| 摘要 |
<p>1278345 Repeaters; transistor amplifying circuits WESTERN ELECTRIC CO Inc 4 June 1970 [9 June 1969] 26963/70 Headings H3T and H4R A transmission system for transmitting a plurality of signals in multiplex form includes a plurality of serially connected repeater amplifiers which inherently generate third order intermodulation signals wherein some of the repeater amplifiers are adapted to generate third order intermodulation products which at least partially cancel the products generated by the other amplifiers. Each of the repeater amplifiers includes at least a final transistor amplifying stage whose load resistance is varied to alter the phase angle of the third order intermodulation products. To change the phase angle by an angle of 120-240 degrees the load resistance must be at least doubled and use of repeater amplifiers giving the required conditions also reduces the power requirement. As shown the two types of repeater amplifiers A, B alternate consecutively along the line but it is possible to use a plurality of type A amplifiers followed by a plurality of type B amplifiers to give the required performance. An equivalent circuit for a repeater amplifier in a common emitter configuration is discussed, Fig. 4 (not shown). In Fig. 6 (not shown) an arrangement for investigating the change in third order product phase angle with changes in transistor bias voltage and load resistance is shown.</p> |
