Referring to FIG. 1, a block diagram of a conventional wireless RF module is shown. As illustrated, the wireless RF module 10 comprises a baseband unit 11, a RF transceiver unit 13, a control unit 15 and a power amplification unit 17, wherein the baseband unit 11 is electrically connected to the power amplification unit 17 through the RF transceiver unit 13 and the control unit 15.
The baseband unit 11 can transmit a control signal TRx_con and a baseband signal BB_sig to the RF transceiver unit 13, wherein the control signal TRx_con is adapted for controlling on/off, operating band selection or other related functions of the RF transceiver unit 13, or regulating the output power of the RF transceiver unit 13. The baseband signal BB_sig is adapted for transmitting a modulating signal associated with the system specifications to the RF transceiver unit 13 so that the RF transceiver unit 13 can up-convert the frequency of the baseband signal BB_sig to generate a RF signal. The RF transceiver unit 13 can further transmit the RF signal to the power amplification unit 17 where the power amplification unit 17 amplifies the received RF signal and then outputs the amplified RF signal.
The control unit 15 is electrically coupled with the power amplification unit 17, and adapted for controlling on/off and operating band selection of the power amplification unit 17, or regulating the output power of the power amplification unit 17. In actual application, the control unit 15 can control on/off and operating band selection of the power amplification unit 17 by changing the power supply voltage Vcc and/or bias voltage Vbias being provided to the power amplification unit 17, thereby regulating the output power of the power amplification unit 17 so that the power amplification unit 17 can properly amplify the RF signal being received from the RF transceiver unit 13.
The baseband unit 11 can transmit at least one control signal PA_con to the control unit 15, thereby controlling on/off and operating band selection of the power amplification unit 17. The baseband unit 11 can also transmit another power control signal Vramp to the control unit 15 to control the output power of the power amplification unit 17.
Currently, the industry has defined the power-vs-time curve of the power amplification unit 17 of the wireless RF module 10. For example, in GSM (Global System for Mobile Communications) system, the power-vs-time curve of the power amplification unit 17 must fall in a predetermined range.
However, in actual application, the output power characteristic of the power amplification unit 17 can be affected by many factors, such as the ambient temperature, the operating temperature and memory effect of the power amplification unit 17 and the bandwidth or frequency dependent characteristics of the power amplification unit 17, resulting in a discrepancy between the actual output power characteristic and the required output power characteristics of the power amplification unit 17.
In order to eliminate the aforesaid problem, the control unit 15 is controlled to adjust the power supply voltage Vcc and/or bias voltage Vbias being provided to the power amplification unit 17, thereby correcting or compensating the output power characteristics of the power amplification unit 17. However, in conventional RF module, the adjustment of the power amplification unit 17 from the control unit 15 is done by analog circuit. The adjustment achieved by analog circuit is more complex and less flexibility due to the complexity and process variation of the analog circuit. Therefore, the conventional method to adjust the characteristic power amplification unit 17 by analog circuit in the control unit 15 is not flexible for the wireless communication module. For example, an error can be easily occurred when the control unit 15 try to adjust the output power of the power amplification unit 17 through a power supply voltage Vcc and/or a bias voltage Vbias, causing some of the specification such as the power-vs-time curve of the power amplification unit 17 or the shape of the spectrum fail the specifications of GSM or other related systems.