Microstrip Lowpass Filter Research Articles

Compact microstrip lowpass filter

A novel compact microstrip lowpass filter using the slow-wave resonator is described. This filter has the advantages of low insertion loss in the passband, high and wide rejection in the stopband and compact size. A demonstration filter is designed, fabricated and tested. Theoretical and experimental results are presented.

Compact microstrip lowpass filter using shunt open stubs and coupled slots on ground plane

A compact microstrip lowpass filter with prominent cutoff sharpness and very wide stopband is presented. The microstrip lowpass filter is composed of a transmission line with shunt open stubs on the topside of the microstrip structure and coupled slots on the ground plane. The shunt open stub microstrip filter with slots on the ground plane has a wide stopband at high frequency, and the coupled slot on the ground plane has sharp cutoff response at low frequency. The combined characteristics of these structures make for an excellent lowpass filter performance.

Control of Bandstop Response of Hi–Lo Microstrip Low-Pass Filter Using Slot in Ground Plane

This paper examines the effect of the geometrical shapes of a defected ground-plane structure (DGS) slot on performance of the Hi-Lo microstrip low-pass filter (LPF). A three-pole LPF based on an arrowhead DGS slot has 67% less length as compared to a conventional three-pole LPF. It has insertion loss of 0.5 dB and 15-dB rejection in the stopband up to three times the cutoff frequency.

A single‐port, dual‐frequency SSFIP antenna integrating a low‐pass filter

AbstractA new, very simple concept is proposed for realizing dual‐frequency antennas with arbitrary frequency separation. This idea is based on the SSFIP antenna principle and the use of a microstrip lowpass filter. It can be easily extended to any number of frequencies by simply adding antenna elements and low‐pass filters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 472–475, 2003

Numerically distributed circuit parameters model on microstrip transmission line circuits and its application on CAD

AbstractA new numerical model of microstrip transmission line circuits in terms of distributed circuit parameters is here illustrated. Based on full‐wave electromagnetic results, the extraction methods of these distributed circuit parameters on different types of microstrip transmission line circuits are introduced. As a preparatory experiment, an improved CAD method using this model is tested on microstrip low‐pass filter. Copyright © 2003 John Wiley & Sons, Ltd.

Application of C-COM for microwave integrated-circuit modeling

The concurrent complementary operators method (C-COM) is extended to simulate microwave planar circuits with the finite-difference time-domain (FDTD) method for the first time. The dispersive boundary condition (DBC) and its complementary operator are used to truncate the FDTD lattices and the fields in the boundary layers are calculated, respectively. Then these two simulations are averaged to annihilate the first-order reflections. Numerical error analysis shows that the performance of the DBC is improved greatly due to the implementation of complementary operators, and the setup of its parameters becomes easier and more robust. A flexible and high-performance absorbing boundary condition is thus obtained through the combination of the DBC and C-COM. This method has been successfully used to simulate a variety of planar circuit structures. Simulations of a microstrip low-pass filter, coupled-line bandpass filter, modified microstrip transmission lines, and dielectric resonator antenna, are presented in this paper.

Tapered photonic bandgap microstrip lowpass filters: design and realisation

The application of tapering techniques to two-dimensional photonic bandgap (2D-PBG) microstrip structures allows great improvement in the sidelobe level of the S11 scattering parameter and, consequently, a very flat passband. In this paper, many tapering windows are proposed for 2D-PBG canonical (straight microstrip line) stopband filters. By suitably designing three rows of tapered periodic structures which are characterised by different centre frequency of the stopband, a novel photonic bandgap lowpass filter was realised and characterised. Numerical simulations show satisfactory agreement with experiments.

Compact tapered photonic bandgap microstrip lowpass filter

A novel tapered two-dimensional photonic bandgap microstrip structure is proposed for increasing the stopband of a lowpass filter. The compact structure, obtained using a meander conductive line and etching in the ground plane a single row of two series of circles, the former Kaiser tapered and the latter of uniform circles, characterised by a different centre frequency of the stopband, shows a very wide stopband. The experimental results show excellent agreement with the numerical ones.

Broadband property and time‐domain application of general transmission‐line equations on microstrip low‐pass filter

AbstractGeneral transmission‐line equations based on the theory of differential equations [1] were introduced in [2] and [3]. The equations' dispersion characteristic of a microstrip low‐pass filter is studied. The parameters L, C, α, and β of general transmission‐line equations are found to be almost invariant to frequency in the passband of the microstrip low‐pass filter. By restoring current and voltage distributions with the use of equations in both frequency and time domains, the broadband property of these equations on the microstrip low‐pass filter is evident. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 123–126, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10250

Lowpass filter for spurious suppression

A novel microstrip-type lowpass filter is proposed to effectively suppress the spurious passbands. It is composed of series microstrips and open-ended microstrips with thin or thick film resistors appropriately inserted. The proposed lowpass filter was shown to suppress the spurious responses by more than 20 dB compared with a conventional microstrip lowpass filter.

Microstrip lowpass filter with multislots on groundplane

A microstrip line structure with backside transverse multislots is proposed for a microwave lowpass filter. The developed equivalent CAD model, based on network analysis, is used effectively to design a multistage microstrip lowpass filter. Numerical simulation and measurement confirm the validity of the proposed lowpass filter configuration and the efficient analysis and design procedure.

Numerical simulation of microstrip resonators and filters using the ADI-FDTD method

In this paper, we derived the characteristics of typical and practical microstrip components such as microstrip linear resonators and microstrip low-pass filters using the alternating-direction-implicit-finite-difference-time-domain (ADI-FDTD) method to examine the calculation accuracy and efficiency of the method. The resonators and the filters included very narrow gaps and strips, respectively. In this case, very fine cells must be applied there for the finite-difference time-domain (FDTD) modeling. In the conventional FDTD method, fine cells cause a reduction of the time-step size because of the Courant-Friedrich-Levy (CFL) stability condition, which results in an increase in calculation time. In the ADI-FDTD method, on the other hand, a larger time-step size than the CFL stability condition limitation could be set. We compared the results of the ADI-FDTD method for various time-step sizes with the results of the conventional FDTD method and measured data.

Finite Difference Time Domain (FDTD) Analysis of Microwave Circuits—A Review with Examples

Finite Difference Time Domain (FDTD) technique is used extensively in the analysis and design of microwave problems. This technique is reviewed here in a tutorial fashion. The various aspects of FDTD dealt with are: stability criteria, numerical dispersion, various types of absorbing boundary conditions, excitation schemes and source modeling. A number of examples are worked out to describe the application of FDTD to microwave circuits and transmission lines. These include: modes in a waveguide cavity, propagation constant of parallel plate waveguide and microstrip line, characteristic impedance of microstrip line, S-parameters of microstrip patch antenna and microstrip low pass filter. Extraction of propagation constant in case of multimode propagation is also discussed. To bring out the real time animation display characteristic of this technique, the propagation of time domain pulse in a microstrip patch antenna is plotted in 3-D.

Microwave microstrip low-pass filters using high- Tc superconducting YBaCuO thin films on LaAlO 3

We have characterized a 5-pole Tchebychev microstrip low-pass filter using YBaCuO thin film with a 5.3 GHz cutoff frequency. The YBaCuO thin film is grown on a LaAlO 3 substrate by means of magnetron sputtering. A matrix modeling of the filter coincides quite well with experimental measurement. Performances of the YBaCuO filter are compared with a gold filter made in the same conditions and with the same pattern. The average insertion loss and the rejection slope are appreciably better with the superconductor filter. Finally, the performances of the superconducting filter are studied at various temperatures and they remain approximately constant up to the transition temperature.

Application of the AWE method with the 3-D TVFEM to model spectral responses of passive microwave components

This paper describes an efficient algorithm to evaluate the spectral response of passive microwave devices. The method is based on the combination of the tangential-vector finite-element method (TVFEM) for modeling three-dimensional (3-D) microwave passive components and the asymptotic waveform evaluation (AWE) technique for efficiently computing the spectral responses. Unlike previous AWE approaches, which use direct matrix factorization to solve for the moments, we employ a preconditioned conjugate gradient (PCG) method. It is observed that the iterative PCG solver converges much faster by solving only the additional components of the higher moments outside the span of previous moments. Moreover, this paper discusses the effect of shifting the expansion frequency from the real frequency axis to the lower half of the complex frequency plane. Through several numerical examples, a waveguide with an obstacle inside, mitered 90/spl deg/ E- and H-plane waveguide bend, microstrip low-pass filter, and microstrip patch antenna, we show that shifting reduces the pollution due to dominant resonant modes and, consequently, results in a much wider convergence range for the moment-matching AWE technique.

Multiresolution analysis similar to the FDTD method-derivation and application

A three-dimensional (3-D) multiresolution analysis procedure similar to the finite-difference time-domain (FDTD) method is derived using a complete set of three-dimensional orthonormal bases of Haar scaling and wavelet functions. The expansion of the electric and the magnetic fields in these basis functions leads to the time iterative difference approximation of Maxwell's equations that is similar to the FDTD method. This technique effectively models realistic microwave passive components by virtue of its multiresolution property; the computational time is reduced approximately by half compared to the FDTD method. The proposed technique is validated by analyzing several 3-D rectangular resonators with inhomogeneous dielectric loading. It is also applied to the analyses of microwave passive devices with open boundaries such as microstrip low-pass filters and spiral inductors to extract their S-parameters and field distributions. The results of the proposed technique agree well with those of the traditional FDTD method.

Microwave multipole lowpass and bandpass filters fabricated by high-T/sub c/ superconducting thin films

The design, fabrication, and measurement of 7-pole microstrip lowpass filters and 4-pole parallel coupled-line bandpass filters using superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ epitaxial thin films are presented. The YBa/sub 2/Cu/sub 3/O/sub 7-x/ films were grown in situ at 770/spl deg/C and 200 mTorr oxygen partial pressure in a pulsed laser deposition system. The 7-pole microstrip-line lowpass filter and 4-pole parallel coupled-line bandpass filter patterned on the laser ablated YBCO films with dimension of 20 cm/spl times/10 cm/spl times/0.5 mmt were generated using photolithographic and wet etching processes. The complete devices packaged in a 3-component type brass test-fixture were characterized. The results showed the center frequency of 11.2 GHz with 6% bandwith and less than 1 dB insertion loss(IL) for the case of bandpass filters below 77 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microstrip filter design using direct EM field simulation

For the first time, we present minimax filter design with electromagnetic (EM) simulations driven directly by a gradient-based optimizer. Challenges of efficiency, discretization of geometrical dimensions, and continuity of optimization variables are overcome by a three-stage attack: 1) efficient on-line response interpolation with respect to geometrical dimensions of microstrip structures simulated with fixed grid sizes; 2) smooth and accurate gradient evaluation for use in conjunction with the proposed interpolation; and 3) storing the results of expensive EM simulations in a dynamically updated database. Simulation of a lowpass microstrip filter illustrates the conventional use of EM simulation for design validation. Design optimization of a double folded stub bandstop filter and of a millimeter-wave 26-40 GHz interdigital capacitor bandpass microstrip filter illustrates the new technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Efficient implementation of the spectral domain method including precalculated corner basis functions

A general implementation of the Spectral Domain Method, formulated for planar microstrip circuits of arbitrary metallisation pattern is presented. The inclusion of a priori knowledge of the edge and corner singularities in the set of basis functions results in a large decrease In the order of the problem to be solved. Libraries of basis functions allow the rapid rigorous analysis of realistically complex circuits. Calculated S-parameters are given for three microstrip lowpass filters and compared to results from both measured data and other techniques.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Scale-model design of a submillimeter-wave planar diode mixer

The design of a planar diode submillimeter-wave mixer is presented in which scale models play an important role. By constructing larger scale models of mixer components, the design process is simplified by making component changes easier and by making the measurements easier with the aid of a network analyzer. Separate scale model measurements were used to find optimum diode geometry, a wide bandwidth transition from circular waveguide to shielded microstrip, a DC return bondwire, and a microstrip low-pass filter. After combining the results from these measurements to form a mixer circuit model, the combined effect of the various components was studied, and adjustments were made to present an optimum impedance to the diode terminals. Tests of the design at 345 GHz confirm the accuracy of the scale model design procedure. Design information presented on the different components will be useful for developing future planar diode mixers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>