Signal processing partially solved the range resolution problem as early as in the 1970s. The key is a process called frequency modulation on pulse, which is used to compress a radar pulse. The advantage of using pulse compression is that with a twenty-microsecond pulse, the range resolution is reduced to about 180 feet or so. There are also several other techniques that can be used to compress a radar pulse such as phase shift keying. Indeed, according to Pietrucha, the technology for pulse compression is decades old and was taught to Air Force electronic warfare officers during the 1980s. The computer processing power required for this is negligible by current standards, Pietrucha said.
The United States has poured ten of billions of dollars into developing fifth-generation stealth fighters such as the Lockheed Martin F-22 Raptor and F-35 Joint Strike Fighter. However, relatively simple signal processing enhancements, combined with a missile with a large warhead and its own terminal guidance system, could potentially allow low-frequency radars and such weapons systems to target and fire on the latest generation U.S. aircraft.[3]
It is a well-known fact within Pentagon and industry circles that low-frequency radars [7] operating in the VHF and UHF bands can detect and track low-observable aircraft. [8] It has generally been held that such radars can’t guide a missile onto a target—i.e. generate a “weapons quality” track. But that is not exactly correct—there are ways to get around the problem according to some experts.