Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1981-07-31
1984-03-20
Tokar, Michael J.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 78E, G01R 2314
Patent
active
044383924
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for sampling and regenerating the carrier frequency of each of the individual pulses in an incoming pulsed carrier frequency signal. The device according to the invention can, for example, be included as a part in a radar receiver, the carrier frequency being situated within the microwave range.
BACKGROUND ART
In, for example, the radar art it is frequently necessary to sample the frequency of the individual pulses in an incoming pulse train to the receiver. This can cause problems, especially, when every incoming pulse has a very short duration and particularly when the carrier frequency varies from one pulse to another. The incoming signal consists, for example, of pulses having mutually different frequency values, which for example, constitutes the signal from different radar stations. The device should after the sampling deliver a signal with the same frequency as the received carrier. Examples of known circuits or systems for this purpuse is described in, for example, the U.S. Pat. No. 3,996,588.
DISCLOSURE OF INVENTION
A general object of to the present invention is to solve such problem. During the duration of a pulse the value of the carrier frequency of the pulse is measured by means of a frequency discriminator, the thus measured value is then supplied to a voltage controlled oscillator as a control quantity. This control quantity is allowed to control the oscillator to a frequency approximately equal to or in the neighbourhood of the received frequency during the short time interval of the carrier frequency pulse duration. During the subsequent longer time interval (or part thereof), when no carrier frequency pulse is received the device works as a closed loop and the voltage controlled oscillator is controlled by the value of a difference signal and is adjusted to a frequency value near the value of the carrier frequency pulse detected during the previous time interval.
The novel and the characterizing of the present device is a track-and-hold circuit and an amplifier connected between the frequency discriminator and the voltage controlled oscillator. A continuous signal which follows the output signal from the discriminator is delivered on the one hand directly and on the other hand via a track-and-hold circuit and the amplifier to a difference forming circuit and during the time interval of the pulse duration. The output signal of the difference circuit controls the oscillator. During the subsequent longer time interval the last measured value from the discriminator is stored in the track-and-hold circuit and the oscillator is controlled in dependence on the difference between a value corresponding to the oscillator frequency and the stored value.
Accordingly, a continuous control of the voltage controlled oscillator is attained already from the beginning of a carrier frequency pulse, i.e. sudden changes in the oscillator control is avoided which implies a more rapid and reliable measuring and adjusting of the carrier frequency.
A specific object of the present invention is thus to provide a device to rapidly and securely sample and regenerate the carrier frequency of received pulses in a pulse train where the carrier frequency can vary from one pulse to another and to give an accurate determined analog counterpart to every detected and measuring frequency, for example in the form of a direct voltage.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be closer described with reference to the accompanying drawings in which:
FIG. 1 shows a block diagram of the device according to the present invention;
FIG. 2 shows a timing diagram in order to explain the function of the track-and-hold circuit which is included in the dvice according to the invention;
FIG. 3 shows a block diagram equivalent with FIG. 1 during the time interval the device forms an open control loop; and
FIG. 4 shows a circuit diagram equivalent with FIG. 1 during the time interval the device forms a closed loop.
MODE FOR CARRYING OUT THE INVENTION
The block di
REFERENCES:
patent: 2905894 (1959-09-01), Rudmann
patent: 3609575 (1971-09-01), Sherry
patent: 3968431 (1976-07-01), Ekstrom
Telefonaktiebolaget L M Ericsson
Tokar Michael J.
LandOfFree
Device for sampling and holding the carrier frequency of short d does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for sampling and holding the carrier frequency of short d, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for sampling and holding the carrier frequency of short d will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1606730