Abstract: Polyphase filters (PPFs) can be used to generate quadrature or other phase-shifted representations of an input signal provided to the PPF. In one approach, a “passive” polyphase filter can include a combination of resistive and capacitive elements. Such a topology can be referred to as an RC-PPF topology. Another passive circuit topology can be used to provide a PPF, by replacing the resistive elements with inductive elements, and by replacing the capacitive elements with resistive elements. A filter circuit can include cascaded RC-PPF and LR-PPF sections, such as in an alternating manner (e.g., an “RC-LR” topology). In this approach, a total insertion loss of cascaded LR-PPF and RC-PPF sections can be reduced as compared to using LR-PPF or RC-PPF sections, alone.

Abstract: A transformer-based balun circuit is disclosed herein. The balun can be implemented using a spiral transformer, where primary and secondary transformer windings can be inductively coupled and can be implemented on the same metal layer (or different metal layers, e.g. vertically adjacent metal layers). The balun can further include a compensation capacitor and a digital frequency tuning circuit. The compensation capacitor can be introduced at one of the differential terminals to reduce or suppress the amplitude and phase imbalance. The digital frequency tuning circuit can be a switchable bank of capacitors, which allows for tuning the frequency of operation of the transformer-based balun.

Abstract: A transformer-based balun circuit s disclosed herein. The balun can be implemented using a spiral transformer, where primary and secondary transformer windings can be inductively coupled and can be implemented on the same metal layer (or different metal layers, e.g. vertically adjacent metal layers). The balun can further include a compensation capacitor and a digital frequency tuning circuit. The compensation capacitor can be introduced at one of the differential terminals to reduce or suppress the amplitude and phase imbalance. The digital frequency tuning circuit can be a switchable bank of capacitors, which allows for tuning the frequency of operation of the transformer-based balun.