Communications: directive radio wave systems and devices (e.g. – Determining distance – With frequency modulation
Reexamination Certificate
1995-01-12
2001-05-15
Lobo, Ian J. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Determining distance
With frequency modulation
C342S109000
Reexamination Certificate
active
06232911
ABSTRACT:
BACKGROUND OF THE INVENTION
The application refers to a device for distance measurement by radar comprising a frequency modulated radar-transmitter and -receiver by which a radar beam is guided onto an object to be measured and which, by mixing of the transmitted frequency with the received frequency, delivers a beat signal; frequency modulating means, by which the transmitted frequency of the radar signal of the doppler signal device is periodically variable in a saw-tooth shaped way and wherein the frequency of the beat signal, due to the travel time of the radar beam reflected by the object, is a measure for the distance of the object, and a signal processing circuit generating a measured value from the beat signal obtained.
Devices of this kind are known. In the radar-transmitter and -receiver mixing takes place of the transmitted and the received signal. The signal received has passed the distance to and from the object, thereby has been transmitted at an earlier instant and thereby has, due to the saw-tooth modulation, a frequency which is a bit different from the frequency of the signal which is emitted at the moment of reception. Thereby a beat frequency occurs. This beat frequency is proportional to the travel time to the object and thereby to the distance from the object to the radar-transmitter and -receiver.
SUMMARY OF THE INVENTION
It is an object of the present invention in a device as defined above, to simplify and to improve measurement and display of the beat frequency.
According to the invention the solution of this problem is achieved by locking the beat signal onto a phase locked loop circuit the output frequency of which forms the measured value of the distance.
The beat signal usually has a high noise factor. Due to nonlinearities of the mixer frequency variations or fluctuation will occur. The beat signal is made of individual signal groups corresponding to the slowly rising edge of the “saw-tooth”. In the area of the steep edge of the saw-tooth beat signals of high frequency occur. By use of a phase locked loop circuitry throughgoing signals are generated, gaps are bridged and frequency fluctuations are averaged. The noise component is low. Signals of this kind can be processed easily.
In a further embodiment of the invention in addition to the distance measurement device a velocity measurement device made up with a doppler signal device may be provided and the distance- resp. -velocity measured values, delivered by the distance measurement device and the velocity measurement device, may be combined.
A combined distance- and velocity- measurement device as set out offers a plurality of applications as will be explained below.
Further embodiments of the invention are subject matters of the subclaims.
An example of the invention is described in detail below with reference to the drawings.
REFERENCES:
patent: 4079377 (1978-03-01), Zur Heiden et al.
patent: 4205314 (1980-05-01), Strauch
patent: 4245221 (1981-01-01), Kipp et al.
patent: 4429309 (1984-01-01), Kipp
patent: 4739330 (1988-04-01), Lazarus
patent: 5072223 (1991-12-01), Hethuin et al.
Creighton Wray James
Lobo Ian J.
Narasimhan Meera P.
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