MICROWAVE HEATING APPARATUS COMPRISING SEMICONDUCTOR MICROWAVE OSCILLATOR

APPAREIL CHAUFFANT AUX MICRO-ONDES, AVEC OSCILLATEUR SEMICONDUCTEUR

English Abstract

ABSTRACT
This invention relates to a microwave heating
apparatus, wherein the output from a single semi-
conductor oscillator (1) is divided into two parts by
a power distributor, the parts are amplified by amplifiers
(3, 4), respectively, and the amplified parts are fed into
a heating chamber (7) by two antennas (A2, A3), the phase
of microwaves being adjusted to combine power in the
heating chamber (7).

Claims

- 5 -
CLAIMS:
1. A microwave heating apparatus using a semi-
conductor microwave generator wherein the output from
a single semiconductor oscillator is branched by a power
distributor, and the branched power parts are respective-
ly amplified by semiconductor amplifiers, the amplified
power parts being fed into a heating chamber by two
antennas provided on a single wall surface of the heating
chamber in such a manner that they are 180° out of phase
with each other.
2. A microwave heating apparatus as set forth in
Claim 1, wherein an in-phase distributor is used as
said power distributor, and a phase shifter for phase-
shifting microwaves by 180° is installed in one of the
microwave wires leading to the antennas.
3. A microwave heating apparatus as set forth in
Claim 1, using a power distributor wherein micro-
waves at the output ends differ in phase by 180°.
4. A microwave heating apparatus as set forth in
Claim 1, wherein the resonance mode in the heating
chamber has a standing wave (2, 0, 1) and two antennas
are installed at 1/4 and 3/4 positions, respectively, in
the x direction and at the middle in the z direction on
the x-z wall surface.

Description

SPECIFICATION
TITLE: Microwave Heating Apparatus
MECHANICAL FIELD
This invention relates to a microwave heating appa-
ratus wherein the output from a senliconductor microwave
oscillator is divided into two parts b~ a power distributor
and the parts are respectively amplified by power ampli-
fiers and microwaves are fed into a heating chamber by
two antennas. The invention is intend to control the
phase o microwaves to effect combination of power in
the heating chamber.
BRIEF DESCRIPTION OF T~IE DR~WINGS
Fig. 1 is a block diagram showing a conventional
semiconductor microwave generator;
Fig. 2 is a block diagram showing a microwave
heating apparatus according to this invention; and
Fig. 3 shows the positional relation between anten-
nas and a heating chamber in the prlncipal portion of
the apparatus.
BACKGROUND ART
Such a conventional apparatus, as shown in Fig. 1,
consists in distributing the output from a semiconductor
oscillator 1, i.e., distributing the output from a

- 2
terminal a be~ween terminals b and c on the same energy
level by a divider 2, respectively amplifying the parts
by semiconductor amplifiers 3 and 4, combining them by
a power combiner 5, and feeding the resultant to the
hea-ting chamber by a slngle antenna Al. In addition,
the powers from the terminals e and f are combined and
delivered from the terminal ~. The terminals d and h
are inte~connected at their terminal ends.
This arrangement, however, has such drawbacks as
requiring a heavy duty power combiner 5 and this producing
high power loss~
DISCLOSURE OF TIIE INVENTION
~ccordingly, the invention provides an arrangement
consisting in dividing the output from a single semi-
conduc-tor power oscillator into two parts by a power
distributor, respe~tively amplifying them by power
amplifiers, and feeding them by two antennas into a
heating chamber serving as an microwave resonator,
said heating chamber also serving as a power combiner,
thereby making the arrangement highly efficient and
inexpensive. An embodiment of the invention will now
be described with re~erence to the drawings.
~5 BEST MODE OF CARRYING OUT. THE INVENTION
In Fig. 2 the power from a semiconductor microwave
oscillator 1 enters the terminal a o a distributor

.. ~,
2 and. is equally distributed among and delivered from
the terminals b and c. The d terminal is ended at the
termination. In addition, the microwaves delivered
Erom th~ distributor 2 are, generally, in phase and 180
out of phase with each other at the terminals b and c.
The outputs from the distributor 2 are amplified by
semiconductor amplifiers 3 and 4 and fed to two antennas
A2 and A3. One of the two has a phase shifter 6 connected
thereto, as required for phase shift, in relation to a
heater to be described below.
Fig~ 3 shows the relation between the heating
chamber and the antennas. The heating chamber 7 is
defined by metal walls and serves as a cavity resonator
with respect to microwaves. The figure shows an example
of a standing wave mode (2, 0, 1), That is, standing
wave electric fields chanye in intensity by 2, 0 and 1
in the directions of x, y and z r respectively. In this
case, the antennas A2 and A3 are located at 1/4 and 3/4
positions in the _ direction and at the middle in the
z direction on the x-z plane, whereby microwave oscilla-
tion is effected in the highest intensity region of
electric field in the standing wave mode (2, 0, 1), so
that microwaves can be efficiently fed into the heating
chamber.
The outputs from the antennas are 1~0 out of phase
with each other because of the relation to the time phase
of the standing wave mode.

Let ~ be said phase, ~ be the propagation constant
and 1 be the distance from the power amplifier to the
antenna. Then, ~ = ~1 In order to obtain a phase
shift of 180, the power is fed to the antenna with the
use oE a phase shifter 6 if the distributor 2 is in
phase but without the use of a phase shifter if it is
180 out of phase.
INDUSTRIAL A:PPLICABI~ITY
As described above, according to the present inven-
tion, since combination of power is possible in the heating
chamber cavity even in the absence of a power combiner, it
is possible to avoid more than 10% of the power loss caused
where a power combiner is used.
While combination of high power is difficult to
achieve in the case of strip wires often used in semi-
conductor power systems because of problems of heat dissi-
pation and electric discharge, the invention basically
solves these problems.
Further, since antennas are provided on a single
wall surface, as compared with an arrangement providing
antennas on two separate wall surfaces, there are merits
that the ineffective volume of the heating chamber can be
reduced and that the arrangement of the microwave lines
for feeding power to the respective antenna is planar
and simple.