Design of Oscillator-Based Reconfigurable Modulator With High-Q FBAR Resonators Supporting Fast OOK/BFSK/ BPSK Modulation

An oscillator-based reconfigurable modulator is proposed to support multi-mode and fast modulation. A direct-modulation structure composed of the cross-coupled oscillator with the fast-switched film bulk acoustic resonator (FBAR) is used to enhance the frequency stability under fast OOK/BFSK modulation. To avoid extra phase-reversal circuitry, a polarity-swapped switching structure is employed in the differential branches of the modulator to achieve energy-efficient BPSK modulation, and this structure is also reused as a buffer stage for OOK/BFSK modulation to avoid the loading effect. In addition, an adaptive fast-switching technique is also proposed to improve OOK/BFSK modulation data rate and energy efficiency. The modulator is fabricated in a 180 nm CMOS technology. The free-running oscillation frequencies with two FBARs are 962 MHz and 990 MHz, and the measured phase noises are -137.3 dBc/Hz@1MHz and -137.1 dBc/Hz@1MHz, respectively. For OOK/BFSK/BPSK modulation, the proposed modulator demonstrated 280/325/67.6 pJ/bit energy efficiency and 5.63/4.20/5.55 % rms EVM with 10/10/50 Mbps data rates.