A reconfigurable bandpass filter (BPF) is presented using a resonator with switchable number of transmission poles at 1.5 GHz. The resonator consists of a uniform resonator, a p-i-n diode, and an open loop. The diode is used to connect/isolate the open loop to/from the uniform resonator. When the open loop is loaded, the resonator has three transmission poles, and the BPF achieves a wideband response. On the other hand, the resonator has one transmission pole, and the BPF exhibits a narrow-band response when the open loop is disconnected. In comparison to previous work, the proposed reconfigurable BPF features a compact size, low insertion losses, minimum diode number, and a fair passband tuning ratio.