Pattern Diversity Compact Patch Antenna

1. Pattern Diversity Compact Patch Antenna M. S. Ruiz Palacios, M. J. Martínez Silva Universidad de Guadalajara, Jalisco, México Abstract— Diversity is a required property for antennas in Multiple Input-Multiple Output (MIMO) systems. In this paper a pattern diversity antenna is presented for operation in the 2.4 band of IEEE 802.11n WLAN MIMO standard. This compact antenna is formed by two shorted air substrate patch antennas located back to back in order to produce two lobes oriented in different directions. Input matching is done by using a long feed wire. Return loss of the input at the center frequency is grater than 20 dB, and isolation between ports is less than -20 dB within the full bandwidth. Half power beamwidth of combined lobes is grater than 80 degrees making this antenna attractive for wall mounting applications. III. ANTENNA SIMULATION • I-INTRODUCTION • Antennas for MIMO systems can be obtained by accommodating identical antennas in an array (linear, planar, etc.) with a separation of • There are several ways for obtaining diversity in compact antenna arrays: Pattern diversity, multimode diversity, polarization diversity and space diversity. • A pattern diversity patch antenna for operation in the low band of WLAN 802.11n is calculated, simulated, constructed and measured. Because of symmetry, the directivity of antenna 2 has the same distribution, but directed to a symmetric direction. II. ANTENNA DEVELOPMENT Basic patch was calculated using a standard procedure [7]. It was decided to use de same value for W and L. Also, it was introduced a finite ground plane of half wavelength on each side. the complete structure shown below was introduced in the simulator, using an elevation h0 of one quarter of wavelength in order to produce a near broadside pattern. With a finite ground plane, the main lobe was directed to a different direction, which was a desired characteristic for this antenna. By adjusting geometry, it was possible to obtain a satisfactory response. It was necessary to introduce a long feed wire of 15 mm to compensate capacitive effect produced by the short circuit. Final values of geometry are in the table. Construction and Measurements The antenna was constructed and input impedance was measured as shown in the figures Simulated and measured and Final values of geometry elements Total directivity of antenna 1, 2D plot. Clear that main lobe of antenna 1 is directed to . Half power beamwidth for antenna 1 is 39° approximately. Because of symmetry of the structure, main lobe of antenna 2 is directed to Total directivity of both shorted patch antennas, 2D plot V. CONCLUSION MIMO technology has not become to maturity. Continuous search for new solutions in all related areas are still an important activity for researches and engineers. Antenna presented in this work offer pattern diversity within a total beamwidth of 80 degrees. Input reflection coefficient (near -20 dB) and isolation between ports (less than -20 dB) are within useful values. Although this antenna is not low profile, it requires a surface of less than 12 cm x 12 cm, which is small enough to be considered compact. Measured results indicate that theory behind this antenna is correct and can be applied to other similar geometries. REFERENCES [1]Q. Li and G. Li, "MIMO Techniques in WiMAX and LTE: A Feature Overview," IEEE Communications Magazine, Vol. 46, Issue 5,May 2010, pp. 86-92. [2] IEEE 802.11n-2009—Amendment 5: Enhancements for Higher Throughput. IEEE-SA. 29 October 2009 [3] Borja, A. Algans, M. Royo, J. Anguera, and C. Puente, "Impact Of The Antenna Technology And The Antenna Parameters on the Performance of Mimo Systems", Proc. of the Antennas and Propagation Society International Symposium, 2003. pp. 507 - 510 vol.2 [4] Öcalan, A. Savaçhabe, b. Görgeç, Ö. Ertu and E. Yazgan, Compact Space-Multimode Diversity Stacked Circular Microstrip Antenna Array for 802.11n MIMO-OFDM WLANs, 2009 Loughborough Antennas & Propagation Conference, November 2009, Loughborough, UK [5] Sha Hu, Jin Pan, Jianbiao Qiu, “A Compact Polarization Diversity MIMO Microstrip Patch Antenna Array with Dual Slant Polarizations”, [6] Haili Zhang, Zhihong Wang, Jiawei Yu, and Jia Huang, “A Compact MIMO Antenna for Wireless Communication”, IEEE Antennas and Propagation Magazine, Vol. 50, No.6, December 2008, pp. 104-107. [7] Balanis, Constantine, Antenna Theory Analysis and Design (3rd Ed), Wiley 2005, pp. 825