Switched integrated band-pass filter bank utilizing 0.25-um pHMET GaAs process for S-, C-, and X-band applications

Abstract

This letter presents a fully monolithic microwave integrated circuit (MMIC) switched filter banks (SFBs) that feature a digitally selectable operation bandwidth frequency. The integrated SFBs with four independently controlled channels span the 2 GHz to 12 GHz frequency range. Unlike the existing methods, the proposed SFB consists of a pair of single-pole four-throw (SP4T) switches coupled with four band-pass filters (BPFs), and the TTL signal can directly drive the SFB through an inner integrated FET-driven circuit, achieving facility usage in the RF system. For verification, two wideband SFB MMICs were designed and fabricated using a 0.25-µm gallium arsenide (GaAs) based InGaAs pHEMT Enhancement/Depletion-Mode Device (E/D-Mode) process, named the low-band SFB and high-band SFB. Measurement results show that the minimum insertion losses for the four channels of the proposed low-band MMIC SFB are around 4.6 to 6.3 dB. The measured Rectangle factor 𝑆𝐹 30𝑑𝐵 for the four channels are all below 1.87. The measured minimum insertion losses are around 4.9 to 6.1 dB for the high-band SFB. The measured Rectangle factor 𝑆𝐹 30𝑑𝐵 for the four channels are still bellow 2.15. The proposed SFB MMIC shows remarkable selectivity and high integration.