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  Progress In Electromagnetics Research C, Vol. 6, 145–158, 2009  DESIGN OF RECONFIGURABLE PATCH ANTENNAWITH A SWITCHABLE V-SLOTT. Al-Maznaee and H. E. Abd-El-Raouf  Department of Electrical and Computer EngineeringInternational Islamic University Malaysia (IIUM)53100 Kuala Lumpur, Malaysia Abstract —In this paper we present the design of a novel PatchAntenna with Switchable V-Slot (PASVS) that resonates at twodifferent frequencies. The antenna operates at the lower frequencywhen the switch is OFF and at the higher frequency when the switchis ON. This antenna is designed for special applications which needsmall frequency ratio. The different effects of the feeding position,slot location, and slot length are investigated in this paper. Thisinvestigation has been used to optimize the design of the PASVSantenna in terms of the return loss (RL), bandwidth, gain, and requiredfrequency ratio. 1. INTRODUCTION Many of the wireless communications today require antennas thatoperate at more than just one frequency while maintaining a smallsize [1]. Although patch antennas suffer from narrow bandwidths,different approaches have been used to increase bandwidths of patchantenna [2,3]. In [4], E-shaped patch antenna using two slotsis introduced to design an antenna resonating at two resonantfrequencies.In [5,6], the design of patch antennas with switchable slots hasbeen presented for different wireless communication applications, e.g.,dual band, circular polarized antennas for the UHF band. Anotherdesign for a wideband, multiple frequency microstrip patch antennabased on multi-slots hole-coupled in a substrate has been presentedin [3]. Corresponding author: H. E. Abd-El-Raouf (hany el  146 Al-Maznaee and Abd-El-Raouf  PIN diodes have been used in different designs to developreconfigurable antennas. It is explained in [6] how the antenna canbe reconfigured at different frequency bands depending on the state of an embedded switch, which was implemented using a PIN diode. In[7], PIN diodes were used to shorten an annular slot antenna, whichproduce a reconfigurable antenna with a controlled radiation pattern.Pattern and frequency reconfigurable slot antenna has been obtainedusing matching stubs and PIN diodes [8]. The PIN diodes are usedto connect or disconnect the stubs creating a reconfigurable matchingnetwork. Wu and Ma [9] developed an antenna that has the abilityto switch its radiation pattern between three states by using threePIN diodes with a DC biased network. Another application using PINdiodes in reconfiguring the antenna is to achieve circular polarizationdiversity. This kind of reconfiguration has been presented in [10] byswitching four diodes between ON and OFF, then the antenna canoperate between two cases: right-hand circular polarization (RHCP)or left-hand circular polarization (LHCP) mode.In this paper we propose a patch antenna with switchable V-slot (PASVS) to achieve the antenna reconfigurability. A switchingdiode is inserted between the two arms of a V-slot cut on the patch tocontrol the antenna operation status using DC bias so that the antennaoperates at two resonant frequencies corresponding to the ON and OFFmodes of the switch. The shape of the V slot is expected to give anadvantage in the frequency ratio than the one used in [5], because theV-shape has the ability to be longer (depends also on the angle of theV-shape) than using a slot parallel to the patch edge. Figure 1.  The geometry of a patch antenna with a switchable V-slot(PASVS).  Progress In Electromagnetics Research C, Vol. 6, 2009 147 2. OPERATIONAL MECHANISM OF PASVS A basic PASVS structure is shown in Fig. 1. The antenna dimensionsare  Lg × Wg . The antenna was designed and fabricated on a dielectricsubstrate with permittivity  ε r  and thickness  h g . The material of theground plane and patch is copper. A 50Ω coaxial line is used to feedthe antenna with an inner conductor connected at the feeding position( X  f  ,  Y  f  ), where the dimensions are measured from the center of thepatch. A V-slot with two arms, each with length  L s  and width  W  s , anda vertex at the position  P  s  was incorporated into the patch. A switch(which can be P-I-N diode or MEMS switch) was inserted between thetwo arms to change the resonant frequency.We will study the behavior of the antenna in three modes: withoutthe slot, with the slot when the switch is OFF, and with the slot whenthe switch is ON. We use it for the simulation of the Finite IntegrationTechnique (FIT) based on the commercial software CST.The ON and OFF modes are designed as explained in Section8 of this paper, so that the effective length of the radiating patch isshorter in the case of the ON mode than in OFF mode, which leads toa resonant frequency in the ON case higher than the OFF mode.In the OFF mode, the switch is removed from the simulation andthe patch should be simulated with a complete V-slot. When the switchis ON, it is modeled as a metal tape. The configuration of the threemodes are shown in Fig. 2. (a) (b) (c) Figure 2.  (a) The patch antenna without slot, (b) OFF mode, (c)ON mode.As an initial design, we used a 25mm × 25mm FR-4 substrate( ε r  = 4 . 9 and Loss tangent of 0.019) with thickness  h g  = 1 . 575mm.The other patch parameters are listed below (in mm) according toFig. 1: L  =  W   = 12 ,  ( X  f  ,Y  f  ) = ( − 4 , 0) , L s  = 6 , W  s  = 1 , P  s  = 4 . 25 (1)  148 Al-Maznaee and Abd-El-Raouf  (a)(b)(c) Figure 3.  (a) Return loss for the patch antenna without slot. (b)Return loss for a patch antenna with the slot when the switch is ON.(c) Return loss for a patch antenna with the slot when the switch isOFF.

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Jul 23, 2017
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