公开(公告)号：US3575662A

公开(公告)日：1971-04-20

申请号：US3575662D

申请日：1968-06-21

申请人： ARVIN IND INC

发明人： DAVISSON ELDEN R

IPC分类号： H03J7/26 ,  H03J3/18 ,  H04B1/28

CPC分类号： H03J7/26

摘要： A circuit for use in electronically sweeping the tuning capacitors of a radio receiver through their capacitance range for successively tuning in each station. The sweeping action stops automatically and the value of the tuning capacitors are held constant at each station which is picked up by the radio. The sweep function is restarted to drive the tuner toward the next higher frequency station by means of a manually operated switch. The tuning capacitors comprise voltage variable capacitance diodes which are varied by means of a ramp voltage supplied by a generator. The generator is formed by a PNP transistor which charges a capacitor to provide the ramp voltage, and by a first field effect transistor which controls the base current of the PNP transistor. A silicon controlled rectifier is connected in parallel with the capacitor at the output of the ramp generator to discharge the capacitor after it has reached the peak voltage level required to vary the diode''s capacitance. In the case of an FM radio, said first field effect transistor has its gate electrode coupled for bias control by a ratio detector in the IF strip of the FM receiver. The output of the ratio detector causes the ramp voltage to level off, when a station is tuned in, by establishing the currents in the transistors so that the charging current to the ramp generator capacitor ceases, thereby holding constant the voltage to the tuning diode. In the case of an AM radio, the IF frequency developed in the AM receiver is passed through a series circuit formed by a narrow band filter, an amplifier, and a rectifier, to provide a DC voltage which is applied to the base electrode of the PNP ramp generator transistor. The DC voltage at said base electrode becomes more positive as a station is tuned in, and the PNP transistor decreases its conduction so that the ramp function ceases and the output voltage to the tuning diodes remain constant.

公开(公告)号：US3559072A

公开(公告)日：1971-01-26

申请号：US3559072D

申请日：1968-03-18

申请人： ARVIN IND INC

发明人： DAVISSON ELDEN R

IPC分类号： G04C23/00 ,  H03K17/284 ,  H03K17/292 ,  H03K17/72 ,  H03K17/28 ,  H04B1/16

CPC分类号： H03K17/72 ,  G04C23/00 ,  H03K17/284 ,  H03K17/292

摘要： ELECTRONIC SWITCHES CONTROLLED BY RC TIMING CIRCUITS FOR COMBINATION WITH A RADIO OR THE LIKE TO PROVIDE TIMED PLAY PERIODS OF THE RADIO. IN ONE EMBODIMENT THE SWITCH COMPRISES A SEMICONDUCTOR HAVING ITS PRINCIPAL CONDUCTING ELEMENTS CONNECTED IN SERIES WITH THE LOW VOLTAGE RECEIVER STAGES AND LOW VOLTAGE POWER SUPPLY OF A RADIO. AN RC TIMING CIRCUIT IS COUPLED TO THE CONTROL ELECTRODE OF THE SEMI-CONDUCTOR TO TURN IT OFF AFTER A TIMED INTERVAL FROM ITS TURN ON TIME. IN A SECOND EMBODIMENT THE ELECTRONIC SWITCH COMPRISES A SEMICONDUCTOR HAVING ITS PRINCINPAL CONDUCTING ELECTRODES COUPLED BETWEEN THE LOW VOLTAGE POWER SUPPLY AND THE AUTIO INPUT TO THE VOLUME CONTROL POTENTIOMETER OF THE RECEIVER. AGAIN, AN RC TIMING CIRCUIT IS COUPLED TO CONTROL CONDUCTION OF THE SEMICONDUCTOR WHICH SHORTS OUT THE AUDIO SIGNAL AFTER A TIMED INTERVAL.