GB2265060A - Doppler velocity measurement - Google Patents
Doppler velocity measurement Download PDFInfo
- Publication number
- GB2265060A GB2265060A GB9204804A GB9204804A GB2265060A GB 2265060 A GB2265060 A GB 2265060A GB 9204804 A GB9204804 A GB 9204804A GB 9204804 A GB9204804 A GB 9204804A GB 2265060 A GB2265060 A GB 2265060A
- Authority
- GB
- United Kingdom
- Prior art keywords
- observer
- objects
- moving
- signal
- stationary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
- G01S13/522—Discriminating between fixed and moving objects or between objects moving at different speeds using transmissions of interrupted pulse modulated waves
- G01S13/524—Discriminating between fixed and moving objects or between objects moving at different speeds using transmissions of interrupted pulse modulated waves based upon the phase or frequency shift resulting from movement of objects, with reference to the transmitted signals, e.g. coherent MTi
- G01S13/526—Discriminating between fixed and moving objects or between objects moving at different speeds using transmissions of interrupted pulse modulated waves based upon the phase or frequency shift resulting from movement of objects, with reference to the transmitted signals, e.g. coherent MTi performing filtering on the whole spectrum without loss of range information, e.g. using delay line cancellers or comb filters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
Abstract
In a radar, lidar or sonar receiver there is a need to detect slowly moving objects moving towards the radar in order to ascertain whether these objects are a true target of a non-flying target. The radar received data 1 is fed to a set of Doppler filters 2. The output of each filter is coupled to a comparator 3 which is adapted to determine the identity of the filter producing the largest Doppler level or value. The comparator is further adapted to produce a signal having a logic high value only if the identified filter is the zero-Doppler filter; otherwise the comparator produces a logic low level. The output of the comparator is coupled to a moving window integrator 4 having the plurality of registers, and if a certain number of these registers contain a high value, an output signal is produced by a threshold detector 5 indicative of the identification of a stationary or slowly moving object. This may be used by inhibit circuit 6 to prevent display of these objects. The invention is stated to enable objects stationary with respect to the radar, moving slowly, or moving otherwise to be distinguished. <IMAGE>
Description
DOPPLER VELOCITY MEASUREMENT
The present invention relates to the measurement of the velocity of a body by means of the Doppler effect.
The Doppler effect is a well known phenomenon in which the frequency of a wave motion is increased or decreased according as to whether a source of the wave motion is moving towards or away from a receiver of the wave motion. The change in the nominal frequency of the wave motion is known as the Doppler frequency.
The Doppler effect can be used in pulse-echo ranging systems to provide a measure of any component of velocity towards or away from an observer a target body may possess. The technique is applicable to pulse-echo ranging systems using sound or electromagnetic radiation (sonar, radar or lidar, respectively) as is the present invention.
A problem which arises in Doppler velocity measurement systems in practice is distinguishing between target bodies which are stationary with respect to an observer, which are moving either slowly towards or away from the observer or with only a small component of velocity in those directions and other objects.
It is an object of the present invention to provide a method of and apparatus for discriminating between stationary objects, objects moving slowly towards or away from an observer or with only a small component of velocity in the said directions and other objects.
According to the invention in one aspect there is provided a method of discriminating between objects which are stationary with respect to an observer, are moving slowly towards or away from the observer or with small components of velocity in the said directions and other objects comprising the operations of analysing a signal received from an object into a plurality of bands of Doppler frequencies as hereinbefore defined, determining which band of
Doppler signals is predominant in the received signal and producing a discriminatory signal when the zero Doppler frequency band is predominant in the received signal.
According to the invention in another aspect there is provided an apparatus for discriminating between objects which are stationary with respect to an observer, are moving slowly towards or away from the observer or with small components of velocity in the said directions, and other objects comprising means for analysing a signal received from an object into a plurality of bands of Doppler frequencies as hereinbefore defined, determining which band of
Doppler frequencies is predominant in the received signal and producing a discriminatory signal when the zero Doppler frequency band is predominant in the received signal.
There may also be provided means responsive to the discriminatory signal to inhibit the display of a target trace when the object is stationary with respect to the observer or moving with only a very small component of velocity towards or away from the observer.
The means for analysing the received signal into a plurality of bands of Doppler frequencies may be a plurality of electronic filters each adapted to pass only a predetermined band of Doppler frequencies, and the means for determining which band of Doppler frequencies is predominant in the received signal may comprise a comparator adapted to determine which band of Doppler frequencies is predominant in the received signal. The means for producing a discriminatory signal when the zero Doppler frequency band is predominant in the received signal may comprise a circuit adapted to produce an output signal which has one value when the predominant
Doppler frequency band is the zero Doppler frequency band and another value when the predominant Doppler frequency band is other than the zero one. The said circuit may be included in the comparator.
The invention will now be described, by way of example only, with reference to the accompanying drawing which is a diagrammatic representation of a radar ranging system embodying the invention.
Referring to the drawing, radar signals 1 received from a target object, not shown are applied to a set 2 of Doppler filters, each of which is adapted to pass a predetermined band of Doppler frequencies only. The outputs from the set of Doppler filters are applied to a comparator 3, which is adapted to determine which band of Doppler frequencies predominate in the received radar signal 1. If the zero Doppler filter band is the predominant one, then the comparator 3 is adapted to produce an output signal which is applied to a moving window integrator 4 which contains five registers. The comparator 3 produces an output signal having a first value when the zero Doppler frequency band is the predominant one and a second value when another Doppler frequency band is the predominant one. If at least three of the registers contain signals from the comparator 3, then a threshold detector 5 is arranged to produce an output signal indicative that the object from which the radar signal 1 is received is either stationary or only has a very small component of velocity towards or away from the radar antenna (not shown) associated with the apparatus being described. The output signal from the threshold detector 5 is applied to a circuit 6 which is adapted to inhibit any signal corresponding to the stationary or slowmoving object being displayed on a visual display unit 7, thereby reducing the number of target traces shown on the visual display unit 7 and hence the risk of confusing relevant and irrelevant target
objects.
The invention has been described with reference to a radar
tracking system but it is equally applicable to sonar and lidar
systems.
Claims (12)
1. A method of discriminating between objects which are stationary with respect to an observer, are moving slowly towards or away from the observer or with small components of velocity in the said directions, and other objects comprising the operations of analysing a signal received from an object into a plurality of bands of
Doppler frequencies as hereinbefore defined, determining which band of Doppler signals is predominant in the received signal and producing a discriminatory signal when a zero Doppler frequency band is predominant in the received signal.
2. An apparatus for discriminating between objects which are stationary with respect to an observer, or which are moving slowly towards or away from the observer or with small components of velocity in the said directions, and other objects comprising means for analysing a signal received from an object into a plurality of bands of Doppler frequencies as hereinbefore defined, determining which band of Doppler frequencies is predominant in the received signal and producing a discriminatory signal when the zero Doppler frequency band is predominant in the received signal.
3. Apparatus according to Claim 2 including, means for displaying target traces corresponding to the objects from which the signals are received, wherein there is provided means responsive to the discriminatory signals to inhibit the display of target traces corresponding to objects which are stationary with respect to the observer, are moving only very slowly in directions towards or away from the observer or with very small components of velocity in the said directions.
4. Apparatus according to Claim 2 or Claim 3 wherein the means for analysing the received signal into a plurality of bands of Doppler frequencies comprises a plurality of electronic filters, each adapted to pass a predetermined band of Doppler frequencies only.
5. Apparatus according to any of Claims 2 to 4, wherein the means for determining which band of Doppler frequencies is predominant in the received signal comprises a comparator to which the analysed received signal is applied.
6. Apparatus according to Claim 5, wherein the comparator is adapted to produce a discriminatory signal when the zero Doppler frequency band is predominant in the received signal.
7. Apparatus according to Claim 6, including means responsive to the discriminatory signal to inhibit the display of a target trace when the object is stationary with respect to the observer, moving only slowly towards or away from the observer or with only a small component of velocity in the said directions.
8. Apparatus according to Claim 7, wherein the means for inhibiting the display of a target trace when the object is stationary with respect to the observer, moving only slowly towards or away from the observer or with only a small component of velocity in the said directions comprises a moving window integrator to which the signals from the comparator are applied and which includes a plurality of registers and means for producing an inhibiting signal when a predetermined number of discriminatory signals are present in a predetermined number of registers.
9. Apparatus according to Claim 8, wherein the moving window integrator includes five registers and the inhibiting signal is generated when discriminatory signals are present in at least three of the registers.
10. Apparatus according to any preceding claim, wherein the received signals are radar signals.
11. A method of discriminating between objects which are stationary with respect to an observer, are moving slowly towards or away from the observer or with small components of velocity in the said directions, substantially as hereinbefore described and with reference to the accompanying drawing.
12. An apparatus for discriminating between objects which are stationary with respect to an observer, are moving slowly towards or away from the observer or with small components of velocity in the said directions, substantially as hereinbefore described and with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9204804A GB2265060A (en) | 1992-03-04 | 1992-03-04 | Doppler velocity measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9204804A GB2265060A (en) | 1992-03-04 | 1992-03-04 | Doppler velocity measurement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9204804D0 GB9204804D0 (en) | 1992-09-23 |
| GB2265060A true GB2265060A (en) | 1993-09-15 |
Family
ID=10711566
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9204804A Withdrawn GB2265060A (en) | 1992-03-04 | 1992-03-04 | Doppler velocity measurement |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2265060A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0176652A2 (en) * | 1984-09-25 | 1986-04-09 | Siemens-Albis Aktiengesellschaft | Circuit for the suppression of multiple time-around echoes in pulse Doppler radars |
| GB2243510A (en) * | 1989-12-21 | 1991-10-30 | Siemens Plessey Electronic | Improvements in pulse doppler radar systems |
-
1992
- 1992-03-04 GB GB9204804A patent/GB2265060A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0176652A2 (en) * | 1984-09-25 | 1986-04-09 | Siemens-Albis Aktiengesellschaft | Circuit for the suppression of multiple time-around echoes in pulse Doppler radars |
| GB2243510A (en) * | 1989-12-21 | 1991-10-30 | Siemens Plessey Electronic | Improvements in pulse doppler radar systems |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9204804D0 (en) | 1992-09-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |