FMCW Radar Active Target Detection via Discrete Frequency Tag
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Solution Overview
Problem
Existing short-range radars using frequency modulated carrier waves (FMCW) are not compatible with active target detection systems, as they cannot distinguish between active and passive targets, and pulsed Doppler systems are unsuitable for very short-range detection due to difficulties in generating short pulses.
Innovation Solution
A radar and radio frequency tag system that includes an interrogator radar and a tag, where the tag transmits a series of discrete fixed frequencies, allowing the interrogator to switch between conventional FMCW mode for passive object detection and an active target detection mode using a single mixer and signal generator, enabling identification of active targets without hardware alterations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FMCW radar is used for short range detection, then detection capability is improved, but ability to distinguish active targets is lost
Solution Approach 1:
The radar system dynamically switches between FMCW mode for passive target detection and a second mode for active target detection. The signal generator and mixer are reconfigured to transmit a sequence of discrete frequencies and receive corresponding responses, enabling the system to adapt its operation mode based on detection requirements without hardware modification.
Solution Approach 2:
In the second mode, the radar transmits a periodic sequence of discrete frequencies and waits for corresponding responses from active targets. This periodic frequency switching creates a distinguishable signal pattern that allows the radar to identify active targets by detecting which frequencies are reflected back, thereby resolving the contradiction between detection capability and active target distinction.
2Adaptability or versatility
If pulsed Doppler radar is used for active target detection, then active target identification is improved, but suitability for very short range detection deteriorates
Solution Approach 1:
The radar system is designed to perform multiple functions using the same hardware platform. It can operate in FMCW mode for passive target detection and ranging, and switch to a second mode for active target detection using discrete frequency sequences. This multi-functionality allows the system to achieve both very short range detection capability and active target identification without requiring separate systems.
3Measurement precision
If broader intermediate frequency band is used to avoid confusion with non-active objects, then active target detection accuracy is improved, but system complexity increases
Solution Approach 1:
Instead of using a broadly increased intermediate frequency band for the entire system, the invention applies local quality by using specific discrete frequencies for active target detection that are selected from the existing FMCW frequency spectrum. The radar identifies active targets by detecting which specific frequencies are reflected back, allowing accurate detection without requiring a significantly broader overall frequency band and thus avoiding excessive system complexity.
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
Enables existing FMCW radar systems to identify active targets within short ranges, improving detection capabilities without modifying hardware, and allows for accurate ranging and identification of objects using a single mixer and signal generator.
Implementation Method 1
a carrier wave is rapidly modulated by the transmitting radar. Energy reflects off objects in the field of view and a portion of this received by the radar is mixed with the transmitted carrier signal.
Implementation Method 2
Energy reflects off objects in the field of view and a portion of this received by the radar is mixed with the transmitted carrier signal. The frequency difference between transmitted and received signals (the beat frequency/intermediate frequency) is used to measure distance to the object(s).
Implementation Method 3
the tag comprises a transmitter through which it is adapted to transmit a binary code through transmission of a series of different discrete fixed frequencies selected from a set of discrete fixed frequencies
Implementation Method 4
The frequency difference between transmitted and received signals (the beat frequency/intermediate frequency) is used to measure distance to the object(s).
Data Source
AI summary
A frequency modulated carrier wave (FMCW) radar system can identify active targets. The system includes an interrogator radar and radio frequency tag. The tag includes a transmitter adapted to transmit a binary code through transmission of a series of different discrete fixed frequencies selected from a set of more than two discrete fixed frequencies.The interrogator radar is configured to be switchably operable between a first mode and a second mode. In the first mode the interrogator radar generates and transmits a FMCW signal in order to identify the presence of passive objects within its field of regard. In the second mode the interrogator radar transmits a relatively fixed frequency signal compared with the FMCW signal, and mixes the relatively fixed frequency signal with the series of discrete fixed frequencies received from the tag to identify the binary code.