Kamil Staszek

Theoretical Limits and Accuracy Improvement of Reflection-Coefficient Measurements in Six-Port Reflectometers

A complete analysis of the influence of six-port reflectometer parameters on the measurement accuracy is presented. A theoretical limit of the reflection-coefficient measurement has been investigated and is derived analytically. Moreover, for a set of six-ports reported in the literature, the numerical analysis of magnitude and phase measurement errors in a wide range of reflection-coefficient magnitude is presented. Furthermore, the modified six-port reflectometer utilizing a 4 × 4 Butler matrix and featuring scalable circle center distribution is proposed, and its advantage is discussed. The impact of power detectors uncertainty on an arbitrary six-port calibration procedure is presented. The performance of the proposed reflectometer has been verified in a wide frequency range of 2-3 GHz by measurements of a reflection coefficient having small magnitude. The obtained results are in agreement with the theoretical predictions, confirming the usefulness of the presented analysis.

Broadband Measurements of

A novel application of 4

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-Parameters Utilizing 4

4 Butler matrices in a multiport measurement technique has been investigated. The proposed measuring system consists of two standard Butler matrices. By application of numerical procedure in measurement system calibration, an enhanced accuracy has been achieved. An influence of power detectors uncertainty and imperfect Butler matrix parameters on calibration procedure and measurement results has been investigated. The proposed measuring system has been verified by measurements of scattering parameters of two attenuators and a narrowband bandpass filter in frequency range of 2–3 GHz. It has been shown that the proposed system allows for achieving results corresponding closely to the measurements obtained with the commercial vector network analyzer.

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A six-port reflectometer providing an improved power distribution is proposed. The developed six-port network allows for a significant enhancement of the measurement accuracy without increasing the complexity of the reflectometers network. The proposed six-port has been theoretically analyzed, designed in a stripline technique with the use of single-section coupled-line directional couplers, and fabricated. For the experimental verification, the developed six-port has been utilized in reflection coefficient measurements in a wide frequency range, 2.5-3.5 GHz. The obtained results are very close to the reference values measured using a vector network analyzer. Furthermore, the same measurements have been performed utilizing the classical six-port reflectometer operating within the same frequency range. The comparison clearly shows that the proposed six-port reflectometer provides a significantly higher measurement accuracy with respect to the classical solutions.

4 Butler Matrices

A novel application of an 8 × 8 Butler matrix in broadband multiport measuring systems has been presented. The proposed measuring system consists solely of a single broadband 8 × 8 Butler matrix and only one isolator allowing for measurements of all S-matrix coefficients of any two-port device. It has been shown that the properties of the applied 8 × 8 Butler matrix allow to obtain high measurement accuracy, which has been estimated with a numerical procedure for a different number of applied power detectors. The improved analytical procedure of calibration necessary for the transmission coefficient measurement has been presented. Performance of the proposed measuring system has been experimentally verified in a wide frequency range of 2-3.5 GHz, by measurements of S-parameters of seven exemplary attenuators and a narrowband bandpass filter. The measurement results are very close to the values obtained with the use of a commercial vector network analyzer.

Six-Port Reflectometer Providing Enhanced Power Distribution

In the paper, the performance of the sampling algorithm as a measure that evaluates together the sampling cost and the sampling accuracy is introduced and analyzed. We define the sampling cost as a number of samples in a unit of time and respectively the sampling accuracy as the mean intersampling error. On the basis of the sampling scheme performance measure, we compare the pure send-on-delta scheme and the send-on-delta scheme with prediction because these sampling algorithms are developed on controlling the linear intersampling error. As shown on the basis of simulation results, the send-on-delta schemes with first or second-order prediction outperforms the classical periodic sampling, and the pure send-on-delta scheme.

Broadband Measurements of

A newly developed, low cost FMCW radar system for industrial applications operating in K band has been presented. The radar features interferometric capability, which gives it sub-millimeter accuracy in distance variation measurement. Moreover, the presented radar has fully embedded signal processing with real time monitoring capability, thus making the presented sensor suitable for fully autonomous operation. The radar performance has been experimentally verified. Mean accuracy better than 30 μm has been achieved in displacement measurement test. The obtained results in terms of high accuracy and high measurement repetition rate prove the radar capable of meeting rigorous requirements of applications like structural health monitoring or industrial process control.

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A concept of dual-band multibeam antenna arrays that allows for efficient utilization of a common aperture has been proposed. The presented antenna arrays allow for achieving N-independent beams pointing at N different directions at higher frequency and N-independent beams at lower frequency pointing at N/2 different directions and having two orthogonal polarizations. As feeding networks, novel modified Butler matrices (BMs) have been proposed in which directional couplers having different properties in two frequency ranges have been for the first time utilized. To confirm the theoretical analysis, a dual-band multibeam antenna array fed by a modified 4 × 4 BM has been developed operating in 2.4 and 5.2 GHz frequency ranges.

-Parameters With the Use of a Single 8

A new type of broadband 3 dB tandem coupler has been proposed featuring frequency characteristics of the resulting coupling similar to those of a classic 3 dB two-section asymmetric coupled-line directional coupler. The coupler is composed of two loosely coupled-line sections having electrical lengths close to quarter-wavelength connected by right-handed and left-handed transmission line sections. Theoretical analysis and design equations have been presented with an exemplary realization. Measurements of the manufactured tandem coupler operating at f0 = 1 GHz having wide operational bandwidth have been shown to validate the presented analysis.