Microstrip Lowpass Filter Research Articles

Novel microstrip low‐pass filters with fractal defected ground structures

AbstractIn this study, three microstrip low‐pass filters (LPFs) containing fractal‐shaped defected ground structures have been designed and manufactured. To improve the performance of microstrip LPF, cascades of inductively coupled fractal resonators have been applied. Simultaneously, to achieve relatively constant microstrip impedance resulting in essentially low reflection losses, a modification of the strip geometry has been introduced. The measured results excellently prove the validity and efficiency of the proposed new solutions. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2473–2477, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24607

Microstrip Coupled-Line Lowpass Filter with Wide Stopband for RF/Wireless Systems

We present the design of a compact microstrip lowpass filter with a wide stopband which is up to ten times the cutoff frequency. The filter is based on a coupled-line configuration and shunt open stubs. The open stubs create additional transmission zeros, which are used to extend the stopband of the filter without any additional components or cascaded units. A prototype lowpass filter with a 3 dB cutoff frequency of 0.428 GHz and a 15 dB stopband extended up to 4.77 GHz is fabricated to validate the theoretical predictions.

Compact lowpass filters with very sharp transition bands based on open complementary split ring resonators

It is shown that open complementary split ring resonators (OCSRRs) are useful particles for the design of lowpass filters with very narrow transition bands in microstrip technology. Owing to the small electrical size of OCSRRs, the filters are also very small. These filters are implemented by cascading several OCSRR stages in a microstrip line. The OCSRR stages can be modelled as parallel resonators in series configuration, thus providing a transmission zero at their resonance frequency. By designing the OCSRRs with small inductance and high capacitance, very sharp cutoffs are achieved. To illustrate the possibilities of the approach, a prototype device example is provided. It consists on a five-stage periodic microstrip lowpass filter with 3 dB insertion losses at 1.33 GHz and 40 dB rejection at 1.45 GHz. To improve out-of-band rejection, four additional OCSRR stages tuned at the spurious frequency band have been cascaded. Filter dimensions are 39×7.4 mm (i.e. 0.46λ× 0.087λ, where λ is the guided wavelength at the cutoff frequency). These filters are of interest in applications where small size and severe cutoff requirements are required.

Application of the Sensitivity Analysis to the Optimal Design of the Microstrip Low-Pass Filter With Defected Ground Structure

This paper shows applied sensitivity analysis for easier design and practical application of a planar half-wavelength low-pass filter (LPF) using defected ground structure (DGS). Typically, it is difficult to deploy planar half-wavelength low-pass filters when high power durability is required because of the very narrow line-widths of high impedance transmission line. Here, we propose a new configuration for the high impedance microstrip line using DGS structure to allow broader line width and high power handling capability. The sensitivity of the scattering parameters was calculated using the self-adjoint sensitivity formula in order to determine the proposed filter's dimension. The paper also highlights the validity of the proposed LPF optimization with its measured performance.

Compact and selective lowpass filter with very wide stopband using tapered compact microstrip resonant cells

A novel microstrip lowpass filter is proposed. It consists of a simple tapered structure using periodical compact microstrip resonant cells. Owing to the introduction of the tapered structure, the proposed lowpass filter has successfully addressed simultaneously the problems of compactness, matching, selectivity, insertion loss and the suppression of spurious frequency bands. A demonstration filter has been designed, fabricated and tested to show the validity of the proposed structure.

New microstrip low pass filter with transmission zero and wide stopband

AbstractNew microstrip low pass filters with low insertion loss, ultra‐wide stopband and transmission zero are presented by using triangular patch resonator with fractal defection. With such defection and a certain parallel feed method, undesired responses and harmonics are effectively suppressed and wideband, sharp attenuation obtained. The new filter has simpler and more compact configurations even better filter properties than the traditional line based ones. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 830–831, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24138

Compact microstrip lowpass filter with sharp roll-off and wide stop-band

A microstrip lowpass filter with enhanced performance is developed. The studied filter is based on a novel patch resonator that features strong slow-wave effects, and can also implement either an improved roll-off or an enhanced stop-band. A demonstrator filter with 3 dB cutoff frequency fc =2.4=GHz is optimally designed, fabricated and measured. Results indicate that a roll-off of 92.5=dB/GHz together with a relative stop-band bandwidth of 135.5= (referred to a 30=dB suppression) is obtained while achieving a highest figure-of-merit of 10106. Both simulations and measurements are presented and compared.

Wide-Stopband and Miniarurized Lowpass Filters Using Sirs-Loaded Hairpin Resonators

Compact elliptic-function microstrip lowpass filters (LPF) using stepped impedance resonators loaded (SIRs-loaded) hairpin resonators are presented in this paper. By adding a pair of coupled SIRs in a conventional capacitor coupling hairpin LPF, two additional transmission zeros are generated to extend the stopband. In addition to one-cell filter, a filter using two SIRs-loaded resonators was also designed, fabricated, and tested. The two-cell filter has a 3 dB cutoff frequency at 2 GHz and a 10 dB stopband from 2.5 to 25 GHz, with a size of only 0.081λg × 0.096λg.

Method for widening the reject-band in low-pass/band-pass filters by employing coupled C-shaped defected ground structure

Two new compact defected ground structure low-pass filters with broad stop-band and low insertion loss in the pass band are presented. The structures of these new microstrip low-pass filters are simple as they are composed of a pair of DGS-slots and an openstub. One filter is realised through the multi-layer method, and the second filter by cascading. With these configurations, two LPF with compact size, wide reject band and sharp transition from pass to stop-band are realised. The design formulas are derived by using an equivalent circuit model of coupled DGS resonators. Demonstration filters are designed, fabricated and tested. The experimental results show good agreement with theoretical results and demonstrate that the required characteristics of LPF could be simply obtained through the proposed methods. Finally a simple gap-method will be used in order to transform the LPF to BPF.

Novel microstrip lowpass filter using stepped impedance resonator and spurline resonator

AbstractA novel low‐pass filter (LPF) is introduced in this article. The filter consists of a pair of feed lines with spurline resonators and a compact step impedance hairpin resonator. Because of the use of spurline resonators, the LPF exhibits better stopband characteristics and improved ripples performances. The proposed microstrip filter was examined, simulated, and measured. Measurements are given and a good agreement is achieved between simulated and measured results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 196–197, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23993

Modification in microstrip low pass filter using bulb shape patch

This paper presents bulb type semicircular microstrip low pass filter with the sharp rejection and wide stop band. The proposed design is based on the calculation of parameters from traditional high–low impedance method and is available in the literature of microstrip filter. To further improve the design performance, high impedance lines are magnetically coupled, resulting an attenuation pole near −3 dB cut off point of the filter. This design gives insight in designing a low pass filter with reduced size with an arbitrary geographical shape.

Modelling of Microstrip Circuit Using a Hybrid PEEC/FDTD Approach

Currently available electromagnetic analysis methods are showing their limitations when large complex circuit structures, such as modern printed circuit boards and their environments, need to be analyzed. Two methods which may be used for the purpose are the partial element equivalent circuit (PEEC) approach and the finite-difference time-domain (FDTD) method. Each of these has their own advantages and limitations. In this paper, a hybrid method is described which overcomes many of the limitations of PEEC and FDTD while retaining their strengths. Results using the method for low-pass and bandpass microstrip filters are presented.

Design of microstrip bandpass and lowpass filters using coupling matrix method and a new hairpin defected ground structure

AbstractIn this work, we present a novel compact hairpin defected ground structure (DGS) bandpass and lowpass microstrip filter using two hairpin‐slots etched in the ground plane. A compact microstrip BPF using coupled DGS resonators is designed using coupling matrix method. The designed BPF showed very wide stopband with two transmission zeros. Furthermore, a simple technique to transform the designed BPF to a LPF was presented. The BPF was fabricated and measured. The measurement results showed good agreement with the theoretical and simulation results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2898–2901, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23794

Microstrip low‐pass filter using open loop resonators

AbstractA compact open loop resonator microstrip low pass filter is modeled. To optimize the performances of the filter, electromagnetic simulation is used to tune the dimensions of proposed prototype. Cascading of open loop resonator provides a very sharp cut off and wide stop band with minimum insertion loss. The filter is simulated with an equivalent circuit model and it is found to be in good agreement with the structure model response. The structure provides a near ideal response. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2983–2986, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23817

Improvement in Design of Hi-Lo Impedance Microstrip Low-pass Filter

A microstrip low-pass filter with the sharp rejection and wide stop band is presented. The circuit model is developed and analyzed based on traditional hi-lo impedance technique. Achieving the attenuation pole in vicinity of the desired -3dB point, magnetic coupling is added. For improving the design and miniaturization of the circuit, capacitance associated with shunt arm of the 3rd order low pass filter is explored. Comparison of proposed low pass filter has been done with existing filters in respect to effective structure as well as capacitive patch area. The filter design is simulated and dimensions are tuned to meet the desired frequency response. Ill. 7, bibl. 8 (in English; summaries in English, Russian and Lithuanian).

스펙트럴 영역에서 DGS 슬롯 임피던스 특성 해석 및 LPF 응용

In this paper, investigations on the impedance characteristics of a DGS(Defected Ground Structure) slot in the groud plane of microstripline are presented in spectral domain and applied to the characteristic improvement of stepped impedance microstrip low pass filter(LPF). In this method, expressions for the impedance of a DGS slot are derived from self-reaction of the angular spectrum of plane waves and the discontinuity in the modal voltage. The numerical results are compared with those of the rigorous full-wave method and are shown to produce reasonably accurate data. And the stepped impedance microstrip low pass filter is designed and fabricated with the uniform and nonuniform DGS slots for improving the frequency responses. The experiments show that the proposed filter with slots in the ground plane has a wider stopband and sharper cutoff response.

A Novel Approach to Synthesize Microwave Filters using Artificial Neural Networks

Emergence of Artificial Neural Network (ANN) has provided newer avenues in the modeling and design of RF components. This paper proposes a novel synthesis procedure for the design and modeling of microwave filters using ANN. Building a feed forward neural network that corresponds to a Cauer ladder network of a planar filter is the key point of the paper. For validation purposes, the proposed approach has been used to synthesize a microstrip lowpass filter with a cutoff frequency of 1.5 GHz. This example filter design provides an insertion loss of around 2 dB in the pass band and a return loss of around 20 dB at the desired cutoff frequency. The design is verified by fabricating the filter on a glass epoxy substrate (ε = 4.6) with a thickness of 1.6 mm.

Compact quasi-elliptic lowpass filter using symmetric rectangular coupled capacitors

A compact microstrip lowpass filter using symmetric rectangular coupled capacitors is proposed. The introduction of an interdigital structure between the symmetric rectangular capacitors can reduce the filter size, owing to the increase in the loading capacitance, and also can provide the finite attenuation poles, thus quasi-elliptic function and stopband extension are fulfilled. Finally, a demonstration filter is designed, fabricated and tested to show the validity of the proposed lowpass filter structure.

A New Spatial Interpolation Algorithm to Reduce the Matrix Fill Time in the Method of Moments Analysis of Planar Microstrip Structures

A new spatial interpolation scheme is proposed to reduce the matrix fill time in the method of moments implementation of planar microstrip structures. The approach is based on the division of the distance between the basis and the testing functions into three, namely near, intermediate and far regions. The matrix entries in the near region are computed directly. The entries corresponding to both intermediate and far regions are evaluated in two steps: (1) choosing an adequate number of sampling points in these regions and computing the associated entries directly and (2) interpolating the remaining entries by using cubic spline or bicubic spline algorithms. To demonstrate the efficiency and accuracy, the technique is applied to a planar microstrip low-pass filter and a microstrip-line fed patch antenna problems. It is shown that the interpolation scheme can result in significant savings with high accuracy.

Improvement of microstrip low pass filters' characteristics using an optimized number of new multi‐ring defected ground structures

AbstractA novel two square split ring resonators defected ground structure (DGS) is investigated for use in low pass filters (LPF) design. An equivalent circuit and parametric study for the DGS are presented. The DGS is employed in a LPF to obtain very wide reject band. The measured results illustrated the excellent performance. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3074–3078, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22964