Antenna with fifty percent overlapped subarrays
An antenna suitable for use as a phased array antenna of a radar system. The antenna includes a plurality of radiating elements, and a substrate integrated waveguide (SIW) configured to form a feed network to couple energy from a plurality of inputs to the radiating elements. The feed network includes over-moded waveguide couplers configured so energy propagates through an over-moded section in multiple modes, TE10 and TE20 modes for example. The feed network also defines sub-arrays configured such that half of the radiators of a sub-group are shared with an adjacent sub-group of an adjacent sub-array, i.e. the sub-arrays are configured to have 50% overlap. Preferably, the feed-network is formed about a single layer of substrate material.
1. An antenna suitable for use as a phased array antenna of a radar system, said antenna comprising:
a plurality of radiating elements; and
a feed network configured to define a plurality of inputs and couple energy from the inputs to the radiating elements, wherein energy from each of the inputs is coupled to a power divider, wherein the feed network is further configured to define
a plurality of over-moded waveguide couplers configured to define a plurality of sub-arrays that couple each input to a sub-group of the radiating elements, wherein the sub-arrays are arranged in a side-by-side arrangement and configured such that half of the radiators of a sub-group are shared with an adjacent sub-group of an adjacent sub-array, wherein each of the over-moded waveguide couplers is configured to define
a left in-port that receives energy from a left divider,
a right in-port that receives energy from a right divider adjacent the left divider,
a left out-port that guides energy to a left radiator, and
a right out-port that guides energy to a right radiator adjacent the left radiator, wherein
each over-moded waveguide coupler includes an over-moded section defined by a width selected such that energy propagates through the over-moded section in multiple modes effective to establish a first path for energy from the left in-port and a second path for energy from the right in-port, wherein the first path is distinct from the second path.
2. The antenna in accordance with claim 1 , wherein the feed-network is formed about a single layer of substrate material.
3. The antenna in accordance with claim 1 , wherein energy coupled from the over-moded section to left out-port is in-phase with energy coupled from the over-moded section to right out-port.
4. The antenna in accordance with claim 1 , wherein the multiple modes include a TE10 mode and a TE20 mode.
5. The antenna in accordance with claim 1 , wherein each over-moded section has a width and length selected such that
a first amount of energy propagates from the left in-port to the left out-port, and
a second amount of energy less than the first amount propagates from the left in-port to the right out-port.
6. The antenna in accordance with claim 5 , wherein a third amount of energy less than the second amount propagates from the left in-port to the right in-port.
7. The antenna in accordance with claim 6 , wherein energy that propagates from the left in-port to an adjacent radiator via the right in-port and is out-of-phase with energy from the left in-port that propagates to the left radiator and the right radiator.
8. The antenna in accordance with claim 1 , wherein the over-moded waveguide coupler is characterized by a first distribution of energy from the left in-port that is a mirror image of a second distribution of energy from the right in-port.
9. The antenna in accordance with claim 1 , wherein each sub-array includes a sub-group formed by four adjacent radiators coupled to two adjacent over-moded waveguide couplers, wherein an energy distribution to the sub-group from the two adjacent over-moded waveguide couplers exhibits an amplitude taper characterized by an inner amplitude of energy to inner radiators of the sub-array that is greater than an outer amplitude of energy to outer radiators of the sub-array.
10. The antenna in accordance with claim 9 , wherein energy from the two adjacent over-moded waveguide couplers of the sub-array that propagates to the four adjacent radiators that form the sub-group is characterized as in-phase, and energy from the two adjacent over-moded waveguide couplers that propagates to a secondary radiator adjacent the sub-group is characterized as out-of-phase with energy of the sub-group.
11. The antenna in accordance with claim 1 , wherein the feed network includes an end coupler on each end of the feed network, wherein the end coupler includes a bulge configured to compensate for a missing outer in-port, said bulge configured to provide an alternative energy path effective to cause energy that propagates to radiating elements directly coupled to the end coupler to be in-phase with energy that propagates to radiating elements directly coupled to an adjacent over-moded waveguide coupler.