State Of Counterstealth Technology On Display At Airshow China
This is the fourth article in a series. Even as the Shenyang J-20 fighter performed its first public display above November’s Airshow China in Zhuhai, the tall arrays of low-frequency air surveillance radars standing over the crowds were evidence of Beijing’s efforts not only to match but to counter the U.S. advantage in stealth.
Towering over the flight line at Zhuhai were three air-defense radars from China Electronics Technology Group Corp. (CETC) and its Nanjing Research Institute of Electronic Technology (NRIET). The low-frequency trio reveals a similar design philosophy comprising tall arrays of horizontally polarized dipoles, the VHF-band JY-27A with 400 elements, UHF-band YLC-8B with 1,800 and L-band SLC-7 with 2,900.
The approach taken by CETC and NRIET to detecting low-observable aircraft while overcoming the limitations of lower-frequency radars appears different than that taken by Russia’s Nizhny Novgorod Research Institute of Radio Engineering (NNiiRT), which has employed wider arrays and, more recently, vertically polarized elements. Early Russian VHF systems like NNiiRT’s P-12 and P-18 used two rows of horizontally polarized Yagi antennas. The P-12 had six elements in each row, the P-18 had eight. In 1982, NNiiRT introduced the first VHF radar with 3-D capability—the ability to ascertain target elevation in addition to range and bearing—the 55Zh6 Nebo “Tall Rack.” This massive, semi-mobile system consisted of four arrays of horizontal dipole elements on top of each other, the bottom one consisting of six rows of 26. A few years later, the institute’s 1L13 Nebo-SV “Box Spring” entered service with six rows of 14 Yagis, shorter than those on the P-12/-18 and with folded dipoles.
In the early 2000s, Russia revealed its first active, electronically scanned array (AESA) VHF radar, the 1L119 “Nebo-SVU,” which had six rows of 14 short Yagis with folded dipoles, now vertically polarized. This was the first mobile VHF band radar to achieve 3-D capability, but its accuracy was limited, particularly in elevation.
NNiiRT addressed the problem by expanding the arrays while adding higher-frequency radars to the system. Later in the 2000s, the 55Zh6ME Nebo-M was introduced, consisting of three radars mounted on separate vehicles: VHF-, L- and S-band. The VHF radar had seven rows of 24 Yagi elements. A few years later, NNiiRT introduced the 55Zh6UME, which mounted a VHF-band AESA (with six rows of 20 elements) along with a 36-row L-band antenna on a single trailer...
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http://aviationweek.com/defense/state-counterstealth-technology-display-airshow-china
