X-band upconverter and K-band downconverter for harmonic radar application
University of New Brunswick
The harmonic radar at UNB was developed to track the Colorado potato beetle over an extended range. To overcome the ground backscatter, harmonic radar is used where a fundamental signal is transmitted and the second harmonic signal is received and tracked. The nonlinear tag on the beetle will re-radiate a portion of the incident power at the second harmonic. The thesis objective is to design, fabricate, test and characterize two microwave frequency boards, one for upconversion which is the transmitter and the other for downconversion which is the receiver. The main objective of the upconversion board is to reduce the output harmonics transmitted and on the downconverter, to eliminate the fundamental signal leaking into the receiver. Most Software Defined Radios (SDR) cannot produce and detect signals beyond 4 GHz. The gap between the SDR's maximum frequencies and high frequency needed to activate the tag needs to be addressed. These boards act as a bridge between the higher microwave frequencies activating the tag and the SDR which work at lower frequencies. Microwave conversion boards which upconvert 2 GHz to 10.2 GHz on the transmit side and downconvert 20.4 GHz to 1.6 GHz on the receive side have been developed, tested and characterized in this work. The use of appropriate microstrip filters, Substrate Integrated Waveguides (SIW), diode limiters, mixers, amplifiers and VCO-PLLs are used to achieve the conversion while making sure that the output harmonics are kept at a minimum and the received fundamental is kept at a minimum.