Piezoelectric transducer-controlled tunable hairpin bandpass filter

Abstract

A piezoelectric transducer (PET)-controlled tunable hairpin bandpass filter (BPF) is introduced. A dielectric perturber is attached to a PET cantilever beam and suspended above the hairpin BPF. The PET actuator vertically lifts up or pulls down the attached dielectric perturber using a DC bias voltage. The dielectric perturber changes the effective permittivity, causing a variation in the BPF's effective capacitance. This changes the centre frequency and passband of the BPF. The hairpin BPF is designed at 5.8 GHz with a fractional bandwidth (FBW) of 0.414%. The fabricated BPF shows a measured insertion loss of less than 2.5 dB and a return loss of greater than 12 dB in the frequency tuning range.

Effects of dielectric substrates on piezoelectric transducer tunable filter

“…PET tunable microwave filters are novel and potential devices because PET has no connection to microwave circuits, and can be used in not only planar microstrip filters but also three‐dimensional structure filters such as evanescent‐mode cavity filters and dielectric resonator filters . Compared to the amount of published work on other tunable microstrip filters, the literature on PET tunable microstrip filters is only little .…”

“…PET tunable microwave filters are novel and potential devices because PET has no connection to microwave circuits, and can be used in not only planar microstrip filters but also three‐dimensional structure filters such as evanescent‐mode cavity filters and dielectric resonator filters . Compared to the amount of published work on other tunable microstrip filters, the literature on PET tunable microstrip filters is only little . In Reference , a PET tunable third‐order hairpin microstrip bandpass filter was designed and tuned from 5.6 GHz to 5.8 GHz with a DC voltage from −80 V to 60 V. In Reference , the tuning range of a PET tunable fourth‐order open loop microstrip bandpass filter is from 1.874 GHz to 2.0 GHz with a controlled DC voltage of −90~90 V and the selectivity of the filter is high, but the asymmetrical physical structure adds the design complexity.…”

“…Compared to the amount of published work on other tunable microstrip filters, the literature on PET tunable microstrip filters is only little . In Reference , a PET tunable third‐order hairpin microstrip bandpass filter was designed and tuned from 5.6 GHz to 5.8 GHz with a DC voltage from −80 V to 60 V. In Reference , the tuning range of a PET tunable fourth‐order open loop microstrip bandpass filter is from 1.874 GHz to 2.0 GHz with a controlled DC voltage of −90~90 V and the selectivity of the filter is high, but the asymmetrical physical structure adds the design complexity. In Reference , a PET tunable low temperature co‐fired ceramic (LTCC) resonator with a wide tuning range under a DC voltage of 0~200 V was introduced but has a poor stopband characteristic.…”

Piezoelectric Transducer-Tuned Fourth-Order Microstrip Bandpass Filter With Cross-Coupling

“…As mentioned above, the relatively low Q of varactor diodes restricts the implementation of higherorder and narrowband tunable filters. Fortunately, PET tunable higher-order filters have very low insertion loss over a tuning range because the PET is not directly connected to the circuit of the filter, but the published literature about PET tunable filters is sparse [8][9][10][11]. Jung et al [8] designed a thirdorder hairpin PET microstrip BPF with a tuning range from 5.6 to 5.8 GHz for a control voltage from −80 to 60 V; Al-Ahmad et al [9] manufactured a PET tunable microstrip resonator, and the resonant frequency varied from 1.1 GHz to 2.6 GHz with a voltage of 200 V applied to the PET.…”

“…Fortunately, PET tunable higher-order filters have very low insertion loss over a tuning range because the PET is not directly connected to the circuit of the filter, but the published literature about PET tunable filters is sparse [8][9][10][11]. Jung et al [8] designed a thirdorder hairpin PET microstrip BPF with a tuning range from 5.6 to 5.8 GHz for a control voltage from −80 to 60 V; Al-Ahmad et al [9] manufactured a PET tunable microstrip resonator, and the resonant frequency varied from 1.1 GHz to 2.6 GHz with a voltage of 200 V applied to the PET. However, the selectivity was very low, and the bandwidth varied significantly over the wide tuning range; Hsieh and Chang [10] realized a four-stage open-loop microstrip filter tuned by a PET, and the center frequency tuning range was 126 MHz (1.874 ∼ 2.0 GHz) when the control voltage changed from −90 V to 90 V, but the structure was asymmetric, which increased the design complexity.…”