| 摘要 |
An aerial or receptor for a motor vehicle radio receiver has no conventional conductive aerial rod but instead uses a front end circuit C3, L2, C4 coupled with a high gain amplifier TR1 followed by a broad band cascoded stage TR2, TR3, TR4. As electromagnetic radiation is intercepted and passes through C3, L2, and C4 a magnetic field is developed within L2 and also in the associated capacitors. As the RF cycle passes through zero the induced magnetic field within C3, L2 and C4 collapses and a small RF voltage is developed at each end of L2 with 90 DEG phase difference. The high frequency roll off is determined by C4 and the lower frequencies reflect back from C4 through L2 and C3, the resultant signal at the junction of C5, C3 and R1 is in phase. A broadly resonant circuit L1, C2 provides a higher "Q" over selected frequency bands. Further tuned circuits (STC), (Fig 3), may be coupled between C3, L2, C4 and R1 to increase circuit "Q" at selected frequencies. Dynamic noise limiting may be provided by a noise signal processor, (Fig 4), having an input coupled to the output of amplifier TR1 and providing a noise blanking signal. The receptor circuitry may be built into a rear view mirror of a vehicle. <IMAGE> |
