Phase Shifting Trimmer with Small Precision Phase Change for Offsetting Process-Voltage-Temperature Tolerances

Phase Shifters (especially the digitally-controlled ones) often tend to omit phase shifting capabilities of less than 5.625° of phase change; due to heavy insertion and return loss performance degradation every time a phase-shifting block is appended to the overall phase shifting chain. In this work, an architecture is shown how one can achieve such small changes of phase (for use as a least-significant-bit stepper); without heavy performance sacrifice. The architecture presented is a series of diode loaded transmission line phase shifter (similar to microwave delay line for analog signal correction) for trimming (or calibrating) though small phase steps. The proof-of-concept trimmer operates at 2.5 GHz and has 8-bits. It traverses a total phase change of 1.2° and it has an average phase change of 0.16° per bit (degrees/bit). For small phase changes, the return and insertion losses deliverance from this architecture might be the best available from the different types of phase shifting compositions out there (if properly designed); and can be used in conjunction with other phase shifting blocks. The trimmer in this work had return loss better than −20 dB and insertion loss of less than 1.2 dB for all 8 states.