CS245238B1 - Solid correcting network connection in digital signal's repeaters - Google Patents

Abstract

The solution concerns the connection of a fixed corrector in repeater transmission systems with digital signal. Signal from output automatically controlled concealer (AK) is brought to non-inverting differential amplifier input (DZ). To achieve the desired frequency during the voltage amplification of the solid the corrector is from the differential output (3) amplifiers (DZ) introduced frequency-dependent negative feedback on its inverting input. Negative reverse in circuit links are used by two links (H4, R3, Cl and R6, R5, C2). One article works in the lower frequency range, the second Article operates in the upper frequency range. It is advisable to connect a fixed corrector for transmission systems with tens kbit / s.

Description

The invention relates to the connection of a fixed concealer in repeaters of digital signal transmission systems.

At the repeater input is connected a corrector adjusting the shape and amplitude of distorted incoming pulses to pulses suitable for further processing in the digital circuits of the repeater. The concealer consists of a cascade connected automatically controlled variable concealer, a fixed concealer, and a broadband amplifier. The automatically controlled variable corrector corrects cable attenuation changes due to the range of cable lengths between repeaters and cable attenuation changes due to temperature fluctuations and cable aging. The fixed corrector corrects the attenuation of the nominal section cable length between repeaters. The final wideband amplifier amplifies the corrected pulses to the value required for further processing in the digital circuits of the repeater.

The known fixed corrector circuit comprises a common-emitter transistor having correction elements in both the collector circuit and the emitter circuit. The voltage gain is determined by the ratio of the impedance in the collector circuit to the impedance in the emitter circuit of the transistor. The disadvantage is that inductor is connected in the collector circuit. This circuit has a small voltage amplification. Therefore, it requires a high gain terminal amplifier that is circumferentially complex.

Another known fixed concealer connection is formed by multi-stage negative feedback amplifiers introduced from the fixed concealer output to its input. With this frequency-dependent negative feedback, the desired frequency feedback is achieved

245 238

- 2 concealer transfer progress. The disadvantage of this connection is the necessity to ensure the stability of the multi-stage amplifier - interference immunity. To ensure stability, it is necessary to achieve some feedback loop transmission over a much wider frequency band than is required for pulse transmission. Therefore, additional correction elements need to be connected, but they must not affect the voltage gain in the transmission frequency band.

The purpose of the invention is to overcome these disadvantages. According to the essence of the invention, this is achieved by connecting a non-inverting differential amplifier input to the output of the automatically controlled corrector whose inverting input is connected via a second resistor to ground and a first resistor, a third resistor and a first capacitor to ground. the resistance is through the fourth resistor and the second capacitor connected to ground. The common point of the fourth and fifth resistors is connected via the sixth resistor to the output of the differential amplifier, which is the output terminal of the wiring.

The fixed concealer circuit according to the invention does not contain any inductances and is therefore suitable for integrated circuit technology. The wiring does not require any additional elements to ensure its stability. There is no need to use a broadband amplifier.

An example of wiring is further described in the drawing. Automatic input corrector AK is connected to input terminal 1, the output of which is connected to the non-inverting input 2 of the differential amplifier DZ. The inverting input of the differential amplifier DZ is connected through a second resistor R2 to ground and through a first resistor R1. a third resistor R3 and a first capacitor C1 to ground. Common point of the first and third resistance Rl. R3 is through the fourth resistor R4. the fifth resistor R5 and the second capacitor C2 connected to ground. Common point of the fourth and fifth resistance R4. R5 is connected to the output of the differential amplifier DZ via the sixth resistor R6. which is the output terminal J of the wiring. The output of the automatic corrector OK control circuit is connected to the output terminal J. the output of which is connected to the control input of the automatically controlled concealer AK.

A signal is supplied from input terminal 1 via an automatically controlled concealer AK. whose transmission characteristic is controlled by the OK circuit of the automatic concealer control, to the input 2 of the fixed concealer.

To obtain the desired frequency response of the fixed corrector voltage amplifier, DZ is output from output 3

245 238 introduced a frequency-dependent negative feedback on its inverting input. Two links R4 are used in the negative feedback circuit. R3. Reverse phase shift C1 and R6, R5, C2 and a resistive divider from the first and second resistors R1, R2. The reverse phase shift cells are designed so that one cell operates in the lower frequency range and the other in the upper frequency range. This achieves a monotonic increase in the voltage gain of the fixed corrector over the entire frequency range necessary for pulse correction. By selecting the first to sixth resistors R1 to R6, the first and second capacitors C1, C2, a steep voltage amplification in the range of 0 to 6 d3 / oct can be achieved. At high frequencies, both capacitors C1, C2 cease to apply. The negative feedback circuit transmission is determined only by the first to sixth resistors R1 to R6 and the phase shift with increasing frequency approaches 0 °. The phase characteristic of the whole feedback loop is then determined only by the properties of the differential amplifier DZ. The output terminal J receives corrected pulses. Since the voltage gain of the fixed corrector is substantially greater than one in the transmission band, a sufficient signal size is output at its output for further processing in the digital circuits of the repeater. There is no need to use a broadband amplifier.

The connection of the fixed concealer is particularly suitable for small transmissions. speed - tens of kbit / s, when the slope of the cable section of the nominal length reaches a value of maximum 6 dB / oct. in the frequency range two to three decades wide.

Claims (1)

Fixed concealer connection in digital signal repeaters vyznač characterized in that a non-inverting input (2) of a differential amplifier (DZ) is connected to the output of the automatically controlled concealer (AK), the inverting input of which is connected via a second resistor (R2) to ground the resistance (R1), the third resistance (R31 and the first capacitor (C1) to ground), where the common point of the first resistance (R1) and the third resistance (R3) is across the fourth resistance (R4), the fifth resistance (R5) and the second capacitor (C2 ) connected to ground, while the common point of the fourth resistor (R4) and the fifth resistor (R5) is connected to the output (3) of the differential amplifier (DZ) via the sixth resistor (R6).