A 250 MHz delta-sigma modulator for low cost ultrasound/sonar beamforming applications

Single-bit delta-sigma (ΔΣ) modulation reduces the complexity of receive beamformers in ultrasound and sonar imaging applications. These applications, however, require a sampling rate in excess of 220 MHz due to the high bandwidth of the echo signals. In this paper, the design and implementation of a 250 MHz second-order single-bit ΔΣ modulator suitable for ultrasound/sonar applications is presented. The circuit is realized in a 0.18 μm P-well CMOS technology and dissipates 20 mW average power when clocked at 250 MHz. The area of the circuit is 0.24 mm². Post-layout simulations show that the modulator achieves 48 dB maximum SNR and 50 dB dynamic range for a 5 MHz input signal bandwidth.