Waveguide/microstrip mode transducer

• US 4,673,897 A
• Filed: 10/08/1985
• Issued: 06/16/1987
• Est. Priority Date: 04/26/1982
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Chua, Lye-Whatt, Gibson, Peter J.
• Primary Examiner(s): LaRoche, Eugene R.
• Assistant Examiner(s): Lee, Benny
• Application Number:
  US06/787,002
• Time in Patent Office: 616 Days
• Field of Search: 333/26, 333/21 R, 333/21 A, 333/33, 333/34, 333/246, 333/248
• US Class Current: 333/26
• CPC Class Codes: H01P 5/107 Hollow-waveguide/strip-line transitions

Abstract

A waveguide/microstrip mode transducer operable over a broad frequency range comprises a dielectric substrate (3) extending along an E-plane of a waveguide and having a conductive layer on each major surface, the two layers having three successive pairs of portions. A first pair (10, 11) form a microstrip line, a second pair (12, 13) form a balanced transmission line, and a third pair (14, 15) couple the portions (14, 15) of the balanced line to opposite walls (6, 7) of the waveguide. The microstrip line is coupled to the balanced line in a manner which is independent of frequency over the operating frequency range, rather than by a resonant balun; the strip conductor portion (10) and the ground plane conductor portion (11) of the microstrip line respectively are the same width as, and taper smoothly to the width of, the conductor portions (12, 13) of the balanced line connected thereto, and there are two regions (22, 23) respectively on opposite sides of the balanced line in which there is no conductor on both surfaces of the substrate (3 ) and which exhibit no resonance in the operating frequency range. In order to provide phase velocity matching between the waveguide and the transmission lines on the substrate (3), particularly when the substrate (3) has a high dielectric constant, the substrate (3) has a recess (24) of progressively increasing width along the waveguide.

Claims

1. A waveguide/microstrip mode transducer comprising:

(a) a length of waveguide having opposing first and second inner walls defining an E-plane extending perpendicularly thereto;

(b) a flat substrate sheet disposed in the E-plane, said flat substrate sheet extending from a first end to a second end thereof along the length of the waveguide and extending between the first and second opposing inner walls of the waveguide; and

(c) first and second conductive layers disposed on opposite flat sides of the flat substrate sheet, each conductive layer having an inner and an outer boundary defining therebetween the width of said layer;

said mode transducer comprising, from the first to the second ends of the flat substrate sheet, successive first, second, third, and fourth sections including;

(1) a first section where the first and second conductive layers each continuously increase in width with distance from the first end of the flat substrate sheet, the outer boundary of each of said first and second layers extending to and contacting a respective one of the waveguide'"'"'s first and second inner walls, and the inner boundary of each of said layers, with distance from said first end, gradually approaching a central longitudinal line of said substrate sheet;

(2) a second section where the first and second conductive layers each continuously decrease in width with distance from the first end of the flat substrate sheet, the outer boundary of each of said first and second layers being spaced from a respective one of the the waveguide'"'"'s first and second inner walls by a distance which increases with distance from said first end, and the inner boundary of each of said layers, with distance from said first end, continuing to approach the central longitudinal line until said first and second conductive layers overlie one another;

(3) a third section where the first and second conductive layers comprise bands covering respective areas in the centers of opposite sides of the flat substrate sheet, thereby forming a balanced transmission line; and

(4) a fourth section where the first conductive layer continues as a band extending along the center of the flat substrate sheet to the second end of said substrate sheet, and where the second conductive laye gradually increases in width with distance from the first end of the substrate sheet until said width extends from the first to the second inner wall of the waveguide;

said first and second conductive layers being shaped in the third section, and in at least part of the second and fourth sections, to define conductor-free areas on opposite sides of the balanced transmission line extending from each of the first and second waveguide walls to the nearest one of said conductive layer boundaries, said conductor-free areas being dimensioned to avoid resonances in the operating frequency range of the waveguide.

3. A mode transducer as in claim 1 or 2 where the width of the first conductive layer in the fourth section is equal to its width in the third section.

4. A waveguide/microstrip mode transducer as in claim 1 or 2 where said waveguide is a rectangular waveguide.

5. A mode transducer as in claim 1 where the widths of the portions the first and second conductive layers in the third section are substantially equal.

6. A mode transducer as in claim 1 where the first and second conductive layers in the first and second sections are symmetrically disposed with respect to a plane perpendicularly-intersecting the flat substrate sheet along said central longitudinal line.

7. A mode transducer as in claim 1 where the flat substrate sheet, in the first section, includes an opening disposed between areas thereof covered by the first and second conductive layers, said opening having a width which gradually decreases to zero with distance from the first end of said flat substrate sheet.

8. a mode transducer as in claim 7 where said opening extends to a maximum width at said first end of the flat substrate sheet.

9. A mode transducer as in claim 7 where the flat substrate sheet has a dielectric constant substantially greater than 3.

2. A waveguide/microstrip mode transducer comprising:

(a) a length of waveguide having opposing first and second inner walls defining an E-plane extending perpendicularly thereto;

(b) a flat substrate sheet disposed in the E-plane, said flat substrate sheet extending from a first end to a second end thereof along the length of the waveguide and extending between the opposing first and second inner walls of the waveguide; and

(c) first and second conducive layers disposed on opposite flat sides of the flat substrate sheet, each conductive layer having an inner and an outer boundary defining therebetween the width of said layer;

said mode transducer comprising, from the first to the second ends of the flat substrate sheet, successive sections including;

(1) a coupling section wheere the first and second conductive layers each continuously increase in width with distance from the first end of the flat substrate sheet, the outer boundary of each of said layers extending to and contacting a respective one of the waveguide'"'"'s first and second inner walls, and the inner boundary of each of said layers, with distance from said first end, gradually approaching a central longitudinal line of said substrate sheet;

(2) an impedance transformer/polarization twister section where the first and second conductive layers each continuously decrease in width with distance from the first end of the flat substrate sheet, the outer boundary of each of said first and second layers being spaced from a respective one of the waveguide'"'"'s first and second inner walls by a distance which increases with distance from said first end, and the inner boundary of each of said layers, with distance from said first end, continuing to approach the central longitudinal line until said first and second conductive layers overlie one another;

(3) a balanced transmission line section where the first and second conductive layers comprise bands of equal width covering areas in the centers of opposite sides of the flat substrate sheet, thereby forming a balanced transmission line;

(4) a microstrip line section where the first conductive layer continues as a band extending along the center of the flat substrate sheet to the second end of said substrate sheet, and where the second conductive layer gradually increases in width with distance from the first end of the substrate sheet until said width extends from the first to the second inner wall of the waveguide;

said first and second conductive layers being shaped in the balanced transmission line section, and in at least part of the impedance transformer/polarization twister and microstrip line sections, to define conductor-free areas on opposite sides of the balanced transmission line extending from each of the first and second waveguide walls to the nearest one of said conductive layer boundaries, said conductor-free areas being dimensioned to avoid resonances in the operating frequency range of the waveguide.