Radio frequency power amplifier and method for increasing power added efficiency and linearity

A radio frequency (RF) power amplifier is disclosed. The RF power amplifier includes an impedance transformation circuit, a current unit gain amplifier, and an output match circuit. The impedance transformation circuit receives a first input power signal and outputs a second input power signal correspondingly, wherein the impedance transformation circuit transforms an input impedance to an output impedance according to an impedance matching parameter for increasing power added efficiency of a pre-stage circuit. The current unit gain amplifier provides a linear transimpedance so as to transmit an input current to an output impedance, and then generate a linear output power for increasing power added efficiency of the current unit gain amplifier, wherein the impedance matching parameter is determined by a first system voltage, a second system voltage, and a predetermined power gain value.

BACKGROUND

1. Technical Field

The present invention relates to a radio frequency (RF) power amplifier, in particular, to a RF power amplifier for increasing a power added efficiency and a linearity.

2. Description of Related Art

Different specifications for the power transmitters in communication systems are needed because there are many methods for modulating signals. In recent years, an orthogonal frequency-division multiplexing (OFDM) modulated signal has been used in wireless communication networks (e.g., the communication network suitable for IEEE 802.11a/b/g specification) which is similar to a modulated method of Amplitude Modulation (AM). Therefore, it needs a high-linearity power amplifier. In general, high-linearity power amplifiers use common source (CS) power amplifiers of Class A or Class AB to increase the linearity. To increase the communication quality, it is essential to further increase the linearity and the power added efficiency of the power amplifier.

SUMMARY

An exemplary embodiment of the present disclosure provides a radio frequency (RF) power amplifier electrically connected to a pre-stage circuit to receive a first input power signal. The RF power amplifier includes an impedance transformation circuit, a current unit gain amplifier, and an output match circuit. The impedance transformation circuit is electrically connected to the pre-stage circuit. The impedance transformation circuit is configured for receiving the first input power signal and correspondingly outputting a second input power signal, wherein the impedance transformation circuit executes a power matching by an impedance transformation for increasing a power added efficiency (PAE) and a linearity of the RF power amplifier. The current unit gain amplifier is electrically connected to the impedance transformation circuit. The current unit gain amplifier is configured for receiving the second input power signal and correspondingly outputting an output power signal, wherein the current unit gain amplifier determines a predetermined power gain value based on an impedance reference value and an input impedance of the current unit gain amplifier is substantially made equal to an input impedance of the RF power amplifier by the impedance transformation circuit. The output match circuit is electrically connected to the current unit gain amplifier. The output match circuit has the impedance reference value for receiving the output power signal to execute the power matching and correspondingly outputs a RF output signal.

An exemplary embodiment of the present disclosure provides a method for increasing a PAE and a linearity, which is adapted for a RF power amplifier. The RF power amplifier is electrically connected to a pre-stage circuit to receive a first input power signal. The RF power amplifier includes an impedance transformation circuit, a current unit gain amplifier, and an output match circuit. The impedance transformation circuit is electrically connected to the pre-stage circuit and a first system voltage. The current unit gain amplifier is electrically connected to the impedance transformation circuit and a second system voltage. The output match circuit is electrically connected to the current unit gain amplifier. The method for increasing the PAE and the linearity includes the following steps: receiving the first input power signal and correspondingly outputting a second input power signal by the impedance transformation circuit, wherein the impedance transformation circuit executes a power matching by an impedance transformation for increasing the PAE and the linearity of the RF power amplifier; receiving the second input power signal and correspondingly outputting an output power signal by the current unit gain amplifier, wherein the current unit gain amplifier determines a predetermined power gain value based on an impedance reference value and an input impedance of the current unit gain amplifier is substantially made equal to an input impedance of the RF power amplifier by the impedance transformation circuit; and receiving the output power signal to execute the power matching and correspondingly outputting a RF output signal by the output match circuit, wherein the output match circuit has the impedance reference value.

To sum up, the exemplary embodiments of the present disclosure provide a RF power amplifier and a method for increasing power added efficiency and linearity, which can transform an input impedance to an output impedance according to an impedance matching parameter by an impedance transformation circuit. Accordingly, it can increase the power added efficiency and the linearity of the RF power amplifier in the condition of receiving a fixed input power.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Example embodiments will be described below in more detail with reference to the accompanying drawings. Many different forms and embodiments are possible without deviating from the spirit and teachings of this disclosure and so the disclosure should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. Like reference numbers refer to like elements throughout.

It will be understood that, although the terms first, second, third, and the like, may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only to distinguish one element, component, region, layer or section from another region, layer or section discussed below and could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

The following instruction describes a radio frequency (RF) power amplifier and a method for increasing the power added efficiency and the linearity via a plurality of embodiments with corresponding drawings. However, the embodiments below are not for restricting the scope of the present disclosure.

[Embodiment of the RF Power Amplifier]

Please refer toFIG. 1, which shows a block diagram of a RF power amplifier according to an exemplary embodiment of the present disclosure. As shown inFIG. 1, a radio frequency (RF) power amplifier100includes an impedance transformation circuit110, a current unit gain amplifier120, and an output match circuit130. The impedance transformation circuit110is electrically connected to a pre-stage circuit101and a first system voltage VDD1. The current unit gain amplifier120is electrically connected to the impedance transformation circuit110and a second system voltage VDD2. The output match circuit130is electrically connected to the current unit gain amplifier120and an antenna102. The present embodiment does not limit the type of the antenna102.

The impedance transformation circuit110is configured to receive a first input power signal PI1and accordingly output a second input power signal PI2according to an impedance matching parameter by the magnetic energy conversion (i.e., the mutual inductance effect). Furthermore, the impedance transformation circuit110executes a power matching by an impedance transformation, i.e., the higher input impedance is transformed into the lower output impedance or the lower input impedance is transformed into the higher output impedance to achieve the power matching. Accordingly, it can adjust or further increase a power added efficiency (PAE) and a linearity of the RF power amplifier.

The current unit gain amplifier120is configured to receive a second input power signal PI2and accordingly output an output power signal POUT. The current unit gain amplifier120determines a predetermined power gain value based on an impedance reference value. An input impedance of the current unit gain amplifier120is substantially made equal to an input impedance of the RF power amplifier100by executing the impedance transformation circuit110. More specifically, in the present disclosure, the designer can design the predetermined power gain value according to the actual application and can design the impedance reference value by the predetermined power gain value, wherein the impedance reference value is an input impedance of the output match circuit130. In addition, the impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and the predetermined power gain value.

The output match circuit130is configured to receive the output power signal POUT to execute the power matching for providing better efficiency of power matching and accordingly output a RF output signal RFOUT.

The following description further elaborates a working principle of the RF power amplifier100.

Because a transimpedance of the current unit gain amplifier120of the present disclosure has a high-linearity, it will cause there to be a linear relationship between the output power and the input current. When the output current of the pre-stage circuit101is a linear current, it achieves the purpose of the high-linearity power amplifier. Because the power gain of the current unit gain amplifier120is a limited value, the output power of the pre-stage circuit101can be decreased in a condition of fixed transmission power of the antenna, so as to generate a linear current to provide the linear current to the current unit gain amplifier120in a condition of slightly increasing the power consumption of the system. Moreover, the impedance transformation circuit110of the present disclosure is electrically connected between the current unit gain amplifier120and the pre-stage circuit101to amplify the current outputted from the pre-stage circuit101by the magnetic energy conversion within the impedance transformation circuit110, thereby the PAE of the RF power amplifier100can be increased. More specifically, when the impedance transformation circuit110receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the impedance transformation circuit110executes the power matching by the magnetic energy conversion, i.e., higher impedance is transformed into lower impedance or lower impedance is transformed into higher impedance). This means that the impedance transformation circuit110transforms the first input power signal PI1into the second input power signal PI2based on the impedance matching parameter. It is worth mentioning that, in the present embodiment, the impedance matching parameter can be determined by the first system voltage VDD1, the second system voltage VDD2, and the predetermined power gain value, wherein the predetermined power gain value can be designed by the designer according to the actual application. The impedance matching parameter directly affects the transform efficiency of the impedance transformation circuit110, and further affects the efficiency of adjusting the PAE of the pre-stage circuit101.

Next, the current unit gain amplifier120receives the current transmitted from the impedance transformation circuit110or the second input power signal SI2. Because the amplification factor of the current unit gain amplifier120is substantially equal to 1, the current unit gain amplifier120of the present disclosure is analyzed from the power aspect. The power gain (i.e., the predetermined power gain value) of the current unit gain amplifier120is directly proportional to the impedance reference value (i.e., the input impedance of the output match circuit130). Therefore, the designer can design for the predetermined power gain value wanted and gain the impedance reference value based on the predetermined power gain value. It is worth noting that, in the present embodiment, the designer can do optimal design according to the aforementioned values. The present disclosure is not limited thereto.

Afterwards, the current unit gain amplifier120transmits the output power signal POUT to the output match circuit130to execute the power matching of the output terminal. Then the output match circuit130transmits the RF output signal RFOUT to the antenna102to emit the signal correspondingly.

For a specific instruction on an operational process of the RF power amplifier100of the present disclosure, at least one of the embodiments provides further instruction.

In the following embodiments, only parts different from embodiments inFIG. 1are described, and the omitted parts are indicated to be identical to the embodiments inFIG. 1. In addition, similar reference numbers or symbols refer to the same elements.

[Another Embodiment of the RF Power Amplifier]

Please refer toFIG. 2, which shows a block diagram of a RF power amplifier according to another exemplary embodiment of the present disclosure. As shown inFIG. 2, the difference between this embodiment and the above-mentioned embodiment ofFIG. 1is that the impedance transformation circuit110includes a first inductor L1and a second inductor L2. The current unit gain amplifier120includes a first transistor MT1and a first current-fed inductor FL1. A first end of the first inductor L1is electrically connected to the pre-stage circuit101to receive the first input power signal PI1. A second end of the first inductor L1is electrically connected to the first system voltage VDD1, wherein the first inductor L1has a first inductance value. A first end of the second inductor L2is electrically connected to the current unit gain amplifier120to output the second input power signal PI2. A second end of the second inductor L2is electrically connected to the ground voltage GND, wherein the second inductor L2has a second inductance value. A source of the first transistor MT1is electrically connected to the first end of the second inductor L2to receive the second input power signal PI2. A gate of the first transistor MT1is electrically connected to a reference bias voltage VRB, i.e., AC ground. A first end of the first current-fed inductor FL1is electrically connected to a drain of the first transistor MT1and the output match circuit130to output the output power signal POUT. A second end of the first current-fed inductor FL1is electrically connected to the second system voltage VDD2, wherein the first current-fed inductor FL1has a first current-fed inductance value.

The following description further elaborates the working principle of the RF power amplifier200.

In the present embodiment, because the first transistor MT1is common gage (CG) configuration, the transimpedance of the first transistor MT1is linear and the power gain is a limited value. Therefore, in the present disclosure, the impedance transformation circuit110with the first inductor L1and the second inductor L2is electrically connected between the pre-stage circuit101and the first transistor MT1, thereby amplifying the current outputted from the pre-stage circuit101through the magnetic energy conversion of the first inductor L1and the second inductor L2to increase the PAE of the pre-stage circuit101. More specifically, when the first inductor L1receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the first inductor L1transmits the power to the second inductor L2by the magnetic energy conversion (i.e., the mutual inductance effect), wherein the ratio between the current flowing through the second inductor L2and the current flowing through the first inductor L1is the impedance matching parameter. It is worth noting that the impedance matching parameter is defined by the ratio between the first inductance value and the second inductance value. Because the impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and the predetermined power gain value, the designer can design the ratio between the first inductance value and the second inductance value based on the impedance matching parameter, thereby adjusting the PAE of the pre-stage circuit101.

Next, the second inductor L2transmits the current or the second input power signal PI2to the first transistor MT1, wherein the first inductor L1and the second inductor L2transmit the first input power signal PI1to the second input power signal PI2based on the impedance matching parameter. Because the amplification factor of the first transistor MT1(i.e., the first transistor MT1is operated as CG configuration) is substantially equal to 1, the first transistor MT1of the present disclosure is analyzed from the power aspect. The power gain of the first transistor MT1(i.e., the predetermined power gain value) is equal to the product between the resistance value of the input resistor of the output match circuit130and the transconductance value of the first transistor MT1. Therefore, the designer can design an output power wanted of the antenna to gain the resistance value of the input resistor of the output match circuit130based on the second system voltage VDD2. The transconductance value of the first transistor MT1is gained by the predetermined power gain value wanted. The impedance matching parameter of the impedance transformation circuit110is determined by the first system voltage VDD1, the transconductance value of the first transistor MT1, and the output power provided from the pre-stage circuit101(i.e., the power gain of the first transistor MT1is subtracted from the transmission power of the antenna, which is indicated in “dB”). Similarly, the designer can do optimal design according to the aforementioned values. The present disclosure is not limited thereto.

For a specific instruction on an operational process of the RF power amplifier200of the present disclosure, at least one of the following embodiments is for further instruction.

In the following embodiments, only parts different from the embodiments inFIG. 2described, and the omitted parts are indicated to be identical to the embodiments inFIG. 2. In addition, similar reference numbers or symbols refer to the same elements.

[Another Embodiment of the RF Power Amplifier]

Please refer toFIG. 3, which shows a block diagram of a RF power amplifier according to another exemplary embodiment of the present disclosure. As shown inFIG. 3, the difference between this embodiment and the above-mentioned embodiment ofFIG. 2is that the impedance transformation circuit110includes a third inductor L3, a fourth inductor L4, a fifth inductor L5, and a sixth inductor L6. The current unit gain amplifier120includes a second transistor MT2, a third transistor MT3, a second current-fed inductor FL2, a fourth transistor MT4, a fifth transistor MT5, and a third current-fed inductor FL3.

A first end of the third inductor L3is electrically connected to the pre-stage circuit101to receive the first input power signal PI1. A second end of the third inductor L3is electrically connected to the first system voltage VDD1, wherein the third inductor L3has a third inductance value. A first end of the fourth inductor L4is electrically connected to the current unit gain amplifier120to output the second input power signal PI2. A second end of the fourth inductor L4is electrically connected to the ground voltage GND, wherein the fourth inductor L4has a fourth inductance value. The ratio between the third inductance value and the fourth inductance value is designed to be a first high-side impedance matching parameter. A first end of the fifth inductor L5is electrically connected to the pre-stage circuit101to receive the first input power signal PI1. A second end of the fifth inductor L5is electrically connected to the first system voltage VDD1, wherein the fifth inductor L5has a fifth inductance value. A first end of the sixth inductor L6is electrically connected to the current unit gain amplifier120to output the second input power signal PI2. A second end of the sixth inductor L6is electrically connected to the ground voltage GND, wherein the sixth inductor L6has a sixth inductance value. The ratio between the fifth inductance value and the sixth inductance value is designed to be a first low-side impedance matching parameter. A source of the second transistor MT2is electrically connected to the first end of the fourth inductor L4to receive the second input power signal PI2. A gate of the second transistor MT2receives a first bias voltage Vb1. A source of the third transistor MT3is electrically connected to a drain of the second transistor MT2and a gate of the third transistor MT3receives a second bias voltage Vb2, wherein the third transistor MT3is a high-voltage element. A first end of the second current-fed inductor FL2is electrically connected to the source of the third transistor MT3and the output match circuit130to output the output power signal POUT. A second end of the second current-fed inductor FL2is electrically connected to the second system voltage VDD2. A source of the fourth transistor MT4is electrically connected to the first end of the sixth inductor L6to receive the second input power signal PI2. A gate of the fourth transistor MT4receives the first bias voltage Vb1. A source of the fifth transistor MT5is electrically connected to a drain of the fourth transistor MT4. A gate of the fifth transistor MT5receives the second bias voltage Vb2, wherein the fifth transistor MT5is a high-voltage element. A first end of the third current-fed inductor FL3is electrically connected to a drain of the fifth transistor MT5and the output match circuit130to output the output power signal POUT. A second end of the third current-fed inductor FL3is electrically connected to the second system voltage VDD2.

For a specific instruction on an operational process of the RF power amplifier300of the present disclosure, at least one of the embodiments is for further instruction.

In the present embodiment, when the current unit gain amplifier120receives the AC signal, the first bias voltage Vb1and the second bias voltage Vb2is connected to AC ground, i.e., the gate of the second transistor MT2, the gate of the third transistor MT3, the gate of the fourth transistor MT4, and the gate of the fifth transistor MT5can be regarded as electrically connected to the ground voltage. Because the second transistor MT2, the third transistor MT3, the fourth transistor MT4, and the fifth transistor MT5are operated as CG configuration, the transimpedances of the second transistor MT2, the third transistor MT3, the fourth transistor MT4, and the fifth transistor MT5are linear and the power gain is a limited value. The second transistor MT2is substantially equal to the fourth transistor MT4. The third transistor MT3is substantially equal to the fifth transistor MT5. Therefore, in the present disclosure, the impedance transformation circuit110with the third inductor L3, the fourth inductor L4, the fifth inductor L5, and the sixth inductor L6is configured to electrically connect between the pre-stage circuit101and the current unit gain amplifier120, thereby transforming the current outputted from the pre-stage circuit101through the magnetic energy conversion of the third inductor L3, the fourth inductor L4, the fifth inductor L5, and the sixth inductor L6to increase the PAE of the pre-stage circuit101. In the present disclosure, the third inductor L3is substantially equal to the fifth inductor L5. The fourth inductor L4is substantially equal to the sixth inductor L6. Before describing the following embodiment, it is worth noting that the signal outputted from the pre-stage circuit101is a differential input signal. The internal circuit of the RF power amplifier300receives the differential input signal by the architecture of the differential circuit. Moreover, the input impedance of the output match circuit130is a differential input resistor Rid. More specifically, when the third inductor L3receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the third inductor L3transmits the power to the fourth inductor L4by the magnetic energy conversion, wherein the ratio between the current flowing through the fourth inductor L4and the current flowing through the third inductor L3is the first high-side impedance matching parameter. The first high-side impedance matching parameter is defined by the ratio between the third inductance value and the fourth inductance value. It is worth noting that the third inductor L3and the fourth inductor L4transform the input impedance into the output impedance based on the first high-side impedance matching parameter. When the first high-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and a first high-side predetermined power gain value, the designer can design the ratio between the third inductance value and the fourth inductance value based on the first high-side impedance matching parameter, thereby increasing the PAE of the RF power amplifier300.

Next, the fourth inductor L4transmits the differential current or the second input power signal PI2to the second transistor MT2and the third transistor MT3, wherein the third inductor L3and the fourth inductor L4transform the first input power signal PI1into the second input power signal PI2based on the first high-side impedance matching parameter. Because the amplification factor of the second transistor MT2and the third transistor MT3(i.e., the second transistor MT2and the third transistor MT3are operated as CG configuration) is substantially equal to 1, the second transistor MT2and the third transistor MT3of the present disclosure are analyzed from the power aspect. The power gain of the second transistor MT2and the third transistor MT3(i.e., the first high-side predetermined power gain value) is equal to the product between the half resistance value of the differential input resistor Rid and the transconductance value of the second transistor MT2. Therefore, the designer can design for an output power desired of the antenna to gain the resistance value of the differential input resistor Rid based on the second system voltage VDD2. The transconductance value of the second transistor MT2is gained by the predetermined power gain value desired. The first high-side impedance matching parameter of the impedance transformation circuit110is determined by the first system voltage VDD1, the transconductance value of the second transistor MT2, and the output power provided from the pre-stage circuit101(i.e., the power gain of the RF power amplifier300is subtracted from the transmission power of the antenna). Similarly, the designer can do optimal design according to the aforementioned values. The present disclosure is not limited thereto. In other words, the second transistor MT2and the third transistor MT3determine the first high-side predetermined power gain value according to the half resistance value of the differential input resistor Rid. The power gain (i.e., the first high-side predetermined power gain value) of the second transistor MT2and the third transistor MT3are directly proportional to the resistance value of the differential input resistor Rid. Therefore, the designer can design for the first high-side predetermined power gain value desired and gain the resistance value of the differential input resistor Rid based on the first high-side predetermined power gain value. When the first high-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and the first high-side predetermined power gain value, the ratio between the third inductor L3and the fourth inductor L4can be determined by the first high-side impedance matching parameter.

Similarly, the third transistor MT3transmits the output power signal POUT to the output match circuit130to execute the power matching of the output terminal. Then the output match circuit130transmits the RF output signal RFOUT to the antenna102to emit the signal correspondingly.

In another aspect, when the fifth inductor L5receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the fifth inductor L5transmits the power to the sixth inductor L6by the magnetic energy conversion, wherein the ratio between the current flowing through the sixth inductor L6and the current flowing through the fifth inductor L5is a first low-side impedance matching parameter. The first low-side impedance matching parameter is defined by the ratio between the fifth inductance value and the sixth inductance value. It is worth to note that the fifth inductor L5and the sixth inductor L6transform the input impedance into the output impedance based on the first low-side impedance matching parameter. When the first low-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and a first low-side predetermined power gain value, the designer can design the ratio between the fifth inductance value and the sixth inductance value based on the first low-side impedance matching parameter, thereby increasing the PAE of the RF power amplifier300.

Next, the sixth inductor L4transmits the differential current or the second input power signal PI2to the fourth transistor MT4and the fifth transistor MT5, wherein the fifth inductor L5and the six inductor L6transform the first input power signal PI1into the second input power signal PI2based on the first low-side impedance matching parameter. Similarly, because the amplification factor of the second fourth transistor MT4and the fifth transistor MT5(i.e., the fourth transistor MT4and the fifth transistor MT5are operated as CG configuration) is substantially equal to 1, the fourth transistor MT4and the fifth transistor MT5of the present disclosure are analyzed from the power aspect. The power gain of the fourth transistor MT4and the fifth transistor MT5(i.e., the first low-side predetermined power gain value) is equal to the product between the half resistance value of the differential input resistor Rid and the transconductance value of the fourth transistor MT4. Therefore, the designer can design for an output power desired of the antenna to gain the resistance value of the differential input resistor Rid based on the second system voltage VDD2. The transconductance value of the fourth transistor MT4is gained by the predetermined power gain value desired. The first low-side impedance matching parameter of the impedance transformation circuit110is determined by the first system voltage VDD1, the transconductance value of the second transistor MT2, and the output power provided from the pre-stage circuit101(i.e., the power gain of the RF power amplifier300is subtracted from the transmission power of the antenna). Similarly, the designer can do optimal design according to the aforementioned values. The present disclosure is not limited thereto. In other words, the fourth transistor MT4and the fifth transistor MT5determine the first low-side predetermined power gain value according to the half resistance value of the differential input resistor Rid. The power gain (i.e., the first low-side predetermined power gain value) of the fourth transistor MT4and the fifth transistor MT5are directly proportional to the resistance value of the differential input resistor Rid. Therefore, the designer can design for the first low-side predetermined power gain value desired and gain the resistance value of the differential input resistor Rid based on the first low-side predetermined power gain value. When the first low-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and a first low-side predetermined power gain value, the ratio between the fifth inductance value and the sixth inductance value can be determined by the first low-side impedance matching parameter.

For a specific instruction on an operational process of the RF power amplifier300of the present disclosure, at least one of the embodiments is for further instruction.

In the following embodiments, only parts different from embodiments inFIG. 3described, and the omitted parts are indicated to be identical to the embodiments inFIG. 3. In addition, similar reference numbers or symbols refer to the same elements.

[Another Embodiment of the RF Power Amplifier]

Please refer toFIG. 4, which shows a block diagram of a RF power amplifier according to another exemplary embodiment of the present disclosure. As shown inFIG. 4, the difference between this embodiment and the above-mentioned embodiment ofFIG. 3is that the impedance transformation circuit110includes a seventh inductor L7, an eighth inductor L8, a ninth inductor L9, a tenth inductor L10, a first capacitor C1, and a second capacitor C2. A first end of the seventh inductor L7is electrically connected to the pre-stage circuit101to receive the first input power signal PI1. A second end of the seventh inductor L7is electrically connected to the first system voltage VDD1. The seventh inductor L7has a seventh inductance value. A first end of the first capacitor C1is electrically connected to the first end of the seventh inductor L7. A first end of the eighth inductor L8is electrically connected to a second end of the first capacitor C1to output the second input power signal PI2. A second end of the eighth inductor L8is electrically connected to the ground voltage GND. The eighth inductor L8has an eighth inductance value, wherein the ratio between the seventh inductance value and the eighth inductance value is designed to be a second high-side impedance matching parameter. A first end of the ninth inductor L9is electrically connected to the pre-stage circuit101to receive the first input power signal PI1. A second end of the ninth inductor L9is electrically connected to the first system voltage VDD1. The ninth inductor L9has a ninth inductance value. A first end of the second capacitor C2is electrically connected to the first end of the ninth inductor L9. A first end of the tenth inductor L10is electrically connected to a second end of the second capacitor C2to output the second input power signal PI2. A second end of the tenth inductor L10is electrically connected to the ground voltage GND. The tenth inductor L10has a tenth inductance value, wherein the ratio between the ninth inductance value and the tenth inductance value is designed to be a second low-side impedance matching parameter.

Next, when the seventh inductor L7receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the seventh inductor L7transmits the power to the eighth inductor L8through the first capacitor C1, wherein the ratio between the current flowing through the eighth inductor L8and the current flowing through the seventh inductor L7is a second high-side impedance matching parameter. The second high-side impedance matching parameter is defined by the ratio between the seventh inductance value and the eighth inductance value. It is worth noting that the seventh inductor L7and the eighth inductor L8transform the input impedance into the output impedance based on the second high-side impedance matching parameter. When the second high-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and a second high-side predetermined power gain value, the designer can design the ratio between the seventh inductance value and the eighth inductance value based on the second high-side impedance matching parameter, thereby increasing the PAE of the RF power amplifier400. In another aspect, when the ninth inductor L9receives the current transmitted from the pre-stage circuit101or the first input power signal PI1, the ninth inductor L9transmits the power to the tenth inductor L10through the second capacitor C2, wherein the ratio between the current flowing through the tenth inductor L10and the current flowing through the ninth inductor L9is a second low-side impedance matching parameter. The second high-side impedance matching parameter is defined by the ratio between the ninth inductance value and the tenth inductance value. It is worth to note that the ninth inductor L9and the tenth inductor L10transform the input impedance into the output impedance based on the second low-side impedance matching parameter. When the second low-side impedance matching parameter is determined by the first system voltage VDD1, the second system voltage VDD2, and a second low-side predetermined power gain value, the designer can design the ratio between the ninth inductance value and the tenth inductance value based on the second low-side impedance matching parameter, thereby increasing the PAE of the RF power amplifier400. Other working mechanisms of the RF power amplifier400are the same as the aforementioned disclosure of the RF power amplifier300(as shown inFIG. 3), and further descriptions are hereinafter omitted.

[Embodiment of the Method for Increasing the Power Added Efficiency]

Please refer toFIG. 5in conjunction withFIGS. 1-4.FIG. 5shows a flow diagram of a method for increasing power added efficiency (PAE) according to an exemplary embodiment of the present disclosure. From the aforementioned exemplary embodiments, the present invention may generalize a method for increasing the power added efficiency and the linearity, which is adapted for the aforementioned RF power amplifier100,200,300and400. The method for increasing the power added efficiency and the linear is described as follows. First, receiving a first input power signal and correspondingly outputting a second input power signal through an impedance transformation circuit, wherein the impedance transformation circuit executes a power matching by an impedance transformation. Accordingly, it can adjust or further increase the PAE and the linearity of the RF power amplifier (Step S510). Next, receiving the second input power signal and correspondingly outputting an output power signal through a current unit gain amplifier. The current unit gain amplifier determines a predetermined power gain value based on an impedance reference value, wherein, by the impedance transformation circuit, the input impedance of the current unit gain amplifier is substantially equal to the input impedance of the RF power amplifier (Step S520). Afterwards, receiving the output power signal to execute the power matching through an output match circuit and then correspondingly outputting a RF output signal RFOUT, wherein the output match circuit has the impedance reference value (Step S530).

Relevant details of the steps of the method for increasing the PAE are illustrated in the embodiments ofFIGS. 1-4, so their detailed description is omitted. It is clarified that, a sequence of steps inFIG. 5is set for convenience, and thus the sequence of the steps is not used as a condition in demonstrating the embodiments of the present disclosure.

In summary, the exemplary embodiments of the present disclosure provides a RF power amplifier and a method for increasing the PAE, which can provide a linear transimpedance through a current unit gain amplifier to linearly transmit an input current to an output impedance and accordingly generate a linear output power for increasing the PAE of the current unit gain amplifier. Accordingly, it can increase the PAE and the linearity of the RF power amplifier in the condition of receiving a fixed input power.