Fractal Bandpass Filter Research Articles

Reconfigured compact Minkowski fractal microstrip filter

AbstractA rapid growth in 4G and 5G in wireless communication applications demand compact and reconfigurable microstrip filters structures. However, meeting these requirements comes with many challenges, namely the increased design complexity, system size, fabrication process, and cost‐effectiveness. Accordingly, the paper aims to design a reconfigurable microstrip filter in terms of its geometrical structures of compactness and its operational performances. A reconfigured compact parallel‐coupled microstrip bandpass filter is a modified Minkowski fractal geometrical shape of inverted alphabet C structure and the first iteration of Minkowski is proposed. The proposed work shows the design technique, parametric analysis, and simulated results of a compact parallel‐coupled microstrip Minkowski fractal bandpass filter for dielectric constant 4.4 and thickness 0.8 mm, operating at 5.1 GHz and bandwidth of 1.5 GHz. A good agreement between simulated results and designed values is achieved, the filter is compact with good bandwidth, less loss, and is dedicated to wireless communication applications.

Novel Dual-Mode Microstrip Triangular Patch Resonator Bandpass Filter

Some new characteristics of microstrip equilateral triangular patch resonator with fractal defection are analyzed, and novel fractal bandpass filters using equilateral triangular resonator are presented to implement high performances of multi-transmission zeros, wide passband and stopband, and low passband insertion loss as well as miniaturization. Due to the space-filling property of fractal geometry, this structure can adjust the location of the transmission zero, it also effectively control the filter’s size. The proposed filters have compact and simple structures, small sizes, high selectivity and so on, and all these features are the requirement of wireless communication circuits. By adjusting filters parameter, we get the optimized S‑parameters. The resonant frequency shifts to lower frequency locations by increasing hemline length c. Measured results of the filter using three fractal-shaped structures are in good agreement with the simulated ones.

New Compact Microstrip Filters Based on Quasi Fractal Resonator

This paper presents new microstrip devices as single band bandpass and multi band bandstop filters. The proposed filters use slotted patch microstrip resonator based on quasi fractal geometry, simulated by AWR12 software package. Both filters have quasi elliptic frequency response, designed at centre frequency of 2.437 GHz for bandpass filter and at band frequencies of 2.434, 4.032, 4.976 and 5.638 GHz GHz respectively, for multi bandstop filter. All filters are employed using RT/Duroid 6010.8 LM substrate of dielectric constant and 1.27 mm dielectric thickness. Simulation results show that the designed quasi fractal bandpass filter has very narrow fractional bandwidth of 0.38 % which is very rare in microstrip filter design. On the other hand, the projected bandstop filter offers multi narrow rejection bands that is useful in broadband wireless schemes influencing from fixed interferences. Both filters present satisfactory S11 and S21 responses besides smallness properties that stand for interesting features of the newest wireless applications. The simulated and measured frequency responses for both designed filters are in good agreement.

Microwave Fractal Bandpass Filters Based on Modified Hilbert Curves of the First and the Second Orders

The microwave fractal bandpass filters based on modified Hilbert shaped curves of the first and second fractal orders are experimentally and numerically analyzed. As a substrate Al2O3 ceramic covered by the thin silver layer with thickness of 50 μm was used. The laser patterning technique was used to design the structures of filters. The filter based on the Hilbert curve of the first order has resonance at ∼4.01 GHz, while the filter based on the second order Hilbert curve has resonances at ∼3.09 and ∼6.34 GHz. The estimated loaded Q-factor of the filter based on the first order Hilbert curve was ∼94. The electromagnetic field distribution of the filter was visualized by using the thermo-elastic optical indicator microscopy.

Fractal Bandpass Filter Using Y-shaped Dual-Mode Resonator for C-Band Receiver (Research Note)

In this study, a fractal, Y-shaped dual-mode resonator bandpass filter (BPF) with input-output cross-coupling is introduced. A parallel-coupling feed structure with a cross coupling has been used to generate two transmission zeroes (TZs) near the lower and upper cutoff frequency that can effectively improve the passband edge selectivity. Also, a fractal shaped based on conventional diamond and square is located. Current density and equivalent model is also given depending on the odd/even excitation resonance condition. The demonstrated filter with a compact size of 0.5*18.3mm2 exhibits a fractal bandwidth of 67% centred as 6GHz(f0) within the 4 to 8GHz bandwidth and minimum insertion loss of 0.3 dB, maximum return loss of 13,15.7dB and flat group delay around 0.3ns that is candidate for use in commercial communications satellites(C-Band).

Miniaturised microstrip bandpass filters based on Moore fractal geometry

This paper presents new microstrip bandpass filter design topologies that consist of dual edge-coupled resonators constructed in the form of Moore fractal geometries of second and third iteration levels. The space-filling property for proposed fractal filters has found to produce reduced size shapes in accordance with sequential iteration levels. These filters have been prepared for ISM band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 10.8, dielectric thickness of 1.27 mm and metallisation thickness of 35 µm. The output responses of each fractal bandpass filter have been determined by a full-wave-based electromagnetic simulator Sonnet software package. Simulated and experimental results are approximately compatible with each other. These responses clarify that these fractal filters have good transmission and return loss characteristics with blocked higher harmonics in out-of-band regions.

A novel wideband microstrip fractal bandpass filter with a notch band at 5–6 GHz

AbstractThis article presents a novel wideband Sierpinski fractal stub‐based microstrip filter that provides a notch band at 5–6 GHz. The frequency bandwidth is 103% from 2.89 to 9.0 GHz, which has two passbands of 40 and 25% separated by the notch band. The filter has been designed using full wave analysis tools and has been experimentally verified. The simulated and measured results are found to be in acceptable agreement. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1413–1416, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25194

NOVEL MICROSTRIP TRIANGULAR RESONATOR BANDPASS FILTER WITH TRANSMISSION ZEROS AND WIDE BANDS USING FRACTAL-SHAPED DEFECTION

Fractal microwave passive circuits are simple and novel structures that attract much attention recently, however, the fractal technique is dominantly applied in antennas. In this paper, some new characteristics of microstrip equilateral triangular patch resonator with fractal defection are analyzed, and novel fractal bandpass filters using equilateral triangular resonator are presented to implement high performances of multi-transmission zeros, wide passband and stopband, and low passband insertion loss as well as miniaturization. Using fractal defection in patch, multi higher order modes are inspired for coupling a much wider passband, and parasitical harmonics are effectively suppressed. A new bandpass filter with a wide passband of about 0.92 GHz (er =9 .8) or 2.7 GHz (er =2 .2), maximum passband insertion loss of less than 0.5 dB, and multi-transmission zeros at both sides of passband, and a second bandpass filter with wide passband and stopbands of more than 2 GHz are implemented. Compared with some literatures, sizes of the new filters reduced and performances are greatly enhanced. The proposed filters have compact and simple structures, small sizes, high selectivity and so on, and all these features are the requirement of wireless communication circuits.