Circular patch antenna for WLAN and XBand applications

Abstract

A novel coplanar wave guide(CPW) fed circular patch antenna with capacitive loading is proposed. The structure is characterised by WLAN,X-Band and ITU band applications. The radiating patch is not in contact with feed. The desired antenna has dimensions 28x25 mm 2 .The proposed antenna has wide frequency bandwidth of 7.7GHz starting from 4.63GHz to 12.33GHz for a return loss(S 11)of less than-10dB. Keyword-CPW,Circular patch,Capacitive loading,Return loss I. INTRODUCTION In modern wireless communiation there is need and demand for systems which are tiny in size,lower cost,lighter weight which may exhibit high data rate and giving up high performance especially in Ultra wide band region[1].Microstrip patch (MSP)antenna which may satisfies most of the requirements.MSP antenna are easily integrated with microwave integrated circuits.CPW feeding ground and radiating patch is on same planar plane.In CPW feeding no via holes are required so that it is considered less complex and fabrication is easy.The designing of compact antenna for portable wireless communication systems is the major task,which could meet the high bandwidth requirements. A 32x16 mm 2 ring monopole antenna with double meander lines for dual band operation was presented in [2].Another compact 20x15.5mm 2 CPW-monopole antenna using two strips for dual-band wireless local area(WLAN) operation was proposed in [3] giving bandwidth from 2.4 to 2.484GHz and 5.15 to 5.825GHz.In[4],a 30x20mm 2 CPW-fed patch antenna for dual band is proposed.A very wide bandwidth is achieved with circular slot fed with CPW line through a circular patch[5].In [6],41.6x28.38mm 2 CPW-fed planar monopole antenna composed of circular radiating patch with smiling slot for dual band operation was presented, and the antenna achieved dual impedance bandwidths from 2.3 to 3 GHz and 4.7 to 5.9 GHz.The antenna presented in [7] has large ground plane.A 30x30mm 2 was proposed in[8] for an impedance bandwidth of 3.1-8.3GHz.Which consists of tapered radiating patch over rectangular patch.Feed patch is close to radiating patch but not in contact with that is developed in [9] shows the capacitive loading of the antenna. II. ANTENNA DESIGN A. CPW design CPW feeding is applied in this proposed antenna where feed is a centre strip that carries the signal and sideplane conductor is ground. Ground is on either side of the feed on the same plane so no via holes are required.CPW feeding applied in this design is finite dielectric thickness and finite width ground plane as shown in Fig 1.CPW structures usually provide wider bandwidth, easy integration with RF circuitry, better impedance matching and less dispersion. Fig 1:CPW Structure The transmission line structure is divided into two halves:upper half which is above metalization,and lower half which is below metalization.Capacitance per unit length for each half is determined by transforming into a parallel plate geometry using conformal transformation. The below equations are based on the quasi-static analysis, q is known as filling factor. q ′ ′