S.A. Babunko1, Yu.G. Belov2

1 JSC NPP Salyut-27 (Nizhny Novgorod, Russia)
2 NSTU named after R.E. Alekseev (Nizhny Novgorod, Russia)

1 babunkosa@salut27.ru, 2 bel266@nntu.ru

GaN transistors allow to realize a pulse mode of operation of a high-power amplifier with a continuous input signal in two ways: by changing the gate offset voltage or the supply voltage of transistors. Obtaining the shape of the microwave output pulse, close to a rectangular one, is also possible with continuous voltage supply of the amplifier and switching of its input microwave signal.

The task was to develop a C-band output amplifier with an output power of 100 Watts, which would ensure the formation of short microwave power pulses (lasting from 50 ns to 2 mcs) with signal suppression in the pause between pulses of at least –130 dBm.

Achieving the required high suppression of the output signal in the pause between pulses is impossible due to a change in the offset voltage or switching of the input microwave signal of an amplifier operating at continuously operating transistor supply voltages. In addition, for low power consumption of the amplifier, low power dissipation and low heat dissipation on the transistor structure, the mode of operation with constantly operating supply voltages is also undesirable.

To implement the necessary suppression of output power in the pause between pulses, it was decided to use two methods of generating a radio pulse simultaneously: switching off the supply voltage of the amplifier transistors in the pause between pulses (which gives an attenuation of about 70 dB) together with the manipulation of microwave switches for 100–110 dB of the input signal of the amplifiers – the signal of a frequency synthesizer with a power of about 100 mW.

To improve the pulse parameters, a modulation scheme was developed for the supply voltage of each of the microwave amplifier transistors based on the key chain FETs LTC4442EMS8E (voltage up to 40 V, peak current “pull-up” to power/ground 2.4/5 A, front/rear edge duration 12/8 ns), manufactured by Linear Technology, and their drivers MIC4102YM controls (voltage up to 100 V, propagation delay 30 ns, leading/trailing edge duration 10 ns, TTL-compatible input).

NEDI Technology microwave transistors have been tested: NDNM01136 (30 W, Usup = 28 V) and NDNM01138 (100 W, Usup = 28 V), which showed characteristics at the level of Toshiba transistors (uneven peak of the high-power pulse, duration of the front/rear edges of the microwave pulse, matching in the frequency band). Unfortunately, the possibilities of using transistors of these companies in serial equipment are currently limited.

The analogues of the considered transistors are the components of the Chinese “CTET” company GN5967P25V28 (25 W, 28 V) and GN5967P100V28 (100 W, 28 V). They have a fairly simple structure of matching circuits for input and output, a small number of adjustments, which complicates their matching in the frequency band. These transistors do not have built-in antiresonance circuits.

After adjusting the drivers and matching the microwave transistors, the following results have been obtained: the delay of the front edge of the pulse (relative to the control pulse) is 100 ns, the delay of the rear edge of the pulse is 65 ns, the duration of the front edge is 10 ns, the duration of the rear edge is 5 ns, the unevenness of the pulse top is 20%.

Babunko S.A., Belov Yu.G. Generation of powerful short microwave pulses using an amplifier on GaN transistors. Achievements of modern radioelectronics. 2024. V. 78. № 2. P. 5–12. DOI: https://doi.org/10.18127/j20700784-202402-01 [in Russian]

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