288 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 12, 2013 Dielectric-Loaded Compact WLAN/WCDMA Antenna With Shorted Loop and Monopole Elements BahadırYıldırım, Member, IEEE, Erkul Başaran, and Bahattin Türetken Abstract—A compact, planar, dielectric-loaded, and mul- tiple-band antenna for 2.45/5-GHz WLAN and 2.1-GHz wideband code-division multiple access (WCDMA) applications is presented in this letter. The antenna has a planar loop element with a shorting pin and a planar monopole element that are printed on the same substrate and driven by a microstrip line. The loop and monopole elements are covered by a thin FR4 layer on top to achieve good impedance matching at both bands. Analysis of the antenna has been realized using extensive 3-D full-wave elec- tromagnetic simulations. Antenna measurements have also been presented, and it is shown that measurements and simulations are in good agreement. Index Terms—Electromagnetic analysis, multiple-band antennas, wireless LAN. I. INTRODUCTION A DIELECTRIC-LOADED, compact, planar, and mul- tiple-band antenna for 2.45/5-GHz WLAN and 2.1-GHz wideband code-division multiple access (WCDMA) applica- tions is presented in this letter. The antenna includes a loop element with a shorting pin and a monopole element; both are printed on FR4-type low-cost and easily available dielectric substrate. The antenna is driven by a 50- microstrip line. Loop-type antennas are well known in the literature. These include a vertically mounted planar antenna of loop form on a mobile phone printed circuit board (PCB) that operates from about 2.7 to 5.9 GHz [1], a loop antenna for 2.45-GHz WLAN band [2], and a folded monopole/loop antenna for DCS 1.8-GHz band [3]. These antennas have a single loop element to generate the desired band(s). A multiband capacitively loaded loop antenna for mobile handsets has been reported in [4]. However, the radiating element was placed on another substrate above the PCB, and an overlap region was used to realize a capacitive short between the radiating element and the RF ground. This antenna can operate at 2.1-GHz WCDMA and 2.45/5-GHz WLAN bands with 6-dB return-loss specification. The presented antenna has 10-dB return-loss specification, and therefore it has a better impedance-matching property. Manuscript received September 26, 2012; revised November 10, 2012, De- cember 31, 2012; accepted January 17, 2013. Date of publication February 20, 2013; date of current version March 15, 2013. B. Yıldırım is with Doğuş University, Istanbul 34722, Turkey (e-mail: byildirim@dogus.edu.tr). E. Başaran and B. Türetken are with Tübitak Bilgem, Gebze 41470, Turkey (e-mail: erkul.basaran@tubitak.gov.tr; bahattin.turetken@tubitak.gov.tr). Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LAWP.2013.2246034 Multielement antennas including loop- and monopole-type elements have been reported for WWAN [5] and WLAN [6] functionality of laptops. The antenna presented in this letter has also been formed by a planar loop and a planar monopole, however 2.1-GHz WCDMA functionality has been added over the 2.45/5-GHz WLAN band. The presented antenna has also been loaded by a thin FR4 layer on top to achieve good impedance matching at both bands. Dielectric loading technique is not new [7], however the integration of loop and monopole elements with a dielectric layer on top of them is a novel technique. Analysis of the antenna was carried out using 3-D full-wave electromagnetic simulations by Ansoft HFSS [8] and CST Microwave Studio [9]. II. ANTENNA DESIGN: SIMULATIONS AND MEASUREMENTS The antenna was built on a 1-mm-thick FR4 substrate whose permittivity and loss tangent are 4.4 and 0.02, respectively. The substrate dimensions are 58 62 mm , and the geometry of the antenna is shown in Fig. 1. A photograph of the fabricated an- tenna is shown in Fig. 2. The antenna radiating element con- sists of a planar loop and a planar monopole. The loop element is shorted to RF ground through a 1.2-mm-diameter shorting pin. During the simulations, this shorting pin has been imple- mented as a 1.2-mm-diameter copper cylinder. For the fabri- cated antenna, an about 1-mm-diameter hole was drilled after the fabrication and filled with a conductive fluid, which became solid after a while. The width of the feeding microstrip line is chosen to be 2 mm on 1-mm-high FR4 substrate to realize the 50- characteristic impedance. The width of the loop and the monopole elements is also 2 mm. The antenna is loaded by a thin FR4 layer on top whose dimensions are 20 22 mm . Here, is the thickness of the top FR4 layer. Top- and bottom-layer copper metallization has a thickness of 0.035 mm for the simu- lation model. Fig. 3 shows the effect of the loop and the monopole el- ements individually over the antenna response. It can be seen that the high band is generated by the monopole, whereas the low band is generated by the coupling of the loop and the monopole. The coupling effect can be explained as follows. In the absence of the monopole, the first loop resonance is around 2 GHz, which is about 1.0- resonant mode, with more than 9 dB. In the absence of the loop, the monopole has a resonance at around 2.1 GHz with of about 10 dB. The resonances due to only-loop and only-monopole cases are weak in the sense that does not meet the 10-dB specification with a us- able bandwidth. However, when the loop and the monopole el- ements exist together, a coupling occurs between them through these two weak resonances, and as a result, a stronger resonance 1536-1225/$31.00 © 2013 IEEE