Attenuation Poles Research Articles

Microstrip filters based on 2D electromagnetic crystal

Construction of microstrip bandpass filters is suggested on the basis of 2D electromagnetic crystal consisting of P horizontal and K vertical rows of resonators. Adjacent vertical rows of resonators are connected by additional mK-1 resonators arranged above and below the outside 2D crystal. Parametric synthesis of six bandpass filters based on crystals with the dimension of 1×2, 2×2, 2×3, 3×1, 3×2 and 3×3 was conducted with use of electrodynamic numerical analysis of 3D models in studied constructions. While calculating substrates with relative permittivity ε=80, h=1 mm thick were used, in this connection, center frequency of bandwidth was registered as follows - f0≈1.0 GHz, as well as their relative bandwidth Δf/f0≈20%. High frequency-selective properties of the filters are connected not only with the increase of their N order, but also with the presence of amplitude-frequency characteristics of power attenuation poles located near the bandwidth.

A Low-Profile Wide-Bandwidth Planar Inverted-F Antenna Under Dual Resonances: Principle and Design Approach

A low-profile planar inverted-F antenna (PIFA) under the operation of TM0,1/2 and TM2,1/2 modes in a single patch resonator for bandwidth enhancement is proposed. Initially, our study demonstrates that all of the even-order modes can effectively be suppressed by employing a rectangular PIFA instead of the conventional microstrip patch antenna. Then, a pair of shorting pins is appropriately loaded underneath the side-shorted radiating patch to investigate the variation of their odd-mode resonant frequencies. The results indicate that the resonant frequency of TM0,1/2 mode ( $f_{0,1/2}$ ) is dramatically increased up while almost maintaining that of TM2,1/2 mode ( $f_{2,1/2}$ ). After that, the width of the radiating patch is progressively enlarged in order to move the $f_{2,1/2}$ more closely to the $f_{0,1/2}$ . By using this approach, the dual radiative resonant modes can be reallocated in proximity to each other. Additionally, a narrow slot is etched out on the radiating patch so as to counteract the equivalent inductance caused by the shorting pins and probe. As such, a wide-bandwidth with stable radiation pattern is achieved for the PIFA under the operation of these dual-resonant modes. After the extensive analysis is executed, the proposed antenna is fabricated and tested. Simulated and measured results are found in good agreement with each other, demonstrating that its impedance bandwidth is tremendously widened to about 15.3% with appearance of two in-band attenuation poles. In particular, a low-profile property with the height of 0.036 free-space wavelength is achieved.

Millimiter-wave stripline bandpass filters

The possibility to use thin (1 mm or less) pseudocombline structures of λ/2 resonators made of sections of symmetric transmission strip lines from a dielectric material with e r = 2.2 as millimeter-wave bandpass filters is shown. It is established that the relative bandwidth of such filters can reach FBW = 0.1. Designs of stripline pseudocombline filters with alternating signs of the coupling coefficients, which are characterized by improved selectivity due to the attenuation poles located on both sides of the passband, are proposed; the filters contain stepped-impedance “half-wave” resonators with a new feature. The results of the computer simulation of the frequency characteristics of the filters in the frequency band of 31–122 GHz and the comparison of them with the characteristics of other filters are presented.

8-order filter based on 2-D photonic crystal with dual-mode microstrip resonators

The design of 8-order band-pass filter based on 2-D photonic crystal is suggested. Strip conductors in all dual-mode resonators are in the form of «irregular» rectangular frame with a gap and are connected at certain points with the ground. At optimal placement of such resonators on a substrate attenuation pole is observed on the amplitude-frequency characteristic of the filter, near low and high bandwidth slope that significantly improves its frequency-selective properties. The change of gap between input and output resonators allows to control the frequency of these poles.

High-Selectivity single- and dual-resonator microstrip filters

New selective properties are revealed of the base section of conventional microstrip filters with circuits based on a four-wire system of coupled quarter-wave lines with one half-wave hairpin resonator. The conditions under which this single-resonator section acquires the characteristics of multi-resonator circuits due to the possibility of formation of four zeros and six operating attenuation poles at the end frequencies are determined. The structure does not contain elements short-circuited to the screen, which determines its high manufacturability. It is demonstrated that high-selectivity compact microstrip filters can be designed on the basis of single- and dual-resonator structures, i.e., the structures with the minimum number of resonators.

Stripline bandpass filters with alternating coupling coefficients

This article shows the possibility in principle to design stripline comb filters with alternating signs of the coupling coefficients. The new feature of the stepped-impedance resonators of the quarterwave type was established. They provide the opposite sings of the electromagnetic coupling with adjacent resonators. Such resonators are asymmetric relative to the vertical axes, which is drawn through their middle part. The stripline passband filters with alternating signs of coupling coefficients have attenuation poles that are located to the left and to the right of the passband. Those poles improve the selectivity of such filters. The articles provide the measured characteristics of the stripline comb filter of the forth order with alternating coupling, which has the central frequency of f0 = 1835 MHz and the passband width of 90 MHz. The filter is constructed using a dielectric material with relative permittivity of er = 92 and has the dimensions of 7.4×4.2×2 mm.

Planar three-resonator bandpass filters with cross coupling

New designs of planar three-resonator bandpass filters with cross coupling having a large variety of frequency characteristics are considered. In addition to better one-sided selectivity, such filters implement symmetric amplitude–frequency characteristics with an attenuation pole at each side of the passband. These filters can also have constant delay time in the passband. Concatenation of the proposed three-resonator filters leads to multiresonator filters with high selectivity determined by two attenuation poles at each side of the passband. It is found that the type of connection of the middle resonator in the circuit of a three-resonator filter with cross coupling results in substantial differences in amplitude–frequency characteristics. The results of modeling of different frequency characteristics are presented. It is shown that filters have small dimensions, which are comparable to overall dimensions of microwave ceramic filters. For example, dimensions of a three-resonator stripline filter designed for a frequency of 1.9 GHz are 9.4 × 5 × 2 mm for the permittivity of the filter material er = 92 and dimensions of a six-resonator filter are 10 × 9.4 × 2 mm.

Thin stripline bandpass filters for the centimeter band

This article considers the design of thin stripline (1 mm) bandpass filters in the centimeter band, which contain dielectrics with different relative permittivity er. This includes the choice of the resonators, the dielectric material, the preliminary assessment of resonators’ unloaded quality factors and taking into account the features of the frequency response curve of the filter. It was found, that the passband width of the thin comb filters with λ/4 resonators and array-type filters with λ/2 resonators cannot exceed 6% for any values of er and the length of resonators of at least 2 mm. The array-type filters with resonators of half-wave type and with alternating signs of the coupling factors between resonators were proposed. Under certain additional conditions, the attenuation poles appear in such filters, resulting in improved selectivity. The results of computer modelling of the frequency response curve of thin filters of cm band are presented. They are compared to the frequency response of other filters. The data obtained from computer modelling showed good correspondence with the experimental data.

A Compact Broadside Coupled Notched Band UWB Filter with Wide Upper Stopband

ABSTRACTA broadside coupled ultra-wideband (UWB) bandpass filter (BPF) with notched band and wide upper stopband is proposed and implemented. Initially, a broadside coupled UWB filter structure with good passband characteristics is developed. To this, split ring resonator (SRR) metal lines of half guided waveguide length are coupled to generate passband notch. Later, stub lines are embedded in the input and output (I/O) feeding lines whose attenuation poles suppress the spurious harmonics and widen the stopband. Finally, the proposed structure is fabricated and measured which establishes the authenticity of the full-wave electromagnetic response. The passband extends from 2.85 to 11.3 GHz with stopband of width 18 GHz and depth greater than 18 dB. The variation of group delay is less than 0.42 ns in the passband. The proposed structure is small in size measuring 11.08 × 11.7 mm2.

A Novel Differential-Fed Patch Antenna on Stepped-Impedance Resonator With Enhanced Bandwidth Under Dual-Resonance

A novel design concept to enhance the bandwidth of a differential-fed patch antenna using the dual-resonant radiation of a stepped-impedance resonator (SIR) is proposed. The SIR is composed of two distinctive portions: the radiating patch and a pair of open stubs. Initially, based on the transmission line model, the first and second odd-order radiative resonant modes, i.e., TM10 and TM30, of this SIR-typed patch antenna are extensively investigated. It is demonstrated that the frequency ratio between the dual-resonant modes can be fully controlled by the electrical length and the impedance ratios between the open stub and radiating patch. After that, the SIR-typed patch antenna is reshaped with stepped ground plane in order to increase the impedance ratio as highly required for wideband radiation. With this arrangement, these two radiative modes are merged with each other, resulting in a wide impedance bandwidth with a stable radiation pattern under dual-resonant radiation. Finally, the proposed antenna is designed, fabricated, and measured. It is verified in experiment that the impedance bandwidth ( $\vert S_{\mathrm{ dd11}}\vert dB) of the proposed antenna has gained tremendous increment up to 10% (0.85–0.94 GHz) with two attenuation poles. Most importantly, the antenna has achieved a stable gain varying from 7.4 to 8.5 dB within the whole operating band, while keeping low-cross polarization.

Band Notched UWB-BPF Based on Broadside Coupled Microstrip/CPW Transition

ABSTRACTA planar band notched ultra-wideband (UWB) bandpass filter based on broadside coupling of microstrip/co-planar waveguide (CPW) transition is proposed and implemented. The UWB filter topology is made up of microstrip lines on the top coupled in broadside fashion to an open ended CPW in the ground plane. Dual narrow notches at 5.2 and 7.9 GHz are implemented by etching two meander shaped defected ground structures in the CPW under the microstrip lines. A wideband stopband for improved isolation is obtained with the suppression of spurious harmonics by the attenuation poles generated by the spur line structures embedded in the input and output feeding lines. The proposed structure exhibits good frequency characteristics and is of compact size.

Resonator-Based Filters with Frequency Modes Close to Metamaterial Cells

Background . Many of the properties of metamaterials are similar to those found in the filter on mutually detuned frequency and unrelated resonators. The bridge filters are used as a low-frequency prototypes of such microwave filters. It is important to establish an analogy between metamaterials and filters on mutually detuned frequency and unrelated resonators for further development and design of new types of metamaterials. Objective. A central objective is a model development of metamaterials based on band-exclusive microwave filters on mutually detuned resonators, and the low-frequency-based prototypes. Methods. Characteristic equivalence test of metamaterials to microwave filters on mutually detuned resonators, their specific dependencies reveal (the modes in parallel channels, the locations of the attenuation poles above or below the bandwidth), manifested regardless of the types of resonators, the study of the possibility of the bridge filter prototypes using for metamaterials simulation. Results. The analogy between metamaterials and microwave filters on mutually detuned resonator is specified, the possibility of bridge bandpass filter use as low-frequency prototypes is shown. Conclusions . Microwave filters on mutually detuned resonators, and bridge band-pass filters as low-frequency prototypes, design techniques of which are well established, can be used for metamaterial modeling.

A novel type of bandpass filter using complementary open‐ring resonator loaded HMSIW with an electric cross‐coupling

ABSTRACTA novel bandpass filter (BPF) with multiple transmission zeros (TZs) and wide stopband is proposed. The filter is realised using complementary open‐ring resonators (CORRs) loaded half mode substrate integrated waveguide (HMSIW). Besides, a novel electric source‐load electric cross‐coupling configuration is introduced to generate extra attenuation poles at either side of the passband, which improves the passband selectivity and the stopband suppression level. Based on this structure, a BPF operating at 5.8 GHz with multiple transmission zeros is designed and fabricated. The Measurement and simulation results indicate that the proposed configuration is a good candidate for filter design. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:998–1001, 2016

Negative Group Delay Circuit with Improved Signal Attenuation and Multiple Pole Characteristics

This paper presents a design of a transmission line negative group delay (NGD) circuit with multiple pole characteristics. By inserting an additional transmission line into a conventional NGD circuit, the proposed circuit provides further design parameters to obtain wideband group delay (GD) and to help reduce signal attenuation. As a result, the number of gain compensating amplifiers can be reduced, which can contribute to stable operation when integrated into RF systems. The multiple pole characteristics can provide wider NGD bandwidth and can be obtained by connecting resonators with slightly different center frequencies separated by quarter-wavelength transmission lines. For experimental validation, an NGD circuit with two poles GD characteristic is designed, simulated, and measured.

Screen‐Printed Flexible Bandstop Filter on Polyethylene Terephthalate Substrate Based on Ag Nanoparticles

We present a low‐power, cost‐effective, highly reproducible, and disposable bandstop filter by employing high‐throughput screen‐printing technology. We apply large‐scale printing strategies using silver‐nanoparticle‐based ink for the metallization of conductive wires to fabricate a bandstop filter on a polyethylene terephthalate (PET) substrate. The filter exhibits an attenuation pole at 4.35 GHz with excellent in‐and‐out band characteristics. These characteristics reflect a rejection depth that is better than −25 dB with a return loss of −0.75 dB at the normal orientation of the PET substrate. In addition, the filter characteristics are observed at various bending angles (0°, 10°, and 20°) of the PET substrate with an excellent relative standard deviation of less than 0.5%. These results confirm the accuracy, reproducibility, and independence of the resonance frequency. This screen‐printing technology for well‐defined nanostructures is more favorable than other complex photolithographic processes because it overcomes signal losses due to uneven surface distributions and thereby reveals a homogeneous distribution. Moreover, the proposed methodology enables incremental steps in the process of producing highly flexible and cost‐effective printed‐electronic radio devices.

Miniaturized lowpass filter with ultra-wide stopband using dual-plane defected structures

A miniaturized lowpss filter (LPF) with ultra-wide stopband is proposed by using the complementary rectangle split ring defected microstrip structure (CRSR-DMS) and the quad U-shaped defected ground structure (QU-DGS). The presented CRSR-DMS can provide a sharp rejection rate and two obvious attenuation poles while the QU-DGS can produce four independently controlled transmission zeros. Based on the characteristics of the defected structures, the proposed LPF is constructed by using four cascaded CRSR-DMS units and four cascaded QU-DGS units. The measurement result of the designed filter with 3 dB cut-off frequency at 2.0 GHz shows that the obtained 20 dB rejection band ranges from 2.12 GHz to more than 20 GHz within a small circuit area of 0.73λg * 0.13λg, λg being the guided wavelength at 2.12 GHz.

Modelling and validation of a simple and compact wide upper stop band ultra‐wideband bandpass filter

A compact ultra-wideband (UWB) bandpass filter (BPF) is proposed based on end coupled microstrip transmission line, defected ground structure and defected microstrip structure. The experimental filter shows a fractional bandwidth of 110% at a centre frequency, with two observable transmission zeros (attenuation poles) at 2.1 and 11.7 GHz. Measured results exhibit an UWB passband from 3.02 to 10.6 GHz with mid-band insertion loss of 1.8 dB and group delay variation <0.45 ns. The BPF achieves a wide stopband with < −18 dB attenuation up to 20 GHz.

Ultrawide stopband low-pass filter using triangular resonators defected ground

In this article, a novel complementary triangular split ring resonator (CTSRR) using defected ground structure (DGS) is introduced. The unit is implemented in microstrip technology. The CTSRR has unique filter characteristics, including six dimension-dependent finite attenuation poles with wide bandgap, very high attenuation rate, and very low level of passband ripples. CTSRR units with different dimensions CTSRR units are cascaded together to design a high-performance low-pass filter (LPF) with a cutoff frequency (fc) of 1.80 GHz. The designed LPF exhibits an attenuation rate of 250 dB/GHz and passband ripples of less than 0.30 dB. Moreover, it has a wide 20-dB stopband at up to 16.5 times fc. To our knowledge, this is the best obtained stopband value among the published results until now. The designed filter has been fabricated and validated using small signal parameter measurements. Excellent agreement is noticed between transmission coefficient measurements and its simulated counterpart using electromagnetic simulator.

DESIGN OF A COMPACT WILKINSON POWER DIVIDER WITH HIGH ORDER HARMONICS SUPPRESSION

A new method for designing compact Wilkinson power dividers with three order harmonics suppression is presented. The quarter-wavelength transmission line in the traditional Wilkinson power divider is replaced by two pairs of parallel coupled lines with one end connected in series with an open stub. With this structure, the quarter-wavelength line will be shorter and three attenuation poles can be added in the stopband. As a result, this newly proposed structure carries the functions of impedance matching at operating frequency and three orders harmonics suppression. In this study, an example of power divider operating at 1 GHz is designed and fabricated. The measured results show good performance at the operating frequency. In addition, the second, third and fourth harmonics suppressions are 43 dB, 49 dB and 37 dB, respectively, which validates the feasibility of the proposed design.

Design of A Wideband Filter With Attenuation Poles Using A Novel Parallel-Coupled Three-line Unit Based on Cross-Coupling

Design of A Wideband Filter With Attenuation Poles Using A Novel Parallel-Coupled Three-line Unit Based on Cross-Coupling