Antenna elements and array
Antenna elements are described that may include a radiator, a feeding portion, a first impedance transformer, a balun, and a second impedance transformer. The first impedance transformer, balun, and second impedance transformer may be disposed above a ground plane of an antenna array to reduce a bulk of the array. The array can also include a dielectric top layer for loading apertures of the antenna array. The antenna elements can also include anomaly suppressors can be provided to cancel common-mode resonances from the radiators.
1. An antenna array, comprising
a plurality of antennas forming an array,
a single common ground plane coupled to each of the plurality of antennas, wherein each of the antennas is disposed above the ground plane,
a feed portion associated with each of the plurality of antennas and disposed below the ground plane, and
a dielectric top cover coupled to the plurality of antennas,
wherein each of the antennas of the plurality of antennas includes a pair of radiating elements and an impedance matching network coupled to the radiating elements, wherein the impedance matching network includes
a first impedance transformer connected to the feed portion,
a balun directly connected at one end to the first impedance transformer, wherein the balun has a central inner portion and a pair of opposed outer portions, and
a second impedance transformer directly connected to the other end of the balun and to the radiator such that the balun is disposed between the first impedance transformer and the second impedance transformer,
wherein the feed portion, the first impedance transformer, the balun and the second impedance transformer are connected and arranged in series,
wherein the first impedance transformer includes a plurality of microstrip lines, wherein the plurality of microstrip lines includes a central conductor disposed between first and second edge conductors, wherein the first and second edge conductors have a relatively tapered shape and are generally the same size, and
wherein the central conductor is coupled to the central inner portion of the balun and the first and second edge conductors are coupled respectively to each of the opposed outer portions of the balun.
2. The antenna array of claim 1 , wherein the plurality of microstrip lines of the first impedance transformer form about a third of the height of the antenna.
3. The antenna array of claim 1 , wherein each of the plurality of antennas are relatively perpendicular to the ground plane at a distance of less than 0.1 wavelengths at a lower end of an operational band.
4. The antenna array of claim 1 , wherein the dielectric top cover includes a plurality of layers of a low-loss dielectric material so as to enhance the impedance matching and the bandwidth of each of the plurality of antennas.
5. The antenna array of claim 1 , further comprising a plurality of anomaly suppressors for canceling common-mode resonance anomalies in a signal from the feed portion, wherein each of the plurality of anomaly suppressors includes one or more conductors coupled to the second impedance transformer and another adjacent one of the plurality of antennas to form a common-mode cancelation network among the antennas.
6. The antenna array of claim 1 , wherein the feed portion comprises a plurality of leads to form an unbalanced transmission line.
7. The antenna array of claim 1 , wherein the balun has a double-Y shape and comprises a plurality of ports.
8. The antenna array of claim 7 , wherein the balun further comprises a plurality of bridge elements.
9. The antenna array of claim 1 , wherein each of the radiating elements includes one or more coupling elements to facilitate coupling to one or more adjacent antennas.
10. The antenna array of claim 1 , wherein the first impedance transformer converts an impedance of a signal from the feed portion to an intermediate impedance, and wherein the second impedance transformer converts the signal to a target impedance.
11. The antenna array of claim 1 , wherein the plurality of antennas are disposed adjacent to one another on a plurality of printed circuit boards.
12. The antenna array of claim 11 , wherein the plurality of printed circuit boards are disposed on the ground plane in an eggcrate configuration.
13. The antenna array of claim 11 , wherein a first printed circuit board comprising a first set of the plurality of antennas is disposed perpendicularly to a second printed circuit board comprising a second set of the plurality of antennas.
14. The antenna array of claim 13 , wherein the first printed circuit board and the second printed circuit board are disposed such that anomaly suppressing conductors of at least two of the plurality of antenna elements are in electrical contact.