| 摘要 |
Disclosed are a method and a circuit for impedance matching. The method comprises: a peripheral impedance detection module detecting an impedance of a subscriber telephone and outputting information about the impedance of the subscriber telephone; an analog switch switching module providing an impedance matching path between the impedance of the subscriber telephone and an impedance matching module according to the information about the impedance of the subscriber telephone output by the peripheral impedance detection module; the impedance matching module providing a corresponding impedance through the impedance matching path provided by the analog switch switching module to match to said impedance of the subscriber telephone. By the present invention, the impedance matching is achieved when a wireless access box communicates with telephones with various impedance modes. The matching process is flexible, automatic, and does not need manual configuration, and the technology is simple, reliable, and of low cost. |
| 主权项 |
1. An impedance matching circuit, comprising a peripheral impedance detection module, an analog switch switching module and an impedance matching module that are connected in turn, wherein,
the peripheral impedance detection module is set to: detect impedance of a subscriber telephone and output information about the impedance of the subscriber telephone; the analog switch switching module is set to: provide an impedance matching path between the impedance of the subscriber telephone and the impedance matching module according to the information about the impedance of the subscriber telephone output by the peripheral impedance detection module; the impedance matching module is set to: provide a corresponding impedance, through the impedance matching path provided by the analog switch switching module, to match said impedance of the subscriber telephone; wherein, the peripheral impedance detection module comprises an analog to digital conversion (ADC) detection module, and the ADC detection module is set to: output the information about the impedance of the subscriber telephone in the form of high or low level according to a value of the impedance of the subscriber telephone; said ADC detection module comprises a resistor R0, a resistor R1, a resistor R2, a resistor R3, a voltage comparator N1 and a voltage comparator N2, wherein, one end of the resistor R0 is connected to the system power supply Vcc, and the other end of the resistor R0 is connected to the impedance Rx of the subscriber telephone, as well as negative input ends of the voltage comparator N1 and the voltage comparator N2; one end of the resistor R1 is connected to ground, and the other end of the resistor R1 is connected to a positive input end of the voltage comparator N1 and the resistor R2; one end of the resistor R2 is connected to the positive input end of the voltage comparator N1 and the resistor R1, and the other end of the resistor R2 is connected to the positive input end of the voltage comparator N2 and the resistor R3; one end of the resistors R3 is connected to the system power source Vcc and the other end of the resistor R3 is connected to the positive input end of the voltage comparator N2 and the resistor R2; the resistor R1, the resistor R2, and the resistor R3 are divider resistors and provide reference voltages to the voltage comparators N1 and N2; the output ends of the voltage comparators N1 and N2 are connected to the analog switch switching module, according to the value of the impedance Rx of the subscriber phone , the voltage comparator N1 and the voltage comparator N2 output high or low level.
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