Spectral Stitching for Wider-Band Vector Signal Generation
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Solution Overview
Problem
Current methods for increasing instantaneous bandwidth in RF vector signal analyzers and generators, such as time-interleaving and quadrature mixing, face limitations including inaccuracies, scalability issues, and image rejection, which hinder achieving larger bandwidths without sacrificing dynamic range.
Innovation Solution
The spectral stitching method processes digital signals through multiple parallel processing paths, each handling a frequency band with a specific center frequency and overlap region, phase-locked and time-synchronized, to create an aggregate frequency band, using frequency-shifting, filtering, and gain/phase adjustments, and combining these signals to achieve higher bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If time-interleaving is used to increase bandwidth, then instantaneous bandwidth is improved, but measurement precision and dynamic range deteriorate due to inaccuracies in time alignment and magnitude/phase differences between ADCs
Solution Approach 1:
The patent divides the frequency band into multiple non-overlapping sub-bands, with each ADC dedicated to a specific sub-band. This segmentation eliminates the need for time-interleaving and associated correction algorithms, achieving over 12 bits of dynamic range without DSP correction while maintaining high instantaneous bandwidth through parallel processing of multiple frequency sub-bands
Solution Approach 2:
The patent transitions from time-domain interleaving to frequency-domain division by assigning different frequency sub-bands to different ADCs. This dimensional change from time to frequency allows simultaneous capture of multiple sub-bands without the alignment errors that plague time-interleaved systems
2Speed
If quadrature mixing is used to increase bandwidth, then instantaneous bandwidth is improved, but device complexity increases and scalability is limited to two converters
Solution Approach 1:
The patent segments the frequency spectrum into multiple independent sub-bands, with each sub-band processed by a dedicated ADC. This approach allows linear scalability to N converters without the complexity of quadrature mixing, as each ADC operates independently on its assigned sub-band with simple bandpass filtering and downsampling
Solution Approach 2:
The patent applies partial processing to each sub-band, where each ADC only processes its assigned frequency portion rather than the entire bandwidth. This partial action simplifies each converter's requirements while achieving overall high bandwidth through parallel operation of multiple simplified converters
Data Source
AI summary
Embodiments are described of devices and methods for processing a signal using a plurality of vector signal generators (VSGs). A digital signal may be provided to a plurality of signal paths, each of which may process a respective frequency band of the signal, the respective frequency bands having regions of overlap. The gain and phase of each signal path may be adjusted such that continuity of phase and magnitude are preserved through the regions of overlap. The adjustment of gain and phase may be accomplished by a complex multiply with a complex calibration constant. The calibration constant may be determined for each signal path by comparing the gain and phase of one or more calibration tones generated within each region of overlap. Each signal path may comprise a VSG to convert the respective signal to an analog signal, which may be combined to obtain a composite signal.