| 摘要 |
1,168,963. Frequency converter. HITACHI Ltd. 27 Feb., 1968 [1 March, 1967], No. 9476/68. Heading H3T. The common emitters of a pair of transistors Q 2 , Q 3 are connected to the collector of a further transistor Q 1 which receives an input signal at its base of frequency fs, one transistor Q 2 of the pair having a resonant feedback circuit arranged between its collector and base to provide oscillation at a second frequency f 0 , and the other transistor Q 3 having an intermediate frequency f i output circuit. The oscillator feedback circuit may involve a timed circuit L 0 C 0 connected to the base of Q 2 and transformer coupled to its collector; or a timed circuit (L 0 C 0 , Fig. 3, not shown) connected to the collector and coupled to the base. Diodes (D 1 , D 2 , D 3 ) supply base bias voltages to the transistors and have associated decoupling capacitors (C A , C B ) and one diode (D 3 ) also acts as a temperature compensating diode. PNP transistors may be used. The arrangement is said to dispense with the need in known circuits for a frequency trap (L 1 , C 1 , Fig. 1, not shown) and an isolating choke (L c ) in the base circuit of Q 2 . |
