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BACKGROUND OF THE INVENTION
The present invention relates to a device for converting output data of a
radar for the display thereof on at least one television screen.
More particularly, this device is employed for displaying the data on a
television screen associated with at least one videographic memory.
More generally, the converting device proposed permits displaying on a
standard television screen having an X, Y scanning, i.e. in Cartesian
coordinates, images issuing from a sensor operating in i.e. in polar
coordinates. This sensor is usually a radar antenna associated with its
control electronics and, in the art, the consoles employed for the display
of these radar images directly receive the different data, and in
particular the videographic output signal of this radar. However, these
consoles are relatively rudimentary and the quality of the image displayed
is not very good.
Further, the possibilities of extension of the utilization, in particular
of the radar imagery, are also relatively limited due to the structure of
these consoles, and in particular the display screen and its control
electronics.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to overcome these problems
by permitting the display of these images on a television screen, while
respecting the ergonomics of the conventional consoles and conserving the
quality of the imagery related to the remanence of the phosphors employed
in these conventional consoles.
The invention therefore provides a device for converting output data of a
radar for the display on at least one television screen associated with a
videographic memory, the output signals of the radar comprising at least
one videographic signal and scanning data, the device comprises a
processor for processing the different radar output data, an
analog/digital converter for digitizing the videographic signal, a
videographic signal converter for compressing the digitized videographic
signal, a distance marker generator for generating distance markers, a
polar to Cartesian converter for converting the standard of the
coordinates of the data contained in the videographic signal from a polar
coordinate system into a Cartesian coordinate system, an intermediate
memory for receiving and storing the compressed videographic signal and
the distance markers, and output buffer memory for receiving and storing
the output signals of the intermediate memory and the polar to Cartesian
converter, an interface for controlling the videographic memory as a
function of the data contained in the buffer memory and an after glow
processor connected to the interface for controlling the contents of zones
of videographic memory.
A better understanding of the invention will be had from the following
description, which is given solely by way of example, with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the operation of a converting device
according to the invention;
FIG. 2 is a table of VME addresses employed by the converting device
according to the invention;
FIG. 3 is a block diagram illustrating the operating of an after glow
processor which is part of the structure of a control unit according to
the invention, and
FIG. 4 shows a screen of a monitor on which two radar images are displayed
simultaneously.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The data converting device according to the invention is intended to be
used for converting output data of a radar and permitting the display
thereof on at least one television screen associated with a videographic
memory.
As can be seen in FIG. 1, the different output data of the radar further
comprising at least one videographic signal and scanning data, are applied
to the input of processing unit 1. The device of which forms what is
called a radar interface comprising different analog and digital circuits
effecting a pre-processing of the radar signals so that they may be
employed by the rest of the circuits of this device. Generally, these
signals comprise at least:
two videographic inputs (primary and secondary), a, b;
an IFF input, c;
a synchro input d; and
a series azimuth input f.
The primary and secondary videographic signals pass through an
amplification circuit which is within processing unit 1 in order to have a
correct amplitude at the input of analog/digital converter 2 which will be
described in more detail hereinafter.
The gain of the videographic signals is controlled digitally by an
analog/digital multiplier 1a which conserves the pass band and whose gain
value is determined by a register.
The videographic signals a and b are multiplexed and the choice of the
videographic signal to be processed is made under the control of a control
unit, per FIG. 3, which will be described in more detail hereinafter.
The IFF signal, after amplification is adjustable by IFF signal amplifier
1b, and is mixed with the videographic signal selected before digitization
and its presentation is subjected to the choice of the operator by a
selection by means of the control unit per FIG. 3. Furthermore, a zooming
device 1d, provides conventional functions of enlargement of certain parts
of the radar image.
Lastly, the azimuth signal and its associated clock e are put into form in
differential receivers such as commercially available differential
amplifiers, before being sent to a shift register, generally designated by
1c.
An azimuth signal f, is at the output of the latter in parallel form and
this signal is used, as will be described in more detail hereinafter, in
polar to Cartesian converter 5 for converting the standard of the
coordinates of the data contained in the videographic signal.
After passage through the previously-described processing unit 1, the
videographic signal is applied to the input of the analog/digital
converter 2 for digitizing. At this point, the sampling is effected at a
fixed frequency so that it is possible to process pulses corresponding to
the minimum pulse width of the radar, the signals of which are to be
displayed. As an example, a 10 MHz clock is used and allows the
digitization of pulses which width is 200 ns.
The analog/digital converter 2 is associated with video signal converter 3
for compressing the videographic signal so as to digitize solely that
which is displayable on the screen and thereby reduce the amount of data
to be processed.
Thus, when the number of samples along an image radius is higher than the
possible definition of the display, the radar data is grouped, i.e. the
maximum amplitude level of the videographic signal is taken from among N
samples.
As an example, for a given scale and a frequency of 10 MHz, there are 2,048
samples along each radar radius. There is then effected a grouping of the
order 2 and only the maximum amplitude among two successive samples is
taken.
For this purpose, it is necessary to construct a clock whose frequency
varies as a function of the chosen type of radar and scale. This clock is
modified by the clock management unit 13. The maximum amplitude of the N
samples is detected in real time at the output of the analog/digital
converter 2 by the videographic signal converter 3.
Further, the variable clock management unit 13 is also employed by distance
marker generator 4.
A perfect concordance results between these markers and the digitized
videographic signal. The digitized videographic signal and the markers are
then employed for addressing a rapid static intermediate memory 6 which
will be described in more detail hereinafter, and which permits, in
accordance with its contents, checking a certain number of elements of the
display and for example, the luminosity of certain markers, the adjustment
of the zero level of the videographic signal so as to allow suppression of
noise, etc.
Note that a table of the correction of the amplitudes of the radar
videographic signal could also be written so as to modify the transfer
function of the digitization line (logarithmic response, etc .... ).
The converting device further comprises polar to Cartesian converter 5 for
converting the standard of the coordinates of the data contained in the
videographic signal from a polar coordinate system into a Cartesian
coordinate system.
This permits effecting the sample writings directly in the physical space
of the videographic memory.
These different converting operations are carried out in real time and are
timed by a variable clock management unit 13, only the coordinates of the
previously selected points being calculated.
At the output, these different coordinates are modified in accordance with
the position of the radar with respect to a display unit, etc . . . . so
as to obtain coordinates pertaining to the physical space of the
videographic memory.
The intermediate memory 6 receives the output signals of the distance
marker generator 4 and the videographic signal converter 3 for
compression.
The converting device as per the assembly shown in FIG. 1, also comprises
an output buffer memory 8, receiving the output signals of the
intermediate memory 6 and the polar to Cartesian converter 5 through the
eccentricity management unit 7. Furthermore, memory 8 permits interchange
between the converting device shown in FIG. 1 and the control unit shown
in FIG. 3.
This output buffer memory 8 may be formed by memories of the first in,
first out (FIFO) type permitting asynchronous accesses at variable
frequency between the polar to Cartesian converter 5 and the control unit.
The abscissa and the ordinate of the points of a radar radius and the
amplitude of the associated videographic signal are available at the input
of output buffer memory 8.
This group of data forms a word of 32 bits which is read by the control
unit formed by for example, any suitable device, such as an automatic
writing means in the videographic memory, depending on the chosen option.
In order to limit the number of transfers to be effected, only the
amplitude points different from 0 are writing in the output buffer memory
8 and it will be noted that the number of written points largely depends
on the adjustment of the threshold suppressing the background noise of the
videographic signal.
It will be observed that this converting device may be used in a standard
work station in which the displays may employ the well-known computer
standards of the types, VME, UNIX, X-WINDOWS, GKS, etc. . . . .
In this case, the output of the output buffer memory 8 is for example,
connected to an interface of type VME 9, which permits transmission of the
different control orders to the different circuits of the converting
device and control the display of the images by controlling the
videographic memory.
There is then no processing during the conversion by the host calculator,
which permits working in virtually real time.
Various input-output addresses have been reserved in the extended
addressable space, for example of a Unigraph as can be seen in particular
in FIG. 2.
NORVAM address
A non-volatile memory of 2K of 8 bits enabling the converting device to
save the current display parameters. When turning it on, it is initialized
by means of the parameters is had stored before it was cut off. This
memory is accessible by the host calculator in reading and writing.
FIFO address
Causes the word by word reading of the information addresses/data
calculated by the converting device.
Intermediate memory address
Permits modifying the contents of this memory (luminosity markers, SEP,
course flash . . . ).
Video gain address
Permits adjusting the luminosity of the real video; 256 values are
possible.
IFF gain address
The same function as the video gain.
State 1 (status 1) register address
Being accessible in writing, this register permits modifying the displayed
videos.
In reading, this register constitutes the state of the FIFO.
Eccentricity address
Register containing the system coordinates of the radar center.
Zoom address
Register containing the value of the scale selected for the display.
SEP address
Register containing the radius of the zone of suppression of the near
module echo of 8 screen pixels; 64
State 2 (status 2) register address writing
Servitude register permitting among other things the activation of the
resetting of the pointers of the FIFO.
There may also be effected a mixture of real-synthetic data in the region
of a VMCG2a graphic card, by means of the data calculated by the polar to
Cartesian converter 5 and temporarily stored in the output buffer memory
8.
As can be seen in FIG. 3, a direct display may also be provided.
Indeed, as the principle of the writing of the radar data in the graphic
card of the Unigraph via the VME bus imposes limitations on the definition
and the scanning rate of the radar, a direct display option may also be
employed.
It permits among other things the display of the radar data by using 6
bits, namely 64 levels, which enables appreciating the difference when
rendering and presenting the image. An after glow processor 10 (shown in
FIG. 3) is connected to a radar videographic memory 11 so as to allow a
display close to that obtained on a conventional directed beam screen.
A memory addressing management unit 20, has as its function, control of the
addressing of memory 11 in a conventional manner and also generating the
sequential addresses.
As can also be seen in FIG. 3, the sequential addresses, i.e. display
addresses of the TV lines, are generated from the videographic output
sequence. As the latter depends on the definition, the use of programmable
circuits is consequently necessary.
The base frequency of the clock point is for example, 120 MHz for a
1280.times.1024 pixels format.
The following table gives the different times of the videographic sequence.
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Signal 1280 .times. 1024
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Vertical frequency 60 Hz
Raster blanking duration
656,8 .mu.s
Line duration 15,64 .mu.s
Line blanking duration 4,97 .mu.s
Useful line duration 10,67 .mu.s
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The video sequence generator 18, which generates the video sequence for the
display addresses in combination with the clock pixel generator 19,
synchronize the writing of the radar data with the videographic sequence
by generating the signals required for reading back of the output buffer
memory 8.
A memory sequencer 16 generates all the signals required for the control of
the radar videographic memory 11 and the division of the memory bus for
the three types of access to this memory.
These three accesses are:
sequential access, i.e. the loading in the output offset registers, of the
contents of the videographic lines so as to transmit them to the output
digital/analog converter.
radar access, i.e. the generation of the reading signal of the buffer
memory 8 and the management of the conditional writing in the radar
videographic memory 11. Indeed, the radar data must not be systematically
rewritten, since the data of a radar spot could be crushed by the noise.
In the course of this access, the data is therefore only written if the
latter is superior to that present in the considered address.
After glow processor 10 access, i.e. the generation of the control signals
required for the after glow processor 10.
The radar videographic memory 11 permits the random storage of the radar
data which will be read back sequentially for display.
The components employed for constructing this memory may be constituted by
videographic RAM memories having a 256 K capacity of 4 bits comprising an
output shift register, which permits loading in the register the data of a
videographic line in one RAM cycle. The rest of the time, the memory is
available for the writing of the radar videographic signal by the after
glow processor 10.
In order to avoid the use of an excessively fast shift clock, the memory is
divided in the parallel form into eight pages timed by a clock of 120 MHz
divided by 8, i.e. 15 MHz.
Eight pixels every 67 ns are then delivered at the output of this memory,
these points being put in series by the videographic output stage.
The resetting of the radar videographic memory 11 is necessary for the
presentation upon each rotation of the real situation. This, added to the
ergonomic utility of the after glow of the phosphors used in the
conventional directed beam scanning, led to the realization of a pseudo
after glow of the data display.
The observation of the visual phenomena due to the asynchronism of the two
types of scanning, namely radar and television, and the physiology of the
human eye, permitted the realization of a simple and high-performance
algorithm, such as known, for example, from U.S. Pat. No. 4,829,308,
enabling an excellent rendering of the after glow effect to be obtained.
Of course, the fact that this effect is obtained numerically in the radar
videographic memory authorizes the use of laws, a mathematical treatment
formula such as is known, for example, from U.S. Pat. No. 4,580,164, of
any decrease in the luminosity both as concerns space and time, up to an
infinite after glow which is very useful for effecting the trace of the
history of the trajectories of mobile echos.
The best rendering of the after glow effect is obtained with bits of data
to be displayed.
This after glow processor 10 then processes the content of certain zones of
the radar videographic memory in accordance with a given law, a
mathematical treatment formula, so as to produce a pseudo-after glow
phenomenon of certain points of the radar image displayed on the screen.
The analog output stage, 12 in FIG. 3, is adapted to convert into analog,
the contents of the radar videographic memory and produce videographic R,
G, B and TV synchro signals for controlling the monitor.
This stage further permits defining the desired palette of pseudo-colours.
A value chose among 16.8 million possibilities corresponds to a given
videographic level.
Therefore, there are available at the output, 64 colours with 6 radar bits
(16 colours with 4 radar bits) among the possible 16.8 million. This
palette of pseudo-colours is loaded via the VME bus.
The analog output 12 also controls three different cursors 17, two of which
are completely definable in a 64.times.64 matrix, the last being a cross.
The colour of these cursors is also programmable.
As the radar videographic memory 11 is divided into 8 parallel pages, the
analog feature of the output stage 12 places in series format, the 8
points for displaying a videographic point in pseudo-colours every 8.3 ns
in the 1280.times.1024 format.
The output videographic signal is available in analog form with as
amplitude 0.7 V for the R and B outputs and 0.7 plus 0.3 V of
synchronization on the G output, permitting synchronization of the
monitor.
All programs of the analog output stage 12, bearing in mind the memories of
the colours, the forms and the positions of the cursors, are effected via
the VME bus.
The radar data converting device is in fact constructed in the form of a
module of two cards in the long double Europe format which is integrated
into the card rack of a Unigraph. This device respects the VME interface.
The basic converting device requires only a single card for the realization
of the initial configuration, this card receives its controls via the VME
bus and delivers the data in Cartesian coordinates after calculation.
This card uses components of the VLSI type in CMOS technology, most of the
latter being reconfigurable by an exterior PROM, permitting, for example,
the easy modification of the display standard. It may be achieved with
cabled technology.
All of the direct display is in the form of a daughter card which may be
connected to the basic converting device.
It groups all the memories, the sequencer, the after glow processor, the
pixel clock, etc.
Owing to the high operating frequencies, it is formed on a printed circuit
card having for example, six layers.
It will therefore be understood that the converting device according to the
invention, permits the display of a complete radar image on a monitor
employing an X, Y scanning, for example, having a high definition.
The invention also permits the simultaneous display of a plurality of
complete or partial radar images on the same monitor, the radars being
located at a distance from one another.
FIG. 4 gives an example of the simultaneous display of two radar images
which permits for example, following without discontinuity, the trajectory
of an aircraft or a missile which flies in succession in the fields of the
two radars.
It is possible to envisage the simultaneous display of four radar images
with the aid of a single videographic memory.
All the functions of a conventional console may be performed. This permits
an easy ergonomic study of new functions which are possible with the use
of a graphic station and a radar videographic memory, in particular, as
concerns the after glow laws and the use of colours.
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