Major advances in microwave device development in recent years have enabled a transition to solid-state power amplifiers (SSPA) for wireless communications and radar systems in microwave to millimeter-wave bands. In particular, SSPAs are rapidly replacing electronic tube amplifiers, such as magnetron and traveling-wave tube-based amplifiers (TWTA), for base stations of mobile phones using L- and S-band, and for satellite communications and base stations for terrestrial communications at C- to Ku-band frequencies.
The advantages of SSPA include: 1) the ability to reduce size and weight of devices including the power supply; 2) the ability to reduce spurious signals; and 3) longer-life than electronic tubes (even though technology advances have recently extended the life of tube-based amplifiers). With the spread of multi-carrier modulation and growing requirements for high capacity digital data communications, there has been strong demand for higher power amplifiers, as well as lower distortion for communications applications (see Figure 1).
Figure 1 Demand for higher power FETs for communication equipment.
Higher power amplifiers are in demand for radar systems as well, to expand the detectable range, improve detection of smaller targets and meet electronic countermeasure (ECM) requirements. Moreover, downsizing of power amplifiers has been expected yearly for both communications and radar systems applications to improve mobility and portability, and to relax installation and mounting conditions (see Figure 2).
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