Six-port Reflectometer Research Articles

A Six-Port Reflectometer Calibration Using Wilkinson Power Divider

A new calibration method for a six-port reflectometer which minimizes the effect of power measurement errors is presented. It is based on the power divider correlator to obtain estimates of the six-port calibration constants. The calibration procedure is to determine the constants that govern the operation of the six-port from the measurement of power or output ports tensions by placing five to eleven standard loads in succession to DUT. A load and four offset shorts are used as reflection standards. Computer simulation results are presented to show that the described procedure substantially reduces the overall error in the calibration constants.

ENHANCED FIVE-PORT RING CIRCUIT REFLECTOMETER FOR SYNTHETIC BREAST TISSUE DIELECTRIC DETERMINATION

In this study,a Six-port Reflectometer (SPR) with dielectric probe sensor is used to predict relative dielectric,er of normal and tumorous breast tissue in frequency range from 2.34GHz to 3.0GHz. Other than that,a superstrate with an exterior copper layer is overlaid on the surface of a primitive Five-port Ring Circuit (FPRC),which is also a denominated,enhanced superstrate FPRC. It is the main component of the SPR and is presented in this paper as well. The enhanced superstrate FPRC is capable of improving its operating bandwidth by 26% and shifting the operating centre frequency to a lower value without increasing circuit physical size. The detailed design and characteristics of the FPRC are described here. In addition,the enhanced superstrate FPRC is integrated into the SPR for one-port reflection coefficient measurement. The measurement using the SPR is benchmarked with Agilent’s E5071C Vector Network Analyzer (VNA) for one-port reflection coefficient. Maximum absolute mean error of the linear magnitude and phase measurements are recorded to be 0.03 and 5.50°,respectively. In addition,maximum absolute error of the predicted dielectric and loss factor are 1.77 and 0.61,respectively.

Six-Port Reflectometer Providing Enhanced Power Distribution

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 reflectometer’s 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.

Development of a Symmetric Ring Junction as a Four-Port Reflectometer for Complex Reflection Coefficient Measurements

Six-port reflectometer is well-known for its abil- ity to measure magnitude and phase-shift of microwave signal using four power detectors that perform magnitude- only measurements. This paper presents the development of an innovative symmetric ring junction as four-port re- flectometer for complex reflection coefficient measure- ments. It reduces the number of required detectors to two. Design optimization, new calibration modeling and algo- rithm are discussed in details for this four-port reflectome- ter. The developed four-port reflectometer is compared to five-port reflectometer and vector network analyzer. It is found that the measured magnitude and phase-shift show good performance in comparison with the commercial vector network analyzer and the five-port reflectometer.

Measurement Accuracy Enhancement in Six-Port Reflectometers

A new algorithm improving measurement accuracy in six-port reflectometers, applicable also for arbitrary multiport reflectometers, is proposed. The developed procedure does require neither additional measurements nor modifications of the measuring system. The introduced weighting coefficients allow for enhancement of the measurement accuracy using the same power measurements as in classic solutions. The proposed theory has been confirmed experimentally by the measurements of reflection coefficient within a wide frequency range 2–4 GHz.

Differential six‐port reflectometer for determining dry rubber content of latex

This study presents the application of a differential six-port reflectometer to the design of a portable system for measurement of the dry rubber content (DRC) of latex. The proposed DRC measurement system consists of a 1 GHz reflectometer used with an open-ended coaxial-probe sensor, a temperature sensor, a display and a microcontroller. The complex permittivity and temperature of the rubber latex are measured, and a temperature-dependent model for DRC determination based on a dielectric mixture theory is used. The reflectometer performance is verified by comparing the measured complex permittivity with the results obtained from a commercial dielectric measurement system. Finally, the accuracy of the DRC measurement system is assessed by comparing the measured DRCs from different latex samples over the range of 10–40°C with the standard oven-drying method.

The Circuit and Network Analysis of Some Signal Separation Structures Constituting Microwave Six-Port Reflectometers

The circuit and network analysis of some signal separation structures constituting a microwave six-port reflectometer are presented. An interconnection of five of these structures composing a six-port network analyzer is also presented. In order to validate the responses, a circuit analysis following the signals from source to detectors, is performed. The complete structure constituting the six-port network analyzer is composed by a 6 dB directional coupler, a four stage 3 dB Wilkinson power divider and three quadrature couplers providing 3 dB, which are formed by two 8.34 dB tandem couplers.

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.

Microwave-Based Noninvasive Concentration Measurements for Biomedical Applications

A Debye relaxation model for the permittivity of aqueous glucose solution is given up to 40 GHz. Measurements of aqueous solutions are compared with invasive measurements on over 40 blood samples. Reflection- and transmission-based techniques are explained, concerning the application in biomedical concentration measurements. Wideband measurements on different sensing structures are introduced. Reflection- and transmission-based sensors are applied to a six-port reflectometer, as well as a homodyne vector network analyzer.

Embedded RF Test Circuits: RF Power Detectors, RF Power Control Circuits, Directional Couplers, and 77-GHz Six-Port Reflectometer

Modern integrated circuits (ICs) are becoming an integrated parts of analog, digital, and radio frequency (RF) circuits. Testing these RF circuits on a chip is an important task, not only for fabrication quality control but also for tuning RF circuit elements to fit multi-standard wireless systems. In this paper, RF test circuits suitable for embedded testing are introduced: RF power detectors, power control circuits, directional couplers, and six-port reflectometers. Various types of embedded RF power detectors are reviewed. The conventional approach and our approach for the RF power control circuits are compared. Also, embedded tunable active directional couplers are presented. Then, six-port reflectometers for embedded RF testing are introduced including a 77-GHz six-port reflectometer circuit in a 130 nm process. This circuit demonstrates successful calibrated reflection coefficient simulation results for 37 well distributed samples in a Smith chart. The details including the theory, calibration, circuit design techniques, and simulations of the 77-GHz six-port reflectometer are presented in this paper.

Six-port-based compact and low-cost near-field 35 GHz microscopy platform for non-destructive evaluation

A complete millimeter-wave solution with features such as low cost, low-power consumption, compactness, robustness and easy-to-use is proposed to address the need of non-destructive methods with sub-wavelength resolution for operation outside a laboratory environment. The measurement system is based on the association of a low-cost 35GHz six-port reflectometer and an inexpensive and easy-to-build microstrip evanescent probe with an apex size of 10μm. The instrumentation can find applications for example in the microelectronic industry where the fast diagnosis of metal layer deposition is of great interest. For demonstration purposes, the technique is applied to the near-field mapping of thin metal layers with a spatial resolution of a few microns. In particular, one-dimensional scanning of rectangular inclusions and imaging of a microsized metallic pattern processed into silicon are experimentally demonstrated to validate the technique. The usefulness and versatility of the method make it also suited for a wide range of applications.

Analysis and Design of a Differential Sampled-Line Six-Port Reflectometer

The analysis and design of a differential six-port reflectometer (SPR) based on a sampled-line structure is presented in this paper. The practical differential SPR is realized in Coplanar Strip (CPS) transmission line form, using two baluns for interfacing with the RF source and device under test (DUT) and four baluns connected to the RF logarithmic detectors. The performance of the proposed differential SPR structure is evaluated with a common-mode rejection ratio analysis and impedance measurement. A prototype differential SPR was designed and fabricated at 1 GHz in order to verify the analysis. Measurement results for various load impedances are compared with the measured results obtained from a commercial automatic vector network analyzer. It is shown that the differential structure gives a significant advantage in rejecting common-mode interference signals.

Single-Frequency-Based Dry Rubber Content Determination Technique for In-Field Measurement Application

In this paper, it is shown that extensive characterization and modeling of dielectric permittivity of rubber latex enables dry rubber content (DRC) to be accurately determined using a measurement at a single microwave frequency. The model is demonstrated in a low-cost sensing system based on a six-port reflectometer that is suitable for application in the field. To develop an accurate model, a wide range of samples (with the DRC in the range 28%–61%) is first measured using the Agilent Technologies 85070E dielectric probe system for a range of frequencies and at temperatures from 15 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> to 39 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> . This data is then used to determine the parameters of a dielectric mixture model, which is based on the assumption that rubber latex is a diphase liquid consisting of the water and solid rubber. To take the effect of temperature and signal frequency on the molecular polarization behavior into account, the dielectric permittivity of the water is described using a Debye-type relaxation spectral function; and the frequency-dependant polarization parameter of neighboring inclusions is applied to the dielectric mixture model. After determining all the model parameters, it is then shown that the measurement of the sample's temperature and dielectric permittivity at a single frequency is sufficient to determine the DRC with a high degree of accuracy. Compared with the measurements made with the standard oven-drying method, using a single 2.5 GHz measurement the technique exhibits 0.36% DRC of mean absolute error with 0.28% DRC standard deviation, over the temperature range 15 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex> </formula> –39 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> . Finally, the technique is implemented with a six-port reflectometer. The measurement system employing the model is applied and tested with several fresh rubber latex samples. A wide range of measured results confirm the validity of the technique.

60-GHz Near-Field Six-Port Microscope Using a Scanning Slit Probe for Subsurface Sensing

A new six-port based near-field millimeter-wave microscope using a scanning slit probe is proposed for subsurface sensing applications. The combination of a six-port reflectometer and a slit probe presents a viable and promising alternative to the costly heterodyne principle. The system presents advantages such as compactness, robustness, and low cost. To evaluate its performance, the spatial resolution is experimentally verified.

Formulation for Complete and Accurate Calibration of Six-Port Reflectometer

An accurate technique for six-port reflectometers calibration is presented in this paper. The method based on a spatial Fourier analysis incorporates nonlinearity and mismatching effects as a part of the calibration procedure. The technique makes use of impedance data distributed on the whole Smith chart to increase the measurement accuracy. A straightforward least square algorithm is used to fully calibrate the six-port reflectometer. Experimental data in the millimeter-wave frequency range is provided to validate the technique.

In situ measurements of complex permittivity and moisture content in oil palm fruits

An in situ measurement system for oil palm fruit's permittivity and moisture content determination is presented. The instrumentation is includes a six-port reflectometer and an open ended coaxial probe which operates at 2 GHz. The developed system was tested and compared with the data obtained using commercial dielectric measurement probe and mixture model. This system is found to be practical for in situ measurement as well as fast and cost effective for oil palm fruit's properties and quality inspection.

Using the Monte Carlo approach to study effects of power measurement uncertainties on six-port reflectometer performance

Monte Carlo simulations have been employed to evaluate the effects of power-measurement uncertainties on the performance of six-port reflectometers (even when known to operate under less-than-optimum specifications). The numerical results compiled in the present study provide additional insights that are useful for the design of six-port reflectometers. The practical utility of the simulation software has also been demonstrated for a prototype reflectometer (implemented in microstrip form with modified branch-line couplers) which is able to yield measurement accuracies of ±0.01 and ±2° for the magnitude and phase, respectively, of a planar component's reflection coefficient from 4.6 GHz to 5.9 GHz.

Integrated Optical Six-Port Reflectometer in Silicon on Insulator

The six-port reflectometer technique enables simple and accurate measurement of optical reflection coefficients in both magnitude and phase. The reflection coefficient is computed from four power measurements of linear combinations of the waves incident and reflected from the device under test. While the six-port technique is very successful at microwave frequencies and conceptually related to coherent optical phase diversity receivers, no optical implementations have been reported so far. In this paper, we present an experimental characterization of an optical six-port reflectometer composed of three multimode interference couplers, fabricated with a single etch step in silicon on insulator. Measurements are performed using a novel technique with a simple setup. The six-port combines the incident and reflected waves with magnitude and phase errors less than plusmn0.5 dB and plusmn6deg in the 1485-1575 nm band.

New Baseband Radio Channel Impulse Processing Algorithms

The method for radio channel pulse response processing with baseband conversion by six-port reflectometer technique is described. The received signal is converted by baseband conversion, digitized and the pulse response of radio channel is processed by proposed algorithms. These algorithms are working in real time and are able to estimate the amplitude, phase and delay of the received signal in each of propagation paths. The most promising algorithm (Exponential Power Descend Algorithm) achieved recovery successfulness of all signal paths equal approximately 90 % for SNR = 2.5 dB. Ill. 9, bibl. 11 (in English; summaries in English, Russian and Lithuanian).

Measurements of Complex Dielectric Constant of Ferroelectrics with Six-port Reflectometer in 80–120 GHz Frequency Range

In the present work six-port reflectometer suitable for the dielectric measurements in the frequency range 80–120 GHz is described. Complex dielectic constant is very difficult to obtain the higher is the value and the higher the frequency of measurements. Presented method is presented with superior calibration method, which implies higher precision. In this paper, results of actual measurements of relaxor ceramics PLZT 8/65/35 and comparison to previous work are presented.