Communications – electrical: acoustic wave systems and devices – Echo systems – Speed determination
Reexamination Certificate
1998-11-25
2001-08-07
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Echo systems
Speed determination
Reexamination Certificate
active
06272071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a speed measuring apparatus for measuring the speed of a moving-target relative to the speed measuring apparatus, based on a frequency of a Doppler signal component selected from receiver signals corresponding to acoustic waves reflected from the moving-target.
2. Discussion of Background
Conventionally, a speed measuring method of this kind is theoretically known, which can be conducted by the steps of transmitting toward a moving-target an acoustic wave generated based on a reference signal with a predetermined frequency, receiving an acoustic wave reflected by the moving-target, of which frequency is changed from that of the transmitted acoustic wave by the Doppler effect, and determining the speed of the moving-target based on a change in the frequency of the transmitted acoustic wave.
However, in order to measure the speed of a moving-target which is small in size or is positioned far away from the observer, it will be necessary to implement countermeasures of increasing the transmission level of the acoustic wave which is generated based on the reference signal, and/or increasing the amplification degree of an acoustic wave receiving circuit.
However, when such countermeasures are implemented, there is the risk that normal signal processing cannot be performed. This is because it may occur that an acoustic wave with the same frequency as the frequency of the reference signal, which has a greater level than that of the acoustic wave reflected by the moving-target, travels from a wave transmitting unit and directly enters a wave receiving unit by diffraction, or the wave receiving unit receives reflection waves from fixed objects, which are positioned near the moving-target and are not subjected to the Doppler effect, whereby signal processing circuits such as amplifiers and/or mixers of the wave receiving circuits are saturated.
FIG. 12
is a block diagram of an example of a speed measuring apparatus that can be constructed based on the above-mentioned conventional speed measuring theory.
FIG. 13
is a diagram in explanation of the dynamic ranges, namely the permissible input ranges, of a pre-amplifier and a mixer for use in the example shown in FIG.
12
.
The example shown in
FIG. 12
is provided with an ultrasonic wave transmitting section
10
comprising a transmitting unit
11
, an ultrasonic wave receiving section
20
comprising a receiving unit
21
, and a signal processing section
30
.
The ultrasonic wave receiving section
20
further comprises a pre-amplifier
22
and a mixer
23
in addition to the receiving unit
21
.
As shown in
FIG. 13
, when a voltage amplification degree (gain) of the pre-amplifier
22
is 200 times, a noise level of the mixer
23
is 2 mV, and a saturation level of each of the pre-amplifier
22
and the mixer
23
is 1 V, the mixer
23
has a dynamic range (DRmix) of 2 mV to 1 V, and the pre-amplifier
22
, viewed from the side of the mixer
23
, has a relative dynamic range (DRamp) of 10 &mgr;V to 5 mV. Therefore, a lower limit of an input level of the pre-amplifier
22
, by which an ultrasonic wave reflected by a moving-target and subjected to Doppler shift can be processed, is 10 &mgr;V, while the permissible input level of the pre-amplifier
22
for the ultrasonic waves which travel from the transmitting unit
11
and directly enters the receiving unit
21
and for the ultrasonic waves reflected by fixed objects is less than 5 mV.
In this example, if a gain Gamp of the pre-amplifier
22
is increased, for example, to 400 times, the permissible input level of the pre-amplifier
22
is reduced to a half, that is, to less than 2.5 mV, so that it is necessary to implement some countermeasures, such as reducing the level of the ultrasonic wave emitted from the transmitting unit
11
to a half, or reducing the direct entering of the ultrasonic wave from the transmitting unit
11
to the receiving unit
21
. Therefore, it is considered that it is extremely difficult to measure the speed of the moving-target which is small in size or is positioned far away from the observer.
Furthermore, in the case where there are foreign objects near the moving-target of which speed is to be measured, and the foreign objects are moving at different speeds from that of the moving-target, it is extremely difficult to measure only the speed of the moving-target, since Doppler-shifted acoustic waves are reflected not only by the moving-target, but also by the foreign objects. For instance, when the speed of a ball thrown by a pitcher in baseball is to be measured, a Doppler-shifted acoustic wave is reflected by the ball itself and various Doppler-shifted acoustic waves are reflected by various parts of the body of the pitcher, and those Doppler-shifted acoustic waves are mixed and received, so that it is extremely difficult to measure only the speed of the ball.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a speed measuring apparatus which is capable of measuring the speed of a moving-target relative to the speed measuring apparatus, which moving-target is small in size and/or positioned far away from the measuring apparatus, even when an acoustic wave transmitted by acoustic wave transmitting means of the speed measuring apparatus directly enters acoustic wave receiving means by diffraction, or even when the acoustic wave receiving means receives acoustic waves reflected by fixed objects near the moving-target, which speed measuring apparatus is also capable of selectively measuring the speed of the moving-target even when near the moving-target there is a plurality of moving objects which move at different speeds from the speed of the moving-target and different acousticwaves reflected by the moving objects reach the speed measuring apparatus.
The above object of the present invention can be achieved by a speed measuring apparatus comprising:
transmitting means for transmitting an acoustic reference wave toward a moving-target, the acoustic reference wave being generated based on a reference signal with a predetermined frequency;
receiving means for receiving acoustic reflection waves which are generated by the transmitted acoustic reference wave being reflected by the moving-target, converting the acoustic reflection waves to receiver signals, and outputting the receiver signals therefrom;
signal attenuating means for selectively attenuating a signal component with the same frequency as the frequency of the reference signal in the receiver signals which are output from the receiving means and outputting signals therefrom;
band pass filter means for abstracting at least one Doppler signal component from the signals output from the signal attenuating means; and
speed computing means for computing the speed of the moving-target relative to the speed measuring apparatus, based on the Doppler signal component abstracted by the band pass filter means.
In the above-mentioned speed measuring apparatus, by use of the signal attenuating means, it is possible to selectively attenuate the signal component with the same frequency as the frequency of the reference signal, corresponding to the acoustic wave which directly enters the receiving means from the transmitting means by diffraction, and/or the acoustic waves reflected by the fixed objects near the moving-target. Therefore, the above-mentioned speed measuring apparatus is capable of increasing the acoustic pressure of the acoustic wave transmitted by the transmitting means and the signal amplification degree of the receiving means, and therefore is capable of measuring the speed of the moving-target which is small in size and/or positioned far away from the speed measuring apparatus.
Furthermore, in the above-mentioned speed measuring apparatus, by use of the band pass filter means, it is possible to selectively measure the speed of the moving-target even when near the moving-target there is a plurality of moving objects which move at different speeds from the speed of the moving-targ
Ikeuchi Fumio
Takai Takuo
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pihulic Daniel T.
Ricoh Microelectronics Co. Ltd.
LandOfFree
Speed measuring apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Speed measuring apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Speed measuring apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521458