Switchable filtering circuit and the operation method using the same

Abstract

The disclosure provides a switchable filtering circuit and the related operation method, in particular related to a filtering circuit which can be used for Bluetooth system and wireless local area network system. By using a first switch, a hybrid filtering circuit and a second switch, the received mode and transmitted mode between these two systems is realized. Moreover, the frequency responses and the bandwidth adjustments can be controlled according to the plurality of switchable resistors, the plurality of switchable capacitors and the shared and switchable resistors within the hybrid filter circuit. Moreover, the effects of high operated freedom of the circuit and the circuit size reduction can be achieved.

What is claimed is: 
     
         1 . A switchable filtering circuit, used for wireless local area network system and Bluetooth system, comprising: a first switch, having a first input port, a second input port, a third input port, a fourth input port, a first output port, a second output port, a third output port and a fourth output port, the first input port electrically connected to an output port of a RF circuit of a first receiver, the second input port electrically connected to an output port of a baseband circuit of a first transmitter, the third input port electrically connected to an output port of a RF circuit of a second receiver, and the fourth input port electrically connected to an output port of a baseband circuit of a second transmitter;
 a hybrid filtering circuit, having a first input port, a second input port, a third input port, a fourth input port, a first output port, a second output port, a third output port and a fourth output port, the first input port electrically connected to the first output port of the first switch, the second input port electrically connected to the second output port of the first switch, the third input port electrically connected to the third output port of the first switch, the fourth input port electrically connected to the fourth output port of the first switch; and   a second switch, having a first input port, a second input port, a third input port, a fourth input port, a first output port, a second output port, a third output port and a fourth output port, the first input port electrically connected to the first output port of the hybrid filtering circuit, the second input port electrically connected to the second output port of the hybrid filtering circuit, the third input port electrically connected to the third output port of the hybrid filtering circuit, the fourth input port electrically connected to the fourth output port of the hybrid filtering circuit, the first output port electrically connected to a first input port of a baseband circuit of a first receiver, the second output port electrically connected to an input port of a RF circuit of a first transmitter, the third output port electrically connected to an input port of a baseband circuit of a second receiver, and the fourth output port electrically connected to an input port of a RF circuit of a second transmitter.   
     
     
         2 . A switchable filtering circuit as claimed in  claim 1 , wherein the hybrid filtering circuit further comprises:
 a first switchable resistor, having an input port and an output port, the input port electrically connected to the first output port of the first switch;   a second switchable resistor, having an input port and an output port, the input port electrically connected to the second output port of the first switch;   a first amplifier, having a first input port, a second input port, a first output port and a second output port, the first input port electrically connected to the output port of the first switchable resistor, and the second input port electrically connected to the output port of the second switchable resistor;   a first switchable capacitor, having an input port and an output port, the input port electrically connected to the first input port of the first amplifier, and the output port electrically connected to the first output port of the first amplifier;   a third switchable resistor, having an input port and an output port, the input port electrically connected to the first input port of the first amplifier, and the output port electrically connected to the first output port of the first amplifier;   a second switchable capacitor, having an input port and an output port, the input port electrically connected to the second input port of the first amplifier, and the output port electrically connected to the second output port of the first amplifier;   a fourth switchable resistor, having an input port and an output port, the input port electrically connected to the second input port of the first amplifier, and the output port electrically connected to the second output port of the first amplifier;   a fifth switchable resistor, having an input port and an output port, the input port electrically connected to the third output port of the first switch;   a sixth switchable resistor, having an input port and an output port, the input port electrically connected to the fourth output port of the first switch;   a second amplifier, having a first input port, a second input port, a first output port and a second output port, the first input port electrically connected to the output port of the fifth switchable resistor, and the second input port electrically connected to the output port of the sixth switchable resistor;   a third switchable capacitor, having an input port and an output port, the input port electrically connected to the first input port of the second amplifier, and the output port electrically connected to the first output port of the second amplifier;   a seventh switchable resistor, having an input port and an output port, the input port electrically connected to the first input port of the second amplifier, and the output port electrically connected to the first output port of the second amplifier;   a fourth switchable capacitor, having an input port and an output port, the input port electrically connected to the second input port of the second amplifier, and the output port electrically connected to the second output port of the second amplifier;   a eighth switchable resistor, having an input port and an output port, the input port electrically connected to the second input port of the second amplifier, and the output port electrically connected to the second output pot of the second amplifier;   a plurality of array of shared and switchable resistors, having a first input port, a second input port, a third input port, a fourth input port, a first output port, a second output port, a third output port and a fourth output port, the first input port electrically connected to the output port of the first switchable resistor, the second input port electrically connected to the output port of the second switchable resistor, the third input port electrically connected the output port of the fifth switchable resistor, the fourth input port electrically connected to the output port of the sixth switchable resistor, the first output port electrically connected to the first output port of the first amplifier, the second output port electrically connected to the second output port of the first amplifier, the third output port electrically connected to the first output port of the second amplifier, and the fourth output port electrically connected to the second output port of the second amplifier; and   wherein the first switchable resistor, the second switchable resistor, the third switchable resistor, the fourth switchable resistor, the fourth switchable resistor, the sixth switchable resistor, the seventh switchable resistor, the eighth switchable resistor, the first switchable capacitor, the second switchable capacitor, the third switchable capacitor and the fourth switchable capacitor, having a switch respectively, used for checking whether the switches are connected or not.   
     
     
         3 . A switchable filtering circuit as claimed in  claim 1 , wherein the hybrid filtering circuit can form as a high-stage filtering circuit by cascading the hybrid filtering circuit constantly. 
     
     
         4 . A switchable filtering circuit as claimed in  claim 1 , wherein the values of the first switchable resistor, the values of the second switchable resistor, the values of the third switchable resistor and the values of the fourth switchable resistor equal to each other. 
     
     
         5 . A switchable filtering circuit as claimed in  claim 1 , wherein the values of the first switchable capacitor and the values of the second switchable capacitor equal to each other. 
     
     
         6 . A switchable filtering circuit as claimed in  claim 1 , wherein the values of the fifth switchable resistor, the values of the sixth switchable resistor, the values of the seventh switchable resistor and the values of the eighth switchable resistor equal to each other. 
     
     
         7 . A switchable filtering circuit as claimed in  claim 1 , wherein the values of the third switchable capacitor and the values of the fourth switchable capacitor equal to each other. 
     
     
         8 . A switchable filtering circuit as claimed in  claim 1 , wherein the plurality of array of shared and switchable resistors further comprises:
 a first shared and switchable resistor, having an input port and an output port, the input port electrically connected to the output port of the first switchable resistor, and the output port electrically connected to the first output port of the first amplifier;   a second shared and switchable resistor, having an input port and an output port, the input port electrically connected to the output port of the second switchable resistor, and the output port electrically connected to the second output port of the first amplifier;   the third shared and switchable resistor, having an input port and an output port, the input port electrically connected to the output port of the fifth switchable resistor, and the output port electrically connected to the first output port of the second amplifier; and   a fourth shared and switchable resistor, having an input port and an output port, the input port electrically connected to the output port of the sixth switchable resistor, and the output port electrically connected to the second output port of the second amplifier;   wherein the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor, having a switch respectively, used for checking whether the switches are connected or not.   
     
     
         9 . A switchable filtering circuit as claimed in  claim 8 , wherein the values of the first shared and switchable resistor, the values of the second shared and switchable resistor, the values of the third shared and switchable resistor and the values of the fourth shared and switchable resistor equal to each other. 
     
     
         10 . A switchable filtering circuit as claimed in  claim 1 , when the hybrid filtering circuit is set as a low-pass filter, the passband bandwidth of the low-pass filter defined according to the reciprocal of the product of the values of the resistance from the first switchable resistor, the second switchable resistor, the third switchable resistor and the fourth switchable resistor and the capacitance from the first switchable capacitor and the second switchable capacitor. 
     
     
         11 . A switchable filtering circuit as claimed in  claim 1 , when the hybrid filtering circuit is set as a bandpass filter, the passband bandwidth of the bandpass filter defined according to the reciprocal of the product of the values of the resistance from the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor and the capacitance from the first switchable capacitor and the second switchable capacitor. 
     
     
         12 . An operation method of switchable filtering circuit, particularly used for wireless local area network system and Bluetooth system, comprising steps of:
 step 1: when the switchable filtering circuit as claimed in  claim 1  is set as received mode for a wireless local area network system, connecting the output port of the RF circuit of the first receiver to the first input port of the first switch, connecting the first output port of the first switch to the input port of the first switchable resistor, connecting the first input port of the second switch to the first output port of the first amplifier, and connecting the first output port of the second switch to the input port of the baseband circuit of the first receiver;   step 2: when the switchable filtering circuit as claimed in  claim 1  is set as transmitted mode for a wireless local area network system, connecting the output port of the baseband circuit of the first transmitter to the second input port of the first switch, connecting the second output port of the first switch to the input port of the second switchable resistor, connecting the second input port of the second switch to the second output port of the first amplifier, and connecting the second output port of the second switch to the input port of the RF circuit of the first transmitter;   step 3: when the switchable filtering circuit as claimed in  claim 1  is set as received mode for a Bluetooth system, connecting the output port of the RF circuit of the second receiver to the third input port of the first switch, connecting the third output port of the first switch to the input port of the fifth switchable resistor, connecting the third input port of the second switch to the first output port of the second amplifier, and connecting the third output port of the second switch to the input port of the baseband circuit of the second receiver; and   step 4: when the switchable filtering circuit as claimed in  claim 1  is set as transmitted mode for a Bluetooth system, connecting the output port of the baseband circuit of the second transmitter to the fourth input port of the first switch, connecting the fourth output port of the first switch to the input port of the sixth switchable resistor, connecting the fourth input port of the second switch to the second output port of the second amplifier, and connecting the fourth output port of the second switch to the input port of the RF circuit of the second transmitter.   
     
     
         13 . An operation method of switchable filtering circuit as claimed in  claim 12 , wherein when the hybrid filtering circuit is set as a low-pass filter, further comprises steps of:
 step 1-1: when setting as received mode for a wireless local area network system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the first switchable capacitor and the second switchable capacitor, and turning on one of the first switchable resistor, the second switchable resistor, the third switchable resistor and the fourth switchable resistor;   step 2-1: when setting as transmitted mode for a wireless local area network system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the first switchable capacitor and the second switchable capacitor, and turning on one of the first switchable resistor, the second switchable resistor, the third switchable resistor and the fourth switchable resistor;   step 3-1: when setting as received mode for a Bluetooth system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the third switchable capacitor and the fourth switchable capacitor, and turning on one of the fifth switchable resistor, the sixth switchable resistor, the seventh switchable resistor and the eighth switchable resistor; and   step 4-1: when setting as transmitted mode for a Bluetooth system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the third switchable capacitor and the fourth switchable capacitor, and turning on one of the fifth switchable resistor, the sixth switchable resistor, the seventh switchable resistor and the eighth switchable resistor.   
     
     
         14 . An operation method of switchable filtering circuit as claimed in  claim 12 , wherein when the hybrid filtering circuit is set as a bandpass filter, further comprises steps of:
 step 1-1: when setting as received mode for a wireless local area network system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the first switchable capacitor and the second switchable capacitor, and turning on one of the first switchable resistor, the second switchable resistor, the third switchable resistor and the fourth switchable resistor;   step 2-1: when setting as transmitted mode for a wireless local area network system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the first switchable capacitor and the second switchable capacitor, and turning on one of the first switchable resistor, the second switchable resistor, the third switchable resistor and the fourth switchable resistor;   step 3-1: when setting as received mode for a Bluetooth system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the third switchable capacitor and the fourth switchable capacitor, and turning on one of the fifth switchable resistor, the sixth switchable resistor, the seventh switchable resistor and the eighth switchable resistor; and   step 4-1: when setting as transmitted mode for a Bluetooth system, turning on the first shared and switchable resistor, the second shared and switchable resistor, the third shared and switchable resistor and the fourth shared and switchable resistor within the plurality of array of shared and switchable resistors, turning on one of the third switchable capacitor and the fourth switchable capacitor, and turning on one of the fifth switchable resistor, the sixth switchable resistor, the seventh switchable resistor and the eighth switchable resistor.