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. A phased array antenna apparatus comprising:
an array of radiating elements;
a pair of main waveguides, the main waveguides each having a variable propagation constant; and
a plurality of directional couplers, with a pair of directional couplers disposed between each one of the radiating elements and the pair of main waveguides, such that each one of the radiating elements is coupled to each of the pair of main waveguides through a respective one of the corresponding pair of directional couplers, the directional couplers controlling phasing of signals fed to the respective radiating element.
2. The apparatus of claim 1 wherein each of the directional couplers further comprises:
a coupling slot formed adjacent the respective main waveguide; and
a probe disposed between the respective main waveguide and radiating element.
3. The apparatus of claim 2 wherein the directional couplers further comprise:
a load disposed adjacent the probe, the coupling slot and respective main waveguide.
4. The apparatus of claim 1 wherein each directional coupler comprises a pair of probes coupled to the respective radiating element in quadrature.
5. The apparatus of claim 1 wherein at least one coupler further comprises one or more mirrors, positioned to further control delay of signals fed to the respective radiating element.
6. The apparatus of claim 1 wherein at least one main waveguide is operated in two modes, where each mode has a different propagation constant.
7. The apparatus of claim 1 wherein the directional couplers are a waveguide-type directional couplers disposed on a top surface of each of the main waveguides.
8. The apparatus of claim 1 additionally comprising:
a quadrature phase shifter disposed between the pair of main waveguides.
9. The apparatus of claim 1 wherein the main waveguides further comprise a multi-layered dielectric material.
10. The apparatus of claim 9 wherein the propagation constant of the main waveguides is varied by changing a spacing between the dielectric layers.
11. The apparatus of claim 9 wherein the propagation constant of the main waveguides is varied by changing a voltage applied to an actuator arranged to control a spacing between the dielectric layers.
12. An apparatus comprising:
a pair of waveguides, each waveguide comprising a plurality of dielectric material layers;
a quadrature phase shifter, disposed adjacent a signal feed point and coupled to the pair of waveguides;
a plurality of directional couplers, the directional couplers disposed on a top surface of and electromagnetically coupled to each of the main waveguides, each directional coupler comprising at least one dielectric material layer;
a plurality of radiating patch elements, disposed on a top surface of and adjacent to the directional couplers, with each radiating element electrically connected to two adjacent directional couplers;
a plurality of probes, each disposed within a corresponding one of the plurality of directional couplers, the probes capacitively coupling a respective one of the pair of waveguides to the corresponding one of the radiating patch elements; and
a quadrature phase shifter, disposed between the pair of waveguides.