A broad-band resistively loaded V-antenna: experimental results

A broadband receiving antenna was realized using a resistively loaded thin-film V-monopole and a 500-Ω oscilloscope probe. The pulse-receiving performance of the antenna was evaluated in a time-domain antenna range, for various directions of the incident pulse. The antenna is capable of receiving a 520 ps electromagnetic pulse, incident within 45° from the boresite direction, with good fidelity. The antenna was also tested in a transverse electromagnetic cell in the time and frequency domains. The frequency-domain receiving transfer function of the antenna was found to be within -57±3 dB in the 22 MHZ to 1.1 GHz frequency range     

Pulse-receiving characteristics of V-dipole antennas with resistiveloading

The pulse-receiving characteristics such as bandwidth, sensitivity, and fidelity of several V-dipole antennas loaded with a nonreflecting resistance profile are analyzed, taking into account the effect of parameters such as the linear resistance at the feed point, the interior angle of the V-antenna, and the terminal resistance load     

Direct GA-based optimisation of resistively loaded wire antennas inthe time domain

An optimisation procedure based on the genetic algorithm is applied to design resistively loaded wire antennas. The broadband characteristic of the antenna is realised through a maximisation of the fidelity factor directly in the time domain. The performance characteristics of the resulting antenna are presented and contrasted with those of the Wu-King design     

An AC-powered experimental memory circuit with a resistively loaded sense circuit

The design and fabrication of an ac-powered experimental memory circuit for Josephson cache memories are reported. The circuit contains a memory cell array and a sense circuit. The sense circuit consists of RCJL gates, symmetrical three-junction sense gates, and transmission lines. An experimental memory circuit has been fabricated by 2-µm Pb-alloy processes. A proper circuit operation, has been verified using a bipolar trapezoidal waveform current. A ±23-percent sense current margin and a ±29-percent OR gate bias current margin were obtained. A typical 130-ps sense time was estimated for a 1-kbit memory by computer simulations.     

Transients in a resistively loaded linear antenna compared with those in a conical antenna and a TEM horn

The receiving and transmitting transient responses of the resistively loaded linear antenna, the TEM horn, and the conical antenna are investigated theoretically and experimentally using the fast Fourier transform (FFT) technique. The receiving transient response of the resistively loaded linear antenna indicates that the shape of a 70-ps impulse is well preserved.     

加载单极子天线的时域辐射特性

基本的单极子天线由于其本身的特社会在天线内部对馈入的信号进行多次反射,严重,制约着它的辐射性能。采用时域有限差分法对比计算了加载与非加载单极子天线的时域辐射特性。计算结果表明,加载是改善单极子天线时域辐射性能的最佳选择,但需要以牺牲辐射效率为代价。     

Radiation characteristics of corrugation loaded dielectric-coated conducting cylinder

The radiation characteristics of a corrugation loaded dielectric coated conducting cylinder are investigated theoretically for the infinite periodic and finite structures. For the infinite periodic structure, the mode matching method is applied. The integral equation is derived for the finite structure by use of the Fourier transform and mode expansion. The influences of the corrugation width, corrugation depth, dielectric thickness, cylinder radius, and finite corrugation number on the radiation characteristics (leakage constant, phase constant, and radiation pattern) are investigated. The results of the finite periodic corrugations are compared with those of the infinite extent structure and good agreement is found. To reduce the high side lobe of the uniform periodic structure, nonuniform quasiperiodic corrugation arrays are considered. The surface wave radiated by the structure having end-fire radiation pattern is also investigated.     

Scattering characteristics of non-linear loaded two-sided corner reflector

Method of integral equations of sideband component of surface currents and physical optics method can be used for calculation of non-linear corner reflector. Efficient equivalent areas of backward scattering at frequencies of incident field and sideband frequencies are calculated.     

Frequency tuning characteristics of capacitively loaded Salisburyscreen radar absorber

The frequency characteristics of a Salisbury screen radar absorber that incorporates a layer exhibiting both resistive and capacitive properties are considered. If the capacitance is fixed, the absorber thickness and hence weight may be reduced but at the expense of bandwidth. If the capacitance is variable then the absorber may be tuned via an external control signal. The practical limitations of both applications are discussed in relation to recent advances in conducting polymer materials     

Radiation characteristics of strip loaded hollow dielectric E-planesectoral horn antennas

The authors report the development of a novel E-plane sectoral horn. A metallic strip of optimum length loaded on the horn is capable of giving symmetric patterns both in the E and H-planes with low sidelobe levels     

A resistively stabilized XeCl laser operating at 200 Hz

We have explored the feasibility of stabilizing the discharge of a high repetition rate XeCl laser by providing distributed resistive ballasting of one of the transverse electrodes in the form of an array of resistive pins. This technique has enabled us to demonstrate operation of the laser at a (power supply limited) pulse repetition frequency of 200 Hz in a device which did not require forced circulation of the gas mixture.     

Radiation characteristics of a dielectric sphere loaded corrugated E-plane sectoral horn

The experimental results of the radiation characteristics of a dielectric sphere in front of a corrugatedE-plane sectoral horn together with the design aspects of the horn are reported. The experiments were carried out with the test antenna system consisting of dielectric (paraffin wax) spheres kept offset at the minimum input VSWR position in front of the horn excited in the balanced HE11mode. The test results have shown that such a feed system produces radiation patterns with reduced sidelobe levels and increased on-axis gain with reduced 3-dB beamwidths as compared to the same horn radiating in free space. The feed system may also produce a low input VSWR and can be used as a variable beamwidth feed for praraboloidal reflectors.     

Propagation characteristics of picosecond electrical pulses on aperiodically loaded coplanar waveguide

A theoretical model which was developed to investigate the propagation characteristics of picosecond electrical pulses on a coplanar waveguide capacitively coupled to periodically spaced sampling channels is presented. Various factors which affect the signal waveform are analyzed in both the frequency and the time domains. The results show that in addition to modal dispersion, conductor loss, and radiation loss of the electrical signals, multiple reflections among the sampling gaps constitute another feature of the signal transfer along the waveguide. The authors have measured the picosecond pulse dispersion using the optoelectronic correlation technique. The experimental data are compared with the theoretical results     

Radiation and matching characteristics of a novel dual-band dielectric loaded coaxial horn

Copolar and crosspolar radiation as well as matching characteristics of a novel dual-band coaxial hybrid-mode feed horn with partial dielectric loading [1] for reflector antennas have been numerically and experimentally investigated. In comparison with dual-band corrugated horns this horn has higher crosspolar level, but provides larger band separation and rather good electrical performances over a wide frequency range (20% and more) within each operational frequency band. Furthermore, the main concept of the coaxial feed system can be easily extended for multi-band cost-effective applications in reflector antennas with polarization diversity.     

Propagation characteristics of partially loaded two-conductor transmission line for broadband light modulators

The characteristics of two-conductor transmission lines containing two dielectrics are derived. The results are applied to broad-band traveling-wave light modulators.     

Radiation characteristics of wide-angle H-plane sectoral horn loaded with dielectric of multiangular shape

Radiation characteristics of H-plane sectoral horns can be improved or modified by inserting a proper dielectric loading. A study of the radiation of wide-angle sectoral horns with a multiangular dielectric insert that behaves as a lens is presented. Two types of loading are considered, the first in the waveguide feed, the second in the aperture. The method of analysis is the domain product technique utilizing Mathieu function expansions. Numerical investigation has shown that both configurations can provide improvements, but the first lens possesses certain advantages in comparison with the second one. Specifically, it has smaller dimensions and allows minimization of the reflected wave amplitude. Proper choice of the shape of the first insert and material of the dielectric can ensure reduction in the beamwidth, lowering the side lobe level and low return losses in a broad band of frequencies.     

Propagation and radiation characteristics of dielectric loaded corrugated dual-frequency circular waveguide horn feeds

Based on a systematic analysis the design and experimental studies on a composite dual-frequency feed with a single radiating aperture are presented. The criterion for selecting the ratio of the diameter of the corrugated guide excited at the lower frequency in the dominant mode to that of the dielectric rod, axially located within the guide and excited at the higher frequency in the dominant mode, is discussed. The constructional features of a typical dual-frequency feed designed for operation atSandXbands (with 2.68 GHz and 9.375 GHz as center frequencies, respectively) are outlined. The measured radiation patterns show good symmetry and sidelobe suppression over 20-percent bandwidth inSandXbands and are in good agreement with calculated patterns.     

Analysis of the effects of a resistively coated upper dielectriclayer on the propagation characteristics of hybrid modes in awaveguide-shielded microstrip using the method of lines

In this paper, propagation characteristics of even-symmetric hybrid modes in a waveguide-shielded microstrip in the presence of a resistively coated dielectric layer affixed to the top cover of the housing is analyzed with the method of lines. The resistive boundary condition is employed to model the resistive film. A shielded microstrip line having a unity strip-width-to-substrate-thickness ratio (i.e., w/h ₁=1) placed on top of a 0.635-mm-thick alumina substrate is considered. Based on a 10h₁×7h₁ reference housing, four different housing arrangements are obtained by varying the structural parameters of the resistively coated dielectric layer. Results obtained indicate that the effects of both the housing walls and the resistively coated upper dielectric layer on the dominant (quasi-TEM) mode are insignificant and may be ignored when frequency is above 15 GHz. For the higher order modes, the resistive film appears to be transparent when film resistance is greater than about 1 kΩ, it behaves as a good conductor when film resistance is much smaller than 100 Ω, and in between it results in nonlinear (and even oscillatory) higher order modal behaviors. Apparently, due to the increasing field concentration inside the upper dielectric (as suggested by the increasing ε_reff) for a given mode, both the maximum attenuation and the film resistance needed to achieve it increase with frequency and dielectric constant of the upper dielectric layer     

On the realization of resistively matched three-ports and theramp-waveform responses of resistive, signal-split three-porttransmission-line networks

Three-port networks consisting of three transmission lines and three branching resistors at a junction are discussed, assuming TEM wave propagation and lossless lines. The matching conditions for the resistive three-port are modeled by scattering matrices. As transmission lines of unequal length are used, the network transfer functions are derived for three different delay variables. These functions are obtained in a matrix form after their expansions with respect to these variables are derived, so that output waveforms can be calculated from the network transfer functions or their expansions. Three characteristics of output waveforms are discussed. Ideal networks that furnish the same output waveforms as their inputs and practical networks that have parameters as close as possible to the ideal are described. Examples of networks that keep the ringing of output waveforms within given tolerances, from the first arriving wave to the steady state, are presented. Power dissipation is discussed