JP2001119256A - Filter for splitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filter for a splitter which improves a return loss characteristic and has a high performance filter characteristic. SOLUTION: This filter for a splitter to separate a voice signal from a digital signal is provided with resonance circuits 11 and 11' which generate resonance in a voice signal pass band and damping resistances R1 and R1', compensates for the gain of a signal component lost at the high pass side of the voice signal pass band and improves the frequency characteristic in the voice signal pass band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention mainly relates to xDSL.
(Digital subscriber line),
The present invention relates to a telephone line splitter filter suitable for separating and synthesizing an analog voice signal and a digital data signal.

[0002]

2. Description of the Related Art Conventional xDSL (digital subscriber)
The filter for the splitter used for the telephone line used for (line) will be described. Here, xDSL (x
Digital Subscriber Line (ADSL)
tric Digital Subscriber Line) and RADSL (Rate Adaptive Asymmetric D) derived from its ADSL.
Digital Subscriber Line) and HDSL (High
data rate DigitalSubscriber Line), VDSL
(Very High Speed Digital SubscriberLine),
SDSL (Symmetric Digital Subscriber Line)
This is a communication technology for performing high-speed data communication using an existing telephone line (copper twisted pair line).

[0003] The xDSL has attracted attention as a technology to compete with ISDN at present, as the demand for high-speed data communication is increasing due to the recent development of data communication networks represented by the Internet. Among them, ADSL is a DS that makes the downlink communication speed faster than the uplink communication speed.
L communication method. Details are described in ANSI Recommendation T.
1-413. To explain ADSL in brief, current analog telephone lines use 0 to 4 kHz.
While only using up to about z voice bands,
In ADSL, high-speed digital data communication is enabled using a higher frequency band.

In ADSL communication, ADSL modems are provided at both ends of a subscriber line connecting a telephone station and a subscriber's house. This ADSL modem is a data modulation and demodulation device for performing ADSL communication, and is characterized by handling a higher frequency than a normal analog modem.

When an ADSL modem is connected to an existing subscriber line, a POTS (Plain Old Telepho) is used to separate and synthesize an analog voice signal and a digital data signal.
ne Service) A splitter is used. In addition, POTS
The term refers to a conventional analog telephone line service or a low frequency band of about 0 to 4 kHz used for analog communication.

[0006] The splitters are attached to both ends of a telephone line, one is connected as an audio signal to an existing telephone or exchange, and the other is connected to an ADSL modem. By making such a connection, data communication via the ADSL modem is always possible regardless of the communication state of the analog telephone.

Conventionally, this telephone line splitter filter
In this case, a passive filter as shown in FIG.
What had been used was used. Conventional telephone line switch
The splitter filter (passive filter) is an inductor
L₄, L₄’, L₅, L₅’, L₆, L₆’Capacitor
C₄, C₅, C₆, Resonance capacitor C₇, C₇’,
C ₈, C₈’, And the cutoff frequency is
(200Hz-4kHz), about 8kHz which is about twice as large
In general, a filter design method with edges is used.

The telephone line splitter filter (passive filter) according to the conventional design method configured as described above has resonance capacitors C ₇ , C ₇ ′, C ₈ , and C ₈ ′.
To secure the attenuation.

[0009]

However, the splitter filter used in the above-mentioned conventional telephone line cannot obtain good return loss characteristics. Hereinafter, the reason will be described with reference to FIGS.

FIG. 3 shows the G.99 in the ITU-T standard.
2.1 (G.dmt) Annex EE.4 This is a return loss evaluation system defined as Type4. In this return loss evaluation system, ZNL-x21 is a general term for ZNL-c (station side) and ZNL-r (subscriber side) as pseudo impedance of a telephone line, and ZHP-x2
1 is a general term for ZHP-c (station side) and ZHP-r (subscriber side) as pseudo impedance of the ADSL modem.

Here, in the conventional filter design, the cutoff frequency is set to 8 times, which is about twice the pass band of the audio signal.
kHz.

In such a design method, ZNL-x21
Is a composite impedance having frequency characteristics as shown in FIG.
It was difficult to satisfy the ITU-T standard.

The above description is based on "IEEE JOURNAL ON SELECTED
AREASINCOMMUNICATIONS, VOL.13, NO.9, DECEMBER 199
ADSL and VADSL Splitter D
esignand Telephony Preformance (by John Cook
and Phil Sheppard).

Accordingly, it is an object of the present invention to provide a splitter filter having improved return loss characteristics and high performance filter characteristics.

[0015]

SUMMARY OF THE INVENTION A filter for a splitter according to the present invention has a cutoff frequency of an audio signal pass band (200 Hz to 4 kHz) for separating and synthesizing an audio analog signal and a digital data signal in xDSL.
In this case, the frequency is set to about 4 kHz, and the splitter filter has improved return loss characteristics.

Further, when the cutoff frequency is set to around 4 kHz, the frequency characteristic of the audio signal pass band is broken, but in order to improve this, a resonance circuit and a damping resistor are newly added to increase the gain. Compensated.

That is, the present invention is a splitter filter for separating an audio signal and a digital signal, wherein the splitter filter includes a resonance circuit that causes resonance in an audio signal pass band, and a damping resistor. This is a splitter filter that compensates for the gain of a signal component lost on the high frequency side of the audio signal pass band and improves frequency characteristics in the audio signal pass band.

The present invention also provides the splitter filter, wherein the splitter filter is configured in first and second signal lines, and the splitter filter is provided in the first and second signal lines. An inductor array connected to the second signal line, the inductor array having first, second, and third inductors connected in series from the input side; and an inductor array connected to the first signal line side. A first capacitor connecting a connection point of the first and second inductors connected to the first signal line and a connection point of the first and second inductors connected to the second signal line side; One end of a third inductor connected to the line side, not connected to the second inductor, and one end of a third inductor connected to the second signal line side, connected to the second inductor. A second capacitor connecting one end not connected to the second inductor, wherein the capacitor of the resonance circuit is connected in parallel to the second inductor on each of the first and second signal line sides. The damping resistor is a splitter filter connected in parallel to the second inductor on each of the first and second signal lines.

Further, according to the present invention, in the splitter filter, the first inductor is preferably in a range of 12.35 to 1.35.
The second inductor has a constant within a range of 2.85 to 3.15 mH, and the third inductor has a constant within a range of 3.65 mH.
The first capacitor has a constant in the range of 87.4-96.6 nF, and the second capacitor has a constant in the range of 75-11.025 mH. The capacitor has a constant in the range of 9 to 86.1 nF, and the capacitor constituting the resonance circuit is 3.70.
Has a constant belonging to the range of 5 to 4.095 μF,
The damping resistor is a splitter filter having a constant in the range of 48.45 to 53.55Ω.

Further, according to the present invention, the splitter filter is provided between the telephone line and the telephone so as to separate / synthesize the analog audio signal and the digital data signal in the xDSL telephone line. It is set to around 4 kHz with respect to the signal pass band (200 Hz to 4 kHz), and the characteristic attenuation of the filter generated in the cut-off frequency band and the polarity generated by the Chebyshev design method are used to reduce the mismatch attenuation (return loss) characteristics. I
G.992.1 (G.dmt) Annex of TU-T standard
This is a splitter filter that satisfies E E.4Type4.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A splitter filter according to an embodiment of the present invention will be described below.

FIG. 1 shows a circuit diagram of a splitter filter according to the present invention. The splitter filter of FIG. 1 is installed between a telephone line and a telephone. The splitter filter of FIG. 1 is used to separate and synthesize an audio analog signal and a digital data signal in ADSL.
This is a filter used as an OTS splitter.

The splitter filter according to the present invention comprises damping resistors R1 and R for adjusting the sharpness of the attenuation gradient of the passive filter section 10, the resonance circuit sections 11 and 11 '.
1 '.

In ADSL, a copper twisted pair wire composed of a pair of copper wires is used as a line. The two terminals on the right side of the filter shown in FIG. 1 are connected to each of the two copper wires. Hereinafter, for convenience of description, the two copper wires will be referred to as first and second signal lines, respectively.

The passive filter section 10 of the splitter filter according to the present embodiment is different from the conventional passive filter shown in FIG. 2 in that inductors L ₂ and L ₂ ′ located between the line side and the telephone set or the exchange side. Only a resonance circuit including the capacitors C ₂ and C ₂ ′ is provided. Further, the resonance circuit is provided with damping resistors R ₁ and R ₁ ′ for adjusting the sharpness of the inclination of the resonance attenuation.

As described above, the splitter filter used for telephone lines according to the present invention is used for a splitter for separating and synthesizing a voice analog signal and a digital data signal in xDSL.

When the cutoff frequency is designed to be higher than the pass band of the audio signal as in a conventional splitter filter for a telephone line, the return loss is about 5 to 7 dB.

That is, in the telephone line splitter filter of the present invention, the cut-off frequency is shifted from the conventional filter cut-off frequency designing method to the vicinity of the audio signal pass band.
It is configured such that the return loss characteristic is improved by utilizing the change in the characteristic impedance of the filter. As a design method for obtaining the circuit constant at this time, the circuit constant was designed using the polarity by the Chebyshev design method.

Referring to the above, a more specific configuration will be described. In the splitter filter according to the present invention, the cutoff frequency is shifted to the vicinity of the audio signal pass band to improve the return loss characteristics, and the cutoff frequency is shifted. The purpose of the present invention is to improve the specification crack of the frequency characteristic by using the resonance circuit and the damping resistor.

In addition to the above description, the circuit configuration of the splitter filter shown in FIG. 1 will be described in more detail.

The filter for a splitter according to the present invention has first and second
And between the first and second signal lines,
Inductors respectively connected in series to the second signal line
A first inductor in order from the input side.
L₁, L₁', The second inductor L₂, L₂’, The third
Inductor L₃, L₃’Are connected in series
And a first row connected to the first signal line side.
And the second inductor L ₁, L₂And the second connection point
First and second inductors L connected to the signal line side
₁’, L₂', The first capacitor C connecting to the connection point
₁And a third input connected to the first signal line.
Dacta L₃Not connected to the second inductor of
One end and a third input terminal connected to the second signal line side.
Nacta L₃'Connected to the second inductor
Second capacitor C connecting to one end ₃With
And a capacitor C constituting a resonance circuit.₂, C₂’
In each of the first and second signal lines,
The second inductor L₂, L₂’In parallel
And the damping resistance R₁, R₁’
In each of the first and second signal line sides, the second
Inductor L₂, L₂’In parallel,
That is, the split circuit connected in parallel to the resonance circuit.
It is a filter for data.

Further, according to the present invention, in the above-mentioned filter, the first inductor is preferably in a range of 12.35 to 13.65.
mH, the second inductor has a constant in the range of 2.85-3.15 mH, and the third inductor has a constant in the range of 9.975-1.
The first capacitor has a constant in a range of 1.025 mH, the first capacitor has a constant in a range of 87.4 to 96.6 nF, and the second capacitor has a constant in a range of 87.4 to 96.6 nF. The capacitor has a constant in the range of 9 to 86.1 nF, and the capacitor constituting the resonance circuit is 3.70.
Has a constant belonging to the range of 5 to 4.095 μF,
A filter is obtained, wherein the damping resistor has a constant belonging to the range of 48.45 to 53.55Ω.

Here, the range of the inductance of the first inductor is set to 12.35 to 13.65 mH.
If it is 3.65 mH or more, the cutoff frequency is too low, and if it is 12.35 mH or less, the cutoff frequency is too high.

The reason why the range of the inductance of the second inductor is set to the range of 2.85 to 3.15 mH is as follows.
Above 15 mH, the cutoff frequency is too low and 2.
This is because the cut-off frequency is too high at 85 mH or less.

The reason why the inductance of the third inductor is set in the range of 9.975 to 1.025 mH is as follows.
If the frequency is 1.025 mH or more, the cutoff frequency is too low, and if it is 9.975 mH or less, the cutoff frequency is too high.

The capacitance of the first capacitor is set to 8
The reason for setting the range of 7.4 to 96.6 nF is that at 96.6 nF or more, the cutoff frequency is too low, and at 87.4 nF or less, the cutoff frequency is too high.

The capacitance of the second capacitor is set to 7
The reason for setting the range of 7.9 to 86.1 nF is that if the frequency is 86.1 nF or more, the cutoff frequency is too low, and if it is 77.9 nF or less, the cutoff frequency is too high.

The reason why the capacitance of the capacitor constituting the resonance circuit is in the range of 3.705 to 4.095 μF is as follows.
At 4.095 μF or more, the set resonance frequency is 1.5 kHz.
This is because the frequency is too low with respect to z, and if it is 3.705 μF or less, the frequency is too high with respect to the set resonance frequency of 1.5 kHz.

The damping resistance is set to 48.45 to 5
The reason for setting the range to 3.55Ω is that if it is 53.55Ω or more, damping is too effective and the attenuation becomes large, and 48.4Ω or more.
If it is less than 5Ω, damping does not work and the resonance circuit becomes unstable.

As described above, in the splitter filter of this embodiment, the cutoff frequency is set to the audio signal pass band (2
00 Hz to 4 kHz) to improve the return loss characteristics and to provide a resonance circuit and a damping resistor for causing resonance in the audio signal pass band. Improvements are being made.

The effect of this improvement will be described by comparing a conventional passive filter (FIG. 2) with the filter according to the present embodiment (FIG. 1).

In the filter according to the present embodiment, L1 =
13 mH, L2 = 3 mH, L3 = 10.5 mH, C1 =
92 nF, C2 = 3.9 μF, C3 = 82 nF, R1 =
Table 1 below shows the measurement results when the resistance was set to 51Ω.

[0043]

[Table 1]

As can be understood from Table 1, although the above-mentioned circuit constants can be slightly varied,
The variation was within ± 5%.

Similarly, in the passive filter of the conventional example, the measurement result when the circuit constant of each component is set to the same value as the corresponding component in the splitter filter according to the present embodiment, Table 2 shows the results of comparison with the measurement results.

[0046]

[Table 2]

As shown in Table 2, it can be seen that the improved circuit configuration using the splitter filter of the present invention has improved gain over the entire voice passband as compared with the conventional circuit configuration.

[0048]

As described above, according to the present invention, it is possible to provide a splitter filter having improved return loss characteristics and high performance filter characteristics.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a splitter filter according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional passive filter.

FIG. 3 is an explanatory diagram of a return loss evaluation system in the ITU-T standard.

FIG. 4 is an explanatory diagram of pseudo impedance of the ADSL modem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Passive filter part 11, 11 'Resonance circuit part 31 Pseudo impedance of ADSL modem

Claims (4)

[Claims] 1. A splitter filter for separating an audio signal and a digital signal, wherein the splitter filter is provided with a resonance circuit that causes resonance in an audio signal pass band, and a damping resistor. A filter for a splitter, wherein the gain of a signal component lost on the high frequency side is compensated, and the frequency characteristic in an audio signal pass band is improved. 2. The splitter filter according to claim 1, wherein said splitter filter comprises first and second filters.
Between the first and second signal lines.
A series of inductors connected in series to the first signal line, respectively, the first, second, and third inductors being connected in series from the input side; and the first signal line A first capacitor connecting a connection point of the first and second inductors connected to the first side and a connection point of the first and second inductors connected to the second signal line side; And one end of a third inductor connected to the signal line side of the third inductor not connected to the second inductor, and one end of the third inductor connected to the second signal line side connected to the second inductor. And a second capacitor connecting one end of the first and second signal lines, wherein the capacitor constituting the resonance circuit is connected in parallel to the second inductor on each of the first and second signal line sides. Is Cage, the damping resistor, in each of the first and second signal line side, the second
A filter for a splitter, which is connected in parallel to the inductor of (1). 3. The splitter filter according to claim 1, wherein said first inductor is 12.3.
Has a constant belonging to the range of 5 to 13.65 mH,
The second inductor has a constant belonging to a range of 2.85 to 3.15 mH, and the third inductor has:
The first capacitor has a constant in the range of 9.975 to 1.025 mH, and the first capacitor has a constant in the range of 87.4 to 96.
The second capacitor has a constant belonging to a range of 77.9 to 86.1 nF, and the second capacitor has a constant belonging to a range of 77.9 to 86.1 nF.
It has a constant in the range of 3.705 to 4.095 μF, and the damping resistance is 48.45 to 53.55Ω.
Characterized in that the filter has a constant belonging to the range of 4. A splitter filter according to claim 1, which is installed between a telephone line and a telephone in order to separate and combine a voice analog signal and a digital data signal in an xDSL telephone line. And the cutoff frequency is set to around 4 kHz on the high frequency side of the audio signal pass band,
Utilizing the variation of the characteristic impedance of the filter generated in the cutoff frequency band and the polarity generated by the Chebyshev design method, the mismatch attenuation (return loss) characteristic is determined by ITU-
G.992.1 (G.dmt) of the T standard AnnexE
E. A filter for a splitter, which satisfies 4Type4.