US 8,173,943 B2Granted

Apparatus for microwave heating of a planar product including a multi-segment waveguide element

AssigneeRaute Oyj

InventorsPete Ristola, Jaakko Vilo, Jerzy Piotrowski

Life of this patent

Estimating the term…

Loading patent…

Abstract

The invention relates to a microwave waveguide element for matching a standard waveguide input port to an enlarged waveguide output port. In the waveguide element, a plurality of intermediate waveguide segments is cascaded in the propagation direction of the microwave energy to first split the waveguide element into two symmetrical waveguide branches and then combine the branches at the output port. Thus, the width of the waveguide element is gradually enlarged and the input port is matched to the output port. The intermediate waveguide segments are preferably dimensioned such that respective characteristic impedances are approximately matched with each other for the fundamental mode.

Claims9

Dependent claims

A waveguide element, wherein the waveguide element is in form of a rectangular pipe made of electrically conducting material, the waveguide element comprising

an input port having a standard rectangular cross-section with the width of the input port being bA in a direction of an electric field of the fundamental mode propagating in the waveguide element, the direction of the electric field being perpendicular to a propagation direction of a microwave power,
an output port having an enlarged rectangular cross-section, the width of the output port being C*bA in the direction of the electric field of the fundamental mode, wherein C is an enlargement factor greater than one,
a plurality of intermediate waveguide segments cascaded in the propagation direction of the microwave power and arranged to split the waveguide element into two symmetrical waveguide branches which are combined at the output port, the waveguide branches terminating to symmetrical horn-shaped waveguide segments of width C*bA/2 which are arranged to open to the output port, and wherein each one of the intermediate waveguide segments comprise
a first intermediate waveguide segment having width bB in the direction of the electric field of the fundamental mode, wherein bB>bA,
a second intermediate waveguide segment having width bC in the direction of the electric field of the fundamental mode, wherein bC>bB,
third and fourth intermediate waveguide segments located in parallel to each other with a spacing bG to form first segments of said symmetrical waveguide branches, the third and fourth intermediate waveguide segments each having width bD in the direction of the electric field of the fundamental mode, wherein (2*bD+bG)>bC.

3 more elements

An apparatus for microwave heating of a planar product, said apparatus comprising

i) a first waveguide element in form of a rectangular pipe made of electrically conducting material,
the first waveguide element further comprising
an input port having a standard rectangular cross-section with the width of the input port being bA in a direction of an electric field of the fundamental mode propagating in the waveguide element, the direction of the electric field being perpendicular to a propagation direction of a microwave power,
an output port having an enlarged rectangular cross-section, the width of the output port being C*bA in the direction of the electric field of the fundamental mode, wherein C is an enlargement factor greater than one,
a plurality of intermediate waveguide segments cascaded in the propagation direction of the microwave power and arranged to split the waveguide element into two symmetrical waveguide branches which are combined at the output port, the waveguide branches terminating to symmetrical horn-shaped waveguide segments of width C*bA/2 which are arranged to open to the output port, and wherein each one of the intermediate waveguide segments comprise
a first intermediate waveguide segment having width bB in the direction of the electric field of the fundamental mode, wherein bB>bA,
a second intermediate waveguide segment having width bC in the direction of the electric field of the fundamental mode, wherein bC>bB,
third and fourth intermediate waveguide segments located in parallel to each other with a spacing bG to form first segments of said symmetrical waveguide branches, the third and fourth intermediate waveguide segments each having width bD in the direction of the electric field of the fundamental mode, wherein (2*bD+bG)>bC,
ii) a feeding waveguide having said standard rectangular cross-section and being connected to said input port of the first waveguide element, and
iii) a heating cavity having said second rectangular cross-section and being connected to said output port of the first waveguide element.

7 more elements

Dependencies are inferred from the claim text.