Full duplex/half duplex power radio

FULL DUPLEX / HALF DUPLEX POWER RADIO

0002Technical Field

0003This invention relates generally to the field of duplex radios, and more specifically to duplex radios with RF switching devices allowing for both full duplex mode and half-duplex or "talkaround" mode.

0004Background

0005Radios use duplexer schemes to allow the transmitter and receiver to share the same antenna. Furthermore, switching schemes are used to prevent the transmitter and receiver from further interfering with each other when required. The arrangement should allow transfer of transmitter power to the antenna, and allow the received signal at the antenna to reach the receiver with minimal attenuation. The switching scheme would facilitate the switching of modes from full duplex to half duplex and visa-versa. But with conventional switching schemes, problems still arise from interference and spurious signals. Therefore, a need exists for a method of using RF power stages that delivers sufficient ^ er in a full duplex and a "talkaround" or half-duplex mode and further provides improved performance substantially free from interference and spurious signals. Summary of the Invention

0006Briefly, according to the invention, a radio having full- duplex and half-duplex capability, provides for a power amplifier having an output port, a receiver having an input port, and a duplexer having an antenna port, a transmitter port, and a receiver port. The present invention further comprises a switching means coupled to the power amplifier output port and the receiver input port for selectively either simultaneously coupling the power amplifier output port to the duplexer transmitter port and the receiver input port to the duplexer receiver port for duplex operation, or alternately coupling the amplifier output port to the duplexer receiver port for half-duplex operation.

0007Brief Description of the Drawings Figure 1 is a partial schematic diagram of a Full Duplex /

0008Half Duplex radio in accordance with the present invention.

0009Figure 2 is a partial schematic diagram of an alternative embodiment of the present invention.

0010Detailed Description of the Preferred Embodiment

0011Referring to Figure 1 , there is shown Full Duplex / Half Duplex (FD/HD) radio 10 in accordance with the present invention. Radio 10 includes a power amplifier 12 preferably comprising an exciter 14, a driver 16, and a final power amplifier

001218. Radio 10 further includes a receiver 20 having an input port

001319. During full duplex operation, the receiver 20 and power amplifier 12 are coupled to a receiver filter 34 ( preferably having a pass band in the 851-870 MHz range or the 935-941 Mhz range) and a transmitter filter 32 (preferably having a passband in the 806-825 MHz range or the 896-902 Mhz Range) respectively. The transmitter filter 32 and the receiver filter 34 are preferably monolithic ceramic block comb-line bandpass filters.

0014During half-duplex operation, the receiver 20 is uncoupled from the receiver filter. Furthermore, the power amplifier 12 couples to the receiver filter 34 and transmits power through the receiver filter.

0015The radio 10 interchangeably switches from full duplex to half-duplex using a switching means 22 which can preferably comprise at least two PIN diode switches represented by the switches 24 and 26. Typically, a controller 30 sends at least one control signal to the switching means 22 to direct the mode of operation of the radio 10.

0016In full-duplex operation, the radio 10 is required to talk and listen simultaneously. Therefore, the switch 24 couples the power amplifier stage 12 to the transmitter filter 32 and switch 26 couples the receiver 20 to the receiver filter 34. This allows for the simultaneous coupling of the receiver 20 and the power amplifier stage 12 to an antenna 42 via a duplexer 44. The duplexer connects to the antenna 42 through an antenna port 40. The duplexer, having a transmitter port 36, a receiver port 38 and an antenna port 40, typically connects to the transmitter filter and receiver filter via fixed length microstrip lines 41 and 43 at the duplexer's transmitter port 36 and the duplexer's receiver port 38 respectively.

0017Operationally, the phase shift of the microstrip lines 41 and 43 are designed to convert receiver filter impedance at transmitter frequencies to "open circuits" and receiver filter impedance at receiver frequency to "closed circuits." Likewise, the transmitter filter impedance at receiver frequencies are seen as "open circuits" while the transmitter impedance at transmitter frequencies are seen as "closed circuits." Thus, both filters "see" only the antenna at their pass band frequencies, and are practically disconnected at their stop band frequencies. The duplexer preferably provides 70 dB isolation between the transmitter signal and the receiver input. This isolation is critical to avoid the receiver's sensitivity degradation due to the transmitter phase noise. The 70 dB isolation between the transmitter power emitting from the power amplifier stage 12 and the receiver's (20) input (or the isolation between the output ports of switch 24) is accomplished by using several PIN diodes and microstrip transmission lines.

0018In half-duplex operation, the switch 24 uncouples from the transmitter filter 32 and couples to the receiver filter 34 so that transmitter power is delivered to the antenna through the receiver filter 34. Filter 34 attenuates harmonics from the power amplifier and helps reduce costs by avoiding the need for additional low pass filters. Switch 26 isolates the power signal present at the receiver filter's (34) input from the receiver's input (19), thereby avoiding burnout of the receiver 20. At least a single PIN diode switch (26) is used to obtain approximately 20dB isolation.

0019Referring to Figure 2, there is shown another FD/HD radio 50 in accordance with the present invention. Radio 50, as in radio 10 of Figure 1 , includes a power amplifier 12 which preferably comprises an exciter 14, a driver 16, and a final power amplifier 18. Radio 50 also includes a receiver 20 having an input port 19. During full duplex operation, the receiver 20 and power amplifier 12 are coupled to a receiver filter 34 and transmitter filter 32 respectively. Both filters are preferably monolithic ceramic block combline band pass filters which have the same passband ranges as the filters in radio 10.

0020During half-duplex operation, the power amplifier 12 uncouples from the transmitter filter 32 and couples to another filter 48, which preferably is tuned to eliminate harmonics and typically being a low pass filter. The power amplifier 12 transmits power through the low pass filter during half duplex operation. The low pass filter 48 also attenuates harmonics from the power amplifier. In this embodiment of the present invention, the half- duplex mode allows radio 50 to by-pass both the receiver filter and the transmitter filter (32 and 34.)

0021The radio 50 interchangeably switches from full duplex to half-duplex using a switching means 23 which can preferably comprise at least two PIN diode switches 21 and 25. Typically, a controller unit (not shown) can send a control signal or signals to the switching means (23) to direct the mode of operation of the radio 50.

0022In full duplex operation, the radio 50 is required to talk and listen simultaneously. Therefore, the switch 21 couples the power amplifier 12 to the transmitter filter 32. A duplexer 44, having a receiver port 38, a transmitter port 36, and an antenna port 40, couples the transmitter filter 32 to the receiver filter 34. During full duplex operation the switch 25 couples the antenna 42 to the antenna port 40 of the duplexer 44. During half duplex operation the switch 21 uncouples the power amplifier 12 from the transmitter filter 32 and couples the power amplifier 12 to the low pass filter 48. Simultaneously, the switch 25 uncouples the duplexer's (44) antenna port 40 from the antenna 42 and couples the antenna 42 to the low pass filter 48. The transmitter filter 32 and receiver filter 34 "see" only the antenna at their pass band frequencies, and are practically disconnected at their stop band frequencies. The duplexer 44, as in radio 10, preferably provides 70 dB isolation between the transmitter signal and the receiver input. Also, at full-duplex operation, the 70 dB isolation between the transmitter power emitting from the power amplifier 12 and the receiver's (20) input is accomplished by using switching means 23 which may preferably include several PIN diodes and microstrip transmission lines. In half-duplex operation, approximately 20 dB of isolation is obtained using switch 25.

0023Again referring to Fig. 2, an alternative embodiment of the present invention (not shown) may include a power amplier that includes only an exciter 14 and driver 16 which is connected to switch 21. The Final amplifier 18 is connected to the transmitter filter 32. In full-duplex operation, the switch 21 connects the driver 16 to the final amplifier 18. In half-duplex operation, the switch 21 uncouples the driver 16 from the final amplifier 18 and connects to low-pass filter 48. Otherwise, the alternative embodiment operates similarly to the radio 50 of Figure 2. What is claimed is: