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This paper presents the design of a novel power-divider circuit with an unequal power-dividing ratio. Unlike the conventional approaches, the characteristic impedance values of all the branch lines involved are independent of the dividing ratio. The electrical lengths of the line sections are the only circuit parameters to be adjusted. Moreover, the proposed structure does not require impedance transformers at the two output ports. By the introduction of a transmission line between one of the output ports and the isolation resistor, a flexible layout design with reduced parasitic coupling is achieved. For verification, the measured results of a 2 : 1 and a 4 : 1 power-divider circuits operating at 1 GHz are given. A relative bandwidth of over 20% is obtained based on a return loss and port isolation requirement of-20 dB. Index Terms--Microstrip, power divider, unequal power-dividing ratio.

This paper presents the design of a new dual-band filter with very wide upper stopband. The proposed circuit offers a simple and compact structure with low insertion loss. Spurious suppression is achieved by using specially designed coupling and resonator sections. Moreover, a systematic analysis is applied to the proposed topology with closed-form design equations derived. For verification purposes, the measured performance of a microstrip filter operating at 1 and 2 GHz is shown with stopband attenuation of greater than 20 dB over the frequency range from 2.5 to 8.0 GHz. Index Terms--Dual band, microwave filters, stopband.

This paper presents the design of a new Wilkinson power divider for dual-band application. The proposed circuit also features a simple structure with realistic impedance values, distributed design with reduced parasitic effect (in compared to lumped component), and exact solution (ideal characteristics). Closed-form design equations are derived using the even- and odd-mode formulation. For verification, the measured results of a microstrip power divider operating at 1 and 2 GHz is shown. Index Terms--Distributed circuit, dual band, power divider.

This paper presents a novel and simple linearization scheme for a CMOS double-balanced mixer based un the use of multibias dual-gate transistors. In this technique, intermodulation-distortion (IMD) components with proper phase relationship, generated by devices operating at different bias conditions, are combined together to improve the linearity of mixers. For experimental verification, the measured performance of a fabricated CMOS mixer is shown. Over 35 dB of IMD reduction is achieved by the proposed method under proper biasing condition. Index Terms--Double-balanced mixer, dual-gate transistor, linearization.

This paper presents the design of a novel branch-line coupler that can operate at two arbitrary frequencies. The proposed circuit also features compact size and planar structure. Explicit design formulas of the proposed dual-band coupler are analytically derived. Moreover, practical issues such as the realization of branch-line impedance and optimum choice of circuit topologies are addressed. For verification purposes, both simulated and measured results of a microstrip branch-line coupler operating at 900/2000 MHz are included. Index Terms--Couplers, dual band, planar circuits.

This paper presents for the first time the investigation of multistage amplifier linearization based on the generalized low-frequency signal-injection technique. Difference-frequency signals, generated by predistortion circuit, are fed to the biasing circuitry of a multistage amplifier for third-order intermodulation-distortion cancellation. The reason that two-stage injection shows better linearization performance than the single-stage injection case is analytically derived. Furthermore, issues on the optimum operating condition, gain error, and bandwidth limitation are also addressed. For demonstration, the measured performance of an experimental system using both the two-tone and digitally modulated test signals are shown. Index Terms--Amplifiers, linearization, multistage.

This paper presents a novel linearization scheme for RF amplifiers based on simultaneous harmonic and baseband signal injection. In this method, second-order frequency components generated by predistortion circuits are fed to the input of the main amplifier to mix with the fundamental signal for third-order intermodulation distortion (IMD) cancellation. A general and rigorous analytical formulation of baseband, harmonic, and the proposed injection techniques is presented, and from these derived expressions, the optimum conditions for IMD suppression are developed. The result also reveals the practical limitation of the proposed method subject to gain and phase error associated with the RF and baseband circuitry. For comparison purposes, an amplifying system is constructed for the experimental investigation of second-order signal injection approach. Both two-tone and digitally modulated waveforms are employed in these measurements. Index Terms--Amplifiers, baseband, harmonic, linearization.

A compact two-dimensional (2-D) full-wave finite-difference frequency-domain method is proposed for the analysis of dispersion characteristics of a general guided wave structure. Because the longitudinal field components are eliminated in the proposed method, only four transverse field components are involved in the final resulting eigen equation. This feature considerably reduces the required CPU time as compared to the existing approaches by which six field components are comprised. Additionally, unlike other 2-D finite-difference schemes that determine the eigenfrequency for a given propagation constant, the new method finds the propagation constant [beta] for a given [[kappa].sub.o] (frequency). The new method has been verified by examining the computed results of a number of typical guided wave structures with the published results. Very good agreement is achieved. Index Terms--Anisotropic media, eigenvalues and eigenfunctions, finite-difference methods, frequency-domain analysis, waveguide.

This paper presents for the first time a computer-aided design-oriented (CAD) analytical formula for the determination of the characteristic parameters of asymmetrical coupled lines of a conductor-backed coplanar type. Closed-form expressions are developed for evaluating the self and mutual static capacitances based on a sequence of conformal transformations. The derived formulas show excellent accuracy compared to the results produced by a spectral-domain approach. Index Terms - Asymmetrical coupled lines, coplanar waveguide.

This paper presents two sets of newly developed CAD-oriented formulas for the evaluation of the quasi-static even- and odd-mode characteristics of coplanar coupled lines on substrates of finite thicknesses. The first set of expressions is derived based on the conformal mapping method. Numerical results show that both the even- and odd-mode characteristic impedances and effective dielectric constants computed by these expressions are in good agreement with the results generated by the spectral domain method. The second set of formulas is derived based on a seminumerical approach and can be used to calculate the geometrical parameters of coplanar coupled lines directly from the given electrical parameters, without using an iterative approach. These seminumerical formulas give maximum error in impedance calculation of about 2.0% (c/h < 2), over a wide range of impedance and dielectric constant values.

This paper presents the quasi-TEM characteristics of microshield lines with practical cavity sidewall profiles. A conformal mapping method is used for the derivation of the electrical parameters of the structures. In this study, numerical results for the characteristic impedances of air-suspended microshield lines with both positive and negative sidewall slopes are presented. Simple and explicit CAD-oriented expressions are proposed for the design and analysis of rectangular-shaped microshield line. Comparisons are made between the results obtained by these formulas and by a standard numerical technique. Furthermore, the sensitivities of the electrical parameters of a rectangular-shaped microshield line to an imperfect sidewall etching process, leading to nonvertical sidewall profiles, are also examined.

This paper presents some simple, explicit and practical formulas for the evaluation of the quasi-TEM characteristic parameters of asymmetrical V-shaped microshield line, based on a conformal mapping procedure. These formulas give very accurate results in terms of elementary functions rather than the exact solution in terms of difficult functions. Two sets of expressions are described using first and second order approximations. These equations are easy to implement, thus making it an excellent choice for use in computer aided design, analysis and optimization of V-shaped microshield structures.

A good estimate of the coupling effect between parallel coplanar waveguide (CPW) lines is important, especially for monolithic microwave integrated circuit (MMIC) applications where unnecessary crosstalk between conductors could be a serious problem. This paper shows how these coupling parameters may be analytically obtained in the presence of the back-face metallization. Closed-form formulas are developed for evaluating the quasi-TEM characteristic parameters based upon the conformal-mapping method (CMM). Very good agreement is observed between the values produced by these formulas and by a spectral-domain method (SDM). Index Terms - Coplanar waveguide, coupled lines.

In this paper, a new type of V-shaped conductor-backed coplanar waveguide (VGCPW) is proposed. The characteristic impedance of the new line is obtained analytically using conformal mapping method under the assumption of pure-TEM propagation and zero dispersion. Direct solutions for the quasistatic normal electric field components and cumulative electric flux distribution across conductor surfaces are also presented. The numerical results show how the total electric flux terminating on the conductor surfaces varies in terms of the CPW's geometry and substrate parameters.

This paper examines both theoretically and experimentally the dependency of in-band noise performance upon circuit and device parameters of microwave filters employing negative-resistance compensation. By neglecting the influence of the induced gate noise source, a general expression for evaluating the noise figure of a second-order active filter is derived as a function of design parameters such as the transistor's noise figure, inductor's quality factor, and filter's bandwidth. In addition, factors affecting the optimization of the overall noise figure of these filters are discussed. For verification, the measured performance of two 900-MHz experimental MESFET filters are included. Index Terms--Microwave active filters, negative-resistance, noise figure.

Achieving high output power and efficiency in GaAs MESFET oscillators is mainly hampered by the device's parasitics, its static I-V characteristics, and the circuit embedding impedance. In this paper, the derivation of the relationship between oscillator output power and various circuit and device parameters is presented. From these analytical expressions, optimum operating conditions for maximum oscillator output power and efficiency are determined. The analysis method employed here is based upon a quasi-linear approach and an open-loop model of the oscillator. The design procedure is verified by measurements on an experimental circuit, which have demonstrated a dc/radio-frequency conversion efficiency of 54%. Index Terms--MESFET, microwave oscillators, optimization.

This paper examines, both theoretically and experimentally, the dependency of the third-order intermodulation (IM) distortion and power saturation upon circuit and device parameters of an active bandpass filter using negative-resistance compensation. Nonlinear analysis is performed by means of the Volterra series formulation. We show that the IM distortion can be reduced by several orders of magnitude with suitable choice of external gate-source and feedback capacitance values. Measured performances of some 900-MHz experimental MESFET bandpass fillers are presented. Index Terms--Intermodulation distortion, microwave active filters, Voiterra series.