Horn antennaHorn antenna is one of the types of combined antennas. Their shape defines the name. Such antennas consist of a flare, a horn, and a waveguide connected to its narrow end.Radiation patterns of horn antennas depend on their size and the shape of inside and outside section of a horn. There is no back lobe. Pattern bandwidth is defined by a waveguide used in the antenna. In fact, such antenna is designed for a broad bandwidth of microwaves: approximately from one to several dozens of GHz.There are several types of antennas distinguished on the basis of its shape: N and T sector antennas, pyramidal antennas, antennas with a rectangular cross-section, conical antennas, and antennas with a round flare. Shape matters. The most widespread pyramidal antennas have a linear polarization of radiation, and conical antennas have a circular polarization.Horn antennas are used independently as a radiant for data transmission as well as together with a mirror antenna as irradiators. In practice, horn antennas are widely used in spacecrafts.There are some disadvantages of such antenna. Directional diagram width depends on the physical size of antenna. In order to get beam radiation antennas are made with a long horn. It's better when it is in proportion to an aperture square, i.e. of a peak cross-section LH or LE, and a directional diagram width is in inverse proportion to LH or LE in the first power.Therefore in order to make a directional diagram N times narrower the aperture width must be broadened by N times and the horn must be lengthened by N2 times. The horn must be excessively lengthened to get a higher gain which is very inconvenient. In this case mirrors and lenses are used in the horn aperture.Use of a horn as an irradiator of a parabolic antenna presents a whole new device which is distinguished for its narrow directional diagram and low level of side lobes.
