Modified rectangular patches for self-oscillating active-antennaapplications

Two modifications to a rectangular-patch antenna, suitable for the integration of active devices, are presented. In the first modification, the impedance inverter was placed in the rectangular opening formed by removing the central part of the patch. This modification allows optimal matching of the active device by changing the position, width, and length of the impedance-line transformer. An oscillating antenna, using this modified patch and a Gunn diode, showed a high EIRP, higher spectral purity, and substantially lower cross-polarization levels, in comparison with the reference active antenna with an unmodified patch. Because of the higher overall Q, this modification is recommended for active-antenna applications with active devices that have a narrower negative-resistance bandwidth. In the second modification, an active device (Gunn diode) was integrated directly into a rectangular opening inside the patch, without the use of a line transformer. This reduced the overall Q of the antenna, thus allowing wide-band frequency tuning by changing the bias voltage. A clear spectrum, with no spurious components of the free-running oscillating antenna, was observed. Radiation patterns in the E and H planes were measured. Low levels of cross-polarization, as for the first modification, were obtained. Injection-locking properties were investigated throughout the tuning range. A relatively wide locking range, with a good locking gain, was achieved. Such a miniaturized wide-band VCO antenna is applicable for integration in injection-locked active arrays, and spatial power combiners     

An efficient CAD-oriented large-signal MOSFET model

An efficient computer-aided-design-oriented large-signal microwave model for silicon MOSFETs is presented based on the well-founded small-signal equivalent circuit including self-heating effect and charge conservation condition. The proposed new single continuously differentiable empirical equations for drain current and gate capacitance are simple and quite accurate. The model parameters in the equations are constructed in such a way that they can be easily and straightforwardly extracted from measured data. The temperature effect is predicted by simply adopting the linear temperature-dependent model parameters for threshold voltage, saturation current, capacitance, and series resistances. The presented model is a good compromise between the simplicity of numerical calculations and the accuracy of final results that is desired by circuit designers in nonlinear circuit simulation     

Transmission-line model for two-port rectangular microstrip patches with ports at the nonradiating edges

A transmission-line model for the analysis of two-port rectangular microstrip patches with input and output ports located at the nonradiating edges is described. For this type of two-port patch the amount of radiated power can be controlled by adjusting the locations of the input and output ports.     

Dual frequency microstrip rectangular patches

A dual frequency microstrip rectangular patch antenna resonating at frequencies 520 MHz and 2.5 GHz is presented. This antenna incorporates a matching structure to improve the impedance characteristic at one resonance frequency and uses symmetrically positioned varactor diodes to control resonance at a lower frequency. The use of varactor diodes also provides the benefit of a broad tuning range at the lower resonance frequency. A tuning range of 32% at 520 MHz was measured.<>     

Improved cavity model parameters for calculation of resonantfrequency of rectangular microstrip antennas

Models for the resonant frequency proposed by other authors are shown to produce misleading results for frequencies greater than about 3 GHz. However, a cavity model with a novel empirically determined edge extension parameter provides calculated frequencies within 2% of measurements for antennas operating between 600 MHz and 5 GHz     

Finite phased arrays of rectangular microstrip patches

Finite phased arrays of rectangular microstrip patch antennas are analyzed. Reflection coefficient magnitudes, element patterns and efficiency (based on power lost to surface waves) are calculated for various sized arrays on substrates of practical interest and are compared with previous infinite array solutions. Measured element patterns and mutual coupling data for a small array are presented and compared with calculations.     

CAD-oriented lossy models for radial stubs

A lumped equivalent circuit model for both series and double-shunt (butterfly) connected radial stub has been developed. The model-simple and effective-not only includes conductor and dielectric losses but also radiation ones, which play an important role in microstrip circuit elements. Experiments widely demonstrate its suitability for implementation in available CAD (computer-aided design) programs. Furthermore, a synthesis procedure for using radial stubs in circuit design is described. An application of the proposed design procedure and simulation tools in the development of very broadband nongrounded termination is also presented     

A closed-form CAD-oriented model for the high-frequency conductorattenuation of symmetrical coupled coplanar waveguides

Closed-form CAD-oriented conformal-mapping approximations are presented for the HF attenuation of two-conductor symmetrical coupled coplanar waveguides (CCPWs). The expressions are compared with the results obtained from a full-wave electromagnetic (EM) simulator and found to yield acceptable agreement. A modified form is also presented, which partly overcomes the low-frequency limitations of the skin-effect approximation     

An accurate two-dimensional CAD-oriented model of retrograde doped MOSFETs for improved short channel performance

An analytical CAD-oriented model for short channel threshold voltage of retrograde doped MOSFETs is developed. The model is extended to evaluate the drain induced barrier lowering parameter (R) and gradient of threshold voltage. The dependence of short channel threshold voltage and R on thickness of lightly doped layer (d) has also been analyzed in detail. It is shown that a retrograde doping profile reduces short channel effects to a considerable extent. A technique is developed to optimize the device parameters for minimizing short channel effects. The results so obtained are in close proximity with published data.     

Admittance of a rectangular slot which is backed by a rectangular cavity

The rectangular cavity backed slot is excited by a current source connected across its center. The longitudinal voltage variation across the slot is obtained from the variational solution of an integral equation. For shallow and narrow cavities the slot appears inductive and the voltage is rapidly attenuated along the slots. The slot may resonate for deeper and/or wider cavities, when the voltage along the slot is approximated by a half-cycle of a sine wave. The resonant cavity depth and the antenna bandwidth are examined for various cavity and Slot parameters. Dielectric cavity loading is shown to decrease both the resonant cavity depth and the antenna bandwidth.     

A CAD-oriented analytical model for the losses of generalasymmetric coplanar lines in hybrid and monolithic MICs

New analytical approximations are derived for the conductor losses of asymmetric coplanar waveguides (ACPW) and coplanar striplines (ACPS) on a finite-thickness dielectric substrate. The expressions hold for lines whose metallizations have thickness much smaller than the slot and strip widths, but suitably larger than the skin penetration depth at the operating frequency. The derivation is based on an extension of the conformal mapping approach formerly proposed by Owyang and Wu (1958) for symmetric lines in air. Comparisons with published data from quasistatic or full-wave numerical analyses are presented to validate the expressions derived for both the symmetric and the asymmetric case. The analytical characterization presented in the paper is well suited for inclusion into CAD codes for MMIC design     

Antenna Designer's Notebook-similarities in the design equationsfor rectangular and circular patches

The transcendental equations, which arise in the cavity-model of patch analyses, are reexamined. It is shown that when the radiation quality factor is not too small, useful approximations to the ensuing design equations may be obtained in a format common to both types of patch. To achieve this, it is assumed that natural loss-tangent effects in the substrate may be neglected. An emphasis is placed on the role of the cavity-wall conductance/susceptance ratio. It is important that a value for this parameter be selected with care in cases requiring a wideband frequency response     

Ray-optical solution for the dyadic Green's function in a rectangular cavity

The ray-optical method, which has been successfully employed for the analysis of diffraction and scattering problems, is used to derive the Green's function in a rectangular cavity. Despite the asymptotic approximations inherent in the method, it is shown that it gives a physical or geometrical insight into the mechanisms of propagation in guiding structures leading to exact or rigorous solutions not always provided by other methods.     

HEMT for low-noise microwaves: CAD-oriented performance evaluation

This paper shows how a graphic processing of low-noise HEMT's small signal parameters, allows evaluating and comparing the actual performance obtainable in front-end applications. HEMT's tradeoff charts which solve tradeoffs among the basic low-noise amplifier performance are reported. Figures of merit for microwave low-noise HEMT which represent a fast way of evaluating HEMT in actual working conditions and of selecting the proper transistor, are defined. As an example, the tradeoff charts and the figures of merit of two HEMT's (Fujitsu FHR02FH, Sony 2SK677) and a pseudomorphic-HEMT (Celeritek CFB001-03) are reported and compared with the data sheets     

Flush mounted rectangular cavity slot antennas--Theory and design

The loaded rectangular cavity slot antenna is analyzed using variational methods in conjunction with simplified equivalent circuit techniques to derive accurate design guides for efficiency, bandwidth, and resonant frequency. The aperture admittance is computed and the effects of a compound aperture plane iris and of material loading are analyzed. The aperture admittance of all such loaded cavity antennas is proportional tomu_{r},sqrt{mu_{r}/epsilon_{r}}, or1/epsilon_{r}, which characteristic lends to a common method of optimization of|T|^{2}(transmission cofficient). Experimental results include: 1) measurements of aperture field; 2) a comparison of theoretical and experimental value of bandwidth, efficiency, resonant frequency, and beam pattern for several experimental models; and 3) the measurement of the effect of applied dc magnetic field.     

Millimeter wave source in the rectangular waveguide cavity

This paper describes a power combiner of solid—state millimeter wave in rectangular cavity. The operating frequency is about 50 GHz. And the sources of excitation are GaAs Gunn deodes. Final presents the performance parameter, combining efficiency, tuning range, frequency drift, and FM noise, etc. This paper also presents a millimeter wave source of rectangular waveguide cavity. Using an exellent algorithm to design rectangular waveguide cavity of power combimer. The algorithm gives the mathematial model, on the basis of the mathematial model, using CAD of PC microcomputer to design the parameters of the cavity. This paper presents a program of CAD of micocomputer.     

有孔矩形腔的屏蔽效能及其对谐振抑制研究

介绍了用传输线解析计算法分析有孔矩形腔屏蔽效能的基本原理,对基本公式作进一步修正,使其能计算孔阵列情形,并对修正的传输线模型计算公式进行了扩展,使其能计算任意极化方向时的情况.通过在腔体内表面敷设经过优化计算的复合电介质涂层,实现了对特定谐振频率抑制.计算和仿真结果表明:当处于谐振频率时,屏蔽系数很低甚至为负;孔阵的屏蔽效能比相同面积的单孔的屏蔽效能好;屏蔽效能随极化角度增加而变化,当耦合电场极化方向平行孔缝的长边时,屏蔽效果最好;在腔体内表面上敷设对应腔体谐振频率的复合电介质涂层,实现了在相同的厚度条件下对腔体谐振频率最佳的抑制效果.根据计算结果提出了设计屏蔽腔的建议.     

External cavity semiconductor laser comprising brewster-angled rectangular core fibre

A GaInAsP semiconductor laser diode, with one of its facets Brewster angled was coupled to a Brewster angled rectangular core fibre to obtain an external cavity. Very good coupling efficiency and a high degree of polarisation of the output beam has been obtained.<>     

基于SBR方法的矩形腔体散射特性分析

本文从电大腔体散射出发,研究分析了射线弹跳法的原理及性质,基于对典型矩形腔体的几何特性及射线追踪特性的研究,推导了该类腔体入射口面与出射口面间的关系,得到了能够解析描述入射位置与出射位置的数学公式。在此基础上,通过对射线弹跳法的分析和简化,推导得到适用于电大矩形腔体的散射的计算公式,极大地提高了原有算法在此类问题上的计算效率。计算结果验证了该公式的有效性,也总结出了矩形腔体散射与入射角度之间的关系。     

基于SBR方法的矩形腔体散射特性分析

本文从电大腔体散射出发,研究分析了射线弹跳法的原理及性质．基于对典型矩形腔体的几何特性及射线追踪特性的研究,推导了该类腔体入射口面与出射口面间的关系,得到了能够解析描述入射位置与出射位置的数学公式。在此基础上,通过对射线弹跳法的分析和简化,推导得到适用于电大矩形腔体的散射的计算公式,极大地提高了原有算法在此类问题上的计算效率。计算结果验证了该公式的有效性,也总结出了矩形腔体散射与入射角度之间的关系。