Communications: directive radio wave systems and devices (e.g. – Determining distance
Patent
1998-03-09
2000-04-18
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Determining distance
342128, 342129, G01S 1332
Patent
active
060520809
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to an apparatus for distance measurement.
A continuous wave radar, which is also referred to as FMCW radar. is known from the Prior Art of Meinke, Gundlach, Taschenbuch der Hocfrequenztechnik, 5.sup.th Edition, Springer-Verlag, Chapter S 3. The abbreviation FM stands for frequency modulation and CW stands for continuous wave. FIG. 1 shows such a continuous wave radar. A modulator MOD generates a modulating signal that is supplied to a voltage-controlled oscillator VCO. An optimally linearly frequency-modulated signal should be adjacent at the output of the voltage-controlled oscillator VCO. Insofar as the frequency-voltage characteristic of the voltage-controlled oscillator VCO exhibits a non-linearity, referenced NLIN in the f-u diagram, the modulating signal stemming from the modulator MOD is to be correspondingly pre-distorted, as indicated with the signal curve VNLIN in the u-t diagram of the modulator MOD. When the voltage-controlled oscillator VCO exhibits a linear characteristic LIN, a linear characteristic is to be selected for the modulator MOD. The linearly frequency-modulated signal stemming from the voltage-controlled oscillator VCO is conducted over a circulator ZIR and beamed out by an antenna A. The beamed-out signal is reflected by a test subject MO located at the distance I from the antenna A and is received by the antenna A. This received signal proceeds via the circulator ZIR onto a mixer MI that mixes this received signal with the transmission signal present at the moment. The difference frequency .DELTA.f.sub.DIF (t) is a measure for the distance L of the test subject MO from the antenna A. Measuring errors arise, however, when the frequency-modulated transmission signal deriving from the voltage-controlled oscillator does not exhibit a linear f-t characteristic.
A correction of the non-linearity of the f-u characteristic of the voltage-controlled oscillator VCO is not always possible or involves a high outlay.
An object of the invention is to specify an apparatus for distance measurement wherein a potentially existing non-linearity in the frequency-modulated output signal of the voltage-controlled oscillator remains without influence on the measuring precision.
The object is achieved by an apparatus according to patent claim 1.
Advantageous developments of the invention derive from the subclaims.
When the isolation of the circulator is too low, a further antenna can be provided that serves for the reception of the reflected signal. This development is recited in claim 3.
When transmission power is to be prevented from also being adjacent at the mixer, a circulator can be connected between the signal source, the mixer and the antenna, see claim 4 with respect thereto. The development according to claim 3 also fulfills this purpose.
The development according to claim 5 has the advantage that a major part of the sensor components can be operated in a lower-frequency range with reference to the transmission frequency. This is more manipulatable in practice.
The development according to claim 6 likewise serves for better manipulation when the signal source generates a signal whose frequency is higher than the frequency at which the signal processing should ensue.
The development according to claim 9 serves for the suppression of noise sources. Additional, neighboring apparatus for distance measurement can be distinguished from one another with this development.
The invention is explained in greater detail below with reference to a number of Figures.
FIG. 1 shows a continuous wave radar as known from the Prior Art.
FIG. 2 shows the basic structure of the inventive apparatus for distance measurement.
FIG. 3 shows a further embodiment of the inventive apparatus for distance measurement.
According to FIG. 2, the inventive apparatus for distance measurement comprises a signal source SQ that contains a modulator MOD and a voltage-controlled oscillator VCO. The voltage-controlled oscillator VCO generates a not necessarily linearly frequency-modulated signal S.sub.VCO wit
REFERENCES:
patent: 4054878 (1977-10-01), Diehl
patent: 4682175 (1987-07-01), Lazarus
patent: 4860017 (1989-08-01), Grudkowski
patent: 5164734 (1992-11-01), Fredericks et al.
"Taschenbuch der Hochfrequenztechnik", Grunlagen, Lomponenten Systeme, Lange et al., pp. S3-S4.
Bauelements Der Elektronik, "Signalvererbeitung mit akustischen Oberflachenwellen", pp. 263-267.
Siemens Aktiengesellschaft
Sotomayor John B.
LandOfFree
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