Yansheng Xu

New-Wave Radio

Radio communications in the past century have relied primarily on nonlinear devices to modulate and demodulate signals for wireless transmissions. This article reviews initial laboratory results obtained with new radios using linear interferometers to modulate and demodulate ultra-wide-band (UWB) signals. Automotive and chip fabrication industries apply such interferometers in new commercial radios for UWB communications.

Theoretical and experimental study of measurement of microwave permittivity using open ended elliptical coaxial probes

In this paper, a new kind of coaxial probe for measurement of microwave permittivity-an open-ended elliptical aperture-is studied from theoretical and experimental viewpoints. Calculated results are discussed and compared with experimental values. Wideband measurements of the dielectric constants of liquids are performed by using this kind of needle type probe. Both theory and experiment show that open-ended elliptical coaxial probes can be successfully used in wideband dielectric constant measurements with the advantage of increased sensitivity, especially at low frequencies. Moreover, this kind of probe can easily be fitted into gels and living tissues. These features are very important in biological applications both for measurements and microwave radiation treatment. >

An efficient method for study of general bi-anisotropic waveguides

In this paper, coupled-mode equations for general bi-anisotropic waveguides with perfect electrically conducting (PEG) walls are studied and a set of rigorous expressions is obtained. The features of these equations are discussed and applications to circular/rectangular Faraday chiral and chiral waveguides are demonstrated. Comparisons between Faraday chiral, chiral, and ferrite-filled waveguides are also given. >

Design of Multiway Power Divider by Using Stepped-Impedance Transformers

In this paper, the design of multiway power dividers by interconnecting power dividers with fewer output ports is studied by transforming them into multisection stepped-impedance transformers. By using this approach, it is easy to design multiway power dividers with required equal ripples of input reflection (S11 ) within a wide passband. The interconnecting lines can be used as additional matching sections to improve the input matching. General properties of this type of multiway power dividers can be easily obtained. Design of multiway power divider with required input reflection level can be readily performed by using the published data and tables of stepped-impedance transformer in the literature. Both even- and odd-mode analyses are performed to obtain the optimal isolation resistor values. A prototype of a wideband four-way power divider with a rhombic architecture is designed, fabricated, and measured. Simulation and measurement results are in good agreement and validate the proposed approach.

Six-port digital receivers (SPDRs): A new design approach

A new SPDR design approach is proposed. The receier contains an RF discriminator, power detectors, a signal leel comparison circuit, a decoder, and data and carrier recoery circuits for BPSK and QPSK signals. The new receier operates solely on analog circuits, and the proposed design isalidated with circuit and system simulations of an RF discriminator and a Costas-type phase-locked loop, demonstration of a demodulator at 2.4 GHz, and MMIC fabrication of an RF discrimina- tor at 15 GHz. The new design approach offers interesting possibilities to achiee SPDR-on-a-chip. Q 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 356)360, 2000.

THz POWER DIVIDER CIRCUITS ON PLANAR GOUBAU LINES (PGLs)

Terahertz spectroscopy is a new tool for real time biological analysis. Unfortunately, investigations on aqueous solutions remain di-cult and need to work on nanovolumes. Integrated Terahertz instrumentation remains a challenge. We demonstrate that Planar Goubau Line (PGL) technology could bring a real practical solution to reach this goal. This study provides the design, fabrication and test results of passive PGL components like loads and power divider. These PGL components are designed, simulated, fabricated and measured with a Vectorial network analyser (VNA). Simulation and test data support PGL component designs. PGL components operate over a wide frequency range from 0.06 to 0.325THz.

ON THE REAL-TIME CALIBRATION OF () SIX-PORT RECEIVERS SPRs

In this paper, a study of the simplification of real-time () calibration of six-port receiers SPRs is gien. A simple, real-time calibration procedure is proposed using the incoming QPSK signal as the calibration standard. Only two systems of four linear equations are necessary to be soled in the calculation of the calibration parameters. This calibration procedure is especially suitable for QPSK reception. Modulation errors will be cancelled if the receied signal is selected for the calibration standards. SPW simulation results of 64 QAM signal receptionalidate the proposed calibration procedure. Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 318)322, 1999.

A new six-port circuit architecture using only power dividers/combiners

In this paper, a novel architecture of six-port circuit is proposed and experimentally verified. The six-port circuit is realized by using only power dividers and combiners of Wilkinson type. This architecture is proposed for the first time and opens new perspective for applications in the THz and optical region for both communication and measurements. A prototype operating in the ultra-wideband frequency region has been fabricated and experimentally verified, to show its performance as modulator/demodulator for applications in software-defined radios.

A novel structure of tightly coupled lines for MMIC/MHMIC couplers and phase shifters

In this paper, a new structure of tightly coupled lines compatible with monolithic-microwave integrated-circuit/miniature hybrid-microwave integrated-circuit (MMIC/MHMIC) technology is introduced. Different from previous designs, short subsections of two or more different coupled lines are alternatively connected together to achieve the needed performance of a single-section coupler or phase shifter. Theoretical calculations are given and some typical design data are provided. A design example of a wide-band coplanar-waveguide (CPW) quadrature coupler using standard MMIC foundry technology is provided. Only metal-insulator-metal (MIM) capacitors and air-bridges are used to achieve tight coupling-no via holes are necessary. Experimental results are in good agreement with simulations. The proposed structure of coupled lines is very flexible and easily achieves very tight coupling factors.

A technique for efficient analysis of planar integrated microwave circuits including segmented layers and miniature topologies

A method-of-lines based technique is presented for efficiently analyzing propagation problems of planar integrated circuits. A scheme of vertical multi-subregion space discretization is used to enhance numerical accuracy by improving most of the edge singularity on metallic conductors. On the other hand, this proposed approach is able to not only handle very narrow strips/very large slots topology or vice-versa, but also simulate exactly bilaterally unbounded structures with possible segmented multilayers. Numerical results including convergence characteristics are demonstrated for both quasi-static and hybrid-mode analysis. Comparison with other publications validates this novel algorithm. >