Progre In Electromagnetic Reearch Letter, Vol. 3, 51, 08 BUILT-IN DUAL FREQUENCY ANTENNA WITH AN EMBEDDED CAMERA AND A VERTICAL GROUND PLANE S. H. Zainud-Deen Faculty of Electronic Engineering Menoufia Univerity Egypt S. M. Gaber and S. M. M. Ibrahem Faculty of Engineering Helwan Univerity Egypt Abtract A thin internal planar antenna for GSM/DCS with a hollow horting cylinder uitable for integration with an embedded digital camera for a mobile phone i preented. A mall vertical ground plane electrically connected to the ytem ground plane of the mobile phone i ued. The vertical ground plane can function a an effective hield wall between the antenna and the nearby electronic element in the mobile phone. The method of moment i ued to imulate the antenna tructure and calculate the radiation characteritic of the antenna. 1. INTRODUCTION Planar antenna, including microtrip and printed antenna and other type of antenna that are flat in appearance and have a low profile, have recently received much attention for application in cellular communication ytem, uch a the global ytem for mobile communication (GSM), the digital communication ytem for mobile (DCS), peronal communication ytem (PCS), the univeral mobile telecommunication ytem (UMTS), and wirele local area network (WLAN) in the 2.4 GHz and 5.2 GHz band. Many novel deign of planar antenna for the above application have been reported very recently [1 11]. The configuration of the conventional internal
52 Zainud-Deen, Gaber, and Ibrahem patch antenna, however allow the fringing electromagnetic (EM) field to eaily penetrate into the urrounding region of the antenna. In thi cae, ome coupling between the antenna and the nearby electronic component will occur reulting in degrading effect on the performance of the antenna. To reduce thi degrading coupling effect, an iolation ditance of about 7 mm or larger between the antenna and the nearby electronic component i uually required for practical application [3]. Thi iolation ditance lead to an inefficient uage of the valuable board pace of the ytem circuit board of the mobile device. In many wirele device, a digital camera i uually embedded, preferably at the top portion of the device ytem circuit board a well and thu competing for the very limited pace of the ytem circuit board with the internal antenna. In thi paper, a thin GSM/DCS dual-band internal patch antenna with an air-layer ubtrate a in [5] i preented. Hollow horting cylinder i ued to accommodate the charge-coupled device (CCD) of an embedded digital camera in a mobile phone, thu leading to a compact integration of the antenna and CCD. The horting cylinder alo erve to upport the propoed antenna firmly above the grounded ubtrate. Small vertical ground plane electrically connected to the ytem ground plane of the mobile phone i preented. The vertical ground plane can function a an effective hielding wall between the antenna and the nearby RF-hielding metal cae or other aociated element in a mobile phone. In thi cae, the internal antenna can be compactly integrated within the mobile phone without degradation of the antenna performance. 2. ANALYSIS The imulated reult in thi paper are obtained uing the method of moment (MoM) [12]. The radiation characteritic of the antenna tarting from the total field equation: E(r) =E i (r)+ G(r/r ) J(r )d (1) where E(r) i the total tangential field on the urface, E i (r) ithe incident field on the conducting urface, G(r/r ) i the dyadic Green function, and J(r ) i the current ditribution on the conducting urface S. For a typical highly conductive tructure, the induce current i flowing on the conducting urface S of the antenna and boundary condition E(r) =Z (r)j(r), r S (2)
Progre In Electromagnetic Reearch Letter, Vol. 3, 08 53 where Z (r) i the urface impedance of the conductor. From Eq. (1) and (2), then Z (r)j(r) =E i (r)+ G(r/r ) J(r )d (3) By auming that the current ditribution i repreented by a et of complete bai function: N J(r )= I n B n (r ), n =1, 2, 3,... (4) n where, N i the number of finite term. After ome manipulation and uing the tet function the ame a the bai function (Galerkin method), Eq. (3) become an N Nmatrix equation, where Z mn = V m = Z (r)b m (r) B n (r)d [Z mn ][I n ]=[V m ] (5) d B m (r) Ḡ(r/r ) B n (r )d (6) E i (r) B n (r)d (7) The olution of Eq. (5) are the coefficient of the expanded current ditribution in Eq. (4). In thi analyi roof-top function are ued to approximate the current ditribution on the antenna. A roof-top function i a ramp in the longitudinal direction and contant on the tranvere direction. After the current ditribution i olved, the antenna parameter can be calculated. 3. NUMERICAL RESULTS Figure 1 how the geometry of the antenna mounted at the top portion of the ytem ground plane of a mobile phone (ize mm 2 ). The antenna ue a hollow horting cylinder of diameter 6 mm in place of a conventional horting pin to contain the len of a practical embedded digital camera. The occupied volume of the antenna i about the ame a that in [5]. The vertical ground ha the ame height (3 mm) a the antenna thickne and at a ditance d = 0.5 mm from the antenna. Before extenive numerical calculation are performed, the
54 Zainud-Deen, Gaber, and Ibrahem radiation characteritic of the internal GSM/DCS patch antenna for a portable mobile terminal a in [5, Figure 1] were calculated to verify the accuracy of the computer program. Figure 2 depict the variation of the return lo in db veru the frequency for the antenna tructure. The radiation characteritic of the antenna are compared with the meaurement in Figure 3 at frequency f = 925 and f = 1795 MHz. Good agreement i oberved between the imulated reult and the meaured reult. The hollow horting cylinder of diameter 6 mm i ued a a firt modification for the antenna tructure in [5]. The poition of the feeding pin i modified a in Figure 1 to keep the ame reonant frequencie approximately the ame a in [5]. The effect of the hollow horting cylinder on the return lo and on the radiation characteritic are depicted on Figure 4 and 5. The radiation pattern with and without the hollow horting cylinder are almot identical. Figure 6 how the imulated reult of the return lo after adding the vertical plane at a ditance d =0.5 mm from the edge of the antenna y z x 15 mm mm Rectangular ground plane B A Vertical ground plane 3 mm L= mm t=4 mm mm (a) 15 mm 17 mm 12 mm 1 mm 42mm Bending line 7 mm t=4 mm 1 mm B A 41mm mm 15 mm 35 mm d mm (b) Figure1. (a) Geometry of the mobile-phone antenna. (b) Top view.
Progre In Electromagnetic Reearch Letter, Vol. 3, 08 55 (ee Figure 1). The impedance bandwidth, defined by 2.5:1 VSWR (about 7.3 db return lo) i 94 MHz for the GSM band and 189 MHz for DCS band. Figure 7 how the radiation pattern of the antenna at 925 MHz and 1795 MHz in different plane. Stable radiation pattern are noticed. 0-5 Return Lo (db) - -15-0.884 0.973 1.750 1.9-25 Meaured [5] Simulated - 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 Frequency (GHz) Figure2. Simulated and meaured return lo. 50 180 0 φ 180 0θ 2 3 - - 2 0 - x-y - Meaured E θ [5] Meaured E φ [5] - - - (a) -
56 Zainud-Deen, Gaber, and Ibrahem 180 0 φ 2 3 - - 2 0 - x-y - Meaured E θ [5] - - Meaured E φ [5] - (b) - Figure3. Simulated and meaured radiation pattern in different plane. (a) at f = 925 MHz, (b) at f = 1795 MHz. 0-5 Return lo (db) - -15-0.88 0.974 1.705 1.894-25 - 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 Frequency (GHz) Figure4. cylinder. Simulated return lo after acting the hollow horting
Progre In Electromagnetic Reearch Letter, Vol. 3, 08 57 180 0 φ 2 3 - - 2 x-y 0 - - - - - 180 0 φ (a) - 50 2 3 - - 2 x-y 0 - - - - - (b) - Figure5. Simulated radiation pattern in different plane after adding the hollow horting cylinder. (a) f = 925 MHz, (b) f = 1795 MHz.
58 Zainud-Deen, Gaber, and Ibrahem 0-5 Return Lo (db) - -15-0.88 0.974 1.705 1.894-25 - 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 Frequency (GHz) Figure6. Simulated return lo after acting the hollow horting cylinder and vertical plate. 180 0 φ 2 3 - - 2 x-y 0 - - - - - (a) -
Progre In Electromagnetic Reearch Letter, Vol. 3, 08 59 50 180 0 φ 2 3 - - 2 0 - x-y - - - - (b) - Figure7. Simulated and meaured radiation pattern in different plane after adding the hollow cylinder and vertical plate. (a) at f = 925 MHz, (b) at f = 1795 MHz. 4. CONCLUSIONS A built-in dual frequency antenna with an embedded camera and a vertical ground plane i invetigated. A vertical-ground plane i ued. Hollow horting cylinder i propoed to embedded the digital camera inide the antenna tructure. Good iolation behavior between the antenna and a nearby element uch a the RF-hielding metal cae inide the mobile phone ha been achieved. Good radiation characteritic ha been oberved. REFERENCES 1. Wong, K. L., Planar Antenna for Wirele Communication, Wiley, New York, 03.
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