Compact Lowpass Research Articles

Compact wide stopband lowpass filter using spiral loaded tapered compact microstrip resonator cell

A new spiral loaded tapered compact microstrip resonator cell (SPLT-CMRC) is presented. The addition of spiral stubs to the CMRC creates transmission zeroes in the stopband which extended the stopband of the filter. The proposed resonator is used to design a compact lowpass filter (LPF) with wide and high rejection in stopband. The fabricated filter has a 3 dB cutoff frequency at 8 GHz. The insertion loss in the passband is less than 0.2 dB from DC to 7.2 GHz. The proposed filter has wide stopband from 9.47 to 40 GHz with attenuation level of −20 dB. The demonstrated filter is designed and fabricated. There is a good agreement between the measured and simulated S-parameters.

Design of a compact low pass filter for high power RF generators

Design of a compact low pass filter for high power RF generators

Compact lowpass filter with wide stopband using novel windmill resonator

A compact lowpass filter (LPF) with wide stopband using novel windmill resonators is presented. Compared to some other reported compact and wide LPFs, the LPF using the novel windmill resonator has great improvements on size reduction and stopband width, simultaneously, with a simple geometry. At the 3 dB cut-off frequency of 1.76 GHz, the designed LPF achieves a wide stopband with overall 20 dB attenuation to seven times the cut-off frequency. The compact dimension of this filter is as small as 0.19λg × 0.25λg, where λg is the guide wavelength at the cut-off frequency. The proposed filter is simulated, fabricated, and tested. Measured results show good agreement with simulated ones.

Compact lowpass filter with ultra-wide stopband rejection using meandered-slot dumbbell resonator

A novel meandered-slot dumbbell resonator for designing a compact lowpass filter (LPF) with ultra-wide stopband rejection is presented. Compared with some other reported compact and wide stopband rejection LPFs, the proposed LPF using the novel meandered-slot dumbbell resonator has great improvement on size reduction and stopband width. Delivering a 3 dB cut-off frequency at 2.2 GHz, the designed LPF achieves an ultra-wide stopband of 12.8 times the cut-off frequency with overall 20 dB attenuation. The compact dimension of this filter is as small as , where is the guide wavelength at the cut-off frequency. The proposed filter is fabricated and tested. Measured results show good agreement with simulated ones.

A Miniaturized Semi-Lumped Lowpass Filter With Multiple Transmission Zeros And Wide Stopband

A compact semi-lumped lowpass filter with three lumped capacitors is presented in this paper. With this design, three transmission zeros can be obtained within the stopband to enhance its bandwidth. Furthermore, a transmission zero located near the passband is used to achieve sharp selectivity. A meander line between source and load is also introduced to get a compact size. Therefore, the proposed filter has a sharp skirt and wide stopband in comparison with traditional low-pass filters. A microstrip lowpass filter with lumped capacitors is designed and fabricated with the standard single-layered printed circuit board (PCB) technology. The measured S-parameters of the proposed filter agree well with the simulated ones, and the filter achieves the design performance.

A Compact Lowpass Filter with Four Transmission Zeros Using Single-Sided Compact Microstrip Resonator Cells

A compact lowpass filter using two single-sided compact microstrip resonator cells （CMRCs）with low insertion loss and broad bandwidth is presented. The cutoff frequency is about 1.4 GHz, the insertion loss is less than 0.6 dB and the 20dB bandwidth is up to the range from 2.1 GHz to 9.8 GHz by means of introducing four transmission zeros through two CMRCs. In addition, the simulated results demonstrate that the proposed filter is characterized by a compact size, low insertion loss, sharp transition, low return loss and wide bandwidth.

COMPACT MICROSTRIP LOWPASS FILTER WITH SHARP ROLL-OFF AND WIDE STOPBAND USING SEMICIRCLE ENDED STUB RESONATOR

In this paper, a semicircle ended stub resonator, cascaded to a modifled radial patch to design a compact lowpass fllter with sharp roll-ofi and wide stopband is proposed. This fllter has 3dB cutofi frequency at 1.54GHz. The transition band is only 0.26GHz from 1.54GHz to 1.8GHz with corresponding attenuation levels of i3dB and i20dB respectively. Maximum insertion loss is 0.1dB in the passband, and the stopband bandwidth with the attenuation level better than i20dB is extended from 1.8GHz up to 13.93GHz. So, a wide stopband is achieved. The proposed fllter is designed, fabricated and measured, where there is a good agreement between the simulation and measurement results. The results show that a roll-ofi rate of 65.4dB/GHz together with a relative stopband bandwidth of 154% with the suppression level of i20dB is obtained while achieving a high flgure of merit (FOM) of 23509.

Development and Analysis of Compact Lowpass Filter for UWB Systems

This paper presents a developed compact lowpass filter which is devised by concatenating 'T' and inverted 'T' open stubs on a microstrip line. They are combined to enhance the bandwidth and also to improve the outband performance. Insertion loss of the developed filter is less than -0.15 dB and the return loss is -30 dB at 2.85 GHz. Stopband performance of the filter is less than -20 dB from 5.4 GHz to 7.8 GHz and provides -3 dB cut-off frequency at 4.5 GHz. The final dimension of the fabricated filter with the above features is only 16.17 mm (length) $\times$15.76 mm (width). The response of the developed filter has a good agreement with simulation response.

Compact lowpass filter based on coupled-line hairpin unit

A compact lowpass filter (LPF) with sharp cutoff frequency response and wide rejection bandwidth is proposed. The proposed LPF has a simple structure and comprises one microstrip coupled-line hairpin unit, one spiral slot and two open stubs. A demonstration filter with 3 dB cutoff frequency at 2.0 GHz has been designed and fabricated. Theoretical and simulated results are presented, which are in good agreement with the measured results.

Sharp Roll-Off Lowpass Filter With Wide Stopband Using Stub-Loaded Coupled-Line Hairpin Unit

A novel application of shunt open-stubs at the feed points of a center fed coupled-line hairpin resonator is presented for the design of compact lowpass filter (LPF) with very wide stopband. The transmission zeros of the basic unit are minimally affected by its association with the stubs. The stopband bandwidth and filter roll-off rates achieved here are larger than those achieved earlier. A prototype microstrip LPF having a very wide stopband up to nine times the filter cutoff frequency is fabricated.

Design of compact low pass filter with wide stop band using tri-section stepped impedance resonator

This paper reports the design of a compact low pass filter (LPF) with wide stop band region using tri-section stepped impedance resonators in microstrip medium. Experimental results of a low pass filter designed at 1 GHz have been compared against the analytical and EM simulation results for the validation of the design. Results are satisfactorily matching each other. The maximum insertion of the measured filter is 0.2 dB and minimum return loss is 13.5 dB over the pass band. The stop band rejection is better than 20 dB from 1.5 GHz to 4.2 GHz and hence wide stop band performance is achieved. Overall size of the filter is 30 mm × 20 mm × 0.78 mm which is 0.1 λ × 0.066 λ × 0.0026 λ at 1 GHz.

Design of Compact Low Pass Microstrip Filter For Wireless Communication System

A compact microstrip low pass filter has been designed using step impedance technique. Two slots were cut in the ground plane just below the high impedance microstrip lines. The proposed filter has spurious free response for wide band width with sharp cut-off characteristics. The filter has been designed for a cutoff frequency 2.5 GHz and provides good agreement between the simulated and measured results.

Compact Low Pass Filter Design for L-Band Application

An effective technique to design compact low pass filter has been proposed in this paper. The proposed method is highly effective for L-band applications. Low impedance microstrip lines are arranged such that they work as open stubs to increase the selectivity of the filter. Using the proposed technique about 57% size reduction has been realized with sharper roll off characteristics. An empirical expression is derived to determine the dimension of resonators. For cut-off frequency of 1.7 GHz the investigated method has been fabricated and tested. There is a close agreement be-tween simulated and measured results

A MULTI-BAND MEANDERED SLOTTED-GROUNDPLANE RESONATOR AND ITS APPLICATION OF LOW-PASS FILTER

A slotted-ground-plane meandered-slot resonator with multi-resonance characteristics and a compact lowpass fllter (LPF) by using the resonator are demonstrated in this paper. The meandered slot provides a wideband resonator with low insertion loss and very sharp cutofi frequency response. Unlike conventional design of cascading bandstop slotted-ground-plane resonators in the literature, the introduced LPF is presented, which consists of a modifled-meander slot in the ground plane, a spurred C-like slot, and a uniform microstrip transmission line with constant characteristics impedance. Two rectangular-head slots, giving an increase in the inductance, are added at the two terminals of the meandered slot for purpose of frequency reduction. An arm aperture is embedded to form another resonant path so that an additional transmission zero could be generated. In order to increase rejection capability, the slot width of one section of the meandered-slot resonator is widened. Meanwhile, a C-like slot with a spur slit is also etched inside the meandered slot to improve rejection performance. The measured insertion loss at a passband is below 0.7dB, and the rejection band over 20dB is from 2.9 to 12.0GHz.

Design of wide stopband lowpass filter with sharp roll-off

In this paper, a modified semi-circle patch and a semi-circle stepped impedance resonator are cascaded to design a compact lowpass filter with sharp response and wide stopband. This filter has 3-dB cutoff frequency at 1.55GHZ. The transition band is only 0.29GHZ from 1.55 to 1.84GHZ with -3dB and -20dB respectively. Maximum insertion loss is 0.4dB in the passband and stop bandwidth with attenuation level better than -20dB extends from 1.84GHZ up to 12.5GHZ and up to 15GHZ is greater than -10dB, hence wide stopband is achieved. Simulation and measurement results are presented and good agreement between them is achieved. Results show that we have obtained a high Figure-of-Merit (FOM) of 30433.

Compact lowpass filter with ultra-wide stopband using novel spiral compact microstrip resonant cell

In this paper a novel spiral compact microstrip resonant cell (NSCMRC) to design a low pass filter with wide stopband is presented. The slow-wave effect and scattering and radiation parameters are depicted. The designed lowpass filter is implemented by cascading three cells with different dimensions that shows the advantages of low insertion loss less than 0.03dB and wide stopband from 4GHZ up to 50GHZ with suppression level better than -13.4dB and compact size. Finally, the proposed lowpass filter is fabricated and a good agreement between simulated and the measured results are demonstrated.

Compact wide-stopband lowpass filter using stepped impedance hairpin resonator with radial stubs

A compact lowpass filter using a stepped impedance hairpin resonator is presented. To achieve wide stopband rejection, radial stubs were introduced. The new lowpass filter has been analysed, simulated and fabricated. Measured results are in good agreement with the electromagnetic simulation, and the circuit only occupies 0.08λg×0.08λg.

Compact Lowpass Filters With Sharp and Expanded Stopband Using Stepped Impedance Hairpin Units

This letter presents a novel compact lowpass filter with two transmission zeros. By tap-connecting the stepped-impedance hairpin unit, two transmission zeros can be generated when an interdigital structure is introduced between the two low-impedance sections. Further, the two transmission zeros can be adjusted easily to obtain a larger zero separation without the need to change the stepped-impedance unit. Therefore, a sharp transition, an expanded stopband, a low insertion loss, and a compact size can be obtained simultaneously. Two filters with single and two asymmetric units are designed, fabricated, and tested. The measured results demonstrate good performance: compact size, low passband insertion loss, broad stopband, and sharp skirt characteristic.

New Design Method of UWB Microstrip Filters Using Adaptive Genetic Algorithms with Defected Ground Structures

The effects of adaptive genetic algorithms (AGAs) and defected ground structures (DGSs) on performance optimization of tapered microstrip filter are investigated. The proposed structure achieves an ultra wide stopband with high attenuation within a small surface area, as well as 45% smaller size, in comparison with conventional filters. The parameters of the filter are optimized using in-home AGA code. In the proposed AGA algorithm, the crossover and mutation probabilities are adaptively changed according to the value of individual fitness. Then by utilizing the proposed DGS, a compact S-band lowpass filter with ultra-wide spurious free window is obtained. The proposed filter achieves an insertion loss of 0.8 dB from DC up to 4 GHz and 21 dB rejection in the stopband from 4.3 up to 60 GHz. The fabricated and measured results exhibit good agreement with the simulated results. They demonstrate that combining AGA and DGS yields best possible response for this group of filters.

Compact lowpass filter with sharp transition knee by utilising a quasi- π -slot resonator and open stubs

Designs of a compact lowpass filter using a slotted-ground-plane resonator are presented. Unlike conventional design of cascading bandstop slotted-ground-plane resonators in the literature, the introduced filter is presented, which consists of a quasi-π slot in the ground plane, and a microstrip line with several stepped-impedance (SI) open stubs. The quasi-π slot provides a very sharp cutoff frequency response with low insertion loss. Furthermore, to increase rejection bandwidth, additional transmission zeros are added into frequency characteristics by connecting the SI open stubs at the microstrip line. An equivalent circuit of the proposed lowpass filter is simply represented by resistor, inductor and capacitor (RLC)-lumped elements. According to measured results, compared with a conventional H-slot resonator, the resonance frequency of the resonator is reduced from 3.5 to 2.0 GHz and the ratio of frequency reduction is about 43%. The measured insertion loss at a passband is below 0.3 dB, and the rejection band over 25 dB is from 1.95 to 9.0 GHz.