Asynchronous Harmonic-Mixing Digitizer for Wideband Signal Capture
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Solution Overview
Problem
Conventional test and measurement instruments with asynchronous time-interleaved digitizers face limitations in bandwidth due to analog to digital converter (ADC) constraints, leading to increased complexity and noise penalties when digitizing high-frequency signals.
Innovation Solution
The use of harmonic mixing to split input signals into multiple paths, allowing all ADC channels to digitize frequency components, thereby avoiding noise penalties and improving Signal-to-Noise Ratio (SNR) by ensuring all bands of the input signal are processed through multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If synchronous time-interleaved digitization is used to achieve higher sample rates, then the effective sample rate is improved, but the system complexity and cost increase due to multiple ADCs and track and hold amplifiers
Solution Approach 1:
The input signal bandwidth is segmented into multiple sub-bands, with each sub-band processed by a separate ADC operating at a lower sample rate. This segmentation allows the system to achieve high effective bandwidth without requiring high sample rates from individual ADCs, thereby reducing complexity while maintaining performance.
Solution Approach 2:
The patent transitions from the time domain (synchronous time-interleaving) to the frequency domain (asynchronous frequency-interleaved) approach. By changing the dimension of operation from temporal to spectral, the system achieves high bandwidth utilization without the complexity of synchronized timing and track-and-hold circuits.
2Reliability
If the ADC sample rate is lowered to satisfy the Nyquist sampling theorem, then the ADC can operate within its bandwidth limits, but many time-interleaved ADC channels are needed to achieve the desired performance
Solution Approach 1:
Each ADC channel is designed to process multiple frequency sub-bands simultaneously through asynchronous sampling. This multi-functionality allows fewer ADC channels to achieve the same effective bandwidth coverage, reducing the total number of channels needed while maintaining sampling accuracy across the entire bandwidth.
3Speed
If sub-bands of an input signal are downconverted to a frequency range for lower sample rate ADC, then the ADC sample rate requirement is reduced, but the Signal-to-Noise Ratio is degraded due to noise penalty
Solution Approach 1:
Multiple asynchronously sampled sub-band signals are merged in the frequency domain to reconstruct the full-bandwidth signal. This combining process integrates the signal energy from all ADC channels while averaging out the noise contributions, thereby recovering the Signal-to-Noise Ratio that would be lost in individual sub-band processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables effective digitization of high-frequency signals by distributing the signal across multiple channels, reducing noise and increasing bandwidth without the need for high-sample-rate ADCs, thus improving the overall performance and reducing system complexity.
Implementation Method 1
A harmonic mixer is configured to mix the split signal with the harmonic signal to generate a mixed signal
Data Source
AI summary
A test and measurement instrument including a splitter configured to split an input signal having a particular bandwidth into a plurality of split signals, each split signal including substantially the entire bandwidth of the input signal; a plurality of harmonic mixers, each harmonic mixer configured to mix an associated split signal of the plurality of split signals with an associated harmonic signal to generate an associated mixed signal; and a plurality of digitizers, each digitizer configured to digitize a mixed signal of an associated harmonic mixer of the plurality of harmonic mixers. A first-order harmonic of at least one harmonic signal associated with the harmonic mixers is different from an effective sample rate of at least one of the digitizers.