Antenna includes two sets of linearly polarized elements. Each set contains slots in parallel array. Sets are mutually orthogonal and are driven in phase quadrature. By changing lengths of slots or their separations, antenna beamwidth can be changed over wide range. Similar results are achieved with dipole configuration

Mailloux, R. J.

Van Atta, L. C.

English

NASA Technical Reports Server

January 1975	 1 B74-10250 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Improved Circulary Polarized Antenna 
The problem: 
Circularly polarized antennas are made using either 
a crossed-slot configuration or an equiangular spiral 
design. Both have some limitations. For example, 
crossed-slot antennas cannot provide circularly 
polarized beams over wide angles. Equiangular spiral 
antennas, on the other hand, have that capability but 
require expensive modifications. 
The solution: 
A new circularly polarized antenna can be 
converted from a narrow beam to a wide beam and 
vice versa without expensive modifications. 
(a) 
Feed Horn
Slots
How it's done: 
The new antenna includes two sets of linearly 
polarized elements. Each set contains slots in a 
parallel array. The sets are mutually orthogonal and 
are driven in phase quadrature. By changing the 
lengths of the slots or their separations, the antenna 
beamwidth can be easily changed over a wide range. 
Similar results are achieved with a dipole config-
uration. 
Shown in Figure 1(a) are two sets of mutually-
orthogonal slot elements, A, B and C, D. The distance 
between a parallel pair is designated as d and the 
length of each slot is designated as h. In operation, 
elements A and B are excited in phase with each 
other. The same situation holds for element C and D. 
As a combination, A, B are excited in phase 
quadrature (90°) with C, D to produce a circularly 
polarized beam. 
A complete slot array is shown on a feed horn in 
Figure 1(b). This configuration provides a relatively 
narrow beam. When the slots are made shorter so that 
they do not intersect, a wide antenna beam results. 
Slot separations can also be varied to produce the 
same effect. Thus feed horns with different slot 
configurations are used to produce desired beam-
widths. 
Figure 2 illustrates a dipole configuration used to 
form a circularly polarized beam. Here a 90° hybrid is 
used to split the incoming signal into phase 
quadrature signals. The signals are applied to the two 
power dividers. Each divider feeds a parallel pair of 
dipole elements. As in the slot configuration, the 
distance between the parallel elements and the lengths 
of the dipole elements determine the width of the 
circularly polarized beam. 
Figure 1. Slot Configuration: 
(a) Magnified View and 
(b) Mounted on a Feed Horn
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19740000250 2020-03-17T13:59:02+00:00Z
Dipole 
Element
Figure 2. Dipole Configuration 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-10250
Patent status:	 - 
This invention has been patented by NASA (U.S. 
Patent No. 3,680,142). Inquiries concerning nonex-
clusive or exclusive license for its commercial develop-
ment should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Lester C. Van Atta

and Robert J. Mailloux
Electronics Research Center

(ERC-10214) 
Categories: 02 (Electronics Systems) 
01 (Electronics - Components and 
Circuitry) 
B74-10250
	 03 (Physical Sciences)


Improved circularly polarized antenna

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