Design of CMOS Dual-Band Dual-Function Filter-Switches

This chapter primarily discusses the design of four different dual-band SPDT and T/R band-pass filter-switches (namely, Design 1, 2, 3 and 4). These switches demonstrate not only switching but also band-pass filtering functions. Design 1 presents a 0.18-µm CMOS dual-band T/R switch having a band-pass filtering function working concurrently over 35.5–43.7 GHz and 56.4–63 GHz. The developed filter-switch has multiple ports, with each port handling a dual-band signal concurrently, and a high isolation (more than 50 dB over the two pass bands) between ports, which making it attractive for the use of the dual-band RF systems. It is also useful for systems having multi-port and dual-band concurrent operation with band-pass filtering and high isolation. The filter-switch is designed based on a 3rd dual-band band-pass filter with its capacitors replaced with shunt nMOS transistors to accommodate switching function. Design 2 describes a 0.18-µm CMOS concurrent T/R switch having dual-band-pass filtering function across 17.2-27.3 GHz and 52.5-66.5 GHz. The filter-switch is implemented with dual-band quarter-wavelength LC networks and dual-band resonators with their capacitor replaced with shunt nMOS transistor. The on/off states of the filter-switch are determined through a quarter-wavelength characteristic of the dual-band LC network and the off/on states of the shunt transistor. The developed T/R filter-switch has multiple ports, with each port being capable of handling dual bands concurrently, making it attractive for the use in multi-band RF systems, and is needed for multi-port and multi-band concurrent operations with band-pass filtering function. Design 3 shows 0.18-µm CMOS dual-band SPDT and T/R switches having band-pass filtering function over 14.6-30.4 GHz, 48-62.3 GHz and 14.6-30.3 GHz, 48.4-64.8 GHz, respectively. The filter-switches are based on a 2nd order band-pass filter. The dual-band band-pass filtering SPDT can operate in single-band mode at 24 or 60 GHz as well as concurrent dual-band modes at 24 and 60 GHz. The dual-band band-pass filtering T/R switch’s operation is more versatile, and it can be used for various individual and concurrent switching functions. It can operate in single-band transmitting or receiving mode at 24 and 60 GHz, and concurrent dual-band transmission or reception at 24 and 60 GHz. It can work completely in concurrent modes including single-band concurrent transmission and reception at 24 or 60 GHz and dual-band concurrent transmission and reception at 24 and 60 GHz. The developed T/R filter-switch makes possible simultaneous transmissions and receptions with a single antenna, which is desirable in RF systems yet not feasible with conventional T/R switches. Design 4 explains a 0.18-µm CMOS concurrent dual-band SPDT filter-switch operating over two distinctive wide bands around 24 and 60 GHz. In the on-state of the switch, the SPDT filter-switch is equivalent to a dual-band resonator. The concurrent dual-wideband SPDT filter-switch has a decent insertion loss, compact size, and good power handling capability.