A New Antenna with Low Cross-Pol
We have developed a new antenna with high gain and extremely low cross-polarization characteristics. We developed it for SAR-C calibration (NASA). The antenna is based on a short backfire principle: it has been optimized for high gain, low sidelobe, and low cross-pol (reduced below 40 dB). It is robust, low-weight, and very low-cost. Extensive numerical computation has informed the optimization. The prototype antenna has improved characteristics over conventional systems. These include: ·
- Cross-polarization goes down to - 50 dB in the worst case.
- Cross pol @ O = 10 deg and O = 0 deg is -61 dB.
- Cross pol @ O = 10 deg and O = 45 deg is -50 dB.
- Cross pol @ O = 10 deg and O = 90 deg is -68 dB.
- The gain of the antenna is 17dB.
- The feedpoint impedance is 15.1 + j2.9: this is matched with 50 or 300 ohms using stub.
- Very low sidelobe levels ~ -20dB.
- High stability.
- Increased tolerance towards surface accuracy and other dimensions.
- Increased tolerance over vibration and thermal stress.
- Extremely low weight.
- Can be manufactured at very low cost.
The prototypes have been developed under sponsorship of NASA for frequencies of 1-25 GHz. Similar units can be developed for frequencies to 10 GHz and the procedure of numerical modeling can be extended to higher frequencies.
These antennas offer super-gain characteristics (i.e., higher gain than the real-estate area) and can work in several configurations where improved gain is needed. An array of such antennas can easily be constructed for much higher gain and further reduced cross-polarization. These antennas can replace dual-mode type of feed, conventional dish antennas, or other systems requiring low cost, low weight, small real estate, high cross-pol rejection, and low sidelobe.