Arrangement for position-selective speed measurement using the d

Details Arrangement for position-selective speed measurement using the d Arrangement for position-selective speed measurement using the d

1996-12-10

1998-07-21

Blum, Theodore M.

Communications: directive radio wave systems and devices (e.g.,

Determining velocity

342109, 342375, G01S 1308

Patent

active

057840245

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to an arrangement for position-selective speed measurement using the Doppler principle.
2. Description of the Related Art
Cost-effective microwave Doppler sensors are used to measure the speed over ground of land vehicles and vehicles on rails, and for movement detection in alarm systems. The sensitivity of these sensors is essentially limited by the noise behavior of the microwave generator.
In the case of Doppler sensors which operate using the continuous-wave (CW) mode, position-selective Doppler evaluation is also not possible.
In the Pulse-Doppler method, short microwave pulses are emitted which recur at a pulse repetition frequency PRF. The range selection in Pulse-Doppler sensors is governed by the time interval between the signals received from reflection objects at different ranges.
In the case of the Pulse-Doppler short-range sensor, fine position resolution is desirable, and a short pulse duration and thus a high transmission bandwidth are required for this purpose. The mean transmitted power and thus the sensitivity of the receiving stage as well are, however, reduced at the same time. This can be counter-acted by a greater transmitted pulse power or a higher pulse repetition frequency PRF, although this limits the maximum unambiguous range area, or by pulse integration, although this limits the maximum speed which can be measured unambiguously. Switching feedback effects in the pulse mode make it necessary to install expensive, direction-selective components such as isolators or separate transmitting and receiving antennas, for example, in the known pulsed sensors.
FIG. 1 shows the block diagram of a Pulse-Doppler sensor as is known from pocketbook!, Chapter S1, Springer Press, 5th Edition, 1992. The microwave signal produced by the radio-frequency generator HFG--a microwave oscillator--is switched over with the aid of a microwave switch S having an amplitude-contrast ratio k: ##EQU1## where: A.sub.1 =amplitude during the switching state .alpha. on off transmitting/receiving antenna A. The transmitted field strength E.sub.S and the received field strength E.sub.R are super-imposed between the radio-frequency generator HFG and the reflection object to form a standing wave. One cost-effective option for obtaining Doppler signals is homodyne detection by using a Schottky diode to detect the standing wave. The voltage u.sub.Det (t) at the demodulator DM, also called the detector, turns out, because of the square-law diode characteristic in the CW mode, to be: =E.sub.R.sup.2 +2E.sub.S E.sub.R cos(.phi.(t)).apprxeq.E.sub.S.sup.2 +2E.sub.S E.sub.R cos(.phi.(t)) received field strength E.sub.R.
Because of the noise from the radio-frequency generator HFG, the term E.sub.S.sup.2 which corresponds to the rectified element of the oscillator signal is not constant. The reception sensitivity is determined by the ratio of the fluctuation width of the term E.sub.S.sup.2 to the amplitude of the Doppler signal. In contrast to the CW mode, a Doppler signal is present at the demodulator DM in the pulse mode (in the ideal case the amplitude-contrast ratio k is much greater than 1) only in the switching state .alpha., .alpha. designating the pass mode, and can be sampled at the demodulator DM, the measurement of the Doppler signal being repeated at a repetition frequency PRF by repeatedly switching over between the states .alpha. and .beta.. A position-selective, continuous-time Doppler signal can be reconstructed from the sample pulses by interpolation of all the samples from the Doppler signal, for example with the aid of a sample and hold element AH. One disadvantage of this method is that the samples are adversely affected by switching spikes and oscillator noise and, because of the finite amplitude-contrast ratio k<.infin., also contain a signal element from undesired range areas. In the past, these disadvantages have been only partially overcome using microwave switches with high switching contrast, direction-sel

REFERENCES:
patent: 2676317 (1954-04-01), Purington
patent: 3764963 (1973-10-01), Beck et al.
patent: 5150126 (1992-09-01), Knepper et al.
Lange et al., Hochfrequenztechnische Anlagen, RF and microwave applications .

Affiliated with

Also associated with

Rating

Arrangement for position-selective speed measurement using the 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 Arrangement for position-selective speed measurement using the d, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arrangement for position-selective speed measurement using the d will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1650474