Two-port Vector Network Analyzer Research Articles

MEASUREMENTS OF PLANAR MICROWAVE CIRCUITS USING AN IMPROVED TRL CALIBRATION METHOD

In this paper, an improved TRL (Thru-Re∞ect-Line) calibration method is presented. This method is based on ten-term error model of a two-port vector network analyzer(VNA) measurement system. Eight error terms induced by flxtures as well as two leakage errors are derived directly from the S parameters of the calibration standards measured from the coaxial reference plane without converting S parameters to T parameters. To validate our algorithm, a microstrip device with a via hole and a coplanar waveguide transmission line are fabricated and calibrated using the present TRL calibration method and Engen's algorithm, respectively. The magnitudes and phases of S11 and S21 of the devices are compared. The consistency of the de-embedded results with those calibrated by Engen's TRL algorithm illustrates the validity of the TRL algorithm in this paper.

Measurement of Noncoaxial Multiport Devices Up to the Intrinsic Ports

Even in light of all the multiport vector network analyzers (VNAs) that appear to be on the market at present, the measurement of noncoaxial multiport devices remains a critical challenge due to the lack of a multiport counterpart of the two-port thru-reflect-line (TRL) calibration. Accordingly, based on the concept of virtual auxiliary termination and the two-port TRL calibration technique, a scattering matrix reconstruction procedure is developed for the use of a two-port VNA to characterize noncoaxial multiport devices up to the intrinsic ports located at the ends of the planar transmission lines such as microstrips, coplanar waveguides, and substrate integrated waveguides (SIWs). The four-port scattering matrix of a 60-GHz SIW 0-dB coupler for experimental validation is reconstructed. The final results are in agreement with not only the simulation results, but also the fully corrected TRL results.

An Error Analysis of the Scattering Matrix Renormalization Transform

By characterizing the condition number as an indicator of accuracy, an error analysis is performed to determine how different auxiliary terminations affect the accuracy of the scattering matrix renormalization transform. Such an error analysis plays an essential role in enhancing the accuracy and widening the applicability of the port renormalization method for measuring multiport devices with a two-port vector network analyzer.

Focus on test and measurement

Focus on test and measurement

Evaluation of Measurement Uncertainties Caused by Common and Cross Modes in Differential Measurements Using Baluns

Two-port vector network analyzers can be used for measuring differential circuits by integrating baluns. However, due to the imperfection of the baluns, measurement uncertainties occur even under the most accurate calibration conditions. These uncertainties are caused by the common and cross modes of the baluns and the device-under-test. This paper proposes a new algorithm, which evaluates these measurement uncertainties, by using a few sets of assumptions that can approximately correspond to the worst conditions in which the common and cross modes maximally affect the measurements. The proposed algorithm can be used in post measurement processes by which the users can be informed of their measurements' uncertainties.

Two-Port Vector Network Analyzer Measurements Up to 508 GHz

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present new results for a two-port vector network analyzer swept-frequency test set for the 325–508 GHz frequency band. The calibrated dynamic range performance in the full frequency band is discussed. Using a line–reflect–line calibration procedure, the dynamic ranges for return and insertion losses of better than <formula formulatype="inline"><tex>$-$</tex></formula>20 and <formula formulatype="inline"><tex>$-$</tex></formula>35 dB, respectively, are achieved. We examine the performance of the calibrated test set for the first time by measuring S-parameters of passive waveguide components and comparing data with electromagnetic simulations. </para>

A New Characterization and Calibration Method for 3-dB-Coupled On-Wafer Measurements

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A two-port vector network analyzer (VNA) can be used for measuring the differential-mode (or common-mode) <formula formulatype="inline"><tex>${ S}$</tex> </formula>-parameters of an integrated circuit by combining on-wafer probes with 3-dB-coupling baluns (or power splitters). In such a measurement setup, the error networks from each port of the VNA to the device-under-test are three-port rather than the conventional two-port. This paper proposes a new set of an impedance standards and algorithm that can efficiently extract the full nine mixed-mode <formula formulatype="inline"><tex>${ S}$</tex></formula>-parameters of the three-port error network. For differential-mode measurements, the four differential-mode <formula formulatype="inline"><tex>${ S}$</tex></formula>-parameters are used for the calibration and the remaining five common- and cross-mode <formula formulatype="inline"><tex>${ S}$</tex></formula>-parameters are used for evaluating their associated measurement errors. By a minor variation, the proposed method can be used for characterizing the full nine mixed-mode <formula formulatype="inline"> <tex>${ S}$</tex></formula>-parameters of the 3-dB-coupler embedded probe itself, providing a valuable tool in its development stage. The proposed method uses a pseudoinverse of an overdetermined matrix, by which it becomes tolerant to errors that occur when measuring the impedance standards. </para>

Marchand Balun Embedded Probe

Planar-type Marchand baluns are embedded into on-wafer probes in order to provide accurate differential measurement capabilities for conventional single-ended measurement equipments such as the two-port vector network analyzer. In designing the planar-type Marchand balun, the values for differential- and common-mode characteristic impedances of the coupled transmission lines are analytically derived by using general transmission line theories. The derived characteristic impedances are realized using a double-sided single-layer printed circuit board surrounded by conductive fixtures. The proposed coupled transmission line structure provides convenient port interfaces to the coaxial cables and it is free from bond wires and vias, enabling one to achieve high cost efficiency and reproducibility.

A Novel Calibration Algorithm for a Special Class of Multiport Vector Network Analyzers

A new error model for a special class of multiport vector network analyzers (VNAs) is presented in this paper. This model can be applied to multiport network analyzers with noncomplete reflectometers, i.e., when the measurement of the incident waves at each port is not always available. The method used to compute the error coefficients proposed here is based on a compact and easy formulation. This method is an extension of the already existing general theory for complete reflectometer multiport network analyzers. Furthermore, the new error model generalizes the theory for three-sampler two-port VNAs. The proposed model has been tested against the complete reflectometer one and exhibits the same accuracy level.

Multiport Measurement Method Using a Two-Port Network Analyzer With Remaining Ports Unterminated

A practical multiport measurement method is presented for the precise characterization of an N-port device using a two-port vector network analyzer. Because the 2 unused ports need not be terminated with matched loads, a test fixture can be simplified. Any influence of the reflections from the unterminated ports can be deembedded by port renormalization. The proposed method was verified with a coupled microstrip line structure.

Virtual Auxiliary Termination for Multiport Scattering Matrix Measurement Using Two-Port Network Analyzer

Almost all methods for measuring the scattering matrix of an n-port device with the use of a two-port vector network analyzer (VNA) require one to terminate the other n - 2 ports in the fully characterized auxiliary terminations and prefer auxiliary terminations with small or moderate reflection coefficients. In this paper, a technique is presented to measure the auxiliary terminations indirectly. It not only eases the measurement of auxiliary terminations, but also makes the concept of virtual auxiliary termination realizable. In practice, examples of virtual auxiliary terminations can be the inherent connectors or bonding pads of the test device. Also studied is the remedy for the numerical pitfall possibly coexisting with the use of strongly reflecting auxiliary terminations such as virtual auxiliary terminations. The scattering matrix of a four-port circulator is then acquired accordingly from measurements using a two-port VNA and virtual auxiliary terminations.

Differential Circuit Characterization with Two-Podt S-Parameters

This article was written to help practicing RF engineers solve everyday tasks related to differential circuit characterization with precise and reliable methods, which employ ordinary single-ended two-port vector network analyzers. The article describes useful, practical methods for balanced circuit characterization, particularly differential voltage, common-mode rejection (CMR), insertion loss, and differential impedance based on measuring two-port S-parameters

Two-Port Vector Network Analyzer Measurements in the 218–344- and 356–500-GHz Frequency Bands

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We discuss methods for full two-port vector network analyzer measurements in the 218–344- (using WR3) and 356–500-GHz (using WR2.2) frequency bands. Waveguide test sets (WR3 and WR2.2) utilize Oleson Microwave Laboratories Inc. frequency extenders with the Agilent 8510C network analyzer. On-wafer measurements in the 220–325-GHz band are demonstrated with GGB Industries Inc. coplanar-waveguide probes. This paper primarily reviews the performance capabilities of the WR3 test set and introduces initial calibration results of the WR2.2 test set. For WR3, calibration methods are compared, and dynamic range and frequency extender output power data are presented. </para>

Investigation of a method to improve VNA calibration in planar dispersive media through adding an asymmetrical reciprocal device

If a passive asymmetrical reciprocal device is used in addition to short open load thru standards in a two-port vector network analyzer calibration, systematic errors in the calibration kit parameters can be reduced dramatically through numerical optimization to minimize asymmetry after correction. The method is described and the quality of correction assessed using simulated data. Measured results are then presented for calibration on a printed circuit board. Encouraging results and practical limitations are discussed.

Multiport method for the measurement of the scattering parameters of N-ports

The multiport method for the precise measurement of the scattering parameters of N-port devices with a two-port vector network analyzer (VNA) is presented. The scattering parameters of an N port cannot be measured directly with a two-port VNA if N>2. Only the scattering parameters of all two-port combinations of the device-under-test (DUT) are measurable. Thereby, the measured two-port scattering parameters strongly depend on the external terminations of the DUTs ports, which are not connected to the VNA during the measurements. In order to eliminate the influences of these external possibly reflective terminations, an error correction has to be performed. In comparison to known correction methods, the multiport method has some advantages. Firstly, the external terminations can be chosen arbitrarily, i.e., short and open circuits are realizable as long as the topology of the DUT allows it. Secondly, the terminations, except for one, can be unknown, leading to a reduction of the inconsistency problem caused by erroneous data of the external terminations, which is also known from the calibration of VNAs with completely known calibration standards. The good performance of the multiport method is shown by measured results.

Pure-mode network analyzer concept for on-wafer measurements of differential circuits at millimeter-wave frequencies

A measurement concept based on a two-port vector network analyzer has been developed, which enables pure-mode on-wafer measurements of differential circuits in the millimeter-wave frequency range. An error model for the measurement system is derived as required for future calibration algorithms. Based on WR15 waveguide components, together with 1.85-mm coaxial probes, a setup has been built and its amplitude and phase imbalances have been characterized in the frequency range from 50 to 65 GHz.

Port reduction methods for scattering matrix measurement of an n-port network

The port reduction method (PRM) is a method to acquire the scattering matrix of an n-port network from the scattering matrix measured at a reduced port order by terminating certain ports. This then relaxes the instrumentation requirement and calibration procedure. As the port order is reduced to two, the scattering matrix of an n-port network can be obtained from the measurement using a conventional two-port vector network analyzer. In this paper, we describe two novel PRMs, which can reduce the order of measured ports to two. The experimental results show good accuracy. These two PRMs can provide a simpler calibration procedure and instrumentation than those directly using an n-port network analyzer. In addition, they give more accurate results than those measured by a two-port network analyzer with the assumption of using ideal terminators.

A novel vector network analyzer

A calibration procedure for a perturbation two-port vector network analyzer is presented. It consists of a variable perturbation two-port placed between a device-under-test and a scalar network analyzer. A measured vector reflection coefficient is determined on the basis of amplitude-only measurements. A full correction of systematic errors is possible. The new principle was experimentally confirmed in the frequency band up to 14 GHz. The results enable prediction of an add-on for scalar analyzers, enabling vector measurements.