Phased-Array and Radar Breakthroughs

Many think that radar is a mature field, nothing new to happen, it having been around a long time. Nothing can be further from the truth. When I entered the field in the '50s I thought the same thing. The MIT Radiation Lab. Series 28 book volume set summarizing the highly classified World War II work on radar was just published and provided the definitive coverage and there was to be nothing more to learn. How wrong I was. Since then many amazing new developments have taken place. Things are moving even faster now. We live in exciting times. Phased array radars and radars have seen in recent years breakthroughs that lead to capabilities not possible only a few years ago. This is exemplified by the development of GaAs integrated microwave circuits called monolithic microwave integrated circuits (MMIC) which makes it possible to build active electronically scanned arrays (AESAs) having lighter weight, smaller volume, higher reliability and lower cost. MMIC allows the construction of AESAs for applications not feasible before. This integration has reached the point where it is possible to now build a low cost 35 GHz phased array for a missile seeker costing $40/element (total cost of array including all electronics divided by number of elements). The advances provided by Moore's Law has now made it is feasible to do digital beam forming with all its numerous advantages. One advantage of digital beamforming is the ability to lower the search power and occupancy by up to a factor of two. Another advantage is that it makes it possible to achieve the performance of a fully adaptive array without having to do a large matrix inversion, i.e., it makes adaptive-adaptive array processing or equivalently principal decomposition feasible. Also covered will be: the potential for GaN and SiC chips which have the capability of a factor of ten higher peak power than GaAs chips; arrays with instantaneous bandwidths of up to 33:1; SiGe low cost T/R modules; low cost MEMS arrays; metamaterials which provide negative refractivity possibly allowing focusing beyond the diffraction limit; a real radar application for Multiple-Input Multiple-Output (MIMO) as opposed to fantasy has been demonstrated by Lincoln Laboratory MIT which allows the coherent combining of two radars to achieve a 9 dB increase in sensitivity; the ability to build microwave tubes that are smaller, more power efficient, lighter, require lower voltages and have lower cost.