Bandpass Sampling Receiver With Analog Interpolation Filtering
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Solution Overview
Problem
Current RF receiver architectures are ineffective in efficiently sampling signals across a wide frequency range with varying bandwidths, particularly in applications requiring large degrees of reconfigurability, such as electronic intelligence and multi-mode communications, due to limitations in tuning range and instantaneous bandwidth.
Innovation Solution
The implementation of a direct RF bandpass sampling receiver using analog interpolation filters decouples the quantization clock from the RF sampling clock, allowing for a tunable bandpass filter and sample clock, and subsequent slower rate quantization, enabling coverage of extremely large RF ranges from 2 GHz to over 20 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide frequency range is covered with a single receiver architecture, then the frequency coverage is improved, but the instantaneous bandwidth and tuning range are limited
Solution Approach 1:
The receiver is divided into multiple parallel superheterodyne channels, each tuned to a different intermediate frequency (IF). The RF input signal is distributed to multiple mixers, each mixing with a different local oscillator frequency to produce signals at different IFs. A bank of IF filters then selects the appropriate channel, effectively providing wide frequency coverage through parallel processing paths.
Solution Approach 2:
The patent introduces an additional frequency dimension by using multiple intermediate frequencies. Instead of trying to tune a single channel across a wide RF range, the system maps different RF frequency bands to different IF bands, creating a multi-dimensional frequency space that allows simultaneous wide coverage and precise filtering.
2Adaptability or versatility
If the sampling rate is increased to cover wider bandwidths, then the frequency range coverage is improved, but the quantization clock coupling limits the final analog bandwidth
Solution Approach 1:
The sampling process is segmented into two independent stages: a high-speed non-quantizing RF sampling stage and a slower quantization stage. The first sampler operates at a high rate to capture wide bandwidth signals without quantization, while a second sampler performs quantization at a lower rate on the already-sampled signal, allowing the final analog bandwidth to be narrower than the initial sampling bandwidth.
Solution Approach 2:
A decimation filter is introduced as an intermediary between the high-speed non-quantizing sampler and the slower quantizing sampler. This filter reduces the sampling rate while preserving the signal content, allowing the quantization clock to be decoupled from the RF sampling clock and enabling the final analog bandwidth to be much narrower than the initial sampling bandwidth.
3Ease of operation
If a fixed architecture is used for simplicity, then the device complexity is reduced, but the reconfigurability for different signal types is limited
Solution Approach 1:
The receiver architecture is made dynamic and reconfigurable through the use of tunable local oscillators and selectable IF filter banks. Each channel can be independently configured to receive different signal types and frequency ranges. The system can be reconfigured by changing the LO frequencies and selecting different IF filter characteristics, allowing adaptation to various communication standards and signal formats without changing the fundamental architecture.
Data Source
AI summary
Reconfigurable direct radio frequency (RF) bandpass sampling receivers are disclosed that utilize analog interpolation filters to improve performance. The addition of the analog interpolation filter to the bandpass sampling receiver allows the quantization clock to be de-coupled from the RF sampling clock. As such, the quantization can be performed at a much slower rate than the initial RF sampling allowing the final analog bandwidth to be much narrower than the bandwidth of the first stage filter located before the high-speed sampler. The combination of a tunable bandpass filter, tunable bandpass sample clock and analog interpolation filter followed by a further stage of sampling and quantization at a slower rate than the bandpass sample clocking, therefore, provides significant advantageous by de-coupling the quantization sample rate from the high-speed sample rate. If desired, the analog interpolation filter may also be tunable. Other variations and implementations are also described.