NO169982B - HOW FREQUENCY, VESSEL COUPLED MEAL DETECTION SEARCH SYSTEM - Google Patents

Description

The present invention relates to a high frequency, vessel-connected raw target detection search system, as stated in the introductory part of the attached patent claim 1.

Various prior art passive and radiometric millimeter-wavelength ground target detection and search systems have demonstrated passive target acquisition with high accuracy. However, these passive guidance systems tend to have a relatively short range, especially at the higher microwave frequencies, which is further exacerbated by adverse atmospheric conditions. Consequently, recent ground target seekers have been increasingly based on the use of both active radar and passive radiometric modes to achieve favorable combinations of achieved target range and seeker accuracy. Operation in the active mode will, in the desired way, provide the necessary characteristics for target attainment and search range, while passive operation at a relatively short range increases the final search accuracy, eliminates the effects of target glitter and sparkle at relatively short ranges or distances.

Operation of active search systems in the 30-300 GHz frequency range results in a more desirable combination in terms of antenna aperture size and weather permeability compared to operation in higher or lower areas of the spectrum. In addition, a significantly greater radio frequency bandwidth is available in terms of clutter smoothing and precipitation-backscatter decorrelation compared to the lower radar carrier frequencies. Typical selected millimeter wave operating frequencies are 35 GHz and 95 GHz, where there are partial atmospheric windows, i.e. where the attenuation is much lower than in other parts of the millimeter wave spectrum. Because the primary use of the seeker is to detect and track ground targets, the antenna will receive a significant amount of energy from the terrain in addition to what it receives from the target. In the active case, this involves the reflected illuminating energy. In the passive case, it is primarily terrain-emitted energy. During passive operation, the more reflective and therefore less radiating, metallic targets will tend to reflect the cool external room temperatures, and thus appear cool in contrast to the warmer background. In the active mode, metallic targets will appear as a stronger source of reflected energy compared to the terrain area of equal physical size. In both cases, the seeker will logically be regarded as a contrast seeker. It is highly desirable to keep the antenna beam interception on the terrain as small as possible. Because the seeker is normally used in airframes with a relatively small diameter or in vehicles, it is possible to use carrier frequencies that are as high as possible, but they must be in accordance with the required atmospheric penetration ability.

Both pulse and frequency modulated carrier waveforms are used in active mode in millimeter wave contrast detectors. These have found application in solid-state transmitters with relatively little power, taking into account the cost of small terminal-driven vehicles and limitations with respect to volume and power. Preferably in transmitter devices that use pulse-modulated waveforms, "Impatt" diode oscillators are used. The applicant according to the present invention can use a frequency-modulated waveform and a Gunn diode oscillator transmitter and represents a significant advance in relation to the system described in US patent document 3,921,169. The present invention also has a general relationship to what is discussed in US Patent 4,200,871.

Another significant function of ground target contrast seekers involves signal processing for discrimination against the terrain-reflected clutter energy occurring in active mode, which competes with the mainly point-reflected energy. Both pulse and frequency modulated systems with continuous wave can use distance resolution to reduce clutter reflection in active mode, by effectively reducing the irradiated terrain area, which would otherwise appear from the antenna beam interception. The pulse systems use narrow pulses and time gates to achieve distance resolution. These systems must generally use wide receiver intermediate frequency bandwidths to receive the narrow pulse. Bandwidths of at least 1/f are required, with X denoting the pulse duration in seconds. The system using incoherent frequency-modulated waveforms can transmit energy over wide bands to perform terrain and precipitation clutter decorrelation, and still use narrow receiver-intermediate frequency bandwidths. This implies an advantage in connection with maximizing the signal/total noise ratio (S/Nfc). The active-mode target detection range of millimeter-wave contrast seekers is usually limited by the target's signal-to-background (S/NB), i.e., by the terrain-reflected energy, indicating the desirability of minimizing the antenna beamwidth. However, under certain environmental conditions, e.g. low terrain reflectivity and adverse atmospheric conditions, S/Nr become a factor that limits range performance. The size S/Nr is defined as the signal-to-receiver-noise ratio. This is especially the case if you want a relatively long detection distance in a system that operates at the higher millimeter wave frequencies, where stronger atmospheric attenuation occurs. Thus, the maximization of S/Nr will be an important construction factor. Distance resolution in frequency-modulating systems, which are used to minimize noise caused by terrain and precipitation and to measure the distance to the target/terrain, is performed with frequency-gated coupling instead of time-gated coupling. Millimeter wave contrast seekers that use both horizontal paths and nearly vertical paths during target acquisition have been demonstrated. Horizontal track systems can make better use of distance resolution to reduce background clutter during target acquisition, due to the antenna beam suppression angle Y that is usually used (in the order of 25-30 degrees from the horizontal). The distance resolution (area-group) with regard to the capture length on the terrain is increased above the current distance resolution by a factor of 1. It should be noted that for a complete vertical-cos y

system, where = 90°, the terrain clutter reduction that can be realized on the basis of distance resolution will be zero. Other typical differences between millimeter wave contrast seekers for horizontal and near-vertical target acquisition mode paths include the search pattern used and the related target detection signal processing implementation.

Stabilization of the seeker system is the means by which the seeker line of sight (LOS "seeker line of sight") is disconnected and made independent of vehicle body rotation. Two methods with regard to prior art will be briefly described here. There are generally two steering axes, but in fig. 1 and 2 only elevation is shown. In the known system according to fig. 1 there are two velocity gyroscopes which are placed on an antenna 1 on mutually orthogonal axes, one for sensing elevation movement and the other for sensing azimuth movement. Any disturbance torque induced by the vehicle's motion, e.g. bearing friction, will tend to rotate the antenna 1. The speed gyroscopes will immediately sense this, and send a corresponding signal to the amplifiers and thus to the torque motors, which balance the disturbance torques and keep the antenna speed approximately equal to zero. There is a further amplifier input signal from the millimeter wave sensor, which commands the antenna 1 to track the target. When the tracking error £■ is zero, the velocity command will be zero. In fig. 1, and more particularly with regard to the elevation control channel, any motion induced torque will tend to rotate the antenna 1 about the elevation axis 9. The elevation rate gyroscope 4 senses the rotation and sends a corresponding signal to a servo amplifier 3 via a wire 6 and thus to the elevation torque motor 2 , which thereby keeps the antenna speed essentially at zero. The input signal from terminal 5 from the millimeter wave sensor commands the antenna 1 to track the target. The correction of the azimuth axis error takes place in a similar way.

In the known gyroscopically stabilized system with two degrees of freedom according to fig. 2, a swing mass 7 is used directly to stabilize the antenna 1. Any disturbing torques are automatically counteracted by the swing torque of the swing mass 7. Small precession errors are detected by the millimeter wave sensor and cross-axis torques are automatically applied there. If e.g. an elevation error becomes apparent, an azimuth torque transmitter 8 is brought into action through the servo amplifier 3 to pre-set the antenna 1 about its elevation error to zero. Azimuth error correction is accomplished in a similar manner.

US 3,728,724 deals with an adaptive sweep-frequency active radar system that overcomes the disadvantages of pulsed systems, as it proposes an active radar that uses continuous wave signals instead of pulse signals.

US 3,924,235 deals with a digital antenna positioning system for the antenna for a radar search system, without the use of velocity gyroscopes. A digital target seek line error signal representing the error between the radar beam seek line and the target seek line for a seek line coordinate system is generated and then referenced to a fixed coordinate system. In the case of a radar system that uses an antenna with an axis system corresponding to the beam line-of-sight axis system, the line-of-sight error signal will be referenced to a fixed coordinate system by first referencing the error signal to an aircraft axis system and then to a fixed coordinate system to obtain a fixed coordinate-referenced error signal. The fixed coordinate-referenced line-of-sight error signal can then be used to generate fixed coordinate-referenced line-of-sight error velocity and position signals using a predetermined transfer function and an integrator with a predetermined fixed coordinate system-referenced integration constant. The line-of-sight position signals which refer to the fixed coordinate system can then be used to generate antenna angle pointing error signals which can be used to drive the antenna in a direction that tends to zero out the line-of-sight error signal.

The present invention is defined in the appended claims and provides an active frequency modulated continuous wave targeting system with vehicle body-fixed speed sensor stabilization. The search system operates in the active frequency modulated continuous wave radar mode, using multiple range groups for target detection and

- search. The seeker system provides line-of-sight airspeed control signals to the vessel or airframe to perform proportional navigation. In a preferred form of the invention, this includes a microwave transmitter which provides a sweep frequency modulated carrier wave and which also provides local oscillator signals. A transmitter feeder and four surrounding receiver feeders cooperate with an antenna that uses polarizing elements. After signal mixing, the amplified received signals will be processed by a surface acoustic wave filter which provides narrow frequency channels that serve as spacing groups. A multiplexer scanning the multichannel filter output controls a target acquisition detector that initiates target angle tracking. It also controls a differential amplifier for homing in terms of terrain or background plus target distance. A range search generator is provided for repetitive movement of a range group or gate from greater to less than the distance from the seeker to terrain, until the range lock is instituted by a range lock threshold stabilizer. The stabilization system is designed around a dual-axis servo system that drives a set of cooperating wobble arms that support the polarization turntable antenna aperture. Tachometer speed sensors for elevation and azimuth and position sensors, which are driven both directly by sway bar servo torque motors are arranged along with a pair of chassis-mounted dual-axis

speed sensors that obtain speeds for the vessel's pitching, pitching and rolling. Also incorporated into the system is a wobbler servo angle search command generator for target acquisition. Tracking demodulators for azimuth and elevation angle determine the line of sight to the target, error, and command line-of-sight velocity for the yaw hoops during homing and provide line-of-sight proportional signals to the vessel's autopilot.

The invention will now be described in further detail by means of examples and with reference to the attached drawings. Fig. 1 and 2 are schematic drawings regarding known target seeker antenna stabilization systems. Fig. 3 is a block diagram of a millimeter measuring sensor system, showing the electrical components and their mutual connection, according to the present invention. Fig. 4 is a side view, partially in section, of an antenna and stabilization system according to the present invention. Fig. 5 is a detailed block diagram showing the components and their electrical connections in the stabilization system according to Fig. 4. Fig. 6 and 7 are respectively elevation and azimuth view, partly in section, of features of the antenna shown in fig. 4.

Fig. 8 and 9 illustrate details of the antenna feed.

Fig. 10 is a flow chart of angle tracking modulators showing their electrical components and their interconnection. Fig. 11 is a logic table which is useful for explaining the operation of the present invention. Fig. 12 illustrates signal waveforms which are useful in explaining the operation of the apparatus according to fig. 10.

Fig. 13 is a block core over r.f. and i.f. the receiver stations in the applicant according to the present invention

neise.

As can be seen from fig. 3, which represents the millimeter-wavelength target sensor portion of the present invention, millimeter-wavelength transmitter and local isolator signals are provided by a microwave oscillator 41, such as can be a regular Gunn diode oscillator. The output from the oscillator 41 is connected via a waveguide 28 to an ordinary, centrally located feed unit 21 for an antenna 20 (see also the feed system 252 in Fig. 9). The antenna 20 may be of any conventional form, including a preferred form which will be discussed below, but which includes an array 244 (Fig. 9) of receiver feed units which can be made receptive in conventional cyclic or monopulse receiver modes. Any received echo signal is coupled by means of an r.f. switch 22 via a waveguide 27 to a conventional broadband microwave mixer 44, together with a cooperating local oscillator signal coupled from the oscillator 41 via a directional coupler 29 and a waveguide 40. It shall note that the oscillator 41 and consequently the transmitted and local oscillator input signals comprise a continuous wave of frequency modulated signals. A linear sweep signal for the oscillator 41 can be supplied from a voltage-controlled oscillator 43 and a conventional linearizing circuit 42, if required. The oscillator 43 is controlled by incoming signals which are selected by a switch 45, the signals appearing on the lines 47 and 48, as will be explained below.

It should be understood by those skilled in the art that the invention as described here can be used over a wide range of frequencies. Operation at 30 GHz to 100 GHz in the millimeter wavelength frequency range is particularly advantageous.

The mixer 44 feeds an intermediate frequency amplifier with a relatively narrow band, which is supplied with an amplifier control signal, as will be explained later, via a line 84 from a multiplexer 83. The output from an i.f. reinforces 8 branches in respective branch paths 86, 87, and 89 to resp. a multi-channel filter 81, a limiter discriminator 88, and a threshold detector 90, as will be explained in more detail below.

The multichannel filter 81 receives an i.f. output signal on a line 86 and may comprise n conventional parallel surface acoustic wave filters for passing through side-by-side arranged adjacent narrow frequency bands of signals representing a plurality of narrow frequency bands or distance groupings. The n outputs from the filter 81 pass separately through a set or group of a corresponding plurality of diodes, with a polarity as shown in the figure, to n inputs to the multiplexer 83, the latter providing means for scanning the plurality of outputs. The narrow multi-channel band filter 81 provides narrow distance groupings, so that a high distance resolution is achieved, typically 0.5% - 2% of the fence distance. This is used to reduce terrain clutter that competes with the target signal. The antenna beam's terrain reception can e.g. is divided into 16 areas, which are narrow in the distance direction, by the use of 16 distance groupings.

The multiplexer 83 provides special, resp. branch outputs on lines 84, 85 and 72. The output on line 84 represents the aforementioned amplifier control signal which is used e.g. of i.f. the amplifier 8, while the error signal components on the line 85 are supplied to the first inputs of the azimuth and elevation servo demodulators 67 and 68. The line 72 supplies the same output signal to a target 9 acquisition detector 71, the latter initiating automatic target angle search through operation of a link 70 and the following movement of switches 65 and 66 to the right in fig. 3 of the drawing. For the supply of an angle search phase reference signal in the demodulators 67, 68, ordinary quadrature reference signals are available in an r.f. switch 22 because of the autonomous reference generator housed therein, the reference signals being fed via a line 26 to the demodulators 67, 68 where they are used together with the signals on the line 85 to provide azimuth and elevation error signals for respective supplies, via lines or 63, 64, to respectively the azimuth and elevation servos 60 and 61. Velocity sensors, which will be discussed in more detail below, and which are indicated by the single package 62, provide stabilization signals to the servos 60, 61. When a target is acquired, the line of sight for the antenna 20 be controlled in azimuth and elevation by means of the servomotors 60 and 61 and the respective connections 23 and 24, as will be discussed later. If there is no acquisition detection signal at the detector 71, the switches 65, 66 will move to the left in fig. 3, so that there is no input signal to the elevation servo motor 61. On the other hand, the switch 65 will connect the input to the azimuth servo motor 60 to a search command generator 69 which serves to scan the azimuth search.

As stated above, a branched output from the i.f. the amplifier 80 on line 87 is supplied via line 87 to the limiter-discriminator 88, and via a line 89 to a threshold detector 90. Lack of a signal detected by the threshold detector 90 means no output signal at terminal 73 from the detector 90, and there will no signal be applied at the same terminal 73 as an input signal to the search command generator 69. Under these conditions, the search command generator 69 will not provide a triangle wave output signal on the wire 63, because the azimuth scan is not desired until the terrain distance locking takes place.

The threshold detector 90 serves as a distance lock detector and also controls an internal actuator to move joints 46a, 46b up and down in fig. 3. In this way, either the output of the line 48 from the area search generator 97 or from an integrator 92 on the line 47 can be supplied to the respective RS or RT terminals of the relay switch 45. The distance or area search generator 97 produces a sawtooth wave to repetitively move the distance grouping or - the gate from a distance greater or less than the distance from the seeker to the terrain until distance locking takes place.

The distance search function makes use of a fully active i.f. bandwidth output signal (effectively a wide group or grouping) to initially lock onto the terrain, which makes greater use of terrain-reflected energy compared to what would be available from one of the narrow area group filters of the multichannel filter. It should be recognized that in a sweep frequency modulated active continuous wave radar system, the distance to terrain or terrain plus target may be measured to keep the active i.f. center (bit) frequency essentially constant and centered inside the i.f. the tape. Detection can take place in any of the distance groupings (eg grouping n in Fig. 3). The multiplexer 83 scans the distance group filters 81 and the acquisition detector 71 selects the group together with the target. This detector 71 can be a simple threshold level detector, or it can be a target signal detector similar to what is described in fig. 2 in US patent document 4,150,379. In a similar way, the selected (n-1) and (n+1)" signals from the multiplexer 83 could be supplied via the lines 95, 96 to an amplifier 94, to provide a differential output signal via the line 93 to a terminal on a relay switch 91. Range finding after detection of the target is performed by comparing energy in alternating (n-1) and (n+1) area groupings, for example groupings 3 and 5 if the target is in grouping 4. The correct groupings for distance search, i.e. on either side of the target group, is automatically selected at the time of target detection by the multiplexer 83. According to the position of the link 46b, the output of the differential amplifier 94 can be connected to the integrator 92, or alternatively, the output of the limiter discriminator 88 can the integrator 92 is connected.

With reference to fig. 4 will work for the antenna 20 in fig. 3 now be described in a discussion that is limited to the elevation axis of the system. It will be obvious that the system in question uses scanning and stabilization about two mutually perpendicular axes. The antenna, which is of dual mode with fast scanning and fast searching, is suitably a device with very little moment of inertia, which eliminates unnecessary antenna driving forces. In fig. 4, the feed system 103 is centered essentially at the axis of the vessel, and is arranged to irradiate a fixed, symmetrically arranged parabola reflector 101. The reflector 101 is a conventional polarization-sensitive, shaped plate or sheet and reflects or emits energy incident on it, depending on the plane of polarization for the incident millimeter energy. The primary feed horn 252 (Fig. 9) for the antenna feeder 103 (or 244) is polarized so that the parabolic reflector 101 reflects and focuses the spherical wave incident on it in a flat phase front. The collimated transmitter beam thus formed is directed at the scanning mirror 102. This is arranged in a conventional manner to rotate the plane of polarization of the flat phase front through 90 degrees and reflects the electromagnetic beam backwards towards the parabolic reflector in a new direction determined by the angular position of the mirror 102. Because the reflected radiation pattern is polarized orthogonally to the polarization of the initiating feed horn 252, it will be passed with little loss directly through the polarization discriminating parabolic focusing reflector 101. The reflector 101 may serve as a radome for the apparatus, or a separate radome 100 can be used.

Details of the microwave construction used in building the antenna reflector 101, 102 do not necessarily need to form a new part of the present invention, because there are a plurality of easily accessible solutions to the problem. Leon Schwartzman and Robert W. Martin describe a practical arrangement in the technical journal: "A Rapid Wide-Angle Scanning Antenna with Miniminum Beam Distortion", published in Proceedings of the Fifth Annual East Coast Conference on Aeronautical and Navigational Electronics, October 1958.

Martin and Schwartzman used a parabolic focusing part 101 consisting of an aluminum honeycomb interlayer structure to which was attached a grating in the form of a metal strip. The grid size and the spaces and interlayer dimensions were balanced to ensure reflection for one polarization and strong transmission for orthogonal polarization.

In the present invention, the parabolic focusing reflector 101 comprises the above-mentioned flat metal strip grating which is bonded to a cross-linked styrene copolymer substrate which is usually used as a microwave dielectric material, e.g. one such material manufactured under the trade name "Rexolite" and marketed by Oak Materials Group, Inc., Franklin, New Hampshire 03235, USA. The scanning mirror 102 has a two-fold function, in that it firstly introduces a linear phase shift on the flat phase front. The resulting pattern therefore becomes the secondary pattern of a constant-phase aperture field that is rotated through an angle twice the angular displacement of scanning mirror 102. Second, scanning mirror 102 rotates the polarization of the energy incident on it through 90 degrees. The scanning mirror 102 uses a grating part which is similar to that present in the paraboloid reflector 101, and which may comprise a layer of low dielectric, e.g. isocyanate foam over a metal grounding plane, with an orientation in the longitudinal direction of 45 degrees in relation to the polarization in question. In the present invention, a glass microfiber-reinforced PTF material can be used, which is usually used for stripline and microstrip circuit applications, e.g. of the type manufactured under the name "duroid" and marketed by Rogers Corporation, Micromet Division, Box 700, Chandler, Arizona 85224, USA, instead of isocyanate foam.

It should be understood by those skilled in the art that the antenna 20 is preferably a compact device with a low moment of inertia and consumes little power, which allows for maximum aperture and minimal antenna beam interception at terrain level. The radiated background clutter in the active mode is minimized, as well as the background radiation effect at the receiver input during the passive mode. Because the antenna pattern is controlled by an angle that is twice the angular movement of the turntable mirror 102, the total field of view of the antenna 20 in both planes will be maximized. Because the antenna feeders 244 are stationary, a conical scan motor can be eliminated, as well as complex rotary microwave connections.

As can further be seen from the simplified single-axis system in fig. 4, and in scanning mode, the receiver horns 251 and 254, as can be seen from fig. 9, supply elevation error data v>j for sensor processing of the target sensor system 104 shown in detail in FIG. 3, and thus provide line-of-sight velocity data on line 116 for use of the elevation axis by the aircraft flight control system or autopilot 115 for operation of an elevation control surface 115a. This signal is also connected via a line 117 to an input to a summing device 112, with voltage inputs as shown. Main part speed signals which are provided by a main part speed device 113 are fixed in relation to the vessel's main part by means of a substrate 114 and are connected to another input of the summing device 112. The scanning loop is completed via the summing device 112, an analog-amplitude-divider-with- two-circuit 111, another summing device 110, a servo amplifier 109, and the torque motor 106 for operating a link 105 which moves the scanning reflector 102 about its elevation axis. A speed stabilization loop is inserted in a path from the tachometer 107 which is driven by the torque motor 106 through a line 108, the second summing device 110, the amplifier 109, and the torque motor 106. It should be understood that an operating system will include an azimuth control system similar to the elevation control of FIG.

4, for operation of a flight control surface about its azimuth axis.

In a typical application of the terminal guidance search system, the seeker autopilot will control the flight of the vessel in a horizontal path during the target search in azimuth with the antenna pressed below the horizon at an angle of about 25-30 degrees. Before it arrives at the target area, the seeker is activated and a distance search is initiated, whereby the broad grouping-full active i.f. bandwidth. Terrain locking takes place within the first to third range search periods, and range search is initiated, i.e. the range search switch 45 is switched from search to tracking. With the range/search trace switch 45 in the trace position, the input from the voltage controlled oscillator 43 and the sweep repetition frequency for f.m. the oscillator 41 be controlled from the wide grouping distance homing output signal, which keeps the shock frequency centered in the active i.f. band. After distance tracking initiation, angle tracking will be initiated either automatically or by means of a timer signal. Target acquisition is performed by varying the antenna azimuth position back and forth at a fixed speed to complete a cyclic azimuth scan, which covers shielded areas in the terrain. Coverage of the search area in the distance direction is a result of the vessel's forward motion. A predetermined horizontal search width can be varied from a very few degrees, e.g. + 3 degrees, to the full azimuth yaw bar limit capacity, e.g. + 20 degrees, as desired and depending on the limitation given by the forward speed of the vessel. A point target that is detected in one of the narrow range grouping channels by the acquisition detector 71 will transfer the seeker from angle search to tracking. The outputs from the angle tracking demodulator 67, 68 will then control the movement of the azimuth and elevation antenna aperture swing brackets in order to be able to perform target angle tracking. At the time of initiation of target angle tracking, signals proportional to seeker-target elevation and azimuth line-of-sight velocity will be fed to the autopilot 115 for proportional navigation guidance. This type of navigation uses a speed change for the vessel's course that is proportional to the turning speed of the vessel-target and thus requires information from the seeker regarding line-of-sight speed. Since sequential lobing (or monopulse) is used for the antenna beam, the angle tracking demodulators 67, 68 will measure the position of the antenna lobe pattern center in relation to the target position and produce elevation and azimuth errors. The error signals are used to drive the antenna swing arms at speeds that are proportional to the errors and these are thus in reality speed signals for the line of sight. The same speed signals with conditioning are fed to the vessel's autopilot.

Left 250, up 251, right 253 and down 254 waveguide feeders (Fig. 9) can be scanned in left-right and up-down pairs using the i.f. the switch in fig. 10 via i.f. the circuit of fig. 13. The input terminals 261, 262, 263 and 264 are connected to the terminals resp. 312, 311, 310 and 313, and are further connected to the input terminals of switches 265a and 265b, the middle output terminals being in turn connected to the input terminals of switches 266a and 266b, while the remaining output terminals are connected to resistors 272, 273, 274 and 275. The output terminals from switches 266a and 266b are connected to input terminals of differential amplifiers 267 and 268 with pole connection as shown in fig. 10. A switch influencing device 267 affects the switches 265a, 265b, 266a and 266b and will further supply a switch signal f-| to the gate terminal inputs 267a, 268b of the gate-connected differential amplifiers respectively. 267 and 268. The output terminals 270 and 271 of the differential amplifiers 267 and 268 are connected to the elevation servo motor 60 and the azimuth servo motor 61, respectively.

During operation, the switch influencing device 265, which can make use of logic gates and microprocessor control for the production of switch signals f-j and ±2, as can be seen from fig. 12 and respectively waveforms 280 and 281, be arranged to actuate the switches 265a, 265b, 266a and 266b according to the signals f-| and ±2- The frequency of the signal f-| is twice that of f2 and is phase matched as shown in fig. 12. As can be seen from fig. 10, the switches 265a, 265b, 266a and 266b will be positioned for contact with the upper terminals, when the signals f-| and f2 has a value equal to zero, and will be in the lower position when f-| and f2 has a value equal to one. Thus, the switch output signals fa and f^ are controlled by the logic table according to fig. 11, so that the output signals fa and f^ appear on the lines 276 and 277, and comprise signals corresponding to the up-down and right-left signal pairs. The signal pairs are connected to the gated differential amplifier 267 and 268 which feeds a signal to their output terminals equal to the difference between fa and ffc, i.e. fa-fb. The differential amplifiers 267 and 268 are switched on and off by means of the gate switching signal f1, so that the up-down difference signal is supplied to the output terminal 270, and the right-left differential signals are supplied to the output terminal 271. An inverter 269 inverts the signal f-j and in this connection the differential amplifiers become 267 and 268 alternately ported on and off.

The up-down difference signal occurring at the output terminal 270 is amplified in intermediate frequency amplifiers, after which the signals are processed by means of elevation angle tracking demodulator circuits, and then connected to the elevation servo motor 61. The right-left difference signals that become available at the output terminal 271 are amplified in intermediate frequency amplifiers, after which they are processed by azimuth angle tracking demodulator circuits, and then coupled to the azimuth servo motor 60.

Alternatively, the up-down, right-left antenna output signals can be scanned at the antenna feeders instead of the i.f. frequencies, as such a set-up is shown in fig. 13. The input terminals 290, 291, 292 and 293 are connected to waveguide feeders 250, 251, 253 and 254 and also connected to mixers respectively. 300, 301, 302 and 303. The r.f. oscillator signal from the oscillator 41 is connected via an input terminal 298 and directional couplers respectively. 294, 295, 296 and 297. i.f. amplifiers 304, 305, 306 and 307 are connected at their input terminals to receive the output signals from the mixers or 300, 301, 302 and 303, and to obtain i.f. signals to output terminals 310, 311, 312 and 313, which in turn are connected to input terminals or 261, 262, 263 and 264.

During operation, individual r.f. signals received from the waveguide feeders 250, 251, 253 and 254 collide with signals received from the oscillator 41, in the corresponding mixers 300, 301, 302 and 303, the shock frequency signal f^ being amplified in the i.f. the amplifiers respectively 304, 305, 306 and 307, so that a four-channel receiver is formed. i.f. the signals from the four-channel receiver are connected to input terminals 261, 262, 263 and 264 to enable sampling of the intermediate frequency signals corresponding to the radio frequency signals. The demodulator of fig. 10 provides error correction signals to the azimuth and elevation servo motors 60, 61. At the time of target detection, the range tracking switch 45 will automatically be switched to reverse plus target position data and a more accurate narrow grouping, e.g. (n-1), (n+1) which implies the start of distance tracking. After angular tracking initiation, target tracking and vessel terminal guidance will continue, resulting in a direct hit on the target. If the seeker structure includes a passive or radiometric mode and the surrounding conditions are favorable, the seeker will automatically be switched to its passive mode with a relatively short range, e.g. 300 m, for improved terminal accuracy and for a hit that is close to the physical center of the target.

Since reference must again be made to fig. 4, the basic methodology for stabilizing the applicant's line of sight must be mentioned there. In the system, antenna 102 uses the torque servo motor as this works together with speed sensor 107, speed sensors 107 being made up of a tachometer which senses the speed of the antenna in relation to the main component of the vessel. To cancel vessel movement disturbances at the antenna 102, the speed sensor 113, which is fixed in relation to the main part, will measure this movement and drive the antenna 20 or 102 in the opposite direction to keep its pointing in a fixed direction. The velocity command from the millimeter wave sensor 104 drives the antenna 20 or 102 to track the target. As can be seen from fig. 4, the rotating reflector antenna 102 acts as a mirror and the viewfinder's line of sight will thus not correspond to the center line of the reflector plate. The plate angle in space is exactly half of the viewfinder angle-line-of-sight in space. The plate speed /3 is controlled so that ft> = 1/2 ép where ép is the vessel's heeling speed.

Due to the peculiarity of the particular antenna steering, stabilization and main body motion decoupling subsystem in the seeker, features of this subsystem will be discussed in further detail with reference to FIG. 4, 5, 6 and 7. As indicated previously, the rotary reflector 102 will have significant advantages with respect to packaging and drive power. Because only a thin plate is moved to direct the seeker line of sight and because the reflector plate has a two-to-one gain, it is easy to achieve usable seeker line-of-sight angles of +20° or more with an aperture diameter that is 90% or more of vessel - the diameter. The low moment of inertia of the plate 102 minimizes the requirement for electrical power for acceleration of the line of sight. This low power consumption minimizes radio frequency interference and torque servo motor heating problems commonly experienced with other torque motor drives. Because the turning reflector behaves like a mirror with a gain of two, the seeker line of sight will inherently be coupled to the vessel motion. This connection is removed by the control implementation shown in fig. 5. Tracking stabilization and search stabilization will be discussed.

As can be seen from fig. 6 and 7, the reflector 102 includes a central aperture 245 which provides a waveguide feeding system 244 shown in FIG. 8 and 9, and made with pivot storage for horizontal movement in pivot bearings 232 and 247 which are diametrically fixed on an inner wobble hoop 231. This wobble hoop 231 is in turn provided with opposite pivot bearings 223, 236 for vertical movement of the one with aperture ( 246) supplied wobble bracket 231 and therefore plate 102. The pivot bearings 223, 236 are suspended in yokes 230, 235 which are attached to the vessel's main body 234. An azimuth torque servo motor 210 which is attached to the vessel's main body drives "pick-off" aids which is attached to it and also drives a joint connection 239, 238, 237 for positioning the reflector plate 102 in azimuth. In a similar way, the reflector plate 102 is positioned in elevation by means of a torque motor 150 and joint roots 249, 233, 248. The described movements take place in relation to the antenna feed system 244 which is fixed in relation to the main part.

As can be seen from fig. 5, it will be seen that the rotor of the elevation torque servo motor 150 is coupled by the same shaft 148 to drive a tachometer 151 and an elevation position pick-off potentiometer 152. Similarly, the rotor of the azimuth servo torque motor 210 is coupled by means of the same shaft 149 to a tachometer 211 and to a "pick-off" potentiometer 212 for azimuth position. Gyroscopes 170, 180, 195 which are attached to the main part and which act for respectively tilting, rolling and turning add further styling cues.

The speed summing amplifier 154 transmits its output signal via a line 178 to a tachometer summing amplifier 179. The input terminals of the speed summing amplifier 154, which have poles as shown in fig. 5, includes a signal on the line 160 indirectly coming from the pitch rate gyroscope 170 coupled via a line 171 to the input of the one input to a main part or vessel speed summing amplifier 172, with pole connection as shown, and a signal on a line 173 from a conventional analog multiplier 184. Another input terminal of the amplifier 154 is selectively derived via a scaling amplifier 17 from the two pins of a switch 157, which for the sake of clarity is shown as a relay which is acted upon by an influence device 155 which is duplicated at the top and bottom of fig. 5, although in reality they are built in one. The speed summing amplifier 154 has a total gain of 0.5. The selectable signals include the output signal <^e on line 161 from an angle summing amplifier 162, or the elevation error output signal 6e from an angle tracking demodulator 166 on lines 163, 165. The inputs to a tachometer summing amplifier 179, with poles as shown, include the output signal /3c from the speed amplifier 154, while the tachometer summing amplifier 179 supplies its output signal via a line 153 to operate the elevation torque servo motor 150. The combination of the speed summing amplifier 154, the elevation torque motor 150, the tachometer 151, the tachometer summing amplifier 179 and the drive link 148 form the elevation speed servo which is the heart in the elevation driven scheme. The bandwidth for the servo can e.g. be 60 Hz. The scaling amplifier 177 multiplies the signals received at the input terminal by a predetermined constant K.

Similarly, in the azimuth tracking channel, a speed summing amplifier 215 will transmit its output signal via a line 214 to a tachometer summing amplifier 218. The inputs to the speed summing amplifier 215, with poles as shown, include a signal on a line 198 which comes indirectly from a rate-of-turn gyroscope 195 which is connected via a wire 196 to one input to a vessel summing amplifier 187, with poles as shown, and a signal on a wire 187 from an analog multiplier 186. Another input to the amplifier 215 is selectively derived via a scaling amplifier 206, from the two pins of a switch 216 shown at the bottom of the drawing, and also here influenced by the influencing device 155. The speed summation amplifier 215 has a gain of 0.5. The selectable signals include the output signal d a on line 220 from the angular summing amplifier 219 or the azimuth error output signal £ a from the angular tracking demodulator 166 on line 201. The inputs to the tachometer summing amplifier 208, with poles as shown, include the output signal Y"c from the velocity amplifier 215, with the tachometer summing amplifier 208 transmitting its output signal via line 207 to operate the azimuth torque servo motor 210. The combination of speed summing amplifier core 215, the azimuth torque motor 210, the tachometer 211, the tachometer summing amplifier 208 and the drive link 149 form the main parts of the azimuth speed servo in the azimuth drive device. The scaling amplifier 206 multiplies signals it receives at its input terminal by a predetermined constant K.

Signals from the roll rate gyroscope 180 on a wire 181 are used jointly in the two elevation and azimuth channels mentioned above. These roll rate gyroscope signals are coupled together via branch lines 182, 183 to respective duplicators 184, 186, which further multiply the products of their input signals by a factor of 2. As indicated above, the antenna azimuth position from the azimuth potentiometer 212 will be coupled via a wire 185 as the second input to the multiplier 184, while the elevation position from the potentiometer 152 is connected by means of the wire 159 as another input to the multiplier 186.

The output of the vessel speed summing amplifier 172,

22 is, in addition to being supplied to the velocity summation amplifier 154 via the line 160, also supplied to the integrator 175 via a line 174. The output from the integrator 175 is, as stated above, fed via the line 176 to the one input of the angle summation amplifier 162. In a similar way, the output of the vessel speed summation amplifier 197, in addition to being interleaved with the speed summation amplifier 215 via 198, is fed to the integrator 200 via line 199. The output of the integrator 200 is, as indicated above, supplied via line 218 to the one input from the angular summing amplifier 219. A third input terminal of the angular amplifier 162, with polarity indicated as shown, is connected to receive the output signal /3 from the potentiometer 152 via the scaling amplifier 169. Similarly, a third input terminal of the angular amplifier 219, with poles as shown, will be connected to receive the output signal V from the potentiometer 212 via a scaling f amplifier 215. The scaling amplifiers 169 and 206 function to multiply their respective input signals by a factor of 2. It will be understood by those skilled in the art that the angular tracking modulators 166 of FIG. 5 is similar to the demodulators 67, 68 in fig. 3, in that the elevation demodulator in block 166 supplies a measurement of the elevation tracking error £ e ^ to the elevation error scaling amplifier 177, while the azimuth demodulator in block 166 supplies a measurement value of the azimuth tracking error é a to the azimuth error scaling amplifier 206.

Furthermore, there is arranged a sensing command generator 188 for the production of command signals /\ åe±, A <3az for supply via lines 167, 189 to respective inputs of angle summation amplifiers 162, 219. To initiate angle search, the influence means 155 will react to an input signal of terminal 156 by placing the two switches 157, 216 in their upper positions. The influencing member is driven directly from acquisition detector 71 in fig. 3. The elevation search error signal &e on line 161 was now formed from the summation of the search command signal ?) fie± on line 167, the elevation reflector plate angle signal 2/<3 > coming from scaling amplifier 169, and the integrated vessel speed compensation signal received from the output of the integrator 175. The closed servo loop acts to keep the search error signal c) e generally small, so that the output of the potentiometer 152 is quite precisely equal to half the difference between the search command signal on wire 167 and the output signal from the integrator on wire 176. This realization compensates for vessel- movement, so that the line of sight in space is approximately proportional to the search command signal.

Under automatic tracking, it is desirable for the antenna stabilization system to control the speed of the antenna reflector plate /3 according to the following equations.

where:

A se = ^a current seeker elevation-line-of-sight speed, ép = vessel's rate of inclination,

= azimuth angle of the reflector plate,

0R = vessel's roll speed.

These signals are shown in fig. 5.

The output signal / 3 c from the speed amplifier 154, in tracking mode will be

where:

é e = angle tracking elevation error signal provided by the angle tracking modulator 166,

K = a constant as provided by the scaling amplifier 177.

The basic governing law for the elevation sight line for the seeker in search and track mode is:

where: A clei = the desired searcher's line of sight in elevation, A\ se = ^a current searcher's line of sight in elevation,

and for tracking mode:

Thus from equations (3) and (4) you will have This is the signal at terminal 164 in fig. 5, and in tracking mode is connected to the slope channel from the autopilot. From equations (2) and (5), one obtains The servo loop, which includes the tachometer summing amplifier 179, the elevation servo motor 150 and the tachometer 151, functions so that the plate speed in question approaches the plate speed command signal ^ c, so that

and the results from equation (1) will then essentially be achieved.

In a similar way, one has Eq

where:

Y = desired azimuth speed for antenna reflector plate,

Å SA = current seeker azimuth line-of-sight speed,

= the elevation angle of the reflector plate, and this equation is realized for controlling the antenna reflector plate in azimuth.

The output signal 7 c from the speed amplifier 215 in tracking mode will similarly be according to equation (2), be:

and analogously to equation (5) which is the signal at terminal 222, and in tracking mode this is connected to the turning channel from the autopilot. Also in a manner similar to that described for elevation control, the azimuth servo loop will operate so that the relevant plate speed <V>" will approach the plate speed command Vc, so that and one will then mainly obtain the result according to equation (8 ).During search mode, the output signal fac from the speed amplifier 154 will be equal to equation (2)

where:

de = angle error signal in elevation, acquired at the angle amplifier 162.

For search mode you will have

where <) £ ei is obtained on line 167 from the search command generator.

The current seeker line of sight in elevation, ^SE' is then determined and subtracted from A ^ e±, and then in the angle amplifier 162, so that: Multiplication of the error signal de by the factor K results in the desired seeker line of sight velocity in elevation, so that

and equation (3) is satisfied.

In a similar way, the azimuth device in search mode will give the following for equation (14): where ^a is provided by the angle amplifier 219 on wire 220, and A<3az, is provided by the search command generator 188 on wire 189. Equation (15) then becomes

and again equation (3) is satisfied.

While referring to fig. 6 and 7, it will be understood by those skilled in the art that the plate azimuth angle V need not be equal to the azimuth motor angle ¥ m, and the plate elevation angle <&> need not be equal to the elevation servo motor angle /*?m. The relationship between them can be approximated using the following equation:

where the distances Ra, ra, Re, re are also shown in fig. 6 and 7.

The speed changes for the plate angles a and Y in relation to the speed changes regarding the motor angles / 2 m and Ym can be found as follows:

where determines the azimuth joint gain, and determines the elevation joint gain. Typical for is 0.25 to 0.35. The maximum seeker line-of-sight angle is generally 20 degrees, which requires plate angles ^ and ty" of 10 degrees, and consequently motor angles P<>> m and Y m of approximately 40 degrees. However, most modes of operation will take place at angles less than half that of these values. It is clear that for plate angles less than 5 degrees the cosine term will be close to unity and therefore of little importance. However, the motor angles m and Vm of 20 degrees are significant. The cosine for 20 degrees is approximately 0, 94, which would ordinarily reduce to a 6% gain reduction with respect to the zero angle case. In the present invention, this gain reduction is compensated for by the use of a tachometer in a feedback configuration, comprising a gain approximately proportional to the cosine of the servo motor angle. Above a wide range of frequencies is the degree of servo motor gain m. 1 $ c and ¥m/ Vc Proportional to the reciprocal value of the tachometer gain gene, and can be expressed as:

where:

/3 «c = the total speed command,

Rpak = the tachometer gain constant.

Thus, the antenna velocities Æ and V± in relation to the total velocity command signal $ c and ¥ c appearing at the servo motor inputs and due to the vessel velocity sensors and angular tracking demodulator signals will be found to be as follows:

as a result, the linearity of the tachometer will not effectively cancel the most significant non-linearities of the joints.

During operation of the apparatus according to the system (see Fig. 3), power will be applied to all the circuits, including the oscillator 41 and the antenna sling arm torque motors 150, 210. The range finder and range follower switch 45 is held in its upper or range finder (RS) position. In a similar way, the switch 91 is kept in its upper or BRT position by means of the threshold detector 90. The switch 65, 66 for angle search and tracking is kept in the angle search position, i.e. to the left in fig. 3. The pattern emitted by the antenna 20 is directed downwards in elevation below the desired depression angle in relation to the horizon, while it is kept centered in azimuth.

After a short warm-up period, the range finder generator 97 is switched on and a varying sawtooth voltage is provided via the wire 48 and the switch 45, to the voltage-controlled oscillator 43. The time from a period for the sweep from the range finder generator 97 can comprise one or two seconds. The voltage controlled oscillator 43 provides a much higher frequency for the periodically varying sawtooth output signal which is supplied to the drive input of the millimeter wave oscillator 41, which is driven to provide a linearly swept, frequency modulated millimeter carrier wave. The output from the oscillator 41 is connected to the fixed antenna seeker feed horn 252 which projects through the antenna turntable 102, and is transmitted with vertical polarization. The transmitted energy is reflected from the terrain, appearing on the four input feed horns 250, 251, 253 and 254 via r.f. switches 22 and is transferred to the low-noise digital mixer 44, where it is converted to an intermediate frequency. Antenna 20 and the other r.f. components and the mixer and preamplifier 44 can be performed wideband to maximize their efficiencies in the passive or radiometric mode, if this mode is implemented. A small amount of power that is coupled from the oscillator 41 serves as a local oscillator signal in the mixer 44. The mixer and preamplifier 44 provide an output which is applied to the relatively narrow band in the i.f. the amplifier 80. If the frequency modulation is varied due to the distance search generator 97 and its input to the oscillator 43, the shock frequency f^ between the transmitting and received sawtooth waveforms will be varied. This variation has direct correspondence with the area of the reflecting surface because the slope of the transmitted (and received) waveform is directly proportional to fm, so that the distance search is completed by variation of fm. The basic FMCW distance equation for the seeker concept according to the present invention is

where:

R = slope rate,

C = velocity of propagation in free space,

Af = bandwidth of the transmitted FMCW signal,

fb = pulse frequency between transmitted and received FMCW signal, and

fm = VCO 43 output signal frequency.

Typically, the distance search is in larger (below terrain) to smaller (above terrain) areas, so that e.g. a vessel with a horizontal trajectory flying at an altitude where the slope rate from the seeker to the terrain (for a typical depression angle) is 1.2 km, the distance search distance will be 1500-900 m.

i.f. the amplifier 80 will have its output connected to the limiter discriminator 88 and the threshold detector 90, the latter controlling the switch 5 for distance search and tracking. When the shock frequency between the transmitted and received millimeter waves appears with sufficient amplitude in the i.f. the amplifier 80, and exceeds the threshold detector's 90 setting, the detector 90 will set the switch for distance search and distance tracking to the contacts RT for distance tracking. The discriminator 88 will then, with its output signal, control the oscillator 43 by feed-through through the BRT/B+T RT switch 91 and the integrator 92. In this background distance tracking mode, distance tracking will be completed using the full i.f. amplifier bandwidth, and the discriminator will thus form a tracer with a relatively wide distance grouping. When range tracking begins, target angle tracking will also be initiated by a signal from the range tracking threshold detector 90, which is transmitted to the target angle tracking command generator 69 via terminal 73. The azimuth antenna sling hoop position is varied back and forth about its center position to form a horizontal scan. Target acquisition in the distance direction is completed internally by the vessel's movement in the forward direction.

When the target is irradiated during the search mode, the reflected energy will appear at the four receiver horns 250, 251, 253 and 254, and the energy will then be fed through switches 22 to the mixer and preamplifier 44. i.f. the frequency that makes up the above-mentioned shock frequency is supplied i.f. the amplifier 80. This amplifier 80 will transmit its output signal to the multichannel filter 81 which effectively forms narrow area groupings, as there are typically 16 groupings. The narrow distance grouping width is determined using the desired distance resolution, e.g. 1% of the slope distance and by limitations imposed by the sweep linearity that can be achieved with the oscillator 41. A linearizer or shaper 42 can be used in order to improve the basic linear characteristic of the oscillator 41. Target detection takes place in a single area grouping/ the n' t grouping, as the multiplexer 83 scans the outputs of the distance groupings. The range resolution available in a single range grouping is effective in increasing target signal-to-background noise (S/NB) for target detection.

When the target is detected, target acquisition, i.e. initiation of target tracking where sequential lobing is used, will take place almost immediately, e.g. within 0.2 milliseconds, enabling target angle tracking to be performed. At this time, the range acquisition detector 71 will transition the target angle search and tracking switches 65, 66 to angle tracking, and the antenna azimuth and elevation jibs are controlled from the angle tracking demodulators 67, 68. The angle tracking demodulators 67, 68 provide target area tracking error signals that serve to drive the antenna slings at speeds proportional to the measured error. These signals are thus effectively proportional to the seeker-to-target line-of-sight velocity. Versions of the signals are provided for

the autopilot for the purpose of proportional navigation guidance.

At the time of meter acquisition and conversion to target angle tracking, the distance tracking BRT/B+T RT switch 91 is switched to the B+T RT position (background plus target) for distance tracking. Range tracking is then performed by comparing the outputs of the adjacent narrow area groupings (n-1) and (n+1) on either side of the measurement tracking grouping (n), effectively providing a narrower area gate for range tracking and for rejecting terrain clutter and precipitation clutter which backfires. The amplitude comparison between (n-1) to (n+1) groupings is performed by means of the differential amplifier 94 in FIG. 3. It should be understood that the bandwidths of the i.f. the amplifier 80 must be wide enough to cover the total number of distance groupings (filters) used, taking into account the grouping bandwidth, the number of groupings and the overlap of the groupings. Typical grouping overlap is - 1 dB for groupings that are next to each other. A typical realization of 16 1.2% distance resolution groupings would be distance grouping filters that are 1 MHz wide, with a resultant requiring i.f. bandwidth of 8-9 MHz. This total bandwidth, as discussed above, would then be the wide grouping for ranging before narrowband range tracking, and then after meter acquisition. After target tracking initiation, the angular tracking demodulator error signal will continue to control the firing loop rebar angular velocities, and output signals proportional to line-of-sight velocities in both planes are applied to the craft's autopilot for converging guidance to hit the target.

After meter acquisition and range tracking with narrow arrays (n-1)/(n+1), the range tracking loop will continue to control the repetition frequency of oscillator 41 to keep the shock frequency f^ centered with the i.f. the band as the distances become shorter as the vessel approaches the target.

Claims (16)

1. High frequency, vessel-coupled, target detection search system with search and tracking modes and with rotary reflector antenna means (102) connected to receiving means (103), comprising a high frequency target sensor system (104) with search and tracking modes connected to the receiving means for detecting position and distance for the target and to provide target distance signals, and signals (K<5 e) representing the difference between the actual and desired line-of-sight velocity for angle change at the antenna relative to a first predetermined reference in a first direction, and signals (Kéa) representing the difference between the actual and desired line-of-sight velocity for angle change of the antenna with respect to the first predetermined direction in another direction perpendicular to the first direction, antenna drive means (150, 120) which are connected to the rotator-flexor antenna means and connected to the target sensor system means for positioning the antenna in the first and second directions according to the target sensor system signals, as well as antenna control means (106, 107, 109) which are connected to the antenna drive means, characterized in that the target sensor system further provides signals /\ ^ ei which represent the desired line of sight angle for the antenna in relation to the first predetermined reference in the first direction, and signals ^ $ az which represent the desired line of sight for the antenna in relation to the first predetermined reference in the other direction, and includes first angle sweep means (152) connected to the antenna drive means for providing signals ( 0 ) representative of the antenna driver angle in the first direction relative to the first predetermined reference, second angle sensor means (212) connected to the antenna driver means for providing signals (^ ) representing the antenna driver angle in the other direction with respect to the first predetermined reference, first vessel velocity follower means (170) which are connected to the vessel to provide signals (ép) representative of the angular velocity change of the vessel in a third direction relative to another predetermined reference, second vessel speed sensor means (180) connected to the vessel to provide signals (Or) representing the angular velocity change of the vessel in a fourth direction perpendicular to the third direction relative to the predetermined reference, third vessel speed sensor means (195) connected to the vessel to provide signals (éy) representing the angular velocity change of the vessel in a fifth direction perpendicular to the third and fourth directions, related to the second predetermined reference, and in that the antenna control means connected to the antenna drive means are aligned to receive the signals K£e, Kfa, ep, Ør, ey, ' ^ daz °9 ^ del ^or ^ produce signals in the tracking mode for controlling the angular rate of change X? in the first direction mainly according to the formula: and also to provide signals in the tracking mode for controlling the angular velocity change of the antenna drivers Yi the other direction mainly according to the formula: and to provide search mode signals for controlling the antenna drive means angular velocity change /3 in the first direction substantially according to the formula: and to further provide search mode signals for controlling the antenna drive means angular velocity change ^ in the other direction substantially according to the formula: 2. System as stated in claim 1, characterized in that it further comprises: transmitter oscillator means (41) connected to the antenna means (102) for irradiating the target and background by means of the directive antenna means, and also connected to receiver means (103, 44) for thereby providing shock frequency signal in the presence of the irradiated target or background, transmitter oscillator drivers (42, 43) having input terminals and output terminals, the output terminals being connected to the transmitter oscillator to provide transmitter oscillator drive signals at the output terminals in response to the amplitude of signals which are impressed on the input terminals, the frequency of the transmitted oscillator signals being responsive to the transmitter oscillator drive signals, a plurality of area grouping means (82) connected to receive the shock frequency signal, each of the area groupings being responsive to irradiated objects in substantially lateral predetermined areas and to provide output signals from a grouping corresponding to the area of the irradiated target, and in addition to provide signals from groupings corresponding to areas in the vicinity of the target area, differential means (94) with input terminals connected to receive the signals corresponding to the areas in the vicinity of the target to provide a signal during tracking mode representing the difference in amplitude between the adjacent range grouping signals and the oscillator drive means, frequency discriminator means (88) with inputs connected to receive the pulse frequency signal and with outputs connected to the transmitter oscillator drivers for providing, during tracking mode, background range tracking signals to the transmitter drivers by outputting the pulse frequency from a predetermined frequency value, as well range search generator means (97) reversibly connected to the transmitter oscillator drive means for providing range search signals during the search mode. 3. System as stated in one of the preceding claims, characterized in that the first direction is the antenna's elevation direction, and the second direction is the antenna's azimuth direction, and that the antenna's drive means comprise: an elevation servo motor (61) which is connected to the rotating reflector antenna (102 ) for positioning the antenna in the elevation direction, and an azimuth servo motor (60) connected to the rotary reflector antenna means for positioning the antenna in the azimuth direction, first speed sensor means (151) connected to antenna drive means for providing signals (/3) representing the angular velocity of the antenna drivers with respect to change in elevation direction, second speed sensor means (211) connected to the antenna drivers for providing signals representing the angular velocity of the antenna drivers with respect to change in azimuth direction, first tachometer summing amplifier means (179) having internal means responsive to the antenna control means signals and the first speed sensor organ nals, and is connected to the elevation servo motor means, for comparing the antenna control means signals and the first speed sensor means signals, to produce an error signal equal to the difference between the input signals for controlling the elevation servo motor, and other tachometer summing amplifier means (208) having means responsive to the antenna control means signals and to the first speed sensor means signals, and which is connected to the azimuth servo motor means for comparing the antenna control means signals and the second speed sensor means signals for providing an error signal equal to the difference between the inputs for controlling the azimuth servo motor means. 4. System as stated in claim 3, characterized in that the first speed sensor means comprise a tachometer (151), that the other speed sensor means comprise a tachometer (211 ), that the first angle sensor means comprises a variable resistor (152) which is connected to the elevation servo motor (150) with an output signal (1) proportional to the angle of the elevation servo motor, and that the second angle sensor comprises a variable resistor (212) connected to the azimuth servomotor (210) and has an output representing the angle of the azimuth servomotor. 5. System as stated in one of the preceding claims, characterized in that the third, fourth and fifth directions correspond to respectively pitch direction, roll direction and turning direction for the vessel, and that the first vessel speed sensor means comprises a pitch rate gyroscope (170), the second vessel speed sensing means comprises a roll rate gyroscope (180), and the third vessel speed sensor means comprises a yaw rate gyroscope (195). 6. System as stated in one of the preceding claims, characterized in that the antenna control means comprise: first multiplier means (184) connected to another vessel speed sensor means (180) and to the second angle sensor means (212) for multiplying the second speed signal by the other angle signal, and to provide an output signal representing said, a first vessel speed amplifier (172) connected to the first vessel speed sensor (170) and to the first multiplier (184) for subtracting the first multiplier output signal from the first speed signal, and to provide an output signal representing said, a first speed summing amplifier (154) which can be reversed in response to the signal K £e and is connected to the first vessel speed amplifier for subtracting therefrom the output signal from the first vessel speed amplifier, and multiplying the difference by 0.5, and to provide an output signal representing mentioned, first integrator means (175) connected to the first vessel speed amplifier for integrating the output signal from the first vessel speed amplifier, and for providing an output signal representing the same, a first angle amplifier (162) which is adapted to receive the signal A & ei and is connected to the first integrator and to the first angle sensor means for multiplying the output signal from the first angle sensor means by two and subtracting the multiplication result from the difference between the signal /\ and the first integrator output signal, to further multiply the subtraction result by a constant K, and to further provide an output signal therefrom which is reversibly connected to the first rate summing amplifier, second multiplier means (186) which are connected to the second vessel speed sensor means (180) and to the first angle sensor means (152) for multiplying the second speed signal by the first angle signal, and to provide an output signal representing the same, a second vessel speed amplifier (197) connected to the third vessel speed sensor and to the second multiplier (186) for adding the second multiplier's output signal from the third speed signal, and to provide an output signal representing said, a second velocity summing amplifier (215) reversibly responsive to the signal K £-a and connected to the second vessel velocity amplifier for subtracting therefrom outputs from the second vessel velocity amplifier, and for multiplying the difference by 0.5, and for providing an output signal representing same, second integrator means (200) connected to the second vessel speed amplifier for integrating the output signal from the second vessel speed amplifier and for providing an output signal representing the same, and another angle amplifier (219) adapted to receive the search command signal ^del' 0< 3 which is connected to the second integrator and to the second angle sensor means, for multiplying the second angle sensor means output signal by two and subtracting the multiplication result from the difference between the signal A<fiaz and the output signal from the first .integrator, to further multiply the subtraction result by the constant K , and furthermore to provide an output signal therefrom which is reversibly connected to the second speed summing amplifier. 7. System as stated in claim 6, characterized in that it further comprises: first switching means (157) with a first internal means which is connected to the first angle amplifier (162), other internal means which are arranged to receive the signal KÉ~ e, and external means connected to the first speed amplifier (154) for reversibly connecting the first or second internal means to the external means from the first switching means, second switching means (216) with first internal means connected to the second angle amplifier (219), other internal means which are arranged to to receive the signal K £ a , and output means connected to the second speed amplifier (215) for reversibly connecting the first or second input means to the output means from the second switch means, and acquisition detector means (155) responsive to target range signals and connected to the first and second switching means for comparing the target range signals in relation to another predetermined threshold signal, and for influencing the first and second b rider organs in the presence of a signal greater than the second threshold signal. 8. System as specified in claim 2 and one of claims 3-7, characterized in that it further comprises: third switch means (91) with first internal means connected to frequency discriminator means (88), second internal means which are connected to the difference means (94), and external means for reversibly connecting the first or second internal means to the external means of the third switching means, fourth switching means (45) with first internal means connected to the area search generator (97), second internal means interlinked with the third switching means' external means (91), and external means connected to transmitter oscillator driving means ( 42, 43) for reversibly connecting the first and second inputs to the outputs of the fourth switch means, and threshold detector means (90) connected to the discriminator means for comparing the frequency discriminator signal with predetermined threshold signals, and for influencing the third and fourth switches in the presence of signals greater than the first threshold signal. 9. System as stated in claim 2 and one of claims 3-8, characterized in that it further comprises: fifth switch means (65) with first internal means connected to the search command generator (69) and second internal means connected to target sensor means (104), and external means connected with antenna driver means (42, 43) for switchably connecting the first or second input means to the output means of the fifth switch, and acquisition detector means (71) connected to receive target area grouping signals for comparison of target area grouping signals against another predetermined threshold signal, and to actuate the fifth switching means in the presence of a signal greater than the other threshold signals. 10. System as stated in claim 2 and one of claims 3-9, characterized in that the area grouping means comprise: a plurality of narrow band filters (81) with mainly close passbands and with internal means which are connected to receive the shock frequency signal, as well as external means for providing a plurality of output signals each indicative of a target in a corresponding area, a plurality of detector means (82) connected to the output means from the narrow band filters for detecting the amplitude of signals received from the narrow band filters and for producing a plurality of detected output signals, and multiplexer means (83) connected to the detector means for selecting one of the detected output signals which are representative of the presence of the target in the corresponding area and for obtaining signals which are representative of the same, and also to select detected output signals which represent areas in the vicinity of said target area. 11. System as stated in claim 10, characterized in that the detector means comprise diodes (82). 12. System as stated in claim 2 and one of claims 3-11, characterized in that the frequency discriminator means includes: limiter means (88) which react to the shock frequency signal, and discriminator circuit means (88) which react to the limiter means. 13. System as stated in claim 2 and one of claims 3 - 12, characterized in that it further comprises integrator means (92) which reversibly react to difference means (94) and to the frequency discriminator means (88), and includes external means which are reversibly connected to the transmitter oscillator drive means (42, 43). 14. System as stated in one of the preceding claims, characterized in that it includes means for providing the target area signals as an automatic gain control signal to the receiver means. 15. System as stated in one of the preceding claims, characterized in that the angle tracking demodulators comprise an azimuth angle demodulator that responds to the target area grouping signal for the production of azimuth angle error signals (K<f"a), and an elevation angle demodulator (68) that responds to the target area grouping signal -nalet for obtaining elevation angle error signals (Kte), and that the antenna drive means comprise elevation and azimuth servo motors (60, 61) connected to the antenna and responding to respectively the elevation and azimuth demodulator. 16. System as set forth in claim 2 and one of claims 3 - 15, characterized in that the transmitter oscillator drive means comprise a voltage-controlled oscillator (43) which reversibly reacts to the difference means (94) and to the area search generator means (94), as well as signal linearization means (42) with an input connected to the voltage-controlled oscillator means and an output connected to the transmitter oscillator means (41).