Generating 45 ring45^∘ 45 ° phase-shifted W-Band signals for subharmonic IQ modulation

The evolution of mobile communication and the corresponding need for growing data rates necessitate increasing absolute bandwidth within the front-end hardware. However, increasing the operating frequency brings modern integrated circuits closer to their maximum oscillation frequency, making signal generation less efficient. Therefore, subharmonic system architectures utilizing oscillator signals at fractions of the desired operating frequency are beneficial compared to fundamental approaches. However, the subharmonic factor changes phase requirements in the system architecture. As a key component for communication circuits, the Inphase/Quadrature (IQ) modulator is mainly concerned with this changing phase requirement. In this work, we present how to generate 45 ring 45^∘ 45 ∘ phase shifts for subharmonic IQ modulators. We showcase the theoretical fundamentals for generating 45 ring 45^∘ 45 ∘ phase shifts and prove it with a realization based on an integrated Lange Coupler in a SiGe technology. For a phase error of plus or minus 5 ring ±5^∘ ± 5 ∘ , a relative bandwidth of 51.5 percent sign $51.5%$ 51.5 % is achieved at a center frequency of 83.5 GHz. Thereby, we achieve the highest reported operating frequency for a 45 ring 45^∘ 45 ∘ phase shift generator while still offering a differential integrated realization. Utilized as the local oscillator for a subharmonic IQ mixer, an image rejection ratio of almost equals 30 ≈ 30 ≈ 30 dB can be achieved in the frequency range from 140 to 190 GHz.