The latest experiment, carried out by the defence contractor China Electronics Technology Group (CETEC), concentrated on a larger, single aircraft which was brought down while flying 1,500 metres (4,920ft) above sea level.

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“It will put us on par with the Americans,” said Professor Gao Huailin and colleagues from the Chinese Academy of Sciences in the paper published in Scientia Sinica Physica, Mechanica & Astronomica on Tuesday.

The idea of an EMP weapon was initially proposed by nuclear scientists, who said a bomb could use powerful electromagnetic waves to cripple a city by disabling all electronic devices in a given area rather than killing people.

Researchers have already developed devices that can generate powerful energy beams in a lab, and some of these are now being tested in the open to evaluate their military potential.

One US prototype, the Tactical High Power Microwave Operational Responder, or Thor, is capable of defending a military base from attack by a swarm of drones, as the 2019 experiment showed.

Another prototype, the Counter-Electronics High-Power Microwave Extended-Range Air Base Air Defence (Chimera) has been designed to hit targets from a longer distance, according to the US Air Force.

Other countries — including Germany, France, Russia and South Korea — are working on similar devices.

In the Chinese experiment, the researchers said the drone behaved unexpectedly after the pulse weapon was fired.

It did not drop immediately, but veered abruptly from one side to another for a period.

Flight data and analysis of debris recovered from the crash site suggested that sensitive electronic devices, including its satellite navigation system, cryoscope, accelerometer, barometric altimeter and communication device, had not been damaged.

The battery and motors also functioned properly until collision.

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The most likely explanation is that “the flight control system malfunctioned, issuing an error control command,” CETC engineer Wen Yunpeng and colleagues wrote in the paper.

The distance between the EMP weapon and the target was not disclosed. Wen and colleagues said that the weapon operated within a narrow band, which means the microwave beam it generated was designed to give it a longer firing range.

Although the experiment only involved one aircraft, they said the weapon would have “a significant advantage against swarms of drones”.

Given the limited energy available on a battlefield, EMP weapons need to find ways to ensure that high-voltage bursts can be released as quickly as possible to be effective.

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Scannable QR code appears in sky above China’s Shanghai

Scannable QR code appears in sky above China’s Shanghai

Researchers in China and other countries have long used a simple device known as the Tesla coil to amplify the voltage with the help of a magnetic field.

But in recent years they have switched to a capacitor-based device known as a Marx generator to produce electric currents with up to two million volts, considerably higher than those generated by a Tesla coil, according to Gao and colleagues.

Though the highest reported output power around the world was about 20 gigawatts, Gao and colleagues said their calculations suggested the peak performance of the best American EMP weapons such as Thor could be as high as 80GW, adding that upgrades would get Chinese weapons close to that level.

The Chinese EMP weapons are based on the design of their American counterparts, but with some technical innovations to achieve a high performance for a relatively low cost, according to the researchers.