Two-Tone Suppressed Third-Order Intermodulation Transponder Based on Transmission-Line-Based Fourth-Order Filter Combined Matching Network

• Published in: IEEE access Vol. 12; pp. 43918 - 43923
• Main Authors: Moon, Dana, Kim, Jisu, Oh, Juntaek
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Attenuation; Bandpass filters; Cutoff frequency; Filter combined matching network; Harmonic analysis; harmonic radar; Impedance; Intermodulation; intermodulation transponder; Matched filters; Matching; Nonlinear response; Power harmonic filters; Resonant frequencies; Transmission lines; Transponders
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2024.3380161

This paper presents a <inline-formula> <tex-math notation="LaTeX">3^{rd} </tex-math></inline-formula>-order intermodulation transponder designed to achieve high suppression of fundamental two-tone signals simultaneously. In previous papers, a nonlinear response system combining matching and suppression has never been considered. The core innovation lies in the proposed output matching network, which effectively shifts the output impedance of the diode to the load impedance at the target intermodulation frequency of 2.3 GHz and to short at the fundamental frequencies of 2.4 and 2.5 GHz. It achieves a high conversion gain and provides a substantial isolation between a two-tone fundamental input port and an intermodulation output port through a sharp band-pass filtering characteristic. For validation, we fabricate and measure the proposed intermodulation transponder with dimensions of <inline-formula> <tex-math notation="LaTeX">72.5\times53 </tex-math></inline-formula> mm2. The measurement results demonstrate a peak conversion gain of −26 dB at an input power of 8 dBm and an intermodulation frequency of 2.3 GHz. Furthermore, the proposed transponder exhibits suppression characteristics of at least −7 and −23 dBc for the two-tone signals at 2.4 and 2.5 GHz, respectively. A conversion gain of over −30 dB is maintained across an input power range of 3-19 dBm at 2.3 GHz.