Siemens Aktiengesellschaft

Heinz Merkle

Peter Drebinger

Anton Sunkler

Gerhard Gruenberger

A method and a circuit arrangement for determining the entry and/or exit of a vehicle into or out of a predetermined monitoring zone, which is defined by at least one inductive measuring loop whose change in inductance, which occurs as a result of the entry of a vehicle into the monitoring zone or the exit of a vehicle out of the monitoring zone, is used to control the oscillation frequency of an oscillator circuit is disclosed. In this method a measuring signal which corresponds to the oscillation frequency of the oscillator circuit and a reference signal which corresponds to a reference oscillation frequency are subtracted from one another. The difference signal thus formed is processed in an analysis device for display purposes. In order to achieve a relatively high degree of measuring accuracy, while employing circuit components which possess a relatively low operating frequency, it is provided that the measuring signal which corresponds to the oscillation frequency of the oscillator circuit is obtained and that on the occurrence of a first measuring pulse in a measuring pulse sequence derived from the oscillation signal of the oscillator circuit and with a reduced pulse rate, at the beginning of a measuring interval determined by a preselectable number of measuring pulses, a bistable trigger element is set to emit a specific output signal. On the occurrence of the output signal, which, for the duration of the selected measuring interval, counting pulses are counted with a pulse rate which is high in comparison to the pulse rate of the measuring pulses in a counting pulse counter whose counter signal, which is emitted at the end of the selected measuring interval, is made available as the measuring signal which corresponds to the oscillation frequency of the oscillator circuit.

Method and circuit arrangement for determining the entry and/or exit of

A circuit arrangement for the production of a control signal, in particular a level regulation signal, in a receiving channel which is subject to interference, forms an amplitude-dependent control signal from the phase coded input signal. In the receiving channel a frequency regulating circuit has an oscillator which is synchronized by means of the received signal and the received signal is superheterodyned with the output signal of the oscillator in one mixer, directly, and delayed by 90.degree. in another mixer. The mixed products are then fed through low-pass filters to obtain signals which indicate the frequency shift between the input signal frequency and the oscillator frequency, which signals are converted in a third mixer and serve for tuning the oscillator. The output signals obtained from the outputs of the two first-mentioned mixers, after being fed through low-pass filters, are squared and combined in a difference stage. The result is again passed through a low-pass filter and squared again before being fed to an addition stage. One input of the addition stage is obtained from the output signal of the third mixer, after squaring, and an amplitude correction stage is provided in front of another input of the addition stage to effect cancellation of the signal components arising from phase errors of the frequency regulating circuit and from the noise components in the useful signal. The interference-free output obtained is used as the control signal.

Growing community of inventors

Munich, Germany

Heinz Merkle