Asynchronous Harmonic-Mixing Digitizers for Wider-Bandwidth Measurement
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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 sub-signals, each containing the entire frequency spectrum, which are then processed by digitizers operating at lower sample rates, allowing for effective digitization of higher frequency components and improved Signal-to-Noise Ratio (SNR) through constructive and destructive phasing of sub-bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If synchronous time-interleaving is used to achieve higher sample rate, then the effective sample rate is improved, but the analog bandwidth requirement increases leading to higher system complexity
Solution Approach 1:
The patent divides the high-speed sampling task into multiple parallel ADC channels operating at lower individual sample rates. Each ADC channel processes a portion of the frequency spectrum, and the results are combined through digital signal processing to achieve the equivalent of a higher sample rate without requiring any single ADC to operate at the full high speed
Solution Approach 2:
The patent transforms the sampling problem from the time domain to the frequency domain by using frequency-domain interleaving. Instead of sampling at high rates in time, the system uses multiple ADCs operating at lower rates with different frequency responses, then combines them in the frequency domain to achieve high effective bandwidth and sample rate
2Speed
If the ADC sample rate is lowered to satisfy Nyquist theorem, then the ADC can operate at lower rates, but more ADC channels are needed increasing system complexity
Solution Approach 1:
The patent merges multiple ADC channels with different frequency responses into a unified high-bandwidth system. By combining the frequency responses of multiple lower-rate ADCs through digital processing, the system achieves the equivalent performance of a single high-rate ADC without the complexity of driving and synchronizing many individual channels
3Speed
If sub-bands are downconverted to lower frequency ranges, then the bandwidth requirement for ADC is reduced, but noise penalty increases due to routing signal energy to only one ADC channel
Solution Approach 1:
The patent makes each ADC channel process the entire frequency spectrum rather than assigning specific frequency sub-bands to specific ADCs. Each ADC channel is designed to handle all frequencies but operates at a lower effective rate, allowing all channels to contribute to the measurement of any given signal component, thereby maximizing signal energy capture and minimizing noise penalty
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.