Noise Augmented Radar Using 1-Bit ADC and Dithering
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Solution Overview
Problem
Current wideband radar systems face limitations in achieving high range resolution due to low signal reception efficiency, high transmission powers or long integration times required in impulse systems, and regulatory constraints on stepped frequency systems, as well as the lack of high-speed, high-resolution ADCs, which result in reduced signal-to-noise performance and increased complexity and cost.
Innovation Solution
A radar system that transmits a pseudo random noise signal, uses a low-resolution 1-bit ADC or comparator, and adds random noise to the received signal for dithering, averaging the signal in a circular buffer to improve SNR, and performs cross-correlation to generate a range profile, allowing for efficient detection of both strong and weak signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impulse radar systems are used to achieve wideband transmission, then high range resolution is obtained, but signal reception efficiency is low requiring high transmission powers or long integration times
Solution Approach 1:
The patent employs periodic transmission of pseudo-random noise signals at repeated time intervals, allowing the receiver to continuously sample and integrate returns over multiple periods. This periodic action accumulates signal energy while maintaining wideband characteristics, resolving the contradiction between achieving high range resolution and maintaining signal reception efficiency
Solution Approach 2:
The patent performs preliminary signal processing by continuously buffering and integrating received signals before final detection. The receiver prepares and accumulates returns over an integration time period, so when a target return is detected, the signal has already been enhanced through preliminary integration, improving reception efficiency without sacrificing range resolution
2Productivity
If stepped frequency radar is used to achieve wideband operation, then transmission efficiency is improved, but narrow band transmission at any point in time violates FCC regulations
Solution Approach 1:
The patent changes the frequency parameter by transmitting pseudo-random noise signals that occupy a wide frequency spectrum simultaneously rather than stepping through frequencies sequentially. This parameter change allows the system to achieve wideband operation in compliance with FCC regulations while maintaining transmission efficiency
Solution Approach 2:
The patent uses pseudo-random noise sequences that can be regenerated and correlated at the receiver. By transmitting a known pseudo-random sequence and copying it for correlation processing, the system achieves wideband coverage without narrowband constraints, complying with regulations while maintaining efficiency
3Measurement precision
If high bit resolution ADCs (>10 Gsps) are used to detect strong and weak signals, then digital quantisation noise is reduced, but no such ADCs currently exist and complexity increases
Solution Approach 1:
The patent applies partial dithering by adding random noise only to the least significant bit of the ADC output rather than to the full signal path. This partial action reduces digital quantisation noise effectively while avoiding the excessive complexity of high-bit-resolution ADCs, as the dithering technique allows lower-resolution ADCs to achieve equivalent performance
Solution Approach 2:
The patent substitutes hardware complexity (high-bit-resolution ADCs) with a software/digital signal processing technique (dithering and integration). Instead of using complex physical ADC hardware, the system uses simpler ADCs combined with digital noise addition and correlation processing to achieve the same measurement precision
4Device complexity
If under-sampling is used to digitize the signal, then hardware requirements are reduced, but signal to noise performance is reduced
Solution Approach 1:
The patent performs preliminary integration and buffering of under-sampled signals before final detection. By accumulating multiple under-sampled returns in a circular buffer and integrating them coherently, the system recovers signal energy and improves signal-to-noise performance, compensating for the initial degradation caused by under-sampling while maintaining reduced hardware requirements
5Speed
If single bit ADC is used to reduce complexity, then ADC speed increases, but output is only one bit requiring large cross correlation arrays
Solution Approach 1:
The patent applies partial dithering specifically to the least significant bit of the ADC output, which allows the single-bit ADC to operate at high speed while the added noise enables effective correlation processing. This partial action reduces the need for large cross-correlation arrays by improving the signal-to-noise ratio of the single-bit output, thereby reducing complexity while maintaining high ADC speed
Data Source
AI summary
A radar system comprises a transmitter that transmits a predetermined wideband signal, a digital receiver that records a returned signal using a one-bit ADC, a random noise source that is added to the transmitted or returned signal, a processing means where the received signal is distorted to compensate for the effect of the noise on the receiver. The predetermined wideband signal may be a pseudo random noise signal. The processing may include averaging prior to cross-correlation.