# US 2018/0026673 A1 · Method and system for mitigating the effects of a transmitted blocker and distortions therefrom in a radio receiver

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- Number: US 2018/0026673 A1
- Document ID: US20180026673A1
- Status: Published application
- Kind: A1
- Application number: 15/618,741
- Filed: 2017-06-09
- Published: 2018-01-25
- Earliest claimed: 2012-11-14
- Assignees: Spectra7 Microsystems Corp.
- Applicants: Spectra7 Microsystems Ltd
- Inventors: Andrew Joo Kim; Stephane Laurent-Michel; Stephen Jantzi
- Web page: https://patentgrep.com/patent/US20180026673A1

## CPC

- H04B 1/525: with means for reducing leakage of transmitter signal into the receiver
- H04B 1/1027: {assessing signal quality or detecting noise/interference for the received signal}
- H04L 7/033: using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
- H04L 25/061: {providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of DC offset (removal of DC offset in coupling arrangements H04L25/029, H04L25/0296)}
- H04L 25/062: {Setting decision thresholds using feedforward techniques only}
- H04L 27/2647: {Arrangements specific to the receiver only (equalisation H04L27/01)}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

The method of claim 1, wherein the second filter is a series filter.

### Claim 5 (depends on 1)

The method of claim 1, wherein the second filter is a shunt filter.

### Claim 6

A radio, comprising:
(a) a digital processor including an input coupled with an output of a baseband transmit module, wherein the baseband transmit module is configured to output a digitally modulated digital signal in one of a baseband frequency range and a low intermediate frequency range, and wherein the digital processor is configured to process the digitally modulated digital signal to construct an approximation of noise caused by and leaking from a transmit signal into a radio-frequency (RF) receive path signal;
(b) a digital-to-analog converter (DAC) including a data input coupled with an output of the digital processor; and
(c) a canceling down-converting mixer (CDM) in a receive path including an input coupled with an output of the DAC, wherein the CDM comprises circuitry to:
(i) subtract a first corrective signal from the RF receive path signal;
(ii) up-convert a DAC output signal to create a second corrective signal, wherein the second corrective signal includes the noise approximation;
(iii) subtract the second corrective signal from the RF receive path signal, wherein subtracting the second corrective signal results in canceling at least a portion of the noise;
(iv) down-convert a resulting corrected RF receive path signal;
(v) filter the down-converted corrected signal; and
(vi) up-convert the filtered corrected signal to create the first corrective signal.

### Claim 7

A radio, comprising:
(a) a first down-converting mixer including a first input coupled with a location in a transmit path carrying a radio-frequency (RF) transmit signal, a second input coupled with a local oscillator, and an output, wherein the first down-converting mixer is configured to down-convert the RF transmit signal to one of a baseband frequency range and a low intermediate frequency range; and
(b) a first filter including an input coupled with the first down-converting mixer output and an output coupled with an input of a canceling down-converting mixer (CDM) in a receive path, wherein the first filter is configured to create an approximation of noise caused by and leaking from the transmit signal into a radio-frequency (RF) receive path signal, and wherein the CDM comprises circuitry to:
(i) subtract a first corrective signal from the RF receive path signal;
(ii) up-convert a first filter output signal to create a second corrective signal, wherein the second corrective signal includes the noise approximation;
(iii) subtract the second corrective signal from the RF receive path signal, wherein injecting the second corrective signal results in canceling at least a portion of the noise;
(iv) down-convert a resulting corrected RF receive path signal;
(v) filter the down-converted corrected signal; and
(vi) up-convert the filtered corrected signal to create the first corrective signal.