High-frequency oscillators with the output power of units-tens of watts

Practical oscillator circuit (Fig.1) transistor KPA in the frequency range 30...80 MHz was provided by pout=2.5 W. A similar circuit on the transistor CPA had pout=20 W at a frequency of fo=4 MHz and PI=52 In (power consumption of 36.4 W, dissipation 15 watts). The values of L2=5,6 MH, C2=760 pF, R=2 ohms.

Fig.1

At low frequencies with high power output (units-tens of watts) in the generators can be used ninasimone composite transistors in which high-power FETs manages more powerful bipolar transistor. In Fig.2 prodana diagram of the crystal oscillator based on the composite transistor.

Fig.2

In Fig.3 presents the dependence of the supply current and output power of temperature. The maximum changes in these parameters did not exceed 2.3 and 3.5% respectively when the temperature changes from 25 to 70°C. When the angle of the cut-off drain current Q=70°, the generator produced a power output of 10 W at a total efficiency of 65%. Frequency generation 7,41 MHz, the average clock frequency instability was less than 2*10-7.

Fig.3. The dependence of the consumed current (1) and output
power (2) from the ambient temperature.

Fig.4. The levels of phase noise of oscillators on the powerful MESFET (1)
Microwave bipolar transistors (2) and Gunn diodes (3)

Thus, the oscillators on the powerful FR cover practically all used frequency bands. For a number of applications are important levels of phase noise of oscillators. As follows from Fig.4, this parameter microwave generators for GaAs powerful MESFET inferior to the generators of microwave bipolar transistors and diodes Gunn. Is expected to decrease the level of modulation noise by 20 dB at the design of high power MESFET with submicron channel length.

Literature

Circuitry devices on a powerful field-effect transistors. Guide. Under the editorship of V. P. Dyakonov.

Publication: N. Bolshakov, rf.atnn.ru