DE2642022A1 - REPLYERS, IN PARTICULAR IMPULSE REPLIES - Google Patents

Description

Alfa-Laval Company Limited, Great West Road, Brentford, Middlesex, England

Responder _f in particular impulse responder

The invention is concerned with answerers, in particular when requested by an interrogating transceiver can transmit coded data, with a monitoring device within the scope of the invention which contains such a responder. A responder of the type mentioned is used for vehicle identification, in the remote retrieval of information relating to animals as well as in the context of safety precautions used.

Responders are known from a large number of applications in which the im A response signal is generated inside. Such responders often have the disadvantage that they are a relatively large energy source for generating the response signal require. In connection with vehicle identification, it is also known to provide reflective strips, which are read by scanning so that the driven vehicle can be identified. Such systems

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usually require a relatively large area for the encoded reflective strips, which can therefore not be used in certain applications.

Attempts have also been made to supply the information-carrying signal to the power supply for the responder to use. This has the disadvantage that the signal that is sent to the responder for putting it into operation must be, must carry a relatively high amount of energy. This in turn causes difficulties in particular when it comes to high-frequency carrier signals, because the amounts of energy to be transmitted are so large can be that they can cause injuries to human or animal organisms if they get into the carrier signal beam. This is a problem that some countries are trying to address by adding the Energy that can be transmitted at specific frequencies is limited, or at least suggestions are made made to limit energy.

The invention is therefore based on the object of a responder to create, which does not suffer from the disadvantages mentioned.

According to the invention it is provided that a responder, for example in the form of an impulse responder, is a reflex element contains whose reflection or transmission property for an electromagnetic signal from a first Frequency can be changed, and has a device with which a coded signal to the reflective element can be emitted, so that the reflective element when irradiated with energy of said frequency energy of the same Frequency, but modulated, reflected or transmitted according to the coded signal, and with a second device

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processing of electromagnetic energy of a second frequency different from the first frequency for energy supply responds to the responder.

According to the invention, therefore, the properties of a reflecting or transmitting element changed, for which less energy is likely required would be than to generate a response signal. Preferably the device with which a coded signal will be delivered to the reflective element comprises a signal source of the third frequency and a modulation device for the signal of the first frequency with signals from the third frequency. Of course, the second and third frequencies can also be the same.

The wavelength of the electromagnetic signal of the first frequency can be in the visible range, in which case an entire frequency band is reflected or transmitted. The reflective element with an electrically variable reflective top Transfer coefficients can be a liquid crystal cell be.

To avoid problems caused by: air turbulence, haze, Fog, etc. can occur when working with visible radiation, but preferably electromagnetic radiation Signal of the first frequency can be an RF signal of short wavelength, for example a microwave signal.

When using a microwave signal for irradiation of the responder, the reflective element with a variable reflection coefficient can expediently be an antenna or consist of several antennas whose dimensions are comparable to the wavelength of the irradiating microwave signal are. This antenna element is connected to a device comprising, for example, a diode, whose

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Impedance can be controlled electrically.

Direct current to operate the responder is obtained from a device based on electromagnetic Responsive to energy at a second frequency, the second frequency being a different frequency than the first frequency. When using a microwave signal, for example, this device can be a solar cell in which If an entire frequency band is used, but it is advantageous to have the necessary power supply through to ensure electromagnetic induction that can take place in the coils of a transformer.

A synchronization signal can be transmitted to or from the responder in order to thereby to support the detection of the coded signal. If in the responder the necessary for operation Electricity is generated by induction, the induced signal itself can serve as a synchronization signal.

The responder in the form of a pulse transmitter and the interrogation device are movable relative to one another, whereby the interrogator can be portable, but a stationary version of the interrogator brings advantages.

For a better understanding of the invention, exemplary embodiments of the invention are described below with reference to the accompanying drawings. Show in detail:

1 shows a block diagram of a detection circuit in which a responder according to the invention is realized;

Fig. 2 is a further detailed block diagram of the responder of Fig. 1; and

FIG. 3 is a detailed block diagram of the interrogator from FIG. 1.

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The assemblies forming the responder are shown in FIG. 1 to the right of the dividing line 10, and to the left of the vertical 10 is shown the interrogation device. There are two signals from the interrogator to the responder transfer. The first signal comes from a signal power transmitter 12 and is fed by an induction loop 14 received in the mobile responder. The transferred Signal contains enough energy so that it can be received and rectified in a rectifier and Stabilizer 16 the average DC demand the other components of the responder can cover. It has been found that a signal of 10 kHz is used for energy transmission suitable is. The signal from the induction loop 14 is sent directly to a coding signal generator 18 which generates a code representative of the data to be transmitted to the stationary interrogator is. The coding signal is fed to a reflective element 20, whose reflection coefficient is changed by the impressed coded signal.

A second transmitter 22 in the interrogator can do that Irradiate reflective element 20 with radiation of a predetermined wavelength and a receiver 24 is on that Radiation matched, which is received after the reflection by the reflective element 20 of the same wavelength. The receiver picks up a synchronization signal from the power transmitter 12, thereby decoding the received, modulated, reflected radiation amplitude is supported.

In the case of a system working in the visible, the reflective element 20 in the responder can be a liquid crystal cell. A liquid crystal cell can, for example, between the radiation received by the transmitter 22 and a mirror are arranged so that the amount of light reflected from

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depends on the permeability of the liquid crystal. Alternatively, if you work with polarized light, you can the modulation device be created so that it changes the degree of polarization of the light passing through.

Note that the responder does not send a signal itself transmits, but only modifies incoming radiation. Hence it would be without any external lighting or irradiation the responder will not be visible.

The DC power supply for operating the coding signal generator 18 is above in connection with the use an induction loop has been explained; however, it is understood as an alternative that instead of the induction loop a solar cell can also be provided in the responder.

Although responder according to the invention with wavelengths can work from the visible spectral range, there are numerous possible applications in which in the visible operating responders are unsuitable for use in air, in which case the radiation path of the interrogation beam would likely be significantly attenuated by haze, mist, steam, air turbulence and the like; further There are applications in which the transmitter, receiver or reflective element is likely to have deposited Suspended matter from the air or other sources can be covered. Furthermore, it is occasionally necessary that the responder remains invisible, either for reasons of secrecy in security systems or because the responder is inserted under the skin or in other areas of an animal inaccessible to light. If answerer To be provided for vehicles, it may also be necessary to place the responder under an impermeable

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To attach protective skin to avoid mechanical damage.

The reflective element 20 can therefore also be designed in such a way that that it can work with frequencies from the microwave range, in particular in the frequency range of 1GHz and more up to the ultra-red spectral range. A microwave reflective element can be designed to work either by changing the impedance with which a microwave antenna is connected, for example a microwave diode, or that the microwave signal is mixed with a modulation signal of a third frequency, which with the responder code, this mixing the non-linear properties of a semiconductor diode is attributable. In this case, the reflective element is made by a combination of the microwave antenna with formed of the semiconductor diode, the latter being used to change the reflection coefficient of the reflective element. The degree of absorption or reflection for radiation hitting the antenna is changed according to the degree with which the antenna terminating impedance, formed by the microwave diode, is matched or detuned.

An advantage of being able to use it with frequencies in the microwave range proposed circuit is that they are realized by using circuit components that have already been developed in conjunction with other applications. For example, the microwave transmitter and receivers already commercially available as a simple intrusion alarm device that works with Doppler radar works, which can be purchased relatively inexpensively. The coding signal generator is similar in the answerer already developed and in the trade for

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Vehicle identification devices available.

In the system described, the one for the power supply loop used frequency either directly or as a quadruple or as a divider in the responder, "to synchronize the receiver and transmitter sections of the responder system. That way a significantly improved detector efficiency is obtained, and also the signal-to-noise ratio is greatly improved. Note, however, that it is not it is essential that the frequency of the power supply loop to synchronize the responder with the stationary receiver is used, because it would be alternatively also possible in the responder a Free-running oscillator to be built in, on whose frequency the receiver code detector with a simple usual phase lock loop is matched.

Preferably, the modulating element should not be controlled by a device that emits an output pulse, whose length is equal to the code bit, but should rather be controlled by a DC signal, that indicates whether the code bed is a one or a zero. The advantage of using a modulating direct current in the microwave diode is that the receiver code detector very precisely the start and stop times of each Determine the code pulse from the given ratios can that between

a) the number of modulation cycles per bit (multiple or integer divisor),

b) the form of modulation (phase shift, frequency shift, Amplitude modulation or combinations thereof) and

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c) the phase of the modulating signal to which the bit edge can be tied

exist. In order to reduce the total power requirement with inductive power supply of the responder, is it is possible for the responder to provide an energy storage device in the form of a capacitor, for example which the energy is increasingly collected, but which discharges faster, with shocks being coded Signals are emitted to the reflective element with variable reflection or transmission coefficients. In in such a system it is necessary that the capacitor can continue to charge sufficiently so that several continuous cycles of code pulses can be transmitted during each discharge.

To transfer the information between the responder and to speed up the interrogator, it is possible that the variable reflective element on at the same time modulated in different ways at different frequencies, each of which may correspond to a binary bit. For example, eight modulation frequencies can be used, which are conveniently connected to the main synchronization frequency of the responder system are linked to an eight-bit word of digital coding simultaneously to the receiver section of the interrogator. A number of eight-bit words, which are represented in sequence using the method mentioned, are used to transmit a large responder codes in a relatively quick manner. By modifying this technique, the above-mentioned Modulation frequencies can be used sequentially for a number of words. For example, the first word can start with the frequency F1, the second word with the frequency F2, and so on. All words can be bit sequential

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and are transmitted word-parallel.

Finally, it was assumed above that the code signal generator 18 transmits a predetermined code; alternatively, it is also possible here for the code signal generator 18 to be connected to sensors. So that can the transmitted code or the code bit rate or the size of the modulation frequency for the variable Reflective element or the degree of modulation can be changed as a function of sensed parameters. Such a thing Telemetry is used, for example, in the monitoring of skin temperatures of animals, with the sensors Thermistors or other temperature-sensitive components are. In this latter embodiment it is not essential that the code be changed in accordance with the sensed parameter because, for example the code can be divided into two sections, the first fixed and identifying the animal and the the second is variable and represents the skin temperature.

The code can be a function of the power supply used frequency or a frequency-dependent element seiri, which can be built in so that the answer encoder only responds to the query if it is at a predetermined frequency or a predetermined group is supplied by frequencies.

The preferred embodiment of the responder is shown in FIG. in which the blocks shown in Fig. 1 are framed by dashed lines. Based on the explanations given above it does not seem necessary to give a detailed description of the respondent because of its function is understandable in detail. However, the following should also be communicated:

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As mentioned above, the responder is a so-called passive responder and is preferably assisted Electromagnetic induction powered. The rectifier and stabilizer 16 includes one Rectifier 161 and, if desired, an energy store 162. The energy store is expediently a capacitor, however, it could also be a rechargeable battery or some other suitable element such as can store electrochemical energy or charge in connection with a solar cell. This facility is partial passive, partly active, and particularly useful when the responder is used to identify or monitor animals that are practically permanently in the open air.

The rectifier and stabilizer 16 can be connected to the rest Parts of the responder output power directly or a switch 171 can be interposed. The desk is controlled by a frequency-dependent device 172, so that the remaining parts of the responder Electricity is only supplied when a current-giving signal of the correct frequency is received. this can be used to advantage because the interrogator described in detail below with a Presence detector is equipped. An alarm signal can be generated by the interrogator if it is present detects a moving object, but a code is not reflected from the responder, either because there is no responder or the responder to the selected and correct energy supply frequency does not respond and is therefore not supplied with power and therefore there is no modulation of the query signal.

The code signal generator 18 contains a code memory 181 and a transmitter. The transmitter is formed by a commercially available universal asynchronous transmitter, the therefore need not be explained in detail. Suffice it to say that the sender has a word in parallel from the

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Fetches out memory 181 and feeds it to reflective element 20 as a series of serial bits.

The code memory 181 can be any memory, for example a read-only memory, or, as shown, a programmable read-only memory (PROM). In the case of a programmable read-only memory, the memory can preferably be designed so that it can store codes over long periods of time and requires little power. This can be achieved by using NMOS technology.

The memory 181 is first entered by entering a code programmed that the code or codes in the memory 181 enrolls. This is usually done by the manufacturer so that the code entry is not part of the responder needs to form. The code generated at the output can be checked by using either a sensing device 176 or a presettable controller 177 or both. The sensing logic 176 can be used to Modification of the code produced by the memory 181 can be used, accordingly with any parameter details that are transmitted to the interrogator should. Such a parameter could be used in animal surveillance for example the temperature of the carcass. Alternatively, the means 176 for specifying the frequency with which the responder was supplied with voltage. This can be done with the help of the presettable control 177, which, as shown, is connected to the frequency-dependent device 172.

In certain cases, therefore, a memory will not be necessary. What is needed is a facility that

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can distinguish between several different frequencies and the reflective element 20 according to each frequency modulated. The frequency with which the power supply is ensured can itself act as a code. One an additional alternative is that instead of the device 176 which changes the code, the frequency of the modulating signal is changed to the third frequency, which is fed to the reflective element 20. Differences of Modulation frequency could then with the interrogation device Can be determined with the help of phase coupling techniques.

As Fig. 2 shows, is the speed with which Bits of the code are delivered to the reflective element 20, fixed to the power supply frequency of 10 kHz here. This is done with the aid of a frequency multiplier or divider 179. The reflective element 20 is activated by an alternating current signal is modulated by a frequency which is a multiple, a divisor, or even equal to the power supply frequency, i.e. the AC signal is passed through the Code transmitted from memory 181 is modulated. The alternating current signal can either be sent to the reflective element 20 can be delivered in single bursts according to the code or the phase of the AC signal can be adjusted accordingly the code can be changed, or the value of the frequency can be changed according to the code, or it can of course a combination of these possibilities can also be used. The coupling of the bit rate to the power supply frequency improves easy signal detection at the receiver, but such coupling is not essential because Similar effects can be achieved due to the phase coupling technique for a modulator frequency determined by the responder know what was referred to in the previous section.

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An interrogator for use with the responder shown in FIG. 2 will now be briefly described. How related As mentioned with Fig. 1, the interrogator includes a power transmitter 12 operating at 10 KHz Interrogation signal transmitter 22, which in this case can be a microwave transmitter 22 operating at 10.6 GHz, and where furthermore, a receiver 24 is framed by dashed lines in FIG. 3. The receiver 24 is at the power supply frequency synchronized. Because of the low frequency induction system which is used to advantage, the responder must in the vicinity of the power supply loop, which is not a big deal with safety devices The problem is where the loop is near passageways or other openings that are used by people. is provided; in the case of animal surveillance, during which the animal or the part wearing the answer carrier passes through a portal is guided, this can contain the power supply loop.

The receiver 24 contains a microwave carrier signal mixer 241, with which the transmitter 22 forms a part a commercially available burglar alarm device, so that a description is omitted in detail can be. The output from mixer 241 has a third frequency and is amplified and then sent to a demodulator fed, which removes the code.

The output from the mixer receiver 241 will also be fed to a presence detector as already mentioned. The rest of the receiver will be obtained from a store universal asynchronous receiver formed, so that here too a detailed description is dispensed with can be.

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The output from the receiver 24 is fed to a system controller 30 which is used to record details of the Animals or from accesses to prohibited areas of a system to be monitored.

It goes without saying that the responder is not limited to the animal surveillance explained above or in the context of security tasks, but also to other, general ones Purposes can be made usable.

This is how the responder discussed above becomes present used with particular advantage for animal monitoring, for example to identify a cow if she enters a milking room or stall, or if the cow is to be fed a putter ration, which was calculated on the basis of the past or expected milk yield. The answerer can be placed under the animal's skin or on the animal's ear or around its neck to be ordered. In the latter two cases, the responder is appropriately protected by that it is installed in a transparent housing for electromagnetic signals of the first frequency.

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Claims (1)

Expectations 1. ) Responder with a reflective element (20), whose reflection or transmission property for an electromagnetic signal can be varied from a first frequency, with a code signal generator (18) which emits a coded signal to the reflective element, so that the element (20) when irradiated with the signal of the first frequency, the signal with the same frequency, but modulates, reflects or transmits according to the coded signal, as well as with a power supply device for the responder, characterized in that the power supply device (14) on electromagnetic radiation from a responds to the second frequency, which is different from the first frequency. 2. answering device according to claim 1, characterized in that that the power supply device has an electromagnetic element responsive to the second frequency. 3. Responder according to claim 2, characterized in that the power supply device is a rectifier (16). 4. Responder according to claim 1, characterized in that the power supply device is a light-sensitive Facility owns. 5. Responder according to one of the preceding claims, wherein the code signal generator has a signal source, which generates signals of a third frequency or a group of frequencies whose frequency differs from the first Frequency is different, and wherein a modulating means the signal of the first frequency with the signals modulated by a third frequency, characterized in that a phase shift coupling for modulating the signal of the first frequency is provided with bumping the signal of the second frequency. 6. Responder according to claim 5, characterized in that the signals of the third frequency from the electromagnetic Energy can be derived, which has the second frequency. 7. Responder according to one of the preceding claims, characterized in that a frequency-dependent component controls the operation of the responder as a function of the second frequency. 8. Responder according to one of the preceding claims, wherein a memory for coded information and a modifying means for the code are provided in the memory, characterized in that the modifying means (176) on electromagnetic energy from the second frequency responds and modifies the code according to the second frequency. 9. Responder according to one of the preceding claims, characterized in that the first frequency is in the microwave range and the second frequency is outside the microwave range. 709814/0684 -ye-- 0O. Responder according to one of the preceding claims in a monitoring device, with a transmission device for the signals of the first frequency, which from the
Responder is arranged remotely, characterized in that a power transmitter (12) is provided which the
Transmits signals of the second frequency to the responder. 11. Responder according to claim 10, characterized in that in that a device responsive to the reflected signals of the first frequency is provided, which means a signal that indicates the presence of a non-silent object in the field of transmitted signals. 12. Responder according to claim 11, characterized in that the device for generating the presence signal
the operation of the signal source for the delivery of signals from
second frequency controls. 7098U / 0684