Antennas are one of the components in a wireless system infrastructure that are used to transfer information between two different points in space. The antenna is a transducer that transforms currents and voltages in circuits into electric and magnetic fields in free space and vice-versa. These electric and magnetic fields propagate in free space; in addition, these fields can be modulated to carry information. Wireless signals carry information that is launched/captured into/from free space by an antenna.
Some examples of UWB (Ultra-Wideband) antennas that are used in the field include a dipole whip or rod, a printed PCB (Printed Circuit Board) wide dipole/monopole, or a ceramic omni-directional UWB antenna. Several different examples are provided.
An example using rectangular elements for the UWB dipole 1-1b is illustrated in
Another antenna type can include a planar reflector (usually formed from an antenna ground) can be designed to form quasi-Yagi antenna structures in PCBs. An example is illustrated in
Although not indicated, the PWB could be a multi-layer board. The additional layers can be patterned into reflector plates to form multiple reflectors for the Multiple Planar Reflector Ultra-Wide Band (UWB) Antenna.
a shows a patterned layout that is used to form a quasi-Yagi antenna 2-1. A PWB 2-2 has a dipole 2-3 and a director 2-4 that is formed on the same top side of the board. The cross-hatch area is the ground plane reflector 2-5 formed on the bottom side of the board. The feed point 2-6 identifies where the transceiver would be connected.
b shows a patterned layout that is used to form a different quasi-Yagi antenna 2-7. A PWB 2-2 has a dipole 2-3 but in this case the director is eliminated. A ground plane formed on the bottom side below the Yagi feedpoint 2-6 that is cross-hatched becomes part of the reflector 2-5. The feed point 2-6 identifies where the transceiver would be connected.
c illustrates a dipole antenna 2-8 on a PWB 2-11. The two metallic rectangular sections 2-9 and 2-10 form the dipole elements.
In
In addition, there is the three-dimensional parabolic reflector antenna. The parabolic surface focuses the reflected incoming energy into a focal point or emits outgoing energy from the focal point to the parabolic surface forming a narrow beam emitted from the antenna. The transceiver is positioned at the focal point to receive or transmit a desired signal. The parabolic antenna is bulky, heavy and costly.
A desirable feature would be to increase the directivity of an antenna without necessarily increasing the cost or weight of the system. A need of building a high-gain directional antenna for the receive and transmit paths of a transceiver is highly desirable. This greatly increases the received/transmitted powers and thus increases the operating range of a low-power wireless system. Another benefit is that the wireless data transmission rate can be improved providing higher signal bandwidths.
This invention relates to the idea of using multiple planar reflectors to build a high-gain directional antenna for the receive/transmit paths to improve the quality of the wireless link. It is important to note that designing a high-gain directional antenna to receive a particularly weak signal, also implies that the antenna will transmit a stronger signal in the high gain direction in the same given frequency range of operation. The maximum EIRP (effective isotropically radiated power) also known as maximum transmitted power is specified by FCC (Federal Communications Commission). The EIRP sets the upper limit of the power radiated in any spatial direction from a UWB system. The maximum UWB power levels allowed by the FCC provide marginal received power levels during the reception of video over short distances. With this transmit EIRP limit, a high-gain antenna is not required for the transmit chain since the power level coupled into the antenna has to be reduced to get the same amount of power radiated into space. The effective power spatial density remains the same. However, it would be desirable to increase the gain of antenna to increase the power of the received signals. On the receive chain, for the same spatial power density presented to the antenna, a high gain antenna couples more power into the receiver IC. Designing a high gain omni-directional antenna is possible but will be very challenging. Meanwhile, for many application scenarios, an omni-directional transmit/receive antenna is not necessary. The other method to get a high gain antenna is to asymmetrically distribute the radiation patterns. An asymmetrically antenna would increase the received power levels for certain directions. Thus, the receiver at these points can receive higher power levels and improve the bit error rate of the USB wireless link.
The design of the asymmetrical antenna is achieved by altering the physical attributes of the system. Some of the physical attributes can be implemented in the PWB, in the regions surrounding the PWB and on the sidewalls of the housing unit. The modification of the physical attributes can be done at very low cost. When the transmit/receive paths shares the same physical antenna, the transmit power would need to be backed off to accommodate a high gain antenna for EIRP limit set by FCC. This brings additional advantage in that a potential transmit power reduction may be possible using the high gain antenna. This greatly increases the operating range of a low-power wireless system, significantly improves the wireless data transmission throughput, and saves power at the transmitter.
An embodiment of the high-gain directional antenna uses a driver plate located within a PWB and at least two reflector plates located on either side of the first plate in the PWB. All three plates are non-intersecting. The reflector plates can be considered to be out-of-plane with the first plane forming the multiple planar reflector antenna structure. The reflector plates can be parallel or non-parallel to the first plate. These reflector plates can be mounted to the sidewalls of the unit and be parallel to each other, can be attached to a foam containing non-conductive low-dielectric constant material that is deposited on the sidewalls, can be positioned on foam to have a wedge shape or be parallel to one another. In some cases, the non-parallel sidewalls can offer an improved performance for this inventive technique. Several embodiments of antennas using several multiple planar reflector plates embodying this inventive aspect to form high-gain directional antennas will be provided.
In another aspect of the invention provides a method of improving the gain of an antenna by using multiple planar reflectors comprising the steps of: pattering a metallic driver plate in a metal layer of a PWB; pattering a first reflector plate in the metal layer of the PWB; isolating the driver plate from the first reflector plate; positioning at least one set of reflector plates where the set comprises an upper reflector plate placed above the metallic driver plate, and a lower reflector plate placed below the metallic driver plate; wherein the driver and all reflector plates can assume any polygon shape, and all plates are isolated from one another.
In another aspect of the invention provides a method that further comprises depositing a layer of non-conductive low-dielectric constant material on the top and bottom planar surfaces of the PWB; whereby the upper and lower reflector plates are placed on the opposing planar surfaces of the material.
In another aspect of the invention provides a method that further comprises supporting the PWB within a product housing unit; attaching the upper and lower reflector plates to the opposing sidewalls; and positioning the PWB between the upper and lower reflector plates.
In another aspect of the invention provides a method that further comprises staggering the placement of the sets of reflector plates along a main beam direction or offsetting the placement of the sets of reflector plates from the main beam direction to improve the gain of an antenna by using multiple planar reflectors.
In another aspect of the invention provides a method adjusting a parameter of a multi planar antenna comprising the steps of: patterning a driver plate in a first metal layer of a PWB; patterning a first reflecting plate in another portion of the first metal layer of the PWB; a means for forming a plurality of sets of reflector plates; and a means for positioning these sets of reflector plates with respect to a main beam direction to adjust a parameter of the antenna.
In another aspect of the invention provides a method that further comprises staggering the sets of reflector plates along the main beam direction; or offsetting the sets of reflector plates from the main beam direction; thereby adjusting the parameter of gain, the beam direction or the angular coverage.
In another aspect of the invention describes a multi planar antenna apparatus that comprising: a metallic driver plate patterned in a metal layer of a PWB; a first reflector plate patterned in the metal layer of the PWB and isolated from the driver plate; at least one set of reflector plates comprising: an upper reflector plate placed above the metallic driver plate; and a lower reflector plate placed below the metallic driver plate; wherein the driver and all reflector plates can assume any polygon shape, and all plates are isolated from one another.
In another aspect of the invention describes a multi planar antenna apparatus that further comprises a non-conductive low-dielectric constant material deposited on both opposing planar surfaces of the PWB; whereby the upper and lower reflector plates are placed on the opposing planar surfaces of the material.
In another aspect of the invention describes a multi planar antenna apparatus that further comprises a product housing unit supporting the PWB; the PWB is placed between opposing sidewalls of the product housing unit; whereby the upper and lower reflector plates are attached to the opposing sidewalls.
The design criteria for the antenna can be segregated from the design criteria of the transceiver. This provides a flexibility of selecting the most cost effective 3rd party design for the transceiver since the transceiver can be a plug and play unit. Of course, the transceiver can be formed using discrete components on a PCB, packaged in an integrated circuit chip that was fabricated in a high tech facility and connected to the PCB, or any other combination of packaging and mounting techniques that can be used to build the components of a wireless system infrastructure known in the art.
All reflector and driver plates are shaped as polygons. A polygon is a shape defined as a plane figure that is bounded by a closed line path. Thus a triangle, a square, a rectangle or an octagon can be considered a polygon. In some case, one or more sides of the polygon may be substituted with a curved line, in any case, this shape with at least one curved line will still be called a polygon. The polygons can have a finite thickness. For example, polygons stamped out of metal plates would have the thickness of the metal plate.
A set of reflector plates is formed when a first and a second reflector plate are either symmetrically or asymmetrically placed about a center plane forming a set of out-of-plane reflector plates or simply a set of reflector plates. This invention proposes to use several discrete metal surfaces that are placed in a given relationship with respect to the axis of main radiation beam to improve the gain of the antenna. Compared with a three dimension scheme for traditional reflector-based antennas, this invention reduces manufacturing/assembly complexity and cost significantly, while demonstrating similar antenna gain by optimizing the shapes, dimensions, and positions of these discrete partial reflectors that are claimed in this invention.
Please note that the drawings shown in this specification may not be drawn to scale and the relative dimensions of various elements in the diagrams are depicted schematically and not to scale.
a shows an oval UWB dipole antenna.
b shows a rectangular UWB dipole antenna.
c shows a triangular UWB dipole antenna.
a illustrates a PWB artwork illustrating the various components of a quasi-Yagi antenna using a director.
b illustrates a PWB artwork illustrating the various components of a quasi-Yagi antenna without a director.
c illustrates a PWB artwork illustrating the various components of a UWB dipole antenna.
d illustrates a 3D artwork illustrating the ultra-wideband antenna.
a depicts a cross-view 3-D perspective of a high gain multiple planar reflector antenna structure in accordance with the present invention.
b depicts a cross-view 3-D perspective of a high gain asymmetrical multiple planar reflector antenna structure in accordance with the present invention.
c depicts a cross-view 3-D perspective of a high gain multiple planar reflector antenna structure with two sets of reflector plates in accordance with the present invention.
a presents a top view perspective of
b presents a top view perspective of
c depicts the top view perspective of
a shows an omni-directional radiation pattern for a traditional UWB antenna.
b illustrates the radiation patterns of the high gain multiple planar reflector UWB antenna structure in accordance with the present invention.
a shows a product housing unit that supports and contains the PWB.
b illustrates the addition of the out-of-plane reflector plates to the inside sidewalls of the product housing unit in accordance with the present invention.
a depicts a PWB.
b depicts a PWB with a portion of the front and back surfaces covered with a foam that cures into a non-conductive low-dielectric constant material.
c illustrates the addition of the out-of-plane reflector plates to the foam in accordance with the present invention.
d depicts a PWB front and back surfaces covered with a foam that cures into a non-conductive low-dielectric constant material.
e illustrates the addition of the out-of-plane reflector plates inside the foam in accordance with the present invention.
f illustrates the addition of the out-of-plane reflector plates to the outside of the foam in accordance with the present invention.
a depicts a side view 8-1 of the driver and reflector plates of
b shows a side view 8-2 of the offset between sets of reflector plates of
c illustrates a side view 8-5 of the staggering between two sets of reflector plates of
a presents a top view perspective of a high gain multiple planar reflector antenna structure with an in-plane top and bottom plate in accordance with the present invention.
b depicts a side view of the driver, reflector, top and bottom plates of
a illustrates a side perspective for one embodiment of an antenna 3-1 that uses reflectors both in and out-of-plane. A Cartesian coordinate axis 3-6 is provided. The transceiver (not shown) would be coupled to a driver plate 3-2. The remaining in-plane element is a reflector plate 3-3. These two elements are in the xz plane with y=0. In addition, the main beam direction 3-7 is depicted and indicated the direction of increased power intensity. A first out-of-plane reflector plate 3-4 is located in the negative y region or below the xz plane. The second out-of-plane reflector plate 3-5 is located in the positive y region or above the xz plane. The in-plane reflector plate 3-3 and the driver plate 3-2 are isolated from each other; that is, the electrical impedance between these two conductor plates are Mega Ω's or higher. This isolation can occur when the metal layer used to form the reflector and driver plates is partitioned into at least two separate metallic segments isolated by the dielectric forming the PWB. The view from the top 4-1 will be shown in
b depicts a side perspective for another embodiment of an antenna 3-8 that uses reflectors both in and out-of-plane. A first out-of-plane reflector plate 34 is located in the negative y region or below the xz plane. The second out-of-plane reflector plate 3-5 is located in the positive y region or above the xz plane. This structure is almost identical to the structure in
c shows a side perspective for one embodiment of an antenna 3-10 that uses two sets of reflectors. The first set of reflector plates 3-5 and 3-4 are in the same position as in
a presents the top view perspective 4-1 of
b illustrates the top view perspective 4-5 of
Sometimes it is not possible to get equal separation between the two out-of-plane reflector plates and the driver plate. Asymmetric reflector placement offers the ability to compensate for the lack of equal separation. Asymmmetry reflector placement can be used to steer the beam away or toward the plane containing the driver plate (the in-plane). Thus, asymmetry reflector placement has two uses: 1) to steer the beam away from the in-plane intentionally when there is equal separation; and 2) steer beam back to the in-plane when equal separation is not possible due to a mechanical limitation. Asymmetric reflector placement is one tool that offers flexibility in beam steering.
c illustrates the top view perspective 4-8 of
a shows the radiation pattern 5-1 of a traditional omni-directional pattern for a UWB antenna. The Cartesian coordinate axis 3-6 that was provided in
a depicts an outside view 6-1 of the product housing unit 6-2. The housing unit has six sides where the sides 6-4 and 6-5 are opposing sidewalls. The PWB 6-3 is placed approximately between the two opposing sidewalls 6-4 and 6-5 where the PWB and the two opposing sidewalls in this case are parallel to one another as shown in
b illustrates an embodiment where the antenna structure 6-6 uses the PCB board ground as the center partial reflector and a set of two metal plates 6-7 and 6-8 as additional reflector plates that are attached to the inside of the sidewalls of the product housing as depicted in
a depicts a PWB 7-1. A ground plane 7-2 is illustrated in
Foams that contain other non-conductive low-dielectric constant materials 7-4 and 7-5 can be applied to the entire top and bottom sides 7-12 and 7-13 of the PWB 7-1 forming the structure 7-11 as illustrated in
Partial reflector plates 7-18 and 7-19 can be placed on the cured foam or material as indicated in the structure 7-17 in
a illustrates a view 8-1 in
b shows a view 8-2 where offsets have been applied to the first and additional sets of reflector plates. The offset of the first set of reflector plates 3-5 and 3-4 is indicated as the offset distance 8-3. The additional set of reflector plates 3-9 and 3-10 are offset in the negative direction 8-4. The offset can be measured with respect to a point on the ground plane of the PWB.
c illustrates a view 8-5 where staggering have been applied to the first and additional sets of reflector plates. The staggering of the first set of reflector plates 3-5 and 3-4 is indicated as the stagger distance 8-6. The additional set of reflector plates 3-9 and 3-10 are staggered in the by the same stagger distance 8-6. The stagger distance is measured with respect to one of the corners of the ground plane of the PWB.
The mechanism of introducing offset or staggering between multiple reflectors along the main beam direction to further improve gain. The mechanism of varying spacing and offset of multiple reflectors also adjusts and steers the beam direction and the angular coverage. In addition, the out-of-plane metal plates can be used to focus the elevation of the beam. The physical dimensions and positions of the plates in the antenna can be designed to adjust one or more parameters of the antenna. Some of these parameters that can be adjusted include the gain, the beam direction or the angular coverage. The proper selection of the dimensions and positions of the plates can be used to achieve optimum performance. The reflector is longer than the driver antenna, this helps collect some EM energy scattered into the direction of the top and bottom edge of the reflector and re-focus it back to the main beam direction; secondly, metal reflectors can be placed on the top and bottom of the driver antenna to further reflect energy back to the main beam.
a illustrates a side perspective for one embodiment of an antenna 9-1 that uses reflectors both in and out-of-plane. A Cartesian coordinate axis 3-6 is provided. The transceiver (not shown) would be coupled to a driver plate 3-2. The remaining elements are an in-plane reflector plate 3-3 and the two additional top and bottom reflector plates 9-2 and 9-3. These four elements are in the xz plane with y=0. A first out-of-plane reflector plate 3-4 is located in the negative y region or below the xz plane. The second out-of-plane reflector plate 3-5 is located in the positive y region or above the xz plane. The in-plane reflector plate 3-3, the driver plate 3-2, the two reflector plates 9-2 and 9-3 are all isolated from each other; that is, the electrical impedance between all four conductor plates are Mega Ω's or higher. This isolation can occur when the metal layer used to form the reflector and driver plates is partitioned into at least four separate metallic segments isolated by the dielectric forming the PWB.
b illustrates a view 9-4 in
Finally, it is understood that the above description are only illustrative of the principle of the current invention. It is understood that the various embodiments of the invention, although different, are not mutually exclusive. In accordance with these principles, those skilled in the art may devise numerous modifications without departing from the spirit and scope of the invention. For example, the techniques of the invention can be practiced in the wireless arena which can include the security, entertainment, business, and gaming industries. It can also be practiced in different wireless standards such as WiMedia MB-OFDM; 802.11a/b/g/n; 802.16 WiMAX; 802.15 WPAN, etc.