A Self-Matched Passive Single Varactor Loaded Transmission Line for Efficient Harmonic Generation in Backscatter IoT Devices

This paper presents a self-matched passive harmonic generator circuit for backscatter IoT devices, utilizing a single varactor-loaded transmission line. The proposed design is implemented on an FR4 PCB with only one varactor, significantly simplifying the circuit, reducing its size, and lowering costs. The parallel configuration of the circuit enables precise control over the generated output power, while the self-matched nature of the design eliminates the need for additional passive matching networks, further enhancing its simplicity and efficiency. Results demonstrate a significant improvement in output power at the second harmonic, achieving a maximum of -8.5 dBm at 4 GHz with an input power of 0 dBm at 2 GHz, outperforming existing designs. The compact, energy-efficient, and low-cost nature of the proposed circuit makes it an ideal solution for batteryless IoT applications.