This paper proposes a novel terahertz metamaterial modulator utilizing vanadium dioxide phase-change materials, which adopts three nested square split rings as a unit cell. The modulator can achieve dual functions of band-stop filter and bandpass filter by vanadium dioxide filled in the gap of split ring changing phase. The simulation results show that the central frequency of the modulator is around 0.83 THz, whether the modulator is at band-stop state or band-pass state. The modulator shows that the -3 dB bandwidth reaches to 30 GHz at the state of band-pass, and that the -20 dB bandwidth reaches to 160 GHz at the state of band-stop.
A Lange coupler with a Ka-band (26.5~40 GHz) had been designed in a 0.15 μm GaAs MMIC technology. The coupler uses λ/4 wavelength lines as the coupling lines. The coupler was realized and measured by using 50 Ω resistors as terminations. The test results of the coupler within 26.5~40 GHz frequency range as follows: the coupling degree -3.2dB at the center frequency of 33GHz, insertion loss < 3.5 dB, return loss and isolation both less than -20 dB, amplitude imbalance less than 0.06 dB, phase imbalance less than 1°. The proposed Lange coupler has extremely wide application scenarios in MMIC circuits such as Ka-band power amplifiers, mixers, and phase shifters and so on.