Récepteur adapté à facteur de bruit amélioré pour liaison de télécommunication

摘要

943,423. Electric signal amplification systems. SOC. ANON. DE TELECOMMUNICATIONS. Oct. 19, 1960 [March 2, 1960], No. 35874/60. Heading H4R. In an amplifying arrangement requiring the amplifier to be matched to the signal source, the source and a matching resistance are connected to a first network, and the output terminal is taken from a second network, the two networks being interconnected by a plurality of amplifiers in such a manner, that signals from the source are present at the output terminal, but noise from the matching resistance is not. The general case is discussed mathematically. In one particular embodiment, Fig. 3, the first network 14 comprises quarterwave line 16 connected between the source 10 and the matching resistance R 2 , the ends of the line being connected by further quarter-wave lines 17, 18 to the amplifiers 3 1 , 3 2 , whose outputs are connected to input terminals of the network 15 which in this case comprises a further quarterwave line 23, the output signal being taken from terminals 12. It is seen that signals from the source 10 arriving at terminals 12 via the two amplifiers reinforce, whereas noise coming from the resistance R 2 via the two amplifiers cancels out at terminals 12. The impedance is made small at the upper ends of lines 17 and 18, so that at their lower ends they present substantially infinite impedance, and so do not upset the matching of the source 10 to the resistance R 2 . Transformers 20, 201 however cause the line to present a high impedance to the input circuits of the amplifiers which themselves have low impedance. This mismatch helps to reduce noise. In a second embodiment, Fig. 5, the source 27 of resistance R 0 is connected to the centre point of a half-wave line 28, 281 to the ends of which are connected two resistances 26 for matching purposes (these are shown as containing noise sources B 1 ). Amplifiers 3 1 , 3 2 , 3 3 having gain G, 2G, G respectively connect the tappings of the delay line 28, 281 to opposite ends of a quarter-wave line 29 as shown. It is proved mathematically that the current in load 30 consists wholly of signal with no noise from the resistors 26, 261 whilst the current in load 301 consists solely of noise with no signal.