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Mars-1
MAtrix Radiometric System project ( MARS ).
First phase MARS-1

The MAtrix Radiometric System project is intended to design more or less simple, but effective radiometric support to the RATAN-600 the "Cosmological Gene" project. It is generally recognized for present time, that matrix progress trend for radiometers is the future of the radio astronomy instrumentation. MARS-1 stage of the project main goal is to work out and then investigate single radiometric module of the assumed matrix system, taking into account the possibility to clone it for the next phase of the project. MARS-1 radiometric module is composed of the front-end amplifier ( LNA ) phase, main and back-end amplifier stages, band-limiting filter, detector and low-frequency preamplifier ( figure 1 ).




Figure 1. Block diagram of single channel radiometer MARS-1.

The design was a straight amplifier, without any frequency conversion. The key components used were:
  • UMS chip HEMT transistors EC2612 for the hybrid technology front-end LNA,
  • two of Hewlett-Packard HMMC-5040 MMICs as main and back-end amplifiers,
  • and Hewlett-Packard HSCH 9161 zero bias beamlead Schottky diode as square-low detector.
  • To assume some special mode of operation, the module structure was supplemented with Hewlett-Packard voltage-controlled attenuator MMIC HMMC-1002 between LNA and main amplifier.

Parameters of the resulting radiometric receiver were as follows:
fo = 30 GHz ( o = 1 cm ), f = 6 GHz, the overall gain 65 dB, Tsys = 300 K. There was noise generator designed at the same time to be used as a secondary noise standard for calibration. The noise generator is of amplified noise type, utilizing the same HMMC-5040 MMIC amplifiers, two in series, with a matched load at the input of the first one. The radiometric module and the noise generator module are shown in the figure 2.




Figure 2. The radiometric ( left ) and noise generator modules.

The overall dimensions of the radiometric module are 13x24x59 mm and of the noise generator module are 13x24x29 mm. The input waveguide window is for WR28 waveguide. MARS-1 radiometric module investigated at the laboratory at three different modes of operation: total power, noise-added ( NAR ) and switched mode. As a result of test, only the last mode was accepted for future application, as the stability of the switched radiometer was about of the order of magnitude better ( or, in other words, 1/f knee frequency was correspondingly lower ), than for other modes. The first MARS-1 radiometric module was tested at the RATAN-600 radio telescope completed with it's regular radiometers. The result ( atmospheric radio emission recording ) is shown in the figure 3.



Figure 3. Atmospheric radio emission at four wavelengths of RATAN-600.

The output signals of the short-wave radiometers ( = 1.38 cm and = 1.0 cm ) are to a great extentcorrelated, so the = 1.38 cm radiometer information can be used to "clean" = 1.0 cm output data.

References