A Double Cross-Coupled Delay Cell for High-Frequency Differential Ring VCOs

This paper presents a double cross-coupled delay cell (DCC-Delay cell) incorporated in a two-stage ring voltage-controlled oscillator (RVCO) that enhances its operating frequency. The DCC-Delay cell employs two cross-coupled transistor pairs, one in a pull-up network and the other in a pull-down network. This design configuration effectively reduces the time required for discharging the output node, allowing for higher operating frequencies. The RVCO's frequency is controlled by a PMOS transistor-based capacitance between the two output nodes. Simulations were performed in 65nm CMOS technology after post-layout parasitic extraction using a 1V supply voltage. The phase noise of DCC-Delay cell-based RVCO is -103.4 dBc/Hz at an offset frequency of 1 MHz, operating at 1.2GHz while dissipating 6.2mW power. The DCC-Delay cell-based RVCO achieves a 55% improvement in operating frequency compared to conventional RVCO while experiencing only slightly increasing power dissipation. The figure of merit (FOM) of the DCC-Delay cell-based RVCO is -157 dBc/Hz at a 1MHz offset frequency, rivaling other RVCO architectures in the existing literature.