Communications: directive radio wave systems and devices (e.g. – Testing or calibrating of radar system – By simulation
Reexamination Certificate
2003-02-27
2004-10-12
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Testing or calibrating of radar system
By simulation
C342S170000, C342S172000
Reexamination Certificate
active
06803877
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a device for generating a desired transit time delay T between a radar signal arriving at the device and an associated pulsed radar signal present at an output of the device, in particular in the microwave range, wherein the transit time delay T corresponds to a certain transit distance S of the pulsed radar signal.
A device of this type is known e.g. from the company leaflet “TE 12283 Abnahme-Testprotokoll” by Alcatel/SEL dated 16 Feb. 1993.
In aviation and seafaring, but also in military defense technology, radar systems are used for detection of moving and stationary objects in the surroundings of the radar system. Radar technology is based on transmitting electromagnetic radiation typically in the microwave range (approximately 10 GHz) and collecting radiation reflected by the object.
In pulsed systems, one can conclude from the transit time of the radiation, i.e. from the time difference between transmission of the pulsed radar signal and detection of the reflected pulsed radar signal, the distance between object and radar system, wherein the radar signal propagates with velocity of light (which depends on the propagation medium). Any frequency shift between transmitted and reflected radiation gives information about the motion (speed) of the object.
To test newly constructed or developed radar systems, use in practice can principally be simulated. Towards this end, the radar system is completely assembled, in particular with radar signal source, transmitting and receiving unit and a radar signal evaluation unit, and operated wherein real objects must be placed at the distances from the transmitting and receiving unit to be investigated. This is very demanding as regards work, time and cost and can in most cases not be realized for larger distances since there should be corresponding visual contact to the target.
For testing, the target can be replaced by a substitute device which receives the pulsed radar signal provided by the radar signal source, stores it and passes it on to the radar signal evaluation unit after a desired time T. The time T thereby simulates the transit time of the radar pulse from the transmitting and receiving unit to the detected object and the associated return path to the transmitting and receiving unit. The time T is therefore designated as transit time delay of the radar signal.
A substitute device of this type thus permits testing of a radar system in a laboratory without having to actually transmit radar signals into the surroundings. In addition to experiments during the development of a new radar system, it is possible to thereby provide an inexpensive proof of the functioning of a radar system which is inexpensive compared to full use in practice. Usually, a purchaser of such a radar system will request such proof from the producer.
In older radar systems, one single radar signal consists of a microwave pulse of uniform frequency during the entire pulse duration (transmitting period). Such radar systems are designated as “narrow-band”.
Substitute devices for narrow-band radar systems are already known e.g. from the company leaflet from Alcatel/SEL, see above. They are based on storing the radar signal in a microwave resonator of high quality which, in the cited company leaflet, is a cavity resonator. After lapse of the desired time T, the radar pulse stored in the resonator (or the associated energy) is transferred to the radar signal evaluation unit. To prevent that the radar pulse looses a significant amount of energy during the time T, the resonance curve of the resonator must be very sharp. In that case, the resonator is suited only for storing radar pulses of a very limited frequency interval, i.e. effectively only of radar pulses of one single frequency. Only when the resonator or its resonance frequency is tuned to the radar pulse or its frequency, it is possible to use a substitute device on the basis of a high-quality microwave resonator for narrow-band radar systems.
Modern radar systems use on the one hand spectrally spread (broad-band) pulsed radar signals, i.e. the frequency and/or phase of one individual radar signal is variable during the duration of the pulse. On the other hand, the center frequency of the transmitting pulse can be changed. Such radar systems are also termed “frequency-agile”. Frequency-agile radar systems have some decisive advantages over narrow-band radar systems.
For narrow-band radar systems, the smallest resolvable distance unit is proportional to the pulse duration of one single transmitted pulse. To increase the range, for modern radar systems, the transmitted signal is expanded at the frequency level and also at the time level to bridge a maximum distance with low peak pulse power. In radar signal processing, the received pulse is again compressed, thereby realizing the desired distance resolution. As a result, frequency-agile radar systems require much less peak pulse power, i.e. smaller amplitude of the transmitted radar signal than narrow-band radar systems with identical distance resolution and identical range.
One further advantage of the frequency-agile radar systems is the reduced interference liability compared with narrow-band radar systems. Narrow-band radar systems can be blinded effectively through overload of the receiving unit by a jammer which transmits at one single transmitting frequency only. Frequency-agile radar systems, however, transmit and receive at a large frequency spectrum such that effective disturbance is much more difficult and requires in particular much more power and a broader transmission spectrum of the jammer.
In a modern frequency-agile radar system which utilizes the pulse compression method, the use of a substitute device on the basis of a resonator, is not possible since it cannot store a broad-band radar signal.
SUMMARY OF THE INVENTION
In contrast thereto, it is the underlying purpose of the present invention to present a device for generating a desired transit time delay T between a pulsed radar signal arriving at the device and an associated pulsed radar signal present at an output of the device, in particular in the microwave range, wherein the transit time delay T corresponds to a certain transit distance S of the pulsed radar signal, with the device also being suited for broad-band radar signals, and wherein in principle transit paths S of the pulsed radar signal which have no upper limit can be simulated.
In accordance with the invention, this object is achieved in a surprisingly simple and effective fashion, in that
a delay line comprising a signal input and a signal output for the pulsed radar signal is provided, whose transit causes a time delay &tgr; of the pulsed radar signal between its input at the signal input of the delay line and its output at the signal output of the delay line,
a signal amplifier with a signal input and a signal output for the pulsed radar signal is connected downstream of the signal output of the delay line, wherein the signal amplifier increases the amplitude of the pulsed radar signal arriving at the signal input of the signal amplifier by a certain amplification factor f, and
a decoupling device is provided which permits supply of at least part of the amplitude of the pulsed radar signal coming from the signal output of the signal amplifier into the signal input of the delay line again, and which permits, after n-fold transit of the pulsed radar signal through the delay line and the signal amplifier, decoupling of at least part of the amplitude of the pulsed radar signal to the output of the device, wherein T=n·&tgr; and wherein n is a natural number.
In contrast to the substitute device on the basis of the resonator, in the inventive device, the pulsed radar signal is delayed mainly through propagation of a pulse in a delay line. Propagation of the pulse does not depend on its frequency spectrum. The pulse in the delay line contains all information of the pulsed radar signal, but does not need to be a radar signal itself.
The inventive design of the device pe
Ludewig Jürgen
Mertens Wolfgang
Hackler Walter A.
Sotomayor John B.
Thales Communications GmbH
LandOfFree
Device for generating a transit time delay of a pulsed radar... 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 generating a transit time delay of a pulsed radar..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for generating a transit time delay of a pulsed radar... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3284109