Wide Stopband Rejection Research Articles

Harmonic suppression in short-circuited stub bandpass filter by means of a new miniaturized bandstop filter

In this article, a conventional short-circuited stub bandpass filter cascaded with a new miniaturized bandstop filter is presented which results in suppression of the spurious signals. The crown bandstop filter is proposed and designed using transmission line model. The combination of a crown bandstop filter, a complementary spiral resonator and a spurline is used to obtain the proposed bandstop filter with wide stopband and high rejection level. The proposed bandstop filter size is 0.31λg* 0.31λg and has a wide 3-dB stop bandwidth of 3.5 GHz. The prototype of the harmonic suppressed short-circuited stub bandpass filter is fabricated and measured. The measured upper stopband is better than 30 dB up to 3.5f0. The measured results are in good agreement with corresponding simulation results.

A Wide Stopband Balun Bandpass Filter with Its Application to Balanced Quasi‐Yagi Antenna

A new microstrip balun bandpass filter (BPF) with wide stopband is presented. It is realized by utilizing the out‐of‐phase feature of standing‐wave distribution on a half‐wavelength (λ/2) open‐ended microstrip line and the resonant characteristics of the triple‐mode resonators. For demonstration, a prototype balun BPF operating at central frequency (f0) of 2.34 GHz with fractional bandwidth (FBW) of about 16.7% is designed. The presented balun BPF not only exhibits nice balanced response with 0.47 dB magnitude imbalance and 4.3° phase difference but also achieves 30‐dB harmonic suppression up to 6.40 GHz (2.7f0). Afterward, this presented design is embedded into a balanced quasi‐Yagi antenna to obtain high‐selective radiation and wide stopband rejection. Experimental results of the implemented antenna indicate less than −10 dB reflection coefficient, 4.49–5.38 dBi gain, and 12.71–19.62 dB front‐to‐back ratio within the operating bandwidth.

Compact UWB BPF with notch-band using SIR and DGS

This paper presents a novel ultra wideband (UWB) bandpass filter (BPF) with a notch-band at specified frequency. Moreover, its equivalent circuit model (ECM) is also investigated. The proposed filter consists of a stepped impedance resonator (SIR), a parallel coupled feed line on the top and a rectangular shaped defected ground structure (DGS) on the bottom of the structure. The notch band can be shifted to any other desired frequency by tuning the length of the parallel coupled feed line. Good performances in terms of wide stop-band rejection, low insertion loss, high return loss and more compact size (7.99 × 6 mm2) than those reported in literature are achieved. In addition, simulation results accomplished by ECM are in good agreement with the full-wave EM.

Compact UWB BPF with notch-band using SIR and DGS

This paper presents a novel ultra wideband (UWB) bandpass filter (BPF) with a notch-band at specified frequency. Moreover, its equivalent circuit model (ECM) is also investigated. The proposed filter consists of a stepped impedance resonator (SIR), a parallel coupled feed line on the top and a rectangular shaped defected ground structure (DGS) on the bottom of the structure. The notch band can be shifted to any other desired frequency by tuning the length of the parallel coupled feed line. Good performances in terms of wide stop-band rejection, low insertion loss, high return loss and more compact size (7.99 × 6 mm2) than those reported in literature are achieved. In addition, simulation results accomplished by ECM are in good agreement with the full-wave EM.

Compact dual bandpass filter for terrestrial radio and GSM applications

A Compact Dual Band-Bandpass Filter (DB-BPF) with wide stopband rejection is proposed in this article. The basic tools used in the structure are Short Circuited Stepped Impedance Resonators (SCSIR), Open Stub Resonators (OSR). First, a Single Band-Bandpass Filter (SB-BPF) is designed with wide stopband rejection, and then it is modified to DB-BPF. Both the SB-BPF and DB-BPFs have similar type of construction except for an additional SCSIRs used in DB filter. The structure of the filters, use the source-load coupling and OSR to generate transmission zeros, which suppresses harmonics and achieves wide stopband. The use of SCSIRs make the SB and DB bandpass filters size compact to 0.099λg×0.094λg and 0.118λg×0.092λg, where λg is guided wavelength with a wide stopband upto 6.85f0 with 22 dB suppression for SB-BPF and 2.78f1/7.57f0 with 22 dB suppression for DB-BPF, where f0 and f1 are centre frequencies of first and second passbands respectively.

DUAL-BAND BANDPASS FILTER USING COMPOSITE COUPLING STRUCTURE FOR CPW/MICROSTRIP

By using a composite coupling structure for coplanar waveguide (CPW)/microstrip, a new dual-band bandpass filter (DBBPF) stacking inverted Y-shaped CPW resonators and rectangular ring resonators is proposed. Two resonant frequency bands are simultaneously excited by the CPW feed line. However, it can be convenient to tune individually. Several transmission zeros are realized to improve the selectivity of the filter and achieve wide stopband rejection. Good agreement between simulated and measured results demonstrates the validity of this DBBPF.

Ku‐band compact bandpass filter with wide upper stopband using multilayer liquid crystal polymer technology

ABSTRACTAn improved compact bandpass filter (BPF) with ultrawide upper stopband on three‐layer liquid crystal polymer substrate is presented. In this work, a broadside‐coupled H‐shape resonator and open circuited with radial stub are used to realize compact BPF. The first BPF is designed with three broadside‐coupled H‐shape resonators, which are placed on the top layer and middle layer, respectively. To improve the selectivity and reduce the size while not widen the bandwidth, an improved filter based on the first filter is proposed, which adds two open circuited with radial stubs and removing two H‐shape resonators. The measured results show that the second filter has better selectivity and much more compact size of 6 mm × 6 mm (about 0.52λg × 0.52λg) while keeping wide upper stopband and high rejection, comparing with the first filter, which size is 7 mm × 8 mm (about 0.61λg × 0.7λg). © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1121–1125, 2015

COMPACT MICROSTRIP NARROW BANDPASS FILTER WITH GOOD SELECTIVITY AND WIDE STOPBAND REJECTION FOR KU-BAND APPLICATIONS

A new microstrip narrow bandpass filter with good selectivity and wide stopband rejection for Ku-band application is proposed in this letter. The characteristic of the triple-mode stub-loaded resonator has been investigated. The resonance frequencies of the degenerate modes can be adjusted easily to satisfy the bandwidth of the narrow bandpass filter. Two parallel-coupling feed structures with cross-coupling have been used to generate two transmission zeros at the lower and upper stopband, which can improve the filter selectivity. To validate the design theory, a new microstrip Ku-band narrow bandpass filter has been designed, fabricated, and measured. Simulated and experimental results are provided with good agreement.

Novel Spurious Suppression Approach for SIR Dual-band Bandpass Filter Design

Abstract A new design approach for a stepped impedance resonator (SIR) dual-band bandpass filter (BPF) with high multi-spurious suppression is proposed in this paper. The external coupling property of an SIR at multi-order resonant frequencies is fully studied. Different input impedances at desired frequencies are achieved by optimizing the unequal impedance transformer. The new solution shows the freedom in the choice of tapping point. The external quality values of multi-order harmonics vary with the shift of the tapping position. Wide upper stop-band rejection is realized by mismatching Qe at the unwanted harmonic frequencies, while keeping the Qe suitable for operating dual band to obtain good in-band performance. A traditional dual-band BPF and a novel practical BPF operated at 2.45/5.25 GHz are designed and fabricated to demonstrate the above idea. Good simulated and measured results are presented.

Low-pass filter with deep and wide stop band and controllable rejection bandwidth

Novel design of low-pass microwave filters based on cascading of identical unit cells is proposed. Dispersion relation is used to determine the cell parameters for a given relative stop-band width. For a filter consisting of two cells, each made of single- or two-section transmission lines, the design formulas and curves are presented. Based on them typical filters are designed, fabricated, and measured. The presented filters feature a deep stop band and a wide rejection band, which can be controlled within the proposed design procedure. The design procedure and the simulation results are verified experimentally by measurement of the fabricated structures containing two and three cells.

Compact Lowpass Filter with Wide Stopband Using Windmill-Shaped Resonator

A novel compact lowpass filter using the windmill-shaped resonator is proposed. The proposed filter has 3-dB cutoff frequency at 4.4GHz and 20dB rejection at 5GHz (the transition band is only 0.6 GHz). The filter has wide stopband with attenuation level better than −20dB from 5 up to 20.9GHz. In this work, we have reached the high and wide rejection in stopband with the compact size as well as good insertion and return loss. Finally, the proposed filter has been fabricated and good agreements between the simulated and measured results are obtained.

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.

Quasi‐lumped bandpass filter with sharp transition edge and wide stopband rejection

Presented is a highly miniaturised bandpass filter (BPF) with superior passband selectivity and high rejection over a wide stopband for 2.4 GHz WLAN applications. The proposed third-order coupled resonator design with a cross-coupled path provides an attenuation pole that is very close to the passband. Properly setting the fractional bandwidth and the resonator Q factor yields a sharp transition edge to suppress a 2.1 GHz WCDMA signal. Furthermore, the use of quasi-lumped LC resonators reduces the area of the BPF and generates multiple transmission zeros to enhance the desired stopband rejection.

Wide-stopband microstrip low-pass filter using modified semi-circle patch resonator

In this article, a compact microstrip low-pass filter with elliptic-function response is proposed. To achieve wide stopband, modified semi-circle patch resonator in series with semi-circle stepped impedance resonator is used. The proposed structure achieves a wide stopband and a high selectivity within a small circuit area. The proposed filter has 3-dB cutoff frequency at 1.71 GHz and 20 dB rejection at 2.1 GHz. The stopband with the attenuation level better than −18.7 dB is from 2.08 up to 16 GHz, and consequently we have reached the high and wide rejection in stopband as well as compact size. The structure is simulated, fabricated and measured. The measured results are in good agreement with the simulated results.

Design of a compact and sharp-rejection low-pass filter with a wide stopband

In this paper, a compact and sharp-rejection low-pass filter is proposed and analyzed. By combining a stepped-impedance shunt open stub and two additional shunt open stubs, a compact low-pass filter with wide upper stopband and very high passband selectivity is realized. Wide stopband and sharp rejection characteristics are achieved by realizing three transmission zeros near the passband edges. This filter demonstrated very good measured characteristics at cut-off frequency ( of 2.49 GHz, including a low insertion loss of dB, a wide stopband from 2.8 to 7 GHz and an attenuation slope of 49 dB/GHz. Experimental results also show a good agreement with the predicted results.

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.

Microstrip Lowpass Filter with Very Sharp Transition Band and Wide Stopband

A novel lowpass filter with a very sharp transition band and wide stopband is proposed. The proposed filter is based on Tshaped patches which are etched in symmetrical structures and folded open stub. To obtain a wide stopband, we have used stub loaded semi-circle stepped-impedance structures. By designing the resonator with high inductance and capacitance, a very sharp transition band is achieved. The proposed filter has a 3-dB cutoff frequency at 2.37 GHz and a 40-dB rejection at 2.44 GHz. The stopband with an attenuation level better than −13.2 dB is up from 2.4 GHz to 16 GHz, and consequently we have reached the high and wide rejection in stopband with compact size. Good agreements between the simulated and the measured results are presented.

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 filter with high and wide rejection in stopband using front coupled tapered CMRC

A front coupled tapered compact microstrip resonator cell is proposed. It consists of a microstrip transmission line with high impedance, two tapered with front coupled and two arms at two ends of the high impendence transmission line. The proposed filter has low insertion loss, high return loss in the passband and high and wide rejection in the stopband, as well as compact size. The demonstrated filter has been designed, fabricated and measured. Good agreements are obtained between its measured and simulated S-parameters.

Design of the Compact Dual-Band Bandpass Filter With High Isolation for GPS/WLAN Applications

In this letter, a novel compact dual-band bandpass filter (BPF) is designed to achieve the characteristic of low insertion loss and high isolation for global position system (GPS)/wireless local area network (WLAN) applications. This BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio (alpha) of the asymmetric stepped-impedance resonator (SIR) with one step discontinuity. The coupling coefficient between the coupled asymmetric SIRs is calculated by using full-wave simulator IE3D. The proposed filter has very good measured characteristics including a low insertion loss of 1.1 dB for both passbands, a high isolation insertion loss of 55 dB between the two passbands and a wide stopband rejection of 38 dB from 2.7 to 5.3 GHz. Good agreement with responses of electromagnetic (EM) simulation and measurement is compared.