Baseband Distortion Cancellation in Wireless Receivers
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Solution Overview
Problem
Wireless communication devices face challenges in reducing intermodulation and harmonic distortion caused by multiple transmitters, leading to receiver desensitization, which existing solutions like reducing transmitter power or using additional RF components do not adequately address, especially for higher order distortions and non-DC baseband frequencies.
Innovation Solution
The method involves generating a baseband replica distortion signal using transmit signals, converting it to a low frequency signal, and subtracting it from the received signal to cancel odd-order intermodulation or harmonic distortion, using an adaptive baseband distortion canceller with complex digital mixers and least mean squared filters to create a correcting signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional RF components (diplexers, separate antennas) are used to isolate transmit signals, then transmitter isolation is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a digital copy of the transmit signals at baseband and uses this copy to generate intermodulation distortion products that cancel the actual distortion. Instead of using physical isolation components, the system copies the signal characteristics and processes them digitally to achieve cancellation.
Solution Approach 2:
The patent replaces physical RF isolation components (diplexers, separate antennas) with a digital signal processing system. The mechanical/physical isolation approach is substituted by generating and subtracting digital representations of distortion products, eliminating the need for additional RF hardware.
2Object-generated harmful factors
If transmitter power is reduced to lower intermodulation distortion, then distortion is reduced, but uplink performance deteriorates
Solution Approach 1:
The patent takes the harmful intermodulation distortion products and converts them into useful cancellation signals. By generating replica distortion products from the transmit signals and subtracting them from the received signal, the harmful distortion is transformed into a beneficial cancellation mechanism.
Solution Approach 2:
The patent introduces an intermediary digital signal processing stage that generates cancellation signals. This intermediary system creates replica distortion products that act as counter-signals to neutralize the actual distortion, allowing full transmitter power to be used without distortion penalties.
3Object-generated harmful factors
If baseband cancellation methods are used to remove distortion, then distortion cancellation is improved, but additional calibration hardware and software are required
Solution Approach 1:
The patent enables the system to self-cancel its own distortion by using the transmit signals themselves to generate the cancellation products. The system serves itself by taking the known transmit waveforms, processing them through the same non-linearity model, and using the output to cancel the actual distortion without requiring external calibration hardware.
Data Source
AI summary
A method (600) and apparatus (200) cancel odd-order distortion signals. Desensitization can be determined (610) in a received signal caused by odd-order harmonic distortion occurring from at least one transmit signal. A baseband replica harmonic distortion signal can be generated (620) using the transmit signal. The baseband replica harmonic distortion signal can be converted (630) to a low frequency harmonic distortion signal. The low frequency harmonic distortion signal can be subtracted (640) from the received signal to cancel the odd-order distortion from the received signal to create a corrected signal.