Miniloop antenna operation and equivalent circuit

The equivalent circuit and principles of operation of a miniloop antenna (i.e., a larger, tuned outer loop inductively coupled to a smaller inner loop) are established and verified. Both classical and moment methods for determining the circuit parameters are presented and compared. Based on the equivalent circuit, the features of the miniloop are contrasted to those of the single, outer loop as a system element, where factors such as signal bandwidth, efficiency, and problems of matching to the transmission line are considered.     

On the equivalent circuit of a receiving antenna

The equivalent circuit of a receiving antenna consists of a current generator and two admittances: one for the load, and one for the antenna. The short-circuit current, I_g - receiving property - may be expressed in terms of the transmitting properties of the antenna. The article gives a derivation for the value of I_g. It is assumed, to simplify matters, that the antenna is located in free space, and that its feeding line is a monomode waveguide (a coaxial cable, for example). The extension to multimode lines, or to spatial regions containing linear media (possibly anisotropic, and/or non-reciprocal) is fairly straightforward     

Comment on the equivalent circuit of a receiving antenna

For original article see Van Bladel (IEEE Antennas Propag. Mag., vol.44, no.1, p.164-5, 2002). The author comments on the above article in the context of a long-standing paradox that arises when an equivalent circuit is used to characterize the electrical properties of a receiving antenna.     

An equivalent circuit for charge-transfer devices

A new equivalent circuit for charge-transfer devices (CTD) is proposed. Results of circuit simulations of a string of CTD's, using the transient analysis program ASTAP, are presented. These show, among other details, incomplete transfer caused by high pulse repetition rates and backward transfer caused by excessive input charge.     

An accurate moment method model for the tapered slot antenna

A moment-method model is presented for the radiation characteristics of the tapered slot antenna. It overcomes the shortcoming of an earlier theory. The method is rigorous for the air dielectric antennas. For dielectric-supported antennas, the method is approximate but accurate. The method is particularly accurate for antennas etched on substrates that are electrically thin or have a low dielectric constant, within the limits of (ε_r-1)d /λ₀⩽0.1. Numerical results are presented for the radiation pattern and compared with experimental results to validate the model     

An equivalent circuit model for uni-traveling-carrier photodiode

In this paper, an equivalent circuit model of uni-traveling-carrier photodiode (UTC-PD) is developed. According to the feature of UTC-PD, hole continuity equation is ignored and only electron continuity equation is introduced, which decreases the complexity of the model. The model is based on a simplified structure and can well express the feature of UTC-PD. Several direct current (DC) and alternating current (AC) analyses are performed to test the model, and the results from the model agree well with that of numerical simulation.     

An equivalent circuit for narrow-band nonideal circulators

The scattering parameters of a simple equivalent circuit based upon modification of an earlier circuit of Bosma [1] are derived and compared with previously published experimental results to demonstrate the suitability of the equivalent circuit for use in the analysis of microwave circuits such as circulator-coupled single-stage and multi-stage negative-resistance amplifiers. The approach followed here can be generalized to obtain circuit models for broad-band circulators.     

An equivalent circuit for the noise in VHF triodes

It is the aim of this paper to show that the present Information about the response of vhf triodes to signals and to noise can be represented is an equivalent circuit consisting of an equivalent noise emf in series with the input and of an independent equivalent noise current generator with an admittance in parallel to it connected between grid and cathode.     

An annular slot antenna on a dielectric half-space

The radiation properties of both singly and multiply fed annular slot antennas on a dielectric/air interface have been analyzed using Galerkin's method applied in the Hankel transform domain. The validity of our method has been confirmed through comparison with both theoretical and experimental results. The magic slot configuration has also been studied. The polarization diversity of this radiator makes it suitable for implementing a quasioptical balanced mixer     

An equivalent circuit for microwave noise at the potential minimum

It has been suggested that an inductive element should be added to Watkins RC equivalent circuit for the microwave noise current fluctuations at the potential minimum of a diode, and that this added element gives closer agreement with more recent work which shows a pronounced peak in noise current near the plasma resonance,a = frac{1}{2}. This paper presents an approximate analytical argument for the inclusion of an inductive element, based on the density-function method of analysis, which predicts the proper value for the inductance and yields a curve of reduction factor vs frequency in agreement with more detailed theories. The value of the inductance is such as to resonate with the capacitance of the potential minimum ata = frac{1}{2}. A discussion of the linearity of the potential minimum and of the idealized potential-minimum model is also included.     

An improved GaAs MESFET equivalent circuit model for analog integrated circuit applications

An improved equivalent circuit model of a gallium-arsenide (GaAs) MESFET that is optimized for the design and analysis of precision analog integrated circuits is described. These circuits entail different modeling requirements from digital or microwave circuits, for which existing equivalent circuit models are optimized. Improved techniques are presented to model the drain-to-source conductance, device capacitance, and the functional dependence of drain-to-source current.     

An approach to determining an equivalent circuit for HEMTs

A simple way to determine a small-signal equivalent circuit of High Electron Mobility Transistors (HEMTs) is proposed. Intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements. Assuming that the equivalent circuit composed of lumped elements is valid over the whole frequency range of the measurements, the extrinsic elements are iteratively determined using the variance of the intrinsic elements as an optimization criterion. Measurements of S-parameters up to 62.5 GHz at more than 100 different bias points confirmed that the HEMT equivalent circuit is consistent for all bias points     

Coaxially-fed tapered slot antenna

An improved design of the longitudinal tapered slot antenna is presented which incorporates a tapered coaxial line balun. This transformer type offers large bandwidth, allows for the direct connection of coaxial sources and reduces the complexity of the printed circuit. Experimental results for an antenna prototype are presented     

Annular slot windshield antenna

An automotive AM/FM hidden antenna using the slot between the body of the automobile and a metal solar heat-reduction film in the front windshield is described. Such solar heat-reduction metal films are becoming common and thus represent an opportunity to incorporate an antenna at only marginal cost. The radio frequency (RF) input impedance and gain patterns are described, and techniques for impedance matching are shown. Theoretical and experimental antenna patterns are compared. A test range measurement system and experimental results is described. A mobile on-road system to characterize the antenna in urban and suburban environments is shown. The application of this mobile system to the measurement of calibrated gain patterns is also demonstrated     

Double-beam parallel-plate slot antenna

This paper presents the design and prototyping of a double-beam linear polarized parallel-plate slot antenna at 12-GHz band. Each beam is separated 27.7/spl deg/ and 27.3/spl deg/, respectively, from broadside direction. Two different radiation patterns are generated, exciting the parallel plate from opposite sides. The radiating elements are composed by three parallel slots, the central slot is close to the resonance, while the side ones are designed to minimize the reflection inside the parallel plate. The length of the slots in the same row is kept constant (periodic walls), and the distance between columns is equal to 0.7 times the wavelength. The designs of the feeding networks and the design of the array of slots generate both beams, pointing toward Hispasat and Astra satellites simultaneously, at the same frequency band. The feeding networks are two microstrip circuits that excite two linear arrays of 24 patches, placed at both sides of the antenna, and generate both quasi-TEM mode plane waves inside the parallel-plate waveguide, propagating from one side to the other.     

An equivalent circuit model for terminated hybrid-modemulticonductor transmission lines

An equivalent circuit for terminated hybrid-mode multiconductor transmission lines is presented. Existing CAD packages, such as SPICE, can be used for its implementation. Model parameters can be found from either a TEM or a full-wave analysis of the transmission lines. The equivalent circuit is used to simulate multiconductor microstrip for applications in high-speed integrated circuits. The accuracy of the TEM approximation is investigated for time-harmonic as well as pulse signal propagation. For some cases examined, the time-harmonic signal propagation data obtained using the TEM approximation become quite inaccurate at frequencies in excess of 20 GHz. The TEM approximation is adequate, however, for pulse propagation with 15-ps risetime and falltime pulses on the geometries investigated     

Waveguide slot antenna with a coupled dipole above the slot

The effect of a parasitic dipole above a waveguide slot antenna is shown analytically and verified experimentally. The E-plane radiation pattern is shown to be rather sensitive to the change of dipole length, and an equalised E- and H-plane pattern is obtained by choosing a proper length of dipole.     

Switchable CPW-fed slot antenna for multifrequency operation

A CPW-fed slot antenna including pin diodes for multifrequency operation within a frequency octave and more is presented. The use of GaAs beam-lead pin diodes limits the influence of the parasitic resistance and reactance presented by surface mount diodes. The simplicity of the structure results in a simplified and compact biasing circuit     

Printed ring slot antenna for circular polarization

A new design of a microstrip-line-fed circularly polarized printed ring slot antenna is proposed. Circular polarization (CP) radiation of the proposed design is achieved by introducing proper asymmetry in the ring slot structure and feeding the ring slot using a microstrip line at 45° from the introduced asymmetry. The asymmetry introduced in the proposed design is a meandered-slot section and the proposed CP design can be applied to printed square and annular ring slot antennas. Prototypes of the proposed design have been implemented. Experimental results show that good CP radiation performances are obtained and the 3 dB axial-ratio CP bandwidths obtained for the square and annular ring slot antennas are about 4.3% and 3.5%, respectively