Testing results from Spring 2014

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Spring 2014 Testing Results

A number of experiments to both verify the operation of the radiometer and calibrate were conducted in the Spring of 2014. These results shown below show the operation of the radiometer and include various screenshots of the radiometer in operation as well as the results from these experiments.

The experiments performed used a 50 ohm matched load that was attached to the input of the ISU RF Front end. This RF Front end used bandpass filters and Low Noise Amplifiers (LNAs) to boost and filter the signal to the desired bandwidth of 20 MHz at 1.4 GHz. This signal was then feed directly into the software defined radio. The matched load was then submerged in different mediums in which the temperature was known. The first medium was Liquid Nitrogen (LN2) which boils at 77 K. The second medium was a Ice bath which is at 273.15 K. The matched load was also allowed to be at room temperature which was estimated to be at 296.15 K. In all cases the matched load was allowed to soak for a minimum of 2 mins in order to equalize the temperature.

Lab 0 - Baseline test

Lab 0 was performed to give a baseline of the operation of the software defined radio. For this setup only the software defined radio was used. Both raw IQ values and total power measurements were stored for this experiment. The experiment soaked the 50 ohm matched load for a minimum of 2 mins. The table below shows the raw files observed during the experiment and the settings used on the software defined radio.

N200 Settings

RF Gain - 23

Center Freq. - 1.406 GHz

Integration time - 2 sec


Air - .148

LN2 - .090

Ice Bath - .135

Air - .144

LN2 - .090

Ice Bath - .138

Air - .144

Lab 1 - Calibration test

Lab 2 - Interfering signal injected

Lab 3 - Calibration with band reject filter

Lab 4 - Measurement with filtered signal present with 250 kHz filter

Lab 5 - Measurement with filtered signal present with 500 kHz wide filter