A Modal Approach to Tuning and Bandwidth Enhancement of an Electrically Small Antenna

We describe the physical phenomena that contribute to the behavior of an electrically small TM10 antenna using characteristic mode theory. The application of characteristic modes to antenna tuning and bandwidth enhancement serves as demonstration of the broad utility of the modal technique. A modal analysis of the TM10 antenna's impedance match yields several interesting observations as to the nature of resonances and antiresonances, which has implications for the impedance matching of small antennas in general. Furthermore, to overcome the bandwidth limitations inherent in small antennas, we determine that multiple resonances must be combined and use a conductance ratio as a figure of merit for design. We then investigate the TM10 antenna's potential for multiresonant operation by examining different candidate modes. Using the appropriate characteristic modes to form multiple resonances, we show how the bandwidth of the TM10 antenna can be designed to be nearly double that expected from the physical limit for a single resonance.

[1]  R. Garbacz,et al.  Antenna shape synthesis using characteristic modes , 1982 .

[2]  H. Thal.  New Radiation$Q$Limits for Spherical Wire Antennas , 2006, IEEE Transactions on Antennas and Propagation.

[3]  J. Mclean.  A re-examination of the fundamental limits on the radiation Q of electrically small antennas , 1996 .

[4]  S..  A Re-Examination of the Fundamental Limits on the Radiation Q of Electrically Small Antennas , 2008 .

[5]  Derek A. McNamara,et al.  MIMO handheld antenna design approach using characteristic mode concepts , 2008 .

[6]  Design and analysis of a helical spherical antenna using the theory of characteristic modes , 2008, 2008 IEEE Antennas and Propagation Society International Symposium.

[7]  M. Cabedo-Fabres,et al.  The Theory of Characteristic Modes Revisited: A Contribution to the Design of Antennas for Modern Applications , 2007, IEEE Antennas and Propagation Magazine.

[8]  S.R. Best,et al.  A discussion on the properties of electrically small self-resonant wire antennas , 2004, IEEE Antennas and Propagation Magazine.

[9]  R. Harrington,et al.  Computation of characteristic modes for conducting bodies , 1971 .

[10]  Pavel HAZDRA,et al.  On the Modal Superposition Lying under the MoM Matrix Equations , 2008 .

[11]  H.R. Stuart,et al.  A small wideband multimode antenna , 2008, 2008 IEEE Antennas and Propagation Society International Symposium.

[12]  Marta Cabedo-Fabres,et al.  Simple design for cost‐effective diversity antennas , 2007 .

[13]  S.R. Best,et al.  The goubau multi element monopole antenna - revisited , 2007, 2007 IEEE Antennas and Propagation Society International Symposium.

[14]  R. Harrington,et al.  Theory of characteristic modes for conducting bodies , 1971 .

[15]  Tom Milligan,et al.  Correct Impedance-Matching Limitations , 2009 .

[16]  K. Solbach,et al.  Optimal antenna location on mobile phones chassis based on the numerical analysis of characteristic modes , 2007, 2007 European Microwave Conference.

[17]  Cuong Tran,et al.  Small Spherical Antennas Using Arrays of Electromagnetically Coupled Planar Elements , 2007, IEEE Antennas and Wireless Propagation Letters.

[18]  R. Garbacz,et al.  Self- and mutual-admittances of wire antennas in terms of characteristic modes , 1973 .

[19]  S.R. Best,et al.  Limitations in Relating Quality Factor to Bandwidth in a Double Resonance Small Antenna , 2007, IEEE Antennas and Wireless Propagation Letters.

[20]  R. Hansen.  Correct Impedance-Matching Limitations [Antenna Designer's Notebook] , 2009, IEEE Antennas and Propagation Magazine.

[21]  R.G. Rojas,et al.  Characteristic mode-based design and analysis of an electrically small planar spiral antenna with omnidirectional pattern , 2008, 2008 IEEE Antennas and Propagation Society International Symposium.

[22]  A. Hujanen,et al.  Bandwidth limitations of impedance matched ideal dipoles , 2005, IEEE Transactions on Antennas and Propagation.

[23]  E. Newman.  Small antenna location synthesis using characteristic modes , 1979 .

[24]  H.A. Wheeler,et al.  Fundamental Limitations of Small Antennas , 1947, Proceedings of the IRE.

[25]  L. J. Chu.  Physical Limitations of Omni‐Directional Antennas , 1948 .

[26]  J. Ethier,et al.  The Use of Generalized Characteristic Modes in the Design of MIMO Antennas , 2009, IEEE Transactions on Magnetics.

[27]  R. Garbacz,et al.  A generalized expansion for radiated and scattered fields , 1971 .

[28]  S. Best,et al.  Impedance, bandwidth, and Q of antennas , 2005 .

[29]  J.T. Bernhard,et al.  Tuning Method for a New Electrically Small Antenna With Low $Q$ , 2009, IEEE Antennas and Wireless Propagation Letters.

[30]  J. Mclean,et al.  Limits on the radiation Q of electrically small antennas restricted to oblong bounding regions , 1999, IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.99CH37010).