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Großwald Systems: Introduction to Radar Systems

The Foundations of Modern Sensing and Airspace Dominance

by Großwald Systems Desk

Updated June 17, 2025

Großwald Systems: Introduction to Radar Systems — Hensoldt TRML-4D **AIR SURVEILLANCE AND TARGET ACQUISITION RADAR; Credits: Hensoldt**

The Foundations of Modern Sensing and Airspace Dominance

Radar—short for Radio Detection and Ranging—has shaped the modern battlespace more than nearly any other sensor technology. From the early Chain Home network that safeguarded Britain in 1940 to today's airborne AESA arrays guiding precision weapons at standoff range, radar has proven indispensable in both surveillance and strike.

This introductory article provides a foundational understanding of radar systems, anchored in defense applications. Drawing on MIT Lincoln Laboratory’s acclaimed lecture series and key texts like Skolnik’s Introduction to Radar Systems, we establish the technical, historical, and operational groundwork for this ongoing Großwald Systems series.

1. Why Radar?

Radar systems emerged to address a fundamental problem in military operations: the inability to reliably detect threats under adverse conditions. Unlike optical or infrared sensors, radar operates independently of daylight or weather. It allows militaries to monitor airspace, land, and maritime domains with precision—even through clouds, darkness, and jamming.

Radar lifts the "fog of war" where human vision and passive sensors fail—night, storms, over-the-horizon targets, cluttered terrain. It is:

All-weather and day/night capable
Effective at long range
Resilient against many countermeasures
Crucial for 3D location, target identification, and track accuracy

Radar plays a core role in:

Air defense (e.g. IRIS-T SLM, NASAMS)
Ground surveillance (e.g. SAR on Global Hawk)
Fire control (e.g. APG-series radars)
Missile seekers (e.g. active radar homing)

2. The Basics

Core Radar Concepts

At its simplest, radar transmits a pulse of electromagnetic energy and listens for echoes. From that echo, it determines:

Range (distance to target)
Azimuth/Elevation (angle)
Velocity (via Doppler shift)
Size/Reflectivity (radar cross-section)

Fundamental Equation (Simplified)

The received signal power is governed by the Radar Range Equation, showing dependence on transmitted power, antenna gains, target size (RCS), and range:

The standard radar range equation (simplified, monostatic, no integration) is:

Pr = (Pt × G² × λ² × σ) / ((4π)³ × R⁴ × L)

Where:

Pr = received power
Pt = transmitted power
G = antenna gain (assumed same for Tx/Rx in monostatic)
λ = wavelength
σ = radar cross-section
R = range to target
L = system losses

The proportional form equals:

Pr ∝ Pt × Gt × Gr × λ² × σ / R⁴

With Gt = Gr = G for monostatic.

3. A Short History of Military Radar

Chain Home (UK, 1936–1945)

Frequency: 20–30 MHz
Wavelength: 10–15 m
Detection range: ~160 nmi
Enabled early warning against Luftwaffe raids
Operational Impact: Allowed RAF to mass limited fighter assets—decisive in the Battle of Britain

4. Radar Types by Function

Domain	Use Cases	Example Systems
Ground-based	Surveillance, Fire Control	Giraffe, Green Pine
Airborne	AEW&C, Strike, Navigation	Erieye, APG-81
Naval	Surface search, CIWS guidance	Sea Fire, SPY-6
Space	Missile warning, debris tracking	SBIRS, Space Fence
Civil	Air Traffic Control, Weather	ASR-11, NEXRAD

5. Key Radar Parameters

Term	Meaning
Wavelength (λ)	Distance between EM wave peaks
Frequency (f)	Cycles per second, linked to λ (f = c/λ)
Pulse Repetition Frequency (PRF)	Pulses sent per second
Duty Cycle	Pulse duration as % of time
Radar Cross Section (σ)	Target reflectivity (in m² or dBsm)
Antenna Gain (G)	Directional focusing power

6. Pulse and Doppler

Pulsed Radar

Emits discrete pulses
Range = (c × time delay) / 2
Peak vs. average power crucial

Doppler Radar

Measures velocity via frequency shift
Separates moving targets from clutter
Core to MTI (Moving Target Indication) and Pulse-Doppler radars

7. Frequency Bands (IEEE Standard)

Band	Range (GHz)	Use
L-Band	1–2	Long-range surveillance
S-Band	2–4	Medium-range search
C-Band	4–8	Weather, air defense
X-Band	8–12	Fire control, imaging
Ku/Ka/W	12–100+	Missile seekers, high-resolution SAR