CN1169338C - digital splitter - Google Patents

Abstract

A digital splitter, it has: a signal sending path, it comprises: an analog/digital converter (59), is used for converting the analog voice signal to be sent into a digital voice signal; a digital low-pass filter (63 ), for low-pass filtering of digital voice signals; a digital high-pass filter (71), for high-pass filtering of digital data signals; a summation circuit (67), for digital voice signals of low-pass filtering and high-pass The filtered digital data signals are summed to form a digital transmission signal; and a digital/analog converter (81) for converting the digital transmission signal into an analog transmission signal to be transmitted via the telephone connecting wire (4); and A signal receiving path, which includes: an analog-to-digital converter (11) for converting the received signal received through the telephone connecting wire (4) into a digital received signal; a digital low-pass filter (23) for Filter out the digital voice receiving signal from the digital receiving signal; a digital high-pass filter (18) is used to filter out the digital data receiving signal from the digital receiving signal; and a digital/analog converter (27) is used to filter The output digital voice receiving signal is converted into an analog voice receiving signal.

Description

digital splitter

technical field

The invention relates to a digital separator for low-frequency voice signals and high-frequency data signals.

Background technique

ADSL signals and narrowband business signals or ISDN signals can be transmitted simultaneously in one telephone connection wire. In this case, the different transport paths are separated by means of separators.

FIG. 1 shows the circuit arrangement at a telephone exchange at a subscriber A, and a subscriber B is connected to this circuit arrangement via telephone connecting lines. Subscriber A has only one ISDN terminal, to which one ISDN terminal EGA is connected. Subscriber A can connect his ISDN terminal EGA directly to the telephone connection line TL _A , which is connected to the corresponding ISDN terminal and the telephone exchange. In this case, the ISDN terminal provided in the telephone exchange consists of an ISDN data processing circuit via a digital/analog converter connected in the opposite direction with a hybrid circuit H _A connected.

The second subscriber B has an ISDN terminal ISDN _B , which is connected to an ISDN terminal EGB, and an ADSL terminal ADSL _B , which is connected to an ADSL modem or a terminal _EGB -ADSL. In order to separate ADSL signals and ISDN voice signals from each other in subscriber B, an analog splitter is required not only in the telephone exchange but also in the subscriber.

Figure 2 shows such a conventional analog separator according to the prior art. Since the ISDN signal has a frequency range from 0 to about 80-120 KHz and the ADSL data signal has a frequency range from 135 KHz to about 1.1 MHz, these two signals must be selectively filtered on both sides of subscriber B's subscriber connection conductor TL _B . The telephone connecting lines TLA and TLB are conventional two-core telephone connecting lines.

The analog splitter shown in FIG. 2 consists of both transmit and receive signal paths, each with an analog high-pass filter and a low-pass filter. The analog splitter has a terminal TL connected to the telephone connection line, which is connected in the signal transmission path of the analog splitter to the output of a signal adder. The signal adder adds an ADSL transmit signal filtered by the analog high-pass filter HP to an analog ISDN signal filtered by the analog low-pass filter TP. The resulting sum signal is output via the analog splitter onto the telephone connection lead.

On the receive path of the analog splitter, the mixed signal received via the telephone connection line TL is passed to an analog high-pass filter HP and an analog low-pass filter TP. The analog high-pass filter HP filters out high-frequency analog ADSL data signals on the receive side of the analog splitter. The analog low-pass filter TP filters out low-frequency analog ISDN speech signals on the receive side of the analog splitter.

The analog splitter according to the prior art shown in FIG. 2 has two high-pass filters and two low-pass filters, which are implemented conventionally by passive analog components. These components include inductors, capacitors and ohmic resistors. Analog high-pass filters and low-pass filters can therefore only be produced with relatively high circuit and production costs associated therewith. In particular, higher-order analog filters can only be realized with a high circuit-technical outlay.

Another disadvantage of filters of analog structure is that their electrical transmission properties will change due to aging processes. In addition, analog filters of passive structures affect the performance of the physical interface, such as reflection damping of the signal.

Another big disadvantage is that it is impossible to change the electrical transmission performance or filtering performance on the high-pass and low-pass filters of the analog structure in the conventional analog splitter shown in FIG. 2 . Therefore, conventional analog-structured separators cannot be flexibly used in different applications.

Contents of the invention

It is therefore the object of the present invention to create a splitter which ensures good separation of high-frequency data signals and low-frequency speech signals with low circuit-technical outlay and which can be flexibly adapted to various applications.

According to the invention, this task will be solved by the following digital separator.

The present invention provides a digital splitter which has

(a) A signaling path comprising:

a first analog-to-digital converter for converting the analog voice signal to be transmitted into a digital voice signal,

a digital low-pass filter for low-pass filtering the digital voice signal,

a digital high-pass filter for high-pass filtering a digital data signal,

a summation circuit for summing the low-pass filtered digital voice signal and the high-pass filtered digital data signal into a digital transmission signal, and

a first digital-to-analog converter for converting said digital transmission signal into an analog transmission signal to be transmitted over the telephone connection wire;

(b) a signal receive path comprising:

a second analog-to-digital converter for converting the reception signal received via the telephone connection lead into a digital reception signal,

a digital low pass filter for filtering the digital speech received signal from said digital received signal,

a digital high pass filter for filtering the digital data received signal from said digital received signal, and

A second digital-to-analog converter for converting the filtered digital voice reception signal into an analog voice reception signal.

(c) having a first hybrid circuit for sending analog transmit signals to and receiving analog receive signals from the telephone connecting conductors,

(d) have a second hybrid circuit that sends an analog voice reception signal to the ISDN connecting wire (38), and sends the analog voice signal received by the ISDN-connecting wire (38) to the first analog/digital converter (59) .

The digital splitter according to the invention has the advantage that existing ISDN terminals for telephone voice signals can be enlarged to carry high frequency data signals, such as XDSL data signals.

The digital high-pass and low-pass filters included in the digital splitter according to the invention ensure that the transfer characteristics of the digital splitter remain unchanged over long periods of time.

A further advantage is that, by using digital filters, very high-order filters with very good filtering properties can be realized without high circuit engineering costs.

The filter coefficients of the digital low-pass and high-pass filters of the digital filter according to the invention are preferably adjustable or programmable.

This offers the particular advantage that the digital separator according to the invention can be used in a simple manner for different applications,

The speech signal preferably relates to a low-frequency ISDN telephone speech signal.

The data signal is preferably a high-frequency xDSL data signal, especially an ADSL data signal.

Preferably there is additionally no analog low-pass filter for low-pass filtering the analog voice transmission signal.

Preferably, a second analog low-pass filter is additionally provided for low-pass filtering the analog speech reception signal.

The digital high pass filter is preferably connected to an xDSL data modem.

The xDSL data modem is preferably an ADSL modem.

In a particularly preferred embodiment of the digital splitter, a parallel voltage regulation circuit is provided which supplies a DC voltage to the telephone connection line as a function of the supply voltage received from the ISDN connection line.

In another particularly preferred embodiment of the digital splitter, a bypass circuit is provided which connects the ISDN connection line to the telephone connection line when the supply voltage of the digital splitter is interrupted.

In this case, the bypass circuit preferably has: a first controllable changeover switch for switching the telephone connection line between the first hybrid circuit of the digital splitter and a bypass line; a second controllable a changeover switch for switching the connection of the ISDN connection conductors between the second hybrid circuit of the digital splitter and a bypass conductor; and a control circuit which connects the two changeover switches to the on the bypass wire.

Preferably, the digital splitter is also provided with a signal amplifier for amplifying the analog transmit signal and the analog receive signal.

Description of drawings

A preferred embodiment of the digital separator according to the invention will be described below with the aid of drawings which illustrate the essential features of the invention.

Attached are:

Figure 1: A telephone exchange connected to several subscribers, in which an analogue splitter according to the prior art is provided;

Fig. 2: A circuit block diagram of a conventional analog splitter according to the prior art;

Fig. 3: the circuit block diagram of digital splitter according to the present invention;

Fig. 4: according to a particularly preferred embodiment of the digital splitter of the present invention, it has a voltage regulating circuit and a bypass circuit;

FIG. 5 : Circuit design of the hybrid circuit used in the digital splitter according to the invention.

Detailed ways

Fig. 3 shows a block circuit diagram of a digital splitter 1 according to the invention. The digital splitter 1 has a first signal terminal 2 connected to the two-core telephone terminal connection wire and a second signal terminal 3 connected to the two-core telephone terminal connection wire and the ISDN terminal. A telephone connection line 4 for a subscriber can be connected via the first signal terminal 2 . The signal terminal 2 is connected via a line 5 to a terminal 6 of a hybrid circuit 7 . The hybrid circuit 7 performs double-core-four-core signal conversion. The hybrid circuit 7 has a signal output 8 which is connected via a line 9 to the input of an analog/digital converter 11 . The mixing circuit 7 outputs a mixed signal received by the telephone connecting wire 4 to the analog/digital converter 11 through the wire 9, the mixed signal includes a low-frequency voice signal and a high-frequency data signal, and the analog/digital converter 11 collects analog signals and Convert it into a digital data signal. The digital data signal is output via an output 12 to a digital data line 13 which is split into a digital data line 15 and a digital data line 16 at a branch node 14 . The digital data line 15 is connected to the input 17 of a digital high-frequency filter 18 , the output 19 of which is connected via a line 20 to the output terminal 21 of the digital splitter 1 .

The data line 16 is connected to an input 22 of a digital low-frequency filter 23 whose output 25 is connected to a signal input 26 of a digital/analog converter 27 . An analog output 28 of the digital/analog converter 27 is connected via a signal line 29 to an input 30 of an analog low-pass filter 31 . The analog low-pass filter 31 has a signal output 32 which is connected via a signal line 33 to an input terminal 34 of a mixing circuit 35 . The hybrid circuit 35 has a signal terminal 36 which is connected via a line 37 to the second signal terminal 3 of the digital splitter 1 .

The second signal terminal 3 of the digital splitter 1 is connected to the signal terminal 39 of a hybrid circuit 40 via a two-core telephone terminal connecting line 38, which has a signal input 41 which is connected via a line 42 to the signal terminal 39 of the hybrid circuit 40. An output 43 of a digital/analog converter 44 is connected. The hybrid circuit 40 also has a signal output 45 which is connected via a signal line 46 to a signal input 47 of an analog/digital converter 48 . Digital-to-analog converter 44 receives digital voice signals from an ISDN data processing circuit 50 via data conductor 49 . The A/D converter 48 outputs the digital voice data to the ISDN data processing circuit 50 via the data conductor 51 . The ISDN data processing circuit 50 is located, for example, in a telephone exchange and is connected to a data transmission network. The mixing circuit 35 has a signal output 52 which is connected via a data line 53 to a signal input 54 of an analog low-pass filter 55 . The low-pass filter 55 has a signal output 56 for outputting the filtered analog signal via a signal line 57 to a signal input 58 of an analog/digital converter 59 . The digital signal converted by this analog/digital converter 59 is output to the input terminal 62 of a digital low-pass filter 63 through the output terminal 60 of this analog/digital converter 59 and a data lead 61, and this low-pass filter makes receiving The received data digital signal is low-pass filtered and output through an output terminal 64. The output 64 of the digital low-pass filter 63 is connected via a line 65 to a first input 66 of an adder 67 . The adder 67 has a further input 68 which is connected via a line 69 to an output 70 of a digital high-pass filter 71 . The digital high-pass filter 71 has an input 72 which is connected via a line 73 to an input terminal 74 of the digital splitter 1 . An ADSL modem 75 can be connected to the digital splitter 1 via terminals 21 , 74 and signal lines 76 , 77 .

The adder 67 has an output 78 which is connected via a line 79 to a signal input 80 of a digital/analog converter 81 . The digital/analog converter 81 has an analog signal output 82, which is connected via a signal line 83 to a signal input 84 of an analog low-pass filter 85. The analog low-pass filter 85 has a signal output 86 which is connected via a signal line 87 to a signal input 88 of the hybrid circuit 7 .

The two digital low-pass filters 23 , 63 and the two digital high-pass filters 18 , 71 together with the adder 67 form a digital filtering device 89 in the digital splitter 1 .

A digital splitter according to the present invention, as shown in FIG. 3, includes a signal transmission path and a signal reception path. In the signaling path, the analog voice transmission signal to be transmitted is converted into a digital voice transmission signal and added to an analog transmission signal with a transmitted digital data transmission signal.

The digital voice transmission signal output by the ISDN data processing circuit 50 through the wire 49 is converted into an analog voice transmission signal in the D/A converter 44, and passes through the mixing circuit 40 to the mixing circuit 35 included in the digital splitter 1. The mixing circuit 35 outputs the transmitted analog ISDN voice transmission signal to an analog low-pass filter 55 through a wire 53 . The analog low-pass filter 55 filters out the low-frequency analog ISDN voice signal to be sent, wherein the filtered analog voice signal is then converted into a digital voice transmission signal by the post-connected analog/digital converter 5. A re-digitization of the voice transmission signal, as output by the ISDN data processing circuit 50 , therefore takes place in the digital separator 1 according to the invention. Since the redigitized speech transmission signal is present digitally in the analog/digital converter 59 , it is combined with the already digitally present data signal by means of digital filters 63 , 71 . The transmitted digital signal output by the data modem 75 via the line 76 is a digital signal which reaches the input 72 of the digital high-pass filter 71 via the internal line 73 of the digital separator 1 . The low-frequency digital speech signal is filtered in a digital low-pass filter 63 and the high-frequency data signal, which is already present in digital form, is filtered in a digital high-pass filter 71 .

The ISDN data processing circuit 50 is a conventional ISDN data processing circuit such as is already present in large numbers in individual telephone exchanges. Due to the switching configuration of the digital splitter 1 according to the invention, it is possible that the existing ISDN data processing circuit 50 remains unchanged in terms of circuit technology. This is possible because the analog speech signal output by the mixing circuit 40 is changed back to the original digital form by the digital separator 1 according to the invention. The existing ISDN terminal can thus be extended in a simple manner to be connected to an ADSL data processing circuit.

In the receive signal path, an analog receive signal is received via the telephone connection line 4, which signal comprises both low-frequency speech signals and high-frequency data signals, which is converted into a digital receive signal by means of an analog/digital converter 11 and transmitted via line 13 to Branch node 14. The digital receive signal is branched and thus connected both to input 17 of digital high-pass filter 18 and to input 22 of digital low-pass filter 23 .

The digital high-pass filter 18 filters out the high-frequency digital data receiving signal component from the incoming digital receiving signal, and outputs the digital data receiving signal to the data modem 75 through the wire 20 , the output terminal 21 and the wire 77 .

The digital low-pass filter 23 filters out low frequency digital speech received signal components from the incoming digital received signal. The digital voice reception signal filtered out will be sent to the rear digital/analog converter 27 through the wire 25, and the digital/analog converter converts the digital voice reception signal into an analog voice reception signal, and the signal is passed through the rear low pass Filters are additionally analog filtered. The filtered analog voice reception signal passes through the hybrid circuit 35 and the hybrid circuit 40 to the A/D converter 48, which converts the analog voice reception signal into a digital voice reception signal and outputs it to the ISDN data processing circuit 50.

In a preferred embodiment, the filter coefficients of the digital low-pass filter 23 , 63 and the digital high-pass filter 18 , 71 of the filter device 89 are adjustable. In this case, either the filter coefficients are generated by a filter coefficient generating means or are stored in non-programmable memory means. The digital filter device 89 is preferably a high-order digital filter, which is highly selective and only slightly increases the circuit-technical outlay compared to a low-order digital filter. The transmission performance of the digital filter included in the filtering device is stable and remains constant over time.

The different individual units of digital splitter 1 are supplied with supply voltage U _V via supply voltage line 90 .

The digital splitter 1 according to the invention can be used both on the subscriber side and on the telephone exchange side.

The digital splitter 1 shown in FIG. 3 has a digital core in the form of a digital filter device 89 and an analog circuit part consisting of mixing circuits 7, 35 and analog filters 31, 55, 95. The interface between the digital circuit part and the analog circuit part is composed of D/A converters 81, 27 and D/A converters 11, 59. Furthermore, the digital splitter 1 according to the invention shown in FIG. 3 preferably has a signal amplifier for amplifying the analog transmit signal and the received analog receive signal.

FIG. 4 shows a particularly preferred embodiment of the digital splitter 1 according to the invention, to which a voltage regulation circuit and a bypass circuit are additionally expanded. The feed from the telephone exchange to the ISDN terminals of the subscribers is usually connected via telephone connection lines to a corresponding voltage supply circuit comprising a DC voltage source.

In an embodiment of the digital splitter 1 according to the invention shown in FIG. 4, a parallel voltage regulation circuit 91 is provided. The voltage regulation circuit 91 has a signal input 92 which is connected via a line 93 at a node 94 to a signal line 94 which is connected to the second signal terminal 3 . The voltage regulation circuit 91 also has a signal output 95 which is connected via a line 96 at a node 97 to a signal line 98 which is connected to the first signal terminal 2 of the digital splitter 1 . The signal line 98 is connected to a switching output 99 of the controllable changeover switch 100 . The controllable changeover switch has a second output 101 which is connected via a line 102 to an output 103 of a second changeover switch 104 . The other output terminal 105 of the controllable changeover switch 104 is connected to the signal line 94 . The controllable changeover switch 104 has an output 106 which is connected via a line 38 to the mixing circuit 40 . The signal input terminal 107 of the other controllable switch 100 is connected to the telephone connection line 4 . The two controllable changeover switches 100 , 104 are each connected via control lines 108 , 109 to a control circuit 110 . The control circuit 110 of the digital splitter 1 is supplied with supply voltage U _V via a supply voltage line 111 .

In the normal operating state, the two controllable changeover switches 100 , 104 are connected in such a way that the inputs 106 , 107 of the changeover switches 100 , 104 are connected to the signal terminals 2 , 3 of the digital splitter 1 . The voltage regulation circuit 91 connected in parallel supplies a DC voltage into the telephone connection line 4 depending on the voltage received by the ISDN connection line 38 .

After interruption of the supply voltage UV, the control device 110 controls the changeover switches 100, 104 via the control lines 108, 109 in such a way that they are switched over to the switch outputs 101, 103, so that the telephone connection line 4 is directly connected to the ISDN via the line 102 The wires 38 are short-circuited. It is thus achieved that the supply current is conducted through the bypass or bypass circuit. This bypass circuit enables ISDN signals to be bypassed around the digital splitter 1 in the event of a digital splitter failure due to a power interruption. The two bypass switches 100, 104 may not be used if the active hybrid circuit arrangement becomes highly resistive in the event of a current interruption or disturbance.

FIG. 5 shows the circuit structure of the mixing circuits 7, 35 and the mixing circuit 40 included in the digital separator 1 according to the present invention. The hybrid circuit includes a transducer or transformer 112 having a primary winding 112a and a secondary winding 112b. The primary winding 112a of the transformer 112 is connected to the terminals 113, 114 of the hybrid circuit. The hybrid circuit is connectable via terminals 113, 114 to any twin-conductor or telephone connection. The hybrid circuit also includes a symmetrical filter mechanism 115 consisting of six resistors 116 to 121 . The filter unit 115 is connected between the secondary winding 112 b of the transformer 112 and the signal outputs 122 , 123 of a fully differential operational amplifier 124 . The signal input 125 of the operational amplifier 124 is connected via a signal line 126 to a signal terminal 127 for a twin-conductor line. The filter unit 115 is also connected via lines 128 , 129 to an analog/digital converter 130 whose output is connected via a line 131 to a digital signal output 132 of the hybrid circuit. The hybrid circuit shown in FIG. 5 is used for signal conversion between twin-conductors and signal transmission and reception paths consisting of twin-conductors.

Claims (13)

1. A digital separator having (a) A signaling path comprising: A first analog/digital converter (59), for converting the analog voice signal to be sent into a digital voice signal, A digital low-pass filter (63), used for low-pass filtering the digital voice signal, A digital high-pass filter (71), for carrying out high-pass filtering to a digital data signal, A summation circuit (67), used for adding the digital speech signal of low-pass filtering and the digital data signal of high-pass filtering into digital transmission signal, and a first digital-to-analog converter (81) for converting said digital transmission signal into an analog transmission signal to be transmitted via the telephone connecting wire (4); (b) a signal receive path comprising: a second analog-to-digital converter (11) for converting the reception signal received via the telephone connection lead (4) into a digital reception signal, a digital low-pass filter (23) for filtering out digital speech received signals from said digital received signals, a digital high-pass filter (18) for filtering the digital data received signal from said digital received signal, and A second digital-to-analog converter (27) for converting the filtered digital voice reception signal into an analog voice reception signal. (c) having a first mixing circuit (7) for sending an analog transmit signal to the telephone connection conductor (4) and for receiving an analog receive signal from the telephone connection conductor (4), (d) have a second hybrid circuit that sends an analog voice reception signal to the ISDN connecting wire (38), and sends the analog voice signal received by the ISDN-connecting wire (38) to the first analog/digital converter (59) (35). 2. The digital separator according to claim 1, characterized in that: the filter coefficients of the digital low-pass filter (23, 63) and the digital high-pass filter (18, 71) are adjustable. 3. Digital separator according to claim 1 or 2, characterized in that said voice signal is a low frequency ISDN telephone voice signal. 4. A digital splitter according to claim 1, characterized in that said data signal is a high frequency XDSL data signal. 5. A digital splitter according to claim 4, characterized in that said data signal is a high frequency ADSL data signal. 6. The digital splitter according to claim 1, characterized in that: a first analog low-pass filter (55) is provided for low-pass filtering the analog voice transmission signal, wherein the first analog low-pass filter (55) connected in front of said first analog-to-digital converter (59). 7. according to the digital splitter of claim 1, it is characterized in that: be provided with the second analog low-pass filter (31), be used for carrying out low-pass filtering to analog voice receiving signal, wherein, this second analog low-pass filter (31) connected after said second digital/analog converter (27). 8. A digital splitter according to any one of the preceding claims, characterized in that the digital high-pass filter (71) of the signal transmit path and the digital high-pass filter (18) of the receive signal path are connected to An XDSL data modem (75). 9. A digital splitter according to claim 8, characterized in that said XDSL data modem (75) is an ADSL modem. 10. The digital splitter according to claim 1, characterized in that a parallel voltage regulation circuit (91) is provided which supplies a DC voltage to the telephone connection conductor ( 4) in. 11. According to claim 10 digital splitter, it is characterized in that: be provided with a bypass circuit, it connects ISDN connecting line (38) to telephone connecting line ( 4) on. 12. The digital splitter according to claim 11, characterized in that: the bypass circuit has: a first controllable changeover switch (100) for connecting the telephone connection wire (4) to the digital splitter (1) The first hybrid circuit (7) and a bypass wire (102) are switched and connected; the second controllable switch (104) is used to connect the ISDN connecting wire (38) to the second wire of the digital splitter (1). a switching connection between the hybrid circuit (34) and a bypass line (102); and a control circuit (110) which switches the two switching switches (100, 104) is connected to the bypass wire (102). 13. The digital splitter as claimed in claim 1, characterized in that a signal amplifier is additionally provided for amplifying the analog transmit signal and the analog receive signal.

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