WAVEGUIDE STRUCTURE

• US 20080129409A1
• Filed: 11/27/2007
• Published: 06/05/2008
• Est. Priority Date: 11/30/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: NAGAISHI, Hideyuki, Shinoda, Hiroshi
• Granted Patent: US 7,884,682 B2
• Time in Patent Office: Days
• US Class Current: 333/34
• CPC Class Codes: H01P 5/107 Hollow-waveguide/strip-line transitions

Abstract

When a microstrip line is connected with a waveguide, there is a limit to reducing the connection loss by using only a matching box. We have discovered that in a transmission mode line transducer for converting between the TEM waves of the microstrip line and the TE01 waves of the waveguide, if the cross-sections of the microstrip line and the waveguide are substantially the same size, in the case of a 50Ω microstrip line when the characteristic impedance of the waveguide is about 80%, i.e., 40Ω, the line conversion loss can be optimized. Therefore, according to the present invention, the microstrip line is connected with the waveguide using a λ/4 matching box by means of a ridged waveguide having a low impedance and a length of λ/16 or less.

Claims

1. A waveguide structure comprising:

a microstrip line;

a standard waveguide; and

a transmission mode transducer provided therebetween,

wherein the transmission mode transducer comprising a waveguide transducer, and

wherein the characteristic impedance of the waveguide transducer is equal to or less than the characteristic impedance of the microstrip line.

2. The waveguide structure according to claim 1, wherein the transmission mode transducer is a line transducer connecting the microstrip line with the waveguide transducer at right angles.

3. The waveguide structure according to claim 1, wherein the transmission mode transducer is a line transducer connecting the microstrip line with the waveguide transducer horizontally.

4. The waveguide structure according to claim 1, wherein the waveguide transducer is a ridged waveguide.

5. The waveguide structure according to claim 4, wherein the length of the short side of a rectangular cross-section of the ridged waveguide is twice or less than twice the dielectric thickness of the microstrip line.

6. The millimeter waveband transceiver according to claim 2,

wherein the length of the short side of a cross-sectional opening of the ridged waveguide is twice or more than twice the thickness of a dielectric of the microstrip line,

wherein a ridge is provided near the center of one or both of the long sides of the ridged waveguide cross-section, projecting toward the center of the rectangle, wherein a distance of the nearest part of the opening is twice or less than twice the thickness of the dielectric, and

wherein the characteristic impedance of the ridged waveguide is equal to or less than the characteristic impedance of the microstrip line.

7. The waveguide structure according to claim 1,

wherein a λ

/4 matching box is connected between the transmission mode transducer and the standard waveguide, and

wherein the characteristic impedance of the λ

/4 matching box is a higher impedance than the characteristic impedance of the transmission mode transducer and microstrip line of the transmission mode transducer, and a lower impedance than the characteristic impedance of the standard waveguide.

10. The waveguide structure according to claim 1, the structure further comprising:

an RF circuit;

a standard waveguide constituting input/output terminals connecting to the outside;

a microstrip line constituting a millimeter waveband data line of the RF circuit; and

a λ

/4 matching box connected between the standard waveguide and the waveguide transducer,

wherein the characteristic impedance of the λ

/4 matching box is an intermediate value between the characteristic impedance of the microstrip line and the characteristic impedance of the standard waveguide.

11. The waveguide structure according to claim 10, the structure further comprising:

a multilayer substrate;

an RF circuit control board;

the RF circuit provided on the top layer of the RF circuit control board and the multilayer substrate; and

a waveguide transducer and the λ

/4 matching box of the transmission mode transducer provided in an inner layer of the multilayer substrate,

wherein the transmission mode transducer is formed of a transmission mode transducer wherein the microstrip line and waveguide transducer are connected at right angles.

12. The waveguide structure according to claim 1, further comprising:

a multilayer substrate;

an RF circuit control board;

the RF circuit provided on the top layer of the RF circuit control board and the multilayer substrate; and

a waveguide transducer and a λ

/4 matching box of the transmission mode transducer provided in an inner layer of the multilayer substrate,

wherein the waveguide transducer and the waveguide of the λ

/4 matching box are formed in a waveguide shape extending through to the undersurface of the multilayer substrate by alternately laminating a dielectric film and a metal conductor film, forming a punch-out pattern in the metal conductor films, and electrically connecting the metal conducting films via vias.

13. The waveguide structure according to claim 2,

wherein the transmission mode transducer has a ridged waveguide formed from ridges projecting near the centre of one or both of the long sides of the waveguide cross-section, and having a smaller characteristic impedance than that of the microstrip line,

wherein the ridged waveguide is formed in a multilayer substrate wherein a dielectric film and a metal conductor film are laminated alternately,

wherein the length of the ridged section is λ

/4 or less from the facet of the long side of the rectangular opening of the ridged waveguide, and

wherein a plurality of electrically conducting vias are disposed in the projection direction on the multilayer substrate.

14. The waveguide structure according to claim 12,

wherein the structure further comprising an impedance matching box having a characteristic impedance ratio of 3 or less at input and output terminals, formed on the multilayer substrate,

wherein a vertical transducer is connect to the impedance matching box at the input and output terminals, and

wherein the impedance matching box is an impedance matching box formed by a tapered artificial-waveguide having a length of λ

/4 or less with a taper angle satisfying the relation tan(θ

)/(√

(Er))<

0.3, and having a reflection characteristic of −

10 dB or less, on the multilayer substrate.

8. A waveguide structure, comprising:

a multilayer substrate, and

a heat transfer plate laminated on the multilayer substrate;

wherein, on the multilayer substrate, a microstrip line, a transmission mode transducer connected between the microstrip line and a standard waveguide, and a first λ

/4 matching box are provided,

wherein the characteristic impedance of the waveguide transducer of the transmission mode transducer is equal to or less than the characteristic impedance of the microstrip line,

wherein the characteristic impedance of the first λ

/4 matching box is a higher impedance than the characteristic impedance of the transmission mode transducer and microstrip line, and a lower impedance than the characteristic impedance of the standard waveguide, and

wherein a second λ

/4 matching box of a conductive conductor, having a lower impedance than the characteristic impedance of the standard waveguide, and a higher impedance than the characteristic impedance of the first λ

/4 matching box, is formed in the heat transfer plate.

9. The waveguide structure according to claim 8, wherein the first λ

/4 matching box is a tapered impedance matching box provided on the multilayer substrate.

15. A waveguide structure comprising:

a microstrip line;

a standard waveguide; and

a transmission mode transducer connected therebetween,

wherein the transmission mode transducer includes a waveguide transducer; and

wherein if the impedance of the microstrip line is Z₁, the impedance of the waveguide transducer is Z₂, and the impedance of the standard waveguide is Z₄, the waveguide structure is constituted so that the relation between these impedances satisfy the inequality;

Z₂≦

Z₁<

Z₄

16. The waveguide structure according to claim 15, the structure further comprising a λ

/4 matching box connected between the transmission mode transducer and the standard waveguide,

wherein, if the impedance of the λ

/4 matching box is Z₃, the waveguide structure is constituted so that the relation between these impedances satisfy the inequality;

Z₂≦

Z₁<

Z₃<

Z₄

17. The waveguide structure according to claim 16,

wherein the waveguide transducer has a ridged waveguide, and the length of the ridged waveguide is λ

/16 or less.

18. The waveguide structure according to claim 17,

wherein, if a ridged gap of the ridged waveguide is WR, the dielectric thickness of the microstrip line is MSLts, and a width of the microstrip line is WS, the length of the shorter side of the cross-section of the ridged waveguide is twice or more than twice the thickness MSLts of the dielectric of the microstrip line.

19. The waveguide structure according to claim 18,

wherein a ridge is provided near the center of one or both of the long sides of the ridged waveguide cross-section, projecting toward the center of the rectangle, wherein a distance of the nearest part of the opening is twice or less than twice the thickness MSLts of the dielectric.

20. The waveguide structure according to claim 19,

wherein a length Wh in the direction of the long side of the ridged waveguide cross-section is twice or less than twice the microstrip line width WS,

wherein the ridge that functions as the GND electrode of the microstrip line, a length WL in the direction of the long side of the ridged waveguide cross-section is three times or more than three times the microstrip line width WS, and

wherein the ridged gap WR is twice or less than twice the thickness of the dielectric forming the microstrip line.