Communications: radio wave antennas – Antennas – Fractional – multiple – or full wave length linear type
Reexamination Certificate
1997-04-18
2001-03-13
Pham, Chi H. (Department: 2731)
Communications: radio wave antennas
Antennas
Fractional, multiple, or full wave length linear type
C343S853000, C343S872000, C343S870000, C343S723000, C343S751000, C343S827000
Reexamination Certificate
active
06201511
ABSTRACT:
BACKGROUND OF THE INVENTION
In a full-duplex radio with a fixed frequency offset, a duplexer is typically required to enable full duplex operation. Conventional duplexers, however, are normally made of ceramic filters, which are bulky and provide only a limited amount of isolation. As the size of communication terminals is getting smaller, the size and significant cost of the conventional duplexer is a concern that must be addressed.
FIG. 1
depicts the operation of a duplexer, which provides a minimum amount of insertion loss in the desired pass band, a sufficient amount of isolation between the Tx and Rx signals, and a sufficient amount of attenuation outside the desired frequency band. The illustrated configuration requires only one antenna for both transmitting and receiving. The use of a single antenna, however, has certain drawbacks. In particular, the antenna must be broadband, covering both Tx and Rx frequencies. As a result, the antenna has low antenna gain with poor VSWR (voltage standing wave ratio) performance. In addition, the single antenna requires the duplexer, which as noted above is space consuming and expensive.
SUMMARY OF THE INVENTION
It is an object of the invention to provide for duplex operation without requiring the conventional duplexer structure. By using separate antennas, one for transmitting and one for receiving, the antennas can be narrowband, which will provide a relatively higher gain and better match to the transceiving circuitry. In addition, with proper arrangement, the composite antenna will also provide full duplex operation without a duplexer. Consequently, space and cost issues associated with the conventional duplexer arrangement are overcome. Moreover, since the bandwidth per antenna (Tx or Rx) is narrower, it will be easier to make dual band antennas, which in fact may eliminate two duplexers from the dual band communications terminal.
In an exemplary embodiment according to the present invention, there is provided an antenna unit for a communications apparatus. The antenna unit includes a transmitting antenna, a receiving antenna, and an isolation circuit disposed coupled with the transmitting antenna and the receiving antenna. The isolation circuit isolates a transmit antenna signal from the receiving antenna. The antenna unit may further include a directional coupler disposed coupling the transmitting antenna and the receiving antenna to the isolation circuit. The coupler couples signal energy off of the transmitting antenna and feeds the energy to the isolation circuit. The isolation circuit may be provided with phase adjusting structure receiving the energy from the coupler. The phase adjusting structure serves to adjust a phase of the signal. The isolation circuit may further be provided with amplitude adjusting structure coupled with the phase adjusting structure. In this context, the amplitude adjusting structure serves to adjust an amplitude of the signal.
In one arrangement, the transmitting antenna and the receiving antenna are disposed substantially co-linear in a single casing. In another arrangement, one of the transmitting antenna and the receiving antenna is disposed in a casing and the other of the transmitting antenna and the receiving antenna is attachable to an apparatus housing.
In accordance with another aspect of the invention, there is provided a method of emitting and receiving a signal with a communications device. The method includes the step of isolating with the isolation circuit a transmit antenna signal from the receiving antenna without a duplexer. The method may further include the steps of coupling signal energy off of the transmitting antenna and feeding the energy to the isolation circuit. The method may still further include the step of adjusting with the isolation circuit a phase of the signal, and adjusting with the isolation circuit an amplitude of the signal.
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patent: 4952193 (1990-08-01), Talwar
patent: 4991165 (1991-02-01), Cronyn
patent: 5227784 (1993-07-01), Masamori et al.
patent: 5315096 (1994-05-01), Muller et al.
patent: 5321409 (1994-06-01), Walker
patent: 5581268 (1996-12-01), Hirshfield
patent: 5589843 (1996-12-01), Meredith et al.
patent: 0 767 508 (1997-04-01), None
patent: 2 270 444 (1994-03-01), None
patent: 2270444 (1994-09-01), None
John Almeida, “The ARRL Antenna Book” pp. 17-1 thur 17-7 Published by The American Radio Relay League 1988.
Ericsson Inc.
Nixon & Vanderhye P.C.
Pham Brenda H.
Pham Chi H.
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