Sample and Hold Circuit for Pulse Radar Signal Integration
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Solution Overview
Problem
Pulse radar systems face issues with signal-to-noise ratio deterioration, charge loss in integrating capacitors, and 1/f noise due to continuous integration and unbalanced signal mixers, which result in noise integration and amplification.
Innovation Solution
Incorporating a sample and hold circuit with a switch and hold capacitor in the signal integration means, controlled by a sampling clock with adjustable delay, to sample and hold the intermediate frequency signal, decoupling the amplifier from the signal mixer during intervals between sampling pulses and preventing disturbance integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RC integration or low-pass filtering means are used for signal integration, then the intermediate frequency signal can be integrated and amplified, but the signal-to-noise ratio of the IF signal is deteriorated due to continuous integration
Solution Approach 1:
The patent applies periodic sampling action instead of continuous integration. The sample and hold circuit samples the IF signal at discrete time intervals synchronized with the sampling clock frequency, converting continuous integration into periodic sampling. This prevents noise integration between sampling moments while maintaining signal integration capability at sampled instants, thereby improving signal-to-noise ratio.
Solution Approach 2:
The patent extracts only the necessary signal information at specific sampling moments rather than continuously integrating all incoming signals. By using the sample and hold circuit to capture and hold signal values only at synchronized sampling instants, the system extracts useful signal components while excluding noise that would otherwise be integrated during non-sampling periods.
2Reliability
If RC integration means are used, then signal integration is achieved, but electric charge stored in the integrating capacitor is lost due to conduction of the mixer diodes in the interval time between IF pulses
Solution Approach 1:
The sample and hold circuit operates periodically, closing the switch only during sampling intervals and keeping it open during interval times. This periodic switching prevents continuous charge leakage through the mixer diodes while maintaining charge storage capability during active sampling periods, eliminating the charge loss problem associated with continuous RC integration.
Solution Approach 2:
The switch in the sample and hold circuit acts as an intermediary between the IF signal source and the hold capacitor. By controlling the switch state based on sampling clock synchronization, it mediates charge transfer to the capacitor only when needed and isolates the capacitor from leakage paths during interval times, preventing charge loss.
3Reliability
If RC integration or low-pass filtering means are used, then the intermediate frequency signal is integrated, but 1/f noise produced by the mixer diodes is applied through the integration to the IF amplifier
Solution Approach 1:
By replacing continuous RC integration with periodic sampling action, the system integrates signals only at discrete sampling moments rather than continuously. This periodic integration approach prevents the accumulation and amplification of 1/f noise that occurs with continuous integration, as noise components between sampling instants are not integrated into the output signal.
4Reliability
If unbalanced signal mixers are used, then signal mixing is achieved, but small signal portions appear at the output that act as noise and are integrated and amplified
Solution Approach 1:
The sample and hold circuit extracts only the synchronized signal components from the mixer output by sampling at precise moments when the desired IF signal is present. This extraction process separates useful signal information from unwanted noise portions generated by mixer unbalances, allowing the system to ignore noise components that would otherwise be integrated and amplified by continuous integration.
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
This solution enhances signal quality by preventing noise integration and maintaining signal integrity, thereby improving the accuracy of distance measurements in pulse radar systems.
Implementation Method 1
a sample and hold circuit having a switch (17) and a hold capacitor (18)
Implementation Method 2
a signal mixer for generating an intermediate frequency signal by mixing echo pulses reflected from the target with the sampling pulses
Data Source
AI summary
In a pulse radar system where received echo pulses are expanded in time by multiplication with sampling pulses and subsequent integration, the effect of disturbances on the integration is reduced by using a sample and hold circuit having a switch and a hold capacitor and wherein the switch is closed only when a sampling pulse is applied for the multiplication.