Radar Waveform Frequency Notching via Digital Signal Processing
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Solution Overview
Problem
Radar systems face interference and operational limitations due to frequency band restrictions, leading to challenges in maintaining signal quality and avoiding interference with other spectrum users, especially at lower frequencies.
Innovation Solution
A notched chirp signal generation method using a programmable look-up table to identify forbidden frequency bands, allowing for dynamic frequency notching during the LFM chirp waveform generation process, which preserves phase linearity and avoids external signal switching, enabling the radar system to adaptively adjust its transmission to avoid restricted frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If radar systems transmit in lower frequency bands to achieve longer range operation and foliage/ground penetration, then the radar system can operate over longer ranges and penetrate obstacles, but the radar system encounters interference from other spectrum users and regulatory restrictions
Solution Approach 1:
The patent extracts and removes the harmful frequency components from the radar signal by implementing spectral notching. The notching process selectively eliminates specific frequency bands that cause interference or violate regulatory limits, while preserving the beneficial low-frequency components for range operation and penetration capability.
Solution Approach 2:
The patent applies local quality modification by creating localized notches in specific frequency regions of the otherwise continuous low-frequency spectrum. This allows the radar to maintain low-frequency operation for range and penetration while selectively avoiding problematic frequency bands through localized spectral modifications.
2Measurement precision
If radar systems use larger bandwidths to achieve finer signal resolutions, then the radar system can achieve better range resolution, but the radar system faces increased competition for frequency bands and regulatory restrictions
Solution Approach 1:
The patent extracts and removes harmful frequency components that cause interference while preserving the overall large bandwidth structure. By applying notches to specific problematic frequency regions within the broadband signal, the system maintains fine range resolution from the large bandwidth while eliminating interference from restricted frequency bands.
Solution Approach 2:
The patent modifies local frequency regions by creating notches in specific bandwidth regions that cause interference, while preserving the rest of the broadband spectrum. This localized spectral shaping maintains the benefits of large bandwidth for fine resolution while avoiding harmful frequency bands.
3Reliability
If radar systems are restricted from transmitting in specific spectral regions by regulatory limits, then other spectrum users are protected from interference, but the radar system's operational flexibility is limited
Solution Approach 1:
The patent implements dynamic spectral notching where the notched frequency regions can be programmatically adjusted based on regulatory requirements and operational conditions. This dynamic approach allows the radar to adapt its frequency usage in real-time, maintaining regulatory compliance while maximizing operational flexibility by shifting energy to available frequency regions.
Solution Approach 2:
The patent changes the spectral parameters of the radar signal by applying notches in programmable frequency regions. This allows the system to adapt to different regulatory environments and operational scenarios by modifying the frequency domain characteristics of the transmitted signal, thereby maintaining both compliance and flexibility.
4Object-affected harmful factors
If radar systems apply traditional frequency notching methods using external signal switching, then restricted frequencies can be blocked, but phase linearity is disrupted and signal quality deteriorates
Solution Approach 1:
The patent replaces mechanical external signal switching with a digital signal processing approach implemented within the waveform generator. By using digital notching techniques that modify the phase and amplitude of frequency components through computational methods rather than physical switching, the system achieves interference reduction while preserving phase linearity and signal quality.
Solution Approach 2:
The patent introduces an intermediate digital processing stage within the waveform generator that mediates between the baseband signal and the RF output. This intermediate digital notching process selectively removes harmful frequency components while maintaining the overall phase coherence of the signal, avoiding the phase disruptions caused by external switching methods.
Data Source
AI summary
The various technologies presented herein relate to incorporating one or more notches into a radar spectrum, whereby the notches relate to one or more frequencies for which no radar transmission is to occur. An instantaneous frequency is monitored and if the frequency is determined to be of a restricted frequency, then a radar signal can be modified. Modification can include replacing the signal with a signal having a different instantaneous amplitude, a different instantaneous phase, etc. The modification can occur in a WFS prior to a DAC, as well as prior to a sin ROM component and/or a cos ROM component. Further, the notch can be dithered to enable formation of a deep notch. The notch can also undergo signal transitioning to enable formation of a deep notch. The restricted frequencies can be stored in a LUT against which an instantaneous frequency can be compared.