Microwave Test Fixtures Research Articles

An improved two-tier L-L method for characterizing symmetrical microwave test fixtures

An improved two-tier L-L method for characterizing symmetrical microwave test fixtures is introduced in this paper. The improved two-tier L-L method is implemented with two uniform transmission lines having the same characteristic impedance and propagation constants, but different lengths. The ABCD parameters of the test fixture and the embedded device under test (DUT) can be determined by measurements of the two lines and the DUT. To validate the improved L-L method, the two-tier thru-reflect-line (TRL) calibration technique is used. High correlation between the S-parameter data de-embedded with the TRL and with the proposed two-tier L-L validates the method. Moreover, the improved L-L method is not only useful for characterizing the test fixture, but is also useful for determining the line characteristic impedance. The main advantage of the two-tier L-L method over the two-tier TRL is the number of calibration elements. The former method uses two and the latter method uses three.

Calibrating an Arbitrary Test Fixture for a Symmetric Device by Three Measurements

In this paper, a general solution of calibrating a microwave test fixture for a symmetric device is deduced from the cascading network relation, and it exposes the probability and condition of calibrating an arbitrary test fixture for a symmetric device by three measurements, which is less than the times of measurements in the thru-reflect-line (TRL) method. The scattering parameters of the test fixture and the embedded symmetric device can be determined by measurements of a thru, a line, and the symmetric device. Furthermore, the method is analyzed and verified by simulation and measurement. The analysis indicates that the presented method is suitable for determining the calibrated S-parameters of a symmetric device under test (DUT).

Choice of calibration equations in calibrating microwave test fixtures

The error theory of linear equation system has been applied to the calibration procedure of microwave network analyser in this article. A new explanation for the choice of the linear calibration equations is proposed and a general principle for choosing calibration equations is presented. The method can also be used to predict the occurrence of the problem of frequency limitation at some periodic frequencies. This principle is employed to the thru-short-delay (TSD) method and the solution using the chosen equations gives the most accurate results. A good agreement between the theory and the experiment has been obtained.

Calibration of microwave network analyzer

This paper presents a systematic description of the methods for calibrating microwave network analyzer and test fixtures, and discusses the problems arising in the calibration. The general criteria for choosing calibration standards and corresponding algorithms are discussed and suggestions to overcome these problems and improve the calibration accuracy are also given. It has been found that for reciprocal test fixtures, the four equations obtained with the thru standard can be used at the same time. Meanwhile, the calibration accuracy can be improved. It has been shown that using the same calibration procedures but different algorithms may lead to the occurrence of frequency limitation.

Frequency limitation in the calibration of microwave test fixtures

The problem of frequency limitation arising from the calibration of asymmetric and symmetric test fixtures has been investigated. For asymmetric test fixtures, a new algorithm based on the thru-short-match (TSM) method is outlined. It is found that the conventional TSM method does not have any inherent frequency limitation, but using the same procedure with an unknown match may lead to the said problem. This limitation can be avoided by using a different algorithm. The various calibration methods for symmetric test fixtures using known standards are also discussed and the origin of the frequency limitation is identified. Several ways in avoiding the problem are proposed. There is good agreement between the theories and experimental data.

New algorithms of the TSM and TOM methods for calibrating microwave test fixtures

AbstractBased on the conventional through‐short‐match (TSM) method, an improved TSM method has been proposed in this Letter. This method gives an analytical solution and has almost all the advantages of conventional TSM methods. For example, it has no phase uncertainty and no bandwidth limitation. The experimental results show that the accuracy can be significantly improved with this method. The proposed theory can be applied to the through‐open‐match (TOM) method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 26–31, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10363

Phase uncertainty in calibrating microwave test fixtures

The problem of phase uncertainty arising in calibration of the test fixtures is investigated in this paper. It is shown that the problem exists no matter what kinds of calibration standards are used. It is also found that there is no need to determine the individual S-parameters of the test fixtures. In order to eliminate the problem of phase uncertainty, three different precise (known) reflection standards or one known reflection standard plus one known transmission standard should be used to calibrate symmetrical test fixtures. For the asymmetrical cases, three known standards, including at least one transmission standard, should be used. The thru-open-match (TOM) and thru-short-match (TSM) techniques are the simplest methods, and they have no bandwidth limitation. When the standards are imprecise (unknown), it is recommended to use any suitable technique, such as the thru-reflect-line, line-reflect-line, thru-short-delay, thru-open-delay, line-reflect-match, line-reflect-reflect-match, or multiline methods, to accurately determine the values of the required calibration terms and, in addition, to use the TOM or TSM method with the same imprecise standards to resolve the phase uncertainty.

De-embedding and unterminating microwave fixtures with nonlinear least squares

A general method of characterizing microwave test fixtures for the purpose of determining the parameters of devices embedded in the fixture is discussed. The technique was used to investigate deembedding under the assumptions that all measurement errors are random and normally distributed and that the standards are distributed uniformly around the Smith chart. It was shown that for any given number of standards, the greatest accuracy under these assumptions is achieved by utilizing a large set of known reflective loads. When the propagation constant and the reflection coefficients of the standards are not known, then equal numbers of thru lines and reflective loads give the highest accuracy, although not as high as when the propagation constant and reflection coefficients are known. The accuracy of the technique was studied and compared with that of the common open-short-load (OSL) and thru-reflect-line methods. The OSL technique was found to be considerably less accurate than using sets of offset reflective loads.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Improved microwave test fixture for brittle substrate materials

A microwave test fixture has been designed and built to hold brittle substrate materials, such as GaAs, without inducing damage. The substrate pressure is adjustable and easily controlled by the use of compression springs. Tests have shown that the holder does not damage GaAs substrates, and produces repeatable and reliable measurements.