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Experimental evaluation of harmonic tag operation in the presence of multiple transmitters

Birnie, T. (2022) Experimental evaluation of harmonic tag operation in the presence of multiple transmitters.

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Abstract:This report presents the results of an experimental study evaluating a mathematical model of harmonic tags used to create a nonlinear response in harmonic radar systems. Harmonic radar is a type of nonlinear radar. Instead of scanning on the transmit frequency for a return signal, with nonlinear radar the return signal is expected on another frequency. This typically requires a nonlinear element (active or passive). Harmonic radar uses a passive tag with a nonlinear element like a diode to create harmonics. Often the second harmonic is used since it has the most power. However, the harmonic return signal is still much weaker compared to the fundamental frequency. This results in a weak return signal which significantly limits the operational range of harmonic radar systems. Conventionally, increased transmit power, low sensitivity receivers, as well as high gain transmit and receive antennas are used to compensate. Recently, an alternative has been proposed that uses multiple lower power transmitters instead. The feasibility of this approach depends on the correctness of a mathematical model describing the harmonic tags that the multiple transmitter approach relies on. However, this mathematical model has not been experimentally verified yet. In this report, measurements with two transmitters are performed and compared against theoretical predictions based on the simulation results using the mathematical model. The results indicate that the mathematical model describes the behaviour of harmonic tags well in the entire input power range. The primary limitation of the model is that the power of the harmonic signal tends to be overestimated compared to the measurements. This leads to optimistic range estimations.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering BSc (56953)
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