CN1960420B - ADSL low pass filter - Google Patents

Abstract

The present invention provides an ADSL low-pass filter, including: the filter circuit comprises a first filter circuit, a second filter circuit and a third filter circuit. The first filter circuit includes: the first circuit comprises a first inductor, a first capacitor and a first resistor which are connected in parallel; the second circuit comprises a second inductor, a second capacitor and a second resistor which are connected in parallel; wherein the first circuit is connected in parallel with the second circuit. And the second filter circuit is connected with the first filter circuit and comprises a first transformer. The third filter circuit is connected to the first transformer and includes: the third circuit comprises a third capacitor, a second transformer and a fourth capacitor which are connected in parallel; the fourth circuit comprises a fifth capacitor and a third resistor which are connected in parallel; the fifth circuit comprises a sixth capacitor and a fourth resistor which are connected in parallel; wherein the third circuit, the fourth circuit and the fifth circuit are connected in parallel. The ADSL low pass filter also comprises a seventh capacitor connected with the fifth capacitor. The ADSL low pass filter is low cost and meets british telecommunications specifications.

Description

ADSL low pass filter

technical field

The present invention relates to ADSL (Asymmetric Digital Subscriber Line, asymmetric digital subscriber line) low-pass filter, particularly relates to the ADSL low-pass filter that can comply with British Telecom specification.

Background technique

ADSL is a broadband network service commonly used by the public. ADSL usually uses indoor telephone lines to transmit signals. In order to prevent the ADSL signal from interfering with the telephone signals transmitted on the telephone line, an ADSL low-pass filter is usually set between the telephone and the ADSL modem.

Please refer to Figure 1, which is an illustration of the use state of the ADSL low-pass filter. One side of the ADSL filter 100 is connected to an ADSL modem (modem) 200 and a telephone line 300 , and the other side is connected to a telephone 400 .

The telecommunications organizations of various countries have some regulations on ADSL low-pass filter setting. That is to say, it must pass the test standard of the telecommunications unit. However, to easily pass telecommunications testing standards, more complex wiring is usually used, thus increasing the cost of the filter.

Contents of the invention

The object of the present invention is to provide an ADSL low-pass filter which has a simple circuit design and can comply with British Telecom specifications.

ADSL low-pass filter of the present invention comprises:

A first filtering circuit comprising:

a first circuit comprising a first inductor, a first capacitor, and a first resistor connected in parallel; and

A second circuit, which includes a second inductor, a second capacitor, and a second resistor connected in parallel; wherein the first circuit is connected in parallel with the second circuit;

The second filter circuit includes a first transformer with a primary coil and a secondary coil, wherein one end of the primary coil and the secondary coil of the first transformer on the same side is respectively connected to the first circuit and the second circuit of the first filter circuit. circuit connection;

The third filter circuit, including:

The third circuit includes a third capacitor, a second transformer and a fourth capacitor connected in parallel, wherein the two ends of the third capacitor are respectively connected to the primary coil of the first transformer and the other end of the secondary coil, and the second transformer has The primary coil and the secondary coil, one end of the primary coil and the secondary coil on the same side of the second transformer are respectively connected to the two ends of the third capacitor, and the two ends of the fourth capacitor are respectively connected to the second transformer The other end of the primary coil and the secondary coil are connected;

The fourth circuit includes a fifth capacitor and a third resistor connected in parallel;

The fifth circuit includes a sixth capacitor and a fourth resistor connected in parallel; wherein both ends of the fifth capacitor of the fourth circuit are respectively connected to one end of the third capacitor and the fourth capacitor of the third circuit, and the fifth capacitor of the fifth circuit The two ends of the six capacitors are respectively connected to the third capacitor and the other end of the fourth capacitor of the third circuit; and

The seventh capacitor is connected to the fifth capacitor.

The ADSL low-pass filter provided by the invention has simple circuit design and low cost, and conforms to British telecommunication standards.

Description of drawings

Figure 1 is an illustration of the state of use of the ADSL low-pass filter;

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

Detailed ways

As mentioned above, the ADSL filter of the present invention is designed to comply with the British Telecom specification and to reduce the cost of the filter.

Please refer to FIG. 2 , which is a circuit diagram of the ADSL low-pass filter of the present invention.

The ADSL low-pass filter 1000 of the present invention includes a first filter circuit 500 , a second filter circuit 600 and a third filter circuit 700 . The input end of the low-pass filter 1000 has a UK standard telephone line connector 2000 for connecting to the telephone line of the telecommunication bureau; and an ADSL modem socket 3000 for connecting an ADSL modem. The output end of the low-pass filter 1000 also includes a telephone socket 4000 for connecting to a telephone.

The first filter circuit 500 includes a first circuit 501 and a second circuit 502 . The first circuit 501 includes a first inductor 5011 , a first capacitor 5012 and a first resistor 5013 connected in parallel. The second circuit 502 includes a second inductor 5021 , a second capacitor 5022 and a second resistor 5023 connected in parallel. The first circuit 501 and the second circuit 502 are connected in parallel.

The second filter circuit 600 includes a first transformer and is connected to the first filter circuit 500 .

The third filter circuit 700 is connected to the first transformer 600 and includes a third circuit 701 , a fourth circuit 702 and a fifth circuit 703 .

The third circuit 701 includes a third capacitor 7011 , a second transformer 7012 and a fourth capacitor 7013 connected in parallel. The fourth circuit 702 includes a fifth capacitor 7021 and a third resistor 7022 connected in parallel. The fifth circuit 703 includes a sixth capacitor 7031 and a fifth resistor 7032 connected in parallel. The third circuit 701 , the fourth circuit 702 and the fifth circuit 703 are connected in parallel.

It also includes a seventh capacitor 800 connected to the fifth capacitor 7021 .

Since the principle of the low-pass filter is well known to those skilled in the art, no description will be given for each circuit element here.

A description of the test results of the filter of the present invention is provided below. The important test items about ADSL filter performance proposed by British Telecommunications Bureau are as follows:

1. Matching impedance for voice terminals

[Standard]: Impedance Zcomplex(2)=230nF//1050Ω+320Ω of telecom bureau network.

2. Return loss

[standard]:

Zcomplex(2) impedance should be used. The test condition is that the ADSL port is open circuit or the ZHP-r defined by E.4/G.992.1 is connected in parallel with the Line end.

In the frequency band 300Hz-500Hz Min 14dB

In the frequency band 500Hz-2KHz Min 18dB

In the frequency band 2KHz-3.4KHz Min 14dB

3. Insertion loss

[standard]:

(1) Insertion loss from the telephone port (telephone port) to the telephone signal line port (line port): 1KHz<1dB in the frequency band.

(2) Insertion loss of the filter telephone port when the connected telephone handset is off hook:

In the frequency band 32KHz-350KHz Min 29dB

In the frequency band 350KHz-1104KHz Min 55dB

4. Insertion loss attenuation (Insertion loss distortion)

[standard]:

In the voice band (voice band):

200-4000Hz＜+/-1dB

5. Unbalance about Earth

[Standard]: When the terminal is 600Ω (terminated with 600Ω), the values of each frequency band are as follows:

5-50Hz＞40dB

50-600Hz＞46dB

600-3400Hz＞52dB

30KHz-1104KHz＞45dB

1104KHz-5MHz＞30dB

The following are the test results of the ADSL low-pass filter of the present invention. In this test, the values of the components of the low-pass filter are as follows:

The first inductance 5011: 15mH

The first capacitor 5012: 470nF

The first resistor 5013: 75Ω

Second inductance 5021: 15mH

Second capacitor 5022: 470nF

Second resistor 5023: 75Ω

The first transformer 600: 2.0mH

The third capacitor 7011: 6.8nF

Second transformer 7012: 2.0mH

Fourth capacitor 7013: 6.8nF

Fifth capacitor 7021: 12nF

The third resistor 7022: 10KΩ

Sixth capacitor 7031: 2.2nF

Fourth resistor 7032: 10KΩ

The seventh capacitor 800: 1050KΩ

1. Isolation

[Output value]: 47Ω

[Test result]: pass

2. Insertion loss

[Output value]: Unit dB

1KHz: 0.88

32KHz-350KHz: 34.134

350KHz-1104KHz: 57.185

[Test result]: pass

3. Insertion loss distortion

Number of parallel filters: 2

[Output value]: Unit dB

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]: pass

4. Return loss

Number of filters in series: 2

[Output value]: Unit dB

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]: pass

5. Unbalance about earth

[Output value]: Unit dB

5-50Hz: 82

50-600Hz: 74

600-3400Hz: 68

30KHz-1104KHz: 62

1104KHz-5MHz: 60

[Test result]: pass

The above-mentioned embodiments are not intended to limit the present invention. The scope of the invention should be defined by the appended claims.

Claims (1)

1. A ADSL low-pass filter, comprising: A first filtering circuit comprising: a first circuit comprising a first inductor, a first capacitor, and a first resistor connected in parallel; and A second circuit, which includes a second inductor, a second capacitor, and a second resistor connected in parallel; wherein the first circuit is connected in parallel with the second circuit; The second filter circuit includes a first transformer with a primary coil and a secondary coil, wherein one end of the primary coil and the secondary coil of the first transformer on the same side is respectively connected to the first circuit and the second circuit of the first filter circuit. circuit connection; The third filter circuit, including: The third circuit includes a third capacitor, a second transformer and a fourth capacitor connected in parallel, wherein the two ends of the third capacitor are respectively connected to the primary coil of the first transformer and the other end of the secondary coil, and the second transformer has The primary coil and the secondary coil, one end of the primary coil and the secondary coil on the same side of the second transformer are respectively connected to the two ends of the third capacitor, and the two ends of the fourth capacitor are respectively connected to the second transformer The other end of the primary coil and the secondary coil are connected; The fourth circuit includes a fifth capacitor and a third resistor connected in parallel; The fifth circuit includes a sixth capacitor and a fourth resistor connected in parallel; wherein both ends of the fifth capacitor of the fourth circuit are respectively connected to one end of the third capacitor and the fourth capacitor of the third circuit, and the fifth capacitor of the fifth circuit The two ends of the six capacitors are respectively connected to the third capacitor and the other end of the fourth capacitor of the third circuit; and The seventh capacitor is connected to the fifth capacitor.

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