Circuit arrangement for establishing weighting coefficients in an analog-type adaptive equalizer
First Claim
1. A weighting network for an adaptive equalizer inserted between a transmission channel and a load for processing incoming high-frequency signals by multiplying their amplitudes by selected analog coefficients, comprising:
- input means for receiving the high-frequency signals to be processed;
output means for emitting the processed high-frequency signals;
a control terminal for receiving a corrective voltage determining a selected analog coefficient;
a bridge circuit inserted between said input and output means, said bridge circuit including two impedance elements having an electrical resistance indirectly variable by an external energy field;
a source of constant reference current connected to each of said impedance elements for generating a voltage drop, proportional to said resistance, thereacross;
a pair of energy emitters respectively juxtaposed with said impedance elements;
amplifier means connected to said terminal and across said energy emitters for differentially exciting same to unbalance said bridge circuit in response to said corrective voltage; and
feedback means connected between said impedance elements and said amplifier means for stabilizing the excitation of said energy emitters in response to the voltage drop across the respective impedance elements.
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Abstract
An adaptive equalizer for a telecommunication system, designed to process high-frequency signals in a band on the order of 50 MHz, comprises several weighting networks with input connections to respective taps of a delay line and with output connections to a summing amplifier, each weighting circuit having a control input to which a selected corrective voltage is applied. Each weighting network includes a bridge with two arms constituted by respective secondaries of an input transformer and two other arms in the form of indirectly variable resistance elements, specifically photoresistors photoelectrically coupled to a pair of light-emitting diodes, capacitively isolated for direct current from other parts of the bridge. Energization of the control input with corrective analog voltage of either polarity unbalances the bridge by differentially exciting the light-conductive diodes through respective operational amplifiers also receiving feedback signals derived from the voltage drops across the associated photoresistors which are traversed by constant currents.
11 Citations
6 Claims
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1. A weighting network for an adaptive equalizer inserted between a transmission channel and a load for processing incoming high-frequency signals by multiplying their amplitudes by selected analog coefficients, comprising:
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input means for receiving the high-frequency signals to be processed; output means for emitting the processed high-frequency signals; a control terminal for receiving a corrective voltage determining a selected analog coefficient; a bridge circuit inserted between said input and output means, said bridge circuit including two impedance elements having an electrical resistance indirectly variable by an external energy field; a source of constant reference current connected to each of said impedance elements for generating a voltage drop, proportional to said resistance, thereacross; a pair of energy emitters respectively juxtaposed with said impedance elements; amplifier means connected to said terminal and across said energy emitters for differentially exciting same to unbalance said bridge circuit in response to said corrective voltage; and feedback means connected between said impedance elements and said amplifier means for stabilizing the excitation of said energy emitters in response to the voltage drop across the respective impedance elements. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification