The first observations and measurements are reported on suppression of the third-order intermodulation (IM3) product arising from nonlinear mixing of two drive frequencies in a klystron, by externally injecting a wave at the IM3 product frequency. Optimum amplitude and phase of the injected wave for maximum suppression are examined. Results indicate that suppression of the IM3 product by as much as 30 dB can be achieved. Experimental results compare favorably with predictions of a 1D simulation code that takes into account all kinematical and dynamical effects including charge overtaking and space charge forces.

A new integrated W-band frequency source MMIC is presented which consists of a 94-GHz voltage-controlled oscillator (VCO) with large tuning range and a phase comparator, forming a subharmonic injection-locked phase-locked loop (ILPLL). The ILPLL combines conventional injection-locking with an additional phase control loop to improve the locking range of the oscillator significantly. The 4th subharmonic frequency is used as the reference signal. The locking range was increased from 80 MHz without ILPLL to 4.5 GHz with ILPLL by closing the loop with an external dc amplifier. A phase noise of -83 dBc/Hz at 100-KHz offset was achieved. Pseudomorphic GaAs HEMT's and a coplanar circuit topology were used to allow integration into complex single-chip subsystems and flip-chip packaging

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For integration in receivers at 77 GHz, three passive mixers, a balanced diode mixer, a single ended and a balanced resistive mixer, as well as an active single-ended gate mixer have been realized in coplanar 0.15-mu m PM-HEMT technology on GaAs. The passive mixers achieved conversion losses of about 9 dB. The resistive mixers required an LO power of only 3 dBm and the diode mixer 10 dBm for optimum conversion. The gate mixer obtained a conversion gain of 1 dB for an LO power of 6 dBm but showed higher sensitivity to the IF load

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