کنفرانس مهندسی برق ایران

صفحه اصلی / سی و چهارمین کنفرانس بین المللی مهندسی برق

A Compact, Highly-Selective, Smart Frequency Detectection Method Using Acoustic-Wave Lumped-Element Resonator Filter

نویسندگان :

Alireza Azar¹ Mohammad Khoshakhlagh² Nasser Masoumi³

1- دانشگاه تهران 2- دانشگاه تهران 3- دانشگاه تهران

کلمات کلیدی :

Surface Acoustic Wave،frequency-to-voltage conversion،Acoustic-Wave Lumped-Element Resonator،frequency detection،power detector

چکیده :

This paper presents a low-cost, compact frequency detector for passive SAW sensors that combines a frequency-to-voltage conversion (FVC) scheme with a highly selective Acoustic-Wave Lumped-Element Resonator (AWLR) filter. The proposed architecture converts the short decaying SAW response into a DC voltage via a high-Q AWLR frequency-selective path and a logarithmic power detector; the resulting voltage is digitized and mapped to frequency by a microcontroller. The AWLR structure provides two transmission zeros and a sharp resonance peak, producing large RF power variation over small frequency shifts and enabling robust, amplitude-insensitive frequency estimation. A prototype implemented on FR-4 was characterized in the frequency band 433–434 MHz using a commercial SRF433K resonator. Measured results show a resonance at 433.912 MHz (S21 ≈ −2 dB) and a transmission zero at 433.240 MHz (S21 ≈ −39 dB), i.e., ≈37 dB change across ≈672 kHz, which produces ≈1 V DC variation at the detector output. The detector’s settling time is 20–30 μs at resonance and ≈40 μs at the transmission zero, yielding an update rate on the order of 30–40 μs. Compared to existing FVC, digital frequency estimation (DFE), and instantaneous frequency measurement (IFM) approaches, the proposed solution achieves < 1 MHz effective bandwidth while keeping design complexity, cost, and PCB area low, making it suitable for low-power, cost-sensitive SAW sensor readers.