Research note Electromechanical controlled phased array dumbbell EBG beam steerer Jeffrey S. Fu a, * , Dong-Hua Yang a , Chin-I Yeh a , N.C. Karmakar b , Jui-Ching Cheng a , Kuo-Sheng Chin a , Hsien-Chin Chiu a , Jian Kang Xiao c a High Speed Intelligent Communication Research Center, Chang Gung University, Tao-Yuan 333, Taiwan, ROC b Department of Electrical and Computer Systems Engineering, Monash University, Clayton, VIC 3800, Australia c College of Computer and Information Engineering, Hohai University, Changzhou 213022, China article info Article history: Received 13 November 2009 Received in revised form 16 May 2010 Available online 20 June 2010 abstract A steerable phased array antenna driven mechanically is realized by utilizing the variation of dumbbell electromagnetic bandgap (EBG) structures. The variation takes place under the feed line of a 4-element array that gives the change in relative phase shift. The phase shift achieved from different shaping com- binations of EBGs shifting under the feed lines. The feed lines are connected with four microstrip patches to yield a 4-element phased array antenna. The mechanical controlled pattern shapes of phase array antenna are simulated in electromagnetic (EM) software Zeland IE3D. Finally the design is fabricated with the help of optical lithography. It can be seen that the beam steering angle can be controlled mechanically without phase shifter and PIN switches. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Recently, beam steering in microstrip antennas finds potential applications in many modern devices that include automobiles and airplane radars, satellite communication networks and recon- figurable wireless network. Previous works using EBG assisted phase array had only shown beamforming performance [1,2] and dual band operation in terms of EBG assisted phase array structure [3]. Beam steering performed with digital phase shifters is expen- sive and the number of phase shifters also increases with the num- ber of antennas in an array. Under this circumstance reconfigurable EBG ground plane is highly preferred for beam steering purpose. Elarman et al. [4] proposed a beam steerer using reconfigurable ground plane. They mentioned only the influence of number of EBG elements on the phase properties. Detailed investigations of the transmission phase of EBG assisted transmission line are miss- ing there. Mollah [5] although showed the filling factor (FF) influ- enced EBG assisted beam steering but the shifting angle is limited by the squared patterned EBG element. In dumbbell-shaped EBG beam steerer, FF is re-defined [6]. The dumbbell-shaped EBG can yield wider and deeper stopband [7]. We use this unique property of dumbbell EBG to replace the square patterned EBGs for beam steering design. We propose 1-D EBG that are located under standard 50-ohm lines. 2. Theory EBG is also known as defected ground structure (DGS). DGS structures are periodic structures that prohibit the propagation of electromagnetic waves at certain frequencies. The lumped LC equivalent model of a dumbbell DGS unit cell can be expressed as in Fig. 1 [7]. The equivalent inductance and capacitance in terms of g 1 and f 0 are expressed in Eqs. (1) and (2) [7]. L ¼ z 0 g 1 x c 1  x c x 0   2 " # ð1Þ C ¼ 1 4p 2 f 0 L ð2Þ where f 0 is the frequency of the attenuation pole, x c is the angular cutoff frequency, z 0 is the characteristic impedance of the line, and g 1 is the admittance value of the Butterworth low pass filter re- sponse. The closed form expression of the equivalent circuit and the dimension can be extracted from the standard microstrip line filter synthesis. The periodicity is calculated by the following Bragg’s condition as shown in Eq. (3). ba ¼ p ð3Þ where ‘a’ is the period of the EBG pattern, and ‘b’ is the wave num- ber in the dielectric slab and is defined by the expression below: 0026-2714/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.microrel.2010.05.007 * Corresponding author. Address: Department of Electronic Engineering, Chang Gung University, Tao-Yuan 333, Taiwan, ROC. Tel.: +886 3 2118800x5790; fax: +886 3 2118507. E-mail address: jeffsfu@mail.cgu.edu.tw (J.S. Fu). Microelectronics Reliability 50 (2010) 2093–2097 Contents lists available at ScienceDirect Microelectronics Reliability journal homepage: www.elsevier.com/locate/microrel