Compact On-Chip mm-wave Reconfigurable Wideband Filtering Switch in 28-nm Bulk CMOS for Integrated Sensing and Communication System Applications

In this paper, we propose a compact wideband on-chip millimeter-wave (mm-wave) reconfigurable wideband filtering switch in 28-nm bulk CMOS technology. A dual-mode LC resonator loaded with transistors is used to achieve wideband filtering responses with a transmission zero at the lower frequency band. The resonant frequency of the resonator and the location of the transmission zero can be conveniently tuned to reconfigure the passband and stopband frequencies by turning on and off the transistor. Moreover, the passband can also be switched on and off, enabling the single-pole single-throw filtering switch circuit function. In this way, the proposed mm-wave reconfigurable filtering switch is applicable to the integrated sensing and communication (ISAC) system, where image rejection in communication operation and a wide bandwidth (or high resolution) in sensing operation are both required. Furthermore, to meet the applications in the ISAC systems with different architectures, extension designs of the proposed reconfigurable filtering switch with the impedance conversion function, high-order responses, balanced-to-unbalanced transition, and differential input/output ports are presented in detailed. For demonstration, the wideband reconfigurable filtering switch has been fabricated. The core circuit has a very compact size of 0.205
$\times$
0.140 mm
$^{2}$
. Experimental results show that the passband can be reconfigured between 20-55 GHz and 37-44 GHz, with a rejection
$>$
17 dB for sensing operation and
$>$
12 dB image-band rejection for communication operation, respectively. High off-state isolation of better than 24.8 dB is also achieved.