▲ German TRML-4D radar. Not long ago, the 10th World Radar Expo opened in Beijing, with nearly 500 companies from around the world exhibiting, highlighting the applications of radar and electronic information in multiple fields, attracting widespread attention from netizens. As is well known, radar is the "eye of a thousand miles" and "ear of the wind" of weapons and equipment, and both warring parties rely on radar to identify and measure target positions and motion parameters. Since the advent of radar, with the rapid development of the evolution of war forms, models of land-based, airborne, and shipborne radars have emerged one after another, and their application scenarios have become increasingly widespread. Currently, radar has made significant breakthroughs in terms of operating range, accuracy, and anti-interference, and is developing towards the integration of detection and countermeasures, diversification of tasks, and playing an important role in the battlefield. In the face of complex battlefield environments, to build a high-performance radar, it is not only necessary to "see far and clearly", but also to have a keen eye that can penetrate the thick fog of the battlefield and accurately distinguish the opponent's camouflage and deception methods. So, what is the origin of radar detection technology? What kind of development has it gone through? What technical challenges need to be overcome in developing modern radar? This article is for you to interpret one by one. In the contest between "spear" and "shield", a generation of fighter planes gave birth to a generation of radar to say goodbye to the era of close combat and close combat in the Cold weapon era. The combat distance of modern war has already exceeded the visible range. Whether one can anticipate the enemy first and take the initiative in battle determines the outcome of the war. In order to win the battle in Beyond-visual-range missile, the rise of radar is inevitable. Being able to bear this heavy burden is because radar has a unique skill - fast detection and tracking of targets, providing support for achieving "first enemy detection, first enemy launch, and first enemy hit" in combat. The earliest radar in the world was born during World War II. In September 1940, the German army dispatched hundreds of fighter jets to attack London. However, many fighter jets were discovered before reaching British airspace. How did the British army learn in advance about the flight dynamics of German fighter jets? How does ground artillery carry out precise strikes? The German army was puzzled by each question. Later, they learned that the British army used a "secret weapon" - radar - in this war, and at the same time, they pioneered the use of radar in military confrontation. Early military radars sent radio waves into the air through mechanical scanning to detect enemy aircraft target information. Since then, fighter jets and radars have engaged in a battle of "spear" and "shield" for over half a century. Due to the need for mechanical radar to aim the "pot cover antenna" at aerial targets, when detecting high-altitude and high-speed second-generation aircraft, the response speed is slow and faults are prone to occur. "The farther, faster, and more reliable" has become the research and development goal of the new generation radar. The United Kingdom, the United States, and other countries have taken the lead in developing planar array antennas that radiate electromagnetic waves through array gaps and synthesize them in space. This effectively enhances antenna gain, expands detection distance, and reduces the volume and weight of radar. A generation of fighter jets gave birth to a generation of radar. In several local wars during the Cold War, the flight speed and low altitude performance of third-generation aircraft have greatly improved, resulting in a doubling of radar blind spots. A large number of fighter planes have successfully achieved low altitude penetration through mountain terrain. The change of "spear" drives the upgrading of "shield". To display detection in a timely and effective manner