330 W LDMOS Power Transistor for L-band Radar
The intense pressure on wireless service providers to reduce cost at every level while maintaining or even increasing performance has produced some notable achievements. One of the most impressive is in LDMOS RF power transistors, which today deliver higher RF power, gain and efficiency than their predecessors. Although perhaps less obvious than the highly visible wireless applications, radar systems used for air traffic control, surveillance and weather monitoring benefit just as much from these advances because they employ large numbers of RF power transistors to produce extremely high output levels. The 50 Volt MRF6V14300H LDMOS FET from Freescale Semiconductor further extends LDMOS device performance by producing 330 W at L-band frequencies between 1200 and 1400 MHz, with 60 percent drain efficiency and 17 dB of gain, which are the best figures of merit to date from a single device at these frequencies.
The MRF6V14300H is the first in a family of 50 V LDMOS FETs designed for avionics and radar applications that will be expanded later with additional models. The MRF6V14300H joins the company’s portfolio of 50 V devices that cover frequencies of 10 to 1400 MHz with RF output power up to 1 kW. They are based on Freescale’s sixth-generation, very-high-voltage (VHV6) technology, which, since first introduced in 2006, has among other advances resulted in the industry’s first 1 kW LDMOS RF power transistor. Models in the 50 V family are tailored for applications ranging from industrial, scientific and medical systems to analog and digital broadcast transmitters, as well as radar and other avionics systems.
The MRF6V14300H was introduced with a new driver, the MRF6V10010N, which delivers 10 W output power between 960 and 1400 MHz. When used along with a Freescale MMG3014N pre-driver, the devices can substantially reduce the number of RF power transistors and gain stages required to deliver a given RF output power. For example, a three-stage line-up using these devices to produce a peak RF output power of 330 W at 1400 MHz (300 μs pulse, 12 percent duty cycle) produces 62 dB of total gain while drawing 11.2 A. Overall efficiency is 58 percent with all three stages and associated matching losses. This performance is considerably greater than previously achieved and allows amplifiers to be designed with a smaller footprint, higher efficiency, require less heat sinking and cooling overhead, reduce system power consumption, and lower the overall bill of materials. These advantages are further multiplied when applied to the high RF output levels typically produced by L-band radars, which use many RF power transistors.
The MRF6V14300H and MRF6V10010N employ electrostatic discharge (ESD) protection (as do all -50 V LDMOS devices from Freescale), which make them less susceptible to damage on assembly lines. It also produces a very wide gate voltage swing (–6 to +10 V) that is important when the devices are operated in higher efficiency modes such as Class C. The devices also benefit from very low thermal resistance (with a junction temperature of less than 0.13° C/W for the MRF6V14300H), which reduces the cooling requirements of the transmitter.
The MRF6V14300H is housed in an NI-780 air-cavity ceramic package, is internally matched, and can withstand a maximum VSWR of 3 at 1400 MHz when operating at 50 V and producing 330 W. The MRF6V10010N is housed in a fully-overmolded plastic PLD-1.5 package and can withstand a maximum VSWR of 10 at 1400 MHz when operating at 50 V and producing 10 W. Both devices are RoHS compliant. Key performance parameters for the devices are shown in Table 1. The MRF6V10010N is currently in production and samples of the MRF6V14300H are available, with production expected in the third quarter. Large-signal models will be available late in the year for both devices, and a broadband reference text fixture is currently available for the MRF6V14300H.
RS No. 305