Communications: directive radio wave systems and devices (e.g. – Determining velocity – Combined with determining sense of motion
Patent
1997-02-18
1998-10-20
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Determining velocity
Combined with determining sense of motion
342 28, 342194, G01S 1362
Patent
active
058253238
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar sensor with which, for example, the speed and/or the movement direction of an object can be determined.
2. Description of the Related Art
Radar sensors are widely used for contact-free measurement of object speeds and object separations. In this case, because of their robustness to environmental influences, radar sensors offer critical advantages in comparison with optical and acoustic sensors for operation in rugged operational conditions.
For cost reasons, radar sensors frequently contain homodyne receivers, that is to say the demodulation is carried out by mixing the frequency of the received signal directly with the transmitted signal. Since, in practice, the radar signal source is noisy containing (for example oscillator noise), the transmitted signal already contains noise. If a so-called single-diode mixer with only one diode which is (generally a Schottky diode) is used as the receiver, also called the demodulator, in simple radar sensors, then the noise in the transmitted signal causes an increase in the received noise level. FIG. 1 shows a block diagram of a radar sensor corresponding to the prior art, as is known from the publication by P. Heide, V. Magori, R. Schubert, R. Schwarte: "24 GHz Low-Cost Doppler Speedover-Over-Ground with Fundamental-Frequency PHEMT-DRO", IEEE GAAS' 94, Turin (Italy), April 1994. The radar signal source RS comprises a microwave oscillator MWO and generally also contains components for modulation M, so that the radar signal source RS generally produces a radar signal which is modulated as required. The choice of the modulation depends on the measurement task of the radar sensor. The signal which is produced by the radar signal source RS is emitted via the antenna A and is reflected back into the antenna A, as the received signal, from objects O which are located in the antenna lobe. The transmitted signal and received signal, described by complex field strengths E.sub.S and E.sub.R, are superimposed additively on the cable L between the radar signal source RS and the antenna A. The demodulator DM, which is connected to the cable L, produces homodyne demodulation and supplies the demodulated output signal u.sub.A (t), which is generally designated as the Doppler signal. The low-pass filter (TP) determines the measurement bandwidth of the output signal. The output signal u.sub.A (t) results approximately, as a consequence of the square component of the characteristic of the Schottky diode which is used in the demodulator (DM) and after low-pass filtering as: +E.sub.R.sup.2 + 2E.sub.S E.sub.R cos(.angle.E.sub.S E.sub.R).apprxeq.E.sub.S.sup.2 +2E.sub.S E.sub.R cos(.angle.E.sub.S E.sub.R) signal) signal)
Because of the noise from the radar signal source RS, the amplitude of the transmitted signal is not constant, and thus the term E.sub.S.sup.2 is also noisy. E.sub.S.sup.2 can thus be regarded as an interference signal which has a disadvantageous effect as a result of the reduction as in the signal to noise ratio of the output signal u.sub.A (t).
In more complex radar sensors, this disadvantage is circumvented by the use of so-called balanced mixers which are described, inter alia, in the book by Stephen A. Maas: "Microwave Mixers", Artech House, Dedham, Mass. (USA). However, the radar sensor in consequence becomes considerably more complex. In addition, the mixers themselves also produce noise contributions which are not suppressed by the use of balanced mixers.
SUMMARY OF THE INVENTION
An object of the invention is to provide an arrangement for a radar sensor, in the case of which quadrature demodulation is possible which until now has made the use of a second mixer necessary, according to the prior art technology! page 77 ff., Springer Press, 1989. Quadrature modulation makes it possible to determine the movement direction of moving objects.
This and other objects and advantages of the invention are achieved by a radar sensor, in which a means for producing a transmitted s
REFERENCES:
patent: 4331958 (1982-05-01), Lacomme
patent: 4439766 (1984-03-01), Kobayashi et al.
patent: 4860014 (1989-08-01), Shores et al.
patent: 4937580 (1990-06-01), Wills
patent: 5402129 (1995-03-01), Gellner et al.
patent: 5481270 (1996-01-01), Urkowitz et al.
patent: 5504455 (1996-04-01), Inkol
1984 IEEE, "A Simple Method for Sampling In-Phase and Quadrature Components", Correspondence, pp. 821-824.
S. Mass, Microwave Mixers, Artech House, Inc., 1993, pp. 237-312.
J. Detlefsen, Radartechnik, Springer-Verlag, pp. 77-81.
P. Heide et al., "24 Ghz Low-Cost Doppler Speed-over-Ground Sensor with Fundamental-Frequency PHEMT-DRO", IEEE GAAS '94 European GaAs Applications Symposium, Apr. 28-29, 1994 in Torino, Italy.
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Sotomayor John B.
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