Harmonic-Mixing Digitizer for Wideband Signal Sampling
Find Innovative SolutionsGenerate Solutions
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 wideband signals.
Innovation Solution
The implementation of harmonic mixing in ADC systems, where input signals are split and mixed with harmonic signals to digitize all frequency components across multiple channels, allowing for effective digitization of higher frequency components within the Nyquist bandwidth, thereby improving the signal-to-noise ratio.
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 and system complexity increases
Solution Approach 1:
The patent divides the wideband input signal into multiple frequency sub-bands using band-pass filters, with each sub-band processed by a separate ADC operating at a lower sample rate. This segmentation allows the system to achieve high effective sample rate through digital combination without requiring high-speed analog components.
Solution Approach 2:
The patent transitions from time-domain sampling to frequency-domain processing by filtering input signals into multiple frequency sub-bands. Each sub-band is then independently digitized and combined in the digital domain, effectively adding a frequency dimension to the sampling architecture.
2Productivity
If the number of ADC channels is increased to achieve desired performance, then the sample rate capability is improved, but the cost and complexity increase
Solution Approach 1:
The patent changes the operating parameters of ADC channels from requiring high sample rates to operating at lower, fixed sample rates. By adjusting the frequency sub-band allocation and filter characteristics, the system achieves high overall sample rate capability through multiple low-speed ADCs working in parallel.
3Speed
If sub-bands are downconverted to frequency range for lower sample rate ADC, then the ADC sample rate requirement is reduced, but the Signal-to-Noise Ratio degrades due to noise penalty
Solution Approach 1:
The patent combines the outputs of multiple ADCs in the digital domain after processing their respective frequency sub-bands. By coherently combining the digitized sub-bands, the system achieves the desired wideband signal representation while the noise from multiple ADCs averages out, maintaining or improving the overall Signal-to-Noise Ratio.
Data Source
Figure 1~3
Figure 4~7
Figure 8~10
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.