EXTENDED RANGE AUTOMATIC THRESHOLD SETTING CIRCUIT
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2001-Oct-25
In a multilevel digital transmission system, the sampled signal at the receiver is compared to a set of predeter- mined thresholds in order to decide what symbols were transmitted. If the threshold levels at the receiver are fixed, the amplitude of the signal at the detector input has to be constant over the range of received power, temperature and time. This amplitude can be controlled using and AGC amplifer. The requirements for the am- plifier regarding dynamic range, stability and frequency response are not easy to meet, especially in a broad- band transmission device. A possible way to overcome the problem is to provide a measure of the difference between the actual received level and the nominal expected level. With the use of this measure, a threshold level correction is possible; however, its range is limited.