dB Stopband Research Articles

A fully integrated programmable dual-band RF filter based on electrically and mechanically coupled CMOS-MEMS resonators

In this paper, a novel fully integrated CMOS-MEMS filter implemented on a commercial CMOS technology is presented. The combination of mechanical and electrical coupling is used to enhance the response of the band pass filter. In particular, a 20 dB shape factor as low as 2 and a 35 dB stopband rejection are achieved. Moreover, the topology of the device allows obtaining a dual-bandpass filter behavior, presenting a tunable bandwidth and a deep notch between bands. Results show a dual-band filter with a 22 dB inner stopband rejection, center frequencies at 27.5 and 27.8 MHz, respectively, and a 0.6% relative bandwidth.

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.

Compact Wideband Bandstop Filter With Five Transmission Zeros

A compact parallel-coupled transmission line section, connected at their both ends, is presented to obtain multiple transmission zeros. As much as five transmission zeros can be obtained. The zeros can be arranged to design a sharp rejection wideband bandstop filter (BSF). A lossless transmission line model is used to analyze the structure and hence to obtain closed form expressions for the -parameters and design graphs to facilitate the filter synthesis procedure. Theoretical predictions are validated by fabricating a BSF in microstrip line technology. The single filter unit provides 29 dB stopband over a fractional bandwidth of 60% at the mid-band frequency of 1.47 GHz.

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.

Quintuple-Mode UWB Bandpass Filter With Sharp Roll-Off and Super-Wide Upper Stopband

This letter presents a quintuple-mode ultra-wideband (UWB) bandpass filter (BPF), using a multiple-stub-loaded resonator, consisting of multiple loaded stubs to a uniform transmission-line resonator, i.e., two asymmetrical stepped-impedance stubs at the center and four uniform-impedance stubs at the symmetrical side locations. Six modes including two odd and four even modes are controllable, while the first five modes are allocated within the UWB band. Two transmission zeros generated by the asymmetrical stepped-impedance stub are used to improve the passband selectivity greatly. The resonant mode and transmission zero chart are given, indicating that the higher modes could be suppressed by the transmission zeros generated by the stubs and the parallel-coupled lines. A compact planar UWB BPF is simulated, fabricated and measured, and the 20 dB stopband performance is extended to 29.7 GHz.

Design the birefringent Michelson interferometer based interleaver with ultra-low dispersion and low cost

We design and demonstrate a birefringent Michelson interferometer based interleaver with ultra-low dispersion and low cost. The interleaver consists of polarizing beam splitters (PBS's) and quarter-wave plates and half-wave plates. The PBS's based Michelson interferometers provide the optical path difference for interference between the two orthogonal polarization components and the half-wave plates provide the birefringent needed to minimize ripple of output. The designed interleaver with two-stage interferometer in a 50 GHz channel spacing application exhibits a 0.5 dB passband and a 25 dB stopband both 27 GHz; a channel isolation higher than 35 dB and chromatic dispersion less than ±5 ps/nm within 0.5 dB passband; 1.3 dB insertion loss and 0.3 dB PDL; 0.04 GHz/°C thermal stability. Since all of the optical components can be optically bonded together, the device is robust and easy to be aligned, which reduces labor cost.

Compact wideband bandstop filter with multiple transmission zeros based on edge-coupled parallel line and transmission line signal interference

In this article, we demonstrate that the compact bandstop filter (BSF) configuration consisting of an edge-coupled microstrip line connected in parallel to a transmission line section can produce multiple transmission zeros in the stopband. A lossless transmission model is used to derive the condition for two, three, or four transmission zeros. A prototype BSF at 2 GHz achieving a wide 20 dB stopband bandwidth of 92.8% with sharp rejection along with a better than 30 dB return loss in the passband is fabricated for validation purposes. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2265–2268, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26258

Flat-top and low-dispersion optical interleavers based on nested prism pair structure

A novel flat-top and low-dispersion optical interleaver using ring cavities (RCs) in a Mach-Zehnder interferometer (MZI) is proposed. It is composed of eight mirrors and two nested prism pairs. Each prism and the two mirrors behave as a RC. Phase shift of RC is a periodic function of the frequency of the input light which acts as a phase dispersive mirror. The two phase shifts needed to achieve a flat-top spectral passband are provided by Fresnel reflectivities at the prism-air interface of the two RCs. The optimum interface reflectivities for flat passband, high isolation and low dispersion can be obtained only by choosing an appropriate material for the prism in each RC. The proposed interleaver in a 25 GHz channel spacing application exhibits a 0.5 dB passband greater than 24 GHz (96% of the spacing), a 30 dB stopband greater than 21.2 GHz (84.8% of the spacing), a channel isolation higher than 32 dB and chromatic dispersion ±50 ps/nm within the range of center-frequency ±2 GHz ITU passband.

Compact sharp‐cutoff wide‐stopband low‐pass filters using H‐shaped coupled microstrip line units

AbstractIn this article, a single coupled‐line configuration is presented for the design of compact, sharp‐rejection, wide‐stopband low‐pass filters. The proposed filter topology consists of parallel coupled‐lines shorted at the middle. The filtering action results from the generation of three transmission zeros brought about by cross coupling. Design equations and guidelines to adjust both bandwidth and the rejection depth are provided. Theoretical predictions are validated in microstrip line by fabricating a two‐unit prototype filter having better than 25 dB stopband, which is at least five times the filter cut‐off frequency. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1402–1405, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25166

Packaged Ultra-Wide-Band Bandpass Filter Based on Inverted-T Multiple-Mode Resonators and Inverted-F Impedance Transformers [TC Contests

The packaged UWB bandpass filter based on the inverted-T multiple-mode resonator and inverted-F impedance transformer was designed, fabricated and measured. The inverted-T multiple-mode resonator was designed to have three resonance modes locating inside the passband (3.1-10.6 GHz), ensuring the flat passband insertion loss. The stepped-impedance open stubs in both inverted-T multiple-mode resonator and inverted-F impedance transformer bring numerous desired transmission zeros, helping enhance the stopband attenuation. The transmission-zero frequency is controllable by the step impedance ratio and step length ratio. The capacitive packaging effect from the Stratedge FP118118-1 is absorbed into the inverted-F impedance transformer design. The parasitic cavity modes excited in the enclosed package are suppressed by the microwave absorber attached on the lid. The integration of inverted-T multiple-mode resonator and inverted-F impedance transformer achieves a compact low-loss UWB filter with significant stopband attenuation. The packaging cases with no lid, 3.3 mm height lid, and 6.6 mm height lid were measured. The filter with 6.6 mm height lid achieves the best measured performance, which are a 4.3 dB insertion loss, 9 dB return loss over the passband of 3.1-10.6 GHz and greater than 37 dB stopband attenuation in the lower (0-2 GHz) and upper (12.515 GHz) stopbands.

Flexible fabrication of three-dimensional optical-domain photonic crystals using a combination of single-laser-exposure diffractive-optics lithography and template inversion

We demonstrate inversion of three-dimensional photonic crystal templates fabricated in a large area with diffractive-optics lithography. A custom-designed two-dimensional diffractive optical element was used to generate highly uniform, bicontinuous, three-dimensional photonic crystal templates in a single-laser exposure. Chemical vapor deposition successfully infiltrated the thick periodic polymer structure to deposit amorphous silica and thereby define an all-silica inverted photonic crystal after polymer removal, as confirmed by focused ion-beam milling and energy-dispersive x-ray spectroscopy. The diffractive-optics lithography permitted a large number of uniform layers to form that manifested in the recording of a strong -28 dB stopband in the telecom band.

Microstrip Coupled-Line Lowpass Filter with Wide Stopband for RF/Wireless Systems

We present the design of a compact microstrip lowpass filter with a wide stopband which is up to ten times the cutoff frequency. The filter is based on a coupled-line configuration and shunt open stubs. The open stubs create additional transmission zeros, which are used to extend the stopband of the filter without any additional components or cascaded units. A prototype lowpass filter with a 3 dB cutoff frequency of 0.428 GHz and a 15 dB stopband extended up to 4.77 GHz is fabricated to validate the theoretical predictions.

Bandstop Filters with Comb-Like Electromagnetic Bandgap Structures on CPW Stubs

An ultra-wideband (UWB) band-stop filter (BSF) has been designed with flat responses at a selected frequency by cascading the unit electromagnetic bandgap (EBG) structures in this paper. The BSFs fabricated by the surface micromachining process have immense potential to compactness and low cost. The BSFs are constructed with comb-like EBG structures on a coplanar-waveguide (CPW) and have been investigated numerically. The simulation result of the BSF is demonstrated to have a good performance on its work band. It reveals a 20 dB stopband with a bandwidth of 6.8GHz. The pass-band insertion loss is less than 1.7dB.

Q-Band GaAs Bandpass Filter Designs for ALMA Band-1

We report on the design and experimental results of Q-band GaAs bandpass filters (BPFs) for the Atacama Large Millimeter/submillimeter Array (ALMA) band-1 receiver. The BPF is required to reject the lower side band from 15.3 to 29 GHz while retain minimum insertion loss across the passband of 31.3 to 45 GHz. In order to reduce the size and weight of receiver module effectively, on-chip BPF designs using the commercial GaAs process are proposed. The parallel-coupled BPF with quarter-wavelength resonators is adopted to achieve a wide fractional bandwidth of about 37%. In addition, the capacitive/inductive loaded coupled-line and the stepped-impedance resonator are used to largely reduce the filter size. Moreover, the cross-coupling effect is introduced to create transmission zeros, such that the required 25 dB stopband rejection below 29 GHz can be achieved. Specifically, two GaAs BPFs with sizes less than 1.24times0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are demonstrated. They will be applied to the multi-chip-module version of ALMA band-1 receiver prototype for further system evaluation and feasibility studies.

A Novel High Stop Band All Complementary MOSFET Switched-Capacitor Filter

Problem statement: Filters are widely used in various applications in cluding communications, electronics and biomedical engineering. The performance and size of the filter is of interest especially in chip implementation. A switc hed-capacitor low-pass filter was designed and simulated using a 0.18 µm 1P6M CMOS technology. Approach: This circuit design offered obvious advantages in increasing the stopband attenuation, reducing passband ripple and achieving accurate frequency response. Results: This circuit achieved 53 dB stop band attenuation, less than 0.1 dB passband ripple, a 5 KHz cut-off frequency, a 100 K Hz stopband frequency and consumes 6 mW from a 2 V power supply. Conclusion: The proposed design is very suitable for the reali zation of analog signal processing blocks in complementary MOSFET integrated circuits.

Wide-Stopband and Miniarurized Lowpass Filters Using Sirs-Loaded Hairpin Resonators

Compact elliptic-function microstrip lowpass filters (LPF) using stepped impedance resonators loaded (SIRs-loaded) hairpin resonators are presented in this paper. By adding a pair of coupled SIRs in a conventional capacitor coupling hairpin LPF, two additional transmission zeros are generated to extend the stopband. In addition to one-cell filter, a filter using two SIRs-loaded resonators was also designed, fabricated, and tested. The two-cell filter has a 3 dB cutoff frequency at 2 GHz and a 10 dB stopband from 2.5 to 25 GHz, with a size of only 0.081λg × 0.096λg.

Design and analysis on a Gires-Tournois resonator based interleaver

A flat-top interleaver, in which a mirror on one arm of the Michelson interferomefer is replaced by a G-T resonator, is proposed. In the interleaver, the parameters including the channel spacing of 50 GHz, ripple less than 0.05 dB, −0.5 dB passband of 43 GHz (86% of the spacing), −30 dB stopband of 42 GHz (84% of the spacing), and a channel isolation higher than 40 dB, are achieved.

A MMIC 4.3‐GHz tunable low‐pass filter

AbstractA microwave integrated, tunable, low‐pass filter is presented. This coplanar filter exhibits a wide tuning range of the cutoff frequency (±19% around 4.3 GHz) and a −30 dB stopband that extends up to 30 GHz. Insertion loss is 1.5 dB at low frequencies and return loss is better than 14 dB in the passband. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2566–2568, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23707

Miniaturized superconducting microwave filters

In this paper we present methods for the miniaturization of superconductingfilters. We consider two designs of seventh-order bandpass Chebyshev filters basedon lumped elements and a novel quasi-lumped element resonator. In bothdesigns the area of the filters, with a central frequency of 2–5 GHz, is less than1.2 mm2. Such small filters can be readily integrated on a single board for multi-channel microwavecontrol of superconducting qubits. The filters have been experimentally tested and theresults are compared with simulations. The miniaturization resulted in parasiticcoupling between resonators and within each resonator that affected primarily thestopband and increased the bandwidth. The severity of the error depends on thedesign in particular, and was less sensitive when a groundplane was used under theinductances of the resonators. The best performance was reached for the quasi-lumpedfilter with central frequency of 4.45 GHz, quality factor of 40 and 50 dB stopband.

Equivalent Circuit Analyzed of Complementary Split Ring Resonator DGS for Low Pass Filter

This paper presents a novel complementary split-ring resonator (CSRR) defected ground structure (DGS) for low pass filter (LPF) design. The equivalent circuit (EC) model of the CSRR was extracted and discussed in details. Based on the advantages of the CSRR, a compact LPF was designed without open stubs. The 3-dB cut-off frequency of 4.89 GHz has presented good measured characteristics, including sharp selectivity, very low insertion loss of 0.695 dB and wide stopband from 5.02 GHz to 10 GHz below −32 dB. The LPF with low return loss and high out-band suppression is designed and fabricated effectively.