Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B3/00—Line transmission systems
  • H04B3/02—Details
  • H04B3/04—Control of transmission; Equalising
  • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/04—Distributors combined with modulators or demodulators
  • H04J3/047—Distributors with transistors or integrated circuits
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
  • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
  • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
  • H03K17/62—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors
  • H03K17/6285—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors with several outputs only combined with selecting means
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/14—Monitoring arrangements

Definitions

• the present invention relates to a demultiplexer, a protection switch unit which includes one such demultiplexer, a telecommunications network which includes one such protection switch unit, and a method relating to demultiplexing. More specifically, the invention relates to the aforesaid apparatus and method in respect of demultiplexing signals that are single-mode or differential-mode signals and preferably of the CMI type at transmission speeds above about 100 Mbit/s and preferably in the range of about 140-155 Mb/s.
• the network includes at least one protection switch unit which includes a demultiplexer whose outputs are connected to the signal lines and whose input is connected to the reserve terminal access unit.
• the exchange sends to the demultiplexer of the protection switch unit output signals which are intended for the signal line connected to the unusable normal terminal access unit via the reserve terminal access unit, said demultiplexer being controlled to forward the output signal to said signal line.
• Good signal quality is required when switching or demulti-ple- . xing signals having transmission speeds in the region of about 140-155 Mb/s.
• the pulse shape of the output signal is often required to be the same as the pulse form of the input signal.
• bit rates of up to about 30 Mb/s
• line impedances, connections, terminations, line runs and component data place strict requirements on circuitry.
• conductor impedances In order to keep conductor impedances as constant as possible, it is necessary to take particular care in implementing the printed board assembly.
• circuitry using standard circuits in a demultiplexer is expensive and highly current consuming.
• US-A 5,146,113 describes an integrated circuit having several narrow, elongated resistance strips on a circuit board, to provide a board-mounted circuit with a predetermined input and/or output impedance.
• One object of the present invention is to provide a method of selecting one of several outputs as the output of a received input signal when demultiplexing, therewith obtaining good signal quality in a simple and inexpensive manner at the same time.
• This object is achieved with a method in which an input signal received on an input is first conducted to a first transmission line and thereafter selectively to one of at least two outputs.
• Another object of the invention is to provide a method of selecting one of several outputs as the output of a received input signal when demultiplexing, and of enabling a signal transferred to one of the outputs to be monitored in a simple manner.
• This object is achieved with a method which also includes generating a replica of the signal forwarded to a selected output by, at the same time, conducting the input signal that was passed to the selected output to a third transmission line.
• a further object of the invention is to provide a method of selecting one of several outputs as the output for a received input signal when demultiplexing, where distortion in the signal obtained on the selected output and on the replica of this signal can be reduced readily in a later stage.
• This object is realized with a method in which the input signal- includes two parts and the two parts of said input signal are each conducted to a respective first and second transmission line and thereafter selectively conducted to a respective first and second connection point in a selected output and also to a respective third and fourth transmission line.
• Still another object of the present invention is to provide a demultiplexer, a protection switch unit including one such demultiplexer, and a telecommunications network which includes one such protection switch unit, where good signal quality is obtained in a simple and inexpensive manner when selecting one of several outputs as the output for a received input signal.
• demultiplexer includes an input and at least two outputs, wherein a connection point in the input is connected to a first transmission line to which a first connection point in each output is connected via a respective first controllable signal forwarding conductor means.
• Yet a further object of the invention is to provide a demultiplexer, a protection switch unit which includes one such demultiplexer, and a telecommunications network which includes one such protection switch unit, wherein the function of the demultiplexer and the function of the unit connected to the input of the demultiplexer can be readily monitored.
• each first signal forwarding conductor means is connected to a third transmission line.
• Still yet a further object of the invention is to provide a demultiplexer, a protection switch unit that includes one such demultiplexer and a telecommunications network that includes one such protection switch unit, wherein distortion obtained in output signals from the demultiplexer can be readily reduced in later stages.
• This object is achieved with a demultiplexer, a protection switch unit and a telecommunications network wherein a second connection point in the demultiplexer input is connected to a second transmission line which, in turn, is connected to a second connection terminal in each output via a respective second controllable signal forwarding conductor means, which may optionally also be connected to a fourth transmission line.
• Fig. 1 is a block schematic of an inventive telecommunications system
• Fig. 2 is a circuit diagram of an inventive demultiplexer.
• Fig. 1 is a block schematic of a telecommunications system which operates with CMI signals transmitted at transmission speeds in the range of about 140-155 Mb/s.
• Each protection unit 2 is connected to the exchange 1 via a respective terminal access unit 3 (TAU) , of which only eight are shown although these units will actually be sixteen in number.
• TAU terminal access unit 3
• This protection switch unit is connected to each protection unit 2.
• the main duty of the protection units 2 is to convert single-mode signals incoming to the protection switch unit 4 into differential-mode signals, and to convert differential- mode signals outgoing from the exchange 1 via the terminal access units 3 and the protection switch unit 4 to single-mode signals.
• the protection switch unit 4 includes a multiplexor or selector and a demultiplexer. The multiplexor functions to receive all of the signals incoming on the conductors and to selectively forward one of said signals, and the demultiplexer functions to receive a signal outgoing from the exchange 1 and to forward this signal to a selected signal conductor.
• Fig. 2 illustrates an embodiment of an inventive demultiplexer, wherein only two outputs are shown for the sake of simplicity, although it will be understood that the demultiplexer will normally include many more outputs.
• a first of the outputs has a first and a second connection point 0UT1+ and OUT-.
• the first connection point 0UT1+ of the first output is connected to a first signal forwarding conductor means Ql via a resistor Rl, said means Ql being connected to an RF transistor in the illustrated case.
• the resistor Rl is connected to the emitter of the transistor Ql in the illustrated case.
• the transistor base is connected via a resistor R8 to a first transmission line TLINE_1.
• One end of the transmission line TLINE_1 is terminated with a resistor R5 which is connected to a voltage source VBB.
• the transistor collector is connected to a third transmission line TLINE_3 included in the demultiplexer circuit board, said third transmission line being terminated at both ends with respective resistors R13 and R12 connected to a voltage source VCC, said voltage source optionally being the same as VBB.
• a first connection point SUP+ is provided in an output for monitoring signals at one end of the third_ transmission line TLINE_3.
• the second connection point OUTl- of the first input is connected to a second transmission line TLINE_2 mounted on the demultiplexer circuit board via a resistor R3, and RF transistor Q4 and a further resistor RIO, similar to the first connection point OUT1+.
• One end of the TLINE_2 is terminated with a resistor R6 which is connected to the voltage source VBB.
• the collector of the transistor Q4 is connected to a fourth transmission line TLINE_4 mounted on the demultiplexer circuit board, this fourth transmission line being terminated with a resistor R14 at one end and a resistor R7 at the other end in a manner similar to the third transmission line TLINE_3, said resistors being connected to the voltage source VCC.
• a second connection point in the monitoring signal output is obtained at one end of the fourth transmission line TLINE_4.
• Respective emitters of the first and second transistors Ql and Q4 are connected to one end of a first externally controlled switch means SI via a resistor R29 and R31 respectively.
• the other end of the switch SI is connected to earth.
• connection points OUT2+ and 0UT2- of a second output are connected to the first and the second transmission lines
• TLINE_1 and TLINE_2 respectively in exactly the same way, via a resistor R2, a transistor Q2 and a resistor R9, and via a resistor R4, a transistor Q3 and a resistor Rll.
• Respective collectors of the transistors Q2 and Q3 are connected to the third and the fourth transmission lines TLINE_3 and TLINE_4 respectively.
• Respective emitters of the transistors Q2 and Q3 are connected to a second externally controlled switch S2 via resistors R30 and R32 in exactly the same way as the first output, said switch S2 also being connected to earth similar to the switch SI.
• transistors Ql, Q2, Q3 and Q4 and associated components are so placed along the transmission lines TLINE_1, TLINE_2, TLINE_3 and TLINE_4 that mismatches and reflexions will be minimal.
• further transistors for further outputs are correspondingly placed along said transmission lines TLINE_1, TLINE_2, TLINE_3 and TLINE_ .
• a differential amplifier D_AMP has one output and is connected to the first transmission line TLINE_1 at a first connection point +0 therein and to the second transmission line TLINE_2 at a second connection point -0.
• the amplifier D_AMP has an input having two connection points +1 and -I which are each connected to a respective connection point IN+ and IN- in the input.
• Resistors that terminate the ends of respective first and second transmission lines TLINE_1 and TLINE_2 where the amplifier D_AMP is connected are included in this amplifier and are also connected to the source VBB, which is also included in the amplifier D_AMP at this end of the transmission lines and is not therefore shown in the Figure.
• each of the transmission lines TLINE_1, TLINE_2, TLINE_3 and TLINE_4 has the form of a microstrip included in the board circuitry and to which the transistors are connected.
• These microstrips are preferably rectilinear, have identical lengths and are essentially of unitary width.
• An important feature of this embodiment, however, is that the two transistors at each output have equally long paths to the connection points +0 and -0 in the output of the amplifier D_AMP.
• the transmission lines TLINE_1, TLINE_2, TLINE_3 and TLINE_4 may optionally be slightly narrower at those points where the transistors are connected, so as to match the impedance of a microstrip to the additional capacitance that is supplied by a passive transistor.
• the impedances of respective transmission lines can be matched to the capacitances of the passive transistors by choosing the value of the terminating resistors R5, R6, R7, . R12, R13 and R14 to correspond to the transmission lines having the additional distributed capacitances that the transistors supply.
• transmission lines are parallel plane lines (stripline) disposed in intermediate layers of the circuit board.
• This transmission line embodiment would require the transistors to be connected to said lines by means of bushings or throughlets, which would make the matching problem slightly more difficult to resolve than when the transistors are connected to a microstrip.
• the inputs and outputs of the demultiplexer are often arranged in the form of parallel plane lines that extend through the interior of the circuit board.
• the demultiplexer illustrated in Fig. 2 functions with differential-mode signals, which results in less distortion in the signals leaving the demultiplexer.
• the demultiplexer operates as follows: An input signal is received on the input IN+, IN- and amplified to an appropriate level in the amplifier D_AMP. The amplified input signal is forwarded to a selected output by the first and the second transmission lines TLINE_1, TLINE_2. The amplification of the amplifier D_AMP is chosen so as to essentially compensate for subsequent losses due to output impedance and load.
• One of the outputs is activated by the first externally controlled switch SI, which activates the transistors Ql and Q4 connected to the input when said input is closed.
• the second input is passive, i.e. the second switch S2 is off.
• the switches may comprise any one of a number of different designs known to the person skilled in this art, for instance transistors.
• the switches SI and S2 are controlled by a control circuit arranged in the protection switch unit and functioning to close a switch depending on which of the aforesaid terminal access units is inoperative. This switching function may also be accomplished directly from the aforesaid exchange.
• Closing of the switch SI results in biassing of the transistors Ql and Q4 and the amplified input signal is conducted from the transmission lines TLINE_1 and TLINE_2 through the transistors Ql and Q4 and to the connection points OUT1+ and OUT1- in the first output.
• the demultiplexer is adapted to conduct an output signal also to the third and the fourth transmission lines TLINE_3 and TLINE_4 immediately when the output signal is obtained on an output. This means that a replica of the input signal is also obtained. This replica is obtained on the connection points SUP+, SUP- of the monitoring output and is processed in a monitoring circuit, which may be included in the protection switch unit.
• the demultiplexer may also include a second differential amplifier for amplifying the monitoring signal. It can be established whether or not the reserve access unit is broken or not, by analyzing this signal. An analysis of the signal will also reveal whether or not the '' demultiplexer is working in the manner intended. This represents a saving in the additional monitoring circuits that would otherwise be required.
• the connection of the transmission lines means that any reflexions therein will be quickly extinguished.
• the trans- mission lines are arranged so that the third and the fourth transmission lines TLINE_3 and TLINE_4 have roughly half the impedance of the first and the second transmission lines TLINE_1 and TLINE_2. This is achieved by virtue of selecting the width of the transmission lines and their respective distances to the earth plane. As a result of such selection, the collector voltage on a transistor will be lower than the emitter and the base voltage. Crosstalk from collector to base will therefore have only a very slight influence on signal quality. A certain degree of crosstalk may occur in the reverse direction, from base to collector, but the quality of the monitoring signal is not equally as important as the quality of the output signal.
• the transistor Since the collector voltage is low in comparison with the base and emitter voltage, the transistor can be considered as an emitter follower. This gives a high input impedance and therewith has little influence on the first and the second transmission lines TLINE_1 and TLINE_2, which has only a slight effect on the pulse shape.
• the amplifier D_AMP may alternatively be connected to the opposite end of the first and the second transmission lines TLINE_1 and TLINE_2.
• the monitoring signal output may also be placed at the opposite end of the third and fourth transmission lines TLINE 3 and TLINE 4.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
• Time-Division Multiplex Systems (AREA)
• Use Of Switch Circuits For Exchanges And Methods Of Control Of Multiplex Exchanges (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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• 1995
  • 1995-06-01 SE SE9502010A patent/SE504533C2/sv not_active IP Right Cessation
• 1996
  • 1996-05-24 WO PCT/SE1996/000679 patent/WO1996038943A1/en not_active Application Discontinuation
  • 1996-05-24 CA CA002222624A patent/CA2222624A1/en not_active Abandoned
  • 1996-05-24 AU AU60196/96A patent/AU705430B2/en not_active Ceased
  • 1996-05-24 EP EP96917759A patent/EP0873609A1/en not_active Withdrawn
  • 1996-05-24 KR KR1019970708356A patent/KR19990021881A/ko not_active Application Discontinuation
  • 1996-05-24 CN CN96195662A patent/CN1191642A/zh active Pending
  • 1996-05-24 JP JP8535995A patent/JPH11507480A/ja active Pending

Non-Patent Citations (1)

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