One-Port Direct/Reverse Method for Characterizing VNA Calibration Standards

Abstract

Abstract-This paper introduces a one-port method for estimating model parameters of VNA calibration standards. The method involves measuring the standards through an asymmetrical passive network connected in direct mode and then in reverse mode, and using these measurements to compute the Sparameters of the network. The free parameters of the calibration standards are estimated by minimizing a figure of merit based on the expected equality of the S-parameters of the network when used in direct and reverse modes. The capabilities of the method are demonstrated through simulations, and real measurements are used to estimate the actual offset delay of a 50-Ω calibration load that is assigned zero delay by the manufacturer. The estimated delay is 38.8 ps with a 1σ uncertainty of 2.1 ps for this particular load. This result is verified through measurements of a terminated airline. The measurements agree better with theoretical models of the airline when the reference plane is calibrated using the new estimate for the load delay.

Results from EDGES High-band. I. Constraints on Phenomenological Models for the Global 21 cm Signal

“…The observed nighttime and night-tonight reflection stability is better than ±0.01 dB and ±0.1 • . This stability is comparable to the intrinsic uncertainty in the VNA reflection measurement (Monsalve et al 2016(Monsalve et al , 2017. Therefore, we average all 29 hours of nighttime measurements from the session to derive our fiducial antenna reflection coefficient.…”

“…We set the input of the receiver as the reference plane for absolute antenna temperature measurements. We calibrate the sky measurements at this plane using six receiver parameters obtained in the laboratory before deployment (Rogers & Bowman 2012;Monsalve et al 2016Monsalve et al , 2017. During laboratory calibration and operation in the field, the receiver is maintained at a nominal temperature of 25 • C using active control.…”

“…It has placed the most significant lower limit on the duration of reionization to date, of ∆z > 0.06 at 95% confidence (Bowman & Rogers 2010a). Ongoing developments in instrumentation and calibration have improved the performance of the system, as well as enabled EDGES to contribute to the characterization of astronomical foregrounds and Earth's ionosphere (Rogers & Bowman 2008, 2012Rogers et al 2015;Monsalve et al 2016;Mozdzen et al 2017;Monsalve et al 2017). EDGES currently operates two total power spectral radiometers, identified as Low-Band and High-Band, which cover the ranges 50 − 100 MHz (27.4 z 13.2) and 90 − 190 MHz (14.8 z 6.5), and nominally target the features from First Light and the reionization, respectively.…”

CALIBRATION OF THE EDGES HIGH-BAND RECEIVER TO OBSERVE THE GLOBAL 21 cm SIGNATURE FROM THE EPOCH OF REIONIZATION

“…VNA calibration involves measuring three reflection standards at the VNA measurement plane: an open standard, a short standard, and a 50 Ω standard. As part of the EDGES efforts to increase the accuracy in calibration measurements, we improved upon the manufacturer-specified VNA tolerances through more accurate modeling of the 50 Ω standard (Blackham & Wong 2005;Scott 2005;Ridler & Nazoa 2006;Monsalve et al 2016). With the improved model for the standard, the additive uncertainty in the magnitude of measured reflection coefficients was reduced to a s 1 linear voltage ratio of -10 4 , which is equivalent to 0.005 dB for a reference reflection of −15 dB.…”

Data Analysis for Precision 21 cm Cosmology

“…In many ways, the calibration requirements for global signal experiments are more extreme than those for interferometric experiments, since single-element experiments possess a noise bias (as discussed in Section 3.1) that must be well-characterized and subtracted. To achieve this level of calibration, experimental groups tend to rely on a combination of laboratory measurements (Rogers & Bowman 2012;Patra et al 2013;Monsalve et al 2016Monsalve et al , 2017, in situ measurements (Patra et al 2017), and principal component-based modelling from the actual data (Tauscher et al 2018b). Typically, the instrumental effects are calibrated out of the measurement by introducing nuisance calibration parameters.…”