PAPER Antenna System Calibration

Calculating Antenna Noise Temperature

Transducer Gain

To calculate the noise temperature, we first needed to calculate Transducer Gain (GT):

GT = GB + GR + GA (where GB = gain due to balun, GR = gain due to receiver, and GA = gain due to attenuator -- which is negative).

Here is the resultant calculation: GT = 30 dB + 60 dB - 0.1 dB = 89.9 dB

Noise Temperature

Here is how we then calculated the noise temperature (Tn):

Tn = (PS / (B * k)) - Ta (where PS = power at source, in watts, k = Boltzmann's constant, B = bandwidth, and Ta = antenna temperature, assumed to be 300 K)

Tn = ((3.908e-15 [W])/(5 [MHz] * 1.381e-23 [m^2 * kg / K * s])) - 300 K = -243.403 K <<< This is a strange result. Not sure what's going on... (note that PS = gain_at_output - GT = -24.18 dB - 89.9 dB = -114.08 dB = 3.908e-15 W).

Data Collection

To determine if the antenna temperature responds appropriately to the environment, we recorded data over hour-long intervals for both antenna channels. We used the following programs to accomplish this:

• dsp-flowgraph.py is run to collect integrated spectra every five minutes from the antenna system using GNU Radio functionality.
• rpi_client.py is run to collect data -- also every five minutes -- from the Raspberry Pi sensors.
• dataGraphing.py processes the data and will calculate the antenna temperature at the tiem of each data burst.

-- EllieWhite - 2019-07-26