LEAKAGE SIGNAL CANCELLATION APPARATUS

• US 20090232260A1
• Filed: 07/28/2006
• Published: 09/17/2009
• Est. Priority Date: 09/06/2005
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Hayashi, Ryoji, Takayama, Naohisa, Shimozawa, Mitsuhiro
• Granted Patent: US 7,899,142 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: G01S 7/038 Feedthrough nulling circuits
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A quadrature modulator divides a part of a transmitted signal to generate a cancel signal. A signal comparator compares the amplitude and phase of the cancel signal which is generated by the quadrature modulator with those of a received signal, and outputs signals corresponding to the comparison results to the quadrature modulator. The quadrature modulator generates the cancel signal on the basis of the output signals of the signal comparator, and these components perform feedback control such that the cancel signal has the same amplitude as the leakage signal and is in phase with the leakage signal. A combiner combines the cancel signal with an antiphase cancel signal, which is made to be in opposite phase with the cancel signal outputted from the quadrature modulator, to cancel out the leakage signal.

Claims

1. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for dividing a part of said transmitted signal so as to generate a cancel signal;

a signal comparing means for comparing an amplitude and a phase of the cancel signal generated by said quadrature modulator or said vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with an antiphase cancel signal whose phase is made to be opposite to that of the cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal, and wherein

said quadrature modulator or said vector modulator generates said cancel signal on a basis of the output signals outputted by said signal comparing means, and said quadrature modulator or said vector modulator and said signal comparing means perform feedback control in such a manner that said cancel signal has a same amplitude as said leakage signal and is in phase with said leakage signal.

7. The leakage signal cancellation apparatus according to claim 1, wherein said apparatus comprises a received signal switch disposed as a backward stage of the combiner, and a switch control means for carrying out on/off control of said received signal switch.

8. The leakage signal cancellation apparatus according to claim 7, wherein the switch control means turns off said received signal switch in a case in which the transmitted signal is a modulated signal having a state in which its signal level is equal to or lower than a predetermined level.

9. The leakage signal cancellation apparatus according to claim 1, wherein in a case in which the transmitted signal is a modulated signal having a state in which its signal level is equal to or lower than a predetermined level, said apparatus holds an input from the signal comparing means to the quadrature modulator or the vector modulator during transmission of the modulated signal.

10. The leakage signal cancellation apparatus according to claim 1, wherein the quadrature modulator or the vector modulator and the signal comparing means have a cancellation operation mode in which the leakage signal cancellation apparatus cancels out the leakage signal, and an adaptive operation mode in which the leakage signal cancellation apparatus follows the leakage signal which varies to generate the cancel signal, and keep the amplitude and phase of the cancel signal at constant in said cancellation operation mode.

11. The leakage signal cancellation apparatus according to claim 1, wherein said apparatus comprises a cancel signal switch for turning on or off an input of the cancel signal to the combiner, and, in a case in which the transceiver performs only a receiving operation without performing any transmitting operation, said leakage signal cancellation apparatus turns off said cancel signal switch.

2. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for dividing a part of said transmitted signal so as to generate an antiphase cancel signal;

a signal comparing means for comparing an amplitude and a phase of the antiphase cancel signal generated by said quadrature modulator or said vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with the antiphase cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal, and wherein

said quadrature modulator or said vector modulator generates said antiphase cancel signal on a basis of the output signals outputted by said signal comparing means, and said quadrature modulator or said vector modulator and said signal comparing means perform feedback control in such a manner that said antiphase cancel signal has a same amplitude as said leakage signal and is in opposite phase with said leakage signal.

3. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for generating a cancel signal on a basis of a signal from a local oscillator for generating a carrier wave for the transmitted signal;

a signal comparing means for comparing an amplitude and a phase of the cancel signal generated by said quadrature modulator or said vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with an antiphase cancel signal whose phase is made to be opposite to that of the cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal, and wherein

said quadrature modulator or said vector modulator generates said cancel signal on a basis of the output signals outputted by said signal comparing means, and said quadrature modulator or said vector modulator and said signal comparing means perform feedback control in such a manner that said cancel signal has a same amplitude as said leakage signal and is in phase with said leakage signal.

4. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for generating an antiphase cancel signal on a basis of a signal from a local oscillator for generating a carrier wave for the transmitted signal;

a signal comparing means for comparing an amplitude and a phase of the antiphase cancel signal generated by said quadrature modulator or said vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with the antiphase cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal, and wherein

said quadrature modulator or said vector modulator generates said antiphase cancel signal on a basis of the output signals outputted by said signal comparing means, and said quadrature modulator or said vector modulator and said signal comparing means perform feedback control in such a manner that said antiphase cancel signal has a same amplitude as said leakage signal and is in opposite phase with said leakage signal.

5. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a first quadrature modulator or a first vector modulator for quadrature-modulating signals which are acquired by complex-multiplying signals of I and Q channels which are outputted by a transmitter by signals for adjusting their amplitudes and phases, respectively, so as to generate a cancel signal;

a second quadrature modulator or a second vector modulator for quadrature-modulating the signals of I and Q channels which are outputted by said transmitter so as to generate said transmitted signal;

a signal comparing means for comparing an amplitude and a phase of the cancel signal generated by said first quadrature modulator or said first vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with an antiphase cancel signal whose phase is made to be opposite to that of the cancel signal outputted from said first quadrature modulator or said first vector modulator so as to cancel out said leakage signal, and wherein

said first quadrature modulator or said first vector modulator generates said antiphase cancel signal on a basis of signals which are acquired by complex-multiplying the output signals outputted by said signal comparing means by the signals of I and Q channels which are outputted by said transmitter, and said first quadrature modulator or said first vector modulator and said signal comparing means perform feedback control in such a manner that said cancel signal has a same amplitude as said leakage signal and is in phase with said leakage signal.

6. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprises comprising:

a first quadrature modulator or a first vector modulator for quadrature-modulating signals which are acquired by complex-multiplying signals of I and Q channels which are outputted by a transmitter by signals for adjusting their amplitudes and phases, respectively, so as to generate an antiphase cancel signal;

a second quadrature modulator or a second vector modulator for quadrature-modulating the signals of I and Q channels which are outputted by said transmitter so as to generate said transmitted signal;

a signal comparing means for comparing an amplitude and a phase of the antiphase cancel signal generated by said first quadrature modulator or said first vector modulator with those of said received signal, and for outputting signals corresponding to results of the comparison; and

a combiner for combining said received signal with the antiphase cancel signal outputted from said first quadrature modulator or said first vector modulator so as to cancel out said leakage signal, and wherein

said first quadrature modulator or said first vector modulator generates said antiphase cancel signal on a basis of signals which are acquired by complex-multiplying the output signals outputted by said signal comparing means by the signals of I channel and Q channel which are outputted by said transmitter, and said first quadrature modulator or said first vector modulator and said signal comparing means perform feedback control in such a manner that said antiphase cancel signal has a same amplitude as said leakage signal and is in opposite phase with said leakage signal.

12. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for dividing a part of said transmitted signal so as to generate a cancel signal;

a combiner for combining said received signal with the cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal;

a quadrature demodulator for converting the received signal outputted from said combiner into baseband I and Q signals so as to output I and Q error signals; and

first and second integrators for integrating said I and Q error signals, respectively, and wherein

said quadrature modulator or said vector modulator generates said cancel signal on a basis of output signals of said first and second integrators, and said quadrature modulator or said vector modulator, said quadrature demodulator, and said first and second integrators performs feedback control in such a manner that said cancel signal has a same amplitude as said leakage signal and is in phase with said leakage signal, and have a cancellation operation mode in which the leakage signal cancellation apparatus cancels out the leakage signal, and an adaptive operation mode in which the leakage signal cancellation apparatus follows the leakage signal which varies to generate the cancel signal, and keep the amplitude and phase of the cancel signal at constant in said cancellation operation mode.

13. A leakage signal cancellation apparatus which cancels out a leakage signal which is leakage of a transmitted signal to a received signal in a transceiver, said apparatus comprising:

a quadrature modulator or a vector modulator for dividing a part of said transmitted signal so as to generate a cancel signal;

a combiner for combining said received signal with the cancel signal outputted from said quadrature modulator or said vector modulator so as to cancel out said leakage signal;

a cancel signal switch for turning on or off an input of the cancel signal to said combiner;

a quadrature demodulator for quadrature-demodulating the received signal outputted from said combiner so as to output I and Q error signals; and

first and second integrators for integrating said I and Q error signals, respectively, and wherein

said quadrature modulator or said vector modulator generates said cancel signal on a basis of output signals of said first and second integrators, said quadrature modulator or said vector modulator, said quadrature demodulator, and said first and second integrators performs feedback control in such a manner that said cancel signal has a same amplitude as said leakage signal and is in phase with said leakage signal, and, in a case in which the transceiver performs only a receiving operation without performing any transmitting operation, said leakage signal cancellation apparatus turns off said cancel signal switch.