Passband Loss Research Articles

Coplanar waveguide wideband bandpass filter and its application to ultra-wideband pulse generation

A technique to design wideband coplanar waveguide bandpass filters is reported. The filter is realized by etching a slot on the ground plane around a gap on its central conductor and modifying the gap in the form of parallel lines. It is shown that the 3-dB fractional bandwidth of the filter can be varied from 60 to 110% by tuning the size of the slot aperture and the length of the parallel lines. Equivalent circuit and design steps are presented. Implementation area of the filter having passband 3.2–10.5 GHz is 0.90 λg × 0.26 λg, λg being the guided wavelength at 6.85 GHz while 20-dB stopband is at least up to 18 GHz. Insertion loss is less than 2 dB up to 9 GHz. Area of the filter having fractional bandwidth 60% at 3.85 GHz is 0.67 λg × 0.11 λg. Passband loss is within 1.5 and 20 dB stopband is at least up to 12 GHz. The proposed filter structure is very simple to integrate, and the ultra-wideband filter is used to generate an ultra-wideband pulse as defined by the US Federal Communication Commission. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Suppression of microstrip filter spurious responses using frequency-selective resistive elements

The spurious responses of microstrip filters were suppressed to extend the stop band. Even-order spurious resonances are suppressed using resistive loads at the voltage nodes of the fundamental resonance, which are the antinodes at the spurious frequency. Odd orders are removed using additional resonators which are deliberately lossy, and whose fundamental resonant frequency is equal to the spurious resonance of the main resonators. Equations for initial estimates for losses and required coupling coefficients are given. Of three filters designed and measured, two show 30 dB stop band attenuation, at the cost of only a small increase in pass-band loss and a small increase in substrate area.

High rejection, tunable parallel resonance in micromachined lead zirconate titanate on silicon resonators

This paper presents a micromachined lead zirconate titanate-on-silicon electromechanical resonator, tunable from series to parallel resonance, for either bandstop or bandpass filter applications. Scattering parameter measurements (9.2 V direct current (DC) bias) reveal bandstop rejection levels > 109 dB at 59.74 MHz and passband loss of 40 dB with a −20-dB bandwidth of 25 kHz (0.042%). These compare within 5-dB of the models. Parallel resonance is also observed for an alternate mechanical mode at 182.8 MHz with a 1.5 V DC bias with a rejection of 54.7 dB, a −20 dB bandwidth of 41 kHz (0.022%). This mode is tunable with the electric field to show series resonance.

Design of Compact Ultra-Wide Stopband Lowpass Filter Using a U-Slotted Ground Structure (SGS) and Multilayer-Technique

A compact microstrip lowpass filter using a U-SGS, which has the same meaning as U-Defected Ground Structure (U-DGS), with compensated microstrip is proposed in the paper. The equivalent circuit for the proposed Ushaped DGS and its corresponding L-C parameters are extracted by using its Sparameters response and a simple circuit analysis method. The lowpass filter using three cascaded U-DGS provides a compact size, very good transition sharpness with low insertion loss in passband and wide rejection in the stopband. Measured results show good agreement with the theoretical results. New ideas in order to improve the compactness and the losses of the filter have been proposed. The article presents some promising patents on design of compact ultra-wide stopband lowpass filter using a U-slotted ground structure (SGS) and multilayer-technique. Keywords: Defected ground structure, lowpass filter, multiplayer-technique, reject band, sharp transition, U- resonator, U - Slotted Ground Structure, Ultra-Wide Stopband Lowpass Filter, U-DGS SLOT STRUCTURE, U-DGS SLOT, DESIGN AND FABRICATION

Hilbert-shaped complementary single split ring resonator and low-pass filter with ultra-wide stopband, excellent selectivity and low insertion-loss

A novel Hilbert-shaped complementary single split ring resonator (H-CSSRR) with an alterative split gap was initially presented and studied. Transmission characteristics of several CSSRR cells were assessed by full-wave electromagnetic (EM) simulation and analyzed by electrical simulation (equivalent circuit model). Miniaturization mechanism as well as effective EM parameters retrieval is also involved. Comparing to conventional CSSRR, proposed H-CSSRR was demonstrated with a merit of lower primary transmission zero realized by negative effective permittivity and multi-resonance behavior attributing to self-similarity of Hilbert geometry. For application, a tunable assembled low-pass filter (LPF) by periodically loading H-CSSRR cells and open stubs is designed, fabricated and measured. Measurement results indicate that the designed LPF has many good performances such as relative low insertion loss (maximum 0.59 dB) in passband, ultra-wide stop-band characterized by 20 dB insertion loss (from 2.45 to 25 GHz) as well as steep rejection with sharp transition band (2.15–2.45 GHz) out of band. Excellent property and consistent numerical and experimental results of the developed LPF have confirmed the effectiveness of this design concept.

Mechanically-induced π-shifted long-period fiber gratings

A band-pass filter based on mechanically-induced multi-π-shifted long-period fiber gratings is proposed. The pass band width of the filter depends on the number N of the sub-gratings divided by π-shifts in the long-period fiber grating. The depth of the two lateral rejection bands can be changed by the amount of pressure applied to the fiber. This paper demonstrates a multi-π-shifted long-period fiber grating created by pressing a fiber between two periodically grooved plates. For N = 7 and LP12 mode coupling, the extinction ratio is 22.22 dB, and the pass band loss is 0.85 dB. For LP12 mode coupling, the pass band width varies from 14.23 nm to 39.31 nm when N increases from 2 to 10.

TUNABLE AND SWITCHABLE BANDPASS FILTERS USING SLOT-LINE RESONATORS

In this paper, novel uniplanar tunable and switchable bandpass fllters are designed by using the centrally-loaded slot-line resonator. From the voltage-wave distribution along the resonator, the appropriate location for the loading element is determined to be the center of the slot-line resonator, where the voltages of the fundamental signal and second harmonic are maximum and zero, respectively. As a result, the fundamental frequency can be tuned while the second harmonic remains almost unchanged. For the flrst time, the properties of the centrally-loaded slot-line resonator are analyzed by using the even- and odd-mode method, and their respective resonant frequencies are derived. The demonstrated tunable bandpass fllter can give a 30.9% frequency tuning range with acceptable insertion loss when a varactor is used as the loading element. By replacing the loading varactors with PIN diodes, a switchable bandpass fllter is realized in which the attenuation in the fundamental passband can be controlled. In experiments, the switchable bandpass fllter exhibits a 2.13dB insertion loss in the fundamental passband when the PIN diodes are ofi and more than 49dB isolation across the passband when the PIN diodes are on.

A Concise Periodic Undulate Sine Rectangular Waveguide Bandpass Filter for Millimeter Wave Region

A novel sine rectangular waveguide (SRW) structure with either broad or narrow side periodic undulation is firstly proposed for designing bandpass filter (BPF) at millimeter wave frequency range. The bandpass characteristics of the SRW and two BPFs with a concise transition operated at millimeter wave atmospheric window frequency are studied. The SRW has the advantages of remarkable simplicity and completely closed environment without energy leaking. Besides, energy transmission mode in SRW is a quasi TE10 mode which is similar to that in rectangular waveguide, which means that a SRW can easily get transition to a rectangular waveguide. So, compared to the traditional waveguide cavity BPF using metal diaphragm, printed circuit substrate or complex cross section, the SRW can be directly connected to a standard waveguide without additional metal diaphragm or substrate. To verify the bandpass characteristics of SRW, Ka band SRW BPF was designed and fabricated. Experimental results show low insertion loss (< 0.2 dB) in the whole Ka passband and sharp, wide rejection in the stopband (below-20 dB), with good agreement with simulated results. Therefore, the SRW will have wide potential applications in millimeter wave frequency range.

Suppression of superconducting filter spurious response using lossy parasitic resonators

To increase the upper stop-band width of a superconducting spiral filter, a spurious response was suppressed using additional, deliberately lossy, resonators. Their fundamental resonant frequency is equal to the spurious resonance of the main spirals, and their bandwidth is limited, so they introduce very little loss in the main pass band, and therefore retain the benefits of superconductors. Unintended coupling between resonators is mitigated by iterative design. The absorptive resonators are retro-fitted to an existing filter, and being on a separate, low-cost, substrate in a plane parallel to the main filter, require no additional space, incur only a slight additional cost, and because the metal box is unchanged, result in little extra thermal capacity (which prolongs heating and cooling cycles).

A new approach to designing varicap-tuned filters

A new approach to designing electrically tuned bandpass filters that is based on the use of U-shaped resonators with several varicaps connected to each of the resonators is proposed. This approach makes it possible to improve the characteristics of the existing filters, reduce the filter passband loss and intermodulation distortions, and obtain narrow passband widths of 2% or less. It has been found experimentally that, using the new approach, the insertion loss that is similar to the loss of the filters based on p-i-n diodes has been obtained with tunable filters based on semiconductor varicaps for the first time.

Design and Analysis of a Novel Tunable Band-Stop Filter Using RF MEMS Technology

This paper presents a tunable band-stop filter within frequency ranges of 15-30 GHz, it used a novel method to turn the resonant frequency by micro-electromechanical systems (MEMS) switch and coplanar-waveguide (CPW) structures. The DC voltage is utilized to load RF-MEMS switch as source of the tunable cell’s power. The simulation obtained by HFSS and ADS tool shows that insertion loss is less than 1dB in pass-band and return loss is greater than 10 dB. The center frequency changes from 15.5 GHz to 26 GHz, which has 10.5 GHz adjustable range. The result shows good stop rejection and sharp roll off frequency and the extracted result from the circuit matches simulation result very well in this paper.

Band-pass filters using high-permittivity ceramics substrate

The miniaturization of ring band-pass filters by employing high-permittivity ceramic substrates (with respective dielectric constants of 9.7 and 23.5) are investigated. Microwave dielectric ceramics with high-permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high-permittivity ceramics can be used as the substrate for band-pass filters. Moreover, the fundamental characteristics of newly developed compact ring resonators have also been described and applied to the design of band-pass filters. In this article, the designed ring resonators structures are simulated using an HFSS simulator. The responses of the fabricated band-pass filters using Al2O3 (εr = 9.7, tanδ = 0.0001) and 0.875Mg0.95Zn0.05TiO3-0.125Ca0.8Sm0.4/3TiO3 (εr = 23.5, tanδ = 0.000083) ceramic substrates are designed at the center frequency of 2.4 GHz. This compact size, low loss band-pass filter should be useful in many wireless communication systems. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2344–2347, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25439

Design of a K-Band Chip Filter With Three Tunable Transmission Zeros Using a Standard 0.13-$\mu\hbox{m}$ CMOS Technology

A novel bandpass filter (BPF), which is fabricated with a commercial CMOS process, demonstrating a low insertion loss in the passband and multiple transmission zeros in stopbands, is presented for 24-GHz automotive ultrawideband (UWB) radar systems. The filter combines a second-order asymmetrically compact resonator filter with a source-load coupling mechanism to realize three transmission zeros; two zeros are arranged in the lower stopband, and one zero is located in the upper stopband. To achieve a compact layout size and a low insertion loss, a semilumped approach, which is accomplished with mixed utilization of high-impedance coplanar waveguide lines and lumped capacitors, is used to construct the chip filter. A K-band experimental prototype that has a very compact size of 0.35 × 0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was realized. The average insertion loss in the filter's passband is about 2.7 dB, the return loss is greater than 15 dB within the frequencies of 24-27.5 GHz, and the attenuation levels at the three transmission zeros all greater than 35 dB.

Improving the stopband of microstrip parallel-coupled line bandpass filters using partially coupled resonators

An effective method is introduced to improve the stopband performance of microstrip parallel-coupled line bandpass filters. The proposed filter is constructed by adding several partially coupled resonators close to each trace in the conventional microstrip parallel-coupled line bandpass filter. The lengths of the coupled section and the stub section in each partially coupled resonator are selected such that the desired transmission zero is obtained. Proper selection of the number and the frequency of each transmission zero eventually makes it possible to suppress the unwanted spurious responses. In order to demonstrate the characteristics of the proposed filter, a third-order bandpass filter, which is centred at the operating frequency of 1 GHz with 10% fractional bandwidth, is designed, tuned, fabricated and tested. Measurement and simulation results show that the proposed prototype has a broad upper stopband performance, whereas it keeps the desired passband loss and shape almost equal to that of the conventional ones.

Complimentary Bifilar Archimedean Spiral Resonator(CBASR)를 이용한 저위상 잡음 전압 제어 발진기

본 논문에서는 complimentary bifilar archimedean spiral resonator(CBASR)를 이용하여 저위상 잡음 특성을 갖는 새로운 구조의 전압 제어 발진기를 제안하였다. CBASR은 작은 면적, 저지대역에서 날카로운 스커트 특성과 통과대역에서 낮은 삽입 손실, 큰 결합 계수 값을 나타내며, 이로 인해 높은 Q값을 구현할 수 있는 장점이 있다. 따라서, 본 논문에서는 CBASR을 공진 회로로 사용하여 전압 제어 발진기의 위상 잡음을 개선시켰다. 제안된 전압 제어 발진기의 주파수 조절 범위는 제어 전압 0~5 V에서 2.396~2.502 GHz이며, 출력은 7.5 dBm, 그리고 위상 잡음 특성은 100 kHz offset에서 -119.16~-120.2 dBc/Hz이다. In this paper, a novel voltage-controlled oscillator(VCO) using the complimentary bifilar archimedean spiral resonator(CBASR) is presented for reducing the phase noise characteristic. A CBASR has compact dimension, a sharp skirt characteristic in stopband, a low insertion loss in passband, and a large coupling coefficient value, which makes a high Q value and improve the phase noise of VCO. The proposed VCO has the oscillation frequency of 2.396~2.502 GHz in the tuning voltage of 0~5 V, the output power of 7.5 dBm and phase noise of -119.16~-120.2 dBc/㎐ at the offset frequency of 100 kHz in tuning range.

A compact ultra‐wide stopband, low insertion loss, and sharp cutoff low‐pass filter

AbstractA novel compact microstrip low‐pass filter (LPF) with ultra‐wide stopband, low insertion loss, and sharp cutoff is introduced in this letter. The LPF is composed of a stepped‐impedance hairpin resonator, a square split‐ring resonator, defected ground structure (DGS), and a pair of coupled DGSs with compensated microstrip lines. Measured results show that the 10‐dB stopband is up to 19.62 GHz, passband loss is below 0.5 dB, and the selectivity of the filter is more than 180 dB/GHz, but its occupied area is only 20 × 35 mm2. It can be widely used for higher harmonics suppression for wideband microwave applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 568–570, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24976

Compact lowpass filter with wide stopband using open stubs loaded tapered compact microstrip resonator cell

we have proposed an open stubs loaded tapered compact microstrip resonator cell (OSL-TCMRC) for designing of the lowpass filter with wide stopband and low insertion loss. By optimization of this structure and insertion of open stubs, undesirable response and harmonics will be suppressed. In order to validate the proposed design, a lowpass filter with low insertion loss in passband and wide stopband is designed, fabricated and measured. Simulation results are compared to the experimental results and good agreement between them was achieved.

Analysis and Design of a Chip Filter With Low Insertion Loss and Two Adjustable Transmission Zeros Using 0.18-$\mu{\hbox{m}}$ CMOS Technology

This paper presents the structure of a high-selectivity bandpass filter that is fabricated on low-resistivity silicon substrate with a commercial CMOS technology. The filter is constructed using crossed coplanar waveguide (CPW) lines and metal-insulator-metal capacitors to ensure that it has the desired passband characteristics. An adjustable capacitor between the input and output ports is employed to form a capacitive cross-coupled path, yielding two transmission zeros in the lower and upper stopbands, respectively. Additionally, the coupling mechanism can be modified by turning on or off the gate of an nMOS transistor to adjust the positions of the transmission zeros by applying an externally controlled voltage. To obtain a low passband loss and to minimize the chip size, high-impedance CPW transmission lines are adopted. Our analysis indicates that the CPW line possesses more advantages than the preferred stacked-ground CPW line for constructing the proposed filter. A very compact X -band experimental prototype with a size of 0.88 × 0.54 mm2 was designed and fabricated. The measurements reveal an insertion loss of less than 3.2 dB in the passband, which is from 10.6 to 12.7 GHz, and rejection levels greater than 35 dB at the designed frequencies of transmission zeros. Moreover, the lower and upper transmission zeros can be shifted from 5 to 6.5 GHz and from 18 to 21.4 GHz, respectively, by changing the controlled voltage.

Electronically Reconfigurable Microwave Bandpass Filter

A new class of reconfigurable bandpass filter based on parallel-coupled switched delay line approach is presented in this paper. The approach allows both center frequency and passband bandwidth to be reconfigured electronically. In contrast to conventional approach, the effects of the switch losses are relatively insignificant and can be treated as an auxiliary effect and therefore the filter has low passband loss. Despite the loss performance, the filter provides excellent linearity performance with large power handling capability. Theoretical analysis is presented and the feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The first filter prototype provides narrowband quasi-elliptic filter response with constant bandwidth (50-MHz) tuning across 45% tuning range. The minimum stopband rejection level is 45 dB. The second filter possesses passband-width 3:1 ratio tunability. The third filter provides both functionalities which allow center frequency and passband bandwidth to be reconfigured. All filters have a < 4-dB passband loss with an OIP3 of >20 dBm and are immune from power saturation effect. The measured results demonstrate improved performance in terms of linear and nonlinear characteristic compared with prior works.

Microstrip ring resonator bandpass filters using ceramic substrate

AbstractThe miniaturization of ring bandpass filters by employing high‐permittivity ceramic substrates (with respective dielectric constants of 9.7 and 23.5) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high‐permittivity ceramics can be used as the substrate for bandpass filters. Moreover, the fundamental characteristics of newly developed compact square‐ring resonators have also been described and applied to the design of bandpass filters. In this paper, the designed square‐ring resonators structures are simulated using an IE3D simulator. The responses of the fabricated bandpass filters using Al2O3 (εr = 9.7, tan δ = 0.000036) and 0.875Mg0.95Zn0.05TiO3‐0.125Ca0.8Sm0.4/3TiO3 (εr = 23.5, tan δ = 0.000021) ceramic substrates are designed at the center frequency of 2.4 GHz. This compact size, low loss bandpass filter should be useful in many wireless communication systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 218–220, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24847