Who Invented Radar?
Heinrich Hertz in Germany calculated that an electric current swinging very rapidly back and forth in a conducting wire would radiate electromagnetic waves into the surrounding space. Today we would call such a wire an ‘antenna’. He created such a wire in 1886, and detected such oscillations in his lab, using an electric spark, in which the current oscillates rapidly (that is how lightning creates its characteristic crackling noise on the radio!).
Today we call such waves ‘radio waves’. At first however they were ‘Hertzian waves’, and even today we honor the memory of their discoverer by measuring frequencies in Hertz (HZ), oscillations per second—and at radio frequencies, in megahertz (MHZ).
Heinrich Hertz was the first to demonstrate experimentally the production and detection of Maxwell’s waves. This discovery led directly to the invention of the radio. Sir Robert Alexander Watson Watt (1892-1973) was the Scottish physicist who developed the radar locating of aircraft in England. He was appointed as the director of radio research at the British National Physical Laboratory in 1935, where he completed his research into aircraft locating devices. Radar was patented in Britain in April 1935.
However, it was not until the early 20th century that systems able to use these principles were becoming widely available, and it was German inventor Christian Hülsmeyer who first used them to build a simple ship detection device intended to help avoid collisions in fog. Numerous similar systems, which provided directional information to objects over short ranges, were developed over the next two decades.
The development of systems able to produce short pulses of radio energy was the key advance that allowed modern radar systems to come into existence. By timing the pulses on an oscilloscope, the range could be determined and the direction of the antenna revealed the angular location of the targets. The two, combined, produced a “fix”, locating the target relative to the antenna.
During 1934–1939, eight nations developed independently, and in great secrecy, systems of this type: the United Kingdom, Germany, the United States, the USSR, Japan, the Netherlands, France, and Italy. In addition, Britain shared their information with the United States and four Commonwealth countries: Australia, Canada, New Zealand, and South Africa, and these countries also developed their own radar systems. During the war, Hungary was added to this list. The term RADAR was coined in 1939 by the United States Signal Corps as it worked on these systems for the Navy.
Progress during the war was rapid and of great importance, probably one of the decisive factors for the victory of the Allies. A key development was the magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. By the end of hostilities, Britain, Germany, the United States, the USSR, and Japan had a wide diversity of land-and sea-based radars as well as small airborne systems.
After the war, radar use was widened to numerous fields including: civil aviation, marine navigation, radar guns for police, meteorology and even medicine. Key developments in the post-war period include the travelling wave tube as a way to produce large quantities of coherent microwaves, the development of signal delay systems that led to phased array radars, and ever-increasing frequencies that allow higher resolutions. An increase in signal processing capability due to the introduction of solid state computers has also had a large impact on radar use.