Tunable Frequency Range and Mismatch Adjustment for Comb-Line Bandpass Filters (Short Papers)

S-band comb-line filters can be tuned over a frequency range of approximately 200 percent of the design frequency. A simple technique is also described that compensates for impedance match and coupling deficiencies associated with the filter.     

Broad-Band Millimeter-Wave E-Plane Bandpass Filters (Short Papers)

An accurate method to obtain starting estimates for an E-plane bandpass filter CAD program recently developed by Shih, Itoh, and Bui is presented. Results agree very well with exact values for filter design with relative bandwidths exceeding 10 percent at W-band and D-band and 20 percent at lower frequencies.     

Bandpass Filters Using Nonlinear FM Surface-Wave Transducers (Short Papers)

A generalized FM method of obtaining bandpass filters using surface-wave delay lines is discussed. Two identical FM transducers are used as input and output. The FM function of the transducers is determined by the required passband.     

Design Equations for a Class of Wide-Band Bandpass Filters (Short Papers)

Design equations and experimental data for a class of bandpass filters having up to two attenuation poles at finite frequencies in the stopband are presented. The new designs are obtained by a relatively simple modification of only the end sections of conventional interdigital and half-wave parallel coupled-line filters. Practical realizability constraints generally limit the design technique to wide-band flters.     

A Design Method of Bandpass Filters Using Dielectric-Filled Coaxial Resonators (Short Papers)

Design formulas for capacitively coupled bandpass filters using dielectric-filled coaxial resonators are derived and experimentally verified. The most important advantage of this filter is its ability to provide wide stopband characteristics for harmonics suppression. Its features can be obtained from the configuration using both quarter-wavelength uniform impedance resonators (UIR's) and stepped impedance resonators (SIR's).     

Mixed Mode Filters (Short Papers)

Mixed mode bandpass filters are described which utilize alternating TE/sub 011//spl deg/ and TE/sub n11//spl deg/ circular waveguide cavity modes. This novel filter configuration exhibits both excellent unloaded Q and spurious mode response characteristics. The use of mixed resonant modes makes possible the design of microwave filters for both in-line side wall connected cylindrical resonators as well as folded planar filter configurations, whereby cross-coupling between selected resonators can be realized.     

Predistortion Techniques for Multicoupled Resonator Filters (Short Papers)

This paper presents predistorted, Iossy design techniques as applied to general, multicoupled, resonator networks. The analytical procedure predistorts the poles of the transfer function to recover the Iossless passband flatness at the expense of insertion loss. Experimental results on 4- and 6-pole elliptic-function filters confirm the validity of the theory. These techniques should lead to significant system efficiencies in applications such as satellite transponder input multiplexer.     

Surface Wave on a Ferrite Magnetized Perpendicular the Interface (Short Papers)

A semi-infinite ferrite magnetized perpendicular to the interface is found to support a nonmagnetostatic surface wave. The wave exists within a finite wavelength band and a finite frequency band. Since the wavelength is typically of the order of 1 cm, large samples of polycrystalline ferrite material may be used for the experiments.     

Design of Nonradiative Dielectric Waveguide Filters (Short Papers)

An efficient design technique of nonradiative dielectric waveguide filters for use at millimeter wavelengths is developed. Filter stuctures considered here are a gap-coupled type and an altenating-width type. According to present theory, 3-pole, 0.1-dB Chebyshev ripple bandpass filters with a 2-percent bandwidth at a center frequency of 49.5 GHz were designed and fabricated with Teflon dielectric. Calculated and measured filter responses agree quite well, and excess insertion losses are found to be as small as 0.3 dB for both types of the fabricated filter circuits.     

E-Plane Integrated Parallel-Strip Screen Waveguide Filters (Short Papers)

A rigorous field theory design of a class of rectangular waveguide screen fiIters is presented which achieves improved attenuation in the upper stopband. The method of field expansion into suitable eigenmodes used considers the effects of the finite rectangular E-plane grid thickness and the mutual higher order mode interaction of the single screens. Calculated results up to 55 GHz show that the peak attenuation in the upper stopband for a Ka-band (26-40-GHz) two-resonators filter example with a midband frequency of f/sub 0/= 37 GHz is about 70 dB, whereas its planar circuit single-metal-insert counterpart reaches only about 34 dB. A Ku-band (12- 18-GHz) filter prototype with three metal-etched screens yields a measured passband insertion loss of 0.8 dB at about f/sub 0/= 17 GHz and a measured attenuation in upper stopband of about 50 dB up to 25 GHz.     

Stripline Triplexer for Use in Narrow-Bandwidth Multichannel Filters (Short Papers)

Design techniques and equivalent circuits are presented for constructing a printed-circuit narrow-bandwidth complementary triplexer filter. The techniques and circuits described allow the construction of contiguous-band multichannel filters using printed circuits with no shorted stubs. A unit was designed and constructed to give a three-percent relative bandwidth for each separate channel. The agreement between theory and experiment was in the range of measurement accuracy.     

Prototype Characteristics for a Class of Dual-Mode Filters (Short Papers)

Selected prototype characteristics of nonequiripple antimetric elliptic-function filters which can be realized in orthogonal cascaded dual-mode circular or square waveguide structures are presented. Cavity-coupling data for 4-, 6-, and S-section 0.01- and 0.05-dB-ripple passband designs with variable stopband levels are tabulated. Quantitative comparisons of elliptic and Chebyshev filter designs are also discussed, indicating the superior characteristics of elliptic networks.     

A Programmable Surface Acoustic Wave Matched Filter for Phase-Coded Spread Spectrum Waveforms (Short Papers)

A programmable surface acoustic wave (SAW) matched filter for biphase-coded spread spectrum waveforms has been constructed using a temperature-stable ST-cut quartz tapped delay line (TDL) and silicon-on-sapphire integrated control circuits. Construction is hybrid with wire stitch bond interconnections between the acoustic and microelectronic portions of the device. The SAW TDL operates at 120-MHz center frequency with 100-ns spacing between adjacent taps for a 10-MHz chip rate. The output of each tap can be individually switched to a load with 0 or 180/spl deg/ phase shift by the silicon-on-sapphire integrated control circuits. The high-speed capability of silicon-on-sapphire integrated circuits allows programming (code changing) to be achieved with a serial data input at 10-MHz rates, while the low temperature coefficient of ST-cut quartz allows satisfactory operation over a wide temperature range (-25/spl deg/C to +85/spl deg/C).     

Synthesis of RC Bandpass Filters

For the first time a method of designing RC bandpass filters is presented. The method consists of two steps. The first step is a scheme to locate the necessary poles and zeros that are RC realizable to produce certain bandpass characteristics. The second step is the synthesis of RC networks to produce these poles and zeros. In the first step, the conformal transformati begin{equation*}s(z) = {left(frac{sn^{2}(z,k) - sn^{2}(alpha{K,k})}{sn^{2}(alpha{K,k})[1 - k^{2}sn^{2}(alpha{K,k})sn^{2}(z,k)]}right)}^{1/2}end{equation*} is used to map the complex frequency s plane into a rectangle in the z plane such that the passband becomes one side, and a part of the negative real axis becomes the opposite side of the rectangle. In the z plane, if poles are located along certain portions of the border and zeros in the interior of the rectangle, certain passband and stopband behavior can be achieved. Among the useful characteristics obtainable by this scheme, the following are three outstanding examples: 1) characteristics that are equal-ripple in the passband and monotonic in the stopband; 2) characteristics that are equal-ripple in the passband and have a number of transmission zeros in the stopband; and 3) characteristics with a maximum gain at the band center and monotonic elsewhere. The steepness of attenuation outside the passband can be altered by a change in the numbers of zeros at the origin and infinity.     

Improved Accuracy for Commensurate-Line Synthesis (Short Papers)

By employing a simple transformation that preserves numerical accuracy, improved precision is obtainable using a Richards' extraction technique to obtain characteristic impedances of commensurate transmission-line structures. Furthermore, reduced sensitivity to coefficient truncation can result in computational savings.     

Design of Optimum Acoustic Surface Wave Delay Lines at Microwave Frequencies (Short Papers)

Optimum procedures for designing microwave acoustic surface wave delay lines are given. Combined beam steering fraction loss curves are provided as a function of the basic material parameter, the slope of the power flow angle, to allow optimum choice of material for a given application. Methods for designing uniform periodic interdigital transducers including finger ohmic loss, lossy tuning elements, and parasitic capacitance have been extended to account for beam steering and diffraction.     

An Evanescent Mode Waveguide Bandpass Filter at Q Band (Short Papers)

Evanescent-mode filters have previously been restricted in frequency to X band or below. Here, the performance of an evanescent-mode waveguide bandpass filter with a center frequency in the 26-40-GHz band (Q band) is reported.     

Wave Propagation on Nonuniform Transmission Lines (Short Papers)

The problem of wave propagation on nonuniform transmission lines is studied. Equations are presented not only for the reflection coefficient but for the transmission and admittance properties as well. They are valid under the assumption that only one mode of propagation exists on the line and that the properties do not change so rapidly that the fundamental transmission line equations are no longer applicable. Since all equations are derived for arbitrary load conditions, an extremely versatile solution of the problem has been obtained.     

Magnetostatic Forward Volume Wave Propagation-Finite Width (Short Papers)

The infinite radiation resistance encountered at the low end of the magnetostatic forward volume wave frequency band for a YIG layer of finite width is avoided by employing a physically justifiable low frequency cutoff value higher than that for which radiation resistance would be infinite. Radiation reactance and insertion loss then can be calculated and are found to be relatively insensitive to the choice of the cutoff frequency, except for frequencies very close to cutoff. Beam spreading considerations determine the cutoff frequency.     

E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations.