| dc.description.abstract | In this thesis, a digital phase shifter designed based on magnetically coupled all-pass networks (MCAPNs) is presented. The effect of the magnetic coupling between the two inductors within an all-pass network is exploited for increasing the bandwidth of phase shifters. As a proof of concept, a broadband 4-bit phase shifter is implemented in TSMC 0.18-µm CMOS process.
The effect of the magnetic coupling between the two inductors within an all-pass network is analyzed. By even–odd mode analysis, the S parameters of the MCAPN are derived. The conditions for the network to provide an all-pass frequency response are subsequently obtained. Furthermore, the MCAPN is applied to phase shifter design. Two phase-shifter topologies, namely dual networks with external path-select switches and single network with internal switched capacitors, are analyzed. The relations between the design parameters and the phase shift are derived.
Based on the results obtained from the theoretical analysis, a fully-differential 4-bit phase shifter is designed and implemented in TSMC 0.18-µm CMOS process. In the phase shifter, the 180° phase-shifting stage is realized using a pair of single-pole double-throw switches whereas the other phase-shifting stages are constructed using single MCAPN with internal switched capacitors. The 90° phase-shifting stage is constructed by cascading two MCAPNs with different center frequencies whereas the 45° phase-shifting stage consists of only a single MCAPN. Finally, in the 22.5° phase-shifting stage, varactors are used instead of switched capacitors so as to provide a continuous phase shift, which can be fine-tuned in case process variations are too severe.
The measurement results of the 4-bit phase shifter show that the root-mean-square phase error is lower than 3° from 1.28 GHz to 4.22 GHz, corresponding to a 106.9% bandwidth. Within the frequency range, the input and output return losses are greater than 7.7 dB, the insertion loss is less than 12.2 dB, and the amplitude error is within ±1.5 dB for all 16 states. | en_US |