Concurrent Dual-Band Shifter With Independent Tunable Phase Shift Control

This article presents a design of a reflection-type dual-band phase shifter (DPS) that allows to tuning relative phase shifts at two operating frequency bands independently. The proposed phase shifter consists of a 3-dB hybrid coupler where through and a couple of ports are terminated with reflection loads. Each reflection load comprises a couple of lines terminated with a transmission line (TL) and a varactor diode. The coupled line can achieve independent phase tuning at each operating frequency, while TL terminated with a varactor diode is used for a high relative phase shift tuning range (PSR). The proposed tunable DPS can provide not only independent tunable phase shift (ITPS) at each operating band, but also simultaneous tunable phase shift at both bands. To prove the validity of the proposed method, the DPS operating at center frequencies of 1.88 and 2.44 GHz is designed and fabricated. The measured relative PSR is 149.33^◦ at 1.88 GHz with phase derivation error (PDE) of ±8.45^◦ within 300 MHz bandwidth (BW). Similarly, the PSR at 2.44 GHz is 125.25^◦ with a PDE of ±8.36^◦ within the same BW of 300 MHz. Likewise, the minimum return loss (RL) of around 17.36 dB, and the maximum insertion loss (IL) of 1.81 dB are measured at both operating bands.