A 9.6 GS/s 112 mW 58 dB DR 150 MHz bandwidth RF bandpass transmission line ΣΔ modulator

Abstract

A 4th order RF bandpass sigma delta modulator (BPSDM) centered at 2.4GHz ISM band based on integrated transmission lines (ITLs) is presented for the first time. The modulator consists of two tunable capacitively-loaded transmission line resonators with active Q-enhancement. As a result, the design of noise transfer function (NTF) is simplified and the degradation in performance due to the jitter noise and excess loop delay (ELD) are reduced. An analytical procedure is presented, which ends up to the TL length reduction without affecting the low jitter sensitivity. The modulator is implemented in a 250nm SiGe BiCMOS technology and occupies an active area of 1.26mm2. The 1-bit modulator output achieves a dynamic range (DR) of 61dB/58dB in a bandwidth (BW) of 75MHz/150MHz, a signal-to-(noise+distortion) ratio (SNDR) of 35dB at 150 MHz BW and consumes 112mW from a 2.5V supply. In the presence of σ jitter =1.3ps rms , the measured performance is not limited by clock jitter unlike to conventional LC modulators. Moreover, more ELD (∼0.7T s ) compared to conventional LC modulators (∼0.55T s ) is tolerated, which proves the robustness of the designed ITLSDM. For the prototype, an efficient wireless technique for tuning of the resonators employing a commercial wideband antenna has been used.