Frequency-Interleaved Signal Generator for High-Bandwidth Waveforms
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Solution Overview
Problem
Conventional time-interleaved D/A converters for high-speed arbitrary waveform generators face issues such as waveform distortion, reduced signal amplitude, and difficulty in correcting mismatch characteristics due to the use of Return to Zero (RZ) waveforms and zero-order hold time limitations.
Innovation Solution
A signal generator employing frequency interleaving with N D/A converters, digital signal processing, and frequency mixers to generate sub-band waveform data, using local signals to frequency-shift and combine signals, reducing the required performance of each D/A converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If time-interleaved method with multiple D/A converters is used to extend signal bandwidth, then signal bandwidth is improved, but waveform distortion and mismatch characteristics occur due to RZ waveform requirements
Solution Approach 1:
The signal bandwidth extension is achieved by segmenting the D/A conversion process into multiple parallel channels, each handling a portion of the frequency spectrum through frequency down-conversion. This segmentation allows each D/A converter to operate at lower speeds while collectively achieving high-speed output through the frequency interleaving combination.
Solution Approach 2:
The invention changes the operating parameters of the D/A converters by down-converting the frequency of the output signals from high-frequency carriers to lower baseband or intermediate frequencies before D/A conversion. This parameter change allows standard D/A converters to achieve high-speed performance when combined through frequency interleaving.
2Speed
If zero-order hold time is reduced to TS/2 to improve bandwidth, then signal bandwidth is improved, but signal amplitude is reduced and waveform distortion increases
Solution Approach 1:
Instead of reducing hold time to improve bandwidth, the invention changes the frequency parameter of the output signals by down-converting them to lower frequencies. This allows the D/A converters to maintain longer hold times (TS rather than TS/2) while still achieving high effective bandwidth through the frequency interleaving combination of multiple channels.
3Speed
If multiple D/A converters operate at high sampling frequency to achieve high-speed waveform generation, then signal bandwidth is improved, but device complexity and performance requirements increase
Solution Approach 1:
The invention changes the frequency parameter of the signals by down-converting high-frequency carrier signals to lower baseband or intermediate frequencies before D/A conversion. This parameter change allows the use of lower-performance D/A converters with lower sampling frequency requirements, reducing device complexity while maintaining high-speed output capability through frequency interleaving.
Data Source
AI summary
N (N≥2) D/A converters convert respective input data at a sampling frequency FS. A digital signal processing unit generates N items of sub-band waveform data. Each of N items of sub-band waveform data is generated by frequency-shifting corresponding one of N sub-band components included in digital waveform data that represents the analog output signal, such that each sub-band waveform data has its maximum frequency below FS/2. A local signal generating circuit generates N local signals having different frequencies.