Ferdinand Braun: Father of the Phased Array & CRT

Jacqueline Hochheiser, Corporate Communications

The concept of the phased array antenna system was first put into practice by German Physicist Ferdinand Braun and his assistants in the spring of 1905. This invention led to the development of radar, smart antennas, and MIMO. Though his career was mainly spent as an educator of physics in various university appointments, he was also an avid inventor and was even a co-winner of the Nobel Prize for Physics in 1909 for his contributions toward the development of wireless telegraphy.

Early Life & Career

Braun was born on June 6, 1850 at Fulda, Germany, where he was educated at the local “Gymnasium,” or grammar school. He then went on to attend the University of Marburg and earned his PhD from the University of Berlin. He graduated in 1872 with a completed paper on the oscillations of elastic strings, which would serve as the catalyst for his later inventions.

In 1874, Braun attained his first position as an assistant to a professor of physics at the Wurzburg University. Over the course of his life, Braun held various teaching positions including Extraordinary Professor of Theoretical Physics at the University of Marburg in 1876. In 1885, Braun was invited to the University of Tubingen for a role as the professor of physics, and was also tasked with building a new physics institute. It was here that he stayed for the remainder of his professional career, and the institute allowed him access to a laboratory for his work as an independent inventor.

Experimentation & Invention

Braun’s first investigations pursued the oscillations of strings and elastic rods in regard to the influence of amplitude and environment on the rods during their oscillations. But perhaps his most important work was done in the field of electricity. He discovered the rectification effect that a point-contact, metal-semiconductor junction has on alternating current in 1874,¹ which was essentially the first crystal detector and the first semiconductor junction.

Braun’s experiments led him to invent what is now known as Braun’s Electrometer, or a cathode-ray tube (CRT) that he constructed in 1897. The CRT became the cornerstone to eventually inventing the television, as it was a critical part of any electronic screen up until the production of the LCD screen at the end of the 20^th century. By 1898, Braun had taken up wireless telegraphy and attempted to transmit Morse signals through water by means of high-frequency currents.

Subsequently, he introduced the closed circuit of oscillation into the field of wireless telegraphy and was one of the first to send electric waves in definite directions. That is, to send them toward intended points. Braun’s wireless, closed circuit could send signals over longer distances than those of his contemporaries, because the energy encountered less loss in his circuit. In early wireless transmitters, the antenna was situated directly in the power circuit and broadcasting was limited to a range of about 15km. Braun solved this problem by introducing a sparkless antenna circuit that linked transmitter power to the circuit inductively.

In 1905, Braun went a step further and invented the phased array antenna by arranging three antennas to transmit a direct signal. Braun and his assistants carefully controlled the excitation phase of each of the antennas shown in Fig 13 of Table 1 and determined experimentally that the antenna array exhibited significant directivity. This and the CRT earned Braun the 1909 Nobel Prize in Physics for his contributions to the development of wireless telegraphy, which he shared with Guglielmo Marconi. ¹  Table 1 shows how Braun himself described the phased array when accepting the Nobel Prize:

“two of my assistants found an ingenious solution when they took up the work, at my suggestion, in the Strasbourg Institute. Experiments were carried out on a big parade-ground in the vicinity of Strasbourg (spring of 1905). In Fig. 13 is shown, schematically, the layout used. The field was measured at a fair distance away, that is to say, in the so-called wave-zone. There was satisfactory agreement between theory and observation, and the results were checked in various ways. It was further shown that the experimental layout functioned in the desired sense. By suitable distribution of the amplitudes in the three transmitters, a field as in Fig. 14 was calculated (the singly dotted curve is the measured field). The radial vectors represent the range. If the roles of the thr¹ee transmitters are exchanged – by simply tripping a change-over switch – the preferred direction can be rotated through 120⁰ or 60⁰. It would appear to be of general interest to remark that one is led to the conclusion that the radiation of a transmitter is reduced here by the oscillations in its neighbour, which are shifted in position and phase, a conclusion which could be proved experimentally.”²

1. Table 1:  Ferdinand Braun and an excerpt with figures from his December 11, 1909 Nobel Lecture showing his 1905 phased array antenna ↩︎

Unlike some of his contemporaries, “Braun avoided publicity and sought no personal recognition for his work.  Braun saw his work solely in terms of helping [the] advancement of science.”⁴ This may have been a contributing factor in the reason why Guglielmo Marconi is better remembered as the “Father of Radio,” since the two had shared claim to the 1909 Nobel Prize.

Later Life

Before the outbreak of World War I, Braun was summoned to New York as a witness for a lawsuit regarding a patent claim by the Marconi Corporation against the wireless station of Telefunken at Sayville, New York. Once the war broke out, Braun was detained to the United States, but was given permission to roam freely around Brooklyn. Due to his absence from his laboratory and the onset of illness, Braun was unable to continue his research, but he lived out the rest of his life peacefully in the United States and passed away April 20, 1918.

In the nearly 12 decades since Braun first described the phased array antenna system, this technology has become commonplace in 4G/5G communications, electronic warfare/countermeasures/support, radar, nonlethal weaponry, and military/industrial/medical imaging. Braun’s early innovations continue to inspire new technology today.

Sources

1. Karl Ferdinand Braun – Wikipedia
2. Karl Ferdinand Braun – Nobel Lecture (nobelprize.org)
3. Ferdinand Braun (nndb.com)
4. Biography of Karl Ferdinand Braun | nitum (wordpress.com)
5. Ferdinand Braun, German Physicist – Britannica

Courtesy of Mini-Circuits