Compact directional Receiving antenna and method

TECHNICAL FIELD

The present invention relates to directional antennas, and more specifically to directional antennas that are compact in size relative to their wavelength.

BACKGROUND OF THE INVENTION

Directional antenna systems for receiving electromagnetic radiation have been practiced for many years. A variety of methods have been used to achieve varying degrees of success using terminated traveling wave antennas, phased arrays, parasitic arrays, and true-time delay arrays.

In practice, the antenna designer is often faced with a difficult tradeoff between complexity, gain, directivity, size and bandwidth. For example, for frequencies below 5 MHz, a terminated beverage antenna having a length of multiple wavelengths is known in the art to provide exemplary directivity over a wide bandwidth, but its size makes it difficult to deploy in many settings, especially when multiple antennas are required to achieve desired directional patterns. Rhombic antennas provide exceptional gain for a fixed pattern but also require significant support structure and real estate for effective operation. Curtain arrays provide moderate bandwidth and are moderate in real estate usage and require substantial investment in superstructure. Log Periodic arrays are known for their wide bandwidth and suitable directivity but also require significant investment in superstructure. Parasitic arrays are known for exceptional gain, excellent directivity, and moderate size, but require moderate superstructure and have a very small operational bandwidth.

Loop antennas are known in the art for providing a reliable bi-directional pattern for a relatively small size. It is well known that the signal from a loop antenna can be phased with a closely spaced vertical antenna element to achieve a cardioid pattern over a small bandwidth. In addition, including a properly selected and located resistor in series with a loop can provide a similar cardiod pattern. Other examples in the art include multiple loops in phased arrangement, being spaced apart in end fire relation.

Others have noted the value of utilizing a true-time-delay method of combining signals from two moderately spaced elements. For example, U.S. Pat. No. 3,396,398 issued to J. H. Dunlavy, Jr. teaches a two element true-time-delay antenna using a pair of shortened dipole elements separated by preferably less than 0.3 times the length of the shortest wavelength handled by the system. Such and antenna promises to provide exceptional bandwidth and reasonable directivity. However, the size of such an array is still considerable if, for example, if the shortest wavelength is twenty meters, the length of the dipole elements is six meters with a separation between elements of three meters.

The present invention provides a refreshing option for the antenna designer by providing a compact antenna having structural simplicity, acceptable gain, respectable directivity, fractional size, and exceptional bandwidth. For example, a single loop embodiment having a base length of seven meters provides an operational bandwidth of 0.5-14 MHz. A dual loop embodiment with each loop having individual base lengths of 3.5 meters each, and a separation distance of three centimeters provides an operational bandwidth of 1-22 MHz.

In addition, the nature of the arrangement of the loops and associated structure lends itself to configuring orthogonal arrays that can be electronically switched to provide means to rotate the pattern without physical rotation. These and other advantages the present invention will become apparent from a thorough review of this specification.

SUMMARY OF THE INVENTION

One aspect of the present invention includes a compact directional antenna having a vertical axis and configured to receive electromagnetic signals comprising a first coupler that is configured to transfer signals from an antenna element and located at a first distance from the vertical axis, a first transmission line having a first end connected to the first coupler, and a second end, a second coupler configured to transfer signals from an antenna element and located at a second distance from the vertical axis, a second transmission line having a first end connected to the second coupler, and a second end, a delay line having a first and second end, and wherein the first end is configured to connect in signal transfer relation to the second end of the first transmission line, a signal combiner having a first input port coupled to the second end of the second transmission line, and a second input port coupled to the second end of the delay line, and having an input impedance that is substantially equal to the characteristic impedance of the delay line, and wherein the first distance is equal to the second distance.

Yet another aspect of the present invention is a compact directional antenna comprising a first coupler configured to transfer signals from a loop antenna element, a first transmission line having a first end connected to the first coupler, and a second end, a first and second switch coupled in signal transfer relation to the first transmission line, a second coupler configured to transfer signals from a loop antenna element, a second transmission line having a first end connected to the second coupler, and a second end, a third and fourth switch coupled in signal transfer relation to the second transmission line, a delay line having a characteristic impedance, and a first end and a second end, and wherein the first end is configured to connect in signal transfer relation to the first and third switch; and a signal combiner having a first input port coupled to the second and fourth switch, and a second input port connected to the second end of the delay line, and wherein the signal combiner provides a resultant signal.

Yet another aspect of the present invention includes a method of providing a compact directional antenna that comprises providing first and second symmetrical loop antenna elements, wherein the first and second antenna elements are each positioned about a vertical axis and formed in a first vertical plane, providing first, second, third, and fourth switches, providing a first and second signal bus, providing a delay line, providing a signal combiner having first and second input ports and an output port, transporting signals captured by the first antenna element to the first and second switch, transporting signals captured by the second antenna element to the third and fourth switch, routing signals from the first and third switches to the first signal bus, routing signals from the second and fourth switches to the second signal bus, transporting signals from the first signal bus through the delay line to the first input port of the signal combiner, transporting signals from the second signal bus to the second input port of the signal combiner, and combining signals from the first and second input ports of the combiner to provide a resultant signal at the output port of the signal combiner.

These and other aspects of the present invention will be described in greater detail hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

FIG. 1 is an isometric elevation view of a dual loop embodiment of the compact directional receiving antenna adapted for mounting on a horizontal surface.

FIG. 2 is block diagram of dual loop antenna elements and associated antenna couplers.

FIG. 3 is an isometric elevation view of a single loop embodiment of the compact directional receiving antenna apparatus adapted for mounting on a horizontal surface.

FIG. 4 is a block diagram of a single loop receiving antenna element and associated antenna couplers.

FIG. 5 is a block diagram of the transmission lines and signal processor utilized in various embodiments of the compact directional receiving antenna.

FIG. 6 is an isometric elevation view of a two orthogonal dual loop embodiment of the compact directional receiving antenna adapted for mounting on a horizontal surface.

FIG. 7 is block diagram of a two orthogonal dual loop antenna elements and associated antenna couplers.

FIG. 8 is an isometric elevation view of a two orthogonal single loop embodiment of the compact directional receiving antenna adapted for mounting on a horizontal surface.

FIG. 9 is block diagram of a two orthogonal single loop antenna elements and associated antenna couplers.

FIG. 10 is a block diagram of the transmission lines and signal processor utilized in selected embodiments of the compact directional receiving antenna.

FIG. 11 is an isometric elevation view of a controller utilized in a directional receiving antenna.

FIG. 12 is a collection of horizontal response patterns for a loop antenna element at selected operational frequencies.

FIG. 13 is a collection of horizontal response patterns for a dual loop embodiment of the compact directional receiving antenna at selected operational frequencies.

FIG. 14 is a collection of horizontal response patterns for a dual loop embodiment of the compact directional receiving antenna at selected coupling locations for a given frequency.

FIG. 15 is a collection of horizontal response patterns for a single loop embodiment of the compact directional receiving antenna at selected operational frequencies.

FIG. 16 is a block schematic diagram of a signal coupling, switching, and processing for the compact directional receiving antenna.

FIG. 17 is a perspective view of an alternate coupling arrangement.

FIG. 18 is an elevation view of a combination of two antenna elements, couplers and transmission lines that provides a bi-directional low-elevation response.

FIG. 19 is an elevation view of an antenna array that combines four elements that provides a directional low-elevation response.

FIG. 20 is an elevation view of a single antenna element having two couplers and transmissions connected in a manner to provide an omni-directional low-elevation response.

FIG. 21 is an elevation view an antenna array that combines two single antenna elements each have two couplers connected in a manner to provide a directional low-elevation response.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

Referring now to FIGS. 1 and 2, a dual loop embodiment of a compact directional receiving antenna 10 is illustrated in a fixed installation. The dual loop antenna 10 is shown in a ground mounted configuration, although it could be mounted above the ground without departing from the scope of this invention. The antenna 10 is also illustrated in a stationary configuration, although it can also be built in a mechanically rotatable configuration.

The dual loop antenna 10 includes a controller 12 that is provided to power and configure the dual loop antenna 10, and to transform and deliver captured signals to a receiver (not shown). A feed transmission line 14 connects to the controller 12, providing a conduit for signals captured from the antenna. In addition, the feed transmission line 14 can be utilized for transmitting power and data from the controller 12.

The feed transmission line 14 is connected to a signal processor 16 located near a base of the dual loop antenna 10. The signal processor 16 includes signal combining, time delay, impedance matching, and amplification, circuitry as will be discussed in further detail in this specification.

The dual loop antenna 10 is shown oriented about a vertical axis 19 and includes a vertically oriented center support. In a preferred embodiment, the center support 18 is composed of non-conductive material, although it can be conductive if it is isolated from the ground. Additionally, other means of mechanical support may be employed without departing from the scope of this invention.

A first loop antenna element 20 is shown borne in part by the center support 18 and is comprised of an endless loop of wire that follows a path defining a shape, and having a path length and an enclosed area. In one embodiment, the shape defined by the element 20 is a right triangle with the apex near the top of center support 18. However, the element 20 may have other shapes without departing from the scope of the invention. In addition, the element 20 can be composed of other types of conductors including tubing, pipe, or printed circuit board traces. One end of first loop antenna element 20 is held in tension by an anchor 22.

A coupler 24 is positioned proximate to a portion of the loop antenna element 20 and is configured to transfer signals that are captured by the loop antenna element 20. In one embodiment, the coupler 24 is a current transformer formed by running the loop antenna element 20 directly through a single or multiple ferrite beads 50 (FIG. 2) forming a single turn primary winding of a current transformer. Other types of couplers or transformers that are known in the art, including active couplers, may also be used without departing from the scope of this invention.

A loop transmission line 26 is connected directly to the coupler 24. In one embodiment, the loop transmission line 26 is connected to a connector 54 (FIG. 2) that connects to a single turn secondary winding 52 (FIG. 2) of a current transformer formed by the ferrite bead 50 (FIG. 2). The loop transmission line 26 provides a time delay for signals traveling from one end to the other end.

A second loop antenna element 30 is shown also borne in part by the center support 18 and is comprised of an endless loop of wire. The path length and area enclosed of the loop antenna element 30 should closely approximate the path length and area enclosed of the loop element 20. Additionally, in one embodiment, the shape of the loop antenna element 30 is a mirror image of the shape of loop antenna element 20. The first and second loop antenna elements 20 and 30 respectively should be mounted in a common plane. One end of first loop antenna element 30 is held in tension by an anchor 32.

A coupler 34 is positioned proximate to a portion of the loop antenna element 30 and is configured to transfer signals that are captured by the loop antenna element 30 and should be substantially similar to the coupler 24. In one embodiment, the coupler 34 is a current transformer formed by running the loop antenna element 30 directly through a ferrite bead 60 (FIG. 2) forming a single turn primary winding of a current transformer.

A loop transmission line 36 is connected directly to the coupler 34. In one embodiment, the loop transmission line 36 is connected to a connector 64 (FIG. 2) that connects to a single turn secondary winding 62 (FIG. 2) of a current transformer formed by the ferrite bead 60 (FIG. 2). The loop transmission line 36 provides a time delay for signals traveling from one end to the other end, and in one embodiment provides a time delay that is substantially similar to the time delay provided the loop transmission line 26.

Referring to FIG. 1, a delay line 38 is formed by a transmission line and is shown having both ends connected to the signal processor 16 and operable to produce a time delay. The delay line 38 can be formed using alternative elements as is known in the art including networks of lumped elements such as inductors and capacitors without departing from the scope of this invention. The operation of the delay line 38 will be discussed in further detail later in this specification.

The loop antenna elements 20 and 30 each have a similar loop, base length 42, a coupler to center distance 44, and a loop apex height 46. The loop antenna elements 20 and 30 are separated by a loop spacing distance 45, and have a base height above ground 48. In one embodiment, when the dual loop antenna 10 is designed for an operational frequency range of 1-22 MHz, the loop base length 42 and loop apex height is equal to approximately 3.5 m, the coupler to center distance 44 is 1.75 m, the loop spacing distance 45 is 3 cm, and the base height above ground 48 is 20 cm.

Referring now to FIGS. 3 and 4, a single loop embodiment of a compact directional receiving antenna 70 is illustrated in a fixed installation. The single loop antenna 70 is shown in a ground mounted configuration, although it could be mounted above the ground without departing from the scope of this invention.

The single loop antenna 70 includes the controller 12, feed transmission line 14, signal processor 16, and center support 18 as discussed above.

A single loop antenna element 72 is oriented about the vertical axis 19 and shown borne in part by the center support 18 and is comprised of an endless loop of wire that follows a path defining a shape, and having a path length and an enclosed area. In one embodiment, the shape defined by the element 20 is a triangle. However, the element 72 may have other shapes without departing from the scope of the invention. In addition, the element 72 can be composed of other types of conductors including tubing, pipe, or a printed circuit board trace. Each corner of the single loop antenna element 72 is held in tension by the anchors 22 and 32.

The loop transmission lines 26 and 36 are each connected directly to the couplers 24 and 34. In one embodiment, the loop transmission lines 26 and 36 are connected to a connectors 54 and 640 (FIG. 4) that each in turn connect to separate single turn secondary windings 84 and 88 (FIG. 4) of current transformers formed by the ferrite beads 80 and 82 (FIG. 4). The loop transmission lines 26 and 36 each provide a time delay for signals traveling from one end to the other end.

Referring now to FIG. 3, the delay line 38 has both ends connected to the signal processor 16 introducing a time delay. Signals coming from a reference direction generally indicated by the arrow 40 are preferred when signals from the loop transmission line 26 are routed through the delay line 38 before being combined with signals from loop transmission line 36.

The single loop antenna element 72 has a loop base length 78, a coupler to coupler distance 76, a loop apex height 46, and the base height above ground 48. In one embodiment, when the single loop antenna 10 is designed for an operational frequency range of 500 KHz-14 MHz, the loop base length 78 is equal to 7 m, the loop apex height 46 is equal to approximately 3.5 m, the coupler to coupler distance 76 is 6 m, and the base height above ground 48 is 20 cm.

Referring now to FIG. 5, one end of the loop transmission line 36 is connected to the coupler connector 64. Another end of the loop transmission line 36 is connected to a first port of signal combiner 90. One end of transmission line 26 is connected to the coupler connector 54. Another end of the loop transmission line 26 is connected to a first end of the delay line 38. A second end of the delay line 38 is connected to a second port of the signal combiner 90. Within the signal combiner 90 there exists a first signal path 92 and a second signal path 94. As a practical matter, the first and second signal paths 92 and 94 each introduce signal time delays before signals are combined. Any significant inequality in time delay between the first and second signal paths 92 and 94 must be accounted for by adjusting the length or time delay of the delay line 38 to ensure proper operation. In addition, any inequality in time delay between the first and second signal paths 92 and 94 ideally should be stable over any desired operational frequency range. In one embodiment, the signal combiner 90 is a hybrid coupler having a characteristic impedance that matches the characteristic impedance of the loop transmission lines 26 and 36 as well as the delay line 38. In an alternative embodiment, the signal combiner 90 is a magic Tee combiner.

A combined signal 96 provided by the signal combiner 90 is introduced to a buffer amplifier 98. The buffer amplifier 98 should have an input impedance over any desired operational frequency range that causes an input impedance of the combiner 90 to substantially match the characteristic impedance of the delay line 38.

Referring now to FIGS. 6 and 7, an orthogonal dual loop embodiment of a compact directional receiving antenna 100 is illustrated in a fixed installation and oriented about the vertical axis 19. The orthogonal dual loop antenna 100 is shown in a ground mounted configuration, and includes the controller 12, feed transmission line 14, and vertically oriented center support 18 as discussed previously in this specification. In this embodiment, the controller 12 is configured to electronically orient the antenna pattern as will be discussed later in this specification.

The feed transmission line 14 is connected to a signal processor 102 located near a base of the orthogonal dual loop antenna 100. The signal processor 102 includes switching, signal combining, time delay, impedance matching, and amplification circuitry as will be discussed in further detail in this specification.

The first loop antenna element 20, second loop antenna element 30, a third antenna element 120, and a fourth antenna element 130 are each borne in part by the center support 18 and are each comprised as discussed earlier. Each of the elements 20, 30, 120 and 130 have a path length and an area enclosed which should each be substantially equal to each other. Each of the elements 20, 30, 120 and 130 have a shape, and wherein the shape of element 30 and 130 should substantially mirror the shape of elements 20 and 120. The elements 20 and 30 should be mounted in a common plane and the elements 120 and 130 should be mounted in another plane that is substantially orthogonal to the common plane.

The loop antenna elements 20, 30, 120, and 130 are each held in tension by anchors 22, 32, 122 and 132 respectively.

The couplers 24 and 34 are each positioned proximate to a portion of the loop antenna element 20 and 30, and are each configured-to transfer signals that are captured by the respective elements. Additional couplers 124 and 134 are similarly positioned proximate to a portion of the loop antenna elements 120 and 130, and are each configured to transfer signals that are captured by these respective elements in a manner described previously in this specification.

In one embodiment, the couplers 24, 34, 124 and 134 are each formed by routing each of the elements 20, 30, 120, and 130 through ferrite beads 50, 60, 150 and 160 as shown in FIG. 7. Secondary windings 52, 62, 152, and 152 are each provided to couple signals to connectors 54, 64, 154, and 164 (FIG. 7).

The loop transmission lines 26 and 36 are each connected directly to the couplers 24 and 34. Similarly, a transmission line 126 is connected to coupler 124 and a transmission line 136 is connected to coupler 134. Each of the transmission lines 26, 36, 126, and 136 provide a time delay for signals traveling from one end to the other end, and are selected to provide a substantially similar time delay, one with respect to another.

Referring now to FIG. 6, the delay line 38 is formed as discussed previously in this specification. Another delay line 138 is provided having both ends connected to the signal processor 16 and introduces another time delay. The delay line 138 can also be formed using other elements as is known in the art without departing from the scope of this invention. The operation of the delay line 138 will be discussed in further detail later in this specification.

Signals coming from a reference direction generally indicated by the arrow 40 are preferred when signals from the loop transmission line 26 are routed through the delay line 38 before being combined with signals from loop transmission line 36. Yet further, signals coming from a reference direction generally indicated by the arrow 140 are preferred when signals from the loop transmission line 126 are routed through the delay line 38 before being combined with signals from loop transmission line 136. Still further, signals coming from a reference direction generally indicated by a vector combination of the arrow 40 and 140 are preferred when signals from the loop transmission line 26 are combined with signals from loop transmission line 126, and are routed through the delay line 38 and delay line 138 before being finally combined with signals from a combination of signals from loop transmission line 36 and loop transmission line 136.

The loop antenna elements 20, 30, 120, and 130 each have a similar loop base length 42, a coupler to center distance 44, and a loop apex height 46. The loop antenna elements 20 and 30 are separated by a loop spacing distance 45. The loop antenna elements 120 and 130 are separated by the loop spacing distance 45. All of the loop antenna elements 20, 30, 120, and 130 share the base height above ground 48. In one embodiment, when the orthogonal dual loop antenna 100 is designed for an operational frequency range of 1-22 MHz, the loop base length 42 and loop apex height is equal to approximately 3.5 m, the coupler to center distance 44 is 1.75 m, the loop spacing distance 45 is 3 cm, and the base height above ground 48 is 20 cm.

Referring now to FIGS. 8 and 9, an orthogonal single loop compact directional receiving antenna 170 is illustrated in a fixed installation and oriented about the vertical axis 19. The orthogonal single loop antenna 170 is shown in a ground mounted configuration, and includes the controller 12, feed transmission line 14, and vertically oriented center support 18 as discussed previously in this specification. In this embodiment, the controller 12 is configured to electronically orient the antenna pattern as will be discussed later in this specification.

The feed transmission line 14 is connected to the signal processor 102 located near a base of the orthogonal single loop antenna 170. The signal processor 102 includes switching, signal combining, time delay, impedance matching, and amplification circuitry as will be discussed in further detail in this specification.

The first loop antenna element 72 and a second loop antenna element 172 are each borne by the center support 18 and are each comprised as discussed earlier. Each of the elements 72 and 172 have a path length, shape, and an area enclosed which should each be substantially equal to one another. The element 72 is mounted in a common plane and the element 172 should be mounted in another plane that is substantially orthogonal to the common plane.

The loop antenna elements 72 and 172 are each held in tension by an anchors 22, 32, 122 and 132 respectively.

The couplers 24 and 34 are each positioned proximate to a portion of the loop antenna element 72 are each configured to transfer signals that are captured by the element. The couplers 124 and 134 are similarly positioned proximate to a portion of the loop antenna element 172 are each configured to transfer signals that are captured by this element in a manner described previously in this specification.

The couplers 24 and 34 are positioned proximate to a portion of the loop antenna element 72. In one embodiment, the couplers 24 and 34 are each current transformers formed by running the loop antenna element 72 directly through ferrite beads 80 and 82 (FIG. 9) forming individual single turn primary windings as discussed previously. The couplers 124 and 134 are positioned proximate to a portion of the loop antenna element 172. In one embodiment, the couplers 124 and 134 are each current transformers formed by running the loop antenna element 172 directly through ferrite beads 180 and 182 (FIG. 9) forming individual single turn primary windings as discussed previously.

The loop transmission lines 26 and 36 are each connected directly to the couplers 24 and 34. In one embodiment, the loop transmission lines 26 and 36 are connected to connectors 54 and 64 (FIG. 9) that each in turn connect to separate single turn secondary windings 84 and 88 (FIG. 9) of current transformers formed by the ferrite beads 80 and 82 (FIG. 9). Loop transmission lines 126 and 136 are each connected directly to the couplers 124 and 134 respectively. In one embodiment, the loop transmission lines 126 and 136 are connected to connectors 154 and 164 (FIG. 9) that each, in turn, connect to separate single turn secondary windings 184 and 188 (FIG. 9) of current transformers formed by the ferrite beads 180 and 182 (FIG. 9).

Referring now to FIG. 8, the delay lines 38 and 138 are formed and connected as discussed previously in this specification. The operation of the delay line 138 will be discussed in further detail later in this specification.

The antenna elements 72 and 172 each have the loop base length 78, the coupler to coupler distance 76, the loop apex height 46, and the base height above ground 48. In one embodiment, when the single loop antenna 170 is designed for an operational frequency range of 500 KHz-14 MHz, the loop base length 78 is equal to 7 m, the loop apex height 46 is equal to approximately 3.5 m, the coupler to coupler distance 76 is 6 m, and the base height above ground 48 is 20 cm.

Referring now to FIG. 10, a combiner signal bus 200 is connected to a first port of the signal combiner 90. A delay line signal bus 202 is connected to a first end of the delay line 38. A second end of the delay line 38 is connected to a first end of a parallel combination of the delay line 138 and a bypass switch 203. An opposite end of the parallel combination is connected to a second port of the signal combiner 90.

The combined signal 96 provided by the signal combiner 90 is introduced to the buffer amplifier 98. The resultant signal 99 is provided by the buffer amplifier 98.

A first end of the transmission line 36 is coupled to the connector 64. A controlled connection is provided between a second end of the transmission line 36 and the delay line signal bus 202 via switch 204. A controlled connection is also provided between the second end of the transmission line 36 and the combiner signal bus 202 via switch 206. One skilled in the art would recognize that switches 204 and 206 could be realized using mechanical switches, relays, or PIN diodes.

A first end of the transmission line 26 is coupled to the connector 54. A controlled connection is provided between a second end of the transmission line 26 and the delay line signal bus 202 via switch 208. A controlled connection is provided between the second end of the transmission line 26 and the combiner signal bus 202 via switch 210.

A first end of the transmission line 136 is coupled to the connector 164. A controlled connection is further provided between a second end of the transmission line 136 and the delay line signal bus 202 via switch 212. A controlled connection is also provided between the second end of the transmission line 136 and the combiner signal bus 202 via switch 214.

A first end of the transmission line 126 is coupled to the connector 154. A controlled connection is provided between a second end of the transmission line 126 and the delay line signal bus 202 via switch 216. A controlled connection is provided between the second end of the transmission line 126 and the combiner signal bus 202 via switch 218.

A preferred receive direction can be manipulated for both the orthogonal dual loop antenna 100 (FIG. 6) and the orthogonal single wire loop antenna 170 (FIG. 8) by proper configuration of the switches 203, 204, 206, 208, 210, 21, 214, 216, and 218. This arrangement will be discussed in further detail in the operation portion of this specification.

In one embodiment of the orthogonal dual loop antenna 100 (FIG. 6), the combiner first signal path 92 provides a time delay of 6 nsec relative to the combiner second signal path 94. In this embodiment, delay line 38 is selected to provide a 20 nsec delay and delay line 138 is selected to provide a 6 nsec delay. As a result, a delay of 14 nsec is realized when the bypass switch 203 is closed, and a delay of 20 nsec is realized when the bypass switch 203 is open. Using these values, an acceptable front-to-back ratio has been achieved using the dimensions provided earlier in this specification.

In one embodiment of the orthogonal single loop antenna 170 (FIG. 8), the combiner first signal path 92 provides a time delay of 6 nsec relative to the combiner second signal path 94 as discussed above. In this embodiment, delay line 38 is selected to provide a 27 nsec delay and delay line 138 is selected to provide a 8 nsec delay. As a result, a delay of 21 nsec is realized when the bypass switch 203 is closed, and a delay of 29 nsec is realized when the bypass switch 203 is open. Using these values, an acceptable front-to-back ratio has been achieved using the dimensions provided earlier in this specification.

Referring now to FIG. 11 the controller 12 is housed in an enclosure 230 which supports a selector switch 232. The selector switch 232 is configured to specify a direction by rotating a knob attached thereto. A plurality of light emitting diodes are arranged about the selector switch 230 and are herein referenced as a north LED 234, a northeast LED 236, a east LED 238, a southeast LED 240, a south LED 242, a southwest LED 244, and west LED 246, and a northwest LED 248.

A pattern flip push button switch 250 is mounted on the enclosure 230 and is configured to temporarily change a configuration of the signal processor 102 to electronically rotate a response of the antenna 100 or 170 by one-hundred-eighty degrees.

A unidirectional push button switch 252 is configured to command the signal processor 102 to provide a response of the antenna 100 or 170 that is generally unidirectional. A bidirectional push button 254 is configured to command the signal processor 102 to provide a response of the antenna 100 or 170 that is generally bidirectional.

Referring now to FIG. 12, and using the dimensions described earlier, a series of patterns is provided illustrating relative performance of both the antenna 100 or 170 when they are configured to provide a bidirectional response. The pattern generally indicated by the numeral 300 is modeled at a frequency of 1.5 MHz; the pattern generally indicated by the numeral 302 is modeled at a frequency of 3 MHz; the pattern generally indicated by the numeral 304 is modeled at a frequency of 6 MHz; the pattern generally indicated by the numeral 306 is modeled at a frequency of 12 MHz; and the pattern generally indicated by the numeral 308 is modeled at a frequency of 18 MHz.

Referring now to FIG. 13, and using the dimensions described earlier for the dual loop antenna 10 and orthogonal dual loop antenna 100, a series of patterns is provided when the antenna 100 configured to provide a unidirectional response. The pattern generally indicated by the numeral 310 is modeled at a frequency of 1.5 MHz; the pattern generally indicated by the numeral 312 is modeled at a frequency of 3 MHz; the pattern generally indicated by the numeral 314 is modeled at a frequency of 6 MHz; the pattern generally indicated by the numeral 316 is modeled at a frequency of 12 MHz; and the pattern generally indicated by the numeral 318 is modeled at a frequency of 18 MHz.

Referring now to FIGS. 1, 6, and 14, and using the overall dimensions described earlier for the orthogonal dual loop antenna 100, a relative position of the coupler distance to center 44 to the loop base length 42 impacts the shape of the antenna pattern and will be described briefly below. There is also a relationship between the coupler distance to center 44 and the optimum delay line 38 length. The series of patterns are illustrated for a frequency of 6 MHz, although the pattern shape is largely retained over the operational frequencies. The pattern generally indicated by the numeral 320 is modeled when the coupler distance to center 44 is 90% of the loop base length 42; the pattern generally indicated by the numeral 322 is modeled when the coupler distance to center 44 is 50% of the loop base length 42; the pattern generally indicated by the numeral 324 is modeled when the coupler distance to center 44 is 37% of the loop base length 42; and the pattern generally indicated by the numeral 326 is modeled when the coupler distance to center 44 is 29% of the loop base length 42. By inspection of FIG. 14, it is apparent that forward gain is increased as the coupler distance to center percentage is increased at the expense of front to side ratio.

Referring now to FIG. 15, and using the dimensions described earlier for the single loop antenna 10 and orthogonal single loop antenna 170, a series of patterns is provided when the antenna 170 configured to provide a unidirectional response. The pattern generally indicated by the numeral 330 is modeled at a frequency of 1.5 MHz; the pattern generally indicated by the numeral 332 is modeled at a frequency of 3 MHz; the pattern generally indicated by the numeral 334 is modeled at a frequency of 6 MHz; and the pattern generally indicated by the numeral 336 is modeled at a frequency of 12 MHz.

Referring now to FIG. 16, an alternative coupling method is presented as a signal processing and coupling apparatus 350. Here, a number of elements are shared with FIG. 10 above. The couplers 24, 34, 124, and 134 are each connected to a transmission line 352, 354, 356, and 358 respectively. The transmission lines 352, 354, 356, and 358 are configured to transport signals in differential form. Differential signals presented by the transmission lines 352, 354, 356, and 358 are converted to single ended signals by interacting with transformers 360, 362, 363, and 366 as known in the art. Once converted, the single ended signals are routed to either the combiner bus 200 or delay line signal bus 202 via switches 204, 206, 208, 210, 212, 214, 216, and 218 as described earlier.

Referring now to FIG. 17, an alternative coupler 24 is presented that includes a plurality of ferrite cores 370 and 372 that are connected in an alternate arrangement to provide an impedance transformation. One skilled in the art would recognize that there are many combinations of wiring and turns ratio to provide multiple possible impedance transformation ratios.

Referring to FIG. 18, a bi-directional antenna having a low elevation response is generally designated by the numeral 380. The inventor has recognized that a backside response null elevation angle can be manipulated by strategic selection of the delay line 38 delay time wherein the null elevation angle relative to a horizontal can be increased by decreasing the delay line 38 delay time.

A boundary condition exists at the point where the delay line 38 delay time is decreased to zero providing a null elevation angle substantially equal to ninety degrees. To realize this boundary condition, signals from the loop 20 are introduced to a transmission line 382 by the coupler or transformer 50. Similarly, signals from the loop 30 are introduced to a transmission line 384 by the coupler or transformer 60. The transmission lines 382 and 384 each have a length that is substantially equal. A transmission line 386 connects to the transmission lines 382 and 384 providing a resultant signal.

FIG. 19 illustrates a directional antenna having a low elevation response and is designated as numeral 392. Here, a first bi-directional antenna 380 is connected to a transmission line 392 that routes signals to the signal processor 16 and delay line 38 (not shown). A second bi-directional antenna 380 is connected to a transmission line 394 and is configured to route signals to the signal processor 16. Connecting in this manner, provides a directional antenna with superior front-to-side ratio as well as low elevation response. One skilled in the art would recognize that four bi-directional antennas 380 could be positioned in a radial manner about a center position and combined utilizing the signal processor 102 and delay line 38 as shown in FIGS. 10 and 16.

Referring to FIG. 20, an omni-directional antenna having a low elevation response is generally designated by the numeral 400. Signals from the loop 72 are introduced to the transmission line 382 by the coupler or transformer 80. Similarly, signals from the loop 72 are introduced to the transmission line 384 by the coupler or transformer 82. As state above, the transmission lines 382 and 384 each have a length that is substantially equal. A transmission line 386 connects to the transmission lines 382 and 384 providing a resultant signal.

FIG. 21 illustrates an alternative directional antenna having a low elevation response and is designated as numeral 410. Here, a first omni-directional antenna 400 is connected to the transmission line 392 that routes signals to the signal processor 16 and delay line 38 (not shown). A second omni-directional antenna 400 is connected to the transmission line 394 and is configured to route signals to the signal processor 16. Connecting in this manner, provides a directional antenna with as well as low elevation response. One skilled in the art would recognize that four bi-directional antennas 380 could be positioned in a radial manner about a center position and combined utilizing the signal processor 102 and delay line 38 as shown in FIGS. 10 and 16. In addition, the omni-directional response of antenna 400 lends itself to use in other types of arrays that utilize omni-directional antenna elements. One skilled in the art would readily recognize that the antenna 400 could be utilized in popular four-square array configurations.

Operation

The operation of the present invention is believed to be readily apparent and is briefly summarized in the paragraphs which follow.

Referring to FIGS. 1,2 and 5, an electromagnetic signal arriving from a direction opposite indicated by the arrow 40 will first induce a signal into loop element 20, and then, after an induced arrival time delay, into loop element 30. Each of the loop elements 20 and 30 have a individual response pattern which is represented by the patterns shown in FIG. 12 at selected frequencies as discussed above. The loop coupler 24 will transfer its signal in phased relationship from loop element 20 to the transmission line 26 and the loop coupler 34 will transfer its signal in phased relationship from the loop element 30 to the transmission line 36. Each signal experiences a similar time delay when traveling from one end of the transmission lines 26 and 36 if they each have a similar length, velocity factor, characteristic impedance, and are terminated into a similar impedance.

After traveling through transmission line 26, its signal is routed through the delay line 38 to induce a further delay into the signal received on the loop element 20. The delay line 38 is terminated into one port of the signal combiner 90 where it experiences a further delay through the combiner signal path 94. The transmission line 36 is terminated into another port of the signal combiner 90 where it experiences a further delay through the combiner signal path 92. The combined signal 96 emerges from a third port of the combiner 90 and is routed to the buffer amplifier 98, where it is delivered to the feed transmission line 14 via path 99. The controller 12 conditions the signal provided by the transmission line 14 and makes it available for connection to a receiver (not shown). The controller 12 also provides power for the buffer amplifier 98.

During design of the antenna 10, the phasing of the couplers as well as the time delay induced by each line and signal path is selected such that signals arriving from the direction opposite that indicated by the arrow 40 are of opposite phase so that they effectively cancel, allowing signals arriving from the preferred direction indicated by arrow 40 to experience a lesser degree of cancellation. More specifically, the sum of the delay provided by the transmission line 26 and the delay line 38 and the signal path delay 94 minus the sum of the delay provided by the transmission line 36 and the signal path delay 92 should be approximately equal to the induced arrival time delay. The results of the signal combining process can be observed by a careful inspection of FIGS. 13 and 14 as described previously in this specification.

Referring now to FIGS. 6, 7, 10, 11 and 16, elements of one dual loop antenna 10 (FIG. 1) are oriented in a direction generally indicated by the arrow 40 (which follows signals arriving from a northerly direction), and combined in orthogonal fashion with elements of another dual loop antenna 10 (FIG. 1) and oriented in a direction generally indicated by the arrow 140 (which follows signals arriving from an westerly direction) for form an orthogonal dual loop antenna 100.

The signal processor 102 is configured to be responsive to commands provided by the controller 12 as is well known in the art. When the bidirectional push button 254 is pressed, a pair of oppositely positioned light emitting diodes are lit indicating the commanded direction. When the north LED 234 and south LED 242 are each illuminated, a message is sent to the signal processor 102 to close the combiner switch 206, leaving remaining switches in FIGS. 10 and 16 in an open position. Signals arriving at the antenna 100 are induced into loop element 30, where they are coupled into the transmission line 36 via coupler 34. These signals are routed through the closed combiner switch 206 and travel through the combiner 90 and follow the path discussed previously in this specification. Since all other switches in the signal processor 102 remain open, no other signal is presented to the combiner 90, so the pattern of FIG. 12 is realized with a north-south orientation. In a similar manner, by moving the selector switch 232 so that the east LED 238 and west LED 246 are illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switch 218 leaving remaining switches in FIGS. 10 and 16 in an open position so the pattern of FIG. 12 is realized with a east-west orientation.

By moving the selection switch 232 so that the northeast LED 236 and southwest LED 244 are each illuminated, a message is sent to the signal processor 102 to close the switches 206 and 218, leaving remaining switches in FIGS. 10 and 16 in an open position. Signals arriving at the antenna 100 are induced into loop elements 30 and 120, where they are each coupled into the transmission lines 36 and 126 via couplers 34 and 124. These signals are routed through the closed combiner switches 206 and 218 to the combiner signal bus 200, traveling through the combiner 90 and following the path discussed previously in this specification. Since all other switches in the signal processor 102 remain open, no other signal is presented to the combiner 90, so the pattern of FIG. 12 is realized with a northeast-southwest orientation.

In a similar manner, by moving the selector switch 232 so that the southeast LED 240 and northwest LED 248 are illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switches 210 leaving remaining switches in FIGS. 10 and 16 in an open position so the pattern of FIG. 12 is realized with a southeast-northwest orientation.

Continuing to refer to FIGS. 6, 7, 10, 11, and 16 when the unidirectional push button 252 is pressed, a light emitting diode is lit indicating the commanded direction. When only the north LED 234 is illuminated, a message is sent to the signal processor 102 to close the switches 206, 208 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. The signal arriving at the antenna 100 is induced into loop element 30, where it is coupled into the transmission line 36 via coupler 34. This signal is routed through the closed combiner switch 206 and fed onto the combiner signal bus 200 that is also connected to the combiner 90. The signal is also induced into the loop element 20, where it is coupled into the transmission line 26 via coupler 24. The signal is routed through the closed delay switch 208 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the bypass switch 203 that is also connected to the combiner 90. At the combiner, signals coming from the favored direction are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification. In this way, the antenna patterns shown in FIG. 13 and FIG. 14 are realized with a northerly orientation.

In a similar manner, by moving the selector switch 232 so that the south LED 242 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close the switches 210, 204 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. In this way, the antenna patterns shown in FIG. 13 and FIG. 14 are realized with a southerly orientation.

By rotating the selector switch 232 so that the east LED 238 is illuminated, a message is sent to the signal processor 102 to close the switches 218, 212 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. The signal arriving at the antenna 100 is induced into loop element 120, where it is coupled into the transmission line 126 via coupler 124. This signal is routed through the closed combiner switch 218 and fed onto the combiner signal bus 200 that is also connected to the combiner 90. The signal is also induced into the loop element 130, where it is coupled into the transmission line 136 via coupler 134. The signal is routed through the closed delay switch 212 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the bypass switch 203 that is also connected to the combiner 90. At the combiner, signals coming from the favored direction, in this case from the east, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification. In this way, the antenna patterns shown in FIG. 13 and FIG. 14 are realized with an easterly orientation.

In a similar manner, by rotating the selector switch 232 so that the west LED 246 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close the switches 214, 216 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. In this way, the antenna patterns shown in FIG. 13 and FIG. 14 are realized with a westerly orientation.

Referring still to FIGS. 6, 7, 10, 11, and 16, and by moving the selection switch 232 so that the northeast LED 236 is illuminated, a message is sent to the signal processor 102 to close the combiner switches 206, 218 and delay switches 208 and 212 leaving remaining switches in FIG. 10 in an open position. Signals arriving at the antenna 100 are induced into loop elements 30 and 120, where they are each coupled into the transmission lines 36 and 126 via couplers, 34 and 124. These signals are routed through the closed combiner switches 206 and 218 to the combiner signal bus 200, traveling through the combiner 90 and following the path discussed previously in this specification.

Signals arriving at the, antenna 100 are also induced into loop elements 20 and 130, where they are each coupled into the transmission lines 26 and 136 via couplers 24 and 134. These signals are routed through the closed delay switches 208 and 212 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the delay line 138 that is also connected to the combiner 90. At the combiner, signals coming from the favored direction, in this case from the northeast, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification. In practice, it has been found that the delay line 138 is optional, and can be removed if it is permanently bypassed.

In a similar manner, by moving the selector switch 232 so that the southeast LED 240 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switches 210 and 218 and close delay switches 204 and 212 leaving remaining switches in FIGS. 10 and 16 in an open position. In this configuration signals coming from the favored direction, in this case from the southeast, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification.

Also, in a similar manner, by moving the selector switch 232 so that the southwest 244 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switches 210 and 214 and close delay switches 204 and 216 leaving remaining switches in FIGS. 10 and 16 in an open position. In this configuration signals coming from the favored direction, in this case from the southwest, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification.

Finally, in a similar manner, by moving the selector switch 232 so that the northwest 244 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switches 206 and 214 and close delay switches 208 and 216 leaving remaining switches in FIGS. 10 and 16 in an open position. In this configuration signals coming from the favored direction, in this case from the northwest, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification.

Referring now to FIGS. 3, 4 and 5, an electromagnetic signal arriving from a direction opposite indicated by the arrow 40 will induce a signal into loop element 72. The loop elements 72 each have an individual response pattern that is represented by the patterns shown in FIG. 12 at selected frequencies discussed above.

The signal from the loop element 72 will first transfer the signal to loop coupler 24, and then, after an induced arrival time delay, transfer the signal to loop coupler 34. Accordingly, the loop coupler 24 will transfer its signal in phased relationship to the transmission line 26, and the loop coupler 34 will transfer its signal in phased relationship to the transmission line 36.

After traveling through transmission line 26, its signal is routed through delay line 38 to induce a further delay into the signal received on the loop element 20. The delay line 38 is terminated into one port of the signal combiner 90 where it experiences a further delay through the combiner signal path 94. The transmission line 36 is terminated into another port of the signal combiner 90 where it experiences a further delay through the combiner signal path 92. The combined signal 96 emerges from a third port of the combiner 90 and is routed to the buffer amplifier 98, where it is delivered to the feed transmission line 14 via path 99. The controller 12 conditions the signal provided by the transmission line 14 and makes it available for connection to a receiver (not shown). The controller 12 also provides power for the buffer amplifier 98.

During design of the antenna 10, the phasing of the couplers as well as the time delay induced by each line and signal path is selected such that signals arriving from the direction opposite that indicated by the arrow 40 are of opposite phase so that they effectively cancel, allowing signals arriving from the preferred direction indicated by arrow 40 to experience a lesser degree of cancellation. More specifically, the sum of the delay provided by the transmission line 26 and the delay line 38 and the signal path delay 94 minus the sum of the delay provided by the transmission line 36 and the signal path delay 92 should be approximately equal to the induced arrival time delay. The results of the signal combining process can be observed by a careful inspection of FIG. 15 as described previously in this specification.

Referring now to FIGS. 8, 9, 10, 11, and 16, elements of one single loop antenna 70 (FIG. 3) are oriented in a direction generally indicated by the arrow 40 (which follows signals arriving from a northerly direction), and combined in orthogonal fashion with elements of another single loop antenna 70 (FIG. 3) and oriented in a direction generally indicated by the arrow 140 (which follows signals arriving from an westerly direction) to form an orthogonal single loop antenna 170.

When the bidirectional push button 254 is pressed, a pair of oppositely positioned light emitting diodes are lit indicating the commanded direction. When the north LED 234 and south LED 242 are each illuminated, a message is sent to the signal processor 102 to close the combiner switch 206, leaving remaining switches in FIGS. 10 and 16 in an open position. Signals arriving at the antenna 170 are induced into loop element 72, where they are coupled and routed as described earlier in this specification so the pattern of FIG. 12 is realized with a north-south orientation. In a similar manner, by moving the selector switch 232 so that the east LED 238 and west LED 246 are illuminated, a message is sent from the controller 12 to the signal processor 102 to close combiner switch 218 leaving remaining switches in FIG. 10 in an open position so the pattern of FIG. 12 is realized with a east-west orientation.

By moving the selection switch 232 so that the northeast LED 236 and southwest LED 244 are each illuminated, a message is sent to the signal processor 102 to close the switches 206 and 218, leaving remaining switches in FIGS. 10 and 16 in an open position. Signals arriving at the antenna 170 are induced into loop elements 72 and 172, where they are each coupled into the transmission lines 36 and 126 via couplers 34 and 124. These signals are routed through the closed combiner switches 206 and 218 and process as described previously in this specification, so the pattern of FIG. 12 is realized with a northeast-southwest orientation.

Continuing to refer to FIGS. 8, 9, 10, 11, and 16, when the unidirectional push button 252 is pressed, a light emitting diode is lit indicating the commanded direction as discussed previously in this specification. When only the north LED 234 is illuminated, a message is sent to the signal processor 102 to close the switches 206, 208 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. The signal arriving at the antenna 170 is induced into loop element 72, where it is coupled into the transmission line 36 via coupler 34. This signal is routed through the closed combiner switch 206 and fed onto the combiner signal bus 200 that is also connected to the combiner 90. The signal is also coupled into the transmission line 26 via coupler 24. The signal is routed through the closed delay switch 208 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the bypass switch 203 that is also connected to the combiner 90 and processed as described earlier. In this way, the antenna pattern shown in FIG. 15 is realized with a northerly orientation.

In a similar manner, by moving the selector switch 232 so that the south LED 242 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close the switches 210, 204 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. In this way, the antenna pattern shown in FIG. 15 is realized with a southerly orientation.

By rotating the selector switch 232 so that the east LED 238 is illuminated, a message is sent to the signal processor 102 to close the switches 218, 212 and the bypass switch 203, leaving remaining switches in FIGS. 10 and 16 in an open position. The signal arriving at the antenna 170 is induced into loop element 172, where it is coupled into the transmission line 126 via coupler 124. This signal is routed through the closed combiner switch 218 and fed onto the combiner signal bus 200 that is also connected to the combiner 90. The signal is also induced into the transmission line 136 via coupler 134. The signal is routed through the closed delay switch 212 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the bypass switch 203 that is also connected to the combiner 90. At the combiner, signals coming from the favored direction, in this case from the east, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification. In this way, the antenna pattern shown in FIG. 15 is realized with an easterly orientation.

In a similar manner, by rotating the selector switch 232 so that the west LED 246 is illuminated, a message is sent from the controller 12 to the signal processor 102 to close the switches 214, 216 and the bypass switch 203, leaving remaining switches in FIG. 10 in an open position. In this way, the antenna pattern shown in FIG. 15 is realized with a westerly orientation.

Referring still to FIGS. 8, 9, 10, 11, and 16 and by moving the selection switch 232 so that the northeast LED 236 is illuminated, a message is sent to the signal processor 102 to close the combiner switches 206, 218 and delay switches 208 and 212 leaving remaining switches in FIG. 10 in an open position. Signals arriving at the antenna 170 are induced into loop elements 72 and 172, where they are each coupled into the transmission lines 36 and 126 via couplers 34 and 124. These signals are routed through the closed combiner switches 206 and 218 to the combiner signal bus 200, traveling through the combiner 90 and following the path discussed previously in this specification.

Signals are also each coupled into the transmission lines 26 and 136 via couplers 24 and 134. These signals are routed through the closed delay switches 208 and 212 and fed onto the delay line signal bus 202 that is connected to the delay line 38 that subsequently is connected to the delay line 138 that is also connected to the combiner 90. At the combiner, signals coming from the favored direction, in this case from the northeast, are attenuated less than are signals coming from the un-favored direction as discussed previously in this specification. In practice, it has been found that the delay line 138 is optional, and can be removed if it is permanently bypassed.

In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and describe, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Compact directional Receiving antenna and method

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CPC

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Abstract

Description

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CROSS-REFERENCES TO RELATED APPLICATIONS