Compact and wideband 3-D IPD butler matrix for millimeter-wave communications

A 4 x 4 Butler matrix for millimeter-wave communications is presented in this paper. The circuit takes advantage of a new 3-D Integrated Passive Devices (IPD) process to achieve a performance/compactness trade-off substantially higher than conventional IPD designs. A footprint of 0.84 mm2 is reached by using 3-D transformers and solenoids for designing couplers and phase shifters. Couplers are optimized to maximize the bandwidth of the Butler matrix. Phase variations with frequency are also tuned between phase shifters and crossover for the same purpose. The resulting experimental bandwidth, defined by reflection coefficients at -10 dB, is from 20 GHz to 30.1 GHz, and from 22.1 to 27.5 GHz considering a maximum phase error of 10 degrees for the four states -45 degrees, 135 degrees, -135 degrees and 45 degrees, while insertion losses are measured close to 1.3 dB. Matchings and isolations remain below -17 dB and -12 dB, respectively.

Automated summary

A 4x4 Butler matrix for millimeter-wave communications is presented in this paper, which utilizes a new 3-D Integrated Passive Devices (IPD) process to achieve a higher performance/compactness trade-off. The design incorporates 3-D transformers and solenoids to optimize couplers and phase shifters and results in a wide bandwidth and low insertion loss.