A 3.2-GHZ 2ND-ORDER DELTA-SIGMA MODULATOR IMPLEMENTED IN INP HBT TECHNOLOGY

This paper presents a second-order delta-sigma (Delta Sigma) modulator fabricated in a 70 GHz (f(T)), 90 GHz (f(max)) AlInAs/GaInAs heterojunction bipolar transistor (HBT) process on InP substrates, The modulator is a continuous time, fully differential circuit operated from +/-5 volt supplies and dissipates 1 W. At a sample rate of 3.2 GHz and a signal bandwidth of 50 MHz (OSR = 32 100 MSPS Nyquist rate) the modulator demonstrates a Spur Free Dynamic Range (SFDR) of 71 dB (12-b dynamic range), The modulator achieves the ideal signal-to-noise ratio (SNR) of 55 dB for a second-order modulator at an oversampling ratio (OSR) of 32, The design of a digital decimation filter for this modulator is complete and the filter is currently in fabrication in the same technology, This work demonstrates the first Delta Sigma modulator in III-V technology with ideal performance and provides the foundation for extending the use of Delta Sigma modulator analog-to digital converters (ADC's) to radio frequencies (RF).