High isolation dual-polarized patch antenna using integrated defected ground structure

A comparative study to determine the most highly sensitive resonant frequency among the first four resonant frequencies of a conventional patch antenna and defected ground structure (DGS)-loaded patch antennas using commonly used DGS geometries in the literature, such as a rectangular slit, single-ring complementary split ring resonators (CSRRs) with different split positions, and double-ring CSRRs (DR-CSRRs) with different locations below the patch, for relative permittivity measurement of planar materials was conducted. The sensitivity performance for placing the DGS on two different locations, a center and a radiating edge of the patch, was also compared. Finally, the effect of scaling down the patch size of the DGS-loaded patch antenna was investigated in order to enhance the sensitivities of the higher order resonant frequencies. It was found that the second resonant frequency of the DR-CSRR DGS-loaded patch antenna aligned on a radiating edge with a half scaled-down patch size shows the highest sensitivity when varying the relative permittivity of the material under test from 1 to 10. In order to validate the simulated performance of the proposed antenna, the conventional and the proposed patch antennas were fabricated on 0.76-mm-thick RF-35 substrate, and they were used to measure their sensitivity when several standard dielectric substrate samples with dielectric constants ranging from 2.17 to 10.2 were loaded. The measured sensitivity of the second resonant frequency for the proposed DGS-loaded patch antenna was 4.91 to 7.72 times higher than the first resonant frequency of the conventional patch antenna, and the measured performance is also slightly better compared to the patch antenna loaded with a meander-line slot on the patch.

A new planar 10 dB loose branch line coupler is proposed for application to the 2.5 GHz centre frequency. This proposed coupler is implemented with rectangular ring headed dumbbell shaped Defect Ground Structure (DGS) along with conventional microstrip transmission line. Design of this conventional branch line coupler with DGS provides more design flexibility. Using the DGS, increases the electrical length of microstrip line, provides slow wave characteristics and increases the impedance of the microstrip line. In this paper one required high impedance microstrip line is implemented easily using proposed DGS structure. Finally, the compact microstrip 10 dB loose coupler is designed.

Microstrip patch antenna is widely presented based on its advantages, especially for WiMAX wireless applications. Although, reducing the antenna size is a distinguished topic of antenna development, the antenna performance significantly drops for a small antenna. In this paper, two slots on a compact square ring and defected ground structure (DGS) are presented for bandwidth enhancement and radiation efficiency at 5.5 GHz. When the DGS and slots are embedded in the structure of the designed antenna, two major improvements are achieved. Enhanced impedance bandwidths with |S11|< −10 dB range from 5.041 to 5.88 GHz (15.25%) and the radiation efficiency of 80.8% by loading DGS over conventional patch antenna are achieved. Both antennas with/without DGS achieve good far-field radiation patterns within the operating frequency band at 5.5 GHz. CST microwave studio is used for simulating the design. The physical antenna layout is printed on FR4 substrate. The proposed configuration has a miniaturized size of 25 × 25 mm2. The fabricated antenna is tested to validate the proposed design. Thus results obtained from simulations and measurements show good agreement. The proposed prototype can be considered a suitable candidate for WiMAX wireless applications.

Propagation characteristics, including scattering, dispersion, and loss modeling, of some microstrip lines (MTLs) with defected ground structure (DGS) slots were investigated in this paper. A simple approach was firstly introduced to calculate the slow-wave factors (SWF) of these MTLs with DGS. Based on the above-mentioned theory, a meander MTL structure with periodic DGS slots was proposed and analyzed. The improved SWF and characteristic impedances have been demonstrated, while the bandgap performances have been proved by experimental results. Further, a type of nonuniform DGS slots, which are composed of dual-periodic photonic bandgap structures, was applied to reduce the second-order harmonics and improve the output power of a Ku-band voltage-controlled oscillator. Measurements showed that the second-order harmonics are suppressed by more than - 20 dB and the output power is improved by 3–5%.

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.

Abstract. A compact (0.16  g × 0.08  g ) and wide stop-band lowpass filter design using open complementary split ring resonator (OCSRR) and defected ground structure (DGS) is presented in this paper. Low pass filter is con-structed using two cascaded stages of OCSRR. Since the rejection bandwidth of the OCSRR is narrow, tapered dumbbell shaped DGS section is placed under the OCSRR to enhance the bandwidth. The cutoff frequency (f c ) of the proposed lowpass filter is 1.09 GHz. The rejection band-width of the filter covers the entire ultra wideband spec-trum. Hence the spurious passband suppression is achieved up to 10 f c . The designed filter has been fabri-cated and validated by experimental results. Keywords Lowpass filter, defected ground structure (DGS), open complementary split ring resonator (OCSRR) 1. Introduction On the motive of conventional filter design methods such as stepped impedance and open stub suffering from poor skirt characteristics and spurious passband, re-searchers have paid great attention over the past few years in designing a compact and sharp cutoff lowpass filters with spurious free wide stopband. Lowpass filter using different defected ground structures (DGS), photonic bandgap (PBG) structures and electromagnetic bandgap structures have been proposed in various literatures [1–9]. Sharp cutoff and low insertion loss lowpass filter using a complementary split ring resonator (CSRR) is reported in [3]. Cascaded stages of CSRR with open stub configura-tion, exhibiting sharp cutoff lowpass response are pre-sented in [4]. Planar photonic bandgap (PBG) structures involving compact microstrip resonating cell (CMCR) are utilized to design a lowpass filter with wide stopband [5]. Recently, a lowpass filter with very sharp transition band using OCSRR is demonstrated in [6]. In this paper, a new technique is proposed to reduce the size of the lowpass filter and to obtain the wide spurious free stopband. The lowpass filter is designed using open complementary split ring resonator and a tapered dumbbell shaped DGS is placed under the OCSRRs to extend the stopband. The proposed lowpass filter is smaller and outperforming the existing filters in terms of insertion loss level, roll off rate and rejection bandwidth. Figure 1 shows the schematic of OCSRR printed on the microstrip line. This structure is first proposed in [6] for designing a sharp cutoff lowpass filter with compact size. OCSRR is a negative image of the open split ring resonator. To study the frequency response characteristics of the OCSRR, this structure is designed on Rogers 5880 substrate with a dielectric constant of 2.2 and a substrate thickness of 0.381 mm and simulated using an Ansys full wave simulator.

Introduction of Defected Ground Structure (DGS) into Microstrip Phased Array Antenna (MPAA) brings significant changes to bearing of major beam. In this paper, realization on evolution of 2 × 1 rectangular patches which resonates at 9.07 GHz is discussed. The two rectangular patches are separated at 0.3962λ and the microstrip line is fed to the middle of patches to improve impedance matching. Afterwards, an orthogonal-I-shaped DGS (OI-DGS) is incorporated in between the two patches at ground plane. It is found that by modifying the dimensions of the OI-DGS, main lobe of the MPAA decreases from 15° to −35° while directivity of the arrays maintains at about 9.04 dBi. Therefore, it could be better to utilize DGS to steer main beam of MPAA rather than employing additional phase shifters, which is massive and more sophisticated to connect to the antenna's feeding lines.

Defected ground structure (DGS)-integrated arc-cornered rectangular microstrip antenna (RMA) has been investigated to achieve broadband along with high co-polarized to cross-polarized radiation (CP–XP) isolation over principal as well as over skew planes without affecting the dominant mode co-polarized (CP) radiation pattern. The present arc-cornered RMA on circular and rectangular dot-type DGS is thoroughly studied and compared with the conventional rectangular microstrip antenna. In the present paper, a crucial emphasis is given to improve CP–XP isolation in all the skew planes and by employing circular dot-type DGS around 20 dB CP–XP isolation is achieved over whole skew planes as well as in the H-plane with the proposed structure with 20% impedance bandwidth. On the contrary, the CP–XP isolation and impedance bandwidth vary in opposite manner in case of the rectangular dot-type DGS. Around 25 and 10 dB CP–XP isolation with 9 and 22% impedance bandwidth have been obtained with thin and thick rectangular dot-type DGS, respectively. The corners of the patch surface are rounded in such a way to reduce spurious radiations from the sharp corners, which are generally attributed for high XP radiation along the diagonal directions.

Over last few decades, wireless communication system has sought more attention and plays predominant role in different areas for human personal and commercial applications. Day by day, with advancements in technology, wireless gadgets got more compact due to microelectronics fabrication and integration techniques. So, such applications put great demand over new design specifications on antenna structures used in transmitter and receiver for radio wave communication. In wireless applications depending upon, frequency bands and bandwidth requirements numerous compact antenna structures are used with improved efficiency. Microstrip patch antennas are highly regarded due to its compact size, easy integration with microwave circuits. In study of patch antenna, Defected Ground structures gain popularity these days due to its various benefits to enhance antenna performance. This research article, provides extensive literature survey over use of Defected Ground Structures (DGS) in microstrip patch antenna with its design consequences. This article also explores the enhancement in antenna parameters with implementation of DGS’s. DGS concept is used in microstrip patch antenna and microwave engineering for performance improvement of these devices. DGS can be merged with other techniques to enhance antenna operational parameters like gain, bandwidth, VSWR and spurious radiations.

A microstrip patch antenna using a defected ground structure (DGS) to suppress higher order harmonics is presented. An H-shaped defect on the ground plane with only one or more unit lattices has been utilized and yielded bandstop characteristics. Compared with a conventional microstrip patch antenna without the DGS unit cell, the radiated power of the DGS patch antenna at harmonic frequencies has been drastically decreased.

The design and analysis of an ultra-wideband with high isolation characteristics, utilizing a modified bowtie antenna and coplanar waveguide feeding technique is presented in this paper. Grooves are added to the ground plane's entire structure to reduce the capacitive coupling between the patch and the ground plane. The grooves in the ground plane enhance the impedance matching and radiation efficiency across the ultrawideband frequency range. Also, defected ground structures (DGS) are used to improve isolation between the two antennas. It is novel and different in that it uses defective ground structures (DGS) to provide high isolation (−<50dB) with a high gain of 6.5 dBi and a large impedance bandwidth (155%). Compared to other documented methods, the antenna's design step is very simple, the overall size is small, larger bandwidth (13.5 GHz) and achieves high isolation due to DGS.

This paper presents the effects of defected ground structure (DGS) on different ground planes in RF power amplifiers (PAs). Two DGS patterns etched on the front and back planes of printed circuit board which are named Top-DGS and Bottom-DGS, and a thru microstrip line are manufactured and measured to compare the insert loss at the fundamental and second harmonic frequencies. In order to evaluate the effects of the Top-DGS, Bottom-DGS and without DGS on the PA, three 4W PA have been designed and measured. Measured results show that the PA with the Top-DGS can reject the second harmonic about 13dB at Pout 34.76dBm, and achieve better the output power (Pout) and power added efficiency (PAE) than the one without DGS; the one with the Bottom-DGS has the suppression of about 28dB for the second harmonic at Pout 34.21dBm, and has less the Pout and PAE for the decreased characteristic impedance (Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> ) of DGS pattern.

A fast and direct method to estimate the stopband in microstrip lines with periodic defected ground structures (DGS) is introduced in this paper. Based on the equivalent circuit of single DGS unit, an approximate relationship between the stopband and DGS circuit dimensions is set up. Comparison between the estimated results and simulated results based on field analysis methods verifies the validity of the proposed method.

Calculation and differentiation of the response of elliptical low pass filter (LPF) with and without using defected ground structure (DGS) was done. In the present work, return loss, bandwidth and gain have been evaluated. All the designs are printed on the FR4 lossy substrate of dielectric constant ( ) of 4.3, substrate thickness of 1.6 mm and loss tangent of 0.02. Moreover, the effect of controlling parameters namely slots and defected ground structure are also analysed. The proposed DGS cell provides low-pass characteristic whose cutoff frequency could be changed by tuning its dimensions. Results are simulated using computer simulation technology software (CST). In this paper, the low pass filter passes the low frequency at a cut off frequency of 5 GHz. This filter operates up to 5 GHz frequency. The proposed planar microstrip filter has been selected because of its simple structure, cost effective components and excellent performance. Microstrip filter technologies are emerging as an innovative way to meet the growing demand for more powerful, cost-effective and highly efficient wireless communication systems.

This chapter presents the study of performance parameters of stub loaded oval-shaped patch antenna using dumbbell-shaped metamaterials (MTM), electromagnetic bandgap structures (EBG), and defective ground structures. Metamaterials are loaded inside the substrate that is mounted on the partial ground plane. EBG and DGS structures utilize full ground planes. The partial ground plane has the dimensions of 10 × 6 × 0.035 mm3 and the full ground plane has the dimensions of 10 × 12 × 0.035 mm3. Many features like impedance bandwidth, gain, axial ratio, and miniaturization of the proposed patch antenna are studied using metamaterials, electromagnetic bandgap structures (EBG), and defective ground structures. The appropriate structure will be chosen depending on the wireless application. Metamaterial loaded patch antenna is recommended for wide bandwidth applications, patch antenna mounted the EBG ground is recommended for small antenna applications, and patch mounted on the DGS ground is recommended for high gain applications.