2.10     Dual-mode horn antenna

Consider Standard/Dmhorn/dm_horn.pro, which is an example of dual-mode axisymmetrical horn antenna [M7] as shown in the Fig. 2.10-1. Input of the antenna is excited with the fundamental mode TE11 of 10..14 GHz spectrum range. However, as the wave propagates through the tapered section, some of its energy is transformed into TM11 mode. Thus, an appropriate design allows us to equalise polarisation in E and H planes. It makes this horn a good feed for reflector antennas. Additionally, proper choices of flare angle and length of the horn’s tube help suppress the side lobes in the radiation pattern (see Fig. 2.10-2). Changing Gain Reference in the Results window from Relative to Directive we see that the gain of this antenna is about 14.5 dB for both E and H planes. The 3 dB beamwidth is 35.4⁰ and 37⁰ for the E and H plane, respectively.

Fig. 2.10-1 QW-Editor view of  dm_horn example.

Fig. 2.10-2 Radiation pattern for dm_horn example.

Fig. 2.10-3 3D Radiation pattern for dm_horn example.

Sinusoidal excitation of the model at the central frequency (f = 12 GHz) shown in the Fig. 2.10-4 confirms that the same radiation levels at both E and H planes are obtained at the end of the antenna.

Fig. 2.10-4 Poynting vector for dm_horn_sin example.