A Switchable Dual-Band Bandpass Filter With Flexible Band Allocation

In this paper, a new switchable dual-band bandpass filter (BPF) was proposed. The proposed BPF could provide two switchable dual-passband operating states. Only one bias voltage is required to achieve the switching function. The BPF was designed based on stepped-impedance resonators (SIRs), leading to a small circuit size and wide stopband response. Moreover, all passbands can be well controlled and designed independently. For a demonstration, a switchable dual-band BPF with third-order Chebyshev bandpass response was designed and fabricated using microstrip technology. For the state I, 0.9- and 1.2-GHz passbands are switched on; for the state II, 1.5- and 1.8-GHz passbands are switched on. Furthermore, the stopband rejection is >20 dB when the passbands are turned off.