Network Analyzer Calibration Research Articles

A calibration method for vector network analyzers using a line and three or more offset-reflect standards

Abstract This article proposes a method for two-port vector network analyzer (VNA) calibration that uses a line standard and three or more offset-reflect standards (LnΓ, where n is the number of offset-reflect standards and n ≥ 3). The reflection coefficient of the highly reflecting offset-reflect standards and the propagation constant of the transmission line are unknown for this calibration method, but they can be obtained in the process of calculating the VNA calibration error coefficients. In the LnΓ calibration method, the calibration fixtures are all equal in mechanical length. Therefore, compared with the thru-reflect-line (TRL) method, this calibration method is convenient when the test fixtures of both sides of the VNA are fixed or difficult to move during the measurement. To further simplify the experimental operation, a corrugated reflector is also designed. In this calibration method, only one corrugated reflector used as the offset-reflect standard is needed. Different offset-reflect standards are realized easily by changing the position on the microstrip line. The proposed LnΓ calibration method is accurate, which is proven by theoretical analysis, simulations, and measurements.

Connector effects and reference plane influence in the N-Type connector

In this paper we outline the impact of mixing slotted N-type and slotless N-type connectors during a vector network analyzer calibration. We want to point out that making precise measurements of typical transfer standards, while using both N-type jack connectors is very difficult, because of the reference plane shift. We performed simulations of the two connector jack geometries to estimate the impact on measurements of devices under test with either plug or jack interface. The influence of mixing slotted and slotless connectors is then validated through simple measurements, which can be easily repeated in many labs. The results show that mixing of slotted and slotless jacks adds errors in the same order of magnitude sometimes reported as measurement uncertainties by national metrology institutes.

Calibration-free method to study temperature dependence of microwave dielectric properties of nematic liquid crystals

ABSTRACTThe present article shows an original transmission-reflection-based method to characterise the microwave dielectric properties of liquid crystals. This new method offering broadband capabilities of transmission-reflection method without the need for vector network analyser calibration. It is based on two measurements in the frequency range: one measurement is performed with the empty cell, the other with the cell filled with the material. The analysis of the two recorded scattering matrices allows to eliminate all error terms and to extract real and imaginary parts of the complex dielectric constant. In this paper, we first present this method, its validation in comparison to other characterisation methods. Secondly, we present an appropriate measuring cell which allows measurements in the frequency range 26 GHz-40 GHz which is also well-suited for temperature-dependent measurements. This method is used to perform dielectric microwave measurements on 5CB liquid crystal. Finally, we discuss the temperature-dependent microwave dielectric properties (permittivity, losses and dielectric anisotropy).

Traceable S-parameter measurements up to 90 GHz in 1.35 mm coaxial

As part of a joint program three National Measurement Institutes around Europe—the National Physical Laboratory in the UK, the Physikalisch-Technische Bundesanstalt in Germany and the Laboratoire National de métrologie et d’essais in France—have each established new capabilities for the traceable measurement of S-parameters up to 90 GHz in the new 1.35 mm (E band) coaxial connector. Each institution has established their own measurement systems to access the full frequency band for the connector, utilising a variety of commercially available equipment and measurement setups. Each have also developed their own calibration techniques and verification methods using different vector network analyser calibration routines. These include optimised multi-line Through Reflect Line, multiple Offset Shorts Through and Short Open Load Reciprocal (SOLR) schemes. Uncertainties for each of these setups and calibration schemes were determined utilising theoretical models of the systems and calibration standards, or through verification methods, with different effects being derived from the dimensional characteristics for each of the different standards or verification artifacts. The different dimensional systems used to make these measurements were also developed and established previously as part of the same program. The last part of this exercise was a three-way intercomparison between the laboratories. The comparison involved the measurement of a set of four traveling standards, including both 1-port and 2-port as well as plug (male) and jack (female) devices, each with different reflection and transmission characteristics to better test and demonstrate the equivalence of the capabilities.

Methods and models of calibration of vector network analyzers

Currently, measurement devices and instruments operating in the microwave range are widespread. Therefore, the problem arises of periodic checks, verifications and calibrations of such devices and instruments. The task of minimizing the systematic measurement error is a key task when performing verification of measuring instruments, measuring systems and devices operating in the microwave range using vector network analyzers. Various methods and models for performing calibrations of a vector network analyzer for determining the scattering parameters of passive microwave devices are described. The analysis of calibration methods is carried out, recommendations for its applications are given.

Calibration of a Dual-Polarized Probe Using the 16-Term Calibration Model

A calibration method for square or circular waveguide-based dual-polarized probes is proposed based on the 16-term network analyzer calibration model, allowing systematic errors, such as polarization impurity and mismatches to be corrected. The unique issues associated with such a dual-polarized probe are discussed, namely, the difficulty in creating thru or delay calibration standards and known asymmetric reflect standards. A novel calibration procedure solving the 16-term calibration model is developed and proposed, which overcomes these issues by utilizing three known symmetric reflect standards, one unknown asymmetric reflect standard, and an optional unknown but reciprocal standard. Subsequently, two Ka -band (26.5–40 GHz), square-waveguide-based dual-circularly polarized probes are fabricated along with the required calibration standards, and the proposed calibration method is then applied and its efficacy verified. In addition, the ability of the calibration algorithm to correct for polarization impurity is demonstrated through synthetic aperture radar (SAR) measurements in conjunction with a sample containing a plurality of identical targets with different relative orientations.

A substitution method for nanoscale capacitance calibration using scanning microwave microscopy

This paper presents a calibration method and an uncertainty budget for capacitance measurements performed on micrometric size capacitors at microwave frequencies and nanometric resolution using a scanning microwave microscopy (SMM). The method applies the classical one-port vector network analyzer calibration for SMM using three known capacitance standards. These standards are established from a commercial calibration kit placed close to the microcapacitors in order to be calibrated. The calibration kit is composed of a large number of Metal-Oxide-Semiconductor (MOS) microcapacitors with capacitance values C ranging from 0.1 fF to 8.6 fF. Diligent selection criteria were established for the choice of the three capacitors. Their capacitance values were calculated from the AFM measured values of the area of the top electrodes and the dielectric thickness and considering the contribution of fringing fields. The combined type uncertainty on these calculated values amounts between 5% and 14% in relative value (uncertainty given at one standard deviation). The comparison between the capacitance values measured on calibration kit capacitors using the calibrated SMM and the calculated values show a good agreement for capacitances higher than 0.8 fF within uncertainties varying between 6% and 9%. For smaller capacitances, most of the observed deviations are not significant at two standard deviations. The uncertainties are mostly dominated by dimensional measurements and less importantly by unwanted capacitance effects. Based on these results, capacitances of two sets of microcapacitors were calibrated. The combined uncertainties vary from 14% to 7% for capacitances ranging from 0.1 fF to 3.1 fF respectively. The permittivity values of the dielectric layer of the two samples have been determined. They are found equal to 4.0 and 4.1 with a standard uncertainty of 0.6 and correlate with the expected value of 3.9.

An Alternative Experimental Determination of a Two-Port Dipolar Antenna Model

It has been shown previously that a symmetric antenna such as a dipole driven via a balun from a coaxial transmission line can be represented as a 3-terminal, 2-port network and that for vertically-polarized antennas operated near ground this network is asymmetric. An experimental approach for the determination of the values of the elements in this network representation has also previously been given. Although reasonably good agreement between simulation and experiment was obtained, the experimental procedure required three 1-port measurements and could not accommodate full error correction in the vector network analyzer (VNA) calibration. Therefore, we consider an alternative experimental approach for determining the network components of the 2-port antenna model. The new approach involves connecting both ports of the antenna simultaneously to the 2-port VNA via a dual coaxial cable and fully exploits the capabilities of a VNA including calibration and adapter removal. Both approaches are presented in detail and compared. Finally, the effect of ferrite choke beads on the coaxial feed transmission line on the equivalent network is investigated.

Establishing a New Form of Primary Impedance Standard at Millimeter-Wave Frequencies

This paper investigates the possibility of using layers of graphene to form primary impedance standards for millimeter-wave rectangular metallic waveguide. It is shown that standards with values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Y_{0}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2Y_{0,}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3Y_{0}$ </tex-math></inline-formula> can be produced by a monolayer, bilayer, or trilayer of graphene, respectively, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Y_{0}$ </tex-math></inline-formula> is the characteristic admittance of the waveguide. These standards could then be used in the calibration of vector network analyzers.

Scanning microwave microscope algorithm offers robust calibration method for doped semiconductors

One-port algorithm draws on classical vector network analyzer calibration to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample.

Scanning microwave microscopy applied to semiconducting GaAs structures.

A calibration algorithm based on one-port vector network analyzer (VNA) calibration for scanning microwave microscopes (SMMs) is presented and used to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample. This robust and versatile algorithm is instrument and frequency independent, as we demonstrate by analyzing experimental data from two different, cantilever- and tuning fork-based, microscope setups operating in a wide frequency range up to 27.5 GHz. To benchmark the SMM results, comparison with secondary ion mass spectrometry is undertaken. Furthermore, we show SMM data on a GaAs p-n junction distinguishing p- and n-doped layers.

A Unified Approach for Reformulations of LRM/LRMM/LRRM Calibration Algorithms Based on the T-Matrix Representation

This paper investigates a unified theory to derive vector network analyzer calibration algorithms based on the T-matrix representation, by which means the line-reflect-match (LRM), line-reflect-match-match (LRMM), and the line-reflect-reflect-match (LRRM) calibrations are formulated. The proposed calibration theory is more general than other versions of LRM, LRMM, and LRRM in that an arbitrary known two-port device can be used as the line standard L, rather than a perfect thru or transmission line. Experimental verifications of the proposed theory using on-wafer calibrations from 0.5 GHz to 110 GHz are given.

A Multireflect-Thru Method of Vector Network Analyzer Calibration

We present a new method for two-port vector network analyzer (VNA) calibration, which uses multiple offset-reflect standards and a flush thru connection. Offset-reflect standards consist of sections of the same uniform transmission line with different lengths, which are terminated with the same highly reflective load. The unknown propagation constant of the transmission line and the load reflection coefficient are then determined simultaneously with the VNA calibration coefficients. We compare our method with the multiline thru-reflect-line (TRL) method and show that both methods yield similar results. Our new multireflect-thru method is solely based upon dimensional parameters of the calibration standards. Therefore, like the multiline TRL method, it can be used to establish a traceable VNA calibration. Thus, the multireflect-thru method constitutes an alternative to the multiline TRL calibration in environments in which the use of transmission lines is troublesome, such as in the case of VNAs with very small coaxial and waveguide connectors. The multireflect-thru method is also useful in on-wafer measurements since it allows us to keep a constant distance between the probes, which reduces the impact of crosstalk and speeds up automated testing.

ACP Probe Measurement of On-Chip Strip Dipole Antennas at W Band

Two L- and T-shaped strip dipole on-chip antennas are designed and manufactured back-to-back in a single chip for 77 GHz operation. The antennas are measured for their reflection coefficients and radiation patterns at W band. It has been observed that measurements are highly influenced by the antenna placements and the ACP110-A-GSG-100 probe. To model the effect of air coplanar probe (ACP probe), a software calibration is performed similar to a network analyzer calibration, and then the antenna reflection coefficient is calculated using the modeled probe-fed antenna. The technique employs obtaining the probe ABCD matrix and then de-embedding from the simulation results to compare with measurements. The probe-fed simulated and measured reflection coefficients agree well for manufactured L and T antennas, which resonate at 86 and 81 GHz, respectively. There are resonance frequency shifts attributed to the ACP probe effect, and simulations show that antennas will operate at 79 GHz (L antenna) and 77 GHz (T antenna) in the absence of ACP probe. The results obtained are highly dependent on the ACP probe, antenna structure, and the environments/experiments on which the measurements are performed.

A novel inconsistency condition for 2-port vector network analyzer calibration

An inconsistency condition for 2-port vector network analyzer (VNA) calibration is presented.This inconsistency condition discussed the use of Reciprocal device and Line or Thru for calibration of 2-port VNA. Mathematical analysis is carried out. The experimental results are compared with well known calibration algorithms like Thru-Short-Delay, Thru-Reflect-Line, Short-Open-Load- Reciprocal, and Thru-Short-Match. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2372–2375, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27072

Multimode TRL Calibration Technique for Characterization of Differential Devices

In this paper, a new comprehensive analytical derivation and discussion of the multimode thru-relfect-line (TRL) calibration based on the new generalized reverse cascade matrices is presented. The advantage of the presented formulation is that it can account for certain symmetries in the measurement setup and reflect them in the symmetry of the derived relationships. The focus is on the two-mode case since this covers the majority of the practical applications. To demonstrate the effectiveness of the new formulation, the practical use of the multimode TRL calibration technique for de-embedding purposes is discussed. The common de-embedding assumptions such as reciprocity and symmetry are analyzed and their consequences on the multimode TRL calibration are discussed. It is shown that these assumptions applied to the embedding networks can reduce the requirements on the reflect standard. The use of the multimode TRL calibration technique for un-terminating purposes is discussed. It is demonstrated that in the special de-embedding case it is possible to completely characterize the partially leaky embedding networks. The problems of interpretation and re-normalization of the measured scattering parameters are also discussed. Finally, the on-wafer measurement results are presented that verify the multimode TRL approach for four-port vector network analyzer calibration and de-embedding of differential devices.

Extended Through-Short-Delay Technique for the Calibration of Vector Network Analyzers With Nonmating Waveguide Ports

The extension of the through-short-delay (TSD) technique to the calibration of two-port vector network analyzers (VNAs) with nonmating waveguide ports is reported. The method retains the well-known high accuracy of the basic TSD technique while it enables to calibrate VNAs using two waveguide ports with different cross sections. Comparisons with the reciprocal-short-open-load technique commonly adopted to calibrate VNAs with nonconnectable ports and with theoretical data are reported. The present method can be adopted as either a one- or a two-tier calibration technique.

Proposal of a slotted circular waveguide as an open-circuited standard for calibration of L-band network analyzers

This paper presents a slotted circular waveguide as an open-circuited standard structure. This device as well as its previous stages are simulated with a 3D FDTD program. The dimensions are based on estimations of the MM8048B1® open-circuited standard. The results obtained through a variational method and a static MoM simulation, when compared with those obtained by means of 3D FDTD simulation, are found to be in good agreement, especially in the L-band.

Propagation Constant of a Coaxial Transmission Line With Rough Surfaces

This paper describes the accurate calculation of the propagation constant of a precision coaxial transmission line with rough plated conductors. The results are compared with previous publications and with traceable measurements of 2.4- and 1.85-mm air lines. In contrast to all tested existing procedures the present algorithm's results agree simultaneously with the real and imaginary part of the measured propagation constant. In the new algorithm, the effects of roughness and plating are represented by perturbed material parameters of a smooth coaxial line problem. A highly accurate multiple multipole field solver is used for the computation of the perturbed material parameters. The differences between the predicted and the measured propagation constant of 1.85-mm air lines are less than 0.01% at 67 GHz. Such high-precision computations are needed for the specification of offset short standards for vector network analyzer calibration.

Electronic vector-network-analyzer verification [Application Notes

The National Institute of Standards and Technology (NIST) recently introduced a new electronic approach for verifying microwave vector- network-analyzer (VNA) calibrations with a single computer-controlled electronic verification artifact. The verification results are captured in easy-to-understand performance metrics that, unlike those derived from measurements of mechanical verification artifacts, are independent of the actual artifacts employed. The approach also verifies VNA calibrations more completely than was previously possible. Finally NIST's VeridiCal software automates the entire process and allows you to log results directly to NIST servers over the Internet or generate verification reports on site, greatly simplifying record keeping.