CENTER FOR SPACE MICROELECTRONICS TECHNOLOGY

Low Noise Superconductor/Semiconductor 7.4 GHz Receiver Downconverter

What is it?

The National Aeronautics and Space Adminisration has developed a low noise microwave receiver downconverter, exploiting the best characteristics of semiconductor and high-temperature superconductor technology, for space applications. This joint project was conducted by the Jet Propulsion Laboratory and the Lewis Research Center for the Navel Research Laboratory's High Temperature Superconductivity Space Experiment (HTSSE II). The unit accepts a 400 MHz wide signal, centered at 7.35 GHZ, and converts it to a band centered at 1.0 GHz. This is a typical NASA uplink band used for deep space communications. When cooled to 77K, the downconverter has a noise figure of 0.7 dB and a conversion gain of 18 dB. The receiver consumes only about 70 mW of power.

Advantages:

The reduction in noise temperature by approximately 60%, compared to a room temperature receiver, enables a corresponding:

The Technology:

The downconverter consists of: a thin-film, high-temperature superconductor (HTS) bandpass filter; a two-stage low noise amplifier; an oscillator with an HTS resonator; and a mixer with an integral low pass filter. The entire unit was built and tested to space qualification standards. In fact, much of the effort was spent developing construction and fabrication techniques compatible with HTS materials and the rigorous demands of space flight.

 Both superconducting circuits (i.e. the filter and oscillator) consists of a patterned thin film of Yttrium-Barium-Lanthanum-Copper-Oxide (YBLCO) deposited on Lanthanum Aluminate substates. The YBLCO film, of average thickness 0.6 microns, was deposited by laser ablation, and then coated with 1000 Angstroms of gold prior to air exposure. The gold layer protected the YBLCO film during subsequent photolithographic processing and formed low resistance bonding contacts. Additional processing provided a final gold thickness of 4000 Angstroms in the contact areas. The ground planes consisted of a niobium/copper/gold trilayer film.

Both semiconductor circuits (i.e.the low noise amplifier and mixer) consist of Titanium/Tungsten-Gold metallization deposited on Alumina substates.

 The bandpass filter is a 4-pole coupled microstrip line implementation with a 3 dB bandwidth of 400MHz. The passband insertion loss in front of the amplifier improves the overall noise figure by about 0.2 dB compared to an equivalent metal filter.

 The low noise amplifier uses GaAs based high electron mobility transistors. Matching is achieved for both stages using quarter-wave transformers. Coupled lines act as interstage DC blocks and tuning pads were placed adjacent to the the microstrip to tailor the response. The noise temperature, including cable and test fixture losses, is less than 44K and the gain is 28 dB.

The local oscillator is a GaAs MESFET based, reflection mode circuit. A linear resonator coupled to the output line is used for stabilization. The HTS resonator provides a "Q" which is at least 10 times better than that obtainable from a normal metal microstrip resonator, thereby producing a substantially lower phase noise. "Q" values in excess of 4000 have been measured. Output power is 0 to +3 dBm.

 The balanced mixer uses low barrier silicon diodes and has provisions for DC bias so that minimal oscillator drive is required. LO-to-RF isolation is 33 dB, RF-to-IF and LO-to-IF isolation is 37 and 43 dB, respectively. Conversion loss is better than 6 dB. All the ciruits are constructed as submodules attached to nickel-gold plated kovar carriers using silver-filled epoxy, and are integrated into a hermetically sealed nickel-gold plated kovar housing.

 

Potential Commercial Uses:

Options For Commercialization :

This technology opportunity is part of the NASA Technology Transfer Program. The program seeks to stimulate development of commercial applications from NASA-derived technology. NASA fostered the idea that early demonstrations of the breakthrough technology of high temperature superconductivity would provide a path for rapid commercialization. A space qualified version of this prototype receiver has been built and tested. There is potential for widespread insertion of this technology into the commercial marketplace; however, careful application specific tradeoff studies need to be undertaken.

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 For further information contact:
Dr. Jeff Barner, JPL
Phone: (818)354-7353
E-mail:j.barner @jpl.nasa.gov