Adjustable electronic duplexer
A duplexer for a communication device having a transmission unit, a reception unit and a shared antenna is disclosed. The duplexer comprises a first signal path between the transmission unit and the reception unit, the first signal path comprises a filter unit filtering the reception signal, the filtering unit provides a filtered signal to the reception unit. The duplexer further comprises a second signal path between the transmission unit and the reception unit. The second signal path comprises a cancellation unit which receives a sample of the transmission signal and produces a compensation signal. The injection of the compensation signal to the first signal path reduces the leakage signal, thereby producing a substantially leakage-free reception signal.
1. A duplexer for a communication device having a transmission unit, a reception unit and a shared antenna, the duplexer comprising:
a transmitter port adapted to receive a transmission signal from the transmission unit;
a receiver port adapted to transmit a reception signal to the reception unit;
an antenna port adapted to transmit the transmission signal to the shared antenna and receive the reception signal from the shared antenna;
a first signal path between said transmitter port and said receiver port;
a filter unit in said first signal path for filtering said reception signal, said filter unit causing a leakage signal to occur between said transmitter port and said receiver port;
a second signal path between said transmitter port and said receiver port; and
a cancellation unit in said second signal path adapted to receive a sample of the transmission signal and produce a compensation signal that is injected into the first signal path to substantially reduce the leakage signal.
2. The duplexer according to claim 1 , wherein said cancellation unit comprises:
a. an attenuator for attenuating the sample of the transmission signal to an amplitude substantially equal to the amplitude of said leakage signal; and
b. a phase-converter for shifting the phase of the transmission signal substantially 180-degree relative to the phase of the leakage signal.
3. The duplexer according to claim 1 , further comprising a first coupling unit at a juncture between said first and second signal paths for injecting the compensation signal to the first signal path.
4. The duplexer according to claim 3 , wherein said first coupling unit is located downstream from said filter unit.
5. The duplexer according to claim 4 , wherein said cancellation unit comprises:
a. an attenuator for attenuating the sample of the transmission signal to an amplitude substantially equal to the amplitude of said leakage signal; and
b. a phase-converter for shifting the phase of the transmission signal substantially 180-degree relative to the phase of the leakage signal.
6. The duplexer according to claim 5 , further comprising a second coupling unit at a juncture between said first and second signal paths for providing said sample of the transmission signal to said compensation unit.
7. The duplexer according to claim 6 , wherein said filtering unit comprises a band-pass filter.
8. The duplexer according to claim 7 , whereIn, said filtering unit comprises a YIG filter.
9. The duplexer according to claim 6 , wherein the attenuation of said attenuator and the shifting of said phase-converter are variable according to a control voltage.
10. The duplexer according to claim 9 , further comprising a third signal path between said first signal path and said compensation unit, said third signal path comprising a control unit receiving a sample of a substantially leakage-free reception signal and producing said control voltage for input to said compensation unit.
11. The duplexer according to claim 10 , wherein said filtering unit comprises a band-pass filter.
12. The duplexer according to claim 11 , wherein said filtering unit comprises a YIG filter.
13. A method for interfacing a transmission unit, a reception unit and a shared antenna within a duplexer, the method comprising:
receiving at a transmitter port a transmission signal from said transmission unit;
transmitting said transmission signal to said shared antenna via an antenna port;
receiving a reception signal from said shared antenna via said antenna port;
filtering said reception signal in a first signal path between said transmitter port and a receiver port, said filtering causing a leakage signal to occur between said transmitter port and said receiver port;
sampling said transmission signal and computing a compensation signal having an amplitude substantially equal to the amplitude of said leakage signal and a phase substantially 180-degree shifted from the phase of the leakage signal; and
injecting said compensation signal into said first signal path to be added to said reception signal and thereby substantially reduce said leakage signal.
14. The method of claim 13 , further comprising controlling the amplitude and phase-shift of the compensation signal in accordance with a control voltage which is a function of a substantially leakage-free reception signal.