Arrangement for the Remote Transmission of Information for the Remote Guidance of Vehicles Which Are Subject to Severe Acceleration

The present invention relates to an arrangement for the remote transmission of information, particularly for systems for the remote guidance of vehicles.

Present day remote transmission arrangements which enable information to be transmitted to a vehicle moving at high speed which is subject to severe acceleration may be divided into two categories. In a first category are those arrangements which comprise a transmitter and a direct-reception receiver attached to the vehicle which the information is transmitted, the transmitter generating a wave which is subject to all or nothing modulation to produce a coding representing the information to be transmitted to the vehicle. In a second category are those arrangements which similarly comprise a transmitter and a heterodyne receiver, the transmitter generating an amplitude, phase or frequency modulated wave, the modulation signal in each case representing the transmitted information.

Arrangements of the two foregoing kinds have, respectively, the disadvantages that they lack selectivity, have a high noise factor, are highly sensitive to jamming and interference, and that the level of the detected signal is attenuated by a factor proportional to the fourth power of the distance between the transmitter and receiver, in the case of arrangements in the first category, and the disadvantages that they are sensitive to the Doppler effect, that the local oscillator in the heterodyne receiver is sensitive to acceleration and vibration, and that the oscillator circuits are complicated by the addition of frequency controlling loops, in the case of arrangements in the second category.

One object of the present invention is to provide an arrangement for the remote transmission of information which is virtually insensitive to the Doppler effect and to acceleration and vibration.

Another object of the present invention is to provide an arrangement for the remote transmission of information whose sensitivity to jamming and interference is low and which has a low noise factor.

Another object of the present invention is to provide an arrangement for the remote transmission of information in which the receiver on board the vehicle to be supplied with information is small in size and highly reliable, as well as being inexpensive to produce, because of its simple construction.

The arrangement according to the invention for the remote transmission of information comprises means for transmitting information-carrying electromagnetic signals and means for receiving the said signals, the said transmitting means further including a first source which enables a first electromagnetic signal of a predetermined frequency F1 to be generated, and a second source which enables a second electromagnetic signal of a predetermined frequency F2, different from F1, to be generated, the said receiving means including a mixing device which enables an electromagnetic signal to be generated whose frequency F3 is equal to the difference between the frequencies of the said first and second electromagnetic signal, and means for processing the electromagnetic signal of frequency F3 connected to the mixing device.

Such arrangements may be used in particular for the remote guidance of vehicles moving at high speed which are subject to very severe acceleration, such as aircraft or guided missiles, and for the transmission of information to such vehicles.

Other features of the invention will be apparent from the following description and the accompanying drawings, in which:

FIG. 1 is a general diagram of an arrangement for the remote transmission of information on which the part marked A represents the means for transmitting electromagnetic signals and the part marked B is attached to the vehicle and represents the means for receiving these signals.

FIG. 2 shows a particular embodiment of the transmitting means indicated in FIG. 1,

FIG. 3 shows another particular embodiment of the transmitting means indicated in FIG. 1,

FIG. 4 shows a particular embodiment of the receiving means indicated in FIG. 1,

FIGS. 5 and 6 show a particular embodiment of the antenna of the receiving means.

In the drawings the various items are not shown in their correct relative size and proportions to assist in overall comprehension.

In FIG. 1, the arrangement for the remote transmission of information to which the invention relates comprises means A for transmitting electromagnetic information-carrying signals, and means B for receiving these signal, i.e. a receiver. The transmitting means includes a first source 1 which enables a first electromagnetic signal of a predetermined frequency F1 to be generated in operation, and a second source 2 which enables a second electromagnetic signal of frequency F2 to be generated in operation. The two sources 1 and 2 are connected to a transmitting antenna 4. At least one of the two signals of frequencies F1 and F2 carries the information to be transmitted in the form of amplitude, phase or frequency modulation, the other signal being, for the receiver, a frequency translation signal. The receiving means comprise a receiving antenna 5 which is connected to a mixing device 6 which enables an electromagnetic signal to be generated whose frequency F3 is equal to the difference between the frequencies of the first and second electromagnetic signals F1 and F2. Means 7 for processing the electromagnetic signal of frequency F3 are connected to the mixing device 6. In operation, the electromagnetic signals of frequencies F1 and F2 are transmitted simultaneously from the transmitting means A and they are mixed and detected in the receiving means B attached to the vehicle. The information is supplied from the output S of the means 7 for processing the signal. In particular, the transmission of the electromagnetic signals F1 and F2 from one and the same point in relation to the vehicle to be supplied with information makes it possible to achieve insensitivity to the Doppler effect which arises from the relative speed of the vehicle and the transmitting means, by virtue of the virtually identical shifts in the frequencies F1 and F2 which occur as the vehicle moves. The simplicity of the receiving means, which is due to fact that they do not include a local oscillator, makes it possible to prevent acceleration from having any effect on the reception of the information and enables the subject of the invention to be used on guided missiles subject to accelerations which may be as much as 5,000 times the acceleration imparted by gravity.

FIG. 2 shows a particular embodiment of the transmitting means A. In this Figure, the first and second sources are formed by a first oscillator 10 which supplies, in operation, a signal of frequency F2-F1, a phase loop 12, and a modulating device 11 which is connected between the oscillator 10 and the input 120 of the phase loop 12. A second oscillator 13 has a output 130 which supplies a signal of frequency F1 to an input 121 of the phase loop 12. The phase loop 12 has an output 122 which emits the signal of frequency F2. A transmitting antenna 14 has a first input 141 connected to the output terminal 130 of oscillator 13 and a second input 142 connected to the output terminal 122 of the phase loop 12. In operation, the transmitting antenna 14 is fed with the signals of frequency F1 and the signals of frequency F2. The phase loop 12 includes a phase detector 123 having a first and second input 1231 and 1232 respectively and an output 1233, a mixing circuit 124 which has a first and second input 1241 and 1242 respectively and an output 1243, and a voltage-controlled variable oscillator 125 having an input 1251 and an output 1252. The output 1252 of the oscillator 125 is connected to the input 1242 of the mixing circuit and to the output 122 of the phase loop 12 which supplies the signal of frequency F2. The connection between output 1252 of oscillator 125 and the input 1242 of mixer 124 takes place via a matched coupler 400. The connection between output 130 of oscillator 13 and the input 1241 of mixer 124 takes place via a matched coupler 500. In operation, the phase discriminator 123 supplies a control voltage to the voltage-controlled variable oscillator 125. Oscillator 125 emits a corresponding signal of frequency F2. The mixing circuit 124 supplies a signal of frequency F2-F1 to the phase discriminator 123. Amplifiers allow the gain of the system to be adjusted.

FIG. 3 shows another embodiment of the transmitting means A. In this embodiment, the first and second sources are formed by an oscillator 20 which has an output 200 which supplies a signal of frequency F0=1/2(F2+F1), by a 0, .pi. modulator 21 which has a first input 211 connected to the output 200 of the oscillator 20, a second input 212 and an output 213. A modulating device 22 has an output 222 connected to the said second input 212 of the modulator 21 and an input 221. An oscillator 23 has an output 231 which in operation supplies a signal of frequency F2-F1/2. The output 231 of oscillator 23 is connected to the input 221 of the modulating device 22. A transmitting antenna 24 is connected to the output 213 of the 0, .pi. modulator 21. In operation, the 0, .pi. modulator supplies the transmitting antenna 24 with information-carrying signals whose frequencies F1 and F2 are respectively equal to F1=F0-(F3/2) and F2=F0+ (F3/2).

FIG. 4 shows an embodiment of the receiving means B. In this Figure, the receiving means B includes a receiving antenna 35 having an output terminal 351 connected to the input terminal 310 of non-linear conduction means 31. From their output terminal 311, the non-linear conduction means emit a signal whose frequency F3 is equal to the difference between frequencies F2 and F1. The non-linear conduction means 31 has its output 311 connected to the input of circuits 32 for processing the signal of frequency F3. The non-linear conduction means are, for example formed by a microwave diode 312 which is connected in parallel with the output channel of the receiving antenna and by biassing means 313 which supply a voltage for biassing the diode into its zone of non-linear conduction.

In a preferred embodiment of the subject of the invention, the output 351 of the receiving antenna is connected to the non-linear conduction means via a high-frequency amplifier 30. This embodiment dispenses with the need to use high-power transmitting means to transmit information over long distances. In effect, using an amplifier 30 having a gain G expressed in decibels makes it possible to achieve an overall gain of 2G for the signal of frequency F3=F2-F1 as a result of the amplification of both the signals of frequencies F1 and F2, and makes it possible to remedy the attenuation in the useful received power which is proportional to the fourth power of the distance between the transmitting means A and the receiving means B.

The circuits 32 for processing the signal of frequency F3 comprise, in series, a filter 320 for the intermediate frequency F2-F1, an amplifier 321, and circuits 322 for detecting the modulation of the signal of frequecny F3. To obtain a better match between the filter 320 and the mixing circuits, which are formed by a diode, a pre-amplifier 33 provides a connection between output 311 of the non-linear conduction means and the input of filter 320, the pre-amplifier enabling the filter to be matched as far as the diode noise is concerned.

So that the arrangement as a whole shall, in particular, be insensitive to vibration and acceleration when the vehicle is liable to subject the receiving means to accelerations of the order of 5,000 times that imparted by gravity, the receiving antenna 35 is, for example, formed as shown in FIGS. 5 and 6. In FIG. 5, the receiving antenna has, in a dense, cylindrical metal body 51 which is connected to the reference voltage for the arrangement, a slab of dielectric material 52. The thickness e of the dielectric slab is of the order of a fraction of the wavelength of the received signals. The dielectric slab 52 is, for example, secured to the metal body 51 by retaining rim 55. The dielectric slab 52 has on its exposed face a conductive sheet 53. The conductive sheet 53 is, for example, produced in the form of a metal deposit using the techniques employed for printed circuits and is in the shape of a circle having a diameter .phi..sub.2 of the order of approximately 15 mm which is equal to half the diameter .phi..sub.1 of the metal body 51. This sheet 53 is connected to the reference voltage for the arrangement through the dielectric 52 by a conductor 62 which is connected near the centre of the sheet at a point where the radioelectrical field is zero. A co-axial output cable 54 enables the signals of frequency F3 to be transmitted. In FIG. 5, the metal body 51 and the slab of dielectric material 52 respectively contain orifices 56 and 57 which provide a passage for a conductor 58 which connects the metal sheet 53 to the non-linear conduction means, which are formed by a diode 59. The diode 59 is housed in orifice 56 and is directly connected to the biassing means by the centre core of the co-axial cable 54. Capacitors 60 enable the high-frequency signals to be decoupled from the reference voltage for the arrangement. In cases where a high-frequency amplifier 30 is used, as shown in FIG. 4, the amplifier is, for example, formed by a high-frequency amplifying transistor 61 which is inserted in the cavity 56 in the metal body 51 between the metal sheet 53 and the diode 56 the transistor having a high frequency input connected to the metal sheet. Transistor 61 is likewise biassed from the centre core of the coaxial cable 54 as shown in FIG. 6.

This embodiment of the subject of the invention enables a remote transmission arrangement to be obtained which has a highly reliable, low-cost receiver.