S-band Large Phased Array Radar
China's new LPAR looking at Russia and India has the capability to rotate 360°. It's range is likely to be large with azimuth changing face. The S-band radar primarily conducts large-volume searches and is capable of performing radar tracks and collections on a large number of radar targets.
This new facility was disclosed in February 2020 by Col (Retired) Vinayak Bhat, who served in the Indian Army for over 33 years. He was a satellite imagery analyst for more than two decades and served in high altitude areas of J&K and North East. An alumnus of NDA, Pune, he was a mountaineer during his young days, climbing peaks like Stok Kangri and Nun Peak. Follow him on Twitter @ rajfortyseven. He initially declined to identify the location of this new radar.
This new radar is generally similar in concept to the Korla, Xinjiang LPAR which which had been under construction since 2004, and was used to support China’s successful exo-atmospheric interception of a ballistic missile on January 11, 2010. Without knowing the location of the second radar, it is difficult to understand the precise role it might play in Chinese BMD or ASAT capabilities.
One limitation of radar is that the return signal varies directly with the square of the wavelength. This means the range that we can achieve increases by increasing the wavelength, which in turn implies both a larger transmitting and receiving antennae. For instance, an S-Band radar operating from 4 to 8 GHz (with a wavelength of ~8 cm to 4 cm) has inherently less attenuation and capability to detect targets at longer range than an X-band radar operating from 8 to 12 GHz (with a corresponding wavelength from 4 cm to 2.5 cm). However, as a rule the S-band radar components are nearly twice the size of X-band components.
Two of the major constituents in the atmosphere are oxygen and water and these components absorb radio frequency energy. As shown by the black line in the figure, the higher the frequency, the more they absorb and hence, the less energy the transmitter can place on the target. In order to detect a target at a given range, designers either must transmit more power or move to a lower frequency. Often, the radar designer must trade size and power (along with operating frequency) for range and resolution.
Radar designers are confronted with a number of tradeoffs. One of the most important is the trade between required range and available resolution. This trade exists because for a given power level, the effective range of a radar decreases with increasing frequency. At the same time, target resolution generally increases with increasing frequency. Hence the designer must pick a frequency which balances the range requirements with the needed resolution. Generally, for a given range capability, as the operating frequency increases, the size, weight and power draw of the components decrease. This is largely due to the fact that the wavelength is shorter for higher frequencies so the components are simply smaller than their long wavelength counterparts.
The U.S. Air Force Space Fence radar located on Kwajalein Atoll uses advanced solid-state S-band radar technology. The technology includes element level digital beamforming, The US Navy Air and Missile Defense Radar (AMDR) is the Navy's next generation radar system that will address Ballistic Missile Defense and Air Defense capability gaps identified in the Maritime Air and Missile Defense of Joint Forces Initial Capabilities Document. The AMDR suite consists of an S-band radar (AMDR-S), X-band radar, and a Radar Suite Controller (RSC). The Theater Air and Missile Defense (TAMD) radar systems envisioned for use in next-generation naval surface combatants are anticipated to include high-power apertures operating at S-band. While the high power of these systems is driven by ballistic missile defense requirements, the radars are, by necessity, multifunction and will also be required to detect and track targets at low elevations in clutter.
In the US, only sea-based systems are mounted on rotating turrets. The Cobra Judy S-Band Phased Array radar featured a larger radar mounted on a turret, for 360 coverage regardless of the orientation of the ship. The Cobra Judy Replacement (CJR) Program includes the design, development, and acquisition of a functional replacement ship and mission equipment (ME) suite for the current Cobra Judy and USNS Observation Island. The S-band radar serves as the primary searchand-acquisition sensor and is capable of tracking and collecting data on a large number of objects in a multitarget complex.
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