Linearization of Multi-Antenna Receivers with RF Pre-Distortion

• US 20130177116A1
• Filed: 01/10/2012
• Published: 07/11/2013
• Est. Priority Date: 01/10/2012
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wyville, Mark William
• Granted Patent: US 9,001,947 B2
• Time in Patent Office: Days
• US Class Current: 375/349
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input

Abstract

A receiver includes a first receiver chain configured to receive a first input signal and a second receiver chain configured to receive a second input signal. A first phase predistorter is provided in the first receiver chain and is configured to shift a phase of the first input signal by a first phase shift φ′_A(f). A combiner is coupled to the first receiver chain and the second receiver chain and combines the first and second input signals. The first phase shift is selected to cause undesired signal components received in the first and second input signals to combine destructively.

Claims

1. A receiver, comprising:

a first receiver chain configured to receive a first input signal;

a second receiver chain configured to receive a second input signal;

a first phase predistorter in the first receiver chain configured to shift a phase of the first input signal by a first phase shift φ

_A(f); and

a combiner coupled to the first receiver chain and the second receiver chain and configured to combine the first and second input signals;

wherein the first phase shift is selected to cause undesired signal components induced in the first and second input signals by nonlinear processing in the receiver to combine destructively.

2. The receiver of claim 1, further comprising:

a second phase predistorter in the second receiver chain configured to shift a phase of the second input signal by a second phase shift φ

′

_B(f);

wherein the first phase shift and the second phase shift are jointly selected to cause the undesired signal components in the first and second input signals to combine destructively.

3. The receiver of claim 2, wherein the undesired signal components comprise intermodulation distortion (IMD) products of a first undesired signal and a second undesired signal, wherein a phase difference between a first one of the IMD products in the first input signal and a second one of the IMD products in the second input signal has the form:

Δ

′

<sub>φ

,IM3</sub>=2Δ

′

₁₀₀ (f₂)−

Δ

′

<sub>φ

(</sub>f₁)

wherein Δ

′

_Φ

(f) is defined as (φ

_A)f)+φ

′

_A(f))−

(φ

_B(f)+φ

′

_B(f)), f₁ is a fundamental frequency of the first undesired signal, f₂ is a fundamental frequency of the second undesired signal, and wherein φ

′

_A(f) and φ

′

_B(f) are selected such that Δ

<sub>φ

,IM3</sub> is about +/−

180 degrees.

4. The receiver of claim 1, further comprising:

a control circuit coupled to the combiner and to the first phase predistorter and configured to control a phase shift of the first phase predistorter.

5. The receiver of claim 1, wherein the combiner is further configured to multiply the first and second input signals by weights to form weighted input signals and to combine the weighted input signals to form a combined input signal.

6. The receiver of claim 5, further comprising:

a control circuit coupled to the combiner and to the first phase predistorter and configured to control a phase shift of the first phase predistorter and configured to generate the complex weights;

wherein the complex weights are selected to increase the destruction of the undesired signal components in the first and second weighted input signals when the first and second weighted input signals are combined.

7. The receiver of claim 1, wherein the first receiver chain comprises a low noise amplifier;

and

wherein the first phase predistorter is provided in the first receiver chain between the first input and the low noise amplifier.

8. The receiver of claim 1, wherein the first receiver chain comprises a low noise amplifier;

and

wherein the first phase predistorter is provided in the first receiver chain after the low noise amplifier.

9. The receiver of claim 8, wherein the first receiver chain comprises a mixer, and wherein the first phase predistorter is provided in the first receiver chain between the low noise amplifier and the mixer.

10. The receiver of claim 1, wherein the second receiver chain does not include a phase predistorter.

11. The receiver of claim 1, wherein the first phase predistorter comprises an all-pass filter having a tunable phase response.

12. The receiver of claim 11, wherein the first phase predistorter comprises a lattice filter.

13. The receiver of claim 11, wherein the first phase predistorter is free of active circuit components.

14. A receiver, comprising:

a first antenna configured to receive a first input signal;

a second antenna configured to receive a second input signal;

a first phase predistorter coupled to the first antenna and configured to receive the first input signal and shift a phase of the first input signal by a first phase shift V_A(f);

a combiner configured to combine the first and second input signals; and

an amplifier coupled between the first phase predistorter and the combiner;

wherein the first phase shift is selected to cause undesired signal components induced in the first and second input signals to combine destructively by nonlinear processing in the receiver.

15. A method of processing a signal that is received on multiple antennas, comprising:

receiving a first input signal from a first antenna;

receiving a second input signal from a second antenna;

shifting a phase of the first input signal by a first phase shift 4′

_A(f); and

combining the first and second input signals;

wherein the first phase shift is selected to cause undesired signal components induced in the first and second input signals by nonlinear processing to combine destructively.

16. The method of claim 15, further comprising:

shifting a phase of the second input signal by a second phase shift φ

′

_B(f);

wherein the first and second phase shifts are selected to cause the undesired signal components in the first and second input signals to combine destructively.

17. The method of claim 16, wherein the undesired signal components comprise intermodulation distortion (IMD) products of a first undesired signal and a second undesired signal, wherein a phase difference between a first one of the IMD products received in the first input signal and a second one of the IMD products received in the second input signal has the form:

Δ

′

<sub>φ

,IM3</sub>=2Δ

′

<sub>φ

(</sub>f₂)−

Δ

′

_φ

(f₁)

wherein Δ

′

₁₀₀(f) is defined as (φ

_A(f)+φ

′

_A(f))−

(φ

_B(f)+φ

′

_B(f)), f₁ is a fundamental frequency of the first undesired signal, f₂ is a fundamental frequency of the second undesired signal, and f_R is a fundamental frequency of a desired signal, and wherein φ

′

_A(f) and φ

′

_B(f) are selected such that Δ

<sub>φ

,IM3</sub> is about +/−

180 degrees.