What is Radar?

RADAR = RAdio Detection And Ranging. A radar system sends out radio waves and listens for echoes bouncing off objects. By measuring the time delay and frequency shift, it can determine an object’s range, speed, altitude, and direction.

In fighter aircraft, radar is the primary sensor for detecting, tracking, and engaging targets — especially at night, in clouds, or beyond visual range. Modern fighter radars can simultaneously track 20+ targets, guide multiple missiles, map terrain, and even jam enemy electronics.

Mechanically Scanned Array (MSA)

The antenna physically rotates or tilts to scan the sky. Simple, reliable, and proven — but slow to scan and can only do one thing at a time (search OR track, not both simultaneously).

Pros: Cheap, reliable, field-repairable
Cons: Slow scan rate, limited multitasking, easy to detect
Examples: APG-70 (F-15E), APG-68 (F-16), N011M (Su-27SM)

Passive Electronically Scanned Array (PESA)

Uses a single transmitter feeding many antenna elements through phase shifters. The beam is steered electronically — much faster than mechanical scanning. However, it still has a single point of failure (the transmitter).

Pros: Fast beam steering, good power output, reliable
Cons: Single transmitter = single point of failure, limited frequency agility
Examples: Irbis-E (Su-35, range 350+ km!), N035 Bars (Su-30MKI), Zaslon (MiG-31)

Active Electronically Scanned Array (AESA)

The gold standard of modern fighter radar. Each of the 1,000-2,000 antenna elements (T/R modules) is its own tiny radar. This enables:

• Near-instant beam steering — scan the entire sky in milliseconds
• Multi-function — simultaneously search, track, jam, and map terrain
• Low Probability of Intercept (LPI) — spread signals across frequencies, hard to detect
• Electronic attack — focus energy to jam enemy radars
• Graceful degradation — if some elements fail, the radar still works
• Frequency agility — change frequency thousands of times per second

How Stealth Works Against Radar

Stealth aircraft use several techniques to reduce their Radar Cross Section (RCS):

Shape: Angled surfaces reflect radar energy away from the receiver (F-117’s faceted design, F-22/F-35’s blended shapes)

Radar-Absorbing Materials (RAM): Special coatings and structural materials that absorb radar energy and convert it to heat

Internal weapons bays: External weapons create huge radar returns. F-22, F-35, J-20, and Su-57 all carry weapons internally

Edge alignment: All edges (wings, tails, intakes) are aligned to the same angles, creating just a few narrow radar “spikes” instead of reflections in all directions

Counter-Stealth Technologies

No aircraft is truly invisible. Several technologies can detect stealth aircraft:

Low-frequency radar (VHF/UHF): Stealth shaping is optimized against high-frequency X-band radar. Low-frequency waves with wavelengths similar to the aircraft’s features can still detect it. (Used by Russia’s Nebo-M system)

Passive detection: Instead of emitting radar, listen for the stealth aircraft’s own emissions (radio, datalink, radar). Systems like Czech Vera-NG and Chinese DWL-002.

Infrared Search & Track (IRST): Detect aircraft by their heat signature. No radar emission needed. Used by Su-35 (OLS-35), Rafale (OSF), Typhoon (PIRATE), and F-35 (DAS).

Bistatic/multistatic radar: Transmitter and receiver at different locations. Stealth shapes can’t deflect energy away from all receivers simultaneously.

AN/AWG-9 — F-14 Tomcat’s Eyes

The legendary radar that made the F-14 Tomcat the fleet’s guardian. Could track 24 targets simultaneously and guide 6 AIM-54 Phoenix missiles at once — an unprecedented capability in the 1970s. Detection range exceeded 300 km for bomber-sized targets.

AN/APG-77 — F-22 Raptor’s AESA Pioneer

The first operational AESA radar on a fighter aircraft. The APG-77 gives the F-22 first-look, first-shot, first-kill capability. It can detect a 1m² target at 250+ km while being virtually undetectable itself thanks to LPI techniques. It can also function as a narrowband jammer.

Irbis-E — Su-35’s Passive Powerhouse

The Irbis-E is the most powerful fighter PESA radar ever built. With 20 kilowatts of peak power, it can detect a 3m² target at an astounding 350-400 km. It features a unique hydraulic-mechanical steering system that gives the antenna a ±120° scan range.

AN/APG-81 — F-35’s Sensor Brain

The APG-81 doesn’t just see — it thinks. Part of the F-35’s integrated sensor suite, it automatically fuses data from radar, IRST (DAS), electronic warfare sensors, and off-board sources. The pilot sees a single unified picture, not raw radar returns. It can simultaneously:

• Track 20+ air targets • Map terrain with SAR • Perform electronic attack • Guide AMRAAM and JDAM • Share data via Link 16