CN1960420B - ADSL lowpass filter - Google Patents

Abstract

The ADSL low pass filter comprises a first filter circuit; a second filter circuit and a third filter circuit. The first filter circuit comprises: a first circuit with a first inductor, a first capacitor and a first resistor; and a second circuit with a paralleled second inductor, second capacitor and second resistor; wherein, the first circuit is connected to the second circuit in parallel. The second filter circuit comprises a first transformer. The third filter circuit is connected the first transformer and comprises: a third circuit comprising a parallel third capacitor, second transformer and fourth capacitor; a fourth circuit comprising parallel fifth capacitor and third resistor; a fifth circuit comprises parallel sixth capacitor and fourth resistor. Wherein, the third, fourth and fifth circuits are connected in parallel. The ADSL low pass filter also comprises seven capacitor connected to the fifth capacitor.

Description

The ADSL low pass filter

Technical field

The present invention relates to ADSL (Asymmetric Digital Subscriber Line, ADSL (Asymmetric Digital Subscriber Line)) low pass filter, particularly can meet the ADSL low pass filter of Britain Telecom's standard.

Background technology

ADSL is the popular broadband network services of generally using.ADSL uses the interphone line to come transmission signals usually, in order not allow the telephone signal of being transmitted on the signal interfering phone line of ADSL, the ADSL low pass filter is set between phone and ADSL Modem usually.

See also Fig. 1, it is the user mode key diagram of ADSL low pass filter.One side of ADSL filter 100 is connected with ADSL Modem (modem) 200 and telephone wire 300, and opposite side then is connected with telephone set 400.

Various countries telecommunications unit is set with some standards for the ADSL low pass filter.That is to say, must be by the testing standard of telecommunications unit.Yet, by the standard of telecommunications test, to use complicated circuit for easily usually, therefore increased the cost of filter.

Summary of the invention

The purpose of this invention is to provide a kind of ADSL low pass filter, it has simple circuit design and can meet Britain Telecom's standard.

ADSL low pass filter of the present invention comprises:

First filter circuit, it comprises:

First circuit, it comprises first inductance, first electric capacity and first resistance in parallel; And

Second circuit, it comprises second inductance, second electric capacity and second resistance in parallel; Wherein this first circuit is in parallel with this second circuit;

Second filter circuit comprises first transformer with primary coil and secondary coil, and wherein an end that is positioned at homonymy of the primary coil of this first transformer and secondary coil is connected with second circuit with first circuit of this first filter circuit respectively;

The 3rd filter circuit comprises:

Tertiary circuit, comprise the 3rd electric capacity, second transformer and the 4th electric capacity in parallel, wherein the two ends of the 3rd electric capacity are connected with the primary coil of this first transformer and the other end of secondary coil respectively, this second transformer has primary coil and secondary coil, an end that is positioned at homonymy of the primary coil of this second transformer and secondary coil is connected with the two ends of the 3rd electric capacity respectively, and the two ends of the 4th electric capacity are connected with the primary coil of this second transformer and the other end of secondary coil respectively;

The 4th circuit comprises the 5th electric capacity and the 3rd resistance in parallel;

The 5th circuit comprises the 6th electric capacity and the 4th resistance in parallel; Wherein the two ends of the 5th electric capacity of the 4th circuit connect the 3rd electric capacity of this tertiary circuit and an end of the 4th electric capacity respectively, and the two ends of the 6th electric capacity of the 5th circuit connect the 3rd electric capacity of this tertiary circuit and the other end of the 4th electric capacity respectively; And

The 7th electric capacity, it is connected with the 5th electric capacity.

ADSL low pass filter provided by the invention, its circuit design is simple and cost is lower, and meets Britain Telecom's standard.

Description of drawings

Fig. 1 is the user mode key diagram of ADSL low pass filter;

Fig. 2 is the circuit diagram of low pass filter of the present invention.

Embodiment

As mentioned above, ADSL filter of the present invention is for meeting Britain Telecom's standard and can reducing the filter cost and design.

See also Fig. 2, it is for the circuit diagram of ADSL low pass filter of the present invention.

ADSL low pass filter 1000 of the present invention comprises first filter circuit 500, second filter circuit 600 and the 3rd filter circuit 700.The input of low pass filter 1000 has the telephone line joint 2000 of British specification, in order to be connected with the telephone wire of telecommunication bureau; And ADSL Modem socket 3000, in order to connect ADSL Modem.The output of low pass filter 1000 also comprises a telephone socket 4000, is used for connecting telephone set.

First filter circuit 500 comprises first circuit 501 and second circuit 502.First circuit 501 comprises first inductance 5011, first electric capacity 5012 and first resistance 5013 in parallel.Second circuit 502 comprises second inductance 5021, second electric capacity 5022 and second resistance 5023 in parallel.First circuit 501 is in parallel with second circuit 502.

Second filter circuit 600 comprises first transformer, and is connected with first filter circuit 500.

The 3rd filter circuit 700 is connected with first transformer 600, and comprises tertiary circuit 701, the 4th circuit 702 and the 5th circuit 703.

Tertiary circuit 701 comprises the 3rd electric capacity 7011, second transformer 7012 and the 4th electric capacity 7013 in parallel.The 4th circuit 702 comprises the 5th electric capacity 7021 and the 3rd resistance 7022 in parallel.The 5th circuit 703 comprises the 6th electric capacity 7031 and the 5th resistance 7032 in parallel.Tertiary circuit 701, the 4th circuit 702 and 703 parallel connections of the 5th circuit.

Also comprise the 7th electric capacity 800 in addition, be connected with the 5th electric capacity 7021.

Because the principle of low pass filter is known by person skilled in the art person, thereby no longer describes at each circuit element at this.

The test result explanation of filter of the present invention below is provided.The important test event of the relevant ADSL performance of filter that British Telecom proposes is as follows:

1. The matched impedance of end-speech (Matching impedance for voice terminals)

[standard]: the impedance Z complex of telecommunication bureau's network (2)=230nF//1050 Ω+320 Ω.

2. Return loss (Return loss)

[standard]:

Should use Zcomplex (2) impedance.Test case is that adsl port is that open circuit (open circuit) or E.4/G.992.1 defined ZHP-r are in parallel with the Line end.

At frequency range 300Hz-500Hz Min 14dB

At frequency range 500Hz-2KHz Min 18dB

At frequency range 2KHz-3.4KHz Min 14dB

3. Insert loss (Insertion loss)

[standard]:

(1) telephony port (telephone port) arrives the insertion loss of telephone signal line cap (line port): at frequency range 1KHz＜1dB.

(2) when connected phone transmitter during by off-hook (off hook), the insertion loss of filter telephony port:

At frequency range 32KHz-350KHz Min 29dB

At frequency range 350KHz-1104KHz Min 55dB

4. Insert loss decay (Insertion loss distortion)

[standard]:

At voice band (voice band):

200-4000Hz＜+/-1dB

5. Unbalanced to ground (Unbalance about Earth)

[standard]: during terminal 600 Ω (terminated with 600 Ω), each frequency range numerical value is as follows:

5-50Hz＞40dB

50-600Hz＞46dB

600-3400Hz＞52dB

30KHz-1104KHz＞45dB

1104KHz-5MHz＞30dB

It below is the test result of ADSL low pass filter of the present invention.In this test, the numerical value of the element of low pass filter is as follows:

The first inductance 5011:15mH

The first electric capacity 5012:470nF

The first resistance 5013:75 Ω

The second inductance 5021:15mH

The second electric capacity 5022:470nF

The second resistance 5023:75 Ω

The first transformer 600:2.0mH

The 3rd electric capacity 7011:6.8nF

The second transformer 7012:2.0mH

The 4th electric capacity 7013:6.8nF

The 5th electric capacity 7021:12nF

The 3rd resistance 7022:10K Ω

The 6th electric capacity 7031:2.2nF

The 4th resistance 7032:10K Ω

The 7th electric capacity 800:1050K Ω

1. Isolate (Isolation)

[output valve]: 47 Ω

[test result]: by

2. Insert loss (Insertion loss)

[output valve]: the dB of unit

1KHz：0.88

32KHz-350KHz：34.134

350KHz-1104KHz：57.185

[test result]: by

3. Insert loss decay (Insertion loss distortion)

Parallel filter quantity: 2

[output valve]: the dB of unit

300Hz：-0.43

500Hz：-0.54

1KHz：0.88

1.5KHz：0.26

2.0KHz：0.62

3.4KHz：0.59

4KHz：0.68

[test result]: by

4. Return loss (Return loss)

Series filter quantity: 2

[output valve]: the dB of unit

300HZ：26.3

500HZ：23.2

1KHZ：20.8

1.5KHZ：20.6

2.0KHZ：21.4

2.8KHZ：20.9

3.4KHZ：19.3

[test result]: by

5. Unbalanced to ground (Unbalance about earth)

[output valve]: the dB of unit

5-50Hz：82

50-600Hz：74

600-3400Hz：68

30KHz-1104KHz：62

1104KHz-5MHz：60

[test result]: by

The above embodiment is not in order to restriction the present invention.Scope of the present invention should be defined by the appended claims.

Claims (1)

1. ADSL low pass filter comprises:

First filter circuit, it comprises:

First circuit, it comprises first inductance, first electric capacity and first resistance in parallel; And

Second circuit, it comprises second inductance, second electric capacity and second resistance in parallel; Wherein this first circuit is in parallel with this second circuit;

Second filter circuit comprises first transformer with primary coil and secondary coil, and wherein an end that is positioned at homonymy of the primary coil of this first transformer and secondary coil is connected with second circuit with first circuit of this first filter circuit respectively;

The 3rd filter circuit comprises:

Tertiary circuit, comprise the 3rd electric capacity, second transformer and the 4th electric capacity in parallel, wherein the two ends of the 3rd electric capacity are connected with the primary coil of this first transformer and the other end of secondary coil respectively, this second transformer has primary coil and secondary coil, an end that is positioned at homonymy of the primary coil of this second transformer and secondary coil is connected with the two ends of the 3rd electric capacity respectively, and the two ends of the 4th electric capacity are connected with the primary coil of this second transformer and the other end of secondary coil respectively;

The 4th circuit comprises the 5th electric capacity and the 3rd resistance in parallel;

The 5th circuit comprises the 6th electric capacity and the 4th resistance in parallel; Wherein the two ends of the 5th electric capacity of the 4th circuit connect the 3rd electric capacity of this tertiary circuit and an end of the 4th electric capacity respectively, and the two ends of the 6th electric capacity of the 5th circuit connect the 3rd electric capacity of this tertiary circuit and the other end of the 4th electric capacity respectively; And

The 7th electric capacity, it is connected with the 5th electric capacity.

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