Precision Measurement of Antenna System Noise Using Radio Stars

Abstract

This paper reviews the National Bureau of Standards (NBS) preision noise measurements program for antenna systems which have been made using Cassiopeia A and the moon. The Earth Terminal Measurement System (ETMS) was developed by NBS to make measurements of figure of merit (GIT), and the noise equivalent flux (NEF). The accuracy of the noise measurements are, typically, between 5 and 15 percent for systems with antenna gains between 51 and 65 dB and frequencies between 1 and 10 GHz. Key words-antenna gain; antenna half-power beamwidth; atmospheric loss; Cassiopeia A; earth terminal measurement system; figure of merit; moon; noise equivalent flux; noise measurement; radio stars; satellite communication.

10-60 GHz GT measurements using the sun as a source-- a preliminary study

“…Therefore, since the present earth terminal measurement system (ETMS) [12] accumulates tipping-curve data automatically during a G/T measurement. O </> -C3 >, c: CD this data can be used to obtain a more accurate loss estimate.…”

“…x2 ( 10 ) where ( 11 ) 1 -e -x2 / B(Q) P (Q) dQ n / B(Q) dQ ( 12 ) for e^/d greater than unity, where d is the apparent or optical solar angular diameter. The same expressions (eqs (10) and (11) shows a decided ellipticity [5].…”

“…After minimizing this uncertainty per the discussion surrounding eq (12) and using the resulting equivalent diameter (d^= 1.0342d), the uncertainty in using eq (10) to estimate the integral in eq (12) is negligible. Equivalent disk diameter d^in units of the apparent solar diameter d as a function of frequency using 1) data from Allen [6], solid curve; and 2) data from Smerd [20], dashed curve.…”

“…Attenuation due to refractive spreading and tropospheric scatter were estimated previously [1], and will be ignored in this report since their effects are small (less than 0.1 dB) relative to attenuation from the gaseous absorption of the atmosphere. The measurement technique [12] leading to eq (1) earth's atmosphere [6] with an insert [7] indicating the duration of the burst spectrum from 10 MHz to 30 GHz. The quiet component of the solar emission dominates above 5 GHz, at which frequency most of the burst components have disappeared and the slow component is falling off.…”

Measuring radiotelescope phased array feed noise and sensitivity

“…The sensitivity is readily measured using an astronomical source of known flux with the PAF installed in a dish as for a horn feed [16]. The PAF (array and electronics) noise temperature contribution is measured in 'aperture array' mode with the PAF facing skywards prior to installation.…”