Travelling wave antenna feed structures
Techniques for implementing series-fed antenna arrays with a variable dielectric waveguide. In one implementation, coupling elements with optional controlled phase shifters are placed adjacent each radiating element of the array. To avoid frequency sensitivity of the resulting array, one or more waveguides have a variable propagation constant. The variable waveguide may use certain materials exhibiting this phenomenon, or may have configurable gaps between layers. Plated-through holes and pins can control the gaps; and/or a 2-D circular or a rectangular travelling wave array of scattering elements can be used as well.
1. An antenna apparatus comprising:
a waveguide having a top surface, a bottom surface, an excitation end, and a load end, the waveguide formed of two or more layers, with gaps formed between the layers;
a control element arranged to adjust a size of the gaps, where the control element may be a piezoelectric, electroactive material or a mechanical position control; and
two or more delay elements disposed along the waveguide, wherein a delay introduced by each delay element decreases with position of the delay element with respect to its position relative to the excitation end and to the load end.
2. The apparatus of claim 1 wherein a cumulative additional delay introduced by the delay elements effectively cancels a delay introduced by the waveguide.
3. The apparatus of claim 1 additionally comprising:
an array of scattering elements disposed on the top surface of the waveguide.
4. The apparatus of claim 3 wherein the scattering elements are disposed in a Cartesian grid pattern.
5. The apparatus of claim 4 wherein the scattering elements are disposed in a concentric circular array pattern.
6. An antenna apparatus comprising:
a waveguide having a top surface, a bottom surface, an excitation end, and a load end, the waveguide formed of two or more layers, with gaps formed between the layers;
a control element arranged to adjust a size of the gaps, where the control element may be a piezoelectric, electroactive material or a mechanical position control; and
two or more delay elements disposed along the waveguide, wherein the control element additionally comprises:
holes disposed in each of the layers of the waveguide, with the holes in a given layer arranged in a grid and aligned with holes in an adjacent layer;
actuator material strips positioned along rows of the holes; and
pins disposed in the holes.
7. The apparatus of claim 6 wherein the holes are plated and the pins are metallic such that an electrical signal propagates there through to the actuator material strips.