Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1997-04-21
2001-02-13
Tsang, Fan (Department: 2746)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S090300, C455S129000, C455S280000, C343S702000, C343S906000
Reexamination Certificate
active
06188918
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to portable communications equipment that utilizes retractable or fixed antennas. More particularly the present invention relates to a transceiver device compatible with both high impedance and low impedance connections without having a matching circuit or switching means included within the device.
PROBLEMS IN THE ART
Many devices such as cellular telephones use a retractable {fraction (1/2+L )} wave antenna. This antenna has a high impedance and requires the use of a matching circuit when connected to the transmitter to provide the maximum energy transfer to the antenna. In some prior art devices, the manufacturers add additional space to the device which is required in order to fit in a matching circuit section that may be external to the main circuit board. Also, when the output power from the transmitter or the receiver sensitivity is checked by connecting the device to testing equipment, the high impedance matching circuit presents a problem. The impedance of most testing equipment is either 50 or 75 ohms and not the high impedance required by the matching circuit (typically 600-2,000 ohms). If the transceiver performance is measured with this impedance mismatch, significant errors in the measurement will result. Many prior art devices overcome these errors by attaching an additional connector, typically coaxial, to a 50 ohm point on the transceiver circuit to provide a test point with accurate information. This solution requires additional coaxial line, a separate connector, and an electrical or mechanical switch to ensure the proper energy transfer from the printed circuit board to the chosen connection. These solutions are not desirable because of the increase in cost and circuit complexity.
Prior art devices using retractable antennas incorporate an internal matching circuit which connects to the antenna assembly to provide the performance of a {fraction (1/2+L )} wave antenna in the extended position. The problem with this feature is that the antenna is matched to the impedance of the transceiver only in the extended position and not in the retracted position. This creates an impedance mismatch that reduces the efficiency of the antenna when it is in the retracted position.
OBJECTS OF THE INVENTION
A general object of the present invention is to provide a retractable {fraction (1/2+L )} wave antenna with an integral matching section.
A further object of the present invention is to provide a transceiver having a low impedance connector for attachment to service equipment and external antennas.
A further object of the present invention is to provide a transceiver having a connector that provides an integral impedance match for high efficiency end-fed {fraction (1/2+L )} wave antennas.
A further object of the present invention is to provide a transceiver having an antenna connector that requires no electrical or mechanical switching inside the transceiver to select the proper impedance as antennas or equipment are interchanged.
A further object of the present invention is to provide a transceiver having an antenna connector that allows for the use of fixed replacement antennas (including {fraction (1/2+L )} wave and {fraction (1/4+L )} wave) without compromising perfor#:ance because of an impedance mismatch.
A further object of the present invention is to provide a transceiver having an end-fed {fraction (1/2+L )} wave antenna that incorporates an integral matching section for proper match when extended.
A further object of the present invention is to provide an antenna that bypasses the integral {fraction (1/2+L )} wave matching section for operation as a {fraction (1/4+L )} wave antenna when retracted.
These as well as other objects of the present invention will become apparent from the following specification and claims.
SUMMARY OF THE INVENTION
A radio transceiver of the present invention includes a transmission line within a housing. The transmission line is comprised of a hollow center conductor and an outer conductor, both connected to a transceiver circuit. The transmission line is also connected to a low impedance connector which is coupled to the housing.
The present invention also includes a retractable antenna which can be coupled to the low impedance connector. The retractable antenna has an extended position and a retracted position. In the extended position, a contact on the antenna makes electrical contact with the center conductor of the transmission line. The contact is connected to an impedance matching circuit within the antenna which matches the antenna with its low impedance connection. In this extended position the antenna acts as an {fraction (1/2+L )} wave antenna.
REFERENCES:
patent: 5245350 (1993-09-01), Sroka
patent: 5353036 (1994-10-01), Baldry
patent: 5521605 (1996-05-01), Koike
Centurion International, Inc.
Sobutka Philip J.
Thomte Dennis L.
Tsang Fan
Zarley McKee Thomte Voorhees & Sease
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