From the early 70’s, solid-state pulsed transmitters for primary and secondary radars (IFF-SSR) and also for communications systems (JTIDS) , have used silicon bipolar transistors. With such kind of devices, the common working operation mode was class C for optimizing the overall system efficiency and, consequently, reducing the power dissipation ,. But during the last few years, thanks to the great investments made by the enterprises interested in the mobile phone market, new devices have been developed, the LDMOS transistors. These devices, allow alternative designs to the traditional ones. Most of the manufacturers of solid-state power devices (Philips, MACOM, Integra, APT,...) show datasheets of LDMOS amplifiers working in L-band with better characteristics than bipolar ones, mainly in power gain.
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