InP HBT continuous time 2nd order bandpass ΔΣ modulator and 1-to-16 DEMUX IC with center frequency continuously programmable from 0 to 70 Mhz

We have implemented a continuous time, 2nd order bandpass ΔΣ modulator, with center frequency tunable from 0 to 70 MHz. The modulator has a sampling rate of 4 GHz and is designed in InP Heterojunction Bipolar Technology (npn only, f_T and f_MAX ~80 GHz). At a center frequency of 62.5 MHz, the modulator exhibits an SNR ranging from 89 dB (14-bits) for a 370 kHz bandwidth to 42 dB (7 bits) for a 62.6 MHz bandwidth. These results represent about a factor of 10 improvement in bandwidth, resolution and center frequency over previously reported results in any semiconductor technology. A 1:16 DEMUX is included in the die to reduce the modulator output data rate by a factor of 16. The output of the DEMUX feeds a silicon gate array for digital filtering. The complete integrated circuit contains 1560 HBTs and dissipates 4 W. A companion chip containing I/Q filters with programmable coefficients is under development as a CMOS gate array and will provide decimation and filtering for a variety of bandwidths and center frequencies