Method and system for mitigating the effects of a transmitted blocker and distortions therefrom in a radio receiver
Noise caused by and leaking from a transmit signal into a radio-frequency (RF) receive path signal is reduced by forwarding the transmit signal to a first filter or a digital processor and DAC, scaling the transmit signal and approximating the noise, subtracting first and second corrective signals from the RF receive path signal, down-converting a resulting corrected RF receive path signal, filtering the down-converted corrected signal in a second filter, up-converting the filtered corrected signal to create the first corrective signal, and up-converting the filter or DAC output signal to create the second corrective signal. The transmit signal may come from an output of an RF power amplifier, and may be down-converted prior to filtering in the first filter or processing in the digital processor. The second filter may be a series filter or a shunt filter. A radio includes the circuits to perform the above method.
1. A method for reducing leakage noise occurring in a receive path of a radio system, the method comprising the following steps:
(a) forwarding a transmit signal from a transmit path of the radio system to a first filter, wherein the transmit signal is either in a baseband frequency range or in a low intermediate frequency range;
(b) scaling the transmit signal using the first filter; and
(c) forwarding the scaled transmit signal to a canceling down-converting mixer (CDM) in the receive path, wherein the CDM comprises circuitry to:
(i) subtract a first corrective signal from a radio-frequency (RF) receive path signal;
(ii) subtract a second corrective signal from the RF receive path signal, wherein the second corrective signal includes an approximation of a blocker being caused by and leaking from the transmit signal, and wherein subtracting the second corrective signal results in canceling at least a portion of the blocker;
(iii) down-convert a resulting corrected RF receive path signal;
(iv) filter the down-converted corrected signal in a second filter;
(v) up-convert the filtered corrected signal to create the first corrective signal; and
(vi) up-convert the scaled transmit signal to create the second corrective signal.
2. The method of claim 1 , wherein the transmit signal includes a digital signal, the method further comprising converting the digital signal to analog prior to canceling at least a portion of the blocker.
3. The method of claim 1 , wherein the transmit signal includes a signal from an output of a power amplifier, and wherein forwarding the scaled transmit signal further comprises down-converting the transmit signal.
4. The method of claim 1 , wherein the second filter is a series filter.
5. The method of claim 1 , wherein the second filter is a shunt filter.