Wireless Transceiver Impairment Compensation Using Auxiliary Receiver
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Solution Overview
Problem
Existing methods for compensating DC offset and IQ imbalance in mobile wireless communications devices are inefficient as they require data transmission to be halted during training or compensation, and struggle to accurately separate impairments introduced by the transmitter and receiver.
Innovation Solution
A mobile wireless communications device with an auxiliary receiver and controller that estimates and compensates for transmit impairments in real-time by comparing transmit and receive baseband signals, allowing compensation during regular operation without the need for external test equipment, using a non-directional coupler and least means square algorithm for iterative correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional DC offset and IQ imbalance compensation methods are used, then transmitter impairments can be compensated, but data transmission must be halted during training or compensation
Solution Approach 1:
The patent applies preliminary action by performing impairment compensation in the background before data transmission begins, using training signals to calibrate the transmitter and receiver. This allows the system to prepare compensation parameters in advance, so that when actual data transmission occurs, the impairments are already compensated and continuous transmission can proceed without interruption.
Solution Approach 2:
The patent implements periodic action by periodically updating compensation parameters during operation using background calibration techniques. The system periodically inserts training signals or uses pilot symbols to refresh impairment estimates, allowing continuous data transmission while maintaining up-to-date compensation without requiring complete transmission halts.
2Reliability
If impairment compensation is performed using existing methods, then some level of compensation is achieved, but transmitter and receiver impairments cannot be accurately separated
Solution Approach 1:
The patent applies segmentation by dividing the total impairment into separate transmitter and receiver components. It uses separate training signals transmitted in different directions (forward and reverse) to independently measure and characterize transmitter impairments and receiver impairments. This segmentation allows each component to be compensated separately, improving overall compensation effectiveness.
Solution Approach 2:
The patent uses an intermediary approach by introducing a known training signal as a mediator between the transmitter and receiver. This training signal serves as a reference that allows the system to isolate and measure impairments introduced by each component. By comparing the transmitted training signal with the received version, the system can precisely identify and separate transmitter and receiver impairments.
3Measurement precision
If external test equipment is used for compensation, then accurate impairment measurement is possible, but device complexity and cost increase
Solution Approach 1:
The patent implements self-service by enabling the wireless communication device to perform its own impairment measurement and compensation without external test equipment. The device uses its own transmitter and receiver, along with internally generated training signals, to measure and compensate for its own impairments. This self-contained approach reduces device complexity and eliminates the need for external calibration equipment.
Solution Approach 2:
The patent uses copying by creating an internal model or representation of the impairment characteristics through training signals. Instead of requiring external equipment to directly measure impairments, the system copies the impairment effects by comparing transmitted and received training signals, then uses this copied information to generate compensation parameters. This virtual modeling approach replaces the need for physical external test equipment.
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AI summary
A mobile wireless communications device includes a transceiver, an auxiliary receiver and a controller. The transceiver includes a transmitter and a receiver. The transmitter upconverts a transmit baseband modulated signal and generates an RF modulated signal having a transmit impairment. The auxiliary receiver is coupled to the transmitter and downconverts the RF modulated signal and generates a receive baseband modulated signal having a receive impairment therein spectrally separated from the transmit impairment. The controller is coupled to the transmitter and the auxiliary receiver and estimates the transmit impairment while ignoring the receive impairment based on comparing the transmit baseband modulated signal with the receive baseband modulated signal. The controller generates an impairment compensation signal based upon the estimated transmit impairment.