Harmonic Rejection Single-Side Band CMOS Mixer

This study presents a single-side band (SSB) mixer that generates a sinusoidal signal at a frequency fc − fb corresponding to a given offset frequency fb , and an RF sinusoidal signal at fc. Because generating pulse signals is more cost-effective than generating sinusoidal signals at low frequencies, an offset-frequency signal is applied in the form of the pulse waveform. However, the application of a pulse to a simple switching core in an SSB mixer results in the appearance of significant harmonic components in the final output. To address this issue, this study adopts a harmonic rejection mixer (HRM) consisting of five double-balanced mixers (DBMs) as the switching core of the SSB mixer. To suppress higher-order harmonics further, the pulse signal is first passed through a first-order RC low-pass filter before driving each DBM. The proposed structure was designed and fabricated using a 28 nm CMOS process, and the experimental results confirmed a harmonic suppression of more than 40 dBc.