AU594946B2

AU594946B2 - A process for the detection of a starting pulse emitted from a ripple control transmitter and a ripple control receiver for carrying out the process

Info

Publication number: AU594946B2
Application number: AU55011/86A
Authority: AU
Inventors: Beat Mueller
Original assignee: Zellweger Uster AG
Current assignee: Zellweger Uster AG
Priority date: 1985-04-29
Filing date: 1986-03-21
Publication date: 1990-03-22
Anticipated expiration: 2006-03-21
Also published as: CH667760A5; ATA44086A; GB2174873A; AU5501186A; FR2581225B1; FR2581225A1; GB2174873B; DE3607028A1; AT384503B; DE3607028C2; GB8606205D0; NZ215785A

Description

COMMONW E ALTH OF AUSTRAL I A PATENT ACT '952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE 594946 Class Int. Class Application Number: Lodged:

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Complete Specification Lodged: Accepted: Published: Priority: 9004*4 Related Art:

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O E o f t f 4 0' 9 004 This document contains tLhe amendments mradc undr becuon 49' and is correct for printing' Name of Applicant: 0 0 0 Address of Applicant: a ZELLWEGER USTER A.G.

CH 8610 Uster,

SWITZERLAND.

0* 60 a Actual Inventor(s): 4 f a i 5* Address for Service: Beat MUELLER DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Complete Specification for the invention entitled: "A PROCESS FOR THE DETECTION OF A STARTING PULSE EMITTED FROM A RIPPLE CONTROL TRANSMITTER AND A RIPPLE CONTROL RECEIVER FOR CARRYING OUT THE PROCESS" The following statement is a full description of this invention, including the best method of performing it known to us -1- 1 1A 1A A process for the detection of a starting pulse emitted from a ripple control transmitter and a ripple control receiver for carrying out the process.

Ripple control receivers are so-called asynchronous receivers which when in the quiescent state, when the transmitter is not emitting, are not synchronized with said transmitter.

This means that the receiver must be synchronized with the transmitter at the beginning of each transmission.

The ripple control command emitted by the transmitter is also known as a ripple control telegram and in all known ripple control telegrams synchronization is carried out by means of a so-called starting pulse for which the receiver waits when at rest. As soon as the receiver has detected the starting pulse and recognized it as such, an impulse raster corresponding to the impulse raster of the transmitter begins to ru through in the receiver. The receiver is now synchronized with the transmitter. In order that the synchronism may be maintained, the transmitter and receiver use the same time basis, namely the 4 supply frequency.

The present invention relates to a process for the 20 detection in a ripple control receiver of a starting pu7.se emitted from a ripple control transmitter and for synchronizing the receiver with the transmitter, in which process the receiving signal is demodulated and then digitalized and the digitalized signal is scanned and the base band signal is thereby recovered and is subsequently evaluated.

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Known processes of this kind have been described, for example, in the article "Integrierte elektronische Rundsteuerempf&nger", Bulletin SEV, No. 10/1976.

According to said article, for example, every signal fed into the evaluating part of the ripple control receiver is liable to be regarded as a starting pulse so long as the pulse raster is not yet running, and running of the pulse raster, in other words synchronization, may be started after the said pulse has been received. This process has, however, the highest probability of error.

It has been proposed as an improvement to stop the pulse raster immediately when it can be assumed on the basis of subsequent development of the signal that no valid starting pulse has been received.

It is obvious that reliable detection of the starting T IT, 4 4 4 4 4 4 20 pulse and hence "correct" synchronization of the receiver are an essential precondition for troublefree operation of a ripple control receiver and must be fulfilled in all circumstances but may be seriously impaired by the disturbances constantly occurring in practice.

The present invention serves to provide a process of the type described above for receiver synchronization in which maximum account is taken of transmission distortions and disturbances.

To solve this problem according to the invention -ste-t b~;t tln-!h!-urix. 1 L-urrrmr~ -arnar~---r*~ 3 11 12 13 14 16 17 18 19 i 21 22 23 24 25 S@ 26 27 °"44 28 29 4 I 31 32 33 34 36 A:4 37 38 there is provided a process of detecting a starting pulse in a ripple command signal superimposed in an alternating current and emitted from a ripple control transmitter and for synchronizing a receiver with the transmitter, in which process a receiving signal is demodulated and then digitized thereby recovering a base band signal and a digitized signal is scanned for subsequently evaluating the base band signal, wherein for detection of the starting pulse, a recovered base band signal is temporarily stored and this stored signal is examined over a predetermined length whether its length reaches a predetermined value and/or whether it has a certain density, that is, a certain number of bits of a given content and is multiplied with a digital reference signal having the same length and form of a normally distorted receiving signal wherein a pulse is accepted as a starting pulse when it has reached a minimum and does not exceed a maximum length and/or when a minimum density has been reached and a maximum density has not been exceeded, and wherein synchronization of the receiver takes place when a correlation value obtained by multiplication of the stored and the reference signals and by summing the values obtained from said multiplication has reached its maximum and does not continue to increase.

When the process according to the invention was tested in practice, it was found that the use of a reference signal having the form of the normally distorted receiving signal causes the starting pulse to be centered in the reference signal and that the correlation value reaches its maximum precisely when the starting pulse is situated at the centre of the reference signal, and further, that due to the proposed testing of the stored signal and the correlation, the process according to the invention is virtually immune both to earlier interfering pulses and to interference gaps within the starting pulse.

891204,gcpdat.O08,5501-.c.3 3a The invention further relates to a ripple control receiver for carrying out the above mentioned process, comprising an input part and an evaluation part.

The ripple control receiver according to the invention is characterised in that the evaluation part has a shift register for temporary storage of the recovered base band signal, which register has a number of positions t t t I 6* 0 o 00 a 4 0 14C -1 I; 1 ii

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4 corresponding at least to the whole length of a starting pulse, and in that a correlator is provided for correlation of the contents of the shifting register with the reference signal.

An embodiment of the invention is described below by way of example with reference to the drawings, in which: Figure 1 is a simplified circuit diagram of an electronic ripple control receiver with a remote controlled switching membe, Figure 2 shows detail of the ripple control receiver of Figure i, and Figures 3 to 6 are diagrams to explain the function.

The ripple control receiver illustrated in Figure 1 has its input terminals 1 and 2 connected to two conductors 3 and 4 of an alternating current circuit 5 which has ripple control commands superimposed on it in known manner in the form of alternating current pulse sequences. The ripple control receiver is supplied with current from a c ~current supply part 6 in which a protective impedance 7, 20 a series capacitor 8 and a full wave rectifier 9 arranged in series are connected to the input terminals 1 and 2.

A filter capacitor 10 and a Zener diode 11 are connected to the direct current connections of said full wave rectifier.

A conductor 12 branches off at a point between the protective impedance 7 and the series capacitor 8 to lead both to a frequency selective receiving part 13 and a RC section i-x~3 i t c, 4,1 i i ii rii 5 14. The receiving part 13 which minay comprise, for example, active RC filters as selectors for the ripple control frequency, is connected at one end to a negative bus-bar and at the other to a positive bus-bar 16 to be supplied with the necessary feed voltage from the current supply part 6. An output terminal 17 of the receiving part 13 is connected to a first input 18 of the evaluating part 19 of the ripple control receiver.

A lead branched off a point between resistor and capacitor of the RC member 14 is attached to the second input 20 of the evaluating part 19. A signal at the supply frequency is fed into the second input 20 of the evaluating part 19 by way of the RC section 14 to enable a sequence of timing pulses bound to the suoply frequency to be formed in the evaluating part 19 as an electronic time basis for evaluating the received pulse sequences.

The evaluating part 19, which is connected to the negative and positive bus-bars 15 and 16 and thereby receives the necessary voltage from the current supply part 6 is a one-chip microcomputer with a fixed programme, preferably a masked prograrme. Since electronic evaluating parts for ripple control receivers are known, these will not be described in detail here but it may be noted that the evaluating part 19 contains inter alia electronic storages and shift registers for intermittent storage of received pulse sequences. Every such stored pulse sequence is compared with a pulse sequence (ripple control

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-6- 6 command) associated with the corresponding ripple control receiver and, if the result of comparison is positive, an approval signal is emitted from a first or second output 21 or 22 of the evaluating part 19 to serve as actuating signal for a remote controlled switching member 23. The switching member 23 shown in the drawing has a switch 23' which is switched on or off, depending on whether the approval signal appears at the output 21 or 22, and a current consuming device 24 is thereby connected to or disconnected from the circuit To operate the switch 23', the signal appearing at the output 21 or 22 of the evaluating part 19 is passed either through a switching transistor 25 or through a switching transistor 26 so that the one or other of the two windings 27 and 28 of a relay 29 carries current and thereby connects or disconnects the switch 23'. Protective diodes are connnected in parallel with the windings 27 and 28 to protect the transistors 25 and 26 against inductive voltage surges.

oao A switching energy store 30 in the form of a storage capacitor with sufficient capacitance for actuating the switch 23' is associated with the switching member 23, The ripple control receiver is illustrated in a highly simplified form in Figure i. For a more detailed illustration and description, see-Swiss Patent 567824 and Swiss Patent Application No. 714/85 and the article "Integrierte elektronische Rundsteuerempf~nger" by H. de Vries in Bulletin SEV, No. 10/1976. As may be seen from this It *1 t 4 o 4~ 7 article, the frequency selective receiving part 13 contains a rectifier as an AM demodulator and a level detector connected in series with this demodulator. The said level detector provides a digital signal which is the recovered base band signal distorted by the transmission.

The digitalized signal is scanned and supplied to the evaluating part 19. In the present ripple control receiver, it is advisable to use a multiple bit level detector (A/D convertor) which provides multiple bit digitalization of the demodulated receiving signal, although a simple tobit digitalization could conceivably be used.

Transmission of a ripple control command begins, as is known, with the emission of a first signal, the socalled starting pulse, which ensures the synchronism between transmitter and receiver. This is followed by the pulse sequence which,characterises the command and which in a known system, the "DECABIT" system of the Applicants of the present patent application, consists of 5 further pulses and 5 pulse gaps. Each of these steps has a length of 600 ms, as does the starting pulse.

Identification of the starting pulse is of major importance for correct functioning of the ripple control receiver since it is only when the starting pulse has been identified as such and the time base has been started that evaluation of the received pulse sequence proper, i.e.

its comparison with a nominal pulse sequence associated -8with the corresponding ripple control receiver, can be carried out in the evaluation part 19. When the receiver is in its quiescent state it watts for the starting pulse.

As soon as this pulse has been identified, the receiver is synchronized with the transmitter and a pulse raster corzesponding to the pulse raster of the transmitter begins to run in the receiver.

According to Figure 2, the evaluating part 19 comprises a shift register 31 and a register 32 which has the fitsame bit number as the digitalization and a sufficient number of positions to accommodate the whole length of a scanned starting pulse. The scanned digitalized signal is fed into the shift register 31 and a reference signal is stored in the register 32. The individual register S 15 positions 1 to n of the two registers 31 and 32 are connect- 0 44 ed to one another by digital multipliers 33 the outputs of which are transmitted to a summation element 34.

Figure 3 is a somewhat different representation of the registers 31 and 32. Line a shows the four-bit shift S SI 20 register 31 with n positions in which a receiving signal S (starting pulse) has just been inserted from the right.

Line b shows the register 32, which ls also a four-bit register, in which a four-bit reference signal R with n positions is stored.

The digital multipliers 33 and the summation element 34 (Fig. 2) now correlate the two signals S and R so that the correlation value K of the two signals S and R 9 n K= (RiSi) is obtainable at the output of the summation element 34.

The maximum correlation value K is obtained when there is maximum agreement between the two signals S and R.

The evaluating part 19 now tests during each scanning interval, i.e. in phase with the supply frequency, the contents of the shift register 31. It carries out the following tests: I Measurement of the length of signal S from the rising to the falling edge by counting. This measurement will hereinafter be referred to as examination of length.

Counting of the number of register positions having a bit number greater than 0 (or greater than any threshold value). This counting will hereinafter be referred to as examination of density.

In addition, the contents of the shift register 31 is multiplied by the digital reference signal R stored

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in register 32, and the correlation value K of the two signals S and R is thereby determined.

The reference signal R shown in line b of Figure 3 is again shown in Figure 4. In this figure, line a shows the transmitted rectangular starting pulse; line b shows the signal at the output of the demodulator on the receiver side as well as the threshold U S of the level detector; and line c shows the two-bit digitalized receiving signal S which has been shortened by distortions at the edges .1 s- T 2 O10 due to transient effects of the narrow band filters in the transmitter and receiver. Line d shows a particularly suitable reference signal R which has been chosen to conform very accurately to the curve of a base band signal (line b) received with the normal transmission c 3tortions and has slopes at the leading and trailing edges.

The examination for length and density of the receiving signal described above and correlation of the signal with the reference signal now provide optimum criteria for identification of the starting pulse and synchronization of the ripple control receiver.

A pulse is accepted as a starting pulse when it has reached a minimum length and does not exceed a maximum length (examination for length) or when, in the event of 15 short interfering gaps which, however, must not exceed e.g. two bits, a minimntum density has been reached and a maximum density has not been exceeded. Fulfilment of one of these two conditions provides the criterion for starting, which may be fulfilled over several phases,, Synchronization, that is to say, starting of the internal pulse raster, however, does not take place until the correlation value reaches its maximum, i.e. increases no further.

The synchronization process described above, using the starting criterion and the synchronization criterion, is illustrated diagrammatically in Figs. 5 and 6. In the lefthand column, the top line shows the reference signal R stored in register 32 (Fig. this signal being formed f

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If (t 9 0 4 Si 44 6 8 6 46 -11in the present case by the sequence "23333321".

Indicated below this reference signal is the shift register 31 which has 8 storage positions and in which the receiving signal S ""11111111" is inserted from the right. Below the shift register, the continuous insertion of receiving signal S into the shift register 31 is symbolized in each line for the particular cycle. The middle column shows whether and when the starting criterion is fulfilled, "0" representing unfulfilled and "START" representing fulfilled, and the corresponding correlation values K are entered in the righthand column. Fulfilment of the synchronization criterion and hence starting of the internal pulse raster are marked by an arrow.

The starting criterion is determined by the examination for density, i.e. this criterion is fulfilled when the 4 receiving signal S has a sufficient density in the coraelation window, this density amounting to 6 to 8 bits in the drawing.

cr sr Oo. The process is illustrated in Figure 5 by reference to o 1€ a receiving signal S having the nominal length of a starting pulse of 8 bits and Figure 6 shows the process with an earlier interfering, pulse ST which is followed by a receiving signal S of 8 bits.

As may be seen froi Figure 5, the starting criterion is fulfilled from the 7th to the llth cycle, which means that the receiving signal is recognized as a starting s- PIP ~CI---PY- 12 pulse at the 7th cycle. The correlation value K continuously increases to reach its maximum at the 9th cycle and then decreases. The criterion for synchronization is exactly fulfilled when the starting pulse is centered in the correlation window, in other words in the shift register 31.

The example illustrated in Figure 6 resembles that in Figure 5 in that in the first cycle, the receiving signal o S is situated immediately in front of the shift register 444 r* o O10 31, but in this case an interfering pulse ST of three 4514*

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bits has previously been inserted. The interfering pulse ST, however, cannot fulfil the starting criterion since it does not pass the density test. The starting criterion is therefore again fulfilled from the 7th to llth cycle as in Figure 5, and the synchronization criterion is again fulfilled at the 9th cycle, which is exactly at the time CO Ge 44 4o when the starting pulse S is centered in the correlation window.

If the gap between the interfering pulse ST and the starting pulse S were shorter than 3 bits, which in practice rarely occurs, it would have no interfering influence.

Although the starting criterion would then be fulfilled earlier, the synchronization criterion would not be fulfilled earlier since this specifies that the correlation value K no longer rises. In that case, therefore, the internal pulse raster would again not start to run until the receiving signal S is centered in the correlation 13 window. It should also be mentioned that although in Figure 6 the correlation value K also ceases to rise after the 3rd and 4th cycle, the starting criterion is not fulfilled in these cycles, i.e. the receiving signal S is not recognized as a starting pulse, and hence the synchronization criterion cannot be fulfilled.

Even when a receiving signal S is shortened by not more than 2 bits, the synchronization criterion is not fulfilled until the receiving signal is centered in the correlation window.

If, as described above, the shift register 31 has just sufficient positions to accommodate the whole length of a starting pulse, then the examination for length and density does not check whether a pulse exceeds a maximum length or density but only whether the minimum length or density has been reached. If a check is to be carrie( out to ascertain whether the maximum length or density has been exceeded, which would be purposeful if the ripple Scontrol telegram had a gap after the starting pulse, then the shift register 31 must have a number of positions exceeding the length of a starting pulse.

The process described provides maximum reliability for recognizing a starting pulse and for synchronizing the ripple control receiver at the correct time. This is achieved both by adapting the reference signal to the form of a normally distorted receiving signal by sloping off the front and rear edges and by fixing the starting 14 criterion (length and density test) and the synchronization criterion.

Claims

4.44ff 30 31 32 33 34 36 37 V 38 1. A process of detecting a starting pulse in a ripple command signal superimposed in an alternating current and emitted from a ripple control transmitter and for synchronizing a receiver with the transmitter, in which process a receiving signal is demodulated and then digitized thereby recovering a base band signal and a digitized signal is scanned for subsequently evaluating the base band signal, wherein for detection of the starting pulse, a recovered base band signal is temporarily stored and this stored signal is examined over a predetermined length whether its length reaches a predetermined value and/or whether it has a certain density, that is, a certain number of bits of a given content and is multiplied with a digital reference signal having the same length and form of a normally distorted receiving signal wherein a pulse is accepted as a starting pulse when it has reached a minimum and does not exceed a maximum length and/or when a minimum density has been reached anrid a maximum density has not been exceeded, and wherein synchronization of the receiver takes place when a correlation value obtained by multiplication of the stored and the reference signals and by summing the values obtained from said multiplication has reached its maximum and does not continue to increase. 2. A process according to claim i, wherein the recovered base band signal is inserted into a shift register having a number of positions corresponding to the whole length of the starting pulse, and in that the contents of this shift register are examined during each scanning interval to ascertain the length of the starting pulse and the number of those register positions whose bit content exceeds a certain threshold value. 891201,gcpdat.008,55011.c. 41~--un Ililiii II 3. A process according to claim 2, wherein the recovered base band signal stored in the shift register is detected as the starting pulse either when its length reaches a minimum value and does not exceed a maximum value or when, in the 3vent of short gaps existing in the signal under investigation, the said signal occupies a number of register poritions having a bit. Bonr( t exceeding the threshold value, which number of postions reaches a minimum value and does not exceed a maximum value. 4. A process according to claim 3, wherein synchronization only takes place if the correlation value reaches its maximum at a point in time at which a starting pulse is also detected. A process according to one of claims 1 to 4, wherein tae reference signal -M and the shift register have a bit(f corresponding to the digitalization of the demodulated receiving signal.
6. A process according to claim 5, wherein the reference signal 4m- has slopes at its front and rear edges adapted to the form of the normally distorted receiving signal.
7. A process for the detection in a ripple control receiver of a starting pulse emitted from a ripple control transmitter and for synchronizing the receiver with the transmitter, substantially as herein described and as illustrated in the accompanying drawings. ii 17 .4 11 12 13 14 16 17 i 18 19 20 21 22 23 24 a 25 26 27 o 28 29
8. A ripple control receiver for carrying out the process according to claim 1, comprising an input part and an evaluation part, wherein the evaluation part has a shift register for temporarily storing the recovered base band signal, said register having a number of positions at least corresponding to the whole length of a starting pulse, and in that a correlator is provided for correlating the contents of the shift register with the reference signal.
9. A ripple control receiver according to claim 8, wherein the evaluating part has a register in which the reference signal is stored and in that the reference signal and the shift register have a bit content corresponding to the digitalization of the demodulated receiving signal.
10. A ripple control receiver according to claim 9, wherein the shift register and the register have an equal number of register positions and in that corresponding register positions of the two registers are connected by digital multipliers the outputs of which are connected to a summation element for forming the correlation value.
11. A ripple control receiver according to claim 7, wherein the reference signal and the shift register have a bit content corresponding to the digitalization of the demodulated receiving signal.
12. A ripple control receiver according to claim 8, wherein the two registers have an equal number of reigster positions.
13. A ripple control receiver substantially as herein described and as illustrated in the accompanying drawings. DATED this ist day of December, 1989 ZELLWEGER USTER A.G. By its Patent Attorneys DAVIES COLLISON 891201,gcpdat.008,55011.c.17 a 4 4 44 31 32 33