Compact microstrip patch array used to radiate TE01 mode wave in circular waveguide

A compact microstrip patch annular array is proposed to excite the TE01 (TE, transverse electric) high-order mode in circular waveguide. This annular array is composed of four microstrip patches which are laid and fed rotationally. The electromagnetic simulation software, high-frequency structure simulator is used to model the electric field radiated by the annular array. It is found that the electric field is turbulent and according to the performance of the TE01 mode. A wireless transmitting and receiving experiment is carried out in a long steel hollow pipe to prove the existence of the TE01 mode. In this experiment, the transmit–receive antenna is selected as the proposed annular array and dipole antenna. It is shown that the transmission loss of the annular array is much less than the dipole.