STUDY OF A LEAKY WAVEGUIDE ON HEATING MORTAR BLOCK SYSTEM FOR MELTING SNOW THROUGH QUASI MICROWAVES

Abstract

The apparatus with electromagnetic waves of frequency 2.45GHz, such as microwave ovens, are mass-produced, therefore an oscillator for the electromagnetic wave of frequency 2.45GHz is inexpensive. We study the heating mortar block system using oscillator of frequency 2.45GHz for melting snow to convert an electromagnetic wave into heat. The heating mortar block system can melt snow in a shorter time than systems with electric heating wires. The heating mortar block system for melting snow needs to be composed of a leaky waveguide for providing electromagnetic waves to the heating mortar blocks. The leaky waveguide has many slots emitting electromagnetic waves on the top surface. In this study, the influences that the figure of the slots gives to quantity of emitted electromagnetic waves are confirmed. First, the characteristic of the single slot on a metal board about emitted electromagnetic waves was confirmed by the S parameter. The metal board that a slot was installed in is connected to a coaxial waveguide, and return loss is measured. When a slot grows longer in the direction inhibiting the electric current in the leaky wave guide, return loss greatly changed. The slot with 60mm long emitted most electromagnetic waves. This length is equal to a half wavelength of the electromagnetic wave of 2.45GHz in the free space. Second, the characteristic regarding emitted electromagnetic waves of the slots that were arranged continually on a leaky waveguide was confirmed by equipment measuring quantity of emitted electromagnetic waves on the leaky waveguide. The equipment measuring the quantity of emitted electromagnetic wave on a leaky waveguide is composed of electromagnetic waves oscillator, a leaky waveguide and a coaxial waveguide converter with the metal board that a slot was installed in. The slot that emitted the most electromagnetic waves on the metal board is 60mm long. Electromagnetic waves that emitted out from each slot on a leaky waveguide is received in a coaxial waveguide converter with the metal board that the slot was installed in. When the length of the slot on the leaky waveguide was 30mm, quantity of emitted electromagnetic waves is stable. In addition, emitted electromagnetic waves have the period that depend on the wavelength in the leaky waveguide when they are reflected in the terminal of the leaky waveguide. However, when they are absorbed in the terminal of the leaky waveguide, the period of emitted electromagnetic waves is lost. This is because there are no stationary waves since there are no reflection waves. The ability of the heating mortar block system for melting snow was confirmed by melting snow piled up in Tsuruoka city, Yamagata prefecture. The heating mortar block system is composed of electromagnetic waves oscillator, leaky waveguide and heating mortar blocks. The slots that emitted electromagnetic waves stably on leaky waveguide is 30mm long. In addition, the rest of electromagnetic waves are emitted at the terminal of the leaky waveguide by the slot of 60mm long. As a result, the heating mortar block system for melting snow has ability of melting snow. However, the heating mortar blocks did not have the equal temperature rise under the influence of the dielectric constant of themselves. It is necessary to make a space between a leaky waveguide and the heating mortar blocks for the equal temperature rise.