Device and method for compensating for a direct voltage offset and for adjusting a decision threshold for optical data transmission networks
First Claim
1. Circuit arrangement for evaluating an information signal comprising an amplifying circuit which has an input for the information signal and an input for a correction value for shifting the level of the information signal, a comparator circuit for comparing the information signal amplified by the amplifying circuit with a threshold value, a first digital/analogue converter for generating the correction value and a second digital/analogue converter for generating the threshold value, a measuring device for ascertaining a first amplitude value of the information signal upstream from the comparator circuit and for determining a second amplitude value of the information signal between the amplifying circuit and the comparator circuit, and comprising a control device which is set up in such a way that it firstly ascertains the first amplitude value by means of the measuring device, determines the correction value as a function of the ascertained first amplitude value and outputs it to the amplifying circuit by means of the first digital/analogue converter and then ascertains the second amplitude value by means of the measuring device, determines the threshold value as a function of the ascertained second amplitude value and outputs it to the comparator circuit by means of the second digital/analogue converter.
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Accused Products
Abstract
Circuit arrangement for evaluating an information signal and a method for adjusting a circuit arrangement of this type.
In particular in optical data transmission networks, disruptive offset voltages can occur in the case of direct current-coupled receiving circuits which may be caused by a basic level of the transmitters of the light signals. Owing to different transmission paths, the amplitudes of the information signals may also be very different, so a different threshold value is necessary for a comparator circuit (8), depending on the amplitude, to recover the bit sequence. For this purpose, the steady component is measured at the input or output of an amplifying circuit (3) in a first step, and depending on this, a correction value is formed for offset compensation and a further measurement of the information signal then takes place at the output of the amplifying circuit (3) in a second step with the correction value superimposed to determine a suitable threshold value for the comparator circuit (8). The correction value or the threshold value is ascertained at each transmitter and stored in a memory arrangement (18, 19). To evaluate the information signal of a specific transmitter, the correction value or threshold value stored for this transmitter is superimposed at the amplifying circuit (3) or the comparator circuit (8).
7 Citations
11 Claims
- 1. Circuit arrangement for evaluating an information signal comprising an amplifying circuit which has an input for the information signal and an input for a correction value for shifting the level of the information signal, a comparator circuit for comparing the information signal amplified by the amplifying circuit with a threshold value, a first digital/analogue converter for generating the correction value and a second digital/analogue converter for generating the threshold value, a measuring device for ascertaining a first amplitude value of the information signal upstream from the comparator circuit and for determining a second amplitude value of the information signal between the amplifying circuit and the comparator circuit, and comprising a control device which is set up in such a way that it firstly ascertains the first amplitude value by means of the measuring device, determines the correction value as a function of the ascertained first amplitude value and outputs it to the amplifying circuit by means of the first digital/analogue converter and then ascertains the second amplitude value by means of the measuring device, determines the threshold value as a function of the ascertained second amplitude value and outputs it to the comparator circuit by means of the second digital/analogue converter.
- 8. Method for adjusting a circuit arrangement for evaluating an information signal comprising an amplifying circuit which has an input for the information signal and an input for a correction value for shifting the level of the information signal, a comparator circuit for comparing the information signal amplified by the amplifying circuit with a threshold value, a first digital/analogue converter for generating the correction value and a second digital/analogue converter for generating the threshold value, a measuring device for detecting a first amplitude value of the information signal upstream of the comparator circuit and for determining a second amplitude value of the information signal between the amplifying circuit and the comparator circuit, and comprising a control device, in which method initially a first amplitude value is ascertained, the correction value is determined as a function of the ascertained first amplitude value and is output to the amplifying circuit by means of the first digital/analogue converter and then a second amplitude value is ascertained, the threshold value is determined as a function of the ascertained second amplitude value and is output to the comparator circuit by means of the second digital/analogue converter.
Specification