A homodyne five‐port network analyzer operating in the W‐frequency band

Abstract

both stubs are approximately an eighth of a wavelength long at the fundamental frequency. This configuration provides a large phase gradient, thus improving the phase-noise performance of the circuit. Additionally, the fundamental signal can be coupled out with a variable coupling factor by tapping the short stub. As described above, the phase condition is enforced by an appropriate coupling line at the base of the devices. The resulting layout is very compact, as the maximum line length in the design is an eighth of a wavelength.Critical parts of the circuit are characterised by an electromagnetic simulation in order to take additional parasitic elements into account. Further parasitic coupling is minimised by an appropriate layout. RESULTSThe output spectrum of the oscillator at the push-push output was measured using a WR-10 waveguide measurement system. The output power was determined by calibrating the system for frequencies above 110 GHz by measurements with a power sensor. The resulting spectrum is depicted in Figure 2. An output power of about 0 dBm at 124.7 GHz is measured. This performance is achieved at a low power consumption of only 70 mW. The phase noise can be estimated from the measured spectrum to be about Ϫ94 dBc/Hz at 1-MHz offset, which is a very low value for this frequency range.The simulation yields an output power of 0.7 dBm at an oscillation frequency of 124.4 GHz for the identical configuration. Phase noise is simulated to be Ϫ98 dBc/Hz at 1-MHz offset. These results demonstrate that first-pass design success can be achieved for fully integrated circuits, even in the F-band, with accurate device models, additional consideration of parasitic elements by electromagnetic simulations, and a careful layout. CONCLUSIONA SiGe HBT push-push oscillator developed for the 122-GHz ISM frequency band has been presented with both simulated and experimental results. The measured data demonstrate that the most advanced SiGe processes with f T in the 200-GHz range are feasible for applications in the higher mm-wave range, up to frequencies beyond 100 GHz.