Synthesis Of Bandpass Filters Research Articles

Calculation of Band-Pass Filters with Fixed Frequencies of Infinite Attenuation

Introduction. When calculating band-pass filters (BPF) with infinite attenuation frequencies using the frequency conversion method, the parameters of the prototype – an inverse or quasi-elliptic low-pass filter (LPF) – are recalculated into BPF parameters according to conventional formulas. Using the selected low-pass filter cutoff frequency and the Q-factor of the band-pass filter, one can select at their discretion only one infinite attenuation frequency (attenuation pole). In order to suppress a pair of concrete frequencies in the attenuation band, the synthesis of BPF should initially fix the frequencies of maximum attenuation and the central frequency of the filter. The reverse transition toward the frequency response parameters of a low-frequency prototype is carried out using frequency conversion formulas.Aim. To develop of a method for calculating band-pass filters with fixed attenuation poles.Materials and methods. Odd-order filters with an additional capacitor in the transverse branch of the П-link and an inductance in the longitudinal branch of the Т-link were used as low-frequency prototypes of the BPF with attenuation poles. Approximation of the frequency response of a low-frequency prototype (inverse or quasi-elliptical LPF) was performed by methods based on solving systems of nonlinear equations.Results. A realizable transfer function (TF) of an n-th order LPF with attenuation poles was written as the ratio of the product of binomials and a polynomial of power n with real coefficients. Systems of equations were derived to determine amplitude-frequency response coefficients with a given frequency of maximum attenuation interference for both types of filters. Analytical expressions for the TF of the low frequency prototypes of 3th and 5th orders were recorded through the capacitances of the BPF circuits tuned to the central and suppressed frequencies, thus allowing the desired capacitances to be directly calculated. The BPF inductances were determined by formulas expressing the dependences of the BPF central frequency on the circuits parameters, taking into account the relationships given in the article. An example of calculating a 10th order quasi-elliptic BPF was provided.Conclusion. The proposed method can be used to determine the BPF parameters directly, without an intermediate calculation and subsequent transformation of the LPF prototype parameters. The given analytical expressions for the frequency response of the П- and Т-shaped BPFs of the 6th and 10th orders make it possible to verify the performed calculations and to correct the frequency response using inductances, when replacing the calculated capacitance values with their standard values.

Automated synthesis of band-pass filters with current to voltage conversion with given transfer gain in the Simone circuit designer

The iterative method for automated synthesis of band-pass filters with current to voltage conversion with a given transfer gain is developed. The structure of the synthesis system of LC circuits with a given voltage transfer coefficient is presented. The implementation of the proposed method in SimOne Circuit Designer plugin is shown. Further ways for method development are suggested.

A Quantitative Approach for Direct Synthesis of Bandpass Filters Composed of Transversal Resonators

This brief aims to propose a quantitative approach for direct synthesis of bandpass filters (BPFs) composed of a few transversal resonators. In conventional synthesis of these BPFs, coupling coefficients between input/output port and resonators are converted to external quality factor ( Qe ), ignoring inherent characteristics of resonators, such as impedance or reactance/susceptance slopes. As a result, the physical dimensions of resonators could only be determined qualitatively. In this brief, a transversal lowpass prototype derived from coupling matrix is transformed into a bandpass circuit at first, then the coupling coefficients between input/output port and resonators in these BPFs are quantitatively derived as an accurate relationship between ${J}$ inverter and susceptance slope of resonators instead. Hence, the physical dimensions of an entire BPF could be directly synthesized by solving the values of ${J}$ inverters and susceptance slope in addition to the resonant frequency of resonators. In order to verify the theory, a proof-of-concept example using cross-shaped resonator is designed and fabricated. The measured results are found in good agreement between the synthesized and simulated ones.

A Filtering Diplexing Antenna for Dual-Band Operation With Similar Radiation Patterns and Low Cross-Polarization Levels

A novel filtering diplexing antenna for dual-band operation is presented. The antenna is composed of a slot-loaded patch and two resonators with a commonly used ground. Dog-bone-shaped slots are used on the ground for achieving broadside magnetic coupling and increasing the isolation between operating bands. The antenna design is based on a second-order Chebyshev bandpass filter synthesis. The proposed antenna exhibits high band-edge selectivity performance, low cross-polarization levels with half-power beamwidths greater than 86° for 2.4- and 5.2-GHz WLAN communication bands. The measured and simulated results are highly consistent.

Waveguide bandpass filter on complex resonance diaphragms

Results of electrodynamic analysis of single resonance diaphragms in the form of a rectangle window with two L-shaped combs in a rectangle waveguide and results of synthesis of bandpass filters on their basis are presented. The electromagnetic fields and critical wavenumbers of a rectangle wavegide with two L-shaped combs that form the aperture of the diaphragms are determined by the partial domain method with allowance for the field singularity on the edge. The proposed diaphragm aperture allows one not only to obtain resonator Q-factors that are higher than those of usual rectangle windows but also to obtain record low attenuation levels for this type of filters in the stop band owing to the presence of an antiresonance in the aperture’s transient characteristic.

Synthesis design of UWB bandpass filter using multiple resonance resonator (MRR)

An ultra-wideband (UWB) bandpass filter synthesis and design, using a multiple resonance resonator (MRR), is presented. Mixed-mode coupling is used to introduce a finite transmission zero to increase the filter selectivity. The equivalent circuit of the design is used to find the filtering function using even–odd mode analysis. The synthesis procedure is done on an extracted filtering function in order to realise the quasi-Chebyshev filtering response. Finally, a compact filter prototype has been fabricated to validate the synthesis theory and simulated design. The measured and simulated results show good agreement.

Compact filtering antenna using CRLH resonator and defected ground structure

A compact filtering antenna with high band-edge gain selectivity using a composite right-/left-handed (CRLH) resonator and a defected ground structure is presented. The CRLH resonator resonates at the zeroth-order mode and acts as the first stage of the corresponding filter; an octagonal patch acts as a radiator as well as the last stage of the filter. The design procedure follows the circuit approach - synthesis of bandpass filters. The filtering antenna has two poles in the passband and two radiation nulls (zeros) at the band edges. Compared to the conventional patch antenna, the proposed filtering antenna, with little extra circuit area, has flat gain response within the passband, good selectivity at the passband edge and wider bandwidth. Measurement results show that the filtering antenna can operate at 5.29 GHz, has a 430 MHz bandwidth and a 2.5 dBi antenna gain in the broadside (+ Z ) direction within the passband.

Bandpass Filters Based on L-ridged Rectangular Waveguides

We solve the problem of electrodynamic analysis and synthesis of bandpass filters based on rectangular waveguides with complex L-shaped ridges. Cutoff wave numbers and components of the electromagnetic field were calculated by the partial region method with allowance for the singularity of the electromagnetic field on metal ribs. As a prototype, the model of a cutoff filter and an approximation of its amplitude-frequency characteristic by the Chebyshev polynomials were used. Examples of synthesis of narrow-band filters with inputs based on a rectangular waveguide and an H-waveguide are presented. Advantages of using a novel waveguide with a complex cross section in the filter are considered, including the appearance of a total reflection frequency (antiresonance) in the filter rejection band, which allows one to significantly extend this band and increase the attenuation level in it.

A Codesigned Compact Dual-Band Filtering Antenna with PIN Loaded for WLAN Applications

A codesigned compact dual-band filtering antenna incorporating a PIN diode for 2.45/5.2 GHz wireless local area network (WLAN) applications is proposed in this paper. The integrated filtering antenna system consists of a simple monopole radiator, a microstrip dual-band band-pass filter, and a PIN diode. The performance of the filtering antenna is notably promoted by optimizing the impedance between the antenna and the band-pass filter, with good selectivity and out-of-band rejection. The design process follows the approach of the synthesis of band-pass filter. In addition, the PIN diode is incorporated in the filtering antenna for further size reduction, which also widens the coverage of the bandwidth by about 230% for 2.4 GHz WLAN. With the presence of small size and good filtering performances, the proposed filtering antenna is a good candidate for the wireless communication systems. Prototypes of the proposed filtering antenna incorporating a PIN diode are fabricated and measured. The measured results including return losses and radiation patterns are presented.

Low‐cost microstrip filter antenna with a monopole‐like radiation pattern for RF front end

AbstractA low‐cost microstrip filter antenna with a monopole‐like radiation pattern suitable to be embedded inside a RF front end of wireless communication systems is presented. The filter antenna comprises two square open‐loop resonators, a coupled line, and a microstrip antenna with an impedance transformation line. The microstrip antenna is excited by the coupled line, which is treated as the admittance inverter in filter design. The microstrip antenna performs as not only a radiator but also the last resonator of the bandpass filter. Therefore, the transmission loss between the filter and the antenna is reduced. The patch of the microstrip antenna is stacked above the system circuit board of the RF front end. In this case, the design can fully integrate the circuit board of the RF front end into an internal filter‐antenna solution. The design procedure of the filter antenna follows the circuit approach—synthesis of bandpass filters. The measured results show good agreement with the simulated ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1810–1814, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26932

Applications of Open Split Ring Resonators and Open Complementary Split Ring Resonators to the Synthesis of Artificial Transmission Lines and Microwave Passive Components

This paper is focused on the application of open split ring resonators (OSRRs) and their dual counterparts, open complementary split ring resonators (OCSRRs), to the synthesis of composite right/left-handed transmission lines, that is, artificial lines exhibiting backward wave propagation at low frequencies and forward wave propagation at high frequencies. Due to the small dimensions of these resonators, the resulting lines are very compact. Several artificial lines, with different electrical characteristics and topologies, are reported as illustrative examples. It is shown that these artificial lines can be applied to the synthesis of dual-band components and bandpass filters, and two prototype device examples are designed and fabricated in coplanar waveguide technology: a dual-band impedance inverter applied to a dual-band power divider, and an order-3 wide-band bandpass filter. Finally, it is also demonstrated that OSRRs and OCSRRs can be combined for the synthesis of band pass filters in microstrip technology. Since OSRRs and OCSRRs are described by means of series and shunt resonant tanks, respectively, and they are electrically small, their potential to the design of semi lumped planar microwave devices is very high.

Synthesis of bandpass filters designed on the basis of 1D PBG structures

A technique for the synthesis of bandpass filters designed on the basis of 1D periodic structures with resonant defects is proposed. Conditions under which the filter’s frequency characteristic approaches a Chebyshev characteristic or a maximally flat characteristic are formulated. The synthesis problem is reduced to solution of a system of nonlinear equations. Numerical results are obtained for the particular case of a periodic structure composed of dielectric layers.

Direct derivation and refinement of generalized Cohn-Matthaei formulas for resonator coupling coefficients in a microwave filter

Generalized formulas for direct synthesis of bandpass filters are presented. The formulas are derived on the basis of a lowpass prototype filter formed from lumped reactive elements and on the definitions of the coupling coefficient and the quality factor of the filter resonators. In deriving the formulas, neither the equivalent circuits with impedance inverters nor linear approximations of the frequency dependences of the immitances of reactive elements are used. The frequency characteristics of a simple filter that is formed by a cascade connection of alternating low-impedance and high-impedance half-wavelength sections and is synthesized using both the approximate and refined formulas are compared.

Insertion Loss Synthesis of Band-Pass Filters with Equal Terminations

While illustrating insertion loss synthesis with equal terminations, textbooks usually cite the example of a low-pass filter with all transmission zeros at infinity, or that of a high-pass filter with all transmission zeros at the origin. The problem that arises in realizing an equally terminated band-pass filter, with transmission zeros at infinity as well as at the origin, has been highlighted in this paper, along with its solution.

Design E-Plane Bandpass Filter Based on EM-ANN Model

A novel design method has been developed for E-plane bandpass filter synthesis based on an electromagnetic artificial neural network (EM-ANN) model. EM-software analysis is employed to characterize an E-plane strip. The EM-ANN model is then designed by exchanging the EM-software input/output. The filter is designed without finding the physical parameters by solving equation. A W-band E-plane bandpass filter is designed by this method, the insertion loss of which is less than 1.5 dB, and the center frequency is 94 GHz with a bandwidth of 4 GHz.

On the synthesis of bandpass filters with bridged topology

This paper presents a general design theory for bridged topology filters exhibiting a Chebyshev characteristic within any wide passband and an arbitrary out-of-band response. The networks proposed consist of LC grounded resonators capacitively coupled to each other. All the inductances have the same value and also negative couplings may be realized by using 1:-1 transformers. One of the most interesting applications is the design of an FDM channel filter working in the 24-28-kHz range. Some experimental results are described.

Computer-aided optimal synthesis of bandpass filters : Daae, H.IEEE trans. vol CAS-22 no 6 (June 1975) pp 490–495

Computer-aided optimal synthesis of bandpass filters : Daae, H.IEEE trans. vol CAS-22 no 6 (June 1975) pp 490–495

Computer-aided optimal synthesis of bandpass filters

A method is developed for the computer-aided synthesis of a particular case of linear, lumped, passive, bilateral, lossless bandpass ladder filters. It involves the numerical values of the open-circuit immittance functions in three sets of equations referred to as the terminal, the remainder, and the junction algorithms. The filter model comprises two chains of LC sections, each of which contains one arbitrary component value and a finite frequency rejection circuit. The response of this model is exact, save for roundoff errors. The possibility of placing boundary values on all component values is then investigated through a systematic permutation of all finite frequency rejection circuits and by varying all arbitrary component values in a programmable number of steps. The process is applied to the example case design of a 70-MHz 14th-order filter.

A Numerical Fourier Transform Technique and Its Application to Acoustic-Surface-Wave Bandpass Filter Synthesis and Design

A Numerical Fourier Transform Technique and Its Application to Acoustic-Surface-Wave Bandpass Filter Synthesis and Design

A versatile active RC building block with inherent compensation for the finite bandwidth of the amplifier

An earlier paper by the authors describes an easily trimmed universal building block for active RC filters which possesses the valuable characteristic that, with suitable design, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -value can be made approximately independent of the gain-bandwidth product of the operational amplifiers. This makes the filter usable for high frequencies, while at the same time the dependence of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -value on temperature variations in the operational amplifiers is drastically reduced. Design formulas are presented, as well as comparative measurements which verify the theory. The building block is shown to have excellent characteristics both as a universal second-order building block and as a standard block for active ladder synthesis of bandpass filters.