Receiver Synchronization via Digital Filter Calibration
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Solution Overview
Problem
Existing signal processing systems for synchronizing multiple receivers lack the necessary precision in achieving identical frequency responses across all channels, leading to suboptimal performance in applications requiring high synchronization accuracy.
Innovation Solution
A computer-implemented method that calibrates receiver channels by designating one as a master and others as slaves, computing relative frequency responses, and implementing digital filters to compensate for amplitude and phase deviations, along with adjusting sample clocks and numerically controlled oscillators to achieve synchronized operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing synchronization tools are used to share LO signals and reference clocks between VSA channels, then basic phase-coherent operation is achieved, but the degree of synchronization is insufficient for high-precision applications
Solution Approach 1:
The patent performs preliminary calibration actions before actual signal processing. A calibration signal is injected into each receiver channel, and the system measures and stores the frequency response characteristics of each channel in advance. This preliminary characterization enables subsequent correction of synchronization errors, achieving high-precision frequency response matching across all channels.
Solution Approach 2:
The patent changes the parameters of digitally applied filters based on measured frequency response characteristics. By analyzing the calibration data and adjusting filter parameters (coefficients, orders, and characteristics), the system compensates for variations in receiver channels, transforming the frequency responses to be substantially identical across all channels.
2Device complexity
If multiple receiver channels operate independently without calibration, then device complexity is reduced, but frequency response uniformity and phase alignment deteriorate
Solution Approach 1:
The patent introduces a central controller as an intermediary that coordinates the calibration process across all receiver channels. This controller manages signal injection, collects frequency response measurements from each channel, computes correction parameters, and distributes filter configurations. This intermediary approach simplifies the overall system architecture while achieving precise frequency response uniformity through centralized coordination.
3Manufacturing precision
If digital filters are applied to compensate for frequency response variations, then frequency response uniformity is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent applies partial correction by focusing digital filter design on the dominant frequency response variations rather than attempting to correct all possible deviations. The calibration process identifies and corrects the most significant parameters affecting frequency response uniformity, achieving sufficient precision without requiring excessively complex filter designs that would overwhelm the system.
Data Source
AI summary
A system and method for synchronizing a plurality of receivers. A tone from a signal generator is swept over a frequency band. A power splitter splits the tone into a plurality of resultant tones that are supplied to the respective receivers. For each receiver, a relative frequency response (including amplitude and phase responses) is measured between the receiver and a master receiver. A linear approximation to the phase response is computed. A digital filter is custom designed for the receiver to compensate for non-uniformity of the amplitude response and for deviations of the phase from the linear approximation. After applying the digital filter, further adjustments are made to remove the time delay corresponding to the linear approximation, e.g., by appropriately configuring a fractional resampler, by adjusting a numerically-controlled oscillator, and/or, by adjusting sample clock phase.