What is an X-band radar?
A radar is a device that emits a radio wave and receives its reflection to measure the distance between the radar and the object in question and to detect the direction in which the object is located. Radars are classified roughly into 11 types, including L-band, C-band, and X-band, according to the frequency in use.
Conventional weather radars designed to observe rain and snow used to be C-band radars (4‒8 GHz). Recently, however, demand has been high for high-resolution weather radar that enables accurate observation of torrential rain to make use of the observation results for disaster prevention/responses related to floods and landslides. As a solution to this challenge, engineers have been working on the development of X-band radars operating in the range from 8 to 12 GHz above the frequencies used by C-band radars. Conventional X-band radars primarily used vacuum-tube devices to amplify output signals. However, in recent years, an increasing number of radars have begun to use gallium nitride high-electron-mobility transistors (GaN HEMTs).
What are the features of the newly developed GaN HEMT?
(1) Extended service life
In the newly developed GaN HEMT, Sumitomo Electric achieved high power and high efficiency in the X band, by optimizing the device's transistor structure and layout. Vacuum tubes used in the transmitters of conventional radars increased radar running costs due to their short replacement cycles, which were generally two to three years. Incorporation of GaN HEMTs in transmitters eliminates the need for device replacement.
(2) Low noise
Vacuum tubes were subject to a poor signal-to-noise ratio, which posed the problem of a high likeliness of the interference of radio waves transmitted by radar with other radio communication systems. Use of superb low-noise GaN HEMTs solves this problem.
(3) Delivers high power and covers a wide band
The new 200 W GaN HEMT operates in a wide band from 8.5 to 9.8 GHz, making it suitable for various radars operating at different frequencies.
Mass production of the GaN HEMT began in July 2015. Due to the aforementioned features, this product has been adopted by models produced by several radar manufacturers. Its applications include harbor surveillance radars, which monitor ships for marine traffic safety, and onboard radars, as well as weather radars.
What motivated you to develop this product?
Conventional radars mostly used vacuum tubes. Customers wanted radars incorporating long-life semiconductors.
In 2013, Sumitomo Electric launched 100-W power class products incorporating GaN HEMTs, which have been selected by our customers in Japan and abroad. However, to downsize the amplifier and reduce components, our customers demanded devices with higher power.
To positively respond to this demand, I embarked on the development of a high-power product using a GaN HEMT operating at 50 V in place of the 24 V operation GaN HEMT used in the 100 W power class product.
What responses have you had from customers?
To build a 1 kW or 2 kW amplifier, it is necessary to synthesize power from multiple HEMT devices. Compared with conventional 100 W class products, the 200 W HEMT cuts the power synthesis stages in half to gain the same power. This has been favorably accepted by our customers in Japan and abroad pleased with the system downsizing and weight reduction.