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We describe a monolithic phase shifter which combines the low loss of high‐temperature superconductivity (HTS) with the variable dielectric properties of a ferroelectric material SrTiO3. Phase shifts greater than 28 degrees per wavelength were observed around 30° K. The compatibility of YBa2Cu3O7‐x and other ferroelectric materials is discussed. © 1992 John Wiley & Sons, Inc.

Optical injection locking was experimentally performed using a 38-GHz-band InP-based HEMT MMIC oscillator and a 1.55-m lightwave. Two optical modulation schemes were compared for optical injection locking, and no difference was found except for the optical modulation frequency. With suppressed carrier modulation of the lightwave, phase noise of less than 73.2 dBc/Hz at a 10-kHz frequency offset and a 14-MHz locking range were achieved.

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This paper benchmarks the first microwave GaAs HBT amplifier results at 4.2" Kelvin. The amplifier nominal gain is 6 dB and is measured from 130 MHz to 10 GHz at fixture temperatures of 295 K, 77 K, and 4.2 K. The maximum gain variation over temperature was found to be about 2 dB. Maximum gain occured at temperatures around 50-85 K, whereas at 4.2 K, the gain seemed to drop slightly from that at RT. Only slight RF evidence of carrier freeze-out was observed at a fixture temperature of 4.2 K, although, HBT junction temperatures are estimated to be around 25-30 K. Finally, this chip was integrated as a buffer amplifier with an HTS superconductor digital logic gate and has shown functionality up to 320 MHz.