Bandpass Sampling Receiver With Modulated Clock Zone Separation
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Solution Overview
Problem
Current receiver architectures for radio frequency (RF) signals face challenges in efficiently sampling wide frequency ranges with low distortion and interference, particularly in applications requiring reconfigurability, sensitivity, and coverage of large frequency spans, such as radar and communication systems, due to limitations in device capabilities, power consumption, size, weight, and cost.
Innovation Solution
Nyquist folded bandpass sampling receivers utilize wideband filters and modulated sampling clocks to alias multiple Nyquist zones together, allowing for the separation and identification of signals from different zones through frequency modulation, enabling efficient sampling across a wide bandwidth with a relatively slow ADC in sparse signal environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sub-Nyquist sampling schemes are used to reduce sampling rate, then device limitations and power consumption are reduced, but measurement precision and signal reconstruction accuracy deteriorate
Solution Approach 1:
The patent applies dynamics by making the sampling clock frequency time-varying rather than fixed. The sampling frequency is modulated according to a known modulation scheme (e.g., frequency modulation), which allows the system to operate at lower average sampling rates while maintaining signal reconstruction capability through the known temporal variations in sampling rate
Solution Approach 2:
The patent changes the sampling parameter from a fixed frequency to a time-varying frequency with known modulation characteristics. This parameter change enables the system to distinguish between different input signals even when they alias to the same frequency, because the time-varying sampling rate imprints unique temporal signatures on signals from different frequency bands
2Adaptability or versatility
If wideband filters are used to cover multiple Nyquist zones, then frequency range coverage is improved, but device complexity and size increase
Solution Approach 1:
The patent implements multi-functionality by using a single wideband filter to perform the function of multiple narrowband filters would otherwise be needed. This wideband filter covers multiple Nyquist zones simultaneously, allowing the system to receive and process signals across a wide frequency range without requiring multiple separate filter components
Solution Approach 2:
The patent merges multiple Nyquist zones into a single processing path by using a wideband filter that passes signals from multiple zones simultaneously. The time-varying sampling clock then processes all these zones together, combining what would traditionally require separate processing channels into a unified system
3Productivity
If multiple Nyquist zones are aliased together to increase sampling efficiency, then productivity is improved, but signal separation and identification become more difficult
Solution Approach 1:
The patent uses dynamic sampling rate modulation to encode information about which Nyquist zone each signal originates from. The time-varying sampling frequency creates unique temporal patterns in the aliased signals that allow digital signal processing to separate and identify signals from different zones even though they are folded into the same frequency range
Solution Approach 2:
The system uses feedback through digital signal processing that exploits the known modulation characteristics of the sampling clock. By comparing the received signals against the known time-varying sampling pattern, the system can extract and separate signals from different Nyquist zones that have been aliased together
Data Source
AI summary
Nyquist folded bandpass sampling receivers are disclosed that utilize wideband filters and modulated sampling clocks to identify received signals. In operation, multiple Nyquist zones are allowed to fold on top of each other during sampling. Because the RF sampling clock is modulated, separate frequency modulations can be induced within each Nyquist zone. The signals that are folded together from different Nyquist zones can then be identified and distinguished. In particular, when the Nyquist zones fold on top of each other, the different signals from different Nyquist zones can be separated and identified based on the fact that the added modulation is different for each Nyquist zone. Thus, by using one or more clock modulations to induce frequency modulations that are Nyquist zone dependent, multiple Nyquist zones can be aliased together while still allowing for signals from different Nyquist zones to be separated and identified. Other variations and implementations are also described.