Monolithic integrated circuits for mm-wave instrumentation

The GaAs sampling head IC fabricated makes use of a monolithic nonlinear transmission line (NLTL). This is accomplished by using the voltage-dependent capacitance of GaAs varactors distributed periodically along a coplanar transmission line to cause shock-wave formation when driven by a large, approximately 10-V signal. A two-diode sampling bridge is integrated with the NLTL as the strobe pulse generator to achieve a sampling bandwidth of over 290 GHz. Also integrated are two samplers with a resistive directional bridge to form an S-parameter test-set on a chip. Greater than 10-dB directivity is demonstrated to 60 GHz. The speed of the sampler is evaluated by using the onboard NLTL test signal generator. With the test NLTL driven at 10 GHz+100 Hz and the strobe NLTL driven at 5 GHz, the sample output showed a 160- mu s 90% to 10% falltime which corresponds to 1.6 ps in real-time.<>