Programmable/tunable active RC filter

A method of carrying out a programmable/tunable active RC filter, comprising:

• adjusting said programmable/tunable active RC filter to an operation band by tuning a plurality of series variable resistors;
• determining a cut-off frequency of said programmable/tunable active RC filter within the tuning frequency range by tuning a plurality of controllable shunt devices;
• and
• programming said programmable/tunable active RC filter to a voltage gain after said cut-off frequency has been determined by tuning parts of said plurality of controllable shunt devices.

A programmable/tunable active RC filter, comprising:

• a first controllable shunt device having an input terminal, a first output terminal and a second output terminal;
• a second controllable shunt device having an input terminal, a first output terminal and a second output terminal, wherein said second output terminal of said second controllable shunt device is connected to said second output terminal of said first controllable shunt device, said first and second shunt controllable devices for determining a cut-off frequency;
• a differential amplifier having two input terminals and two output terminals, wherein each of said two input terminals is respectively connected to each of said first output terminals of said first controllable shunt device and said second controllable shunt device;
• two first variable resistors RP, wherein one end of said two first variable resistors are respectively connected to a first input signal and a second input signal, and another end of said two first variable resistors are respectively connected to said input terminals of said first controllable shunt device and said second controllable shunt device;
• two second variable resistors Rf, wherein one end of said two second variable resistors are respectively connected to said two output terminals of said differential amplifier, and another end of said two second variable resistors are respectively connected to said input terminals of said first controllable shunt device and said second controllable shunt device;
• and
• two capacitors, wherein each of said two capacitors is respectively connected to said two input terminals and said two output terminals of said differential amplifier for forming a RC filter and being outputted from two output terminals of said two capacitors.

A dual module portable wireless communication system having a programmable/tunable active RC filter, comprising:

• a first controllable shunt device having an input terminal, a first output terminal and a second output terminal;
• a second controllable shunt device having an input terminal, a first output terminal and a second output terminal, wherein said second output terminal of said second controllable shunt device is connected to said second output terminal of said first controllable shunt device;
• a differential amplifier having two input terminals and two output terminals, wherein each of said two input terminals is respectively connected to each of said first output terminals of said second controllable shunt device and said second controllable shunt device;
• two first variable resistors RP, wherein one end of said two first variable resistors are respectively connected to a first input signal and a second input signal, and another end of said two first variable resistors are respectively connected to said input terminals of said first controllable shunt device and said second controllable shunt device;
• two second variable resistors Rf, wherein one end of said two second variable resistors are respectively connected to said two output terminals of said differential amplifier, and another end of said two second variable resistors are respectively connected to said input terminals of said first controllable shunt device and said second controllable shunt device;
• two capacitors, wherein each of said two capacitors is respectively connected to said two input terminals and said two output terminals of said differential amplifier for forming said programmable/tunable RC filter and then being outputted from two output terminals of said two capacitors;
• and
• two fourth variable resistors RC between said two first variable resistors and said input terminals of said first controllable shunt device and said second controllable shunt device, wherein one end of said two fourth variable resistors is connected to another end of said two first variable resistors, and another end of said two fourth variable resistors is connected to said input terminals of said first controllable shunt device and said second controllable shunt device;
• and
• a radio transceiver, wherein said radio transceiver receives the signals outputting from said programmable/tunable active RC filter in said dual module portable wireless communication system.