Simultaneous transmit and receive (STR) structures immune to phase and amplitude imbalances
View Patent ↗An echo-canceling unit for a simultaneous transmit and receive (STR) system includes at least three phase shifters instead of just two phase shifters in order to provide immunity to phase and/or amplitude imbalances. Each respective phase shifter is coupled to a transmit signal to generate an output signal comprising a selected phase shift with respect to the transmit signal. A weight calculation unit generates a corresponding amplitude-weight signal for the output signal of the phase shifter. A variable attenuator attenuates the output signal of each respective phase shifter based on the corresponding amplitude-weight signal to form an echo-cancelation signal component corresponding to the phase shifter. A first summer then sums the respective echo-cancelation signal components into a received signal containing an echo signal to form an echo-canceled signal. In some embodiments, an information handling system includes a receiver and a transmitter coupled to the echo-canceling unit.
1. An echo-canceler for a simultaneous transmit and receive (STR) system, comprising:
at least three phase shifters, each respective phase shifter being coupled to a transmit signal of the STR system to generate an output signal comprising a selected phase shift with respect to the transmit signal, the transmit signal comprising a 3 rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) transmit signal;
a weight calculation unit coupled to the output signal of each respective phase shifter, each weight calculation unit to generate a corresponding amplitude-weight signal for the output signal of the phase shifter;
a variable attenuator to attenuate the output signal of each respective phase shifter based on the corresponding amplitude-weight signal to form an echo-cancelation signal component corresponding to the phase shifter; and
a first summer to sum the respective echo-cancelation signal components into a received signal containing an echo signal to form an echo-canceled signal.
2. The system according to claim 1 , wherein each phase shifter is a fixed-phase phase shifter.
3. The system according to claim 1 , wherein a first phase shifter of the at least three phase shifters generates a nominal phase shift of 0° with respect to the transmit signal, a second phase shifter of the at least three phase shifters generates a nominal phase shift of 60° with respect to the transmit signal, and a third phase shifter of the at least three phase shifters generates a nominal phase shift of 120° with respect to the transmit signal.
4. The system according to claim 1 , wherein the at least three phase shifters comprise part of a vector modulator.
5. The system according to claim 1 , wherein the system further comprises a plurality of vector modulators, each vector modulator comprising:
at least three phase shifters, each phase shifter being coupled to the transmit signal of the STR system at a selected tap of the transmit signal to generate an output signal comprising a selected phase shift from the transmit signal with respect to the selected tap;
a weight calculation unit coupled to the output signal of each respective phase shifter of the vector modulator to generate a corresponding amplitude-weight signal for the output signal of the phase shifter;
a variable attenuator to attenuate the output signal of each respective phase shifter based on the corresponding amplitude-weight signal to form an echo-cancelation signal component corresponding to the output signal of the phase shifter; and
a second summer to sum the respective echo-cancelation signal of the vector modulator into an echo-cancelation signal for the vector modulator, and
wherein the first summer sums the respective echo-cancelation signals of the respective vector modulators into the received signal containing an echo signal to form the echo-canceled signal.
6. The system according to claim 5 , wherein a first phase shifter of the at least three phase shifters of at least one vector modulator generates a nominal phase shift of 0° from the transmit signal with respect to the selected tap, a second phase shifter of the at least three phase shifters of the at least one vector modulator generates a nominal phase shift of 60° from the transmit signal with respect to the selected tap, and a third phase shifter of the at least three phase shifters of the at least one vector modulator generates a nominal phase shift of 120° from the transmit signal with respect to the selected tap.
7. The system according to claim 1 , wherein each phase shifter is a variable-phase phase shifter, and
wherein the weight calculation unit is to further generate a variable-phase weight signal corresponding to the output signal of the phase shifter that varies a phase of the phase shifter.
8. The system according to claim 7 , wherein each respective phase shifter is coupled to the transmit signal of the STR system at a different selected tap of the transmit signal to generate an output signal comprising a phase shift from the transmit signal with respect to the selected tap based on the variable-phase weight signal.
9. An information-handling system, comprising:
a receiver capable of receiving a signal, the received signal containing an echo signal and comprising a 3 rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) downlink signal;
a transmitter capable of transmitting a transmit signal simultaneously as the receiver receives the received signal; and
an echo-canceling unit coupled to the transmit signal and the received signal to generate an estimated echo signal, the echo-canceler comprising:
at least three phase shifters, each respective phase shifter to generate an output signal comprising a selected phase shift with respect to the transmit signal;
a first signal attenuator to attenuate the output signal of each respective phase shifter based on a weight signal corresponding to the output signal of the phase shifter to form an echo-cancelation signal component corresponding to the phase shifter; and
a second signal combiner to combine the respective echo-cancelation signal components into the received signal containing the echo signal to form an echo-canceled signal.
10. The information-handling system according to claim 9 , wherein the echo-canceling unit further comprises a weight calculation unit to generate the weight signal for the output signal of the phase shifter.
11. The information-handling system according to claim 9 , wherein each phase shifter is a fixed-phase phase shifter.
12. The information-handling system according to claim 9 , wherein a first phase shifter of the at least three phase shifters generates a nominal phase shift of 0° with respect to the transmit signal, a second phase shifter of the at least three phase shifters generates a nominal phase shift of 60° with respect to the transmit signal, and a third phase shifter of the at least three phase shifters generates a nominal phase shift of 120° with respect to the transmit signal.
13. The information-handling system according to claim 9 , wherein the at least three phase shifters comprise part of a vector modulator.
14. The information-handling system according to claim 9 , wherein the echo-canceling unit further comprises a plurality of vector modulators, at least one vector modulator comprising:
the at least three phase shifters; and
at least three weight calculation units, each weight calculation unit to generate a weight signal for the output signal of a corresponding phase shifter;
wherein the first signal attenuator is to attenuate the output signal of each respective phase shifter based on the corresponding weight signal to form an echo-cancelation signal component corresponding to the phase shifter; and
wherein the second signal combiner is to combine the respective echo-cancelation signal components into the received signal containing the echo signal to form the echo-canceled signal.
15. The information-handling system according to claim 14 , wherein a first phase shifter of the at least three phase shifters of at least one vector modulator generates a nominal phase shift of 0° from the transmit signal with respect to the selected tap, a second phase shifter of the at least three phase shifters of the at least one vector modulator generates a nominal phase shift of 60° from the transmit signal with respect to the selected tap, and a third phase shifter of the at least three phase shifters of the at least one vector modulator generates a nominal phase shift of 120° from the transmit signal with respect to the selected tap.
16. The information-handling system according to claim 9 , wherein each phase shifter is a variable-phase phase shifter, and
wherein echo-canceling unit further comprises a weight calculation unit corresponding to each phase shifter to generate a variable-phase weight signal corresponding to the output signal of the phase shifter that varies a phase of the phase shifter.
17. The information-handling system according to claim 9 , wherein the information-handling system comprises a cellular telephone, smartphone, smart-type device, or tablet-type device.
18. The information-handling system according to claim 17 , wherein the cellular telephone, smartphone, smart-type device, or tablet-type device further comprises a touchscreen display capable of receiving input information from a touch of a user or a stylus.