| 摘要 |
851,229. Superheterodyne circuits. PHILIPS ELECTRICAL INDUSTRIES Ltd. Aug. 21, 1957 [Aug. 24, 1956], No. 26406/57. Class 40(6). In a self-oscillating triode frequency-changer, I.F. regeneration is used and is derived from a choke 18 in the anode circuit of the valve. The aerial is connected to a coil 3 coupled to tuned signal circuit 4, 5, 6. A tapping point on this is connected via a blocking condenser to a tap on the oscillator coupling coil 8 which is a neutral point for local oscillations, the input capacity of the valve being balanced by a condenser 11. The anode circuit comprises tuned oscillator circuit 12, 13 which is back-coupled to coil 8 and is fed via condenser 14 in parallel with the primary 15 of the I.F. transformer, which resonates at I.F. with condenser 14. I.F. regeneration derived from choke 18 in series with primary 15 is applied across the condenser 6. A feed resistor 19 provides I.F. decoupling, in conjunction with condenser 20, and in addition produces negative feedback at low frequencies, permitting the use of a grid leak 10 of large value without danger of squegging. |
