We present a conceptual framework of planar SIS mixer array receivers and the studies on the required techniques. This concept features membrane-based on-chip waveguide probes and a quasi-two-dimensional local-oscillator distribution waveguide network. This concept allows sophisticated functions, such as dual-polarization, balanced mixing and sideband separation, easily implemented with the SIS mixer array in the same planar circuit. We have developed a single-pixel prototype receiver by implementing the concept in the design. Initial measurement results show good evidences that support the feasibility of the concept.
We present in this paper a study of a low-power consumption cryogenic amplifier with GaAs-based HEMT. A two-stage MMIC low noise amplifier for 2.5-4.5 GHz frequency range has been designed, fabricated and measured at a low-power condition with the temperature range from 300 K to 4 K. To design such a cryogenic MMIC amplifier, firstly we extracted the model of the bare-die transistor at cryogenic temperatures fabricated together with the MMIC. The temperature-dependent DC and RF characteristics of the HEMT have been measured. From the approximate noise model based on the DC characteristics, we verified that the HEMTs offer sufficient gain and reasonably noise at a relative lowpower operation condition. Subsequently, we designed a low-power dissipation cryogenic MMIC amplifier utilizing the cryogenic s2p model of the HEMTs biased at the optimal low-power condition. At cryogenic temperature, the GaAsbased amplifier achieves a gain larger than 20dB and a noise temperature as low as 10 K with a total power consumption of 1.2 mW. The low-power amplifiers can be used as first-stage IF amplifiers in a superconductor-insulatorsuperconductor (SIS) receiver, and are especially useful in focal plane arrays with large pixel count because of the merit of the total power consumption.