Harmonic-Rejection Compact Bandpass Filter Using Defected Ground Structure for GPS Application

This paper introduces folded DGS resonators to be used as building blocks of two-band band-pass filter. The transmission line with defected ground structure (DGS) can increase the equivalent capacitance and inductance of the transmission line and the dielectric constant. This character is useful for the design of miniaturization filter. The folded DGS resonator is then applied to design a multilayer second-order coupled resonator band-pass filter and a second-order two-band band-pass filter. The simulation results are presented to show the performance of these filters. It is easy to change the work frequency by adjusting the length of folded line and the thickness of resonator. External Quality Factor is connected with the length of feed line. It is significant for the research of the multi-frequency DGS filter.

A novel defected ground structure (DGS) microstrip resonator is proposed. The proposed DGS resonator has the resonant and anti-resonant characteristic that is very similar to those of a surface acoustic wave resonator or a film bulk acoustic resonator (FBAR). To confirm the validity of the proposed resonator, bandpass filters were designed and implemented using series and parallel resonators.

This paper presents a novel ultra wideband (UWB) bandpass filter (BPF) with a notch-band at specified frequency. Moreover, its equivalent circuit model (ECM) is also investigated. The proposed filter consists of a stepped impedance resonator (SIR), a parallel coupled feed line on the top and a rectangular shaped defected ground structure (DGS) on the bottom of the structure. The notch band can be shifted to any other desired frequency by tuning the length of the parallel coupled feed line. Good performances in terms of wide stop-band rejection, low insertion loss, high return loss and more compact size (7.99 × 6 mm2) than those reported in literature are achieved. In addition, simulation results accomplished by ECM are in good agreement with the full-wave EM.

In this paper, we design and implement a coplanar waveguide (CPW) bandpass filter utilizing defected ground structure (DGS) technology. The CPW DGS technology, which only needs one or a series connection of a few cells to exhibit the bandgap characteristics, can provide the attenuation poles in the upper and lower bands to improve the rolloff characteristics of the bandpass filter. Moreover, the equivalent lump values of the CPW DGS are also calculated and good agreement between EM simulation and numerical calculation is obtained. The measured results show that the improved selectivity of upper and lower bands are 10.7 and 46.5 dB/GHz, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 331–334, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20294

High frequency rejection using L shaped defected microstrip structure in ultra wideband bandpass filter

Low Pass (LP) and Band Pass (BP) filters using stepped impedance resonator (SIR) utilizing band-reject behavior of defected ground structure (DGS) for wireless applications are proposed. These new configurations of DGS filters are fabricated on both isotropic and anisotropic substrates. Improvement in cut-off characteristics for both LP filter and BP filter, and fractional bandwidth improvement of BP filter using anisotropic substrate over isotropic substrate are reported. A size reduction of up to 67.7 % using the DGS configuration over the conventional three-pole SIRBPF is achieved.

In this paper an ultra wideband microstrip Bandpass filter is proposed using stepped impedance resonators (SIR) and defected ground structures (DGS). This band-pass filter is designed to operate within the Ultra Wide Band frequency range from 4.0 GHz to 11.0 GHz with 7.0 GHZ bandwidth and centre frequency at 7.5 GHz. This prototype filter is designed on RT/Duroid 5880 substrate of thickness 0.787mm with dielectric constant 2.2. The filter is simulated and optimized using Zealand IE3D simulation software v14.0. The passband of the filter has five transmission poles. Insertion loss within the passband is better than -1.5dB and the return loss is kept less than -20dB and a total fractional bandwidth of 93.33% is obtained. The prototype built can be used in UWB communications or localization systems.

In this letter, a novel tri‐band bandpass filter (BPF) with high selectivity is presented. The proposed tri‐band BPF employs a symmetrical π‐type structure loaded with λ/4 open stubs and hybrid stepped impedance resonator (SIR). The hybrid SIR consists of two‐section cascaded SIR and a pair of parallel‐coupled lines. Using λ/4 frequency‐selected open stubs, the complete π‐type structure is restructured into a basic π‐type structure with three microstrip lines. The filtering responses of the second passband are controlled only by the basic π‐type structure. The filtering responses of the first and third passbands are influenced by the complete π‐type structure. By embedding coupled‐lines into the two‐section cascaded SIR, four extra transmission zeros (TZs) are obtained. For validation, a tri‐band BPF with 3‐dB fractional bandwidths of 14.3%, 9.4%, and 6.6%, respectively, operating at 1.77 GHz (GSM), 2.37 GHz (WLAN), and 3.43 GHz (WiMAX) is simulated, fabricated, and measured. The measured insertion losses are less than 1.5 dB and return losses are better than 24.5 dB within three passbands. In total, seven TZs are generated and the maximum roll‐off rate of three passbands is up to 173 dB/GHz. The good agreement between simulations and measurements verifies the proposed design.

This paper presents a novel connecting-line coupling technique for the design of compact and low-loss bandpass filters (BPFs) with multiple controllable transmission zeros (TZs). Traditional gap-coupling methods are highly sensitive to fabrication errors and have limited design flexibility. By contrast, the proposed approach enables precise control of coupling strength without modifying resonator geometry. Such control is achieved through independent adjustments of the lengths, widths, and positions of connecting lines. Furthermore, the proposed approach facilitates the generation of up to n TZs for an nth-order BPF, thus considerably improving the BPF’s frequency selectivity and stopband attenuation. To validate the effectiveness of this method, four filters are designed and fabricated: a second-order stripline BPF, a fourth-order microstrip BPF, a fifth-order stripline BPF, and a sixth-order wideband microstrip BPF. The second-order BPF is based on asymmetric connecting-line coupling, whereas the fourth-, fifth-, and sixth-order BPFs are based on symmetric connecting-line coupling. Excellent agreement between simulation and measurement results is achieved for these designs, with low insertion loss, high roll-off rates, and high tolerance to fabrication variations being noted. The proposed technique is suitable for filters ranging from narrowband to ultra-wideband filters and across low to millimeter-wave frequency bands, making it a highly versatile and practical solution for modern RF and microwave communication systems.

This paper addresses DGS based inductively coupled bandpass filters fabricated on Coplanar Waveguide (CPW) technology. The addition of the DGS to the conventional inductively coupled resonator BPF allows the miniaturization of the resonator by exploiting the transversal dimensions of the CPW, while maintaining its performance with respect to insertion and return loss values. On the other hand, the DGS cell allows reconfiguration of the structure from a single band to a multiband BPF. The design procedure of the filters with the DGS is explained with filters designed at 5 GHz. Simulated and measured results show good agreement.

A novel 22-GHz-band oscillator using an integrated defected ground structure (DGS) resonator is presented for quasi-millimeter waveband applications. The DGS is etched on the first metal layer (M1) below a 50- $\Omega $ microstrip line on the top metal layer (M6) of 0.18- $\mu \text{m}$ one-poly six-metal (1P6M) complementary metal-oxide-semiconductor (CMOS) technology. The proposed oscillator is fabricated using 0.18- $\mu \text{m}$ CMOS technology, and the measured carrier frequency and phase noise are 22.88 GHz and −129.21 dBc/Hz (−108.05 dBc/Hz) at 10-MHz (1 MHz) offset frequency, respectively. The power dissipation is 6 mW that results in a figure of merit to be −188.8 dB. As the DGS resonator could be designed at any high frequency, it may give an alternative design approach of high performance voltage controlled oscillator and frequency synthesizers at K-band and beyond, thus alleviates the problem of self-resonance that a spiral inductor usually encounters at higher frequency.

ABSTRACTIn this article, a novel dual‐band bandpass filter using composite right/left handed (CRLH) triangle mushroom structure and defected ground structure (DGS) is proposed. The proposed filter uses triangle mushroom structure as the CRLH transmission line to achieve low‐in‐band insertion loss and compact size, and DGS to achieve out‐band rejection. Simulation and measurement results are in good agreement and the good properties mentioned above have been verified. It is proved that CRLH triangle mushroom structure and DGS can be both used to reduce the size of the filter and increase the rejection between the passbands in multipassband filter applications for the first time. This new combination of the two different structures has succeeded in achieving excellent performance. This novel filter can be applied in the microwave circuits and wireless communication systems. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2756–2759, 2013

An asymmetric defected ground structure (DGS) with respect to a microstrip line is proposed. Its unit cell consists of two square slots connected with a rectangular slot by meandered transverse slots. The simulated, measured and equivalent circuit responses have been presented. The unit DGS pattern under microstrip line produces wide rejection bandwidth and high sharpness factor. Its elliptic band-reject filter response is modelled by appropriate LC equivalent circuit. Two such DGS cells under a microstrip line produce 3-pole quasi-elliptic bandstop filter response, which shows deeper attenuation without appreciable change in pole frequencies in comparison to single cell structure. Unit DGS pattern under coupled gap microstrip lines produces band-accept filtering characteristics. The frequency characteristics show a quasi-elliptic highpass filtering characteristics with sharp lower transition knee. Accordingly, an LC equivalent circuit is proposed. A cascaded band-accept and band-reject filter is proposed for designing a wideband bandpass filter. The bandwidth and centre frequency of the bandpass filter can be varied by choosing different set of DGS dimensions.

In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results.

Analysis and realization of a microstrip-based planar ultra-wideband (UWB) filter with integrated multiple notch elimination property and simultaneously extended upper stopband is proposed. Initially, a UWB filter based on back-to-back microstrip-to-CPW technology is designed. Later, multiple spiral defected ground structures (DGS) are embedded to obtain multiple passband notches. Further, double equilateral U (DEU)-type DGS are used to improve upon the rejection level in upper stopband. The multiple passband notches are results of embedded spiral-shaped DGS (SDGS), while extended upper stopband is the outcome of suppressed higher-order spurious harmonics. The flexible dual-attenuation poles of DEU-shaped DGS suppress the stopband harmonics and widen the stopband. An approximate lumped equivalent circuit model of the proposed filter is modelled. The filter is compact and its layout measures 25.26 mm × 11.01 mm. The measured result is in good agreement with the full-wave electromagnetic (EM) simulation and circuit simulation.