DE2008514A1 - Telegraphy receiving device for harmonic telegraphy - Google Patents

Description

20085U

FPHN M 15OC Va / RJ

You. Herbert Scholz

Applicant, -.! Delecö & uSlicatione Hadioeleotriques & Telephon! Ques

Akfe N0.-PHN-4I 50
Registration from »February 23, 1970

"Telegraphy receiving device for harmonic telegraphs e "..

The invention relates to a multi-channel t | Telegraphy receiving device for harmonic ToJogruphio, with different levels of the input signal per channel are characterized by different carrier frequencies.

It is known that telegraph receivers of the type mentioned above have the disadvantage that they are unreasonable sensitive to changes in the atmospheric state,., such as changes in temperature, humidity, etc., are. It has been found that the required frequency stability with the usual telegraphy receivers,

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which are provided with coils in the usual way, difficult due to this undesirable atmospheric influence is achievable. With a receiver that has three different frequencies per channel and one transmission speed of 50 Bd works, this atmospheric influence leads, for example, to a frequency accuracy requirement in the order of 1/1000.

In the known telegraphy receivers of the type mentioned above, there is therefore the problem of frequency stability and the frequency control required for this, which is in particular due to the large number of frequencies (e.g. 72 different frequencies for a 24-channel receiver with three frequencies per channel) is made considerably more difficult.

The invention aims to provide a Telegraphleempfänger of the aforementioned type, which is excellent in frequency stability, which is particularly insensitive to at- ff mosphärische changes, whereby also a frequency control is unnecessary.

According to the invention, such a receiving device contains one per receiving channel for this purpose Discriminator consisting of a digital counter, one coupled to the input of this counter continuously effective counting pulse generator and a decoding device connected to the mentioned counter whose output circle is represented by a register with oinoni

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separate output formed for each of the different levels will; while such a receiving device furthermore is provided per channel with a signal input circuit with a zero crossing detector, whose output pulses the mentioned counter and the mentioned register are supplied, the counter being returned to the zero position when such an output pulse occurs offset and the register is influenced by the same output pulse in such a way that that at the reset time occurring at the output of the decoding device Signal appears at the output of the register that corresponds to the level in question.

When using the measures according to the invention will with; With the help of the counter measured the time between two characteristic for the input signal Points in time runs; these points in time can be two consecutive Be zero crossings of the carrier frequency in which If the measured time interval corresponds to half a period; however, these zero crossings can can also be chosen in such a way that they are around a certain whole number of periods are different from each other.

The invention is explained in more detail below with reference to the accompanying drawings. ''.

Fig. 1 shows the period ^ t, during the the position of the counter does not change, as well as the periods t, t and t, which correspond to the three frequencies fO - 30 Hz,, p s ι »

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fo and fo + 30 Hz, and the N counting positions that the counter during dfjs time interval between your zoom point 0 and the point in time T runs through one after the other;

Fig. 2 shows a block diagram of an embodiment of a receiving channel of a receiver according to the invention, which is suitable for use in a transmission system that transmits three levels at a transmission speed of 50 Bd.

Fig. 3 shows in detail an embodiment of such a channel;

Fig. H shows a number of diagrams 4a, 4b, 4c, 4e and 4f of the signals as they occur at the outputs P and N of the register, these signals being shown in the event that no logic filter according to the invention is used , or in the event that such a filter is used to suppress interference caused by noise.

Fig. 5 shows an embodiment of the means generally used to suppress the above-mentioned disturbances caused by noise will.

FIGS. 6, 7 and 8 show diagrams of signals which largely correspond to those of FIGS. 4b, 4c, ka and kf.

Fig. 7 corresponds to Fig. Ha and shows a square-wave pulses from existing signal as When employing

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ORIGINAL INSPECTED

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transmission of the three-value code (three levels).

FIG. 8 shows the diagram of the signals P and N as they occur at the output of the bistable elements 5 and 6 (dde * ¹ P and N) of FIG.

Fig. 9 symbolically shows and

FIG. 10 shows in detail the time constant circle preceding the monostable circuit (FIG. 13), which combination brings about the filter effect according to the invention, as shown in FIG. Kd .

Fig. 11 shows the signals generated at the points C_ and S "of the time constant circle of FIG. 10 occur.

Figs. 12 and 13 show an embodiment

the monostable circuit that is used when building the logical Filters ^ d is used.

14 shows the output signal appearing at S " of the monostable circuit of Fig. 13, the occurs when a signal is received at C ».

. Fig. 15 shows the diagram of the final Square-wave signals (line. "1.5C) which occur at the output of the differentiating device 12" of FIG. 3 and which used to control the counter and the output register will; Line 15a shows the input signal and * Line 15b the output signal of the designed as a limiter Amplifier 11.

Fig. 16 is a table shown only as

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an example is to be considered and which for each of the channels numbered 1 to 2k the crystal frequencies /: for generating the required sequence of intermediate frequencies e'n and the values of the three characteristic frequencies S, P and N, as they are in practice can be obtained when working with the three-value code (three levels).

Fig. 17 shows the time interval ΔΤ, during whose position does not change the counter, as well as the

Periods t, t and t representing the three. Frequencies f0 - 30 Hz; η ρ s

fo and fo correspond to + 30 Hz, and the N counting positions which the counter passes through one after the other during the time interval between 0 and time T; the frequency fo is not transmitted; of this frequency corresponding zero crossing falls, as can be seen from this figure, accurately with the border between the examples Wf the Zähllagen together, corresponding to the state N or the P state.

18 shows schematically a discriminator according to the invention for use in a transmission system, using a two-valued code (two levels).

The device according to the invention, its principle adraltbild is shown in Fig. 2, contains a discriminator, which consists of a digital counter 1, one with counting pulse generators coupled to the input of this counter

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rator 2 and a decoding device 3 connected to the mentioned counter is constructed, the output circuit of which is formed by a register k with its own output for each of the different levels 1, while a signal input circuit 5 with a zero passage detector 6 is also provided, the output pulses of which correspond to the mentioned counter 1 and the mentioned register _ k . The input signal which is fed to the input pin 5 is shown in FIG. 15a. This input signal varies between three frequency values fo - Δ f, fo and fo + Δ f ₍ which are characteristic of the levels T, S and * N to be transmitted, which are used in Qinen three-valued code The time intervals that these periods cover are indicated in the figure "it t" t -basy. % . These time intervals have a different duration, ie that (| According to the invention, these differences are used as a criterion for differentiating the different frequencies. The time between two zero crossings is measured with the aid of the counter 1. The decoding device 3 connected to the counter ensures that after each measurement Signal occurs at one of the outputs of register h , depending on:

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sufficient counting position that is characteristic of the frequency characterizing the level.

In the device according to FIG. 3, the counting pulse generator formed by a crystal oscillator 7 and an adjoining frequency divider 8. The ones supplied by this counting pulse generator

^ Counting pulses are fed to the counter 1, which contains four stages in the illustrated embodiment, each of which consists of a bistable element 9, 10, 11, 12. In the embodiment shown, the register h is formed by two bistable elements 13 and ^ k . These bistable elements are connected to the counter 1 via the decoding device 3, which contains two "not-and" gates 15 and 16, the output of the gate 15 on the one hand directly to the input J ^ and on the other hand via an inverter 17 to the Input k des

ψ bistable element 13 is connected, while the output of toro 16 is connected directly to Ki η gang JL on the one hand and via an inverter 18 to input k of bistable element 14 on the other hand. The zero crossing detector 6 included in the input circuit 5 is formed in the illustrated embodiment by an amplifier 19, which acts as a limiter and which converts the input signal, which has a more or less sinusoidal profile, into square-wave pulses, which are then sent to a differential:

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device. 20, the output pulses of which are fed to the frequency divider 8, the bistable elements forming the counter 1 and the bistable elements 13 and 14 of the register k . The latter register contains only two outputs P and N, so that only two levels can be specified. However, the constricting zwischenlie- ~ S level may, if it occurs, from the simultaneous absence of level N and P abgelei- -

be switched.

When using the measures according to the invention, a receiver for harmonic telegraphy with η channels can be obtained, each channel being provided with a counter of the type described above. For example, the invention can be used in a telegraphy system for harmonic telegraphy with a transmission speed of 50 Bd with 2k channels that are centered with respect to the frequencies that are determined by the \

Formula:

f _k = 60 (5 + 2k)

are given, where k is an integer between 1 and 2k . If it is assumed that one of these center frequencies is equal to the frequency ft>, the three fre-

sequences that characterize the three levels to be transmitted are specified as follows:
Level P: fo- - 30 Hz

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Level S: fo
Level N: fο + 30 Hz.

In the embodiment shown in FIG these three frequencies with the help of the digital counter 1, to which the counting pulses of the counting pulse generator 2 are fed are distinguished from each other. In this embodiment, the discriminator is set up in such a way that that it is the time interval between two zero crossings of the carrier wave running in the same direction measures. The counter is reset to the zero position whenever such a zero crossing occurs. The received frequency is marked by the counting position in the counter at the time of the reset .

If N indicates the number of positions that the counter takes one after the other in the time interval t (see FIG. 1), the time during which the counter is in a certain counting position is given by: At = t / N.

The number N determines the number of stages of the counter, while the time At determines the repetition frequency of the counting pulses to be fed to the counter. These two parameters must be chosen as a function of the frequency fo and the difference between the periods of the three frequencies to be underexed. In addition, the condition still applies that:

Ut = T - T _n (see Figure 1);

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from this it follows »that:

Δ t = \ / h (jr- - ± -)
η ρ

f -J

• f f

= Λ / h.

60

fp.fn

so that: Δ t = rf

The following also applies:
T

N =

6θ2

f 2 ο

t§

, or else

= 20 ₊ 8k,

what can be written as:

N = 16 + - '»+ 8 k = Ii + 8 (k + 2),.

Since noise can be superimposed on the received signal, it must be taken into account that the measured duration of the periods is not entirely accurate. In this context , each of the frequencies is not characterized by a counting position belonging to this frequency, but by a number on the following counting positions, which each characterize the same frequency for themselves » In this case. the detection criterion can be selected, for example according to FIG. T, in such a way that the level P is determined by each of the counting

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were marked between the counting position n + 1 and the counting position n + 3 will.

Dor Pogo I S is replaced by jode dor count 1 agon between the counting positions n-1 and the counting position η .

Level N is identified by each of the counting positions between counting position nh and counting position n-2.

The minimum number of counting positions of the counter is thus: N + ^ (whereby counting position 0 must be taken into account), or else: 8 (k + 4). Therefore, there is a simplification which consists in the fact that instead of a counter in which the Number of counting positions is also determined by the channel and depending on the channel 12 to 216 counting positions a modulo-8 counter (8 counting positions) can be used in each of the channels.

This extraordinary simplification can also be achieved by using a two- or three-value code with a transmission speed different from Oinor'von ^ D Bd, whereby a different discrimination criterion naturally applies and the number of counting positions is greater or less than 8. During the measurement, the counter K + runs through its complete counting cycle twice and stops during the subsequent counting cycle in one of its 8 counting positions, which is determined by the current period of the carrier frequency. The discrimination criterion can be goschrio-

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be practiced:

Level P: 5 < counting position - £. 7 '' level Si 3 <counting position < k level N: O <counting position * C 2.

Since K no longer has any influence, this discrimination according to the invention can occur in all channels can be carried out so that a counter with 8 counting positions can be arranged in each of these channels. ■. *

Tests were carried out with a receiver of the type described in FIG. 3 in order to be able to determine the behavior of the receiver with different signal-to-noise ratios. The signal and the noise were measured at the output of the telegraphic filter belonging to the receiver; in this case it is the signal-to-noise ratio in the passband of the channel. Two types of noise are superimposed on the signal one after the other: a) white noise,: b) a signal Λ with a frequency chosen arbitrarily in the passband of the channel. It has been found that these two types of noise do not have a different influence on the behavior of the recipient. In the case of unfavorable signal-to-noise ratios (of the order of magnitude of 15 dB), the output signals exhibited interference (see FIGS. 4a , 4b, kc and 6). These disturbances are due to the uncertainty caused by the noise about the point in time of the zero crossing of the input signal.

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to lead. Each of the points on the diagram corresponds to a count error over one or two periods of the signal; dioHO foal or troton especially often in the vicinity of the Nu L Idurcligänge. This difficulty also arises with the usual recipients; the undesirable effects are largely eliminated by the inertia of the resonant circuits from which the discriminator is constructed; but this is at the expense of the bandwidth. In the device according to the invention, these inaccuracies caused by the noise can be eliminated by means of a low-pass filter 21 according to FIG. However, this solution is expensive because, after filtering, the signals have to be brought into the correct form again by a pulse regenerator 22 connected to the filter. This filtration is therefore preferably carried out in a simpler and more economical manner with the aid of a logic circuit which is constructed from a circuit with a time constant and a monostable circuit according to FIGS .

Fig. 7 shows a transmitted signal with three different levels. If there is no Disturbances occur, the output signals of the two bistable elements P and N of FIG. 3 by the Diagrams according to Fig. 8 are shown. The noise has the consequence that the zero crossings are arbitrary

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Have shifts, as a result of which the time measurement is incorrect over certain periods of the carrier frequency. At the outputs of the bistable elements P and TM, such error pulses cause the duration of which is equal to one period of the carrier frequency. When such a pulse is received, the circuit according to FIGS. 9 and 10 supplies an output signal according to FIG. ^ d filtered; the filtering and the regeneration are therefore carried out at the same time. These filters are connected to the outputs 0 of the bistable elements P and N, that is to say that the signals fed to the filters are inverted with respect to the signals shown in FIG. ^r If the receiver is equipped with such filters, a signal-to-noise ratio of 12 dB is permissible.

The receiving apparatus according to the invention is _ '' μ not limited to use in systems where three levels are transmitted ,, but can also be used in systems in which only two levels are transmitted "Starting from the for an input signal with three Definitions given to levels can be written in the case of two levels:

(fo) a = 60 (5 + 2k)

f = fo - 30 Hz - ■ = ■ "

f "= fo + 30 Hz

0 0983 * / UB0

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(Only the frequencies f and f are sent out).

Assuming that At = T - T, it follows that:

F-F T 1 1 η ρ 6θ

^pn ρ η F .F f * * η ρ ο

™ from which it follows:

T f ² f

N = -Λ . f = = r £ = 5 + 2K or 60 ο oOfo oO

N = 2 (K + 2) + 1.

From the above, it is apparent that the counter 8 Zähllagen, which is used in modulation with three frequencies by a counter with 2 Zähllagen, that is a counter with a single stage, can be replaced. The discrimination criterion will be:

Level N bistable in position 0

Level P bistable in position 1.

The pulse repetition frequency P of the counting pulses fed to the counter is:

^F = ^ 7 = T = ^f o ^N - 37Γ - ^6o

1 N f

The crystal frequency is:

F = 60 (5 + 2k) ² . 2 ^X.

The word χ (i.e. the number of divisors in the

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Frequency divider) is preferably chosen such that the crystal frequency has a value between 2 and h MHz. ,

In a receiving device for a telegraphy system in which only two levels are transmitted, a register with two bistable elements P and N no longer needs to be used because a single bistable element with positions 0 and 1 is sufficient. Each of the two outputs of this bistable circuit is provided with a filter of the type shown in Fig. 10, which the signals C ^ and S _? which are fed to a bistable circuit which is bound by two "non-TJnd" gates and which reproduces the transmitted signal with great accuracy.

Fig. 11 shows the signal at the output of the Apparatus according to Fig. 10 occurs when a square wave signal is applied to the input of this apparatus.

The above-described embodiments of a Receiving device according to the invention can be used in a 24-channel telegraphy system in which the Input signals per channel have two or three levels and at which the transmission speed is 50 Bd, i.e. one bit has a duration ^ t of about Has 20 msec.

The receiving device according to the invention but can also advantageously be designed in such a way that

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that it can be used in a 6-channel telegraphic system in which the input signals have two or three levels and the transmission speed is 200 Bd, i.e. the duration Δ t of a bit is approximately equal to 5 msec, i.e. four times shorter. Such a receiving device largely corresponds to the receiving device described above and is also based on the measurement of the time between two zero crossings. Taking into account the fact that at a transmission speed of 200 Bd the duration of a bit is only 5 msec and that this corresponds to at least two periods of the carrier frequency for the lowest frequency, it is advantageous to reduce the distortion if the time span between two immediately after one another following zero crossings of the carrier frequency signal is measured. A receiving device of this type therefore differs from the receiving devices described above in that the time is not measured over a complete period of the carrier frequency signal, but rather over half a period (see FIG. 19).

Finally, it should be noted that even if a comparison between a precisely regulated the usual telegraph receiver and the receiver the invention results in no real difference in transmission quality, the improvements and advantages of

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Receiving device according to the invention still consist in the fact that this device is not de-regulated by atmospheric influences, such as temperature changes can be; that certain parts of the receiver are more suitable for mass production; that space is saved.

In addition, the receiving device according to the invention has the significant advantage that the crystal frequencies of the respective channels are identical to those of the transmitter described in Dutch patent application No. 6903701 (9HBSQQM). This is particularly important for achieving a "modem" because in this case the oscillator can be combined with part of the frequency divider. Reference is made to the table in FIG. 6 for the crystal frequencies to be used.

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Claims (1)

- 20 - FPHN Μ5OC Claims ; Π.) * Multi-channel graphic receiving device for Harmonic telegraphy, in which different levels of the input signal per channel due to different carrier frequencies are characterized, characterized in that the receiving device per receiving channel one ^ k contains discriminator, which consists of a digital counter, one with the input of this counter coupled continuously effective counting pulse generator and one to the mentioned counter connected decoding device is constructed, the output circuit through a register with a separate output is formed for each of the levels, while the receiving device furthermore per receiving channel a signal input circuit with a zero crossing detector contains whose output pulses the mentioned counter and are supplied to the mentioned register, with the occurrence of such an output pulse The counter is reset to the zero position and the register is influenced by the same output pulse in such a way that that that at the reset time at the output of the decoding device Occurring signal appears at the output of the register belonging to the level in question . 2. Multi-channel telegraphy receiving device according to claim 1, characterized in that the counting pulse 009838 / U90 2Ö085U FPHN 415OC generator is composed of a pulse oscillator and an adjoining frequency component consisting of jl divider stages, of which each output pulse is characteristic of a time increment Δ t of the counter, 2 ^X where the oscillator frequency is F =. L · ^τ 3. Multi-channel telegraphy receiving device according to claim 2, characterized in that the number of divider stages χ of the frequency divider is chosen such that the oscillator frequency F is between 2 and k MHz. k. Multi-channel telegraphy receiving device according to claim 1, 2 or 31, which has three levels per receiving channel, which are characterized by frequencies fo - ^ S, fo or fo + AS, characterized in that the discriminator is designed such that between the one period of the Frequencies fo - Δ S, fo or fo + / j S corresponding time intervals t, t or t and the duration of a time increment Δ t, the following relationships exist: and k ^ t = t -t, where N is equal to the number of counting positions that the counter runs through one after the other in the time interval t. 009838/1490 20085U FPHN k 15OC 5. Multi-channel Telegraphieempf sawing device according to claim 1, 2 or 3 »which has three levels per channel, which are characterized by the frequencies fo ¹ -Af, fo or fο ♦ Λ f, characterized in that the discriminator is designed in such a way that that between the time intervals t, t or t corresponding to a period of the frequencies fo - Af, fo or f ο ♦ Δ f and the duration of a time increment Δ Τ, the following relationships exist: ^ t = - 2N t - t P η and Ί4 t = where N is equal to the number of counting positions that the counter runs through one after the other in the time interval t. 6. Multi-channel telegraphy receiving device according to one of the preceding claims, characterized gekennzoichnet that the outputs of the mentioned register with each a filter device and a subsequent pulse regenerator are provided. 7 * multi-channel telegraphy receiving device according to claim 6, characterized in that said Filter device and the mentioned pulse restorer are formed by a time constant circuit and a monostable circuit connected to it. 009838 / U90 Blank page