A calibration free vector network analyzer

Recently, two novel single-port, phase-shifter based vector network analyzer (VNA) systems were developed and tested at X-band (8.2 - 12.4 GHz) and Ka-band (26.4 - 40 GHz), respectively. These systems operate based on electronically moving the standing wave pattern, set up in a waveguide, over a Schottky detector and sample the standing wave voltage for several phase shift values. Once this system is fully characterized, all parameters in the system become known and hence theoretically, no other correction (or calibration) should be required to obtain the reflection coefficient, (Γ), of an unknown load. This makes this type of VNA calibration free which is a significant advantage over other types of VNAs. To this end, a VNA system, based on this design methodology, was developed at X-band using several design improvements (compared to the previous designs) with the aim of demonstrating this calibration-free feature. It was found that when a commercial VNA (HP8510C) is used as the source and the detector, the system works as expected. However, when a detector is used (Schottky diode, log detector, etc.), obtaining correct Γ still requires the customary three-load calibration. With the aim of exploring the cause, a detailed sensitivity analysis of prominent error sources was performed. Extensive measurements were done with different detection techniques including use of a spectrum analyzer as power detector. The system was tested even for electromagnetic compatibility (EMC) which may have contributed to this issue. Although desired results could not be obtained using the proposed standing-wave-power measuring devices like the Schottky diode but the principle of calibration-free VNA was shown to be true --Abstract, page iii

CIRCUIT MODULES FOR BROADBAND CMOS SIX-PORT SYSTEMS

This dissertation investigates four circuit modules used in a CMOS integrated six-port measurement system. The first circuit module is a wideband power source generator, which can be implemented with a voltage controlled ring oscillator. The second circuit module is a low-power 0.5 GHz - 20.5 GHz power detector with an embedded amplifier and a wideband quasi T-coil matching network. The third circuit module is a six-port circuit, which can be implemented with distributed or lumped- lement techniques. The fourth circuit module is the phase sifter used as calibration loads. The theoretical analysis, circuit design, simulated or experimental verifications of each circuit module are also included

Novel and Simple High-Frequency Single-Port Vector Network Analyzer

Portable, accurate, and relatively inexpensive high-frequency vector network analyzers (VNAs) have great utility for a wide range of applications, encompassing microwave circuit characterization, reflectometry, imaging, material characterization, and nondestructive testing to name a few. To meet the rising demand for VNAs possessing the aforementioned attributes, we present a novel and simple VNA design based on a standing-wave probing device and an electronically controllable phase shifter. The phase shifter is inserted between a device under test (DUT) and a standing-wave probing device. The complex reflection coefficient of the DUT is then obtained from multiple standing-wave voltage measurements taken for several different values of the phase shift. The proposed VNA design eliminates the need for expensive heterodyne detection schemes required for tuned receiver-based VNA designs. Compared with previously developed VNAs that operate based on performing multiple power measurements, the proposed VNA utilizes a single power detector without the need for multiport hybrid couplers. In this paper, the efficacy of the proposed VNA is demonstrated via numerical simulations and experimental measurements. For this purpose, measurements of various DUTs obtained using an X-band (8.212.4 GHz) prototype VNA are presented and compared with results obtained using an Agilent HP8510C VNA. The results show that the proposed VNA provides highly accurate vector measurements with typical errors on the order of 0.02 and 1° for magnitude and phase, respectively

Spatial Vector Microwave Measurement

V této práci je představena nová interferometrická měřicí metoda pro měření koeficientu přenosu mezi dvěma anténami. Jestliže je přenos mezi anténami realizován odrazem od nějakého předmětu, lze metodu využít např. pro mikrovlnné zobrazování. Navržený systém obsahuje referenční větev obsahující anténu, která přímo ozařuje přijímací anténu a testovací větev, kde anténa ozařuje testovaný objekt. Elektromagnetická vlna z testovacího kanálu je od testovacího objektu odražena do přijímací antény, kde interferuje s vlnou z referenční větve. Pro jednoznačné získání fázového posunu mezi referenční a testovací vlnou jsou provedena postupně minimálně dvě interferometrická měření, kdy je v referenčním kanálu nastaven vhodný fázový posun a amplituda přenosu. Při měření můžeme provést více nezávislých interferometrických měření a vzniklá redundance může být využita ke zmenšení nejistot měření. Dále byl popsán způsob geometrické representace měření, který umožňuje názorně odhadnout nejisty měření. Nejistoty měření byly určeny i na základě numerické Monte Carlo metody. Navržená konfigurace byla ověřena jak přesným měřením za použití vektorového analyzátoru pro ověření nejistot měření, tak původní konfigurací pro ověření funkčnosti celého konceptu. Navrženou metodou bylo provedeno mikrovlnné zobrazování metodou inverzní syntetické apertury a byla tak ověřena použitelnost navrženého systému.This work presents a new interferometric measuring method for measuring the transmission coefficient between two antennas. If the transmission between the antennas is realized by a reflection from an object, the method can be used, e.g., for microwave imaging. The proposed system contains a reference branch containing an antenna that directly irradiates the receiving antenna and a test branch where the antenna irradiates the object under test. The electromagnetic wave from the test channel is reflected from the test object into the receiving antenna where it interferes with the wave from the reference channel. To achieve a unambiguous phase shift between the reference and test waves, at least two interferometric measurements are performed sequentially, with a suitable phase shift and the amplitude of the transmission being set in the reference channel. We can perform more independent interferometric measurements while redundancy can be used to reduce measurement uncertainty. Furthermore, a method of geometric representation of the measurement has been described which makes it possible to clearly estimate the measurement uncertainty. Measurement uncertainties were determined by the numerical Monte Carlo method. The proposed configuration has been verified by accurate measurements using a vector analyzer to verify measurement uncertainties, and the original configuration to verify the functionality of the entire concept. Microwave imaging using the inverse synthetic aperture method was performed to verify the usability of the proposed system

A Portable Microwave Interferometry Sensor for Permittivity Detection Based on CCMRC

© 2013 IEEE. A portable microwave complex permittivity sensor based on the interferometry configuration is proposed. A complementary compact microstrip resonant cell (CCMRC) is applied as the sensitive element, which converts the dielectric information of the material under test (MUT) into the phase variations of its transmission coefficient. A miniaturized interferometry platform based on a down-converting mixer further translates the phase change into DC output voltage variation, which can be readily recorded with a direct readout circuit. In this context, expensive and bulky vector network analyzer is no longer needed, thereby leading to a low hardware cost. With comprehensive theoretical analysis, the material permittivity is simply extracted using a specific extrapolation algorithm. As a proof of concept, several different solid material samples with known permittivity values are used to verify the devised detection system

Investigation of RF Direct Detection Architecture Circuits for Metamaterial Sensor Applications

Recent advances in metamaterials research has enabled the development of highly sensitive near-field microwave sensors with unprecedented sensitivity. In this work, we take advantage of the increase in the sensitivity to produce a compact, lightweight, affordable, and accurate measurement system for the applications of microwave imaging and material characterization. This sensitivity enhancement due to the inclusion of metamaterials opens the door for the use of inexpensive microwave components and circuits such as direct detectors while leveraging the high sensitivity of the metamaterial probe to deliver an overall accurate measurement system comparable to that of a traditional probe used in conjunction with a vector network analyzer. The sensor developed is composed of a metamaterial sensor with an RF direct detection circuit. In this work, two prototype measurement systems have been designed and tested. Measurement of small cracks in conductors and material characterization using the proposed system were performed. The results from the newly developed sensors were compared with the results from vector network analyzer measurements. Good agreement was obtained. The feasibility of a compact, lightweight, affordable, and accurate system has been demonstrated by using the developed prototypes

Modifying design of four-port couplers for enhanced six-port reflectometer performance

Ph.DDOCTOR OF PHILOSOPH

Millimeter-Wave Multi-Port Front-End Receivers: Design Considerations and Implementation

This chapter covers recent achievements on the integrated 60 GHz millimeter-wave front-end receiver based on the multi-port (six-port) concept. For this purpose, the design procedure of a fully integrated 60 GHz multi-port (six-port) front-end receiver implemented on a thin ceramic substrate (εr = 9.9, h = 127 μm) using an miniature hybrid microwave integrated circuit (MHMIC) fabrication process is presented in detail. All components constituting the proposed front-end receiver including an 8 × 2 antenna array, a low-noise amplifier (LNA), a six-port circuit, and the RF power detectors are presented and characterized separately before they are integrated into the final front-end receiver prototype. The performance of the latter has been experimentally evaluated in terms of various M-PSK/M-QAM demodulations. The obtained demodulation results are very satisfactory (the constellation points for all considered M-PSK/M-QAM schemes are very close to the ideal locations), demonstrating and confirming the high ability of the proposed 60 GHz millimeter-wave six-port front-end receiver to operate as a high-performance quadrature demodulator, without any calibration, for modulation schemes up to 32 symbols

Investigations of an On-body Reflectometer Probe

Radar can be utilized to detect the mechanical heart activity and is a potential alternative to today’s heartbeat monitoring techniques in medicine. It can detect details of the heart activity, such as filling and ejection of heart chambers and opening and closing of heart valves. This is due to the radars ability to detect movements and direction of motion. Compared to electrocardiogram and ultrasound it has the advantage that it is a contactless measurement. The objective of this thesis is the development of a proof-of-concept prototype of a novel microwave on-body sensor for heartbeat detection, which can be used inside an MRI system and which could provide prospective triggering information. The main idea is to use a microwave sensor (reflectometer) with an on-body antenna illuminating the heart and detecting the reflected signal. The measurement is based on the evaluation of the heart-related time-dependent reflection coefficient of the antenna, by minimizing the static and respiration-related components of the reflection coefficient. In a first step, this is done by minimizing the antenna mismatch with an automatic impedance matching circuit after the placement of the antenna on the chest of an individual; the antenna mismatch is dependent on the position and the individual body properties. In a second step the residual static and slow variation signal from respiration is suppressed by a canceller circuit (well-known from CW radar technology as reflected power canceller). With the reflectometer sensor system consisting of a CW signal generator (transmitter, Tx), on-body antenna, adaptive impedance matching circuit and demodulator circuit as part of the reflected signal canceller, the performance of each component influences the performance of the sensor system. Thus, the thesis concentrates on the design of the circuits and the antenna but also investigates the wave propagation scenario of the sensor applied to a human chest. The signals measured with the microwave sensor are compared with a standard measurement method for heart activity, a heart sound measurement. This is used in order to assess the obtained signal and relate the signal states to certain heart states. The measured radar signals are found to be sensitive to position of the sensor, the individual and the posture of the individual, making the interpretation of the signals challenging

Simultaneous Data Communication and Power Transfer Technique with Multiport Interferometric Receiver

RÉSUMÉ Le problème de la communication est généralement présenté comme un problème de trans-mission d’un message généré d’un point a un autre. Certains systèmes de communication modernes sou˙rent de contraintes énergétiques sévères. Avec le développement rapide des systèmes électroniques sans fil de faible puissance, d’innombrables activités de recherche ont été menées en vue d’explorer la faisabilité d’une alimentation à distance ou sans fil de ces systèmes. Par conséquent, la transmission d’énergie sans fil (WPT) est en cours de développe-ment en tant que technique prometteuse pour alimenter des appareils électroniques à distance et pour prolonger la durée de vie des réseaux sans fil à contrainte d’énergie. Parmi les éner-gies renouvelables récoltées dans l’environnement, les signaux RF rayonnés par les émetteurs peuvent être une ressource viable pour le transfert d’énergie sans fil, tandis que les signaux RF ont été largement utilisés comme véhicule pour la transmission d’informations sans fil (WIT). Par conséquent, le transfert simultané d’informations et la plateforme de transfert de puissance sans fil (SWIPT) deviennent bénéfiques, car il réalise les deux utilisations utiles des signaux RF en même temps et il o˙re ainsi potentiellement une grande commodité aux utilisateurs mobiles. L’antenne redresseuse, qui combine des fonctionnalités du redresseur et de l’antenne, est un élément clé pour la transmission et la récolte d’énergie sans fil. L’eÿcacité de conversion du circuit de redressement détermine les performances globales de l’antenne redresseuse. Par conséquent, pour concevoir une antenne redresseuse à haute eÿcacité qui peut garantir la qualité d’un système WPT, il convient de se concentrer davantage sur l’investigation, l’analyse et le développement de redresseurs axés sur les performances en référence à une eÿcacité de conversion radio fréquence à courant continu. D’un autre côté, les circuits redresseurs peuvent simplement récupérer l’énergie et ils ne peuvent pas décoder le signal transmis pour fins de communication. Cependant, la transmission de données est une exigence essentielle des systèmes de communication sans fil. Par conséquent, si la capacité de détection et de traitement du signal peut être ajoutée à une architecture antenne redresseuse, un récepteur avec transmission de puissance sans fil et communication de données simultanées peut être réalisé. Ce mémoire vise à étudier et à démontrer un récepteur de multifonction et de multiport qui a la capacité de collecter simultanément l’énergie sans fil et les données de communication fonctionnant à la fréquence des microondes.----------ABSTRACT The problem of communication is usually cast as one of transmitting a message generated at one point to another point. Some modern communication systems are known to suffer from severe energy constraints and power consumptions. With the rapid development of low power wireless electronic systems, countless research activities have been carried out to explore the feasibility of a remote or wireless powering of those systems. Therefore, wireless power transmission (WPT) is being developed as a promising technique, for powering electronic devices over distance and for prolonging the lifetime of energy constrained wireless networks. Among the renewable energy harvested from the environment, the RF signals radiated by transmitters can be a viable resource for wireless power transfer, while RF signals have been widely used as a vehicle for wireless information transmission (WIT). Therefore, simultaneous wireless information and power transfer (SWIPT) platform becomes appealing since it realizes both useful utilizations of RF signals at the same time, and thus potentially offers great convenience to mobile users. The rectenna, combining the functionalities of rectifier and antenna, is a key element for wireless power transmission and harvesting. The conversion efficiency of the rectifying circuit determines the overall performance of the rectenna. Therefore, to design a high-efficiency rectenna that can guarantee the quality of a WPT system, more focus should be concentrated on the investigation, analysis and development performance-driven rectifiers with reference to high RF-to-DC conversion efficiency. On the other hand, rectenna circuits can just scavenge energy and they cannot decode the transmitted signal for communication purpose. How-ever, the data transmission is an essential requirement of wireless communication systems. Therefore, if the ability of signal detection and processing can be added to a rectenna architecture then a multi-function receiver with simultaneous wireless power transmission and data communication can be realized.This dissertation aims to investigate and demonstrate a multi-function and multi-port receiver with the capability of simultaneous wireless energy harvesting and data communication operating at microwave frequency. To achieve these goals, it becomes interesting when a single receiver chain is able to convert the RF power to DC power, while at the same time converting the RF modulated signal to BaseBand (BB) signal. Therefore, the fundamental methodology to receive and convert the RF signal to BB while simultaneously harvesting power is derived and analyzed in this work