Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-01-14
2002-03-26
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
Reexamination Certificate
active
06362787
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed generally to the field of antennas for communication systems, and more particularly to a novel active antenna system using patch/microstrip antenna elements, and more particularly still, to a novel lightning, corona, and low frequency static energy protection scheme for such an antenna system.
BACKGROUND OF THE INVENTION
In base stations for most Cellular/PCS systems, where the antennas and cable are completely passive, lightning near strikes (or other corona discharges or high energy static) cause reliability concerns, since the antenna acts as a “sponge” to the lightning (or corona/static discharge) energy, and channels the high voltage to the sensitive electronics. Of course, in the case of direct strikes, the antenna system is typically vaporized. However, for near strikes, where the local area around the antenna is saturated with high voltage field energy, protection of the base station electronics from this energy is warranted. These systems often employ “lightning arrestor” systems, often simply high voltage-capable capacitors (high pass filters), that suppress the low frequency and DC (direct current) energy associated with the lightning. These arrestors are often simply attached in series with the cable to the antenna, near the antenna and/or near the base of tower (as shown in FIG.
1
), via connectors, to the RF cable.
Additionally, even the presence of simple static build-up (DC energy), on the surface of the antenna elements, can achieve significant voltage to severely damage active components, not protected by the conventional lightning arrestor described above, i.e., a high voltage capacitor in series with the cable.
The above-referenced prior applications discloses a novel active amplifier system in which patch or microstrip type antenna elements are arranged in antenna arrays with each antenna element being provided with a low power amplifier chip closely adjacent the antenna element, or at least within the same housing or on the same circuit board as the antenna element.
For such “active” antenna systems, which employ active electronics (amplifiers, transistors, phase shifters, . . . ) within the antenna structure, the use of the above-described conventional lightning arrestors will not protect the electronics. Such protection would require an arrestor system or device within the antenna itself, to arrest the low frequency and DC energy before it reaches any electronics. This proves difficult, since conventional arrestor devices are typically large (an inch or more in diameter) and costly. Additionally, the use of an arrestor of this type can adversely impact the performance of the electronics, since the capacitive properties of the arrestor adversely affects the circuit impedance.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is described herein in connection with an aperture coupled microstrip patch antenna used in a base station sector antenna with active electronics; however, the invention is not so limited, but may be used in connection with patch antenna elements in other applications. Typically, the radiating microstrip patch is located on a dielectric superstrate and the DC voltage of the (metal) patch is floating with respect to zero potential or ground. If a static charge develops on the (metal) patch and discharges through the aperture to the microstrip feeder line, damage to, or failure of, the active electronics connected to the microstrip feeder line is possible. Since the antenna is operating with a single polarization, e.g., vertical polarization, any DC connection to the patch in the opposite polarization, e.g., horizontal polarization, does not affect the desired radiation pattern.
Therefore, to prevent static charge build up, the invention provides a narrow, high impedance conductive trace attached to the radiating patch in the orthogonal polarization (i.e., orthogonal to the patch polarization). These conductive traces are tied together with a vertical conductive trace along the axis of the array, which at a convenient location, is tied to an electrical ground.
In one embodiment, this grounding system of conductive traces is placed on the superstrate, so that the conductive traces do not disturb the base station's radiation pattern or VSWR (voltage standing wave ratio). For the case of vertical polarization of the antenna elements, if the vertical traces which tie together the individual narrow static (horizontal) drain lines are too close to the radiating patch(es), the radiating pattern and VSWR can degrade. Therefore, the vertical trace is separated from the radiating patch. In one example of the invention, the vertical trace is roughly 0.45 &lgr;o (0.45 of a free space wavelength) away from the edge of the radiating patch.
If only one (vertical) trace is used to connect to the (horizontal) lines from the patch, generation of some undesirable asymmetry in the azimuth radiation pattern is possible. By designing a system of traces with symmetry about the center of the radiating patch, in one embodiment of the invention, mechanical symmetry is maintained, and accordingly, the azimuth radiation pattern remains symmetrical.
In an alternate embodiment of the invention, it is an objective to overlay the grounding system of conductive traces on the superstrate so that the conductive traces interact with the radiating patch to produce desirable effects in overall (azimuth) radiation pattern. Some of the desirable effects to the (azimuth) radiation pattern are: (a) to suppress backward radiation, and, (b) shaping of the pattern within the sector coverage, i.e., tailoring the pattern to roll off quicker past the sector edge.
Briefly, in accordance with the foregoing, an active antenna system having lightning, corona and low frequency static energy protection, comprises a plurality of patch antenna elements, a feed structure operatively interconnecting said plurality of patch antenna elements, and at least one conductive drain line coupled with each of said patch antenna elements, said drain lines being coupled together at a common ground connection point.
REFERENCES:
patent: 4124852 (1978-11-01), Steudel
patent: 4360813 (1982-11-01), Fitzsimmons
patent: 4566013 (1986-01-01), Steinberg et al.
patent: 4689631 (1987-08-01), Gans et al.
patent: 4825172 (1989-04-01), Thompson
patent: 4849763 (1989-07-01), DuFort
patent: 4890110 (1989-12-01), Kuwahara
patent: 5034752 (1991-07-01), Pourailly et al.
patent: 5061939 (1991-10-01), Nakase
patent: 5230080 (1993-07-01), Fabre et al.
patent: 5248980 (1993-09-01), Raguenet
patent: 5280297 (1994-01-01), Profera, Jr.
patent: 5327150 (1994-07-01), Cherrette
patent: 5379455 (1995-01-01), Koschek
patent: 5412414 (1995-05-01), Ast et al.
patent: 5513176 (1996-04-01), Dean et al.
patent: 5548813 (1996-08-01), Charas et al.
patent: 5596329 (1997-01-01), Searle et al.
patent: 5604462 (1997-02-01), Gans et al.
patent: 5619210 (1997-04-01), Dent
patent: 5621422 (1997-04-01), Wang
patent: 5644622 (1997-07-01), Russell et al.
patent: 5646631 (1997-07-01), Arntz
patent: 5659322 (1997-08-01), Caille
patent: 5710804 (1998-01-01), Bhame et al.
patent: 5714957 (1998-02-01), Searle et al.
patent: 5724666 (1998-03-01), Dent
patent: 5751250 (1998-05-01), Arntz
patent: 5770970 (1998-06-01), Ikeda
patent: 5802173 (1998-09-01), Hamilton-Piercy et al.
patent: 5809395 (1998-09-01), Hamilton-Piercy et al.
patent: 5832389 (1998-11-01), Dent
patent: 5854611 (1998-12-01), Gans et al.
patent: 5862459 (1999-01-01), Charas
patent: 5987335 (1999-11-01), Knoedl, Jr. et al.
patent: 6008763 (1999-12-01), Nystrom et al.
patent: 6043790 (2000-03-01), Derneryd et al.
patent: 6072434 (2000-06-01), Papatheodorou
patent: 6091360 (2000-07-01), Reits
patent: 6104935 (2000-08-01), Smith et al.
patent: 6140976 (2000-10-01), Locke et al.
patent: WO 95/34102 (1995-12-01), None
patent: WO 98/09372 (1998-03-01), None
patent: WO 98/11626 (1998-03-01), None
patent: WO 98/50981 (1998-11-01), None
Judd Mano D.
Monte Thomas D.
Andrew Corporation
Clinger James
Wong Don
Wood Herron & Evans L.L.P.
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