SU1587548A1 - Logarithmic amplifier - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to reduce the recovery time and increase the frequency selectivity. To do this, in a logarithmic amplifier containing N amplifiers - limiters 1, serially connected frequency-selective circuits 3 and limiters 4 of the signals from the bottom are entered into the input circuits of the N-input adder 2. This provides a better frequency selection of the signals and reduces the recovery time of the sensitivity of the amplifier, since the signals whose amplitude is below the limiter limit of limiter 4 do not pass to the output of the amplifier. 1 hp f-ly, 1 ill.

Description

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The invention relates to radio engineering and can be used in devices whose input signals vary in a wide dynamic range.

The purpose of the invention is to increase the saturation selectivity.

The drawing shows an electrical structural diagram of the logarithmic amplifier.

The logarithmic amplifier contains N uspitel-limiters 1, output N-input adder 2, N frequency-selective circuits 3 and N limit, le 4 signals from the bottom.

The logarithmic amplifier works as follows.

The input signal is amplified in N amplifiers of x-limiters 1. The output signals of N limiter amplifiers pass through the corresponding N-e frequency-selective circuits 3 and the corresponding N limiters of 4 signals from below, are summed in the output N-input adder 2 and are output to the device.

The amplitude-frequency characteristic of the logarithmic amplifier is given by N frequency-selective circuits 3. The N-limiter amplifiers have a bandwidth substantially greater than the bandwidth of the N-x frequency-selective circuits 3.

The device's bandwidth weakly depends on the input signal level, since the bandwidth broadening in the x-limiter amplifier with increasing input signal level no longer affects the resulting device bandwidth. N limiters 4 signals below provide extra

suppression of the spectral components to the input signal Qx, which are outside the device bandwidth, do not pass them to the input of the output N-input adder 2.

To reduce the level of non-linear distortion of the output signal, the threshold N-ro of the signal limiter from below can be chosen close to zero. However, the frequency selectivity of the proposed device is somewhat impaired.

Claims (2)

1. A logarithmic amplifier containing N series-connected limiting amplifiers, the output of each of which is connected to the corresponding frequency-selective circuit, and the output N-input adder, and the input of the first amplifier limiter is: the input of the log- ricative amplifier, l and lover in order to reducing the recovery time and increasing the frequency selectivity, between the output of the i-th frequency-selective circuit and the ith input of the output N-input adder, the i-th signal limiter is inserted from the bottom, while the bandwidth of the i-ro limiter amplifier is much larger than the bandwidth i-th frequency-selective chain, where i 1,2, ..., N.. 2. The amplifier according to claim 1, about tl and - due to the fact that the threshold for limiting the L th signal limiter from the bottom is chosen close to zero;