A Wideband Digital-to-Frequency Converter with Built-In Mechanism for Self-Interference Mitigation

A digital-to-frequency converter (DFC) assisted by a built-in-self-measurement mechanism is presented. It demonstrates the capability to overcome oscillator pulling that is caused by the high-speed digital frequency-tuning signal that is fed into the DFC’s digitally-controlled-oscillator (DCO), thereby allowing the DFC to accommodate high-rate modulating data. Thus, by placing replica images and quantization noise far away from the transmitted carrier, the presented DFC is suitable for wireless applications having the most demanding spectral mask requirements, without necessitating RF filtering in the transmitter’s signal path. The proposed solution, designed with minimum overhead, reduces the extent of injection pulling experienced by the digitally controlled oscillator (DCO) due to ΣΔ dithering applied to its capacitor bank by adjusting the phase between the aggressor and victim signals through a digitally controlled delay (DCD) line. The proposed calibration and compensation scheme for the DCD is autonomous and simple computationally. The proposed solution has been demonstrated in a transmitter of a commercial cellular CMOS system-on-chip (SoC).