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[Keyword] input impedance(11hit)

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  • A Unified Analysis of the Signal Transfer Characteristics of a Single-Path FET-R-C Circuit Open Access

    Tetsuya IIZUKA  Asad A. ABIDI  

     
    INVITED PAPER

      Vol:
    E101-C No:7
      Page(s):
    432-443

    A frequently occurring subcircuit consists of a loop of a resistor (R), a field-effect transistor (FET), and a capacitor (C). The FET acts as a switch, controlled at its gate terminal by a clock voltage. This subcircuit may be acting as a sample-and-hold (S/H), as a passive mixer (P-M), or as a bandpass filter or bandpass impedance. In this work, we will present a useful analysis that leads to a simple signal flow graph (SFG), which captures the FET-R-C circuit's action completely across a wide range of design parameters. The SFG dissects the circuit into three filtering functions and ideal sampling. This greatly simplifies analysis of frequency response, noise, input impedance, and conversion gain, and leads to guidelines for optimum design. This paper focuses on the analysis of a single-path FET-R-C circuit's signal transfer characteristics including the reconstruction of the complete waveform from the discrete-time sampled voltage.

  • S-Parameter Method and Its Application for Antenna Measurements Open Access

    Takayuki SASAMORI  Toru FUKASAWA  

     
    INVITED PAPER

      Vol:
    E97-B No:10
      Page(s):
    2011-2021

    This paper focuses on the S-parameter method that is a basic method for measuring the input impedance of balanced-fed antennas. The basic concept of the method is summarized using the two-port network, and it is shown that the method can be enhanced to the unbalanced antennas using a formulation based on incident and reflected waves. The compensation method that eliminates the influence of a measurement jig and the application of the S-parameter method for the measurement of a radiation pattern with reduced unbalanced currents are explained. Further, application of the method for measuring the reflection and coupling coefficients of multiple antennas is introduced. The measured results of the input impedance of a dipole antenna, radiation patterns of a helical antenna on a small housing, and S-parameters of multiple antennas on a small housing are examined, and the measured results obtained with the S-parameter method are verified.

  • Small Loop Antenna and Rectenna for RF Energy Harvesting in FM Bands

    Akira NOGUCHI  Hiroyuki ARAI  

     
    BRIEF PAPER

      Vol:
    E96-C No:10
      Page(s):
    1319-1321

    This paper presents a DC output voltage-boosting antenna with high input impedance in wide frequency band for RF (radio frequency) energy harvesting of FM broadcasting signals. Target input power level of -20dBm is used to design a loop antenna for DC output voltage-boosting. The RF energy harvesting on YNU campus provides 924mV DC output for a single rectenna and 1.72V DC output for twin rectennas by receiving several FM broadcasting wave simultaneously.

  • A Theoretical Analysis of a Circular Microstrip Antenna in a Parallel-Plate Waveguide

    Narihiro NAKAMOTO  Tomohiro OKA  Shoichi KITAZAWA  Hiroshi BAN  Kiyoshi KOBAYASHI  

     
    PAPER-Antennas and Propagation

      Vol:
    E96-B No:1
      Page(s):
    173-181

    To better understand antenna properties in a narrow space such as in a densely-packed device, a circular microstrip antenna in a narrow parallel-plate waveguide is theoretically studied. An analytical expression is derived for the input impedance in a parallel-plate waveguide by using the cavity model with surface admittance on the side wall. The surface admittance is defined by the external magnetic field due to the equivalent magnetic current at the aperture and takes into account the contribution of the parallel plates to the antenna. The magnetic field external to the antenna, that is in the parallel-plate region, is determined by using a dyadic Green's function. The input impedance is then calculated by a basic definition based on the conservation of the complex power. An analytical expression which couples the resonant frequency and the surface susceptance is also formulated. Presented expressions are validated by comparison with experimental results.

  • Adaptive Impedance Matching System Using FPGA Processor for Efficient Control Algorithm

    Hirokazu OBA  Minseok KIM  Ryotaro TAMAKI  Hiroyuki ARAI  

     
    PAPER-Microwaves, Millimeter-Waves

      Vol:
    E91-C No:8
      Page(s):
    1348-1355

    The input impedance of an antenna fluctuates because of various usage conditions, which causes a mismatch between an internal circuit and an antenna. An automatic matching system solves this problem, then this paper presents a reconfigurable impedance tuner that has a set of fixed capacitors controlled by switching p-i-n diodes. A fast control algorithm for selecting the appropriate conditions of an impedance tuner is proposed and mounted on FPGA to demonstrate the performance.

  • High-Speed Low Input Impedance CMOS Current Comparator

    Varakorn KASEMSUWAN  Surachet KHUCHAROENSIN  

     
    PAPER-Analog Signal Processing

      Vol:
    E88-A No:6
      Page(s):
    1549-1553

    A simple high-speed low input impedance CMOS current comparator is presented. The circuit uses improved Wilson current-mirror to perform subtraction. Negative feedback is employed to reduce the input impedance of the circuit. HSPICE is used to verify the circuit performance with standard 0.5 µm CMOS technology. Simulation results demonstrate propagation delay of 1.02 ns, average power consumption of 0.9 mW, and input impedance of 137 Ω for 0.1 µA input current at the supply voltage of 3 V.

  • Characteristic Comparison between Electric Currents on Upper and Lower Surfaces of Patch Conductor in a Microstrip Antenna

    Takafumi FUJIMOTO  Kazumasa TANAKA  Mitsuo TAGUCHI  

     
    PAPER-Antennas and Propagation

      Vol:
    E88-B No:2
      Page(s):
    729-736

    The electric currents on the upper, lower and side surfaces of the patch conductor in a circular microstrip antenna are calculated by using the integral equation method and the characteristic between the electric currents on the upper and lower surfaces is compared. The integral equation is derived from the boundary condition that the tangential component of the total electric field due to the electric currents on the upper, lower and side surfaces of the patch conductor vanishes on the upper, lower and side surfaces of the patch conductor. The electric fields are derived by using Green's functions in a layered medium due to a horizontal and a vertical electric dipole on those surfaces. The result of numerical calculation shows that the electric current on the lower surface is much bigger than that on the upper surface and the input impedance of microstrip antenna depends on the electric current on the lower surface.

  • Impedance Characteristic Analysis of an Axial Slot Antenna on a Sectoral Cylindrical Cavity Excited by a Probe Using Method of Moments

    Rangsan WONGSAN  Chuwong PHONGCHAROENPANICH  Monai KRAIRIKSH  Jun-ichi TAKADA  

     
    PAPER

      Vol:
    E86-A No:6
      Page(s):
    1364-1373

    This paper presents the analysis of the impedance characteristics of a sectoral cylindrical cavity-backed axial slot antenna excited by a probe. The integral equations are derived based on boundary conditions of the proposed structure and they are expressed in terms of dyadic Green functions and unknown current densities. The dyadic Green functions are obtained by using the eigenfunction expansion method together with application of scattering superposition techniques. The unknown current densities are solved by the Method of Moments. The input impedance is subsequently determined from the unknown electric current density at the probe. Numerical results of input impedance and return loss are demonstrated as functions of frequency for various parameters such as cavity length, cavity radius ratio, slot location in φ direction, slot length and probe length. Calculated results are validated by the measurements. At the operating frequency, it is found that the result is sufficiently accurate. The results from this study are very useful for the design of a sectoral cylindrical cavity-backed axial slot array antenna excited by a probe with omnidirectional beam radiation.

  • An Efficient ICT Method for Analysis of Co-planar Dipole Antenna Arrays of Arbitrary Lengths

    Adam Icarus IMORO  Ippo AOKI  Naoki INAGAKI  Nobuyoshi KIKUMA  

     
    PAPER-Antennas and Propagation

      Vol:
    E81-B No:3
      Page(s):
    659-667

    A more judicious choice of trial functions to implement the Improved Circuit Theory (ICT) application to multi-element antennas is achieved. These new trial functions, based on Tai's modified variational implementation for single element antennas, leads to an ICT implementation applicable to much longer co-planar dipole arrays. The accuracy of the generalized impedance formulas is in good agreement with the method of moments. Moreover, all these generalized formulas including the radiation pattern expressions are all in closed-form. This leads to an ICT implementation which still requires much shorter CPU time and lesser computer storage compared to method of moments. Thus, for co-planar dipole arrays, the proposed implementation presents a relatively very efficient method and would therefore be found useful in applications such as CAD/CAE systems.

  • An Improved Circuit Theory for the Analysis of Longer Co-planar Dipole Antennas

    Adam Icarus IMORO  Yoshihisa KANI  Naoki INAGAKI  Nobuyoshi KIKUMA  

     
    LETTER-Antennas and Propagation

      Vol:
    E80-B No:2
      Page(s):
    389-394

    The valid region for the application of the conventional Improved Circuit Theory (ICT) in the analysis of wire antennas is established. To further extend the application of ICT to the analysis of much longer antennas, Tai's trial function is used to derive new formulas for the impedance matrix. Unlike the conventional ICT trial function, Tai's trial functions lead to input impedances which are finite irrespective of antenna length. Results of the new ICT impedance formulas are comparable in accuracy with the general method of moments. Moreover, since all the elements of the new formula have been expressed in closed-form, the resulting ICT algorithm is still superior in terms of computer running time with lesser storage requirement compared to other conventional methods like method of moments. This would enhance ICT applications in CAD/CAE systems.

  • Analysis of High-Tc Superconducting Microstrip Antenna Using Modified Spectral Domain Moment Method

    Nozomu ISHII  Toru FUKASAWA  Kiyohiko ITOH  

     
    PAPER-HTS

      Vol:
    E77-C No:8
      Page(s):
    1242-1248

    In this paper, we analyze high-Tc superconducting (HTS) microstrip antenna (MSA) using modified spectral domain moment method. Although it is assumed that the patch and the ground plane of the MSA are perfect electric conductors (PECs) in the conventional spectral domain method, we modify this method to compute the conduction loss of the HTS-MSA. In our analysis, the effect of the HTS film is introduced by the surface impedance which we can estimate by using the three fluid model and experimental results. This paper presents numerical results about the HTS-MSA, for example, the relations between the thickness of the substrate and the radiation efficiency, the temperature and the resonant frequency, and so forth. And we discuss the effective power range where the performance of the HTS-MSA is superior to that of the Cu-MSA.