What is it about?
This paper presents the design of a unique multimode extractor and converter of higher order modes of a circular waveguide. The multi-mode extractor couples first five circular waveguide propagation modes TE11, orthogonal TE11(o), TM01, TE21, and TE21(o) that includes the three tracking signals (i.e. sum signal, elevation signal, and azimuth signal) used in a high-frequency monopulse tracking system and two communication channels for transmitting and receiving signal at Ka band. This design is based on amplitude and phase characteristics of the higher-order modes TM01, TE21, and TE21(o) excited in circular waveguide. TE21 and TE21 (o) modes are extracted from circular waveguide to TE10 mode in rectangular waveguide by two longitudinal slots milled in the circular waveguide. TE11 mode is coupled using two coupling slots and H-plane power combiner. A turnstile junction is used to extract TM01 and TE11(o) mode. This multimode tracking system is designed both for linear or circular polarized ground earth station antennas to track orbiting satellites.
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Why is it important?
The antenna of the satellite must be pointed accurately toward the earth station antenna with which the satellite is in communication using a high-gain reflector antenna system. In order to achieve this accurate pointing, satellite antenna commonly employ tracking systems to provide signals indicative of the pointing errors in elevation and azimuth relative to the antenna beam of the earth station antenna. In tracking system three signals are used for the pointing accuracy of the satellite antenna. These three tracking signals are the azimuth difference signal, elevation difference signal, and the sum signal. The phase and amplitude characteristics of these three signals are utilized in a conventional manner to generate elevation angle error and azimuth angle error signals to control the pointing direction of the satellite antenna.
Perspectives
Typically, the tracking system on the satellite utilizes a monopulse-tracking configuration in which a plurality of antennas, feeding a reflector-system, is employed to develop three tracking signals indicative of the pointing accuracy of the satellite antenna. These three tracking signals are the azimuth difference signal, elevation difference signal, and the sum signal.
RF | Microwave | Antenna | Signal Integrity Engineer Anil Pandey
Keysight Technologies
Read the Original
This page is a summary of: Design of multimode tracking system for earth station antenna, December 2016, Institute of Electrical & Electronics Engineers (IEEE),
DOI: 10.1109/apmc.2016.7931301.
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