A 9 GS/s 2.1..2.2 GHz bandpass delta-sigma modulator for Class-S power amplifier

A tunable fourth-order bandpass delta-sigma modulator (BDSM) designed and fabricated in 0.25 mum SiGe BiCMOS technology is presented. The input band can be tuned in a range of 2.1 to 2.2 GHz while clocking at 9 GHz. The modulator achieves 42-43 dB signal-to-noise ratio (SNR) in 10 MHz bandwidth with sine wave input over the tuning range consuming 270 mW from -3 V supply. Measurement results show that the circuit is well suited for Class-S power amplifier applications using WCDMA coding scheme. For a WCDMA modulated signal the modulator demonstrates less than 2.3 % of EVM over the full tuning range.