NO810227L - SYSTEM FOR IDENTIFICATION OF OBJECTS AND PERSONS AND TO PROMISE INFORMATION - Google Patents

Description

The invention concerns a system which serves for the identification of objects and persons and for the dissemination of information and consists of a reading device and an information carrier (marking device) which is placed on the object to be identified, resp. at the location of the information depository, and radiate the electric reading signals arriving from the reading device back to the reading device via a radio field with a plurality of delayed echoes that represent the information content (the bit content).

Corresponding devices for the identification of objects

and persons have been treated in previous patent applications belonging to the applicants. Thus, in BRD patent application P 28 21 299.9 above all the marking device of such a device is described and in BRD patent application P 28 21 509.3 the reading device.

The invention is based on the task of providing instructions for a solution for a system of the type indicated at the outset, with which identification and information transmission that is secure against interference and forgery is provided in a simple way, and it is especially made possible to use such a system for securing and improving road traffic.

According to the invention, this task is solved in such a way that frequency, phase or amplitude modulated reading pulses are sent from the reading device to the information carrier and echo pulses are radiated back from this which represent the information content and have a delay time t = f. t_ (f = integer. number, x_, = the

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smallest transit time fraction common to all the echo pulses) which, with reference to the read pulse, does not fall below a minimum delay Tq = e . tb (e = whole number), and which in relation to noise reflections that are triggered by the reading pulses and arrive at the reading device at the same time, and which are written from more distant additional noise reflection sources, exhibit a previously given noise distance at the reading device due to the longer noise radio field determined by tq,

and that the echo pulses received by the reading device are demodulated in frequency, phase or amplitude demodulators depending on the type of signal and amplified and then via a time window link controlled by a beat preparation unit are passed on to subsequent deciphering links in such time intervals within which, conditional on tolerated echo travel times that are precisely determined in advance in the information carrier, echo pulses are expected back from information carriers to be read from a pre-given area in the room, and that

where, with the help of the interpretation links controlled by the beat processing unit, such a distribution of the successive echo signals at the minimum possible time intervals xInteresting echo signals at fixed bit locations that there is assigned to each of the possible echo pulses tv A. representing the information content, a fixed location that is suitable for simultaneous parallel reading from downstream interpretation devices.

Favorable designs and further developments of the invention are specified in the subclaims.

In the following, the invention will be elucidated in more detail with reference to exemplary embodiments shown in the drawing. Fig. 1 and 2 are respectively the block diagram for a device that works with PM pulses, and an associated pulse diagram. Fig. 3 is a block core for a further device which works with PM pulses, and

fig. 4 is the block diagram of a device that works with AM pulses.

In the block diagram of fig. 1, the reader LG is shown in detail. It is connected to an antenna 6 which via a radio field F is connected to an antenna 7 for the marking device 8 (KA). The reader LG contains in the transmission branch a generator 1 which produces the transmission frequency, an amplifier 2, a downstream phase modulator c|> and an attenuation element it which in the block diagram is summarized in a box 3, as well as a directional coupler 4 and a band-limiting filter 5 connected to the antenna 6. The amplifier 2 amplifies the signal so that the intended transmission power is available at the antenna 6. It also disconnects the post-connected phase modulator <j> from the generator 1. A fast monoflop 9 is connected to the phase modulator <f> which is triggered via a switch 13 by a signal Al, and with the help of which the phase reading pulse via the phase modulator <)> is impressed on the transmission frequency with e.g. 180° phase modulation. Via the attenuation link tt and the coupler 4 (e.g. a 10-dB coupler) which decouples the phase modulator $ from the antenna 6

and also increases the receiver noise figure by only approx. 0.5 dB, and via the band-limiting filter 5, the antenna 6 and the radio field F, the carrier oscillation with an imprinted reading pulse arrives at the marking device 8. The band-limiting filter 5 here serves to limit the bandwidth of the receiver noise and causes an improvement in the impact of the device noise.

The different walking time lines at the marking device

- surface wave propagation time lines which are placed on substrates of e.g. quartz or lithium niobate and has defined length and different strong attenuation - converts the phase pulse into a phase-pulse sequence which has minimum possible time intervals td which is precisely defined by the marking device, and which represents its information content. The purely passively delayed pulse sequence is radiated back via the radio field F and comes via the antenna 6 and the coupler 4 to a low-noise phase detector 10 in the receiving branch of the reading device LG. Another input to the phase detector 10 is connected to the generator 1. At the time of the return of the pulse sequence after the time t/q, which in addition to the basic running time of the marking device KA with e.g. 0.1 nsec precision also contains travel time components from the radio field and the reading device, the signal from the generator 1 is unmodulated and serves as the reference phase for the pulse sequence. The phase detector 10 is designed so that its phase sensitivity is always optimal, regardless of the absolute value of the phase of the reception signal. It consists, for example, of of two 90° mutually offset detectors with baseband addition coupling. IN

a broadband, low-noise and e.g. logarithmic amplifier 11 which follows the phase detector 10, the phase detector's useful signal is amplified to a sufficient level for the further processing.

Due to the high running time precision of the marking device which can be realized with existing technology, it is known with very high accuracy at which times after the sending of the transmission pulses the responses must occur at the latest from a pre-given, narrowly limited reading diameter, namely at the times Tq, t- ^, ......<T>x<=>^,TB'^vor To = e * TB ut,?jØre a minimum delay that the echo pulses exhibit in relation to the read pulse.

In this equation, e is an integer value, tb is a minimum transit time share that is common to all echo pulses. tb is therefore e.g. the distance between the individual response pulses, namely between Tq and t^, etc. (cf. fig. 2).

With the help of the time window, which is matched to the corresponding response pulses and produced with a very fast window switch 12, it is possible to exclude all such response pulses originating from marking devices outside the narrowly limited reading diameter of e.g. 3 m, and which therefore has too long a walking time. This ensures a sharply limited spatial resolution.

The window switch 12, which follows the amplifier 11, is followed by a distributor switch 20 by means of which the useful signals separated by the window switch 12 are distributed to the individual possible bit locations in step with the bit information. The distributor switch 20 contains e.g. a number of parallel individual switches, each followed by an integrator 10, II, 12 ... In (21) and possibly adjustable thresholds SO, Sl, S2 ... Sn (22). The integrators 10 ... In at the output from each individual bit space integrate over e.g. approximately 10 4 readings of the marking device (it corresponds at 65 bits of information content, a vehicle speed of 200 km/h, an area of influence of 3 m,!„ = 70 nsec andTn= 1400 nsec to

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8 . 10 possible readings). With the help of this signal integration, it is possible to improve the signal-to-noise ratio by more than 20 dB,

and also the noise safety against extraneous noise sources and against interference from nearby reading devices is increased by similar values. Via the adjustable thresholds 22, which make it possible to reduce the bit distance t„ and provide an additional opportunity to prevent the reading of adjacent marking devices, the bit content comes to an interpretation and information device 23 which controls the bit code, e.g. . 2 out of 5 code, in step with a fraction p/l of the reading frequency, and as with a flawlessly read code, it deciphers the overall bit information corresponding to the system task and passes it on.

The necessary precise and partly very fast control (e.g. less than 0.5 nsec switching time) of the phase modulator <J>, the window switch 12, the distributor switch 20 and the interpretation switch 23 takes place via a central flow control unit which is indicated simplified by T. This contains a quartz generator 17 whose frequency is matched

on t and<Tn>„, (the running time of the marking device). Its frequency

B WEEK.

is divided into two branches in which the frequency e.g. using fast divisors 16, 19 (division ratio 2/1 in the case shown)

can be brought in digital form. In one branch, an adjustable phase shifter 18 is also connected in front of the divider, with which it is possible to set the length t^ of the time window and thus the range of the reading. The output signals Al and A2 from the dividers 16 and 19 respectively form the control signals for the time window 12. The period of the signals is exactly matched to the very constant travel time difference Tg between the successive response pulses from the marking device KA. The time for the marking device is given in advance for the marking device's running time element so that the bit sequence fits exactly into the periodic

window grids for Al and A2 (Tq^ = e . Tg) ...

In order for there to be no mutual disturbance of read locations located close to each other, the same bits of the disturbed device must not always be hit by the read pulse from the disturbing device. This can be achieved with certainty by the individual read pulses following each other with a quasi-statistically varying period T_ JU. By e.g. 10 3 individual readings per bit, depending on the length of the quasi-statistical period, only a few of these readings are falsified by the reading pulse of the neighboring device. The subsequent integration in the integrators 21 over the high number of individual readings completely clears the occasionally occurring bit errors. With a noise signal 30 dB higher than the useful signal, approx. 100 readings sufficient in that respect.

The quasi-statistical variation in the read period is achieved by the fact that the read pulse from the signal Al in one branch of the quartz generator 17, instead of being produced with a fixed division factor of 1, is produced with a variable adjustable division ratio of a divider 15. This adjustment takes place with a correspondingly long, feedback shift register 14 which is shifted with the rate of the read pulse. The adjustable divider 15 is connected to the switch 13, which is connected to the fast monoflop 9. Since the running times of the divider 15 are temperature dependent, but the read pulse must occur in exact time relation to the signals Al and A2, the signal A3 from the divider 15 closes the switch 13, which passes the temporally exact trigger edge of the signal A2 on to the fast monoflop 9, and only briefly each time. The monoflop-9 thus produces the temporally exact short-term (e.g. 20 nsec) phase read pulse via the phase modulator

Fig. 3 shows a device for phase-modulated read pulses which has improved receiver noise figure, and which with respect to the principle structure corresponds to the device shown in fig. 1 and was described above. Therefore, only the coupling parts that differ from fig. 1, be described in more detail. Incidentally, reference should be made to the description of fig. 1. One difference lies in the fact that no permanent signal is sent out that gets a fast phase reading pulse emphasized, but slow (Gaussian) AM pulses are used

on e.g. 1.5 ysec which is emitted at the rate of the read frequency and shows the fast phase read pulse in the middle of the pulse. The AM pulse is then

already completely disconnected when the response pulses arrive at the reading device corresponding to a basic transit time Tq which is determined by the marking device's marking element. This makes it possible in the receiving branch to use a very low-noise, limiting receiving amplifier 29 directly on the transmission frequency, inserted between the coupler 4 and the phase demodulator 10.

The control for the AM modulation takes place in a simple way by

a further monoflop 27 is controlled via a further adjustable counter 28 which is likewise connected to one branch of the quartz oscillator 17 and connected to the shift register 14. The e.g. three-digit dividers 15, 28 with the adjustable division factor n resp. m is only changed synchronously in the first two digits by the shift register 14, while the lowest digits are fixed and so differently set that the monoflop 27, which is connected to an amplitude modulator arranged in front of the phase modulator <j> in the transmission branch of the reading device, is started a few cycles of the frequency Al earlier than the phase reading pulse and only goes back after a time which is measured so that together with pulse shaping operations a Gaussian pulse of suitable length is obtained. In this connection, the amplitude modulation takes place via a PIN switch 24 and a subsequent filter-amplifier combination 25, 26 which ensures that the AM spectrum does not exceed the band limits for the frequency band used, and that the transmission amplitude is switched off, e.g.

more than 80 dB when the response pulses from the marking device KA occur.

Fig. 4 shows an embodiment which is intended for amplitude modulated read pulses. In its basic structure, the connection corresponds to that shown in fig. 1. Only those features and functions that differ from those in fig. 1, will therefore be described, while otherwise reference is made to the above description of fig. 1.

In the device in fig. 4 you work with very short AM read pulses, e.g. in 20 nsec, as using the monoflop

9 is produced in an amplitude modulator 30 connected to the transmission branch of the reading device LG, as well as a keyed amplifier 31. Amplitude modulation takes place here in a similar way as in the device in fig. 2, namely via a PIN switch and a downstream amplifier. In the reader's receiving branch, a low-noise preamplifier 29 and an amplitude detector 32 are connected between the 10 dB coupler 4 and the window switch 12. The received pulse responses are amplified in the preamplifier 29, demodulated in the amplitude detector 32 and deciphered in the manner already described. The pulse control takes place here with the help of the beat preparation unit T, also as already described.

Claims (21)

1. System for identification of objects and persons and to dissemination of information, consisting of a reading device and an information carrier (marking device) which is placed on the object to be identified, resp. at the information depository, and which radiates the electromagnetic reading signals arriving from the reading device with a plurality of delayed echoes that represent the information content (bit content) back to the reading device via a radio field, characterized in that frequency, phase or amplitude modulated reading pulses are sent from the reading device to the information carrier and from there echo pulses that represent the information content are radiated back and has the delay time t = f. t_, (f = integer, t_ = a for x a o all echo pulses share the smallest travel time fraction), and which in relation to the read pulse does not fall below a minimum delay Tq = e .T g (e = whole number), while at the same time as the reader arriving disturbing reflections that are triggered by the reading pulse and originate from more distant noise reflection locations, due to it atT q certain longer noise radio fields exhibit a pre-given noise distance at the reading device, and that the echo pulses received by the reading device, depending on the type of signal, are demodulated in frequency, phase or amplitude demodulators and then amplified via a time window switch controlled by means of a clock preparation unit, is given further to subsequent deciphering links in such time intervals within which, conditional on tolerated echo travel times which are precisely given in advance in the information carrier, echo pulses are expected back from information carriers which. should be read, from et pre-given area in the room, as well as that the echo signals arriving in turn at minimal possible time intervals T g with the help of the decoding links controlled by the clock processing unit are in turn distributed to fixed bit locations in such a way that each of the possible echo pulses t representing the information content is assigned, a fixed place which is suitable for simultaneous parallel reading of downstream interpretation devices. 2. System as stated in claim 1, characterized in that the time window switch (12) is connected to a distributor switch (20) which is controlled chronologically by the beat processing unit (T), so that each individual echo pulse (bit) comes to a own integration link (21) (bit space) in accordance with its running time marking contained in the information carrier. 3. System as specified in claim 2, characterized in that the integration links (21) are sized with regard to time constant so that at a pre-given repetition frequency of the read pulses and a pre-given minimum dwell time for the information carrier in the area of influence of the reading device, an almost lossless summation of all per bit-space incident echo pulses. 4. System as specified in claim 1, 2 or 3, characterized in that the integration links (21) and a threshold switch (22) are connected afterwards which only forward such signals as useful echo pulses that exceed a predetermined noise distance from the reading device's own noise . 5. System as specified in one of claims 1-4, characterized in that the integration links (21) and possibly the threshold switches (22) are followed by interpretation devices (23). 6. System as stated in claim 5, characterized in that the deciphering device (23) is controlled by the beat preparation unit (T) in such a way that thereafter, at any time a previously given number p (p less than the number of possible reading pulses at a given residence time for the information carrier in the reading device area) of read pulses, a code check is made of the bit pattern present at the individual bit positions, and the bit pattern in the event of a positive result of the check is passed on to the deciphering link (23). 7. System as stated in one of the claims 1-6, characterized in that the clock preparation unit (T) contains a clock generator (17) whose frequency is supplied to two branches connected with each control input to the time window switch (12) as a digital clock with frequency — , that one branch contains an adjustable phase shifter (18) which causes a time shift (t^ ), and that the time window switch (12) with, in relation to the clock frequency, ignorable switching and delay times per period is closed by an edge of the undelayed signal and after time t^ again opened by an edge of the delayed signal. 8. System as stated in claim 7, characterized in that from the undelayed signal via an adjustable divider (15) with dividing factor n, a reading frequency clock is derived which closes a switch (13) for a time of approx. t_,, while one switching edge of the undelayed clock (—) via the switch (13), a triggered monoflop (9) and a downstream modulator designed as a frequency, phase or amplitude modulator, depending on the type of modulation, modulate the read pulse on the transmission signal. 9. System as stated in claim 7 or 8, characterized in that dividers (16, 19) are connected in one or both of the branches connected to the clock generator (17). 10. System as set forth in one of claims 1-9, characterized in that the duration of the read pulse is controlled statistically or quasi-statistically with regard to length so that the read pulses from very, very nearby disturbing reading devices do not constantly fall in the same time window of the same bits in the disturbed reading device, and individual noise pulses per bit, caused by adjacent readers, is suppressed by signal integration over many read periods. 11. System as stated in claim 8, 9 or 10, ~ characterized in that it shares (15) which determines., the reading pulse. duration, can be controlled electronically with regard to its sharing ratio in such a way that the period does not fall below a time determined by the longest echo time for the information carriers, and does not fall below a certain maximum reading period which is to be determined on the basis of the desired high number of readings per . effective time between reading device and information carrier. 12. System as set forth in claim 11, characterized in that the control of the divider (15) takes place by means of a quasi-statistical generator (shift register 14) which is timed by the read rate. 13. System as stated in one of claims 1-12, characterized in that the FM, PM or AM reading pulses are modulated onto a CW carrier oscillation. 14. System as stated in one of claims 1-12, characterized in that the FM, PM or AM reading pulses have an approximately Gaussian curve. 15. System as stated in one of claims 1-12, characterized in that the FM or PM read pulse is modulated onto a 100% through-modulated AM transmit pulse whose pulse time is less than the delay time T q, and which has run completely when the first echo pulse occurs at the reading device. 16. System as specified in one of claims 1-15, characterized in that the common travel time fraction xB for all echo travel times is measured to be so large that echo pulses from such information carriers that lie far outside the pre-given reading space, which is sharply limited by the time window, and because of. its considerably longer radio field travel times fall in the méd time tb shifted time window, thanks to the increased radio field attenuation, a pre-given noise distance to the echo pulses from information carriers in the pre-given reading room is observed. 17. System as stated in one of the claims 1-16, characterized in that the echo travel times given in advance in the information carriers have such a small travel time tolerance, the read pulses are designed to be so short and the travel time tolerances for the beat preparation, the sending and receiving components as well as all other building blocks that are passed by the signals up to the time window switch in the reading device, is measured so narrow that the total travel time tolerance At^ effective for the spatial resolution is small enough to ensure a spatial tolerance limit given in advance That .c Ar (Ar = —^— : c = speed of light) for that by means of the time-window switch's sharply limited reading range. 18. System as stated in one of claims 1-17, characterized in that the phase detector in the case of PM reading pulses is dimensioned so that its phase sensitivity is always optimal regardless of the absolute phase of the input signal. 19. System as stated in claim 18, characterized in that the phase detector consists of two 90° offset detectors with baseband addition coupling. 20. System as set forth in one of claims 1-19, characterized in that the information content of the information carriers consists of time differences between the echoes reflected by the information carriers and amplitude differences between the individual echoes. 21. System as specified in one of claims 1-2 0, characterized by application for monitoring, controlling and directing road traffic.