Patent Grant
7755553
1. Statement of the Technical Field
The invention relates to the field of communications. More particularly, this invention relates to an antenna assembly for a portable communications device.
2. Background of the Invention
Portable hand-held radio communication devices are often limited with regard to their long range communications capabilities. This limitation is generally attributable to the relatively low effective radiated power (ERP) associated with such radios. The relatively low ERP is due primarily to the relatively low power output of the radio frequency (RF) amplifiers used in such radios, and the poor efficiency of the antennas. For example, many of these handheld radios have conventionally been equipped with a short flexible antenna sometimes referred to as a “rubber duck” antenna or “whip” antenna. These antennas are essentially shortened vertical monopole antennas which have been electrically loaded so as to reduce their overall physical length. While such antennas are convenient, their performance is often limited by their small size and the absence of an effective counterpoise.
U.S. Pat. No. 6,940,462 to Packer (hereinafter “Packer”) discloses a body-worn antenna which overcomes many of the limitations associated with shortened, electrically loaded vertical monopole designs. In particular, Packer teaches a broadband dipole antenna that is removably fastened to a garment of the user. The antenna assembly is coupled to a portable handheld radio which is also carried by the user. The body-worn dipole design of the antenna disclosed by Packer provides higher gain and improved efficiency as compared to conventional vertical monopole designs. These improvements are attributable to the electrically balanced design of the dipole and larger physical size of the antenna.
Still, there remains a continuing need for antenna systems that offer improved performance. In particular, there is a continuing need for antennas that provide higher gain and wider operating bands. These capabilities can enable small portable hand-held radios to provide equal or better range performance compared to larger man-pack radios which are conventionally carried in a ruck-sack.
An antenna assembly to be worn by a user includes a low-band dipole antenna. The low-band dipole antenna is comprised of a low-band dipole feed electrically coupled to a first low-band dipole element extending outwardly from the low-band dipole feed in a first direction. The low-band dipole antenna also includes a second low-band dipole element connected to and extending outwardly from the low-band dipole feed in a second direction opposed from the first direction.
The antenna assembly also includes a high band dipole antenna. The high-band dipole antenna is comprised of a high-band dipole feed interposed at a location along a length of the first low-band dipole element. The high-band dipole feed divides the first low-band dipole element into a first high-band dipole element extending outwardly from the high-band dipole feed in the first direction and a second high-band dipole element extending in the second direction. The high-band dipole feed is electrically coupled to the first and second high-band dipole elements.
Significantly, at least one of the high-band dipole elements is formed as a flexible electrically conductive sleeve. For example the flexible electrically conductive sleeve can comprise a pair of spirally wound, interlocking, electrically conductive elements. The flexible electrically conductive sleeve surrounds a transmission line that extends from the low-band dipole feed to the high-band dipole feed.
An RF control device is provided for selectively directing RF energy in a high-band to the high-band dipole feed, and for selectively directing RF energy in a low-band to the low-band dipole feed. In this regard, it should be understood that the low band comprises an RF range that is lower as compared to an RF range of the high band. For example, the low band can be the VHF band and the high-band is the UHF band. The RF control device is selected from the group consisting of an RF diplexer and an RF switch. If RF control device is an RF switch, it can be controlled by a portable transceiver to which the antenna assembly is connected.
A low-band impedance matching network is provided for the low-band dipole antenna. Similarly, a high-band impedance matching network is provided for the high-band dipole antenna. The low-band dipole feed and the RF control device are advantageously disposed within a dielectric body which physically supports the first and second low-band dipole elements.
The high-band dipole feed further comprises a first impedance transformer electrically coupled to the first and second high-band dipole elements and to the high-band impedance matching network. The first impedance transformer is disposed within a dielectric body which supports the first and second high-band dipole elements. The low-band dipole feed further includes a second impedance transformer electrically coupled to the first and second low-band dipole elements and to the low-band impedance matching network.
A secondary winding of the second impedance transformer is connected to the first and second low-band dipole elements. The secondary winding has a high impedance to electric current at all frequencies in the high-band such that the second low-band dipole element is electrically isolated from the high-band dipole antenna at RF frequencies in the high band. The first impedance transformer forms a low impedance path for coupling electric current from the second high-band dipole element to the first high-band dipole element at RF frequencies in the low band.
The second low-band dipole element is also advantageously constructed as a flexible electrically conductive sleeve. The flexible electrically conductive sleeve surrounds a second RF transmission line that extends from the low-band dipole feed to an RF input port of the antenna at a location disposed along a length of the second low-band dipole element. One or more ferrite bodies are disposed about a portion of the second RF transmission line at a location adjacent to the RF input port.
An alternative embodiment of the antenna assembly also includes a second high-band dipole antenna. The second high-band dipole antenna includes a second high-band dipole feed interposed at a location along a length of the second low-band dipole element. The second high-band dipole feed divides the second low-band dipole element into a third high-band dipole element extending outwardly from the second high-band dipole feed in the first direction and a fourth high-band dipole element extending in the second direction. The second high-band dipole feed is electrically coupled to the third and fourth high-band dipole elements. The flexible electrically conductive sleeve that defines the second low-band dipole element surrounds a third RF transmission line that extends from the low-band dipole feed to the second high-band dipole feed. The RF control device directs RF energy in the high-band to the first and second high-band dipole feed in phase. The second high-band dipole feed can have an impedance transformer which includes a secondary winding. The secondary winding is connected to the third and fourth high-band dipole elements and forms a low impedance path for RF in the low band.
Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which:
Referring now to
The portable communication system 50 can include a portable communication device 125 such as a portable radio that can also be worn on the garment 15 of the user 10. For example, the portable communication device 125 could be a portable radio such as the Harris Corporation Model RF-5800M-HH radio that is a small, lightweight VHF/UHF handheld radio offered by Harris RF Communications Division of Rochester, N.Y. The Model RF-5800M-HH radio operates over a broad frequency range of 30-512 MHz which is commonly used in special operations and platoon-level communications to the squad and individual soldier. However, the invention is not limited in this regard as other portable communication devices could be used as is known to one of ordinary skill in the art.
The portable communication device 125 could be conventionally equipped with a small “rubber duck” or “whip antenna” (not shown) as a primary antenna. However, such antennas are known to be relatively inefficient. In view of the foregoing, the rubber duck or whip antenna can be disconnected from portable communication device 125 and replaced with antenna assembly 100. Coupling antenna assembly 100 to the portable communication device 125 in place of the rubber duck or whip antenna can facilitate longer range communication ability. In addition, the antenna assembly 100 can be worn on the garment 15 of the user 10 to eliminate the problem of having to carry a larger portable communication device 125 in a rear pack with its unwieldy conventional blade antenna. This arrangement also allows the portable communication device 125 to be worn on the front of the garment 15 of the user 10 where it is more convenient to operate.
Referring now to
According to an embodiment of the invention, the second low-band dipole element 110 can be comprised of two sections, namely an upper section 132 and a lower section 134. The upper section 132 and the lower section 134 can be physically connected by a molded section formed of a dielectric material. The upper section 132 and the lower section 134 are formed of a flexible body portion or electrically conductive sleeve. Together, the upper section 132 and the lower section 134 serve as the second low-band dipole element. In this regard, a conductive link 133 can be provided to electrically connect the upper section 132 to the lower section 134. A molded end cap 138 can be provided on an end portion of the lower section 134 to prevent moisture and particle of dirt from entering into the lower section 134. The molded end cap 138 can be formed of a dielectric material or conductive metal.
The first low-band dipole element 105 also includes two sections. These include an upper section 128 and a lower section 130. The upper section 128 and the lower section 130 are physically connected by a molded section 104 which can be formed of a dielectric material. The lower section 130 can be formed of a flexible body portion or electrically conductive sleeve. For example, the electrically conductive sleeve can be of a similar construction to the one that is used to form the second low-band dipole element 110. The upper section 128 of the first low-band dipole element 105 can be formed of a series of progressively longer strip-shaped conductors in a retractable or nested arrangement. Such arrangements are well known by those skilled in the art. Accordingly, the upper section 128 can be folded for storage and transportation, but when released will spring to a fully extended position. Still, the invention is not limited in this regard and any other suitable conductor can also be used to form the upper section 128.
For the VHF range described above, the overall length of the first dipole element 105 may be about thirty inches. Similarly, the overall length of the second dipole element 110 can be about thirty inches. Still, it should be understood that the invention is not limited in this regard. For example, the actual length of the dipole elements can depend on the frequency bands on which the antenna assembly is to be operated.
A high-band dipole feed 102 is disposed within the molded section 104. The molded section 104 can be formed of a dielectric material. The high-band dipole feed 102 is electrically connected to the upper section 128 and the lower section 130 which together comprise the first low-band dipole element 105. Significantly, the upper section 128 and the lower section 130 also respectively comprise a first high-band dipole element and a second high-band dipole element. Hereinafter, for purposes of clarity, upper section 128 may also be referred to as the first high-band dipole element. Similarly, lower section 130 may also be referred to as the second high-band dipole element. For the UHF range, the overall length of the first high-band dipole element can be about 15 inches. The second high-band dipole element can also have a length of about 15 inches for a total high-band dipole length of about 30 inches.
The electrically conductive sleeve which comprises the second low-band dipole element 110 surrounds a transmission line 111. According to one embodiment of the invention, the transmission line 111 can be selected to include a coaxial arrangement of conductors such as is commonly used in coaxial type cable. However, the invention is not limited in this regard. The transmission line 111 can also be coupled to a noise filter that is contained within the molded section 115. The noise filter 204 can be comprised of one or more ferrite toroids 204. The noise filter can be useful for reducing interfering noise delivered from the antenna assembly 100 to the receiver in the portable communications device 125. A connector 115 can be disposed on molded section 108 for coupling to a first connector 121 on one end of the coaxial cable 120. A second connector 122 can be provided on the opposite end of the coaxial cable 120 for coupling to a connector (not shown) on the portable communication device 125. Ferrite sleeves 136 are advantageously provided to reduce noise and unwanted currents which may exist on the shield of the coaxial cable 120.
The electrically conductive sleeve which comprises the high-band dipole's lower element 130 surrounds a second transmission line 113. According to an embodiment of the invention, the second transmission line 113 can be a coaxial arrangement of conductors as is commonly found in coaxial cable. However, the invention is not limited in this regard. The transmission line 113 can be coupled at one end to the RF control device 308 and at a second end to the high-band dipole feed 102. These features will be discussed in more detail below in relation to
Referring now to
Referring once again to
In addition, the invention is not limited to the use of the user-worn antenna fastening device 140 on the clothing or garment 15 of the user 10. In another embodiment of the invention (not shown), the antenna fastening device 140 could be mounted on a surface, such as vehicle panel for mounting the antenna assembly 100 in a vehicle. Still, the invention is not limited in this regard as the antenna fastening device 140 could be used to mount the antenna assembly 100 in any desired location as is known to one of ordinary skill in the art. Other uses for the antenna will also be understood by those skilled in the art. For example, the antenna could be suspended from an object, such as a tree limb in order to increase communications range.
Referring now to
Still referring to
The operation of antenna assembly 100 will now be described. RF energy is communicated to an RF control device 308 through transmission line 111. The RF control device 308 can be disposed within the molded section 106. The RF control device 308 is selectively coupled to either the low-band impedance matching network 304 or the high-band impedance matching network 306. In particular, a low-band type of RF energy having a frequency within a first range can be communicated to the low-band impedance matching network 304. For example, low-band type RF energy can include signals in the VHF frequency range. Similarly, a high-band type of RF energy having a frequency within a second range that is higher than the first range can be communicated to the high-band impedance matching network 306. For example, high-band type RF energy can include signals in the UHF frequency range.
It will be understood by those skilled in the art that the RF control device 308 can take the form of an RF switch or an RF diplexer, without limitation. If the RF control device 308 is an RF switch, it can be advantageously controlled by means of one or more control signals generated by the portable communication device 125. These control signals can be communicated to the RF control device 308 through transmission line 111 or through dedicated control lines (not shown). Various means for communicating antenna control signals using RF transmission lines are well known in the art and therefore will not be described here in detail. However, it should be understood that one such method can include a switched DC control signal and one or more blocking capacitors to isolate the control signal from the antenna elements and sensitive RF circuitry.
The portable communication device 125 can generate the necessary control signal for an RF switch to determine whether RF signals are communicated by the RF control device 308 to either the high-band impedance matching network 306 or the low-band impedance matching network 304. For example if the portable communication device 125 is operated in the VHF band, the control signals can cause the RF control device 308 to route RF signals to the low-band impedance matching network 304. Alternatively, if the portable communication device is operated in a UHF band, the control signals can cause the RF control device 308 to route RF signals to the high-band impedance matching network 306.
According to an alternative embodiment the RF control device 308 can be an RF diplexer. In that case, low-band RF signals can be automatically routed to the low-band impedance matching network by passive circuitry associated with the RF diplexer. Similarly, high-band RF signals can be automatically routed to the high-band impedance matching network 306 using such passive circuitry. RF diplexers are well known in the art and therefore will not be described in detail. However, it should be understood that there are a variety of techniques that can be used for implementing such RF diplexers. Further, it will be understood that a passive RF diplexer can advantageously eliminate the need for antenna control signals. Still, the invention is not limited in this regard and any other suitable means can be used for controlling a flow of RF energy to either the high-band impedance matching network 306 or the low-band impedance matching network 304.
As will be understood from the foregoing discussion, low-band type RF signals will be communicated to the low-band impedance matching network 304. The low-band impedance matching network 304 operates in cooperation with impedance transformer 302 to provide broad band impedance matching. According to one embodiment of the invention, the impedance transformer 302 can step-up the input impedance of the low-band dipole antenna to a relatively higher impedance value. The low-band impedance matching network 304 can then be selected to match the impedance of the transmission line 111 to the relatively higher impedance value provided by the impedance transformer 302. As will be appreciated by those skilled in the art, this arrangement can advantageously minimize the loss of RF power communicated to the low-band dipole antenna 310 which can be otherwise caused by impedance mismatches.
The high-band impedance matching network 306 operates in cooperation with impedance transformer 314 to provide broad band impedance matching between the input transmission line 111 and the high-band dipole antenna 312. According to one embodiment of the invention, the impedance transformer 314 can step-up the input impedance of the high-band dipole antenna 312 to a relatively higher impedance value. The high-band impedance matching network 306 can then be selected to match the impedance of the transmission line 111 to the relatively higher impedance value provided by the impedance transformer 314. As will be appreciated by those skilled in the art, this arrangement can advantageously minimize the loss of RF power communicated to the high-band dipole antenna 312, which losses can be otherwise caused by impedance mismatches. In the arrangement shown in
Still referring to
The foregoing impedances Z314 and Z302 can be provided by selectively choosing the impedance of secondary winding 318, 316 of impedance transformers 314 and 302, transmission line 113 and matching networks 306, 304. The impedance values are selected such that when RF energy in the frequency band of the high-band is fed into the high-band dipole antenna 312, the impedance value that appears at the secondary winding 316 is extremely high. For example, this impedance value is preferably greater than 1000 ohms. This high impedance effectively functions as an open circuit to currents associated with RF energy at frequencies in the high-band (e.g. frequencies in the UHF band). Similarly, the secondary winding 318 of impedance transformer 314 has a relatively low impedance value so that a short circuit is effectively created for currents associated with low-band RF energy (e.g. VHF band). For example, the impedance value can be in the range of 0 to 10 ohms. Consequently, the secondary winding 316 effectively functions as a short circuit at frequencies within the low-band.
Referring now to
In
Referring again to
Referring now to
During low-band operation (e.g. VHF) operation there is no DC applied through the transmission line 111. Accordingly, the RF control device 308 returns to its normal state and RF energy is communicated to the low-band matching network 304. The low-band impedance matching network is comprised of passive components (R1, C3, R2, L2) and the impedance transformer 302. The objective of this circuit is to match the impedance of the low-band dipole antenna 310 so that it provides an acceptable voltage standing wave ratio (VSWR) to the portable communication device. The high band impedance matching network is comprised of transmission line 113 and impedance transformer 314. The values of the various components in
All of the apparatus, and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the invention has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus, methods and sequence of steps of the method without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined.
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|---|---|---|---|
| 4410893 | Griffee | Oct 1983 | A |
| 4940989 | Austin | Jul 1990 | A |
| 5087922 | Tang et al. | Feb 1992 | A |
| 6940462 | Packer | Sep 2005 | B2 |
| 6963313 | Du | Nov 2005 | B2 |
| 6985121 | Bogdans et al. | Jan 2006 | B1 |
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| 7158087 | Dai et al. | Jan 2007 | B2 |
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| Number | Date | Country |
|---|---|---|
| 1 349 235 | Oct 2003 | EP |
| 1 401 051 | Mar 2004 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20090051609 A1 | Feb 2009 | US |
