Parallel-coupled Microstrip Bandpass Filter Research Articles

A novel Ka-band MMIC coupled filter with harmonic suppression

PurposeA novel Ka-band compact parallel-coupled microstrip bandpass filter with harmonic suppression performance has been designed, implemented and tested on GaAs MMIC.Design/methodology/approachThis proposed filter consists of modified coupled-line units with T-shaped open-stubs.FindingsThe proposed filter with T-shaped open-stubs is valuable in performance with low loss at fundamental frequency, suppression at harmonic frequencies and small size. The simulation is based on full-wave electromagnetic analysis and the measurement is based on chip test. It shows an insertion loss below 1.2 dB, return loss better than 20 dB in the pass band and high than 28 dB suppression at harmonic frequencies.Originality/valueThis Ka-band MMIC filter with harmonic suppression is attractive for the millimeter-wave system.

Novel Microstrip Band Pass Filter for C- Band Wireless Applications

In this paper, a novel approach for designing the parallel coupled microstrip bandpass filter operating at C-band frequency is numerically analyzed iteratively and simulated. The physical dimensions are being finalized using standard odd- even impedance method. Various electrical parameters such as insertion loss, reflection loss are being analyzed and practical results are being compared and found same as the predicted results. The proposed design is fabricated on FR4 dielectric substrate and the experimental result shows the scientifically acceptable for C-band Applications.

Design of compact multiband bandpass filter with suppression of second harmonic spurious by coupling gap reduction

In this paper, we describe a method to implement compact multiband bandpass filters with suppression of second harmonic frequency. This filter design approach is based on decreasing the coupling gap between adjacent resonators of a parallel-coupled-line bandpass filter in order to achieve both the desired multiband frequency response and the spurious suppression. We present the theoretical analysis of the proposed structure that consists of modeling the frequency dependence of the even- and odd-mode characteristic impedances as well as due to the different phase velocities of the parallel-coupled microstrip lines. As an example, a compact tri-band parallel-coupled-line bandpass filter with suppression of second harmonic frequency was implemented operating at 1.9/3.2/4.6 GHz to cover PCS1900, WiMAX, and C-band applications. A three-pole Chebyshev parallel-coupled microstrip bandpass filter was designed at a center frequency of 3.2 GHz and used as the basis to validate the gapping effect on the filter response which also achieves a narrower bandwidth for the second harmonic. Finally, the filter performance with minimized coupling gap is compared to a filter enhanced by the insertion of apertures in the ground plane. Generally speaking, good agreement was accomplished between simulated, calculated, and measured results.

Design of the Parallel Coupled Microstrip Bandpass Filter

A design method of microstrip filter with good isolation is presented. In the paper, the design method of microstrip bandpass filter is introduced, and one example filter with 3.075GHz center frequency, 9% relative bandwidth is given. With the aid of microwave HFSS software, the microstrip filter is simulated. The result of simulation shows the microstrip filter has an excellent frequency response.

Stepped-Impedance Coupled Resonators for Implementation of Parallel Coupled Microstrip Filters With Spurious Band Suppression

A parallel-coupled microstrip bandpass filter based on the stepped-impedance coupled resonator (SICR) for suppression of harmonic spurious response is presented. The SICR relies upon the incorporation of different stepped impedances for the even and odd propagation modes of the coupled microstrip lines. This is to align the modal parallel resonance frequencies, and thereby effectively equalize the modal phase velocities. Its structural simplicity enables closed-form analytical formulation, and the derived equations are effectively utilized to explicitly guide parameters selection based on classical synthesis methodology of coupled microstrip filters. Practical feasibility of the SICR and the integrity of the analysis are demonstrated via designs and implementations of two third-order 0.01-dB ripple Chebyshev bandpass filters with a passband center frequency of 2.0 GHz and 3-dB fractional bandwidths of 15% and 25%. Good agreement between design, simulation, and measurement is obtained, where suppressions of the first harmonic spurious responses by more than 40 dB are achieved in both filters.

Design and Optimization of Band Pass Filter for SoftwareDefined Radio Telescope

Design and optimization of a parallel-coupled microstrip bandpass filter for Software Defined Telescope is presented in this paper. The simulation and optimization is done using ADS and Momentum. The filter is designed and optimized at a center frequency of 1.42GHz. The filter is built on a relatively cheap substrate FR-4 with permittivity 4.4 r   and loss tangent . Simulation results reveal that the filter operation is optimum over the frequency range 1.41 GHz to 1.44 GHz. The 3 dB bandwidth is thus 300 MHz. the return loss is below -10 dB over the passband. Insertion loss is -2.806 dB in the passband. The filter is almost matched to the characteristic impedance ( 0 Z ), 50 Ohms. Also it is observed that the phase varies linearly with frequency. The filter once fabricated could be used at the radio receiver of the Software Radio Telescope to filter out terrestrial radio interference.

Study on Transmission Characteristics of Silicon-Based Microstrip Bandpass Filter

With the development of semiconductor process technology and IC design technology, silicon-based filter technology continuously improved. The filter’s transmission characteristics depend on the dielectric constant, dielectric loss and substrate thickness. This paper studies the frequency response characteristics of transmission coefficient and reflection coefficient of the parallel coupled microstrip bandpass filter, in the condition of silicon-based with different thickness, loss and doped concentration, when the center frequency is 5.75 GHz.

A Multilayered Parallel Coupled Microstrip Bandpass Filter With Embedded SIR Cells to Have a Broad Upper Rejection Band

This paper proposes a parallel coupled microstrip bandpass filter (BPF) with folded stepped impedance resonator (SIR) cells on the middle layer for spurious suppression. The folded SIR cells on the middle layer create a wide stopband by canceling the second and third harmonics of the parallel coupled microstrip BPF with suppression of over -50 and -30 dB, respectively. By selecting properly the impedance ratio (R) and physical length ratio (?) of the folded SIRs, the parallel coupled BPF with a wide stopband can be implemented without causing a package problem of degrading the complete ground plane. The proposed BPF is designed and fabricated. Good agreement between the electromagnetic (EM) simulation and measurement is obtained.

Triple‐band parallel coupled microstrip bandpass filter with dual coupled length input/output

AbstractA three‐order triple‐band bandpass filter is proposed to operate at 1.8/3.5/5.2 GHz for DCS, WIMAX, and WLAN applications. Three 1/2λ open‐loop resonators and two novel modified input/output structures parallel coupled are used as the bases. The cascaded resonators are designed for wide bandwidth and high out‐of‐band rejection. The modified input/output structure is used to tune the suppression/improvement of each spurious resonance. The filter is printed on Al2O3 ceramic substrate with 0.635 mm in thickness and has the relative dielectric constant 9.4. Because of the high dielectric constant substrate and novel feed in/out structure, the proposed filter with optimized parameters exhibits low insertion loss, high out‐of‐band rejection, wide bandwidth, and simple structure. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 995–997, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24257

Compact Electronically Switchable Parallel-Coupled Microstrip Bandpass Filter With Wide Stopband

In this letter, a compact electronically switchable parallel-coupled microstrip bandpass filter (BPF) based on quarter- wavelength resonators and p-i-n diode switch is proposed. The proposed filter occupies only half the circuit size of the conventional parallel-coupled filter. In addition, the type and length of each coupled-line section is suitably chosen such that the inherent transmission zeros associated with the coupled-lines can be used to reject the spurious passbands effectively. By adding only one p-i-n diode along with a simple bias control circuitry, the proposed filter becomes electronically switchable with no current consumption when the filter is turned off. Specifically, a switchable fourth-order microstrip BPF with a center frequency f0 of 2 GHz, passband insertion loss less than 3 dB, and wide stopband up to 7.7 f0 in the ON state is demonstrated. The isolation of the filter is better than 30 dB from dc up to 7.7 f0 in the OFF state.

Design of a Broadband Parallel-Coupled Microstrip Filters without Spurious Resonances

A design of parallel-coupled microstrip bandpass filters without spurious resonance is presented. Two different techniques are used to eliminate this response at twice the passband frequency (2fo). The first one is based on usage of suspended substrate, while the second is carried out by shorting the parallel-coupled lines to the ground plane through two shorting walls. The numerical results show that a broadband filter can be obtained by the suppression of the spurious response. The finite difference time domain (FDTD) with the perfect matched layer (PML) is used in the present analysis. The obtained results are compared with the available published data and good agreements are found.

Harmonic suppression in parallel coupled microstrip bandpass filter with embedded C‐shaped EBG cells

AbstractIn this article, harmonic suppression of a parallel coupled microstrip bandpass filter (BPF) with C‐shaped electromagnetic bandgap (EBG) cells embedded on the middle layer is investigated. The embedded C‐shaped EBG cells patterned on the middle layer add a good stopband‐rejection mode to the second harmonics of the parallel coupled microstrip BPF with suppression of over −40 dB, without affecting the center frequency and insertion loss of the original designed BPF. The experimented results matched the simulated results well. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2244–2246, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21918

A 10-35-GHz six-channel microstrip multiplexer for wide-band communication systems

A six-channel multiplexer composed of parallel-coupled microstrip bandpass filters is developed. The passbands of the filters, i.e., channel frequencies, are 10, 12, 19, 21, 32, and 35 GHz. The operating frequency range of the multiplexer is so wide that a new method of harmonic suppression is devised for the filters designed at 10 and 12 GHz. The method is simple and does not require any change to the conventional parallel-coupled microstrip bandpass filter. A design procedure for the microstrip multiplexer is then introduced with a rule to set up initial conditions for better optimization. The designed multiplexer does not need any tuning elements, and the measurement results show insertion losses between 2.0-3.2 dB for all six channels. The multiplexer developed in this paper has been used in the wide-band transceiver system.

Spurious Suppression of a Parallel Coupled Microstrip Bandpass Filter with Simple Ring EBG Cells on the Middle Layer

SUMMARY This paper proposes a parallel coupled microstrip band-pass filter (BPF) with ring Electromagnetic Bandgap (EBG) cells on themiddle layer for spurious suppression. The ring EBG cells of the middlelayer add a good stopband-rejection mode to the second harmonics of theparallel coupled microstrip BPF with suppression of over −50dB, withoutaffecting the center frequency and insertion loss of the original designedBPF. The design of ring EBG cells is presented and verified by the experi-mented results. key words: electromagnetic bandgap (EBG), bandpass filter (BPF), spuri-ous, suppression 1. Introduction Parallel-coupled bandpass filters (BPFs) are more favor-able to be used for planar microstrip filters in modern mi-crowave and wireless communication system, due to itsweightless, low cost and easy integration. However, spu-rious response is a well-known problem occurring at thetwo, three or four times of the fundamental frequency forconventional Parallel-coupled BPFs. It will cause poor har-monic responses as the parallel-coupled filters are used foroutput components of oscillators and amplifiers. Therefore,how to suppressing the spurious response is also an essen-tial issue on the conventional microstrip filters with half-wavelength or quarter-wavelength. While, the requirementsof the high performance filter in the sensitive receiver needsa wider upper stop-band for reducing the interference fromout-of-band signals, and therefore a cascaded lowpass filteror bandstop filter may be used to suppress the spurious re-sponse at cost of extra insertion loss and size. Recently, theapplication of electromagnetic bandgap (EBG) structures onmicrowave filters for rejecting spurious responses has at-tracted much interest [1]–[4]. In general, EBG structuresare periodic cells preventing the propagation of the electro-magnetic waves in a specified band of frequency [1]. Toachieve broad-stopband characteristics, some microstrip fil-ters have been designed and fabricated using EBG structure[1]–[3]. T. Itoh et at.[1] have reported the UC–PBG groundplane to suppress the spurious response of microstrip BPF

Compact parallel coupled HTS microstrip bandpass filters for wireless communications

A practical design methodology for a compact parallel-coupled microstrip bandpass filter structure with steep attenuation is introduced using a computer-aided full-wave electromagnetic (EM) simulation based on the method of moments. The structure consists of an array of fully aligned half-wavelength spiral-meander-line resonators. Aimed at the application in the front-end receiver of digital cellular communication service, a 12-pole high-temperature superconductor filter with 2.27% fractional bandwidth (FBW) at 883.0 MHz was designed. In order to utilize the limited wafer area further, a 15-pole filter with 803.0-MHz center frequency, 2.25% FBW is precisely designed with greater EM simulation effort. Both the filters are fabricated using thallium-barium-calcium-copper-oxide thin films on a 2-in lanthanum-aluminate (LaAlO/sub 3/) wafer. The S-parameter measurements show a good agreement with the simulated results. At 70 K, the 12-pole filter shows less than 0.4-dB insertion loss, 0.3-dB passband ripple, and better than 12-dB return loss, and the 15-pole filter shows 0.25-dB insertion loss, 0.2-dB passband ripple, and better than 15-dB return loss. Out-of-band rejection for both the filters at 3 MHz below the passband edges is more than 60.0 dB. In order to estimate the power-handling capability of the filters, third-order intermodulation distortion was measured. A sensitivity analysis for the observed frequency shift in the filters is reported, which also shows very similar parametric dependence in both the filters. Also from this analysis, an approach for using the same deign in 0.5% FBW applications is discussed.

Novel compact parallel-coupled microstrip bandpass filters with lumped-element K-inverters

Novel compact parallel-coupled microstrip bandpass filters are proposed by using additional lumped inductors to realize K-inverters between coupled-line sections to achieve an equivalent to the quarter-wavelength (/spl lambda//4) resonator filters. As a result, the filter order can be doubled without increasing the circuit area, and no repeated passband is observed at twice the center frequency. In addition, by introducing the cross-coupling effect, two transmission zeros at upper and lower stopbands may be created. Simple equivalent-circuit models are also established as effective design tools. Specifically, several compact fourth-order microstrip bandpass filters with good stopband rejection are implemented and carefully examined.

Optimized Design Method of Microstrip Parallel-coupled Bandpass Filters with Compensation for Center Frequency Deviation

An optimized design method is presented to compensate for the open-end effect in parallel-coupled microstrip bandpass filters. The analysis of the relationship between center frequency deviation and microstrip open-end effect is given. Based on the theoretical analysis, a design example of 10GHz bandpass filter is presented, which has proved the validity of this method.

Parallel‐coupled microstrip bandpass filters with a wide stopband using spur lines

AbstractIn this paper, we propose a novel parallel‐coupled microstrip bandpass filter with a wide stopband. The proposed bandpass filter with spur lines provides a deep and wide stopband because spur lines can provide deep stopband characteristics in some frequency bands. Also, the experimental results show that the transmission coefficients of the proposed filter are lower than −50 dB around the 2nd‐ and 3rd‐harmonic frequencies. This operation can be obtained without increasing its size while the other features are not degraded. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 9–11, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20359

New formulas for synthesizing microstrip bandpass filters with relatively wide bandwidths

New formulas are proposed for designing wideband parallel-coupled microstrip bandpass filters with improved prediction of bandwidth. When a fractional bandwidth /spl Delta/ is required, a correction /spl theta/=(/spl pi//2)(1/spl plusmn//spl Delta//2) is incorporated into the formulation for determining the dimensions of each coupled stage. Two filters with /spl Delta/=50% are designed and fabricated to show the improvement. The measurement shows a very good agreement with the simulation.

Tapped wiggly-coupled technique applied to microstrip bandpass filters for multi-octave spurious suppression

A tapped wiggly-coupled technique is applied to parallel-coupled microstrip bandpass filters for multi-octave out-of-band spurious suppression. The coupled edges of tapped microstrip resonators are wiggled to equalise the odd-mode and even-mode phase velocities such that the nearest two spurious harmonics can be eliminated. The simulation and experiment show that both the second and the third spurious level are reduced below 42 dB up to 9 GHz for a 2.45 GHz and 5.7% bandwidth bandpass filter.