The New Radar Killer Kh 58 UShK
The Russians almost completed the prototype variant of new generation anti radiation missile the Kh 58, which is completely a new missile with older X 58 air frame along with folding fins, which allows the missiles can house inside the Su T 50's internal weapon bay. The Russians and Indians involved to build a new generation Fighter under the PAK FA and FGFA program, for that they gone for fully modern systems, from Engines to Radars and Missiles to Electronic warfare system.
To defeat the much modern Anti Air missile batteries like most powerful S 400 missile defense system and western Patriot system, the need of smart aircraft along with smart munitions needed, in the modern Air warfare the Ground based threats pose serious problems to the Fighter jets, those highly powerful stand alone modern Air defense missile can engage any kind of modern threats with high accuracy, even they can ripple fire missiles allows to intercept highly maneuverable small aircraft's with high precision.
So there is a need of missile that can intercept such ground threats more accuracy, usually the missile defense system comes with couple of elements, like Radar, Launcher, command vehicles, most of the Ground based systems are highly mobile, that can be moved within a minutes and can be deployed again very quickly, thus makes long range cruise missiles ineffective to strike such missile systems, even most systems are positioned in good distances, also those missile defense systems comes with couple of launchers, but one or two Air search and Fire control Radars, usually most comes with only one Radar systems, a Typical S 400 Missile battery consist of four launchers and two Radars along with other support vehicles,
It's tough to find and kill the Radar, which is the heart of the missile defense system, so there is missile called anti radiation missile, which can target only the Radars with it's frequency, the S 400 Radars emits signals in the S Band frequency that means 2 GHz to 4 GHz, so the missile would be lock a target which can emit frequency at the S band, the early anti radiation missiles are developed at specific bands only, but now the modern Ground based Radars uses multiple spectrum, the need of new missile which can respond more band of frequency's. so the Russians put into the work that a seeker can acquire frequency's at all bands commonly L,S,C and X which varies from 1 GHz to 12 GHz.
and Russians did it a good missile seeker that can intercept and lock frequencies at 1.2 GHz to 11 GHz. makes that missile good enough against most modern Radar systems, another issue is the speed and warhead, the missile can travel at the speed of mach 4 and can be launched from at an altitude of 600 feet to 60,000 feet, but due to the altitude the range also varies, means if it can launched from higher altitude the missile can reach the highest distance of 240 kilometers, and if launched at low altitude the missile ranged capped at 70 kilometer.
The major disadvantage of the Missile is it's precision capability, the missile can't strike at bulls eye, or pin point, it's strike probability is 20 meters, means missile can strike near to the Radar, mostly less than 20m. because of the heavier payload, even if it strikes near to the Radar, the warhead can destroy anything nearby 20 meters, the missile weights at 650 kilograms, and the warhead weighs upto 150 kg. which is High explosive warhead.
the T 50 can carry two Kh 58 missile in it's main internal weapon bay, and another two short range heat seeking missiles in it's side bay, with this internal payload the T 50 nearly invisible to the Enemy radars, then only the Fighter can enter inside the Radar's search area, the Kh 58 missile ranges 240 kilometers at most, but the S 400 radar's Range more than 300 kilometers, can easily detect the launched missile,
earlier the Fighters used Terrain hugging method to perform SEAD mission, the fighters computers provide the Blind side of the Radar, where the Fighter can travel and launch it's missile, the IAF uses the Jaguar a finest Terrain hugging plane which can be armed with French made Martel Missile, also the Mirage platforms are also used for the same, but still IAF didn't try for a SEAD mission inside Pakistani or Chinese airspace.
The IAF Sukhoi 30 MKI also comes with earlier version of Kh 58 ARM missile,another variant of Anti radiation missile named K 100 novotar, A joint venture between India and Russia to develop a missile to kill enemy airborne radar platforms like aerostats and awecs planes, also DRDO involves a Project to develop a indigenous missile for SEAD role, named NG ARM, whose status is not available since it's highly classified, and It's expected that The Jaguars gets the American High speed anti radiation missile AGM 88 HARM in the DARIN III Upgrade.
Truth is it's hard to find the frequency of SAM missile's Radars since Ship, Televisions, Telecoms are all use the same frequencies to transmit signals.