Bandpass Filtered RF A/D Conversion Using Low-Rate Undersampling
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Solution Overview
Problem
Existing AD conversion techniques require high-cost, high-performance AD converters and circuits to handle high sampling rates, leading to inefficiencies and limitations in sampling broadband signals, particularly due to the need for multiple AD converters and complex digital signal processing.
Innovation Solution
An AD converting device with a plurality of bandpass filters and a low sampling rate AD converter that selects one bandpass filter to sample signal components, setting the sampling frequency to avoid integral multiples of the Nyquist frequency, allowing efficient undersampling and reducing the need for high-performance processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high sampling rate AD converter is used to digitize high frequency signals, then sampling accuracy is improved, but cost and power consumption increase
Solution Approach 1:
The frequency band of the input signal is divided into multiple sub-bands using bandpass filters. Each sub-band is then processed by a single low sampling rate AD converter through undersampling, eliminating the need for a single high sampling rate converter while maintaining overall sampling accuracy across the entire frequency range.
Solution Approach 2:
The sampling frequency is changed from a high uniform rate to a lower rate that is specifically tailored for undersampling each filtered sub-band. By adjusting the sampling frequency parameter to be lower than the signal frequency but satisfying the undersampling condition, the system achieves accurate digitization without requiring expensive high-speed converters.
2Measurement precision
If a high sampling rate AD converter is used, then sampling accuracy is improved, but power consumption increases
Solution Approach 1:
The frequency band is segmented into multiple sub-bands, allowing a low power consumption AD converter to process each sub-band separately through undersampling. This segmentation enables the use of energy-efficient low sampling rate converters instead of a single high power consumption high sampling rate converter.
Solution Approach 2:
The sampling frequency parameter is changed from a high value to a lower value suitable for undersampling. This parameter change directly reduces the power consumption of the AD converter while maintaining sampling accuracy through the combination of bandpass filtering and undersampling techniques.
3Measurement precision
If a high sampling rate AD converter is used, then sampling accuracy is improved, but digital data processing complexity increases
Solution Approach 1:
The frequency spectrum is segmented into multiple non-overlapping sub-bands using bandpass filters. Each sub-band is converted to digital form separately at a lower sampling rate, producing fewer digital samples per channel. This segmentation reduces the total amount of digital data that needs to be processed compared to a single high sampling rate converter, thereby reducing processing complexity.
4Measurement precision
If undersampling is performed without bandpass filtering, then multiple aliases cannot be distinguished
Solution Approach 1:
The frequency band is segmented into multiple distinct sub-bands using bandpass filters before undersampling. This segmentation ensures that each sub-band contains signals from a specific frequency range, allowing the undersampled aliases to be clearly distinguished and assigned to their respective original frequency bands, thereby maintaining signal distinction accuracy.
Data Source
AI summary
A wireless communication device converts a signal component, which has one of distributed frequency bands in an analog RF signal and passes through one of a plurality of bandpass filters, into digital data with an AD converter that carries out undersampling. A sampling frequency of the AD converter is set so that frequencies which are integral multiples of a Nyquist frequency based on the sampling frequency do not fall within frequency bands of signal components which are of the RF signal and are to pass through the respective plurality of bandpass filters.