GB2115252A - Pulse doppler radar units - Google Patents
Pulse doppler radar units Download PDFInfo
- Publication number
- GB2115252A GB2115252A GB08218490A GB8218490A GB2115252A GB 2115252 A GB2115252 A GB 2115252A GB 08218490 A GB08218490 A GB 08218490A GB 8218490 A GB8218490 A GB 8218490A GB 2115252 A GB2115252 A GB 2115252A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pulse
- repetition frequency
- pulse repetition
- range
- train
- 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.)
- Granted
Links
- 230000005540 biological transmission Effects 0.000 claims abstract description 5
- 238000002592 echocardiography Methods 0.000 claims description 8
- 230000006835 compression Effects 0.000 claims description 7
- 238000007906 compression Methods 0.000 claims description 7
- 238000004458 analytical method Methods 0.000 claims description 5
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 claims description 4
- 230000000737 periodic effect Effects 0.000 claims description 4
- 230000003321 amplification Effects 0.000 claims description 3
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 3
- 101100137546 Arabidopsis thaliana PRF2 gene Proteins 0.000 abstract description 11
- 101100191501 Zea mays PRO2 gene Proteins 0.000 abstract description 11
- 101000987581 Homo sapiens Perforin-1 Proteins 0.000 abstract description 9
- 102100028467 Perforin-1 Human genes 0.000 abstract description 9
- 230000001629 suppression Effects 0.000 abstract description 8
- 238000010586 diagram Methods 0.000 description 5
- 230000006735 deficit Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
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
- G01S13/528—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 with elimination of blind speeds
-
- 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
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
- G01S13/22—Systems for measuring distance only using transmission of interrupted, pulse modulated waves using irregular pulse repetition frequency
- G01S13/227—Systems for measuring distance only using transmission of interrupted, pulse modulated waves using irregular pulse repetition frequency with repetitive trains of uniform pulse sequences, each sequence having a different pulse repetition frequency
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
Pulse Doppler radar MTI units use different pulse repetition frequencies (PRF1, PRF2) and for the suppression of slow moving targets an overlapping of range is effected by periodically changing at 3 the PRF within each target -observation-time (TOT). In accordance with the PRF change the signal processing is divided into a near range B and a remote range A. During the transmission of radar signals of high PRF, at a high lower cut-off frequency of the moving target indicator (MTI) only the near range is analysed,whereas during the transmission of the low PRF only the remove range is analysed. <IMAGE>
Description
SPECIFICATION
Pulse doppler radar units
The invention relates to pulse doppler radar units comprising moving target indication and different pulse repetition frequencies.
In endeavours to minaturise the antennae of radar units, the frequency of the radar transmitter is set as high as possible, within the limitations imposed by the expected atmospheric conditions and bytechnology considerations. The need to operate at the highest possible transmitting frequencies is even greaterfor heightfinding radar units, having larger antennae used therein. This desire is restricted in situations in which radar units are to be used not only to cover relatively near ranges, but also to cater four average ranges, e.g. of100 km.In these cases the increase in range, combined with a reduction in the pulse repetition frequency (PRF) is disadvantageously opposed by an impairment of the suppression of
Doppler frequencies ofthe undesired signals of slowly moving targets due to a reduction in the lower limit speed. Whilstthe relative pole width of the moving target indicator remains identical, a reduction in the PRF in fact results in a reduction in the absolute lower cut-offfrequency, which governs the lower limit speed. On the other hand an increase in thelowercut-offfrequency,which results in a reduction in the path width ofthe filter for moving target indication by suppression of echoes from fixed or slowly moving sources must be contrasted with an impremissible impairment in the blind speed conditions.
These contradictory requirements regarding an increase in the range ofthe radar unit and an improvement in the suppression of signals from fixed or slowly moving targets cannot be satisfactorily fulfilled buy a compromise.
However, a pulse Doppler radar could utilise a high transmitting frequency and an appropriate high pulse repetition frequency to discolver close range targets, and a low transmitting frequency and an appropriately low pulse repetition frequency to discover more remote targets. Although the operation results achived by a radar unit of this this kind are good, the technical outlay is complex and expensive.
One object of the present invention is to provide a pulse Doppler radarwhich operates at a high transmitting frequency designed for average range, adapted with aviable outlayto achieve a good suppression oftargets which move at a low speed without increasing the occurrence of residual clutter and promoting the incidence of beyond horizon signals.
In accordance with the present invention there is provided a pulse Doppler radar unit for operation with mutually different pulse repetition frequencies, in which in the moving target indicatorfor the suppression of slow targets, range overlapping is effected by a periodic change ofthe pulse repetition frequency within each target-observation-time such that a plurality of common system components can be utilised in the transmitter and receiver sections of the radar unit, and signal processing is effected in accordance with the pulse repetition frequencies to cover a near range and a remote range, during the transmission of radar signals at a relatively high pulse repetition frequency only echoes from the near range are analysed using a relatively high lowercut-off frequency forthe moving target indicator filters, whereas during the transmission of radar signals with a low pulse repetition frequency only echoes from the remote range are analysed.
The division ofthe radar detection range into a near range and a remote range is based on an interlocking of pulse trains having mututally different pulse repetition frequencies, but using a common transitting frequency. The high PRF is advantageously approximatelydoublethelowPRF.The high PRFcan amount two a largerwhole numbered multiple ofthe low PRF. As a resultofthe use of a high PRF,which limitstherangeoftheradartoa nearrange,the low cut-offfrequency ofthe moving target indicator filter in the discovery range is sufficiently high to suppress echoes from slow moving targets.Here it may be assumed that slow movement on the ground at a range outside the near range will disappear behind shadows. Forthis reason itis unnecessaryto provide additional measures in the remote rangeforthe suppression of such movements. Asufficiently high cut-off frequency of the moving targer indicator filter is achieved bythe use of double cancellers.
Advantageously during target observation time (TOT) at ieast one group of non-expanded pulses of the high PRF are interlocked time-wise into expanded pulses of a pulse train having the low PRF. The width of the radar pulses ofthetrain having a high PRF without pulse compression and that of the radar pulses of the train having the lower PRF with pulse compression are maintained the same. Acorresponding pulse compression is required in the processing section ofthe associated radar receiverforthe low PRF pulses.
The time interlocking ofthe two pulse trains which possess mutually different pulse repetition frequencies can be achieved in various ways. For example, at least one pulse of the train having a low PRF can be replaced by a group of pulses of the train having a higher PRF, or all the interspaces btween the pulses of the train having a low PRFcan be filled bya group of pulses ofthe high PRFtrain, or else part ofthe interspacescan be filled in a periodic sequence by pulses ofthe high PRFtrain. Afurther possibility consists in coding one or both pulse sequences, possibly in different manners. The inconsistancies which are produced in the signal flow of the pulse sequence of the low PRF dueto the insertion of pulses ofthe high PRFtrain can be eliminated by known individual pulse suppression measures.
The invention will now be described with reference to the drawings, in which: Figure 1 is an explanatory diagram that schemati- cally illustrates the division of the overall range of a
radar device resulting from range interlocking;
Figure 2 is a basic block-schematic circuit diagram of one exemplary embodiment of a radar transmitter constructed to operate in accordance with the present invention;
Figure 3 is a basic block-schematic circuit diagram of one exemplary embodiment of a radar receiver; and
Figure 4 is a set of explanatory pulse diagrams illustrating one method of interlocking two pulse trains of mutually different pulse repetition frequency.
The overall range which can be detected by a radar device and represented on a display screen is indicated in Figure 1 by two concentric circles, a near range B having a maximum range R2, and a remote range A having a maximum range R1 Targets in i n the near range B are detected by echoes from a pulse train having a relatively high pulse repetitionfrequen- cy PRF1, and those in the remote range A are detected by echoes from a pulse train with a lower pulse repetition frequency PRF2. The ratio PRF2/PRF1 of the pulse repetition frequencies has a minimum value of approximately 1:2, and therefore considerably exceedsthe change of pulse repetition frequency that is normally used to suppress blind speed ranges.On account of the division intotwo range zones, a lower dynamic amplification reduction can be used in the range zone in comparison to a STC (sensitivity time control) for the overall range. The representation of targets which move from the remote range A into the close range B or vice versa is not subject to interference on the screen ofthe radar device.
In the radartransmittersection ofthe radar unit shown in Figure 2, a high frequency oscillator 4 generates a transmitting frequency which is fed via separate keying stages 5 and to respective inputs of an electronic switch 3 whose output drives a transmitter power output stage 2 connected to a radar antenna 1 The value ofthe transmitting frequency is independent ofthe keying. During each target coverage time, which is dependent upon the rotational speed ofthe antenna and upon the apertural angle of the antenna lobe, the keying of the transmitting frequencybythetwo keying stages5 and 6 is effected alternately, atthe pulse repetition frequencies PRF2 and PRF1 respectively. The electronic switch 3 selectively connects the transmitter output stage 2 to the corresponding keying stage 5 or 6.A keying frequency FT1 for the generation of a pulse train having the pulse repetition frequency PRF1 is generated in a generator 7 whose output is connected directly to the keying stage 6. A second keying frequency FT2 is obtained by feeding the output of the generator 7 via a divider stage 8, whose output is connected to the keying stage 5to modulate the transmitting frequency waveform and produce a pulse train having the lower pulse repetition frequency PRF2. The frequency FT2 is also fed to a control circuit composed of a frequency divider 9 and a keying circuit 10 to determine the keying ratio of the switching of the electronic circuit 3, and therefore the time and duration ofthe respective pulse trains fed to the antenna 1. The keying ratio of the switching function of the electronic switch 3 can be adjusted in the stage 10.
Making reference to the set of pulse diagrams
illustrated in Figure 4, the interlocking of the pulse trains bythe action ofthe electronic circuit 3 is
represented in a simplified form. Waveform a of
Figure 4 represents a pulse train of the relatively low pulse repetition frequency PRF2, which is used for the remote range A, and waveform b represents the pulse train of the higher pulse repetition frequency PRF1 which is used forthe near range B ofthe radar unit.In the case of an operation mode of a radar unit in which, during a target-observation-timeTOT, one pulse of the pulse train having the repetition frequency PRF2 is replaced by a sequence of pulses of the pulse repetition frequency PRF1 ,the one pulse of the pulse train of repetition frequency PRF2 being blanked out by a release pulse ofthewaveform czars indicated by waveform a with the pulse train of repetition frequency PRF2 interrupted one in each period TOT. At the same time a sequence of pulses ofthe higher pulse repetition frequency PRF1, as illustrated in waveform b, is released by a second release pulse, illustrated in waveformc,forthe duration of one period of the pulse repetition frequency PRF2. During this time the electronic switch 3 occupies the postion 3b (Figure 2).
The interlocked pulse sequence emitted from the antenna 1 is represented in the final waveform a + b of Figure 4.
In synthronism with the electronic switch 3 in
Figure 2, a corresponding switch 13 in the associated radar receiver must be operated. In the radar receiver shown in Figure 3,the antenna 1 is that shown in
Figure 2, as it is a common element used for transmitting and receiving. Following amplification, conversion and rectification in a receiving stage 12, the echo signals received via the antenna 1 are forwarded as video signals to a signal analysis circuit to be represented on a PPI display device 14.The signal analsis device for moving target indication (MTI) is divided into afirstbranch 16forthe processing of echo signals of pulses from the train of frequency PRF1 covering the near range B and a second branch 15for processing signals from the remote range Athat are produced by pulses from the train having the repetition frequency PRF2. The electronic switch 13 switches the video signals from the output ofthe receiving stage 12 alternately to the first branch 15, comprising an anlysis circuit for
pulses ofthe low pulse repetition frequency PRF 2
and a following detector stage, and then to the second branch 1 6 for analysis of the echo signals from the remote range A. The output of the analysis
branches 15 and 16 are connected via an OR gate 17 to a display device 14On which the target echo signals
are represented.
In the described design, thetransmitter and receiv
ersections can employ a substantial number of
common components in a radar unit. Separate signal
processing forthetwo range zones is required only in
the two analysis branches 15 and 16 of the radar
receiver section, whereas the antenna, transmitter,
and receiver require no separation, although indi
vidual additional elements mat be incorporated, such
as pulse compression or optimal filters and target
representation means.
Claims (12)
1. A pulse Doppler radar unit for operation with mutually different pulse repetition frequencies, in which in the moving target indicatorforthe supression of slowtargets, range overlapping is effected by a periodic change of the pulse repetition frequency within each target-observation-time such that a plurality of common system components can be utilised in the transmitter and receiver sections ofthe radar unit, and signal processing is effected in accordancewith the pulse repetitionfrequenciesto cover a near range and a remote range, during the fransmission of radar signals at a relatively high pulse repetition frequency only echoes from the near range are analysed using a relatively high lower cut-off frequencyforthe moving target indicator filters, whereas during the transmission of radar signals with a low pulse repetition frequency only echoes from the remote range are analysed.
2. A pulse Doppler radar unit as claimed in Claim 1, in which the higher pulse repetition frequency is a whole numbered multiple of the lower pulse repetition frequency.
3. Apulse Doppler radarunitas claimed in Claim 1, in which the analysis of the radar signals ofthe low pulse repetition frequency train is carried out using pulse compression.
4. A pulse Doppler radar unit as claimed in Claim 1, in which the pulse width ofthe radar pulse train having the high pulse repetition frequency without pulse compression is equal to that of the pulse of the train having the lower pulse repetition frequency with pulse compression.
5. A pulse Doppler radar unit as claimed in any preceding claim, in which thetwo pulse repetition frequencies are transmitted on the same transmitting carrierfrequency.
6. A pulse Doppler radar unit as claimed in any preceding Claim, in which during each targetobservation-time at least one group of pulses of the high pulse repetition frequency overlaps time-wise into the pulse train ofthe lower pulse repetition frequency.
7. A pulse Doppler radar unit as claimed in any preceding Claim, in which at least one pulse of the train having a low pulse repetition frequency is replaced by a group of pulses ofthe higher pulse repetition frequency.
8. A pulse Doppler radar unit as claimed in any preceding Claim, in which one or both pulse sequences are differently coded.
9. A pulse Doppler radar unit as claimed in Claim 8 when dependant upon any one of Claims 1 to 6, in which a group of pulses of the high pulse repetition frequency train is inserted between all the pulses of the low pulse repetition frequency train.
10. Apulse Dopplerradar unit as claimed in Claim 9, inwhich pulses with the high pulse repetition frequencyareinserted in a periodic sequence into part of the interspaces between the pulses of the low pulse repetition frequency train.
11. Apulse Dopplerradarunitas claimed in any preceding Claim, in which an amplification reduction of lower dynamics is used in a range zone in comparison to a sensitivitytimecontrolforthe overall range.
12. A pulse Doppler radar unit substantially as described with reference to Figures 2 and 3.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3132268A DE3132268C1 (en) | 1981-08-14 | 1981-08-14 | Pulse Doppler radar device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2115252A true GB2115252A (en) | 1983-09-01 |
| GB2115252B GB2115252B (en) | 1985-05-01 |
Family
ID=6139374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08218490A Expired GB2115252B (en) | 1981-08-14 | 1982-06-26 | Pulse doppler radar units |
Country Status (5)
| Country | Link |
|---|---|
| DE (1) | DE3132268C1 (en) |
| FR (1) | FR2522414B1 (en) |
| GB (1) | GB2115252B (en) |
| IT (1) | IT1151229B (en) |
| NL (1) | NL8203185A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3326115A1 (en) * | 1983-07-20 | 1985-01-31 | Siemens AG, 1000 Berlin und 8000 München | Pulse Doppler radar |
| DE3326116A1 (en) * | 1983-07-20 | 1985-01-31 | Siemens AG, 1000 Berlin und 8000 München | Pulse Doppler radar |
| GB2214026A (en) * | 1987-12-23 | 1989-08-23 | Hollandse Signaalapparaten Bv | Radar apparatus employing different kinds of pulses |
| EP0320306A3 (en) * | 1987-12-11 | 1991-01-30 | Nec Corporation | Phased-array radar |
| GB2463391A (en) * | 2007-08-31 | 2010-03-17 | Raymarine Uk Ltd | Digital radar or sonar processing |
| CN112731329A (en) * | 2020-12-29 | 2021-04-30 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Method and system for improving isolation degree of long-distance echo and short-distance clutter of harmonic radar |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6049302A (en) * | 1999-05-04 | 2000-04-11 | Boeing North American | Pulsed doppler radar system with small intermediate frequency filters |
| FR2848675B1 (en) * | 2002-12-17 | 2005-05-06 | Thales Sa | METHOD OF MEASURING DOPPLER FREQUENCY BY TRANSMITTING LACUNAR PULSE TRAINS |
| DE102004050627B4 (en) * | 2004-10-18 | 2013-08-08 | Audi Ag | Method and distance measuring device for determining the distance between an object and the device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3765017A (en) * | 1968-06-12 | 1973-10-09 | North American Rockwell | Amti range ambiguity resolver |
| NL183210C (en) * | 1976-11-12 | 1988-08-16 | Hollandse Signaalapparaten Bv | TWO KINDS OF PULSE WORK RADAR SYSTEM. |
| US4143373A (en) * | 1977-09-21 | 1979-03-06 | Hughes Aircraft Company | Adaptive radar systems and methods therefor |
-
1981
- 1981-08-14 DE DE3132268A patent/DE3132268C1/en not_active Expired
-
1982
- 1982-05-25 IT IT21459/82A patent/IT1151229B/en active
- 1982-06-26 GB GB08218490A patent/GB2115252B/en not_active Expired
- 1982-08-10 FR FR8213908A patent/FR2522414B1/en not_active Expired
- 1982-08-13 NL NL8203185A patent/NL8203185A/en not_active Application Discontinuation
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3326115A1 (en) * | 1983-07-20 | 1985-01-31 | Siemens AG, 1000 Berlin und 8000 München | Pulse Doppler radar |
| DE3326116A1 (en) * | 1983-07-20 | 1985-01-31 | Siemens AG, 1000 Berlin und 8000 München | Pulse Doppler radar |
| EP0320306A3 (en) * | 1987-12-11 | 1991-01-30 | Nec Corporation | Phased-array radar |
| GB2214026A (en) * | 1987-12-23 | 1989-08-23 | Hollandse Signaalapparaten Bv | Radar apparatus employing different kinds of pulses |
| GB2214026B (en) * | 1987-12-23 | 1992-04-22 | Hollandse Signaalapparaten Bv | Radar apparatus employing different kinds of pulses |
| GB2463391A (en) * | 2007-08-31 | 2010-03-17 | Raymarine Uk Ltd | Digital radar or sonar processing |
| US8624776B2 (en) | 2007-08-31 | 2014-01-07 | Raymarine Uk Limited | Digital radar or sonar apparatus |
| US9024816B2 (en) | 2007-08-31 | 2015-05-05 | Raymarine Uk Limited | Digital radar or sonar apparatus |
| US9372257B2 (en) | 2007-08-31 | 2016-06-21 | Raymarine Uk Limited | Method of operating a digital radar or sonar apparatus |
| US9645229B2 (en) | 2007-08-31 | 2017-05-09 | FLIR Belgium BVBA | Digital ranging systems and methods |
| CN112731329A (en) * | 2020-12-29 | 2021-04-30 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Method and system for improving isolation degree of long-distance echo and short-distance clutter of harmonic radar |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3132268C1 (en) | 1985-12-05 |
| FR2522414A1 (en) | 1983-09-02 |
| IT1151229B (en) | 1986-12-17 |
| IT8221459A0 (en) | 1982-05-25 |
| FR2522414B1 (en) | 1986-03-07 |
| GB2115252B (en) | 1985-05-01 |
| NL8203185A (en) | 1983-07-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |