Biconical antennas consist of two cone-shaped elements that can send and receive signals across a broad range of frequencies. They are often used for electromagnetic interference testing and have a symmetrical design that allows for consistent test repeats. They are versatile and can be used in various applications, including terrestrial and mobile platforms and in the air.
A biconical antenna is a conductor that can send and receive signals from two arrays of cone-shaped elements that extend across from each other. It is typically hourglass shaped, as both conductors have a common axis and balun. These broadband dipole antennas operate in the 30 to 300 megahertz (MHz) range, although 20 MHz to 3 gigahertz (GHz) ranges are possible. They can have bandwidths of three or more octaves.
Biconical antennae, sometimes called bicones, are essentially two touching cones with a common central axis. Each cone applies excitation to its vertex, or point. These components can be driven by electronic charges, alternating potentials or magnetic fields, and currents at the apex. When a single cone is angled in one plane, or 180 degrees, it is called a discone.
Available as small, large, portable, or fixed antennas, bicons typically consist of conductive elements that fan out from a balun. A balun, short for balance/unbalance, is a transformer coupling that converts current balances to smooth impedance, which refers to the relationship between current, voltage, resistance, and their effects on the radiation pattern of the antenna. The balun helps determine the radiation pattern and efficiency of the antenna. The elements radiate symmetrically from their support, although cylindrical and star-shaped varieties exist.
Often, the biconical antenna is used to test for electromagnetic interference (EMI), immunity or emissions. These tests occur at 25-200 MHz for commercial applications and 30-200 MHz for military. Dipole and Yagi arrays indicate higher field strengths than a simple biconical antenna; the bicon is less efficient but has broadband. Simple conical monopoles and bowtie antennas, wire approximations of the biconical type, have higher bandwidth than monopoles. High-gain antennas usually have higher signal strength, while low-gain varieties like bicon transmit over a wider angle.
With the conductors radiating from a central point in opposite directions, the design makes the biconical antenna suitable for conducting sweep measurements and conformance tests. It is also useful for maintenance of automated antenna measurement systems. Its advantage over measurements of vertical site attenuation, or signal loss, is attributed to its long dipole element lengths at lower frequencies: for example, 16.4 feet (about 5 m) at 30 MHz.
Some models allow for both vertical and horizontal attenuation measurement scans. The bicon’s symmetrical design allows for more consistent test repeats, as the antenna is unaffected by how it is rotated. With such applications, manufacturers sometimes provide calibration data for measurement standards; for example, antenna gain and factor versus frequency.
Typically, the radiation pattern of a biconical antenna appears similar to that of dipole antennas, with a field pattern extending into two opposite lobes. These models operate virtually independent of frequency. Common applications include use in areas requiring omnidirectional radiation, as well as emission test facilities; they perform service on terrestrial and mobile platforms and in the air. The smaller size allows for versatile portable uses, as these antennas tend to be light in weight and easily installed.
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