Intermodulation Distortion Measurement Using RX Local Oscillator
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Solution Overview
Problem
Existing methods for measuring and calibrating intermodulation distortions in radio receivers, particularly intermodulation products of second order, face challenges such as the need for external TX signals, potential crosstalk issues, and the requirement of additional analogue blocks, which complicate the process and increase chip area usage.
Innovation Solution
The method involves using a second RX local oscillator to emulate an RF input signal with pulse modulation, switching the amplitude between levels, and detecting output signals to determine intermodulation distortions without relying on TX signal paths or local oscillators, thereby simplifying the measurement process and reducing hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external TX signals are used for measuring intermodulation distortions, then measurement capability is achieved, but chip area increases and crosstalk issues occur
Solution Approach 1:
The patent extracts the measurement function from the transmit path and implements it within the receive path using existing components. The second RX local oscillator generates test signals that remain confined to the receive signal path, eliminating the need for external TX signals and reducing chip area requirements while avoiding crosstalk between transmit and receive paths.
Solution Approach 2:
The patent makes the receive path components serve dual purposes: normal receive operations and intermodulation distortion measurement. The second RX local oscillator and receive signal path are used both for receiving actual signals and for generating/measuring test signals, eliminating dedicated measurement hardware and reducing overall chip area.
2Measurement precision
If external TX signals are used for measuring intermodulation distortions, then measurement capability is achieved, but crosstalk issues occur
Solution Approach 1:
The measurement function is extracted from the transmit path and implemented entirely within the receive path. By using the second RX local oscillator to generate test signals and confining all measurement activities to the receive signal path, the patent eliminates the source of crosstalk that would occur with external TX signals while preserving measurement capability.
3Measurement precision
If additional analogue blocks are added for measurement, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements measurement functionality using existing receive path components that already serve dual purposes. The second RX local oscillator, mixer, and signal path are used for both normal receive operations and intermodulation distortion measurement, eliminating the need for additional dedicated measurement hardware and reducing device complexity.
Solution Approach 2:
The receive path components serve themselves by performing both their primary receive function and the measurement function. The second RX local oscillator generates test signals, the mixer processes them, and the output is measured - all using existing components without requiring external measurement equipment or additional dedicated measurement blocks.
Data Source
AI summary
A method (300) for determining inter-modulation distortions products of a mixing stage includes: driving (301) a signal input of the mixing stage based on an input signal, wherein an amplitude of the input signal is switched between a first level and a second level, and wherein a frequency of switching the amplitude is smaller than a frequency of the input signal; detecting (302) at a signal output of the mixing stage a first output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the first level, and a second output signal responsive to the driving of the signal input with the input signal, wherein the amplitude of the input signal is switched to the second level; and determining (303) the inter-modulation distortions based on the first output signal and the second output signal.