Abstract
Abstract A transistor avalanche noise generator (TANG) is described. It is based on an off-the-shelf RF transistor with an integrated planar monopole. From a 70 V DC power it generates sub-nanosecond pulses with amplitudes close to 1 V. The proposed solution does not employ step recovery diodes, and it is based as the name implies on the operation of a bipolar transistor crossing into the avalanche region. Radiation measurements showed energies close to −40 dBm at frequencies near 600 MHz, with energies reaching the range of 1 GHz.
Highlights
Fast pulse generators have several applications, such as electromagnetic noise generators, medical treatment, Ultra-Wideband (UWB) radars [1], ground penetrating radar (GPR) [2], optical switches [3], etc
A Marx generator based on special avalanche transistors was analyzed in [4], with a total of ten stages and powered with DC voltages from 250 V up to 284 V
A chain of four series-connected power transistor (2N3055) were excited to enter into avalanche mode, generating a 666 V pulse which is connected to a 100 MHz bow-tie antenna [2]
Summary
Fast pulse generators have several applications, such as electromagnetic noise generators, medical treatment, Ultra-Wideband (UWB) radars [1], ground penetrating radar (GPR) [2], optical switches [3], etc. This article covers a broadband noise generator based on an off-the-shelf bipolar device (applications in RF amplifiers), not avalanche transistor It is excited with a moderate (70 V) DC voltage and generates pulses which are extracted by means of a monopole planar antenna, whose spectrum covers reaches up to 2 GHz. Section II of the article covers the circuit and its working fundamentals; section III the respective measured pulse waveform and section IV the radiated energy, measured with a spectrum analyzer. The used transistor has a transition frequency fT of 6 GHz – in theory the higher the fT the higher the generated noise frequency generated by the TANG circuit It has a nominal avalanche voltage (base-collector VCBO) of 20 V.
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