Digital Predistortion Using Shared Receive Path ADCs
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Solution Overview
Problem
In wireless transceivers, achieving high linearity in power amplifiers for broadband communications is challenging, especially in combination with high efficiency, which is crucial for battery life in mobile devices and operational costs in basestations, and existing digital predistortion methods require multiple analog-to-digital converters and complex circuitry.
Innovation Solution
A method and circuitry for digital predistortion in time-domain duplexed transceivers that enables power amplifier feedback signals to be carried by the main receive path during transmit periods and received signals during receive periods, sharing analog-to-digital converters to reduce complexity and cost while maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital predistortion is implemented using conventional methods with separate feedback path ADCs, then measurement precision for power amplifier output is improved, but device complexity and manufacturing cost increase due to requiring multiple ADCs
Solution Approach 1:
The patent merges the feedback path ADCs with the main receive path ADCs, allowing the same ADCs to serve dual purposes: converting received signals during receive periods and converting power amplifier feedback signals during transmit periods. This consolidation eliminates the need for separate feedback ADCs, reducing device complexity and manufacturing cost while maintaining measurement precision through time-division multiplexing.
Solution Approach 2:
The main receive path ADCs are designed to perform multiple functions: they convert received signals during TDD receive periods and convert power amplifier feedback signals during TDD transmit periods. This multi-functionality allows a single set of ADCs to replace what would traditionally require separate dedicated feedback ADCs, thereby reducing overall device complexity while preserving measurement capabilities.
2Device complexity
If time-domain duplexing is used to share ADCs between feedback and receive paths, then device complexity is reduced, but reliability may worsen due to potential interference between feedback signal processing and receive signal processing
Solution Approach 1:
The patent employs periodic time-division multiplexing where the shared ADCs are allocated to feedback signal processing during transmit periods and to receive signal processing during receive periods. This periodic alternation ensures that feedback and receive signals are processed at different times, eliminating interference while maintaining signal processing reliability. The TDD frame structure naturally provides this periodic separation.
3Reliability
If multiple ADCs are used for feedback and receive paths separately, then reliability of signal processing is improved, but manufacturing cost and ease of manufacture worsen
Solution Approach 1:
The patent merges the feedback path ADCs with the main receive path ADCs into a single shared ADC system. This consolidation reduces the total number of ADC components required, thereby lowering manufacturing cost and simplifying the manufacturing process. The merged ADCs maintain signal processing reliability through time-division multiplexing, ensuring that each signal type is processed with dedicated attention during its allocated time period.
Data Source
AI summary
A transceiver for time-domain duplexed (TDD) communications, for example in connection with wireless broadband data communications, is disclosed. The transceiver includes digital predistortion compensation circuitry, which compensates the digital signals to be transmitted based on feedback signals from the output of the power amplifier, in order to linearize the output from the power amplifier. The feedback signals from the power amplifier are coupled back to the digital predistortion circuitry over part of the same receive path as the received signals from the wireless communications channel. The shared path includes analog-to-digital converters that are used both in the transmit period of the TDD cycle to convert the feedback signals from the power amplifier output, and in the receive period of the TDD cycle to convert the analog received signals.