RESUMO

Today, the problem of overloading of pulse radar receivers by target return signals is of especially importance because of appearance of new kinds of radio systems of various applications. To prevent the overload, a number of techniques is used, including automatic gain control in dependence on the input signal level, separation of the dynamic range into subranges and multichannel amplification, application of amplifiers with logarithmic amplitude characteristic, etc. Good results are provided by combining a logarithmic amplification with automatic gain control of the signal level. In the paper, a pulse logarithmic amplifier with a time-transit control of the signal gain control operating in the frequency range 1 to 8 GHz is described and its functional diagram and circuit schematic are presented. A compact-size experimental mockup of the device has been developed with the use of the modern circuitry which extends essentially its application capabilities. The physical principles of selecting the necessary bandwidth, not producing distortions in the radio pulse spectra and dynamic operation mode of the time-transit automatic gain control, are considered. Experimentally obtained amplitude curves are presented. The mockup parameters are as follows: the gain factor K0 within the linear range is ~53 dB; dynamic range of the input signals makes ~55 dB; the input and output resistances are Rin ≈ Rout = 50 Ω; and supply voltages are ±12 V (current consumption 100 mA) and ±5 V (current consumption 20 mA)