High Stopband Research Articles

High-Order Infinite Impulse Response Microwave Photonic Filters

Two new high-order infinite impulse response microwave photonic filters, which have multiple poles and zeros in the transfer characteristic, are presented. They are based on either the wavelength division multiplexing technique with a single infinite impulse response delay line structure or a single laser with multiple infinite impulse response delay line structures. A wavelength converter is used to increase the filter order without the coherent interference problem. A high-resolution and high-performance bandpass filter response can be realized. Experimental results are presented that demonstrate high-resolution bandpass filter responses with robust operation, and high stopband rejection level and high skirt selectivity.

Cascaded Multiple Infinite Impulse Response Optical Delay Line Signal Processor Without Coherent Interference

A technique that enables two or more infinite impulse response optical delay lines to be connected in series without the coherent interference problem is presented. It is based on inserting an optical frequency shifter into the infinite impulse response optical delay line structure. Signal processors based on the cascaded optical delay line structure have a higher frequency response performance than the single optical delay line structure. Experimental results are presented, which demonstrate a dual series frequency shifting amplified recirculating delay line can realise a high-resolution, high skirt selectivity, high stopband rejection level bandpass filter response, and a narrow-passband, flat-top bandpass filter response using a non-commensurate delay line approach.

MINIATURIZATION DESIGN OF FULL DIFFERENTIAL BANDPASS FILTER WITH COUPLED RESONATORS USING EMBEDDED PASSIVE DEVICE TECHNOLOGY

This paper presents two full difierential bandpass fllters with small occupied areas. Both fllters are designed with the same basic structure which consists of two double coupled resonators with magnetic coupling. The resonators are stacked up and have the advantage of high coupling e-ciency, reducing the area. Nevertheless, in the basic structure, the insertion loss in the high stopband is above i10dB and therefore does not meet the requirement for bandpass fllter design. Thus, two solutions are introduced to form the proposed fllters. The flrst one integrates the ground plane, while the second one makes the use of an extra transmission zero. With the help of these solutions, two types of full difierential bandpass fllters are implemented on an FR4 using the embedded passive device technology, with the additional purpose of being designed for SiP applications. The passband of the fllters conforms to the WLAN IEEE 802.11a (5GHz) standard. Most importantly, the occupied areas of the two proposed bandpass fllters are only 6mm£6:7mm and 6:6mm£8:3mm respectively. Compared with previous research, area reductions of up to 98.05% and 97.76% can be achieved.

A Packaged Ultrawideband Filter with High Stopband Rejection [Application Notes

In recent years, the promises of ultrawideband (UWB) technology have sparked the interest of the research community, and since 2002, when the Federal Communications Commission (FCC) approved the commercial use of the frequency band between 3.1 GHz and 10.6 GHz for UWB systems, research in this field has gained momentum. The first years after the FCC's release have seen an almost exponential increase in publications on this topic, as is shown in Figure 1.

Coherence-Free High-Resolution RF/Microwave Photonic Bandpass Filter With High Skirt Selectivity and High Stopband Attenuation

A new coherence-free high-resolution RF/microwave photonic bandpass filter with high skirt selectivity and high stopband attenuation is presented. It is based on a frequency shifting amplified recirculating delay line loop with a wavelength dependent element at the output. The amplitudes of the delayed optical signals at the output of the frequency shifting loop are windowed by a wavelength dependent element to improve the signal processor frequency response performance. The frequency shifting amplified recirculating delay line enables a large number of taps to be generated using a simple structure for high-resolution signal processing. It has no coherent interference and phase-induced intensity noise limitations, and can be inserted into conventional fibre optic links. Experimental results demonstrate a high-resolution bandpass filter having a high performance with a shape factor of only 3.1 and an extremely high stopband attenuation of over 70 dB.

Design of planar bandpass filters from tapered slot resonators

AbstractA compact planar bandpass filter is designed using a tapered slot resonator, which is formed using two tapered slot antennas connected in a face‐to‐face configuration. The tapering profile and dimensions of the resonator control the characteristics of the filter. The success of the method is demonstrated via full wave electromagnetic simulations and measurements. Passbands of 30–50% centred at about 6 GHz with an insertion loss of less than 1 dB and a peak‐to‐peak group delay of less than 0.5 ns are achieved in two filters having different tapering profiles and fabricated on RT6010 substrate with an overall dimension of 25 mm × 30 mm. The use of an open‐ended series stub within the coplanar waveguide feeder of the filters extends their high stopband beyond 15 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1190–1194, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25118

A Design Method for Variable Linear-Phase FIR Filters with Changing Multifactors for Checkweighers

Digital signal processing requires digital filters with variable frequency characteristics. A variable digital filter (VDF) is a filter whose frequency characteristics can be easily and instantaneously changed. In this paper, we present a design method for variable linear-phase finite impulse response (FIR) filters with multiple variable factors and a reduction method for the number of polynomial coefficients. The obtained filter has a high piecewise attenuation in the stopband. The stopband edge and the position and magnitude of the high piecewise stopband attenuation can be varied by changing some parameters. Variable parameters are normalized in this paper. An optimization methodology known as semidefinite programming (SDP) is used to design the filter. In addition, we present that the proposed VDF can be implemented using the Farrow structure, which suitable for real time signal processing. The usefulness of the proposed filter is demonstrated through examples.

Substrate integrated waveguide negative-order resonances and their applications

A family of substrate integrated waveguide (SIW) negative-order resonances and their applications to miniaturised antennas and filters are investigated and presented. These metamaterial resonators are realised by etching the interdigital slot on the surface of SIW with varied boundary conditions. The slot acts as a series capacitor along with the waveguide inherent shunt inductor achieving a composite right/left-handed functionality. These resonances are generated below the characteristic waveguide cut-off frequency and are independent of the dominant TE10 mode. The properties of these different resonances, which are characterised by half-wavelength or quarter-wavelength resonances, are discussed and compared. According to their characteristics, different applications are investigated. First, miniaturised waveguide slot antennas based on the first-order resonance are discussed. These antennas provide relatively high radiation efficiency and regular radiation patterns while keeping a low profile. Secondly, compact waveguide filters are proposed and presented. The simulated and measured results for these filters are provided. These metamaterial filters are showing advantages in terms of low-profile, high stopband rejection, easy fabrication and integration with other circuits.

An improved asymmetric defected ground structure cell and its application to lowpass filter

AbstractAn improved asymmetric defected ground structure cell is presented and analyzed. Based on this structure, a microstrip lowpass filter with low passband loss and high stopband suppression is designed and fabricated. Measured passband losses are below 1 dB, and a sharp slop is obtained at passband frequency fringe. The suppression is no <30 dB in stopband from 2.98 to 10 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2933–2935, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24778

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.

Novel dual mode microstrip bandpass-filter [Technical Committee

A novel four-pole, dual-mode bandpass filter is presented. It is based on microstrip meandered ring resonators, where dual-mode resonances are utilized through well-placed discontinuities in the symmetry plane of the ring structure. These filter types show very compact size, low insertion loss, and high stopband attenuation as well as steep filter slopes. The investigation was carried out within the student paper contest "Packaged X-Band Filter" at IMS 2008. Therefore, the passband is defined between 7.145--7.235 GHz, while the insertion loss is less than 5 dB and the return loss exceeds 15 dB. Between 8.4--8.5 GHz, the stopband attenuation should exceed 45 dB. This article presents the filter construction and simulation results. The integration into the given package as well as measurement results are presented.

Tunable photonic bandpass filter with high-frequency response performance

A continuously tunable RF/microwave photonic bandpass filter that simultaneously achieves high skirt selectivity and high stopband attenuation is presented. It is based on controlling the signal polarisation state in a reflective amplified recirculating delay line loop with a polariser at the output. A technique to overcome the phase noise limitation in the structure is also presented. Experimental results demonstrate continuous tuning of the high-performance photonic bandpass filter and a continuously tunable photonic bandpass filter with a low-noise performance.

A compact quasi‐elliptic bandpass filter using coupled dual quasi‐lumped LC resonators

AbstractThis letter proposes a compact microstrip bandpass filter using coupled dual quasi‐lumped LC resonators. With the proposed topology, two transmission zeros are generated at both low and high stopband near the passband to create quasi‐elliptic response. A filter sample is designed and fabricated to provide an experimental verification. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 158–160, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24009

Double Coupler Amplified Recirculating Delay Line Microwave Photonic Bandpass Filter

Theoretical and experimental investigations on a double coupler amplified recirculating delay line (ARDL) microwave photonic bandpass filter are presented. These show that the system involves both coherent and incoherent summation of optical signals. This enables a higher order filter transfer function to be realized, which results in a high-performance frequency response that cannot be achieved by the conventional single coupler ARDL structure. Experimental results are presented that demonstrate a sharp, high skirt selectivity and high stopband rejection level bandpass filter response.

First-order PMD compensation using optical FIR filter

We present a synthesis algorithm to design an optical finite impulse response (FIR) filter for compensating a first-order polarization mode dispersion (PMD) by minimizing the differential group delay (DGD). The desired frequency response was approximated using two widely used methods in designing digital FIR filters: the Fourier series expansion method and the frequency sampling method. A numerical simulation was performed for an eighth-order filter to demonstrate the difference between the two methods. The simulation results produced a sharper cutoff for the Fourier series expansion and higher stopband attenuation for the frequency sampling method. The Fourier series method produced better results in reducing the DGD.

A novel microstrip slow‐wave resonator band‐pass filter for millimeter wave applications

AbstractMicrostrip line is characterized by many advantages such as easy fabrication, compact size, lightweight, planar structure, and easy integration with other components on a single circuit board. In this article, a novel microstrip millimeter wave band‐pass filter with slow‐wave resonator is presented. By introducing cross‐coupling capacitance between the input and output ports of the filter, a slow‐wave resonator is suggested to improve both selectivity and stopband rejection. The proposed microstrip filter also has the merits of compact size and high stopband rejection. The experimental results on a fabricated filter agree with the simulated results very well. It might be widely used in plane circuits and advanced circuits such as MMIC and LTCC. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1720–1722, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23484

Coplanar waveguide metamaterials: The role of bandwidth modifying slots

The authors propose a coplanar waveguide stopband metasurface based on the Babinet principle. The resulting layout is a compact planar metal structure with complementary split ring resonators, which exhibits a high rejection stop band. The complementary rings provide a frequency band with an effective negative dielectric permittivity. Moreover, the rejected bandwidth can be expanded by introducing slots close to the rings. The authors provide a simple physical model which explains the impact of the slots. Simulations confirm the expected behavior and are in excellent agreement with the measurements.

Design of the Compact Parallel Coupled Wideband Bandpass Filter With Very High Selectivity and Wide Stopband

In this letter, a compact and high performance parallel coupled line wideband bandpass filter (PCL-WBF) with open stubs is designed and implemented on the commercial substrate, RT/Duroid 5880. The PCL-WBF is composed of a one-stage coupled line and two open stubs connected near the input/output ports. The design procedure and limit are discussed in detail. The designed filter was fabricated and measured, showing good characteristics of wide stopband and very high passband selectivity. Measured results also have a good agreement with the simulated results.

Reflective Amplified Recirculating Delay Line Bandpass Filter

A new microwave photonic filter structure that can achieve a high factor, high stopband rejection, and high skirt selectivity bandpass filter response simultaneously is presented. It is based on reflecting the signal back into a single amplified optical recirculating delay line and comprises coherent summation of the multiple signals that constitute each tap and incoherent summation of the successive taps. This introduces a new class of filter operation and effectively enables the realization of a higher order bandpass filter characteristic in a very simple structure. Experimental results are presented that demonstrate a multiple-tap high- bandpass filter response that also displays high stopband rejection level and high skirt selectivity.

Compact wide stopband low‐pass filter using rectangular patch compact microstrip resonant cell and defected ground structure

AbstractA new compact microstrip low‐pass filter (LPF) is presented using a novel rectangular patch compact microstrip resonant cell (RPCMRC) and square‐head defected ground structure (DGS). It exhibits wide, high stopband, and sharp rejection. A demonstration LPF having 3 dB cutoff frequency of 2.65 GHz was fabricated and measured. Measured rejection is better than 20 dB from 2.8 to 16 GHz. Electrical length of the filter is less than 20% of the guided wavelength at 3 dB cutoff frequency. Measured passband to stopband attenuation slope is more than 56 dB/GHz. Good match between experimental and simulated results are obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 798–800, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22259