Subband Domain Code Division Multiplexing for Antenna Arrays
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Solution Overview
Problem
Conventional digital beamforming systems face challenges with high power consumption, size, and weight due to the need for multiple high-rate analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) in antenna arrays, limiting flexibility and increasing hardware complexity, especially when implementing code division multiplexing (CDM) in the time domain.
Innovation Solution
The system employs code division multiplexing in the subband domain, using a single ADC and DAC to aggregate signals from multiple antenna elements, performing circular convolutions in the frequency domain to demultiplex signals, and routing subband signals for beamforming, thereby reducing hardware complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple high-rate ADCs and DACs are used in antenna arrays for digital beamforming, then signal processing flexibility and beamforming performance are improved, but power consumption, size, and weight increase significantly
Solution Approach 1:
The patent combines multiple antenna element signals into a single aggregated signal path, allowing one ADC and one DAC to serve multiple antenna elements through code division multiplexing, thereby reducing the total number of converters and their associated power consumption
Solution Approach 2:
The patent transitions from time-domain code division multiplexing to subband-domain code division multiplexing, performing CDM operations in the frequency domain after FFT transformation. This dimensional change enables more efficient signal aggregation and reduces the sampling rate requirements for the ADC and DAC
2Adaptability or versatility
If multiple high-rate ADCs and DACs are used in antenna arrays, then digital beamforming capability is improved, but hardware complexity, size, and weight increase
Solution Approach 1:
The patent merges multiple signal paths into a single processing path by aggregating signals from multiple antenna elements, allowing shared use of one ADC, one DAC, and reduced digital processing complexity through subband-domain CDM
Solution Approach 2:
The patent replaces the mechanical/physical multiplication of hardware components (multiple ADCs and DACs) with a signal processing approach using CDM in the subband domain, achieving the same functional capability with fewer physical components
3Use of energy by moving object
If low-rate converters are used to reduce power consumption, then power consumption decreases, but flexibility in terms of supported frequency and bandwidth requirements decreases
Solution Approach 1:
The patent moves the CDM operation from the time domain to the subband (frequency) domain by performing FFT transformation first, then applying code division multiplexing in the frequency domain. This allows low-rate converters to maintain high flexibility because the subband processing preserves spectral information while reducing sampling rate requirements
Solution Approach 2:
The patent changes the operational domain parameter from time-domain sampling to subband-domain processing, transforming the signal through FFT and performing CDM operations on frequency-domain representations, thereby enabling low-rate conversion without sacrificing bandwidth flexibility
4Device complexity
If sub-array digital processing is used to reduce hardware complexity, then hardware complexity decreases, but scan range is restricted and beam performance in directivity and steerability is reduced
Solution Approach 1:
The patent performs code division multiplexing in the subband domain after FFT transformation rather than in the time domain, enabling full-array digital processing with reduced hardware complexity while maintaining complete scan range and beamforming performance through frequency-domain signal manipulation
Data Source
AI summary
System and method for efficient wideband code division multiplexing in subband domain include: aggregating L analog signals received from L antenna elements into a single aggregated signal, by using code division multiplexing with L code words, where L is an integer greater than 1; converting the single aggregated analog signal to a single aggregated digital signal, by a single analog-to-digital converter (ADC); channelizing the single aggregated digital signal into N subbands, where N is an integer greater than 1; performing circular convolutions of the N subbands with the L code words to demultiplex the channelized signal into L elements per subband; and routing each subband signal of the L elements to N beamforming circuits for performing beamforming on each of the N subbands.