## Appendix  
_Specifications of the Electronic Components Used_  
\begin{tabular}{c|c|c} \hline
**Component** & **Specifications** & **Functionality** \\ \hline \multirow{6}{*}{SW} & Insertion loss \(<0.1\) dB & \multirow{2}{*}{Switching between H-, V-polarization} \\  & Repeatability \(<0.03\) dB & \\  & Mechanical switch & \\  & \(>\)10\({}^{7}\) operations & \\  & 4-bit TTL control & \\ \hline ISO1, & Tuned frequency = 1,413.5 MHz & \multirow{2}{*}{Improve matching of amplifier inputs.} \\  & \(\mathrm{Loss}=0.20\) dB & \\ \hline \multirow{3}{*}{BP1} & Center frequency = 1,413.5 MHz & Suppression of out-of-band RFI \\  & Insertion loss \(<0.77\) dB & before amplification. \\  & -3 dB bandwidth = 22 MHz & Determines the radiometer frequency \\  & Min. attenuation at 1,391 MHz = 12 dB & response. \\ \hline \multirow{3}{*}{BP2} & Center frequency = 1,413.5 MHz & Further suppression of out-of-band \\  & Insertion loss \(<1.22\) dB & RFI. \\  & -3 dB bandwidth = 22 MHz & Determines the radiometer frequency \\  & Min. attenuation at 1,391 MHz = 24 dB & response. \\ \hline \multirow{3}{*}{BP3a, (BP3b)} & Center frequency = 1,407.5 MHz & \multirow{3}{*}{Split the noise power into 2 spectral} \\  & (1,419.5 MHz) & \\ \cline{1-1}  & Insertion loss \(<1.3\) dB & bands for RFI detection in the \\ \cline{1-1}  & -3 dB bandwidth = 11 MHz & frequency domain. \\ \cline{1-1}  & Min. attenuation at 1,391 MHz = 21 dB & \\ \hline \multirow{3}{*}{LPa/b} & Cut-off frequency = 400 Hz & \multirow{3}{*}{Amplification and filtering of the detector output.} \\  & \(G=2\) (active filter) & \\ \cline{1-1}  & \(4^{\mathrm{th}}\) order LPF & \\ \hline AMP1, & \(G=40\) dB & \\ AMP2, & _NF_ = 0.5 dB (\(T_{\mathrm{AMP}}\) =34 K at \(T_{0}=313\) K) & Amplify noise power (AMP1/2) and \\ \cline{1-1}  & \(NF=0.5\) dB (\(T_{\mathrm{AMP}}\) =34 K at \(T_{0}=313\) K) & act as cold noise source (AMP5). \\ \hline \multirow{3}{*}{AMP3a/b} & DC-instrumentation amplifier & \multirow{3}{*}{Amplification of detector output} \\  & Gain = 850 & \\ \cline{1-1}  & Noise = 8 nV-Hz\({}^{1/2}\) & voltage. \\ \cline{1-1}  & Offset \(<25\) mV & \\ \hline \multirow{3}{*}{AMP4a/b} & Buffer amplifier & \multirow{3}{*}{Drive for ADC input.} \\  & Gain = 1 & \\ \cline{1-1}  & Offset = \(<10\) mV & \\ \hline \multirow{3}{*}{splitter} & Insertion loss \(<0.4\) dB & Splitting RF into two channels for \\ \cline{1-1}  & at 1,000 - 2,000 MHz & RFI detection in the frequency \\ \cline{1-1}  & Amplitude imbalance \(<0.01\) dB. & domain. \\ \hline \multirow{3}{*}{DC-block} & \multirow{3}{*}{Insertion loss \(<0.15\) dB} & remove low-frequency internal RFI or \\ \cline{1-1}  & & DC-bias signals. \\ \hline \multirow{3}{*}{detector} & Zero-bias detector diode & \multirow{3}{*}{Square-law detection of the RF-} \\  & Low-level sensitivity = 0.4 mV/\(\mu\)W & \\ \cline{1-1}  & Noise \(<50\) mV & power. \\ \cline{1-1}  & Frequency range: 0.01-12 GHz & \\ \hline \multirow{3}{*}{ADC} & Number of channels = 4 & \multirow{3}{*}{Digitize the amplified, filtered, and \\ \cline{1-1}  & Resolution = 16 bit & \\ \cline{1-1}  & Input voltage range = \(\pm 2.5\)V & \\ \hline source & Noise temperature \(\approx\) 1,575 K & Additional hot calibration source. \\ \hline \end{tabular}