This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS 1 High-Isolation Multimode Multifunction 24-/60-GHz CMOS Dual-Bandpass Filtering T/R Switch Youngman Um , Student Member, IEEE, and Cam Nguyen , Fellow, IEEE Abstract— Fully integrated 24-/60-GHz dual-band transmit/ receive (T/R) switch capable of bandpass filtering and switching operations in single bands and concurrent dual band, coupled with simultaneous transmission and reception, is developed using a 0.18-μm SiGe BiCMOS process. The developed bandpass filtering switch can also function as a diplexer with switching functions. The measured insertion losses of the T/R switch are 2.9 and 8.7 dB at 24 and 60 GHz in single-band modes and 3/8.8 dB at 24/60 GHz in concurrent dual-band mode, respec- tively. The measured isolations are 53 and 43 dB at 24 and 60 GHz in single-band modes and 50/57 dB at 24/60 GHz in concurrent dual-band mode, respectively. The measured inputs P 1-dB are 20.6 and 16.4 dBm at 24 and 60 GHz in single-band modes and 15.9/13 dBm at 24/60 GHz in concurrent dual-band mode, respectively. The measured inputs IP 3 are 23.2 and 22.5 dBm at 24 and 60 GHz in corresponding single-band modes, respectively. The total chip size is 1480 μm × 520 μm excluding all the RF and dc pads. Index Terms— Bandpass filter (BPF), BiCMOS, CMOS, diplexer, dual-band circuit, radio frequency integrated circuit, SPST switch, transmit/receive (T/R) switch. I. I NTRODUCTION T RANSMIT/RECEIVE (T/R) switches are used often in RF transceivers. Furthermore, in RF transceivers, exter- nal bandpass filters (BPFs) are normally used together with T/R switches to reduce undesired out-of-band signals. These separate BPFs increase the size and cost of the overall system. A more effective approach is to integrate the bandpass filtering function into switches to make a dual function (switching and filtering) simultaneously. While numerous single-band silicon-based radio frequency integrated-circuit switches have been developed at microwave and millimeter-wave frequen- cies, e.g., [1]–[4], few dual-band CMOS single-pole double- throw and T/R switches, particularly those with integrated bandpass filtering function and concurrent operation, have been reported to date in spite of their importance in multiband RF systems [5]. Multiband RF systems working over multiple bands provide significant advantages in terms of cost, size, operation, versatility, and performance as compared to their single-band counterparts. Manuscript received March 29, 2018; revised May 8, 2018; accepted June 1, 2018. This work was supported by NPRP through the Qatar National Research Fund (a member of Qatar Foundation) under Grant 6-241-2-102. (Corresponding author: Youngman Um.) The authors are with the Department of Electrical and Computer Engineer- ing, Texas A&M University, College Station, TX 77843-3128 USA (e-mail: youngman.um@tamu.edu; cam@ece.tamu.edu). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LMWC.2018.2847022 Fig. 1. (a) Schematic of the 24-/60-GHz dual-bandpass filtering T/R switch. (b) 24-GHz TX/RX concurrent mode. (c) 60-GHz TX/RX concurrent mode. (d) 24-GHz RX and 60-GHz TX concurrent modes. In this letter, we report the development of new 0.18-μm CMOS dual-bandpass filtering T/R switch operating in two different frequency bands centered around 24 and 60 GHz. The switch can operate in a variety of separate and concur- rent modes, either in single band, dual band, transmission, and reception or simultaneous transmission and reception, with bandpass filtering and enhanced isolation. It can also function as a diplexer with switching capability and allow the transmission and reception in multiband to be carried out simultaneously with a single antenna—a highly desirable feature for multiband RF systems. The frequency bands at 24 and 60 GHz are chosen for nonlicense applications taking advantages of both long- and short-range communications, networking and sensing at 24 and 60 GHz, respectively. II. SWITCH ARCHITECTURE,DESIGN, AND OPERATION A. 24-/60-GHz Dual-Bandpass Filtering T/R Switch Fig. 1(a) shows the schematic of the 24-/60-GHz dual- bandpass filtering T/R switch implemented using four SPST switches. It has five different ports: Port 1 is the transmit- ting (TX) port for both 24- and 60-GHz signals; Port 2 (ANT1) and Port 3 (ANT2) are the antenna ports for both 24 and 60 GHz; and Port 4 (RX1) and Port 5 (RX2) are the receiving (RX) ports for 24- and 60-GHz signals, respectively. The ANT ports could belong to a single antenna with two ports operating concurrently at 24 and 60 GHz or two different antennas operating concurrently at 24 and 60 GHz. The T/R switch’s design parameters and their values are listed in Fig. 1(a). One of the most crucial requirements in multiband T/R switches designed for concurrent TX and RX operations with 1531-1309 © 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.