Phase-lock loop controlled object detector oscillator

Details Phase-lock loop controlled object detector oscillator Phase-lock loop controlled object detector oscillator

1981-10-19

1984-07-10

Grimm, Siegfried H.

Oscillators

With device responsive to external physical condition

324236, 324328, 331 4, 331 17, 331 27, 340941, G01V 311, H03L 712

Patent

active

044595611

ABSTRACT:
A vehicle detector installation includes a loop oscillator the loop of which is laid in the roadway and which is locked in operation to a voltage controlled oscillator (VCO). Vehicle detection is effected by a phase detector monitoring the phase difference between the oscillators. The VCO is incorporated in a phase-lock loop (PLL) that is capable of locking to a multiple of a reference frequency oscillator over a range of multiples. To achieve the locking of the loop oscillator to the VCO, means are provided for disabling the normal operation of the PLL and sweeping the VCO over its range of frequency until the phase detector indicates that the loop oscillator and VCO frequencies are equal. This indication activates the PLL to its normal operation to pull the VCO and therewith the loop oscillator to an adjacent multiple of the reference frequency. The PLL is maintained by a repeated charge/discharge cycle of the VCO capacitor that is dependent on the phase of the reference oscillator and the VCO.

REFERENCES:
patent: 3397364 (1968-08-01), Crandall
patent: 3870990 (1975-03-01), Fathauer
patent: 4262264 (1981-04-01), Vandegraaf
patent: 4358749 (1982-11-01), Clark
Kimberley-Jennings, "Metal Detector", Elektor, vol. 5, Jul./Aug. 1979, pp. 7-77, 7-78.

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