Hybrid array architectures for BMD radar systems

The proliferation of long range ballistic missiles has increased the need for radars capable of supporting early midcourse and ascent phase intercepts. In order to support these early midcourse and ascent phase intercepts, the ballistic missile defense (BMD) radar should be forward deployed. While a sea-based capability can be forward deployed, an easily transportable ground-based radar would be advantageous in certain scenarios. In this paper, we described a hybrid array antenna architecture that can provide target tracking performance similar to a conventional array design, but requires approximately 50 percent less prime power and cooling. In phased array antennas, the prime power and cooling requirements are dominated by the transmit portion of the antenna. Since the receive portion of the antenna requires only a small fraction of the total power, the prime power and cooling required can be reduced by approximately 50 percent by using a hybrid array architecture with only half the number (0.5N) of transmit/receive (T/R) modules as used in a conventional array. These T/R modules are located in the central core of the antenna and receive-only modules are added around the central core to compensate for the lost radar sensitivity. For this hybrid array to maintain the same power-aperture-gain (PAG) performance as the conventional array consisting of N T/R modules, approximately three and one half times as many (3.5N) receive-only modules will be required. Note that for tracking and discrimination, PAG is the appropriate measure for radar performance. The hybrid array architecture results in a large, but relatively lightweight, aperture. However, the antenna can be manufactured in a modular form, so that sections of the antenna can be shipped separately with final assembly being performed at the deployment site. Since receive-only modules have the potential to cost significantly less than T/R modules, the total antenna cost may still be lower than the conventional antenna with only T/R modules. Since the prime power, and therefore the DC power, required is reduced by 50 percent, the associated transmit portion of the antenna weight is reduced significantly. As a result, the total antenna weight of the hybrid array should still be less than the conventional ant- enna weight. Also, the rate of fuel consumption required to run the generators that power the array will also be reduced by approximately 50 percent, which eases the logistical burden of supplying fuel.