Microwave Network Analyzer Research Articles

Optical vector network analyzer as a reflectometer

An optical vector network analyzer similar to that of the microwave network analyzer has been shown to be feasible for the evaluation of optical components. It is shown that this instrument can also be used as a reflectometer. Heterodyne mixing and small linewidth lasers with a large tunable range make it a flexible tool for optical device evaluation and design. Experimental results are presented.

On the design and performance of electrically small printed thick film YBa/sub 2/Cu/sub 3/O/sub 7-x/ antennas

Strip material and substrate losses, that occur at the radiating element and the feeding-matching network of electrically small printed YBa/sub 2/Cu/sub 3/O/sub 7/spl minus/x/ (HTS) antenna systems, can substantially degrade their performance and, therefore, have to be considered in optimum efficiency and SNR designs. Identification and numerical estimation of such loss mechanisms, and assessment of the overall efficiency of the antenna system, which is of particular importance in design, is facilitated by fundamental microwave network analysis and the method of moments (MM). Four efficient designs, incorporating different feeding-matching configurations, are experimentally tested, and their performance is compared with the theoretical predictions. Superior gain can be demonstrated over similar supercooled Cu and Ag antennas. The applicability of low frequency efficiency measurement methods for highly efficient HTS antenna systems is outlined and extended for improved accuracy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Permittivities of Fresh Fruits and Vegetables at 0.2 to 20 GHz

Permittivities, moisture contents, tissue densities, and total soluble solids data were determined for samples of twenty-three kinds of fresh fruits and vegetables at 23 degrees C. Permittivities were measured at 41 frequencies between 200 MHz and 20 GHz with an open-ended coaxial-line probe and a microwave network analyzer. Results of the permittivity measurements are presented graphically, and dielectric constant and loss factor values at six frequencies across the range are tabulated along with sample descriptions and moisture, density, and total soluble solids data. Although specific values differ, the dielectric constant decreases steadily with increasing frequency, dropping more rapidly at frequencies above 5 GHz. Values for the loss factor decrease as frequency increases above 200 MHz to a broad minimum in the 1- to 3-GHz region and then increase again as the frequency approaches 20 GHz. The dielectric behavior of the fruit and vegetable tissues appears to be influenced by ionic conductivity and bound water relaxations at the lower frequencies and by free water relaxation at the higher end of the frequency range.

Microwave Permittivities of Fresh Fruits and Vegetables from 0.2 to 20 GHz

Procedures are described for microwave permittivity measurements taken on 23 kinds of common fresh fruits and vegetables with an open-ended coaxial-line probe used in conjunction with a microwave network analyzer. Plots of the dielectric constant and loss factor at 41 frequencies between 200 MHz and 20 GHz are illustrated for apple, lemon, carrot, cucumber, and avocado, and condensed data for all, along with moisture content, tissue density, and total soluble solids, are tabulated at six frequencies covering the same range. Although specific values differ, the dielectric constant decreases steadily with increasing frequency, dropping more rapidly at frequencies above 5 GHz. Values for the loss factor decrease as frequency increases above 200 MHz to a broad minimum in the 1- to 3-GHz region and then increase again as the frequency approaches 20 GHz. The dielectric behavior of the fruit and vegetable tissues appears to be influenced by ionic conductivity and bound water relaxations at the lower frequencies and by free water relaxation at the higher end of the frequency range.

Symbolic analysis of large-scale microwave networks

A new and efficient method of symbolic analysis of the interconnection of microwave networks which are characterised by the wave-scatter matrices is presented. By taking advantage of unique topological properties of the networks, a rather simplified SFG (referred to as compact SFG (signal flow graph)) is introduced with which the effective symbolic products combination can be determined with great simplicity and clarity so that large-scale microwave networks can be treated. An augmented network principle is also derived so that all the elements of the wave-scatter matrix of the connected network can be obtained in one implementation.

Using microwave network analyzer and MSW-SER to measure linewidth spectrum in magnetic garnet film from 0.5 to 20 GHz

A measurement technique, based on the combination of a modern network analyzer and wide-band-tunable magnetostatic wave straight-edge resonators (MSW-SERs), is used to automatically measure the linewidth ( Delta H) in yttrium iron garnet (YIG) epilayers at 0.5-20 GHz. Smith chart and voltage standing wave ratio methods are used to determine the half resonance band ( Delta omega ). Delta H value is calculated from Delta omega using resonance conditions of MSW-SERs. A system with insertion loss <0.07 dB and return <-50 dB is set up by an improved calibration. Four pieces of YIG films with thicknesses of 9-120 mu m and magnetization of 370-1750 Gs are examined in the range 0.5-20 GHz. The results measured at 9.2 GHz agree well with those obtained by ferromagnetic resonance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Admittance characteristics of narrow radiating slots in nonradiating dielectric waveguide

A study of an inclined slot cut in the metal wall of nonradiative dielectric (NRD) waveguide is presented. The modal expansion method is applied to the development of an equivalent network of a slot discontinuity in NRD waveguide, using the reciprocity and Poynting theorems. The effect of the metal wall thickness is taken into consideration by applying microwave network analysis. Numerical data for the normalised slot admittance is obtained and compared with experimental results. Good agreement is observed. Numerical data for the slot admittance for various dielectric materials is also presented and the radiation patterns of a single slot are included.

Wave computations for microwave education

The analysis of even simple microwave circuits can involve complicated calculations. It is argued that students repeatedly forced through this exercise are left exhausted and never develop understanding and insight into the principles of high-frequency circuit design. The use of computer-aided design software eliminates the network analysis burden, but it is a precarious solution: students easily become dependent on software and never develop analytical skills. A simple wave computational approach to microwave network analysis is discussed. The method is derived from Mason's theory of signal flow graphs and is based on wave variables and scattering parameters. The approach is easily understood and applied as either an analytical tool, or within a microwave CAD analysis engine. PC software using this computational technique is described and its educational applications are discussed. >

An electro-optic laser probe at low temperature for the characterization of planar integrated microwave resonators

An electro-optic crystal probe has been used to measure noninvasively the strength of the electric stray field of coplanar λ/2-resonators at about 6GHz. Resonators have been structured from a single layer of the high temperature superconductor Y Ba 2 Cu 3O 7- x as well as from copper. The spatial electric field distribution along the resonator lines shows the expected functional behavior. Field mapping however, requires that the vertical probe position is maintained with great accuracy. From the measurements of the field strength versus frequency the resonator quality factors can be determined. Good agreement with measurements carried out with a microwave network analyzer has been found.

S-parameter analysis of multiconductor, integrated circuit interconnect systems

The authors explore the use of S-parameter-based network techniques for the analysis of coupled, multiconductor, high-speed analog and digital integrated circuit interconnects. S-parameter-based computer-aided design (CAD) techniques, widely used in microwave network analysis, provide a powerful framework for the analysis of analog and digital integrated circuit interconnect systems. The specific additions to the existing S-parameter network analysis framework developed provide for multiport interconnect capabilities and for the use of multiconductor S-parameters derived from three categories of input parameters: (1) lossy quasi-static R,L,C and G; (2) lossy frequency-dependent (dispersive) R,L,C,G; and (3) the propagation constants, characteristic impedance, and conductor eigencurrents, derived from full-wave electromagnetic analysis. Results are compared with computed simulations and experimental measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A W-band homodyne vector network analyzer with variable measurement port distance

A homodyne network analyzer is presented that covers the frequency range from 92 to 100 GHz. The W-Band waveguide setup consists of two identical measurement heads, one of which is movable in order to accommodate devices under test (DUT's) of arbitrary length. The millimeter wave signal is fed to the moving head through a novel quasi-optical line stretcher. A new calibration procedure has been de- veloped for the special setup. I. INTRODUCTION OMMERCIALLY available vector network analyzers C (VNA's) for the millimeter waveguide bands are based on the heterodyne principle with harmonic downconversion. The necessary components (microwave network analyzer, two mi- crowave sources with at least one of them synthesized, har- monic mixers, low-noise amplifiers, etc.) are very expensive. A homodyne analyzer that requires only a single source and a comparatively small microwave setup may be a cost-effective solution for measurement tasks where the necessary frequency coverage does not exceed a waveguide band. Former homodyne designs (l), realized as a waveguide setup, suffer from unflex- ible line lengths. The requirement of adapting a DUT to the VNA by special waveguides has been eliminated by making one of the measurement heads movable and feeding the signal to it through a quasi-optical line stretcher. Furthermore, the design presented here allows the measurement of all S-parameters' without reversing the DUT.

Microwave Properties of Cascaded Arbitrarily Oriented Metallic Gratings and of Gratings Cascaded with Lossy Dielectric Slabs

The theory of scattering matrices and microwave network analysis are employed to solve the problem of scattering from two cascaded infinite gratings with variable orientation at the second layer. The total reflection and transmission coefficients are calculated as functions of the angle of incidence, orientation of the second layer, distance of layer separation and grating size. Furthermore, the problem of cascading a grating with a lossy dielectric is formulated and solved. The Secant-Corrector Spectral Iteration method is used as a numerical technique for calculating the desired currents and fields. Finally, calculated values of the reflection and transmission coefficients are presented and compared with reported experimental and theoretical data.

The microwave circuit model of Josephson junction at liquid nitrogen temperature

We have measured the microwave characteristics of Josephson junction at liquid nitrogen temperature by using microwave network analyser. Based upon these experimental results we present a microwave circuit model of Josephson junction at liquid nitrogen temperature and calculate the parameters of microwave circuit model of Josephson junction.

Planar multiport microwave network analysis by the finite element method

P. Silvester (1973) described a finite element method that combines geometrical flexibility with a partial-fraction representation of the admittance matrices of the general N-port. His method was demonstrated for a rectangular strip. However, to the author's knowledge the method has never been demonstrated on other two-port networks or on multiport planar microwave circuits. Frequency-dependent admittance, impedance and scattering matrices are obtained here for complicated two-port planar circuits, using Silvester's method. Comparison with other methods and measurements is made where possible. The reasons why this method is not in widespread use are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transit frequency of fast Si self-aligned bipolar transistors

The small-signal current gain beta of fast Si self-aligned transistors is measured up to the transit frequency f/sub T/ using a 26.5-GHz microwave network analyzer system and special HF measuring probes. The influence of parasitic transistor elements such as the base-collector junction capacitance, the internal base resistance, and the peripheral transistor was confirmed in a real transistor at high frequencies by measurements on transistors with different emitter areas. The two-dimensional effects, which deviate from the expected one-pole frequency behavior of beta , can be described by the extended transistor model, namely the intrinsic model and the peripheral model. >

A unified mathematical approach to two-port calibration techniques and some applications

A rigorous mathematical treatment of microwave network analyzer calibration and de-embedding procedures for the two-port error network representation is used in order to explain current calibration techniques in a succinct and homogeneous manner. It is demonstrated that the essence of through-delay de-embedding techniques consists in the use of two known two-port calibration standards to obtain pairs of similar matrices for the input and output error adapters. Once the characteristic vectors for these matrices are obtained, a number of different approaches can be used in order to solve for the scaling constants. >

Network analyzer calibration using offset shorts

Microwave network analyzer accuracy enhancement by offset shorts is investigated. Usable calibration bandwidth and accuracy limitations are determined by applying a previously published model by L.A. Glasser (1978) to the case of a reference short and two offset shorts. Data necessary to emulate the HP 8510 scalar network analyzer are derived and used in the model to provide realistic projections. Convenient techniques for optimizing experimental accuracy and for obtaining an estimate of the uncertainty in actual short circuit and offset short calibration standards are also presented. >

Elf: computer automation and error correction for a microwave network analyzer

A microwave measurement system has been developed that combines a personal computer (PC) and an conventional vector network analyzer to yield a full complex-error-corrected automatic network analyzer. The system consists of a Hewlett-Packard HP 8410C network analyzer, an HP 8350B sweep oscillator, and an IBM PC. A program called Elf runs on the PC, performing calibration and measurement algorithms and providing a flexible, menu-oriented user interface. The system, when calibrated, achieves a worst-case measurement error vector of magnitude <or=0.02 for transmission and reflection coefficient measurements over the 2-12.4-GHz frequency range and has a measurement speed of three frequency points/s. Elf provides an inexpensive method for upgrading the HP 8410 to achieve the high accuracy of an automatic network analyzer.<<ETX>>

Scattering from stacked gratings and dielectrics for various angles of wave incidence

The theory of scattering matrices and microwave network analysis is used to solve the problem of scattering from cascaded infinite periodic gratings. The total reflection and transmission coefficients are calculated as functions of angle of incidence, wire spacing for each grating separation, wire thickness, and number of gratings that comprise the cascaded structure. The problem of stacking dielectric slabs with periodic gratings is also formulated and solved. In all cases, the secant corrector spectral iteration approach is used as a numerical method for calculating the desired currents and fields. Finally, the calculated values of the reflection and transmission coefficients are presented and compared with reported experimental and theoretical data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Frequency response of AlInAs/GaInAs/InP modulation-doped field-effect transistors at cryogenic temperatures

The microwave S-parameters of MODFETs have been measured at 300 and 90 K up to a frequency of 26.5 GHz. Measurements were made using a microwave network analyzer and a probe station that was modified for liquid-nitrogen-cooled operation. The MODFET layers included an Si-doped Al/sub 0.48/In/sub 0.52/As barrier and an undoped Ga/sub 0.47/In/sub 0.53/As channel grown by molecular-beam epitaxy on a semi-insulating InP substrate. Results indicate a striking difference between the high-frequency responses at the two temperatures. At low frequencies the gain is higher at 90 K, where the maximum unilateral gain G/sub u/ at 1 GHz is 28 dB at 90 K vs. 20 dB at 300 K. At 300 K, G/sub u/ rolls off at 6 dB/octave and the maximum frequency of oscillations f/sub max/, is 51 GHz. However, at 90 K, the gain roll-off steepens to 12 dB/octave and f/sub max/ is only 21 GHz. The roll-off in current gain is 6 dB/octave at both temperatures, and the current gain cutoff frequency, f/sub T/, is 33 GHz at 300 K and 41 GHz at 90 K. It was found that GaInAs MODFETs can have a lower frequency response at cryogenic temperatures than at room temperature. The measured 12 dB/octave roll-off rate of G/sub u/ indicates a second pole in the device response function.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>