MWA Active Crossed-Dipole Antenna (used in the Murchison Widefield Array)
If you are interested in ordering the MWA crossed-dipole antenna described below, click here.
Description
The MWA active crossed-dipole antenna is a receive-only antenna with a design frequency range of 80 to 300 MHz. It complements the LWA active crossed-dipole antenna described here. Some of the original design documents for the MWA antenna system are available on request.
The MWA antenna is a vertically oriented bow-tie design with elements that consist of triangular wings or blades as shown immediately below. The antenna central hub contains a dual low noise amplifier (LNA) assembly. Each LNA is powered by 5 Vdc through its coaxial cable and a bias-tee arrangement.
In the Murchison Widefield Array, "Tiles" consisting of sixteen crossed-dipole antennas are installed on a ground screen and connected to a beam forming assembly (shown in foreground below). With the beamformer, the antennas may be steered up to 30 degrees from vertical. We have a limited supply of the beamformer hardware but cannot supply and do not support the software for controlling it.
Documentation
Transmission Line, Power and Protection Considerations
The dual low noise amplifier assembly in each crossed-dipole antenna is powered through individual bias-tees located at or near the receiver equipment. The MWAPC power coupler is used with one crossed-dipole assembly for single antenna installations (not tiles). The MWAPC can be equipped with or without a quadrature coupler for discrimination of polarization (see Applications for Circular Polarization below).
Applications for Circular Polarizations
A crossed-dipole antenna, such as the MWA antenna, can be setup to discriminate right-hand circular or left-hand circular polarization by combining the output of each dipole in a 90° hybrid coupler as shown below. For additional information, see Introduction to Radio Wave Polarization and Antenna Application for the Quadrature Coupler.
Our primary application for the active crossed-dipole antenna is reception of solar radio bursts, in which case we use the antenna with the CALLISTO instrument described here. When used with the CALLISTO instrument, the usable frequency range is 80 to 300 MHz.
If you are interested in ordering the MWA crossed-dipole antenna and associated active balun described above, click here.