Solid state microwave oven power source

• US 4,097,708 A
• Filed: 04/02/1976
• Issued: 06/27/1978
• Est. Priority Date: 08/13/1974
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Bickel, Samuel H.
• Primary Examiner(s): Grimley, Arthur T.
• Application Number:
  US05/673,024
• Time in Patent Office: 816 Days
• Field of Search: 219/10.55 R, 219/10.55 B, 219/10.55 F, 333/1.1, 333/84 R, 333/84 M, 333/95 A, 343/792.5, 343/799, 343/801
• US Class Current: 219/761
• CPC Class Codes: H03B 7/146 with several semiconductor devices
• CPC Class Codes: H03H 7/48 Networks for connecting several sources or loads, working on the same frequency or frequency band, to a common load or source phase shifters providing two or more output signals H03H7/21
• CPC Class Codes: H05B 6/6402 Aspects relating to the microwave cavity

Abstract

Disclosed is a solid state power source which combines the power of a plurality of negative resistance transistor packages in a circular cavity to form an oscillator producing a resonant source of microwave energy for radar or microwave energy oven applications. The power of the plurality of negative resistance transistor packages is fed to the cavity through a plurality of gapped coaxial cable antennae selectively positioned adjacent the circular cavity wall. The antennae terminate in an microwave energy termination and dc base biasing circuitry.

Claims

1. A solid state microwave power source comprising a plurality of solid state microwave oscillators and an equal phase power combiner and impedance matching network, said oscillators coupled to input ports of said power combiner whereby the power from each oscillator is coupled to an output port in phase with all the other of said oscillators.

2. A microwave power source comprising:

(a) a source of dc power;

(b) a plurality of negative resistance transistor packages, each negative resistance transistor package including a transistor and a capacitor, said transistor coupled to the source of dc power and capacitor for producing a negative driving point resistance;

(c) a plurality of microwave energy radiating elements;

(d) a cavity, said plurality of microwave radiating elements coupled to the plurality of negative resistance transistor packages and cavity for combining the outputs of the plurality of radiating elements and exciting the cavity in a single preselected mode of oscillation;

(e) microwave termination circuitry coupled to the said plurality of radiating elements to suppress unwanted modes of oscillation; and

(f) an output means coupled to the cavity for conducting the combined microwave energy from the cavity to provide a high power source of microwave energy.

3. A microwave power source according to claim 2 wherein each of said plurality of negative resistance transistor packages includes a transistor having its collector attached directly to a heat sink for grounding and decreasing the thermal resistance of the device thereby increasing heat dissipation capability.

4. A microwave power source according to claim 2 wherein said capacitor is connected between the emitter and base of the transistor for decreasing the base lead inductance and making the emitter base loop resonant and the negative resistance as viewed at the collector base output substantially at maximum.

5. A microwave power source according to claim 3 wherein the plurality of microwave energy radiating elements are gapped coaxial lines connected to the transistor output of the negative resistance transistor packages with the gaps selectively positioned within the cavity for radiating the microwave energy into the cavity.

6. A microwave power source according to claim 3 wherein the cavity is a circular symmetric cavity having a preselected radius for exciting a desired mode for a preselected frequency.

7. A microwave power source according to claim 6 wherein the circular symmetric cavity receives the plurality of microwave energy radiating elements at preselected distances from the sidewall thereof and includes a centrally disposed output probe for coupling power from the cavity into a 50 ohm line.

8. A microwave power source according to claim 5 wherein the plurality of gapped coaxial lines terminate in an microwave termination and dc base bias circuit, said microwave termination and dc base circuit including a dielectric attached to the cavity, a plurality of conductors interconnecting said plurality of gapped coaxial lines to a dc source of power, the dielectric and plurality of conductors forming a microstrip circuit for microwave termination and dc biasing for the transistors of the plurality of negative resistance transistor packages.

9. A microwave power source according to claim 8 wherein a ballast resistor is connected in series with the microstrip circuit for equalizing the current distribution of the transistors of the plurality of negative resistance transistor packages.

10. A microwave power source comprising:

(a) a source of dc power;

(b) a plurality of microwave energy coaxial antennas;

(c) an microwave termination and dc base biasing network said microwave termination and dc base biasing network connected to the plurality of microwave energy coaxial antennas;

(d) a circular cavity, said cavity housing adjacent its sidewalls the plurality of microwave energy coaxial antennas and having an output probe centrally disposed therein; and

(e) a plurality of transistor packages, each package including a transistor having a collector attached directly to a heat sink, an emitter coupled to the dc source of power, a base coupled to one of the plurality of microwave energy coaxial antennas, and dc base biasing network, and a capacitor connected between the base and emitter whereby the transistor has a negative resistance and the plurality of transistor packages and the cavity form an oscillator producing a source of microwave energy.