Observation ADC Hybrid Sampling for Low-Noise Transceiver Calibration
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Solution Overview
Problem
In multi-GHz transceivers, non-linear distortions and memory effects in ADCs and DACs lead to spurious tones, spectral regrowth, and degradation in spurious-free dynamic range (SFDR) and error vector magnitude (EVM), particularly severe at high signal levels and critical for wideband operation.
Innovation Solution
Implementing a combined uniform and non-uniform sampling scheme in the observation path of the transceiver, where the observation ADC is activated at both regular and irregularly spaced sampling instants, with only valid samples from uniform sampling used for calibration, reducing noise and power dissipation while maintaining high dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If non-uniform sampling is used in the observation path, then power dissipation is reduced and noise is lowered, but random transients are generated at the buffer output
Solution Approach 1:
The patent changes the sampling parameter from purely non-uniform to a hybrid scheme that combines uniform and non-uniform sampling. The ADC is activated at uniform sampling instants (every Nth sample) to provide stable reference points, while also allowing non-uniform sampling at intermediate points to reduce power consumption and noise. This parameter modification resolves the contradiction by maintaining the benefits of non-uniform sampling while mitigating its harmful effects through periodic uniform sampling.
2Measurement precision
If the observation ADC is activated continuously at high rate, then measurement precision is improved, but power dissipation increases
Solution Approach 1:
The patent implements periodic activation of the observation ADC where the ADC is turned on at regular intervals (every Nth sample instant) rather than continuously. This periodic operation maintains measurement precision by capturing signals at uniform sampling points while significantly reducing power dissipation by keeping the ADC inactive during intermediate periods. The uniform sampling instants provide stable reference measurements despite the reduced activation frequency.
3Use of energy by moving object
If irregular sampling instants are used, then power dissipation is reduced, but spurious tones appear in the ADC output spectrum
Solution Approach 1:
The patent modifies the sampling pattern parameter from purely irregular to a hybrid pattern combining uniform and non-uniform elements. By activating the ADC at uniform instants (every Nth sample) rather than purely irregular intervals, the patent eliminates spurious tones in the ADC output spectrum while still reducing power dissipation compared to continuous activation. The uniform sampling points provide spectral purity while the reduced frequency of activation maintains energy efficiency.
Data Source
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AI summary
A method and system for controlling an analog-to-digital converter (ADC) in an observation path in a transceiver. The transceiver includes a transmit path, a receive path, and an observation path. The observation path includes an analog buffer and an observation ADC. A controller generates a control signal to control sampling events at the observation ADC to activate the observation ADC at combined uniform and non-uniform sampling instants. The controller may also generate a second control signal indicating whether digital data obtained by the observation ADC is valid or not. The digital data generated by the observation ADC at non-uniform sampling instants is indicated as invalid and digital data generated by the observation ADC at uniform sampling instants is indicated as valid. The digital data indicated as invalid may be discarded and the digital data indicated as valid is used for calibration of the transmit path or the receive path.