Parallel Coupled-line Bandpass Filter Research Articles

Design of Microstrip Low-pass and Band-pass Filters using Artificial Neural Networks

Usually the design of microstrip filters is done using simulators and classical approximation methods as Butterworth and Chebyshev, these techniques takes a lot of time to run for designing filters. In this paper we develop a faster artificial neural network model for designing a microstrip low-pass and band-pass filters for all rang of operating frequency , when the input are the dimensions of filter, operating frequency, the features of substrate, and the output are the transmission and reflection coefficients. The database uses for training this model is generated by a linear simulator based on circuits model. Two filters designed by the developed model are a stepped impedance low-pass filter with a cut-off frequency of 1 GHz and a parallel coupled-line band-pass filter with fractional bandwidth of 25 % and a central frequency of 2.45 GHz. The results of simulation are compared with desired results and the effectiveness of this method has been proven.

Spurious harmonic suppression in compact coupled-line bandpass filter with asymmetric perturbations

ABSTRACTPresent article exhibits the design of a third-order compact parallel-coupled line bandpass filter at 5.25 GHz having asymmetric perturbations to suppress the second harmonic. Initially, the effects of compactness on filter characteristics have been studied by synthesising the distributed filter network into its equivalent circuit model. The design has been initiated by computing the unit cell model, which leads to the first-order and third-order design instances with an improvement in compactness over the traditional parallel-coupled line filter. In contrary, compactness in the filter characteristics degrades the second harmonic level subject to enhanced imbalances among the odd- and even-mode velocities at the coupled lines. Subsequently, the improvement in the harmonic suppression of 53 dB and 58 dB has been achieved by incorporating different non-uniform perturbations to the outer and coupled edges of the compact filters. Accordingly, compactness of 58% and 71% have been obtained subject to the folded and in-line designs over the conventional layout.

Compact Band-Pass Filters Based on Parallel-Coupled Lines with Open Stubs

In this paper, two parallel coupled line band-pass filters are proposed. The proposed parallel coupled line band-pass filters are composed of the parallel coupled lines and open stubs. The equivalent circuit of the proposed parallel coupled line band-pass filter is proposed and analyzed. By using odd–even mode analytical method, the design equations are derived. The relation between the center resonant frequency of the proposed band-pass filters and the electrical length is analyzed. The relation between the fractional bandwidth and the impedances is discussed. Two proposed parallel coupled line band-pass filters are designed, fabricated and measured based on the calculated results. The spurious frequencies of the proposed filters are suppressed and the transmission zeros improve the filters’ selectivity. The measured results and the simulated results show good agreement with each other, which verifies the design theory.

Unequal termination impedance parallel-coupled lines band-pass filter with arbitrary image impedance

This paper presents an analytical design for a microstrip parallel-coupled line bandpass filter (BPF) with arbitrary termination and image impedances. Using the proposed design formulas, multistage arbitrary termination impedance BPFs can be designed with a very high impedance transforming ratio (r). The fractional bandwidth and return losses are maintained even though the r and image impedance are varied. To validate the design formulas, two- and three-stage BPFs are fabricated and measure at the center frequency (f0) of 2.6 GHz. The filter 1 and filter 2 are designed with termination impedances of 50–300 Ω and 20–50 Ω, respectively. The measured results of both filters show a good agreement with the simulations. The measured passband insertion and return losses of filter 1 are better than 0.8 and 19.6 dB, respectively. Similarly, the measured passband insertion and return losses of filter 2 are better than 1.5 and 19 dB, respectively.

Design of a compact symmetricalc-Band Micro Strip Band Pass Filter with Periodic Saw tooth Grooves

Design of a miniaturized symmetrical band pass filter (BPF) using parallel-coupled half-wavelength micro strip resonators with improved stop band characteristics and 2nd harmonic suppression is presented. The proposed filter is designed at a center frequency of 5.25 GHz with a stop band insertion loss greater than-10dB at 5.15 GHz and fractional bandwidth of 20% (4.74–5.80GHz). The conventional parallel-coupled line band pass filter structure has been folded symmetrically about the horizontal plane and consecutive saw tooth periodic grooves are introduced to the parallel lines. Thus there has been a significant improvement in 2ndharmonic suppression to almost-34.51dB. Size reduction of 46.73% is accomplished with respect to the conventional filter.

Synthesis of Wideband Parallel-Coupled Line Bandpass Filters With Non-Equiripple Responses

This letter proposes a synthesis of wideband parallel-coupled line bandpass filters with controllable non-equiripple frequency responses. Different from the traditional Chebyshev transfer function filters, the reflection lobes of the proposed non-equiripple filters can be redistributed within the operating passband. As a result, the proposed filters have a reduced sensitivity to manufacturing errors and exhibit good tolerance control for maximum in-band reflection loss. By deriving the transfer functions, a synthesis approach with a set of nonlinear equations can be established according to the specifications such as the bandwidth and predetermined reflection lobes. Without performing any post optimization in the full-wave simulation, the non-equiripple synthesized results have less sensitivity in comparison with those obtained from traditional Chebyshev transfer functions with equiripple frequency responses.

Compact parallel-coupled line bandpass filter using double complementary split ring resonators

A novel compact parallel-coupled line bandpass filter (BPF) with complementary split ring resonators (CSRRs) is presented in this letter.The proposed BPF, with a combination of CSRRs and parallel-coupled lines, has the advantages of compact size and simpler design procedure compared with conventional CRSS BPFs. The prototype filter achieves the measured insertion loss of 1.4 dB at 3.6 GHz. The implementing area is 0.35 λg × 0.14 λg, where λg is the guided wavelength at the resonant frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:506–509, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27373

Improved Microstrip Filters Using PMC Packaging by Lid of Nails

This paper shows that microstrip filters perform like textbook examples when packaged with perfect magnetic conductor (PMC). A PMC is made as a pin surface or lid of nails, and this is used to package a microstrip parallel coupled line bandpass filter. Our measurements confirm that parallel plate, cavity modes, and radiation are suppressed. This paper also includes a study of the reasons for a frequency shift between the ideal PMC packaged case and the realized case.

Unequal Wilkinson Power Dividers With Favorable Selectivity and High-Isolation Using Coupled-Line Filter Transformers

In the conventional unequal-split Wilkinson power divider, poor selectivity for each transmission path is usually a problem. To surmount this obstacle, the parallel coupled-line bandpass filter structure is utilized as an impedance transformer as well as a band selector for each transmission path in the proposed unequal-split Wilkinson power dividers. However, the bandpass filters in the proposed dividers require careful design because they may not be functional under certain conditions. For example, the odd-order coupled-line filters are not appropriate for impedance transformers in the proposed unequal-split dividers and high-isolation requirement. Using the even-order coupled-line filter transformers, this study proposes two types of unequal-split Wilkinson power dividers. The first type of the proposed dividers arranges two filter transformers near two output ports, respectively, and is capable of achieving a highly remarkable isolation between the two output ports and a good band selection in each transmission path. Specifically, not only the operating band but also the lower and higher stopbands can achieve highly favorable isolation for this type of divider. By arranging the load impedance of each port properly, the second type of the proposed dividers, which has only one filter transformer to be shared by each transmission path near the input port, is also proposed to provide effective isolation between two output ports and favorable selectivity in each transmission path.

Parallel-coupled line filter design from an energetic coupling approach

In this study, the design of parallel-coupled line bandpass filters (BPFs) is investigated from an energetic coupling theory approach. The proposed filter design process allows the design of BPFs with improved characteristics. In particular, it is possible to implement filters with reduced occupation area, larger passband bandwidth and improved rejection performance. This is accomplished by controlling the coupling coefficient between resonators by means of the coupling section length. The suggested design technique is validated through the design, fabrication and measurement of several coupled line microstrip BPFs centred at 2.0 GHz.

Improving the stopband of microstrip parallel-coupled line bandpass filters using partially coupled resonators

An effective method is introduced to improve the stopband performance of microstrip parallel-coupled line bandpass filters. The proposed filter is constructed by adding several partially coupled resonators close to each trace in the conventional microstrip parallel-coupled line bandpass filter. The lengths of the coupled section and the stub section in each partially coupled resonator are selected such that the desired transmission zero is obtained. Proper selection of the number and the frequency of each transmission zero eventually makes it possible to suppress the unwanted spurious responses. In order to demonstrate the characteristics of the proposed filter, a third-order bandpass filter, which is centred at the operating frequency of 1 GHz with 10% fractional bandwidth, is designed, tuned, fabricated and tested. Measurement and simulation results show that the proposed prototype has a broad upper stopband performance, whereas it keeps the desired passband loss and shape almost equal to that of the conventional ones.

Characterization and dielectric behavior of B 2O 3-doped 0.9Mg 0.95Co 0.05TiO 3–0.1Ca 0.6La 0.8/3TiO 3 ceramic system at microwave frequency

The microwave dielectric properties and the microstructures of (1 − x)Mg 0.95Co 0.05TiO 3– xCa 0.6La 0.8/3TiO 3 ceramic system, prepared by a mixed oxide route, have been investigated. The sintered 0.9Mg 0.95Co 0.05TiO 3–0.1Ca 0.6La 0.8/3TiO 3 ceramics with B 2O 3 addition were characterized using X-ray diffraction spectra and scanning electron microscopy (SEM). The microwave dielectric properties are found to strongly correlate with the sintering temperature as well as the amount of B 2O 3 addition. The Q × f value of 0.9Mg 0.95Co 0.05TiO 3–0.1Ca 0.6La 0.8/3TiO 3 ceramic increased with increasing temperature to 1225 °C/4 h and decreased thereafter. The decrease in Q × f value was coincident with the abnormal grain growth. A maximum Q × f value of 76,000 GHz associated with an dielectric constant ( ɛ r ) of 22.67 and a temperature coefficient ( τ f ) of −12 ppm/°C, was achieved for samples with 0.5 wt.% B 2O 3 additions sintering at 1225 °C/4 h. By appropriately adjusting the x value in the (1 − x)Mg 0.95Co 0.05TiO 3– xCa 0.6La 0.8/3TiO 3 ceramic system, zero τ f value can be obtained. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance.

Compact quasi-elliptic microstrip bandpass filter using terminated anti-parallel coupled-line

A compact quasi-elliptic microstrip bandpass filter with lower and upper stopband zeros is presented. The bandpass filter consists of terminated anti-parallel coupled-line and the stopband zero is generated and controlled by the reactive termination. In comparison to the traditional parallel coupled-line bandpass filter, the proposed filter achieves simultaneous size reduction and sharp filter skirt. The usefulness of the proposed filter is validated by a simultaneously miniature and selective quasi-elliptic bandpass filter centred at 2.4 GHz with 4.6% fractional bandwidth as well as two transmission zeros at 2 and 3.2 GHz.

Parallel coupled-line bandpass filter with branch-line shape for G-band frequency

A parallel coupled-line planar bandpass filter (BPF) with branch-line shape using coplanar waveguide technology on GaAs substrate is presented. The unit parallel coupled-line BPF utilises a parallel coupled-line resonator with an open-ended stub which has suppression response of spurious band. Four unit parallel coupled-line BPFs are integrated with branch-line shape and open-circuit stubs on input and output ports are also integrated for improvement of rejection performance. The proposed fourth-order filter was fabricated on GaAs substrate with dielectric thickness of 50 m and gold thickness of 1.2 mum. The fabricated fourth-order BPF shows a 3 dB bandwidth from 177 to 209 GHz frequency range with insertion loss of 6.5 dB, rejection of 38 dB and return loss better than 12 dB. It has a high resolution fractional bandwidth of 17%.

New dielectric material system of La(Mg 1/2Ti 1/2)O 3–Ca 0.6La 0.8/3TiO 3 for microwave applications

The microstructure and microwave dielectric properties of xLa(Mg 1/2Ti 1/2)O 3–(1 − x)Ca 0.6La 0.8/3TiO 3 ceramics system with ZnO additions (0.5 wt.%) investigated by the conventional solid-state route have been studied. Doping with ZnO (0.5 wt.%) can effectively promote the densification and the dielectric properties of xLa(Mg 1/2Ti 1/2)O 3–(1 − x)Ca 0.6La 0.8/3TiO 3 ceramics. 0.6La(Mg 1/2Ti 1/2)O 3–0.4Ca 0.6La 0.8/3TiO 3 ceramics with 0.5 wt.% ZnO addition possess a dielectric constant ( ɛ r ) of 43.6, a Q × f value of 48,000 (at 8 GHz) and a temperature coefficient of resonant frequency ( τ f ) of −1 ppm/°C sintering at 1475 °C. As the content of La(Mg 1/2Ti 1/2)O 3 increases, the highest Q × f value of 62,900 (GHz) for x = 0.8 is achieved at the sintering temperature 1475 °C. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance.

Dielectric properties and applications of low loss (1−x)(Mg0.95Co0.05)TiO3–xCa0.8Sm0.4/3TiO3 ceramic system at microwave frequency

In this paper, the microstructures and microwave dielectric properties of the (1 − x )(Mg 0.95 Co 0.05 )TiO 3 – x Ca 0.8 Sm 0.4/3 TiO 3 ( x = 0.05–0.2) ceramic system were investigated. Ca 0.61 Sm 0.78/3 TiO 3 increased the dielectric constant ( ɛ r ), reduced the quality factor ( Q × f value) and also compensated the temperature coefficient of resonant frequency ( τ f ) of (Mg 0.95 Co 0.05 )TiO 3 . The microstructures of (1 − x )(Mg 0.95 Co 0.05 )TiO 3 – x Ca 0.8 Sm 0.4/3 TiO 3 ceramics were characterized by X-ray diffraction patterns, scanning electron microscope (SEM). The existing areas of different compositions in the ceramics were observed by means of energy dispersive spectroscopy (EDS), which revealed that Ca 0.8 Sm 0.4/3 TiO 3 as minor phase co-existed with (Mg 0.95 Co 0.05 )TiO 3 . The existing Ca 0.8 Sm 0.4/3 TiO 3 phase can inhibit the grain growth of the main (Mg 0.95 Co 0.05 )TiO 3 phase. A dielectric constant ( ɛ r ) of 22.5, a Q × f value of 108,000 (at 8 GHz ) and a τ f value of −8 ppm/°C were obtained for 0.9(Mg 0.95 Co 0.05 )TiO 3 –0.1Ca 0.8 Sm 0.4/3 TiO 3 ceramic sintered at 1275 °C for 4 h. Moreover, an ISM band parallel-coupled line band-pass filter with a central frequency of 5.8 GHz was also designed and fabricated using the proposed material as substrate to study its performance. It also showed a substantial reduction in both insertion loss and size in comparison with other dielectrics FR4 and alumina.

π-형 전송선 급전 구조를 갖는 대역 통과 필터

This paper proposed the band pass filter(BPF) with feeding structure using -type transmission line by means of transforming the input/output coupled-lines of the half wavelength parallel coupled-line BPF into K-inverter, then substituting -type transmission line equivalence for K-inverter. The proposed method supplies solution with what the half wavelength parallel coupled-line BPF`s input/output coupled-lines are realized. Also it can quite reduce efforts and time needed to optimize filter performance when is compared to reported method using tapped line structure because formulas is very simple and accurate. On the basic of the proposed method, the BPF with feeding structure using -type transmission line has been designed and fabricated. The validity of proposed method was proven by the measured result.

Corrugated parallel-coupled line bandpass filters with multispurious suppression

Corrugated coupled stages are devised to design bandpass filters with multispurious suppression. Through two-port analysis, the suppression is found critically dependent on equality of the even and odd mode phase velocities at even harmonics of design frequency fo. Quarter-wave (λ/4) corrugated stages are tuned to allocate inherent transmission zeros at both 2fo and 4fo, and 6fo for some structures, so that the circuit is free of spurious at these frequencies. Coupled stages with proper coupling lengths are arranged to cancel unwanted peaks at 3fo, 6fo and 7fo, and tapped input/output scheme is employed to tackle those at 3fo and 5fo. Measured data of designed filters show rejection levels better than 30 dB in upper stopband. Three circuits are fabricated and measured to demonstrate the idea.

Optimum design of microstrip parallel coupled-line band-pass filters for multi-spurious pass-band suppression

A modified configuration for the parallel coupled-line band-pass filters is presented which allows it to largely suppress the spurious pass-bands. The proposed filter configuration is composed of two attached open-circuit stubs at the open-end of each section of the conventional coupled-line filter. A least-square-based algorithm is developed for the design and optimisation of the proposed filter. First, the two-port impedance matrix of a coupled line is determined from its four-port matrix. Then, the transmission matrix of a coupled line and subsequently that of the multi-section filter are obtained, which lead to its scattering parameters. Finally, an error function is constructed by the specified insertion and return losses of the filter. To demonstrate the characteristics of the proposed filter, a third-order band-pass filter centred at the operating frequency of 1.7 GHz with 5% fractional bandwidth is designed, optimised, fabricated and tested. Simulated and measured data show that for such a filter prototype, a rejection level exceeding 20 dB is obtained in the first four spurious pass-bands, while keeping the desired pass-band attenuation less than 2 dB. In addition, the filter circuitry size is reduced in comparison with the conventional parallel coupled-line filters, and an impedance matching function is also embedded in the filter configuration.

A PARALLEL COUPLED-LINE FILTER USING VLSI BACKEND INTERCONNECT WITH HIGH RESISTIVITY SUBSTRATE

This paper reports our progress in developing parallel coupled-line filters based on Si-based VLSI backend interconnects for millimeter-wave applications. The resonant frequency of this coupled-line filter increases with increasing spacing-gap and with increasing IDM thickness. By using high resistivity substrate, the parallel coupled-line band-pass filter is extremely effective in reducing substrate loss, and also provides very low insertion loss, even at the millimeter-wave regime. In addition, the parallel coupled-line filter suitable for advanced system-on-a-chips at the millimeter wave application achieves high performance characteristics, which show low insertion loss, wide band, and compatibility with standard VLSI process.