Differential 45° Phase-Shifted Lo Signal Generation to Enable Subharmonic IQ Modulation for Broadband 6G Communication in the D-Band

This work presents a broadband generation of 45° phase-shifted signals in the W-Band in a 90 nm SiGe BiCMOS technology. It is designed for IQ modulation in the D-Band, where the use of subharmonic system architectures is beneficial with regard to efficient signal generation. However, the subharmonic factor, which is two for this work, reduces the required phase shift for IQ modulators from 90° to 45°. Our approach utilizes an integrated Lange Coupler to generate 45° phase-shifted signals by adding the Lange Coupler's in-phase and quadrature output signals. Accepting a phase error of ± 5° a relative bandwidth of 51.5% is achieved at a center frequency of 83.5 GHz, which represents the highest published operating frequency for an integrated generation of a 45° phase shift. Embedded into a subharmonic IQ modulator, a sideband suppression of more than 25 dB is achieved over a bandwidth of 60 GHz, covering a large portion of the D band.