Planar emitter

In a planar emitter apparatus (1) having a plurality of sandwich like layers (4, 5, 6, 7, 8) that are plan-parallel to each other the improvement wherein:

• a first layer (5) is a dielectric layer made of two different dielectric materials;
• a first dielectric material of said first layer (5) forms a second layer (14) having opposed sides and a thickness L1;
• the second dielectric material of said first layer (5) forms a third layer (15) having opposed sides and a thickness L2;
• said second layer (14) has one of said opposed sides in contact with one of said opposed sides of said third layer (15);
• a fourth layer (7) is a dielectric layer having opposed sides made of a dielectric material;
• a fifth layer (6) is an electrically conductive thin layer defining a common earthing member for said planar emitter apparatus (1) and interposed between and in contact with the side of said second layer (14) that is not in contact with said third layer (15) and with one of said sides of said fourth layer (7);
• a sixth layer (4) is a plurality of spaced, thin layer electrically conductive planar resonators (4) in contact with the side of said third layer (15) that is not in contact with said second layer (14);
• a seventh layer (8) is a coupling network (3) comprising microstrip circuits (3a-3f) in contact with the side of said fourth layer (7) that is not in contact with said sixth layer (6);
• means (9) extend through said first, fifth and fourth layers (5, 6, 7) from said coupling network (3) to said planar resonators (4) to couple said planar resonators (4) electrically in phase;
• and
• said thickness L1 of said second layer (14) is greater than said thickness L2 of said third layer (15).