Radar Transmit Bandwidth Augmentation With LO Leakage Correction
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Solution Overview
Problem
Conventional radar systems are limited by the bandwidth of digital-to-analog converters (DACs), which restrict the resolution of radar signals, and LO leakage across transmit channels introduces amplitude and phase distortions in combined RF signals.
Innovation Solution
Employing multiple lower sampling rate DACs and addressing LO leakage through phase adjustments, feedforward loops, and selective LO frequency selection to combine RF signals with constant amplitude and phase, enabling a very high instantaneous bandwidth (IBW) radar signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single high-performance DAC is used to achieve high instantaneous bandwidth, then the radar signal resolution is improved, but the system cost increases significantly
Solution Approach 1:
The patent divides the single high-performance DAC into multiple lower-performance DACs operating in parallel. Each DAC generates a portion of the overall radar signal spectrum, and these signals are later combined through frequency multiplication and mixing. This segmentation allows the system to achieve the same high instantaneous bandwidth and resolution as a single expensive DAC would provide, but using multiple cheaper, lower-sampling-rate DACs that are more readily available and cost-effective.
2Measurement precision
If multiple transmit channels are combined to increase bandwidth, then the instantaneous bandwidth is augmented, but LO leakage introduces amplitude and phase distortions
Solution Approach 1:
The patent converts the harmful LO leakage effect into a beneficial measurement tool. By deliberately measuring the LO leakage present in each transmit channel, the system computes correction factors that characterize the distortion. These measured leakage patterns are then used to calculate and apply compensation signals that pre-distort the transmitted waveforms, thereby canceling out the expected LO leakage effects in the final combined signal and achieving clean amplitude and phase characteristics.
Solution Approach 2:
The patent performs preliminary measurement and computation of LO leakage characteristics before the actual radar signal transmission. The system measures the LO leakage from each transmit channel, computes the necessary correction factors, and determines the appropriate compensation signals in advance. This preliminary action ensures that when the full-radar signals are transmitted and combined, the LO leakage distortions have already been accounted for and compensated, resulting in a clean combined signal with accurate amplitude and phase.
3Ease of manufacture
If lower sampling rate DACs are used, then the system cost is reduced, but the achievable bandwidth is limited
Solution Approach 1:
The patent changes the frequency domain parameters of the signals generated by multiple low-sampling-rate DACs through frequency multiplication and mixing operations. Each DAC operates at a manageable sampling rate to produce baseband or intermediate frequency signals. These signals then undergo frequency transformation where their spectral content is shifted and expanded into higher frequency ranges. The combined effect of multiple DACs, each contributing a portion of the spectrum after frequency transformation, results in a composite signal with very high instantaneous bandwidth that would be impossible to achieve with any single low-sampling-rate DAC.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The radar system generates high-resolution data with a very high IBW using relatively inexpensive DACs, overcoming conventional limitations and achieving improved resolution and signal quality.
Implementation Method 1
The mixer receives the IF analog signal and mixes the IF analog signal with a local oscillator (LO), thereby upconverting the IF analog signal to a radio frequency (RF) analog signal
Data Source
AI summary
Various technologies pertaining to forming a very high instantaneous bandwidth (IBW) radar signal based upon several radio frequency (RF) signals that have sub-bands of the frequency band of the radar signal are described herein. A radar system is configured to address local oscillator leakage across multiple transmit channels of the radar system, such that the radar signal has a relatively constant or other desired amplitude and phase across frequencies of the radar signal. In addition, the radar system is configured to compute a correction signal that pre-distorts each of the sub-frequency channels such that upon combining enables the generation of desired amplitude and phase response across a transmitted pulse.