Topic
Standing wave ratio
About: Standing wave ratio is a research topic. Over the lifetime, 6576 publications have been published within this topic receiving 54422 citations. The topic is also known as: SWR & voltage standing wave ratio.
Papers published on a yearly basis
Papers
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TL;DR: In this article, three types of single-feed circularly polarized microstrip antennas, namely, a diagonal fed nearly square, a truncated-corners square and a square with a diagonal slot, are presented.
Abstract: Analysis and optimized designs are presented of three types of single feed circularly polarized microstrip antennas, namely, a diagonal fed nearly square, a truncated-corners square and a square with a diagonal slot. The Green's function approach and the desegmentation methods are used. The resonant frequencies are calculated for two orthogonal modes which together yield circular polarization. Optimum feed locations are determined for the best impedance match to a 50 \Omega coaxial feed line. Axial-ratio bandwidths, voltage standing-wave ratio (VSWR) bandwidths and radiation patterns are evaluated and verified experimentally.
602 citations
TL;DR: In this article, an analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented, where the input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes.
Abstract: An analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented. The input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes. A zero decibel directional coupler is described and its possible use as a duplexer is proposed. The design of multiple stub directional couplers for any degree of coupling is discussed. A method of computing the bandwidth of all these couplers is outlined, and the bandwidth curves, the power out the various arms with respect to frequency of the zero decibel coupler, are computed. A tabulation is made for six different 3 db couplers (even-power split) and their standing wave ratio, evenness of power split and isolation of the fourth arm as a function of frequency assuming perfect performance at the band center.
471 citations
TL;DR: In this article, the feasibility of an electrically small transformer with two sections and capable of achieving ideal impedance matching at two arbitrary frequencies is demonstrated analytically, and the exact solution to the resulting transcendental transmission-line equations for two sections is obtained with no restrictions.
Abstract: One of the most useful transmission-line constructs is the quarter-wave transformer that is used to impedance match a line at a single frequency f/sub 0/. The feasibility of an electrically small transformer with two sections and capable of achieving ideal impedance matching at two arbitrary frequencies is demonstrated analytically. To achieve this, the exact solution to the resulting transcendental transmission-line equations for two sections is obtained with no restrictions. The parameters of the transformer are presented in explicit closed form, and are exact. The results of this study are useful for a number of practical design problems, including dual-band antennas and RF circuits in general. In particular, feasibility of ideal operation at the important first harmonic frequency 2f/sub 0/ is demonstrated.
420 citations
TL;DR: In this paper, the authors present the non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory.
Abstract: Electrically-small antennas present high-Q impedances characterized by large reactances and small radiation resistances. For such antennas, the effectiveness of passive matching is severely limited by gain-bandwidth theory, which predicts narrow bandwidths and/or poor gain. With receivers, the inability to resolve this impedance mismatch results in poor signal-to-noise (S/N) ratio, as compared to using a full-size antenna. With transmitters, the consequence is poor power efficiency. However, in many applications full-size antennas are impractical, and a means is required to effectively match their electrically-small counterparts. This paper presents the technique of non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory. We first review the origins and development of non-Foster impedance matching, and then present experimental results for the non-Foster impedance matching of electrically-small dipoles and monopoles. For receivers, our best measurements on the antenna range demonstrate up to 20 dB improvement in S/N over 20-120 MHz; for transmitters, we show a power efficiency improvement which exceeds a factor of two over an 5% bandwidth about 20 MHz with an average signal power of 1 W to the radiation resistance.
349 citations
Book•
01 Jan 2000
TL;DR: This chapter discusses RF Behavior of Passive Components, which consists of RF Transistor Amplifier Designs, and an Overview of RF Filter Design, which focuses on Filter Implementation.
Abstract: 1. Introduction. Importance of Radiofrequency Design. Dimensions and Units. Frequency Spectrum. RF Behavior of Passive Components. Chip Components and Circuit Board Considerations. Summary. 2. Transmission Line Analysis. Why Transmission Line Theory? Examples of Transmission Lines. Equivalent Circuit Representation. Theoretical Foundation. Circuit Parameters for a Parallel Plate Transmission Line. Summary of Different Line Configurations. General Transmission Line Equation. Microstrip Transmission Line. Terminated Lossless Transmission Line. Special Termination Conditions. Sourced and Loaded Transmission Line. Summary. 3. The Smith Chart. From Reflection Coefficient to Load Impedance. Impedance Transformation. Admittance Transformation. Parallel and Series Connections. Summary. 4. Single- and Multiport Networks. Basic Definitions. Interconnecting Networks. Network Properties and Applications. Scattering Parameters. Summary. 5. An Overview of RF Filter Design. Basic Resonator and Filter Configurations. Special Filter Realizations. Filter Implementation. Coupled Filter. Summary. 6. Active RF Components. Semiconductor Basics. RF Diodes. Bipolar-Junction Transistor. RF Field Effect Transistors. High Electron Mobility Transistors. Summary. 7. Active RF Component Modeling. Diode Models. Transistor Models. Measurement of Active Devices. Scattering Parameter Device Characterization. Summary. 8. Matching and Biasing Networks. Impedance Matching Using Discrete Components. Microstrip Line Matching Networks. Amplifier Classes of Operation and Biasing Networks. Summary. 9. RF Transistor Amplifier Designs. Characteristics of Amplifiers. Amplifier Power Relations. Stability Considerations. Constant Gain. Noise Figure Circles. Constant VSWR Circles. Broadband, High-Power, and Multistage Amplifiers. Summary. 10. Oscillators and Mixers. Basic Oscillator Model. High-Frequency Oscillator Configuration. Basic Characteristics of Mixers. Summary. Appendix A. Useful Physical Quantities and Units. Appendix B. Skin Equation for a Cylindrical Conductor. Appendix C. Complex Numbers. Basic Definition. Magnitude Computations. Circle Equation. Appendix D. Matrix Conversions. Appendix E. Physical Parameters of Semiconductors. Appendix F. Long and Short Diode Models. Long Diode. Short Diode. Appendix G. Couplers. Wilkinson Divider. Branch Line Coupler. Lange Coupler. Appendix H. Noise Analysis. Basic Definitions. Noisy Two-Port Networks. Noise Figure for Two-Port Network. Noise Figure for Cascaded Multiport Network. Appendix I. Introduction to Matlab. Background. Brief Example of Stability Evaluation. Simulation Software on Compact Disk. Index.
327 citations