Evanescent-Mode Bandpass Filters Using Folded and Ridge Substrate Integrated Waveguides (SIWs)

A novel evanescent-mode bandpass filter (BPF) is presented using folded and ridge substrate integrated waveguides (FSIWs & RSIWs). Both measured and simulated S-parameters are presented to show the characteristics, with good agreements achieved between them. It is experimentally validated that such a BPF has better performance in spurious suppression and much smaller size than those of conventional SIW cavity-coupled counterparts.      

Small Ultra-Wideband (UWB) Bandpass Filter With Notched Band

A compact ultra-wideband (UWB) bandpass filter (BPF) with notched band has been proposed and implemented in this letter. H-shaped slot is studied and adopted to tighten the coupling of inter-digital capacitor in order to improve the BPF's performance. Three pairs of tapered defected ground structures (DGS) are formed to assign their transmission zeros towards the out of band signal, thereby suppressing the spurious passband. Combining these two structures we obtain a small sized UWB BPF. Meander line slot is developed to reject the undesired wireless local-area network (WLAN) radio signals. An experimental UWB filter with notched band was fabricated with 35% less length as compared to an embedded open-circuited stub. The measured BPF insertion loss is less than 1.0 dB throughout the pass band of 2.8 to 10.8 GHz, the variation of group delay less than 0.20 ns in this band except for the notched band, and a wide stopband bandwidth with 20 dB attenuation up to at least 20.0 GHz.     

Short-circuited CPW multiple-mode resonator for ultra-wideband (UWB) bandpass filter

An ultra-wideband (UWB: 3.1-10.6 GHz) bandpass filter (BPF) on coplanar waveguide (CPW) is proposed, designed and implemented. A nonuniform CPW multiple-mode resonator with short-circuited ends is constructed and its first three resonant modes are properly allocated around the lower-end, center and higher-end of the specified UWB band. This CPW resonator is then driven at two ends by two parallel-coupled CPW lines with dispersive inductive coupling degree. By properly reallocating the enhanced coupling peak toward the UWB's center, a five-pole CPW BPF with one full-wavelength can be eventually constituted. Its UWB bandpass performance is characterized and optimized on the basis of a simple transmission-line network. Predicted results are confirmed by experiment. Measured results achieve the insertion loss <1.5dB and group delay variation <0.35ns in the realized 3.3 to 10.4GHz UWB passband.     

Angular Bend Half Mode Substrate Integrated Waveguide (HMSIW) Based Band-Pass Filter with Multiple Transmission Zeroes

Wireless Personal Communications - Design methodology of 90° bend half mode substrate integrated waveguide (HMSIW) band pass filter (BPF) is presented in this paper. Edge wall reflections...     

Dual band notched UWB-BPF based on hybrid microstrip-to-CPW transition

The research paper proposes a compact dual notched band ultra-wideband (UWB) bandpass filter (BPF). The basic architecture of the filter is developed using the hybrid microstrip-to-coplanar waveguide (CPW) technology, wherein a short circuited CPW in ground is coupled vertically via the dielectric to the microstrip lines on the top plane. The broadside alignment generates a three pole BPF with dual transmission zeros (TZs) on either passband/stopband edges which leads to minimum insertion loss passband and sharp roll-offs. Later, multiple spirals and split ring resonators (SRRs) are embedded in the CPW of the UWB filter to introduce the dual notches and widen the stopband respectively. The proposed filter is fabricated to justify its measured response. The proposed filter measures only 14.6 × 7.3 mm².     

Coplanar Waveguide Bandpass Filters With Compact Size and Wide Spurious-Free Stopband Using Electromagnetic Bandgap Resonators

This work presents a novel coplanar waveguide (CPW) bandpass filter (BPF) that uses electromagnetic bandgap (EBG) resonators to reduce the size and suppress the harmonic responses. The propagation characteristic of the EBG structure is investigated by its associated equivalent circuit model. Compared with the conventional half-wavelength resonator at 5GHz, the EBG resonator is 60.5 % more compact. Based on the EBG CPW resonators, the inductively-coupled two-pole BPF with 3.8% 3-dB bandwidth and 2-dB insertion loss at 5GHz is implemented. This structure generates a 59.6% reduction in size and suppresses a second harmonic passband when compared with a conventional filter. To eliminate the third harmonic response, the proposed EBG CPW BPF further incorporates two EBG structures into its input and output ports and has the merit of a small circuit area     

Design of an RF Low-Noise Bandpass Filter Using Active Device Reduction Technique

This letter presents a new design for the radio frequency low-noise bandpass filter (BPF) using the active device reduction technique. In a conventional active BPF based on the negative resistance method, the number of active devices depends on the order of the BPF. In the proposed design, the number of active devices is reduced in half, using the suggested new technique. Compared with the conventional active BPF, the proposed one shows better noise figure and consumes less power. We apply this technique to the design of the second order BPF and verify that the measured results exhibit good active filter performances     

A broad-band tunable CMOS channel-select filter for a low-IFwireless receiver

This paper presents a broad-band bandpass filter (BPF) designed as a channel-select filter for wireless applications. It is implemented as a low-pass filter (LPF) in series with a high-pass filter (HPF) for lower power consumption compared to true BPF. Semiscaling of the filter nodes is superior in the wireless receiver over traditional full scaling. The HPF is built with low-pass feedback of an amplifier. The bandwidth is selectable from 625 kHz, 2.5 MHz, or 10 MHz. The filter stopband loss is more than 50 dB extending beyond 100 MHz, and passband ripple less than 2.5 dB. Fabricated in a 0.6-μm CMOS process, it provides a minimum input noise of 16 nV/√Hz noise with 22.5-dBm out-of-band IIP3, while draining an average 14 mA from 3.3 V     

Design of a Wide Stopband Microstrip Bandpass Filter With Asymmetric Resonators

In this letter, a novel microstrip bandpass filter (BPF) with asymmetric resonators is presented. With the asymmetric structure and capacitively loaded coupling, a wide bandwidth with sufficient rejection level can be achieved easily. A full-wave electromagnetic simulator IE3D is used, and the prototype of the BPF is fabricated and measured. Comparisons of simulated results and experimental data are shown; moreover, good match validates the proposed filter.     

Dual-mode dual-band bandpass filter for single substrate configuration

A novel dual-mode dual-band bandpass filter (BPF) is proposed that uses a bi-interdigital coupling structure for a single substrate configuration. The BPF consists of a microstrip feed network, ground embedded slots, and outer and inner loop resonators which are excited over bi-interdigital coupled lines with tight coupling in the two passbands. The filter design, analysis via the equivalent circuit of the proposed BPF and the experimented results are dealt with.     

Planar microstrip UWB bandpass filter using U-shaped slot coupling structure

A compact planar microstrip UWB bandpass filter is proposed. It is realised by cascading a lowpass filter and a highpass filter. A transmission line with U-shaped slots coupled with two DGS units on the back of the circuit board has the characteristic of highpass, while a periodic uniform DGS array has the characteristic of lowpass. Combining these two structures, a new UWB bandpass filter (BPF) is fabricated and measured. Measured results show that the proposed BPF has wide bandwidth from 3.0 to 10.9 GHz, all the measured return loss less than 13 dB in the passband. The BPF achieves a wide stopband with 18 dB attenuation up to 18.0 GHz     

A novel microstrip dual-mode bandpass filter with harmonic suppression

A novel dual-mode microstrip bandpass filter (BPF) with harmonic suppression is presented in this letter. The filter is composed of a perturbed square-ring resonator and two end-open L-shaped microstrip lines for the input and output of the resonator. The harmonic suppression of the BPF may be realized by choosing a proper length for the L-shaped microstrip line. The BPF has been investigated numerically and experimentally. Measured results show that the stop-band of the filter is increased up to near the third-order harmonic of the square-ring resonator due to harmonic suppression, and the rejection level is kept below -27dB.     

Design of a Wide Stopband Microstrip Bandpass Filter With Interdigital Resonators

In this letter, a novel microstrip bandpass filter (BPF) with interdigital resonators is presented. With the interdigital resonators and shorted asymmetrical coupled-lines, a wide bandwidth with sufficient rejection level can be achieved easily. A full-wave electromagnetic simulator IE3D is used, and the prototype of the BPF is fabricated and measured. Comparisons of simulated results and experimental data are shown; moreover, good match validates the proposed filter.      

Compact ultra-wideband bandpass filter using broadside coupled hairpin structures on multilayer liquid crystal polymer substrate

A novel ultra-wideband (UWB) bandpass filter (BPF) using a broadside- coupled hairpin structure and multilayer organic liquid crystal polymer (LCP) technology is presented. To suppress stopband harmonic response, folded stepped impedance structures were adopted as hairpin resonators in the design. The proposed filter has been investigated numerically and experimentally. Multilayer LCP technology was used to implement designed UWB BPF. Good agreement between simulated and measured results of the proposed filter was observed. They show that the fabricated UWB BPF has a good performance, including a small insertion loss, a flat group delay with a variation within 0.1 ns in most of its passband, a wide stopband from 11.0 20.0 GHz with a high rejection level up to 20.0 dB, and a very compact size of 9.8 x 7.5 mm (0.36 lg x 0.27lg, where lg is the guided wavelength of 50 V microstrip line at 6.85 GHz).     

Analytical design of a microstrip UWB BPF with sharp rejection

This paper presents a new Ultra-WideBand (UWB) BandPass Filter (BPF) using half-wavelength (??/2) Stepped-Impedance Stub-Loaded Resonator (SISLR). Analytical equations derived by the even-odd mode analysis show the new filter has two tunable transmission zeros at both sides of the passband to provide a sharp rejection and seven transmission poles inside the passband to achieve U.S. UWB performance. For verification, a UWB BPF is designed, fabricated and measured. The measured results show that the fabricated filter has a -3 dB fractional bandwidth from 3.0 GHz to 10.9 GHz and its insertion loss less than 0.9 dB over the whole passband. Furthermore, the new filter exhibits a simple topology, sharp rejection, and deep stopband suppression.     

Switchable Embedded Notch Structure for UWB Bandpass Filter

A reconfigurable ultra-wideband (UWB) bandpass filter (BPF) with switchable notch for UWB system is presented. The UWB BPF is embedded with two identical switchable notch structures, in which PIN diodes are used for electronic switching. A bias circuit for UWB applications was investigated and designed to control the state of PIN diodes in order to activate or deactivate the notch without an affect on the response of the BPF. A demonstrator for this type of switchable notch UWB filter is designed and fabricated. Simulated and measured results are described.      

Characterization of Average Power Handling Capability of Bandpass Filters Using Planar Half-Wavelength Microstrip Resonators

Several closed-form equations are obtained for characterizing the average power handling capability (APHC) of bandpass filters (BPFs) using planar half-wavelength open-circuited microstrip resonators. It is found that the temperature rise (TR) of the BPF is the product of two terms corresponding to the single microstrip resonator and the filter, respectively. The APHC of an eighth-order open-loop BPF is determined numerically, with good agreements obtained between its maximum TRs calculated using our model and 3-D-FEM software.      

A novel compact interdigital bandpass filter using multilayer cross-coupled folded quarter-wavelength resonators

In this letter, a novel compact cross-coupled interdigital bandpass filter (BPF) is developed. By using multilayer folded quarter-wavelength resonators, the size of the filter is reduced greatly, meanwhile a cross-coupling is introduced to produce transmission zeros and thereby improve the stopband characteristics of the filter. As an example, a four-pole BPF centered at 2.25GHz with a fractional bandwidth of 31% is designed, fabricated, and measured. The simulated and measured results show an excellent agreement.     

An Ultra-Wideband Bandpass Filter With an Embedded Open-Circuited Stub Structure to Improve In-Band Performance

In this letter, we present a compact ultra-wideband bandpass filter (BPF) with a notch band in the BPF performance by using an embedded open-circuited stub structure. The filter mainly consists of conventional stepped impedance resonator (SIR) as the multiple-mode resonator and two enhanced coupled input/output lines. The bandwidth can be analyzed by using the image-parameter method to obtain the proper dimension of the coupled lines and verified by using electromagnetic (EM) simulation. The embedded open-circuited stub structure in the SIR is used to produce a narrow notched band at 5.8 GHz, which its frequency position and bandwidth can be tuned by its physical parameters. The measured 3 dB fractional bandwidth of 113.8% and narrow notched band with 25 dB rejection is achieved. Good agreement between the EM simulation and measurement is obtained.