Design of Coupled Microstrip Lines by Optimization Methods (Short Paper)

The design of two coupled microstrip lines is converted into an optimization problem, which is then solved by two methods of nonlinear mathematical programming. New formulas for calculating the first approximation of the solution, i.e., the starting point of the optimization, are given.     

On the Analysis and Design of Three Coupled Microstrip Lines (Short Paper)

The general configuration of a system of three coupled microstrip lines is analyzed and its parameters (mode numbers, effective dielectric constants, and modal impedances) are derived in terms of the system capacitances. These capacitances were computed by using the network analog method. In this paper, it is shown that for a system of three equal-width lines, there are, in general, the normal-mode impedances (four of which are independent). This would make the design of a system based on three equal-width lines, mainly with narrow strips and narrow separations, rather complicated. For a system of three equal-impedance lines, the number of mode impedances reduces to only three, which would facilitate the design. This latter system can be achieved by an appropriate increase of the width of the center line relative to that of the outer lines. Thus, a set of curves and a corresponding formula are obtained to determine this relative increase as a function of the geometric parameters. A complete set of design data for the new geometric configuration are also given. The experimental results of two fabricated three-line couplers, one based on the present data and the second on other published data, are compared.     

Loss Calculations of Coupled Microstrip Lines (Short Papers)

Loss calculations have been performed to yield useful data relevant to the complementary odd and even modes propagating along a pair of identical coupled microstrip lines. The calculations are based on methods applied to the single-line case and indicate substantial differences in attenuation occurring between the odd and even modes for particular geometries.     

Tolerance Analysis of Shielded Microstrip Lines (Short Paper)

A complete analysis of the sensitivities of shielded microstrips is presented. The sensitivity formulas form the basis for studying the effect of tolerances on the performance of these circuits. A set of sensitivity curves are given to help the design procedure. It is suggested that the position of the top cover can be adjusted to compensate for some of the effects of the manufacturing tolerances. Practical examples are given to support the suggested procedure.     

Transient Analysis of Partially Coupled Lines (Short Paper)

We propose a time-domain analysis method for partially coupled Iines by dividing them into "tubes." A tube of order N is a set of N coupled lines of equal lengths for which transient analysis based on modal decomposition is well known. An interface problem occurs at the junction of tubes of different orders. Such a case is analyzed by introducing two operators, called dilatation and shrinkage.     

Dimensions of Microstrip Coupled Lines and Interdigital Structures (Short Papers)

A method is presented for finding dimensions of coupled lines and interdigital structures on microstrip given the electrical properties. Both a graphical approach and computer approach using polynomial approximations are given. These results are within 1 percent of Bryant and Weiss' dimensions for coupled lines for most practical stripwidths and spacings. Experimental data for a 10-percent bandwidth microstrip interdigital filter are given.     

Parameters of Microstrip Transmission Lines and of Coupled Pairs of Microstrip Lines

A theoretical analysis is presented of microwave propagation on microstrip, with particular reference to the case of coupled pairs of microstrip lines. Data on this type of transmission line are needed for the design of directional couplers, filters, and other components in microwave integrated circuits. The inhomogeneous medium, consisting of the dielectric substrate and the vacuum above it, is treated in a rigorous manner through the use of a "dielectric Green's function" which expresses the discontinuity of the fields at the dielectric-vacuum interface. Results are presented in graphical form for substrate dielectric constants of 1, 9, and 16, and a range of values of width and spacing of the strips. Numerical tables for these and other cases are also available. The tables present capacitance, characteristic impedance, and velocity of propagation of the even and odd normal modes. The method lends itself to the treatment of other geometries which are of practical interest, such as "thick" strips, presence of an unsymmetrically located upper ground plane, etc.     

Characteristics of Some Asymmetrical Coupled Transmission Lines (Short Paper)

In this paper, expressions for the characteristics of some asymmetrical coupled transmission lines are derived. These include expressions for the capacitances, impedances, and phase velocities of asymmetrical coplanar strips, asymmetric coupled striplines, and asymmetric coupled microstriplines. Accuracy of these expressions is compared against available numerical results obtained rising varous numerical methods.     

Measured Odd- and Even-Mode Dispersion of Coupled Microstrip Lines (Short Papers)

A convenient method is described for the measurement of the odd- and even-mode phase velocities of coupled microstrip lines. Results are presented which show the strong influence on the dispersion characteristics of a closely spaced low-loss shielding cover. The method also enables the loss of the odd and even modes to be determined.     

Design of Coupled Microstrip Lines (Letters)

An accurate and direct method for designing coupled microstrip lines for any substrate is given once the design curves for any other substrate are known.     

Multilayer Microstrip Transmission Lines (Short Papers)

A method used to treat covered microstrip is extended to multilayer microstrip. Detailed results are obtained for the general three-layer problem. Series expansion and term-by-term integration are used to obtain a closed form expression for the Green's function. Matrix methods are then used to obtain the characteristic impedance. Data obtained agree closely with experiment.     

Shunt-Connected Microstrip Radial Stubs (Short Paper)

Radial-line stabs provide an interesting alternative to low-impedance conventional straight stubs.They are useful as filter elements in both series and shunt configurations. In this short paper, the planar circuit analysis previously performed for a series-connected radial stub is extended to the shunt configuration. Theoretical and experimental results are presented to verify the equivalent model for the shunt-connected radial stub.     

Equivalent Circuit Parameters of Microstrip Step Change in Width and Cross Junctions (Short Papers)

The inductive component of the equivalent circuit of microstrip step change in width and cross junctions has been evaluated theoretically and a comprehensive set of results is presented. Experimental results for one set of step changes in width obtained using the resonant method compare well with theory.     

Dielectric Loss in Microstrip Lines (Short Papers)

A new technique is presented for calculating dielectric loss in microstrip lines. Numerical results for several different substrates are included. These are compared with other available results and experimental data.     

A Novel Low-Noise Downconverter System Using A Microstrip Coupled Transmission-Mode Dielectric Resonator (Short Paper)

A low-noise downconverter system for microwave downlink applications is presented. Although most downconverters with an internally generated local oscillator have been designed utilizing MESFET's and DGFET's, the circuit described herein uses a silicon bipolar Darlington pair as its active device and a dielectric resonator for feedback. Downconverters of the latter type have been realized with noise figures as low as 4.57 dB and conversion gains of 7 dB over an intermediate frequency range from 0.6 to 1.8 GHz.     

New Quasi-Static Models for the Computer-Aided Design of Suspended and Inverted Microstrip Lines (Short Paper)

New quasi-static models for the computer-aided design (CAD) and analysis of open suspended and inverted microstrip lines are reported. The models are obtained through generalizing those reported earlier and are applicable up to epsilon/sub r/= 20, thereby covering all the practically used substrate materials for these structures. The models also cover a larger range of dimension ratios and are accurate to within 0.6 percent for analysis and within 1 percent for synthesis.     

全等宽平行耦合微带线带通滤波器的设计

半波长平行耦合微带线带通滤波器由于其结构紧凑,第二通带的中心频率3倍于主通带中心频率,因而在微波集成电路中获得广泛应用。本文提出一种新的设计方法：耦合线节级联直接设计法。这一方法比传统设计方法简便,适用相对带宽范围较宽,为30～80%,而且可以采用全等宽耦合线,因而滤波器结构简洁。     

Planar Circuit Analysis of Microstrip Radial Stub (Short Paper)

Radial-line stubs have been found to work better than low-impedance rectangular stubs when an accurate localization of a zero-point impedance is needed. In this paper, microstrip radial-line stubs are analyzed using a planar circuit technique and characterized for design purposes. Experiments performed on various structures are in excellent agreement with the theory and confirm the suitability of such a structure as an altenative to a conventional straight stub.     

Millimeter-Wave Oscillators Using Image-Line or Microstrip Waveguides (Short Paper)

A low-cost Gunn oscillator using a coaxial cavity coupled into either dielectric image guide or microstrip line has been developed. A unique feature is the broad frequency range off mechanical tunability of 10 to 11 GHz centered around 56 GHz. This range of tunability is beyond the range of standard metal waveguide cavities. Power levels up to 43 mW have been observed in image-line structures and 20 mW for microstrip lines. The construction allows an easy and quick replacement of diodes, when necessary hence, the structure is easily modified to operate in different ranges.     

The Design of Coupled Microstrip Lines

Although graphical results and formulas are available for the design of microstrip couplers, the design procedure is hampered because even- and odd-mode impedances are always expressed in terms of the physical geometry. In practice the designer obtains these impedances and then requires to know the geometry given by them. A new design procedure for coupled parallel microstrip lines is therefore presented. The technique enables the geometry of the coupled lines to be obtained directly from the required even- and odd-mode impedances and uses single microstrip-line geometry as an intermediate step. The results are presented in graphical form using only two universal families of curves. Results are also presented in the form of simple formulas for design programs and also comparisons with practical results are made.