Suspended Substrate Stripline Research Articles

Design model for broadside‐coupled suspended substrate stripline for microwave and millimeter‐wave applications

AbstractSimple closed‐form expressions for the analysis of broadside coupled suspended substrate stripline is presented. The expressions are valid over a wide range of structural parameters and dielectric constants. The validity range of this expression for structural parameters is 1.0 ≤ εr ≤ 30.0 (dielectric constant), 0.2 ≤ W/b ≤ 10.0 (strip width), and d/b ≤ 0.5 (substrate thickness). The average accuracies of the present expressions are <0.8% and <0.6% for even‐ and odd‐mode impedances, respectively. The maximum deviation is ±1.25% and ±1.16% for even‐ and odd‐mode impedances with respect to the reference values. This closed‐form model is useful for the interactive CAD analysis of microwave and millimeter‐wave circuit. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 328–331, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20293

Switched bandstop filters

AbstractA new prototype network is derived for a class of allpass networks from which, by a simple switch operation, a cascaded element bandstop filter results. an explicit solution for element values is obtained for the even‐ and odddegree solutions of arbitrary degree. the performance of various degrees is investigated and experimental results are presented for a fifth‐degree suspended substrate stripline bandstop filter operating over a narrow band at 10 GHz.

Autoregressive (AR) and autoregressive moving average (ARMA) spectral estimation techniques for faster TLM analysis of microwave structures

Autoregressive (AR) and autoregressive moving average (ARMA) techniques have been successfully implemented in conjunction with the transmission line matrix (TLM) method for efficient time-domain analysis of microwave structures. The AR technique can be used to compute the full time-domain response from a relatively short segment of the early TLM response. It was found that the least-square technique of estimating the AR parameters requires a shorter time record than solving Yule-Walker equations through the Levinson-Durbin algorithm. The ARMA technique can be used to compute the scattering parameters of microwave structures without using the discrete Fourier transform. A recursive least square covariance ladder algorithm has been used for ARMA modeling. Both AR and ARMA models have been validated by applying them to waveguide and suspended substrate stripline filters. With these techniques, the speed of the computationally intensive TLM algorithm can be increased up to five times. >

W Band Mixer in Planar Configuration

This paper describes the design and fabrication of millimeter wave balanced mixer, using commercially available Schottky barrier beam lead diodes and planar circuit techniques. The design of RF, LO and IF matching circuits are described. The beam lead Schottky barrier diodes were subjected to test (before being bonded to mixer circuit) for their I-V characteristics and match paired for better AM noise cancellation and for optimum diode parasitic losses. The mixer circuit has been realized on 125 micron thick RT Duroid substrate involving symmetrical unilateral finline in E plane of a rectangular metal waveguide housing and suspended substrate strip line configuration, integrated on a single substrate. A conversion loss of 10.5 dB, noise figure of 8 dB (DSB) and RF to LO isolation better than 21 dB have been achieved with + 13 dBm LO power.

K-band quasi-planar tapped combline filter and diplexer

Quasi-planar realizations of a combline bandpass filter and diplexer using multiple coupled suspended substrate striplines (MCSSSs) have demonstrated good performance at K-band without any tuning. The N MCSSSs excite N zero-cutoff-frequency quasi-TEM modes. A computer-aided filter design approach employing a rigorous spectral domain approach and 2N-port microwave circuit theory accounts for the effects of the N quasi-TEM modes, the couplings through nonadjacent MCSSSs, and cover height. Two 19.5-20.5 GHz MCSSS combline filters with different cover heights have been built and tested to compare their filter characteristics. The reduction in cover height has been found to decrease the amount of nonadjacent coupling through MCSSSs and to result in better filter stopband performance. An 18.5-19 GHz and 20-20.5 GHz MCSSS diplexer is also presented. All the measured results for the combline filters and diplexers agree well with the theoretic calculations. >

The design and development of a 140GHz beam-lead diode subharmonically pumped mixer

The possibility of using beam-lead diodes in the design of a 140GHz subharmonically pumped mixer was investigated. An easily assembled, rugged mixer structure was developed which avoids the problems associated with present production techniques and reduces costs. The construction of the circuit developed makes it ideally suited to space and other environmentally demanding application. Computer analysis techniques were used to predict millimetre-wave performance and a large-scale low-frequency model was used to optimize the circuit. The millimetre-wave mixer was constructed using a circuit implemented on suspended substrate stripline. Results of millimetre-wave performance are presented.

Design of a three-dimensional gap-coupled suspended substrate stripline bandpass filter

A three-dimensional gap-coupled sus- pended substrate stripline (SSS) bandpass filter, based on the modified configuration of the classic end-coupled filter, is presented. It consists of printed half-wavelength resonators placed on the same and/or the opposite sides of the suspended substrate. These resonators orient themselves in arbitrary directions. Such an arrangment makes the new filter highly flexible to interface with other microwave subcircuit modules. The filter is con- structed in a bent channelised housing that sup- presses any possibility of exciting higher-order modes, except the dominant quasi-TEM mode of propagation. Consequently, the channelised filter is free from any coupling between itself and other microwave circuit components within the system. Two look-up tables, derived from a variational three-dimensional quasi-TEM spectral-domain analysis of the discontinuity problems associated with the adjacent gap-coupled resonators, are incorporated into the computer-aided design of the new filter. The de-embedded discontinuity parameters are validated by comparing them with those obtained by experiment and full-wave approaches for the microstrip open-end and the SSS end-coupled problems, respectively. The measured results for the experimental 21-22 GHz bandpass filter agree very well with the theoretic predictions considering the conductor losses (5.57 x lo-' dB/mm) of the SSS. It has less than 1.4 dB insertion loss and greater than 10dB return loss in the passband.

K-band suspended substrate stripline tapped combline filter

A newly developed 19.5–20.5 GHz combline bandpass filter realised by multiple coupled suspended substrate striplines (MCSSSs) and metal-insulator-metal (MIM) capacitors is presented. The filter design uses an iterative field-theory-based algorithm to account for the composite effects of multiple dominant quasi-TEM modes of the MCSSS and the couplings through the nonadjacent lines. A prototype is built and tested. The measured and theoretical filter characteristics are in good agreement for the combline filter without any tuning.

New equivalent circuits for inhomogeneous coupled lines with synthesis applications

Equivalent circuits for inhomogeneous coupled-line sections are presented which enable cascade synthesis procedure to be applied to the design of very-broadband inhomogeneous filters. Here, the term inhomogeneous means that the even and odd modes have different phase velocities and different electrical lengths. The method has been implemented in the design of inhomogeneous high-pass filters constructed in suspended substrate stripline, when the even-mode characteristic impedance is much greater than the odd-mode characteristic impedance. An approximate but highly accurate synthesis of a 3:1 bandwidth-inhomogeneous distributed high-pass filter is described. The procedure is almost purely analytic, and computer-aided design is required only for fine tuning adjustments. The theoretical feasibility of designing such filters for upper-pass bandwidths of greater than 8:1 is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Element values of a generalized Chebyshev prototype filter for suspended substrate stripline

An odd-degree lowpass prototype filter satisfying a generalized Chebyshev response with five transmission zeros at infinity and the remainder at a finite real frequency is presented. This prototype is synthesized using the alternating pole technique with little loss of accuracy for degrees up to 15. Two convenient forms of realization in suspended substrate stripline (SSS) are introduced. Tables of element values for commonly used specifications are given. These tables are suitable for the design of TEM-mode microwave filters and multiplexers having broad or narrow bandwidths.

Characteristics of single and coupled rectangular resonators in suspended substrate stripline

A rigorous spectral-domain analysis is carried out to determine the resonant frequency characteristics of resonators in a general suspended substrate stripline. The resonant frequency characteristics of single as well as coupled rectangular resonators are computed. An important observation for resonators in broadside-coupled suspended substrate stripline is that the even- and odd-mode resonant frequencies are considerably different.

Propagation in Broadside-Coupled Suspended-Substrate Stripline in E-Plane

The spectral-domain analysis is applied to the derivation of the propagation characteristics of the even and odd mode, for the broad-sidecoupled suspended-substrate stripline (BCSSS). The characteristic impedance, based on the current-power definition, as well as the effective permittivity are evaluated. Numerical results are presented illustrating the effects of several different dimensional parameters. Numerical results indicate a large spread between even- and odd-mode impedance for thin substrates (D/A < 0.045) and stripwidths ranging 0.046<= W/B<= 0.47, suggesting tight coupling. Negligible frequency dependence on odd-mode impedance is evident, as well as significant frequency effects on even-mode impedance. Considerable dispersion is shown to be present in the odd mode for wider strips. Measured results for a low-pass filter and cascaded transitions are presented.

Suspended substrate stripline filters for ESM applications

Suspended substrate stripline filters for ESM applications

An Efficient 200-290-GHz Frequency Tripler Incorporating a Novel Stripline Structure

This paper describes a broadly tuneable frequency tripler which can provide more than 2-mW output power at any frequency between 200 and 290 GHz. It is derived from an earlier narrow-band prototype design, with the major improvements being the use of a new low-pass filter design implemented using a novel suspended substrate stripline structure, an optimized waveguide transformer, and a lower loss contacting output backshort.

A Generalized Chebyshev Suspended Substrate Stripline Bandpass Filter

A design method for narrow-band suspended substrate strip-line filters having a true bandpass structure is presented. A generalized Chebyshev low-pass prototype is used, resulting in a convenient form of realization in suspended substrate stripline. A prototype device, designed with the aid of a computer program, is given as an example. Results from this device show that the method of realizing such a filter is viable for many applications and maybe suitable to replace more conventional types of microwave filter realized using TEM-mode resonators.

Electronically Tunable Microwave Bandpass Filters

Combline filters with novel input and output coupling networks which enable broad-band tuning to be achieved with minimum degradation in passband performance are discussed. Explicit design formulas for these filters are presented. Computer analysis of varactor tuned combine bandpass filters including the small signal varactor equivalent circuit is presented enabling filter performance to be easily evaluated. The design and experimental performance of a varactor tuned combline filter, realized in suspended substrate stripline is described. This filter toned from 3.2 GHz to 4.9 GHz exhibited low passband insertion loss and its performance was is close agreement with theoretical expectations.

A Novel Class of Generalized Chebyshev Low-Pass Prototype for Suspended Substrate Stripline Filters

A novel class of low-pass prototype filters having an equiripple passband response with three transmission zeros at infinity and the remainder at a finite real frequency is presented. The prototypes are synthesized using the alternating pole technique to obtain directly the even-mode or the odd-mode admittance and little accuracy is lost for prototypes up to degree 15. Tables of element values for commonly used specifications are included. The tables are useful for the design of TEM-mode microwave broad-band filters, diplexers, and multiplexers, particularly for a printed circuit form a realization. A design example of a low-pass microwave broad-band filter designed and constructed in suspended substrate stripline (SSS) configuration is given and experimental results are also presented.