Interferer Induced Jitter Reduction in Bandpass CT ΣΔ Modulators for Receiver Applications

The jitter sensitivity of continuous-time ΣΔ modulators is well known. It becomes an even more severe performance bottleneck in receiver applications, when out-of-band interferers are present together with colored phase noise. Bandpass ΣΔ modulators, as a competitive candidate for software-defined radios, are typically considered to be disadvantageous regarding jitter, and it can be shown that they are at least similarly affected by jitter as the mixer in a direct conversion receiver. In this paper, an analog interferer suppression technique is presented for bandpass ΣΔ modulators, which allows them to be more tolerant to interferer induced jitter error, thereby relaxing the overall clock phase noise requirements compared to other receiver architectures. The proposed technique is also combined with a previously published digital interferer suppression technique in order to provide suppression over a larger frequency range.