Defected Ground Structure Filter Research Articles

Miniaturized low‐pass filter based on defected ground structure and compensated microstrip line

AbstractThis article presents a low‐pass filter combining asymmetric π‐type defect structure and microstrip line filter. Traditional single‐form defected ground structure filters often require cascading to have good suppression, which can result in increasing board size and cost. The top layer of the proposed filter is in the form of a stepped impedance microstrip line, and the bottom layer uses a defective structure. Simulation and experimental results show that the filter combining the new defect structure and the microstrip line has a very sharp transition zone and deeper suppression depth than the existing symmetrical or asymmetric defect structure. The proposed structure has an ultracompact size of 356 mm2, and the results show an insertion loss from 0 to 2.2 GHz as low as 0.8 dB and a wide stop band of more than 30 dB from 3.3 to 9.8 GHz.

System‐based modelling and synthesis of defected ground structure resonators and filters

This paper describes a method for the system modelling and synthesis of defected ground structure (DGS) resonators based on the singularity expansion method (SEM). The analytical expressions of the transfer functions for three types (dumbbell-shaped, C-shaped and meander-shaped) of DGS resonators are formulated. The physical poles of the DGS structures are extracted utilising a pole-energy-based matrix pencil (MP) scheme. Afterwards, the transfer function expressions are utilised to develop an accurate equivalent lumped-element circuit for the three types of DGS resonators. A systematic synthesis method using the generalised transfer function of the resonators is proposed to design a meander-shaped DGS dual-bandpass filter. Good agreement is observed between the transfer function model of the system and the computed frequency domain data of the synthesised DGS filter. The developed procedures of system-based modelling and synthesis are general and can be used systematically to synthesise multipart DGS filter structures.

Model-Driven Design of Microwave Filters Based on Scalable Circuit Models

Most microwave filters are currently designed using direct electromagnetic (EM) optimization. This method holds several disadvantages regarding the provided physical insight to designers and duration of the optimization process. To circumvent these drawbacks, we propose a filter design based on scalable circuit models. This model-driven design competes with EM optimization by maintaining the accuracy of the optimization results while providing a very significant speedup and gaining physical insight on the EM working mechanism of the filter of interest. This paper discusses the advantages of using the proposed model-driven design by the illustration on a defected ground structure filter. A scalable equivalent circuit model is used in the design procedure to provide physical insight to the designer and to speed up the design process enormously.

Co-designed defected ground structure filter with UWB slot antenna

Co-designed defected ground structure filter with UWB slot antenna

A Robust Parameter Design of Wide Band DGS Filter for Common-Mode Noise Mitigation in High-Speed Electronics

A defected ground structure (DGS), working as common-mode noise filter, is developed for high-speed electronic circuits. However, due to deviations of parameters inevitably exiting in the process and materials, the performance of the filter may shift and deteriorate even if the design is optimized. Therefore, a robust design method is proposed by using design of experiment and Taguchi method. Recognizing the deviations as uncontrollable factors and categorizing the prevailing and nonprevailing design parameters in the study, the filtering performance of common-mode DGS filter is not only optimized effectively with a wider stop band of 7.926 GHz but also highly resistive to the variations of design parameters.

Wideband bandstop defected ground structure filter with enhanced common-mode suppression using split ring

An effective method to broaden the rejection bandwidth of dump-shaped defected ground structure (DGS) filter design is proposed in the paper. One traditional dumbbell-shaped DGS is split by using one split ring, and reconstructed into two different compact DGSs. The distance between both of the DGSs is so close that there exists mutual inductance, which can be utilized to broaden the rejection bandwidth effectively. The effect of different parameters of the split ring on the rejection bandwidth and depth of the filter is analyzed. Simulated results demonstrate that, with the same area of 5.5mm by 10 mm, rejection bandwidth of the proposed filter is from 4.4 GHz to 10.5 GHz for the common-mode noise (CM) while that of the traditional dumbbell-shaped DGS is from 5.3 GHz to 7.3 GHz. Compared to other schematics adopting multiple DGS to broaden bandwidth, it can broaden the bandwidth by dividing the existed DGS into multiple parts and reconstructing a new filter. The experimental results show good agreement with simulated results.

A broad stopband common-mode suppression defected ground structure filter with complementary structure

A low-cost defected ground structure (DGS) wideband stopband filter adopting complementary structure is proposed, which is designed for common-mode noise suppression in high-speed differential signals. The filter is etched below the low cost FR4 printed circuit board. To avoid stimulating the common-mode noise, the DGS cells on ground planes are kept symmetrical to the central line of the two differential signal lines. Both sides of the filter adopt a symmetric cup-shape DGS structure and the middle of the filter adopts a symmetric umbrella-type structure. All of the DGS structures are complementary, which makes the filter compact and miniaturized. What is more, because the spaces among the three DGS are closer, there exist the mutual inductances among them, which are utilized to achieve a wide stopband filter. The simulated result demonstrates the proposed filter has a wideband bandwidth of 6.8 GHz over 20 dB. In order to analyze the effect of compact structure of the filter, a filter having the same DGS patterns but large spaces among them is compared with it. The simulated result demonstrates that the stopband bandwidth of the compared filter has a wideband bandwidth of 4.4 GHz over 20 dB, of which the bandwidth is about 2.4 GHz less than that of the proposed filter. It is obvious that there exists a mutual inductance in the compact DGS structure common-mode filter, which plays an important role in broadening the bandwidth of the proposed filter. In order to facilitate analysis, an equivalent model of LC circuit is also given. The equivalent parameters of LC can be deduced from the definition of 3 dB cut-off frequency and resonant frequency, of which the values can be obtained by the HFSS simulation. The simulated and measured results show that the differential signal under the DGS filter is nearly intact, and the common-mode noise can be reduced over 20 dB from 4.6 GHz to 11.4 GHz and over 15 dB from 4.3 GHz to 12 GHz, while the area of the filter is only 10 mm by 10 mm. Compared with the periodic DGS at the same suppression depth of common-mode noise over 20 dB, the method has the advantages that surface area is reduced to no more than 30%, and the stopband width is increased by over 50%.

Design of a High-Power Superconducting Filter With Novel DGS Structures

A novel defected ground structure (DGS) resonator with improved power handling capability is proposed in this paper. The current density distribution of the DGS resonator is simulated and compared with that of the complete ground structure (CGS) resonator. Simulation shows that the maximum current density of the DGS resonator is lower than that of the CGS resonator. Two four-pole bandpass high-temperature superconducting filters centered at 2.9 GHz with a fractional bandwidth of nearly 1.5% are designed and fabricated using the DGS and CGS resonators, respectively. The measured maximum handling power is 37.3 dBm for the DGS filter at 77 K, which is higher than that of 34.1 dBm for the CGS filter.

A Novel Rectenna Design with DGS Filters for Low-Power Energy Transfer

A high efficiency rectifying antenna (rectenna) is designed at 5.8 GHz by using defected ground structure (DGS) filters for low-power energy transfer. A slot-coupled patch antenna is used as a receiving antenna with a high gain of 8.2dB. A DGS low-pass filter at the input port of the rectifying circuit is used to suppress the high order harmonics by 20dB. A DGS dc-pass filter is designed to block the AC signal from transmitting to the load. Both of the antenna and the filters are simulated by the full wave EM analysis software of HFSS. The RF-DC conversion efficiency of 51.8% is obtained when the received power is as low as 3mW.

Dual-band-stop filters with unsymmetrical T-shape DGS resonators

A kind of dual-band-stop filter with an unsymmetrical T-shape defected ground structure (DGS) is proposed. The filter has two band gap centers at 4.9 GHz and 7.35 GHz, respectively, where the two centre frequencies are just the second and third harmonics 2.45 GHz. The filters with high band-stop performance and wideband spurious suppression can be achieved by cascading miniaturized unsymmetrical T-shape DGS. The attenuation of three-cascaded T-shape DGS filter is 30.77 dB at 4.9 GHz and 17.96 dB at 7.35 GHz respectively. The above experimental results are in good agreement with the simulation results, especially for the third harmonic.

Lowpass filter with reduced fractal defected ground structure

Presented is the design of a planar lowpass filter with stubs separated by transmission lines. To minimise dimensions, the filter is completed by a fractal defected-ground structure (DGS). The fractal DGS filter requires a 20% smaller substrate compared to a conventional filter with stubs.

Novel Dual Band-Reject Microwave Filter Using C-Shaped Defected Ground Structures

In this paper, a new compact dual band-reject C-shaped defected ground structure (DGS) for microstrip line is introduced. Using two units of the same shaped DGS with different dimensions, a dual band-stop filter is designed and implemented. Results show that there are two parallel resonance frequencies at 2.468 GHz and 6.629 GHz with a very high Q-factor. The frequency characteristics of the proposed filter could be controlled by adjusting the DGS parameters such as width and length of both C-shaped patterns. Also, the distance between the two DGS structure could be adjusted for the required frequency characteristics. The proposed DGS provides Q-factor of more than 50 with attenuation of at least 20 dB at the resonant frequencies. The new introduced DGS filter is successfully designed and fabricated and the measured results are in a very good agreement with those obtained by numerical investigation.

Wide stopband compact microstrip lowpass filter using circular ring resonator and split ring resonators

In this contribution, a microstrip low-pass filter with a wide stop-band using split ring resonators and a circular ring resonator is introduced. The passband ripple of proposed filter was measured 0.6 dB and minimum insertion loss of passband is about 0.75 dB at 0.5 GHz frequency. Moreover, the 1.0 dB cut off frequency of proposed filter is 1.45 GHz in measurement. Designing this type of low-pass filter requires a high impedance transmission-line. However, the microstrip line width cannot be taken less than 0.2 mm in practical implementation. This causes to a small mismatch in passband. Furthermore, these results show wide stop-band up to 9.0 GHz with more than 30 dB rejection. The dimensions of proposed compact filter are about 12.5×30 mm2 (excluding extra substrate width). The proposed filter is a microstrip filter and can compete with defected ground structure (DGS) or defected microstrip structures lowpass filters in miniaturizing and wide stopband. However, the DGS or DGS filters have some problems in manufacturing applications such as radiation fields from defected structures and requiring a specific box. In addition, a distributed equivalent circuit model based on geometrical filer parameters is introduced, and good agreement can be seen between EM simulation and distributed equivalent circuit model up to 6.0 GHz frequency. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26203

Improvement of compactness of low pass and band pass filter using a simple combination of cross‐defected ground structure and a discontinuous microstrip line

AbstractThis article presents a method to reduce the size of LPF/BPF using defected ground structure (DGS). The DGS filter structure employs two cross‐slots etched in the ground plane. To validate the feasibility of the proposed design method, a low‐pass filter with 0.1‐dB ripple is designed, fabricated, and measured. Then a simple technique to transform the designed BPF to a LPF was presented. Additionally, a new suspended Layer's technique will be used with DGS in order to reduce more the size and to suppress the second harmonic in reject band. The second order band pass filter was designed using the proposed technique and their simulation results confirmed the validity of the technique. Simulated and measured results of the proposed filters are presented and show good agreements. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1191–1195, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24291

Microstrip parallel coupled‐line bandpass filter with selectivity improvement using U‐shaped defected ground structure

AbstractA novel defected ground structure (DGS) feedline element with two transmission zeros and flat passband is proposed. The zeros can be tuned individually by the DGS geometry to improve the low order filter's selectivity. A traditional microstrip parallel coupled‐line bandpass filter cascading this new element, not only achieves the selectivity improvement, but also its basic design formulation is retained. A prototype DGS filter was designed and tested to validate its performance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 911–915, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23236

Novel defected ground structure element with triple transmission zeros and its application for multispurious suppression of microstrip parallel‐coupled‐line bandpass filter

AbstractA novel compact defected ground structure (DGS) element with triple transmission zeros is proposed. The zeros can be tuned individually by the DGS geometry and the overall etched area is kept as compact as that of the conventional structure with single zero. The traditional microstrip parallel‐coupled‐line bandpass filter cascading this new element, not only achieves the multispurious suppression but also its basic design formulation is retained. A prototype DGS filter was designed and tested to validate its performance. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1409–1412, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22457

Compact quasi-elliptic function filter based on defected ground structure

A novel defected ground structure (DGS) is investigated for filter applications. With this structure, the basic resonant element exhibits the quasi-elliptic function responses. A new equivalent lumped L–C circuit model is presented and its corresponding L–C parameters are extracted by using parametric relationships, which has quasi-elliptic characteristics. The theoretical analysis for the effect of different design parameters has been carried out, which provides effective guidance in designing DGS. The performance of the new filter is also compared with the characteristic of the dumb-bell DGS filter to highlight the advantages of the proposed DGS. Based on the equivalent circuit model, a three-pole quasi-elliptic lowpass filter (LPF), using two DGS units cascaded, is optimally designed and implemented; experimental results show good agreement with theoretical ones.