Electronic oven with ferrite rf rejection filters

Claim 2

In an electronic heating apparatus adapted for use with a source of DC operating potentiAl having at least one terminal and with a source of low-frequency AC energy having at least one terminal, structure defining a cooking cavity, a generator for generating electromagnetic wave energy of a predetermined ultrahigh frequency and having a pair of output terminals, a transmission line coupling said generator to said cooking cavity, a hollow outer conductor coupled to one output terminal of said generator and extending outwardly therefrom and terminating in an outer end, an inner conductor disposed in said outer conductor and coupled to the other output terminal of said generator and extending outwardly therefrom and terminating in an outer end adjacent to the outer end of said outer conductor, an insulating sleeve disposed within said outer conductor in surrounding relationship with said inner conductor, means coupling the DC source terminal and the low-frequency AC source terminal to the outer end of said inner conductor, a ferrite filter element disposed in said inner conductor intermediate the outer end thereof and said generator output terminals and being constructed and arranged to operate as a section of lossy transmission line in the coaxial mode for providing high-transmission losses at selected harmonics of the predetermined frequency, and a conductive filter element disposed in said inner conductor in end-to-end relationship and longitudinal alignment with said ferrite filter element and connected thereto and being constructed and arranged to cooperate with said insulating sleeve and said outer conductor for providing a low-impedance bypass path between said inner and outer conductors at the predetermined frequency, whereby propagation of ultrahigh frequency energy at the predetermined frequency and selected harmonics thereof from the generator to the outer ends of said conductors is highly attenuated without interfering with the transmission of the DC operating potentials and the low frequency AC energy from the sources thereof to the generator.

Claim 3

The electronic heating apparatus set forth in claim 1, wherein said inner and outer conductors and said ferrite filter element are each cylindrical in shape and circular in cross section, the outer diameter of said ferrite filter element being such as to provide high attenuation of all of the harmonics of the predetermined frequency up to the seventh harmonic.

Claim 4

The electronic heating apparatus set forth in claim 1, wherein said inner and outer conductors and said conductive filter element are each cylindrical in shape and circular in cross section, the outer diameter of said conductive filter element being such as to provide a capacitive bypass path between said inner and outer conductors at the predetermined frequency.

Claim 5

The electronic heating apparatus set forth in claim 1, wherein said inner and outer conductors and said ferrite filter element and said conductive filter element are all cylindrical in shape and circular in cross section, the outer diameters of said ferrite filter element and said conductive filter element being substantially equal to each other.

Claim 6

The electronic heating apparatus set forth in claim 1, wherein said outer conductor overlaps said conductive filter element a distance not greater than one-quarter of the wavelength of the predetermined frequency.

Claim 7

The electronic heating apparatus set forth in claim 1, wherein said inner conductor comprises an externally threaded rod, said ferrite filter element and said conductive filter element each being cylindrical in shape and having an internally threaded opening extending axially therethrough, said inner conductor being threadedly engaged with the internally threaded openings through said ferrite filter element and said conductive filter element for coupling said filter elements to said inner conductor.

Claim 8

In an electronic heating apparatus adapted for use with a source of DC operating potential having at least one terminal and with a source of low-frequency AC energy having a pair of terminals, structure defiNing a cooking cavity, a generator for generating electromagnetic wave energy of a predetermined ultrahigh frequency and having a pair of output terminals and a low-frequency AC input terminal, a transmission line coupling said generator to said cooking cavity, a first hollow outer conductor coupled to one output terminal of said generator and extending outwardly therefrom and terminating in an outer end, a first inner conductor disposed in said outer conductor and coupled to the other output terminal of said generator and extending outwardly therefrom and terminating in an outer end adjacent to the outer end of said outer conductor, a first insulating sleeve disposed within said outer conductor in surrounding relationship with said inner conductor, means coupling the DC source terminal and the low-frequency AC source terminal to the outer end of said inner conductor, a first ferrite filter element disposed in said inner conductor intermediate the outer end thereof and said generator output terminals and being constructed and arranged to operate as a section of lossy transmission line for providing high-transmission losses at selected harmonics of the predetermined frequency, a first conductive filter element disposed in said inner conductor in longitudinal alignment with said ferrite filter element and connected thereto and being constructed and arranged to cooperate with said insulating sleeve and said outer conductor for providing a low-impedance bypass path between said inner and outer conductors at the predetermined frequency, a second hollow outer conductor coupled to said one output terminal of said generator and disposed adjacent to said low-frequency AC input terminal and extending outwardly therefrom and terminating in an outer end, a second inner conductor disposed in said second outer conductor and coupled to said low-frequency AC input terminal of said generator and extending outwardly therefrom and terminating in an outer end adjacent to the outer end of said outer conductor, a second insulating sleeve disposed within said second outer conductor in surrounding relationship with said second inner conductor, means coupling the other of said low-frequency AC source terminals to the outer end of said second inner conductor, a second ferrite filter element disposed in said second inner conductor intermediate the outer end thereof and said generator low-frequency AC input terminal and being constructed and arranged to operate as a section of lossy transmission line for providing high-transmission losses at selected harmonics of the predetermined frequency, and a second conductive filter element disposed in said second inner conductor in longitudinal alignment with said second ferrite filter element and connected thereto and being constructed and arranged to cooperate with said second insulating sleeve and said second outer conductor for providing a low-impedance bypass path between said second inner and outer conductors for the predetermined frequency, whereby propagation of ultrahigh frequency energy at the predetermined frequency and harmonics thereof from the generator to the outer ends of said first and second conductors is highly attenuated without interfering with the transmission of the DC operating potentials and the low-frequency AC energy from the sources thereof to the generator.

Claim 9

In an electronic heating apparatus adapted for use with a source of DC operating potential having at least one terminal and with a source of low-frequency AC energy having a pair of terminals, structure defiNing a cooking cavity, a generator for generating electromagnetic wave energy of a predetermined ultrahigh frequency and having a pair of output terminals and a low-frequency AC input terminal, a transmission line coupling said generator to said cooking cavity, a first hollow outer conductor coupled to one output terminal of said generator and extending outwardly therefrom and terminating in an outer end, a first inner conductor disposed in said outer conductor and coupled to the other output terminal of said generator and extending outwardly therefrom and terminating in an outer end adjacent to the outer end of said outer conductor, a first insulating sleeve disposed within said outer conductor in surrounding relationship with said inner conductor, means coupling the DC source terminal and the low-frequency AC source terminal to the outer end of said inner conductor, a first ferrite filter element disposed in said inner conductor intermediate the outer end thereof and said generator output terminals and being constructed and arranged to operate as a section of lossy transmission line for providing high-transmission losses at selected harmonics of the predetermined frequency, a first conductive filter element disposed in said inner conductor in longitudinal alignment with said ferrite filter element and connected thereto and being constructed and arranged to cooperate with said insulating sleeve and said outer conductor for providing a low-impedance bypass path between said inner and outer conductors at the predetermined frequency, a second hollow outer conductor coupled to said one output terminal of said generator and disposed adjacent to said low-frequency AC input terminal and extending outwardly therefrom and terminating in an outer end, a second inner conductor disposed in said second outer conductor and coupled to said low-frequency AC input terminal of said generator and extending outwardly therefrom and terminating in an outer end adjacent to the outer end of said outer conductor, a second insulating sleeve disposed within said second outer conductor in surrounding relationship with said second inner conductor, means coupling the other of said low-frequency AC source terminals to the outer end of said second inner conductor, a second ferrite filter element disposed in said second inner conductor intermediate the outer end thereof and said generator low-frequency AC input terminal and being constructed and arranged to operate as a section of lossy transmission line for providing high-transmission losses at selected harmonics of the predetermined frequency, and a second conductive filter element disposed in said second inner conductor in longitudinal alignment with said second ferrite filter element and connected thereto and being constructed and arranged to cooperate with said second insulating sleeve and said second outer conductor for providing a low-impedance bypass path between said second inner and outer conductors for the predetermined frequency, whereby propagation of ultrahigh frequency energy at the predetermined frequency and harmonics thereof from the generator to the outer ends of said first and second conductors is highly attenuated without interfering with the transmission of the DC operating potentials and the low-frequency AC energy from the sources thereof to the generator.

Claim 10

The electronic heating apparatus set forth in claim 7, wherein said first ferrite filter element is identical in construction to said second ferrite filter element, and wherein said first conductive filter element is identical in construction to said second conductive filter element.