Drewniak, James L.

Mayes, P. E.

Tanner, D.

Woodruff, J.

English

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine

Missouri University of Science and Technology Scholars' Mine Electrical and Computer Engineering Faculty Research & Creative Works Electrical and Computer Engineering 01 Jun 1987 A Dual Circular Polarization Radiating-Line Antenna James L. Drewniak Missouri University of Science and Technology, drewniak@mst.edu P. E. Mayes D. Tanner J. Woodruff Follow this and additional works at: https://scholarsmine.mst.edu/ele_comeng_facwork  Part of the Electrical and Computer Engineering Commons Recommended Citation J. L. Drewniak et al., "A Dual Circular Polarization Radiating-Line Antenna," Proceedings of the Antennas and Propagation Society International Symposium (1987, Blacksburg, VA), pp. 348-351, Institute of Electrical and Electronics Engineers (IEEE), Jun 1987. The definitive version is available at https://doi.org/10.1109/APS.1987.1150102 This Article - Conference proceedings is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Electrical and Computer Engineering Faculty Research & Creative Works by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu. APO9-1 A DUAL CIRCULAR POLARIZATION RADIATING-LINE ANTENNA J. DrewniaK, P. Mayes, D. Tanner and J. Woodruff Electromagnetics Laboratory Electrical and Computer Engineering Department University of Illinois a t  Urbana-Champaign INTRODUCTION The  concept of achieving  wideband  performance f r o m  a low-profile  traveling-wave  structure has previously  been in t roduced  [l], 121. The  dual  circularly  polarized (CP) radlatlng-line  antenna 1s one  such  antenna:  a  two-port  antenna from Which both  senses of circular  polarization  are  available, one sense  from  each of the  two ports. I t  haa the low-profile, simplicity and conformability attributes of the microstrip Patch antennas. However, the  near  f ields  have  traveling wave r a t h e r  than resonant mode characteristics and this yields a much wider impedance bandwidth than that  of the  resonant  Patch  antennas. The  impedance bandwidth is theoretically  unlimited  and  an ~ : i  input impedance bandwidth Is easlly  achieved  in practice. The CP bandwidth is much less  than  the impedance bandwidth,  but still grea te r  than  tha t  repor ted  f o r  CP resonant-patch antennas. CP bandwidth of 31X has been observed on one model. Power gain and beam Squint  are  more IiKely t o  Provide  the  ul t imate  limitations on the  bandwidth of acceptable  performance fo r  an indlvldual antenna. ANTENNA STRUCTURE The antenna  geometry is shown in  Figure I. The outer  radius of b = 3.5 cm is chosen based upon the desired frequency band (1.9-2.6 GHz). The  inner   radius   (a)   determines  the fraction of the   input  power t h a t  is radiated.  The  height (h) above t h e  ground  plane IS specified t o  produce  adesired  level of l n p u t  impedance. The antenna  rm is supported  above  the ground  plane by a  dlelectrlc  spacer of low permitt ivity.  The antenna is probe fed in a manner t o  excite a decaying traveling wave with approximately  one  degree of phase  progression along the  outside of the  a rm p e r  degree of rotation  in  azimuth. The fin a t  each port provides a smooth lmpedance transformation from t h e  coaxial  probe t o  t h e  flat strip of t h e  270-degree sector of curved  antenna  arm.  Both  Ports  should be matched t o  eliminate ref lect ions  which would  produce the   oppos i te   s nse  of polarization. RHCP is obtained by feeding t h e  r i g h t  port   (as vlewed f r o m  above the antenna) and terminating the left  Port  in a  matched load. LHCP is obtained by reversing  the  source  and load. ANTENNA PERFORMANCE A Smith  c h a r t  plot of the input impedance i$ Shown in Figure 2. I t  is apparent   hat   he   input  impedance is not   he  CH2435-6/87/0000-0348$01.00 @ 1987 IEEE 348 limiting  factor  in  the  performance  bandwidth,  Figure 3 shows radiation  patterns  taken  from 2.0 t o  2.6 GHz In the  symmetry plane of t h e  antenna USlng a ro ta t ing  dlpole. The pa t t e rn  is primarily a broad,  hemlspherlcal lobe w i t h  an axial ratio on t h e  beam  maximum less than 1.0 dB from 2.0 t o  2.4 GHz and less than 1.5 dB a t  2.6 GHZ. A t  t h e  -3 dB points on t h e  lobe the  axial  r a t i o  is S t i l l  less   than 3.0 dB over 2.0 t o  2.6 GHz. One possible limiting factor in the antenna Performance Is the beam squint which increases w i t h  increasing  frequency. A t  2.6 GHZ t h e  beam  maxlmum deviates a t  most 15 degrees from the vertical axis. An experimental  study  has been conducted to   character ize  the  antenna  Performance  in  terms of the  geometric  parameters. Once t h e   o u t e r   r a d i u s  (b) has been selected f o r  a  given frequency  band,  the  two  variables  which  determine t h e  performance  are:  a, the inner arm radius,  and  h,  the  height above the  ground Plane. In t h e  experimental study the values of h were  selected t o  produce 50-ohm input impedance. The aspect of t h e  performance which is most greatly  dependent upon t h e  inne r   r ad ius  Is t h e   f r a c t i o n  of t h e   i n p u t  power t h a t  is radiated. This was found t o  v a r y  from 35X f o r  a narrow antenna arm t o  72X f o r  a very wide arm. While the  resu l t ing  ra ther  low values of power gain may not be adequate for some applications of the  antenna  as  an  individual radiator,  t h e  simple manner In which  precise  control of t he  power radiated  can be achieved makes the  radiating-line  antenna  an  attractive  element for use in series-fed arrays. CONCLUSIONS I t  has been demonstrated  that   both  senses  of circular polarization  can  be  simultaneously  achieved  from  one  simple low-Profile  antenna.  The  input  impedance of this  dual CP radiating  line  antenna is near  constant  over  very wide bands. operating bandwidths are determined by pat tern and power gain considerat ions rather  than impedance. The f rac t ion  of the  input  power t h a t  is radlated by one of these antennas can be precisely controlled  while  maintaining  a  fixed  level of input impedance by varying the  width and height of t h e  s t r i p  conductor. REFERENCES 1. J. Drewnialr, P. Mayes, D. Tannerl and R. 'Waller, "A log-spiral, radiating-line  antenna," 1986 AP-S International Symposium Digest, pp. 773-776. 2. C. Wood, i'Curved mlcrostrip l ines as compact wideband circularly  polarized  antennas," IEE J. Microwaves, Optics, & Acoustics, Vol. 3, No. 1, pp 5-13, Jan. 1979. 349 Flgure 1. The dual CP radiating-llne antenna. 0.5 - 4.0  GHz Figure 2. Measured Input Impedance. 350 Figure 3. Radiation patterns taKen with a spinning dipole. (Horizontal  scale: 5' per d i v i s i o n )  351 

A Dual Circular Polarization Radiating-Line Antenna

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A Dual Circular Polarization Radiating-Line Antenna

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