8. F. Huang, Ultra-compact superconducting narrow-band filters using single- and twin-spiral resonators, IEEE Trans Microwave Theory Tech 51 (2003), 487–491. 9. Z. Xu, B. Wei, B. Cao, X. Guo, X. Zhang, D. Wang, X. Song, and X. Lu, A Compact Superconducting Filter at 6.5 MHz Using Capacitor-Loaded Spiral-in-Spiral-Out Resonators, IEEE Microwave Wirel Components Lett 24 (2014), 242–244. 10. Z. Ying, X. Guo, B. Cao, X. Zhang, B. Wei, Y. Zhang, Q. Li, C. Feng, X. Song, Y. Heng, and G. Zhang, A compact superconducting bandpass filter at 360 MHz with very wide stopband using modified spiral resonators, IEEE Trans Appl Supercond 23 (2013), 1–6. 11. J. Garc  ıa-garc  ıa, F. Mart  ın, F. Falcone, J. Bonache, J. D. Baena, I. Gil, E. Amat, T. Lopetegi, M. A. G. Laso, J. Antonio, M. Iturmendi, M. Sorolla, S. Member, and R. Marqu es, Microwave Filters With Improved Stopband Based on Sub-Wavelength Resonators, IGGF Trans Microwave Theory Tech, 53(2005), 1997–2006. 12. A. V elez and F. Aznar, Stop-band and bandpass filters in coplanar waveguide technology implemented by means of electrically small metamaterial-inspired open resonators, Propag IET (2010). 13. N. Zhang, Z. Deng, and F. Sen, CPW Tunable Band-Stop Filter Using Hybrid Resonator and Employing RF MEMS Capacitors, IEEE Trans Electron Devices 60 (2013), 2648–2655. V C 2016 Wiley Periodicals, Inc. A NOVEL COMPACT DUAL-BAND DUAL-POLARIZED MICROSTRIP PATCH ANTENNA FOR GSM/DCS APPLICATIONS Ali Vedaee and Hamid R. Hassani Department of Electrical Engineering, Shahed University, Tehran, Iran; Corresponding author: ali.vedaei@shahed.ac.ir and hassani@shahed.ac.ir Received 31 March 2016 ABSTRACT: In this paper, a novel compact dual-band dual-polarized microstrip stacked patch antenna suitable for base stations is presented. The first and second frequency bands cover the GSM and DCS bands respectively. The antenna layout consists of a single circular patch with four symmetrical slots along its periphery mainly responsible for the upper frequency band and one cross-shaped slot at the center, mainly responsible for the lower one. The stacked configuration is considered for bandwidth enhancement. The antenna utilizes a simple orthogonal feed network for the two polarizations, which feeds the patch through a relatively wide cross-shaped slot at the antenna’s ground plane, placed centrally with respect to the patch. The antenna bandwidth completely covers the two desired bands with relatively good return loss and also exhibits polarization isolation of greater than 33 dB and 40 dB in the lower and upper frequency bands respectively. In addition, the antenna has good radiation characteristics in terms of cross-polarization in both bands of interest. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2557–2559, 2016; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.30099 Key words: circular notched patch antennas; DCS; dual-band anten- nas; dual-polarized antennas; GSM 1. INTRODUCTION Multiband antennas with polarization diversity, have been sub- ject of many research activities in the past two decades mainly due to capacity problems in receiving and transmitting of data in older single frequency single polarization antenna systems. Among them dual-band dual-polarized (DBDP) antennas, almost in patch configuration, have wide applications in areas such as wireless communications, radar imaging (SAR) etc. As we know, about five reported works exist in the area of DBDP antennas operating in GSM (880-960 MHz) and DCS (1710-1880 MHz) frequency bands [1–5]. In Ref. [1], a DBDP stacked patch antenna configuration is proposed, with relatively good results as impedance bandwidth and radiation properties; but it has relatively large thickness and since it makes the use of air bridge at the cross point of two orthogonal feed networks; its fabrication is difficult. The proposed antenna in Ref. [2] has relatively good isolation between polarizations and also good pattern characteristics, but it does not cover the significant amont of lower frequency band and also has bulky structure with relatively large thickness and probably is not cost efficient due to use of four ridged cavity at the back of lower band slots for port isolation insurement. Another reported work in Ref. [3], has relatively a complex feed network, makes some diffculty in design process. In Ref. [4], DBDP antennna is reccomended in 1*4 linear array form. As the elements of the lower and upper band does not share the same aperture in each unit cell of the array, the total size of it increases signifigantly with respect to ones share the same aperture. Finally the antenna array sugested in Ref. [5], exhibits nearly good results in radiation characteris- tics and impedance and isolation bandwidth, but its single ele- ments has yet comparatively large size, makes area usage and cost to be not efficient. On the basis of above analysis, no one tries to design a single circular patch capable of supporting simultanously dual-band and dual-polarized operation, which can takes advantagaous of above reported works in addition to significant size reduction in single and array form. In this study, a single element antenna, capable of supporting simultaneously two frequency bands of GSM and DCS in dual orthogonal polarizations is presented. The antenna element con- sists of one circular notched patch stacked over one dielectric substrate of FR4 and 21 mm foam layer beneath of it as spacer. The antenna feeding method exploits from one cross-shaped slot embedded centrally with respect to the patch at the antenna’s ground plane, sandwitched between two layers of FR4 substrate at the bottom of the foam layer. The feed network composed of two orthogonal corporate microstrip lines, placed on two differ- ent sides of ground plane, coupling energy through aforesaid slot to the patch. The suggested design has benefit of integration of single compact antenna element usage with simple feed net- work simultaneously in addition to relatively good results in terms of return loss, port decoupling and pattern characteristics which will be discussed in detail in the following sections. 2. ANTENNA DESIGN The antenna structure is demonstrated in Figures 1(a)–1(c). As can be seen in Figure 1(a), there are four layers of dielectric substrates employed in the antenna structure. Layers 1, 3 and 4 are FR4 substrate with dielectric constant of 4.4 and thickness of 1.6 mm. The slotted ground plane is embedded between layers 3 and 4 and radiating patch is on top of layer 1. Layer 2 acts as spacer and consists of one foam layer with dielectric constant of 1.06 and thickness of 21 mm. The stacked configu- ration is considered for bandwidth enhancement. There are three major considerations in design process of this antenna. The first one of them is the antenna patch structure with its associated notches to be responsible for the two men- tioned frequency bands at two polarizations. Another one is the ground plane slot and the third one of them is the antenna feed network. In the next subsections these subjects will be discussed in detail. DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 58, No. 11, November 2016 2557