IEEE - Aerospace and Electronic Systems - May 2020 - 34

Multifrequency Spaceborne Deployable Radiometer Antenna Designs

Figure 16.
Beam alignment measurement using telescope.

adjacent to the source horn when the OA is alignment with
the positioner, then another spot (spot 2 in Figure 16) is
marked when the OA received the largest power level (at
least three times for searching, the final position of spot is
the mean square root of the three positions). The measurement procedure is monitored by a telescope. The beam
alignment is measured by the division of the two spots distance by distance (L) of the source horn and AUT in the
far-field system. The test result showed that the beam
alignment is 0.04o. Besides, the antenna successfully
passes through the vibration and thermal vacuum test.

Figure 17.
ACMR calibration corrugated horns.

and the whole antenna's beam alignment verify the simulations. Simulations and measurements also showed that
the antenna has MBEs above 90% for the three frequencies. Prelaunch calibration experiments have satisfactory
results of the ACMR, and thermal vacuum and vibration
tests confirm the antenna structure design for space use.

REFERENCES
ACMR CALIBRATION ANTENNA
The three dual-polarization calibration corrugated horn
antennas are displayed in Figure 17. These horn antennas
are designed with a beam width of 15 for three bands,
respectively, test results agree well with those of simulations. Measurements also showed that the voltage standingwave ratios (VSWRs) are less than 1.2 throughout the
working frequency bands.
To have precise calibration result, ACMR prelaunch
calibration experiments were carried out in a vacuum
chamber to eliminate the uncertainness of the components
in each path. The sensitivity and error of the ACMR are
calculated with calibration test data when the receiver
temperature is 291 K at all frequency bands. In view of
the impact of other factors, the ACMR system calibration
accuracy is 0.32 K for 18.7 GHz.

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[7] S. Brown, "Maintaining the long-term calibration of the
Jason-2/OSTM advanced microwave radiometer through
intersatellite calibration," IEEE Trans. Geosci. Remote

CONCLUSION

Sens., vol. 51, pp. 1531-1543, Mar. 2013.

Mechanical and electrical design of the tri-band dual
polarizations deployable dish and calibration antenna are
presented in this article. The curved corrugated horn is
selected to reduce the horn length and maintain the phase
centers of three bands are as close as possible to the horn's
aperture. Axial and lateral offset influence on the antenna
patterns is also analyzed. Thermal stable CFRP material is
utilized for the antenna dish and frame to reduce the thermal deformation. Deployment with error analysis of the
antenna is performed by software. Measurement of the
antenna showed that the SLLs of the OA are all lower
than À20 dB at all frequency bands, and the VSWRs are
also lower than 1.5 throughout the corresponding frequencies. In addition, measurement of the horn's phase centers
34

[8] L. Peters, "Corrugated horns for microwave antennas,"
IEEE Antennas Propag. Soc. Newslett., vol. 27, no. 2,
pp. 23-23, Apr. 1985.
[9] J. Uher et al., Waveguide Components for Antenna Feed
Systems: Theory and CAD. London, U.K.: Artech House,
1993.
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J. A. Ruiz-Cruz, J. R. Montejo-Garai, and J. M. Rebollar,
"Development of a wideband compact orthomode transducer for the 180-270 GHz band," IEEE Trans. Terahertz
Sci. Technol., vol. 4, no. 5, pp. 634-636, Sep. 2014.
[11] A. Navarrini and R. L. Plambeck, "A turnstile junction

IEEE A&E SYSTEMS MAGAZINE

waveguide orthomode transducer," IEEE Trans. Microw.
Theory Techn., vol. 54, no. 1, pp. 272-277, Jan. 2006.

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