The AN/APQ-181 is an all-weather,

low probability of intercept A low-probability-of-intercept radar (LPIR) is a radar employing measures to avoid detection by passive radar detection equipment (such as a radar warning receiver (RWR), or electronic support receiver) while it is searching for a target or enga ...

(LPI)

phased array In antenna (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

system designed by

Hughes Aircraft The Hughes Aircraft Company was a major American aerospace company, aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of the Hughes Tool Company. The company produced the Hughes ...

(now

Raytheon Raytheon is a business unit of RTX Corporation and is a major U.S. defense contractor and industrial corporation with manufacturing concentrations in weapons and military and commercial electronics. Founded in 1922, it merged in 2020 with Unite ...

) for the

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its origins to 1 ...

B-2A Spirit The Northrop B-2 Spirit, also known as the Stealth Bomber, is an American heavy strategic bomber, featuring low-observable stealth technology designed to penetrate dense anti-aircraft defenses. A subsonic flying wing with a crew of two, ...

bomber aircraft. The system was developed in the mid-1980s and entered service in 1993. The APQ-181 provides a number of precision targeting modes, and also supports

terrain-following radar Terrain-following radar (TFR) is a military aerospace technology that allows a very-low-flying aircraft to automatically maintain a relatively constant altitude above ground level and therefore make detection by enemy radar more difficult. It is ...

and

terrain avoidance In aviation, a terrain awareness and warning system (TAWS) is generally an on-board system aimed at preventing unintentional impacts with the ground, termed "controlled flight into terrain" accidents, or CFIT.Federal Aviation AdministrationInsta ...

. The radar operates in the K_u band (a subset of the J band). The original design uses a TWT-based

transmitter In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna (radio), antenna with the purpose of sig ...

with a 2-dimensional

passive electronically scanned array A passive electronically scanned array (PESA), also known as passive phased array, is an antenna in which the beam of radio waves can be electronically steered to point in different directions (that is, a phased array antenna), in which all the ...

(PESA) antenna. In 1991, the B-2 Industrial Team (including Hughes as a major subcontractor) was awarded the

Collier Trophy The Robert J. Collier Trophy is awarded annually "for the greatest achievement in aeronautics or astronautics in America, with respect to improving the performance, efficiency, and safety of air or space vehicles, the value of which has been t ...

in recognition of the "design, development, production, and flight testing of the B-2 aircraft, which has contributed significantly to America's enduring leadership in aerospace and the country's future national security." In 2002, Raytheon was awarded a contract to develop a new,

active electronically scanned array An active electronically scanned array (AESA) is a type of phased array antenna, which is a computer-controlled antenna array in which the beam of radio waves can be electronically steered to point in different directions without moving the a ...

(AESA) version of the APQ-181. This upgrade will improve system reliability, and will also eliminate potential conflicts in frequency usage between the B-2 and commercial satellite systems that also use the J band. In 2008 the

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...

accidentally sold the APQ-181 frequency to a commercial user. This resulted in an additional cost to modify the in-progress AESA upgrade which had a total cost of around $1 billion, although the cost for the frequency change was only a portion of this. All B-2 aircraft are expected to have the upgraded radar by 2010. In accordance with the

Joint Electronics Type Designation System The Joint Electronics Type Designation System (JETDS), which was previously known as the Joint Army-Navy Nomenclature System (AN System. JAN) and the Joint Communications-Electronics Nomenclature System, is a method developed by the U.S. War Depa ...

(JETDS), the "''AN/APQ-181''" designation represents the 181st design of an Army-Navy airborne electronic device for

special equipment. The JETDS system also now is used to name all

Department of Defense The United States Department of Defense (DoD, USDOD, or DOD) is an executive department of the U.S. federal government charged with coordinating and supervising the six U.S. armed services: the Army, Navy, Marines, Air Force, Space Force, ...

electronic systems.

References

External links

Raytheon product description
{{Raytheon, state=collapsed Aircraft radars Raytheon Company products Radars of the United States Air Force Military radars of the United States Military equipment introduced in the 1990s Military electronics of the United States

See also

References

External links