In-line microwave warming apparatus

1. Microwave warming apparatus comprising

a housing defining a heating waveguide having a pair of opposite electrically conductive end walls and electrically conductive longitudinal walls extending between the end walls, said walls enclosing a heating cavity;

an integral electrically conductive ridge projecting from one of the longitudinal walls and extending along the waveguide between the end walls;

a slot having opposite ends and extending from the outside through said one longitudinal wall and said ridge into the heating cavity, said slot being adapted to receive a cartridge containing a tube so that the tube extends through the slot into the heating cavity;

means for coupling electromagnetic energy having a selected heating frequency into the heating waveguide to heat the contents of the tube;

a first receiving waveguide extending inside said ridge adjacent to the slot so that when the cartridge is received in the slot, the first receiving waveguide can pick up thermal radiation emanating from a first segment of the tube and produce a corresponding waveguide-generated signal, and

a radiometer that operates at a selected detection frequency and is responsive to the waveguide-generated signal for producing a corresponding temperature signal.

2. The apparatus defined in claim 1 wherein the first receiving waveguide has an inner end located adjacent to the slot and extends along the ridge to a first transition located outside the heating cavity, said first transition being in circuit with the radiometer.

3. The apparatus defined in claim 2 wherein the first transition is a waveguide-to-strip-line transition.

4. The apparatus defined in claim 2 wherein the radiometer comprises a microwave integrated circuit (MIC).

5. The apparatus defined in claim 2

wherein the inner end of the first receiving waveguide is adjacent to one end of the slot, and

further including a second receiving waveguide extending inside the ridge and having an inner end located adjacent to the opposite end of the slot, said second receiving waveguide being similar to the first receiving waveguide and extending to a second transition located outside the heating cavity, said second transition being in circuit with the radiometer.

6. The apparatus defined in claim 5 and further including

a microwave integrated circuit (MIC) in the housing, said microwave integrated circuit including said radiometer, and a switch for connecting the first and second transitions alternately to the radiometer, and

a controller in the housing for switching the switch.

7. The apparatus defined in claim 5 wherein each of the first and second receiving waveguides includes a first leg which extends along the ridge to an E-Plane bend and a second leg which extends from said bend through said one longitudinal wall to the corresponding one of said transitions.

8. The apparatus defined in claim 7 wherein

said bend is a 45° bend, and

the first and second receiving waveguides are substantially filled with a dielectric material.

9. The apparatus defined in claim 5 and further comprising a cartridge received in said slot, said cartridge including

a tube loop having an inlet, an outlet and spaced-apart parallel coplanar legs connected by a connecting segment, said tube loop being shaped and dimensioned so that when the cartridge is received in the slot, one leg of the tube is adjacent to one end of the slot and the other leg of the tube is adjacent to the opposite end of the slot, both legs extending into the heating cavity, and

a flat, relatively rigid support member having upper and lower ends and spaced-apart parallel side walls secured to said legs to maintain the shape of the tube loop.

10. The apparatus defined in claim 9 and further including an interior recess in a longitudinal wall of the heating waveguide opposite the slot, said recess being dimensioned to receive said connecting segment so that the connecting segment is outside the heating cavity.

11. The apparatus defined in claim 9 wherein the tube legs are spaced apart a quarter wavelength or multiple thereof at said heating frequency.

12. The apparatus defined in claim 9 wherein

the opposite side walls of the support member have first and second notches located directly opposite said inner ends of the first and second receiving waveguides, respectively, and

said first and second notches have walls which are electrically conductive and together with the first and second receiving waveguides comprise first and second transducers, respectively.

13. The apparatus defined in claim 12 wherein

the spacing of the inner ends of the first and second receiving waveguides is less than the length of the slot so that each receiving waveguide has a segment which brackets the slot and extends to the corresponding notch in the cartridge so that the walls of each notch form part of the adjacent one of the first and second receiving waveguides.

14. The apparatus defined in claim 9 wherein

the housing includes an exterior promontory projecting from said one longitudinal wall, said promontory having electrically conductive surfaces bordering the opposite ends of said slot;

a segment of the support member above said heating cavity has conductive surfaces, and

the heights of the promontory and the support member are selected so that together they form circular waveguides around the tube loop legs above said heating cavity which function as two-way filters at said heating and detection frequencies to prevent passage of electromagnetic radiation through said slot.

15. The apparatus defined in claim 1 and further comprising a cartridge in the slot, said cartridge including

a tube having a first segment;

a support member having a wall supporting the tube so that said first tube segment extends through the slot and past the first receiving waveguide into the heating cavity, and

a notch in said wall adjacent to the first tube segment, said notch being located directly opposite an inner end of the first receiving waveguide and having electrically conductive walls, said walls and the first receiving waveguide constituting a first transducer.

16. The apparatus defined in claim 15 wherein the notch and said inner end of the first receiving waveguide constitute a first transducer which brackets the first tube segment.

17. The apparatus defined in claim 16

further including a second transducer at the opposite end of the slot, said second transducer being similar to said first transducer, and

wherein the tube includes a second segment which extends past the second transducer into the heating cavity.

18. The apparatus defined in claim 15 wherein

the housing has an electrically conductive exterior wall extending up from said one longitudinal wall adjacent to the first tube segment, and

the support member includes an upper segment that extends above the slot opposite said exterior wall and has electrically conductive surfaces so that the upper segment and exterior wall together form a circular waveguide around the first tube segment above the slot that is tuned to function as a two-way filter at said heating and detection frequencies.