Directivity Enhancement of a Broadband Printed Antenna by Using Two Closely Spaced Strips

The bandwidth of a printed rectangular loop antenna with two gaps can be enlarged by using the metallic strips as directors. However, the directivity is not good. Because the two closely spaced metallic strips act as a building block, they can be used to block the propagation of electromagnetic waves. Therefore, two closely spaced metallic strips as a new reflector are adopted and investigated in this paper for improving the directivity of antenna. Two arrangement modes of the printed antennas with two closely spaced strips are designed, fabricated, and measured. Experimental results show that the impedance bandwidth of type A antenna (with inner strip) is about 62.5% ranging from 2.3 to 4.39 GHz. In addition, the gain of 3.8–5.2 dBi and 2 dB improvement of F/B ratio are achieved. Type B antenna (with outer strip) can realize a 62% measured bandwidth ranging from 2.29 to 4.35 GHz. Also, about 3.4 to 4.9 dBi of gain with 2.5 dB improvement of F/B ratio is obtained. The measured F/B ratios of the two modified antennas are both better than 10 dB within the operating frequency band. Measured results verified that adopting the two closely spaced metallic strips as a new reflector can both enhance the F/B ratio and gain without changing the overall dimensions and operating frequency.

[1]  Z. Nie,et al.  A wideband printed antenna with unidirectinal radiation characteristics , 2013, IEEE Antennas and Propagation Society International Symposium.

[2]  Lei Ge,et al.  A Wideband Magneto-Electric Dipole Antenna , 2012, IEEE Transactions on Antennas and Propagation.

[3]  Donglin Su,et al.  A Novel Reversed T-Match Antenna With Compact Size and Low Profile for Ultrawideband Applications , 2012, IEEE Transactions on Antennas and Propagation.

[4]  Gangbing Song,et al.  Compact Wideband Unidirectional Antenna With a Reflector Connected to the Ground Using a Stub , 2011, IEEE Antennas and Wireless Propagation Letters.

[5]  Gabriel M. Rebeiz,et al.  Differentially-Fed Millimeter-Wave Yagi-Uda Antennas With Folded Dipole Feed , 2010, IEEE Transactions on Antennas and Propagation.

[6]  Y. Wang,et al.  Plasmon-induced transparency in metamaterials. , 2008, Physical review letters.

[7]  M. Tentzeris,et al.  Design and Development of a Novel Compact Soft-Surface Structure for the Front-to-Back Ratio Improvement and Size Reduction of a Microstrip Yagi Array Antenna , 2008, IEEE Antennas and Wireless Propagation Letters.

[8]  Hao Ling,et al.  Design of a Closely Spaced, Folded Yagi Antenna , 2006, IEEE Antennas and Wireless Propagation Letters.

[9]  Best.  Improving the performance properties of a dipole element closely spaced to a PEC ground plane , 2004, IEEE Antennas and Wireless Propagation Letters.

[10]  Qing Huo Liu,et al.  A Broadband Unidirectional Antenna Based on Closely Spaced Loading Method , 2013, IEEE Transactions on Antennas and Propagation.

[11]  Sungkyun Lim,et al.  Design of Multi-Band, Compact Parasitic Array With Twisted, Helical Directors , 2013, IEEE Transactions on Antennas and Propagation.

[12]  Sungkyun Lim,et al.  Design of a Dual-Band, Compact Yagi Antenna Over an EBG Ground Plane , 2009, IEEE Antennas and Wireless Propagation Letters.

[13]  J. Laskar,et al.  Unidirectional printed loop antenna , 2003, 6th International SYmposium on Antennas, Propagation and EM Theory, 2003. Proceedings. 2003.