CN115395903A - Self-biased radio frequency power amplifier with power protection - Google Patents

Abstract

The invention discloses a self-bias radio frequency power amplifier with power protection, which comprises a radio frequency transistor, an input matching network, an output matching network, a drain bias network and a self-bias power protection circuit. The self-bias power protection circuit is connected to the gate and source of the radio frequency transistor, including four MOS transistors; the gates of the three MOS transistors are all connected to the first gate voltage, the drains are all connected to the source of the radio frequency transistor, and the source The poles are all grounded; the three MOS transistors are respectively used as variable resistors, and different resistance values are provided by changing the first gate voltage, so that the gain of the radio frequency transistor in the saturation region is reduced; the gate of the other MOS transistor is connected to the second gate voltage , the drain is connected to the grid of the RF transistor, and the source is grounded; the second grid voltage decreases with the increase of the input power of the RF transistor; the other MOS transistor also acts as a variable resistor, and when the input power of the RF transistor increases When the resistance value becomes larger, it is used to prevent the RF input signal from leaking to the ground.

Description

A self-biased RF power amplifier with power protection

technical field

The invention relates to a radio frequency power amplifier.

Background technique

RF power amplifier is an important device in wireless communication system. In the wireless transceiver system, the radio frequency power amplifier is responsible for amplifying the signal, making the signal transmit farther and making the signal strength higher, and its performance determines the performance of the entire communication system. In some special applications, because the input signal is too large, the RF power amplifier will be burned, so it is particularly important to have a power protection function for the RF power amplifier.

The existing RF power amplifier with power protection mainly feeds back the source of the RF transistor to the gate through the resistor, which can save the gate voltage power supply circuit, and can also realize the RF output under the condition of high power input by adjusting the appropriate resistor. The gain of the transistor drops sharply, preventing the RF power amplifier from being damaged due to oversaturation. The disadvantage of this solution is that an additional circuit is required to adjust the appropriate resistance value.

Contents of the invention

The technical problem to be solved by the present invention is to provide a radio frequency power amplifier, which can provide self-bias and also has power protection, so as to solve the problem that the radio frequency power amplifier will be burned under high input power.

In order to solve the above technical problems, the present invention discloses a self-biased radio frequency power amplifier with power protection, including a radio frequency transistor, an input matching network, an output matching network, a drain bias network and a self-biased power protection circuit. The radio frequency transistor has a gate, a source and a drain. The input matching network is connected to the gate of the radio frequency transistor, and is used for matching with the input impedance of the radio frequency transistor. The output matching network is connected to the drain of the radio frequency transistor for matching with the output impedance of the radio frequency transistor. The drain bias network is between the power supply voltage and the drain of the radio frequency transistor, and is used to provide a drain bias voltage for the radio frequency transistor. The self-bias power protection circuit is connected to the gate and source of the radio frequency transistor, including four MOS transistors; the gates of the three MOS transistors are all connected to the first gate voltage, and the drains are all connected to the source of the radio frequency transistor, and the source The poles are all grounded; the three MOS transistors are respectively used as variable resistors, and different resistance values are provided by changing the first gate voltage, so that the gain of the radio frequency transistor in the saturation region is reduced; the gate of the other MOS transistor is connected to the second gate voltage , the drain is connected to the grid of the RF transistor, and the source is grounded; the second grid voltage decreases with the increase of the input power of the RF transistor; the other MOS transistor also acts as a variable resistor, and when the input power of the RF transistor increases When the resistance value becomes larger, it is used to prevent the RF input signal from leaking to the ground.

Preferably, the radio frequency transistor is a high electron mobility transistor HEMT or a MOS transistor.

Preferably, there is also an input DC blocking capacitor between the input matching network and the gate of the radio frequency transistor.

Preferably, there is an output DC blocking capacitor between the drain of the radio frequency transistor and the output matching network.

Further, the self-bias power protection circuit supplies the drain DC signal of the radio frequency transistor to the gate of the radio frequency transistor through four MOS transistors, and then realizes the gate of the radio frequency transistor under the joint action of the input power of the radio frequency transistor. self-biased.

Alternatively, in the self-bias power protection circuit, any one or more MOS transistors are replaced by a switch diode series resistor.

Alternatively, the other MOS transistor is changed to an inductor.

Further, the self-biased radio frequency power amplifier with power protection also includes a grounding capacitor; the grounding capacitor grounds the source of the radio frequency transistor to prevent the output signal of the radio frequency transistor from leaking to the input terminal.

Further, the four MOS transistors and a grounded capacitor constitute a gate bias network of the self-biased radio frequency power amplifier with power protection.

The technical effect achieved by the invention is that it does not need to control the radio frequency input signal, and does not need to add an attenuator, and realizes special functions through a relatively simple circuit structure. In the invention, a part of the gate bias network is used as a self-bias power protection circuit, which not only realizes the self-bias of the gate voltage of the radio frequency transistor, but also realizes the power protection of the radio frequency transistor under large input power.

Description of drawings

FIG. 1 is a schematic circuit diagram of a self-biased radio frequency power amplifier with power protection disclosed by the present invention.

Fig. 2 is a schematic diagram of the curves of input power and gain of the radio frequency power amplifier disclosed in the present invention.

FIG. 3 is a schematic diagram of the saturation region and the back-off region of an RF transistor.

Explanation of reference numerals in the figure: Q0 is a radio frequency transistor, Q1 to Q4 are MOS transistors, C1 is a grounding capacitor, C2 is an input DC blocking capacitor, C3 is an output DC blocking capacitor, Vin is a radio frequency input signal, Vout is a radio frequency output signal , Vcc is the power supply voltage, Vg1 is the first grid voltage, and Vg2 is the second grid voltage.

Detailed ways

Please refer to FIG. 1 , the self-biased RF power amplifier with power protection disclosed by the present invention includes: RF transistor Q0, an input matching network, an output matching network, a drain bias network and a gate bias network.

The radio frequency transistor Q0 is, for example, HEMT (high-electron-mobility transistor, high electron mobility transistor) or MOS transistor (metal-oxide-semiconductor field-effect transistor, MOSFET for short, metal-oxide-semiconductor field-effect transistor), Has a gate, source and drain.

The input matching network is connected to the gate of the radio frequency transistor Q0, and is used to match the input impedance of the radio frequency transistor Q0, so that the radio frequency input signal Vin enters the radio frequency transistor Q0 with low loss. The input matching network is to match the optimal input impedance of the RF transistor Q0 to the load impedance, so as to prevent the device from being damaged due to excessive reflection of the RF input signal Vin. Preferably, there is an input DC blocking capacitor C2 between the input matching network and the gate of the RF transistor Q0 to prevent the DC signal from leaking to the load terminal, so as to allow the DC signal to flow into the RF transistor Q0.

The output matching network is connected to the drain of the radio frequency transistor Q0 to match the output impedance of the radio frequency transistor Q0 so that the signal of the radio frequency transistor is output with low loss to obtain the radio frequency output signal Vout. The output matching network is to match the optimal output impedance of the RF transistor Q0 to the load impedance, so that the RF transistor Q0 can complete the maximum power transmission and reduce the loss. Preferably, there is an output DC blocking capacitor C3 between the drain of the RF transistor Q0 and the output matching network to prevent the DC signal from leaking to the load terminal, so as to allow the DC signal to flow into the RF transistor Q0.

The drain bias network is between the power supply voltage Vcc and the drain of the radio frequency transistor Q0, and is used to provide the drain bias voltage for the radio frequency transistor Q0, and prevent the energy of the radio frequency transistor Q0 from leaking out, and prevent the AC signal from leaking to the DC end.

The gate bias network is connected to the gate and source of the radio frequency transistor Q0, and includes four MOS transistors Q1 to Q4 and a grounded capacitor C1. The grounding capacitor C1 grounds the source of the RF transistor Q0 to prevent the output signal of the RF transistor Q0 from leaking to the input terminal, prevent the drain energy of the RF transistor Q0 from leaking to the gate, and play the role of RF bypass. Four MOS transistors Q1 to Q4 form a self-bias power protection circuit. In the self-bias power protection circuit, the gates of the three MOS transistors Q1 to Q3 are all connected to the first gate voltage Vg1, the drains of the three MOS transistors Q1 to Q3 are all connected to the source of the radio frequency transistor Q0, and the three MOS transistors Q1 to Q3 are connected to the source of the radio frequency transistor Q0. The sources of transistors Q1 to Q3 are all grounded. The three MOS transistors Q1 to Q3 respectively provide a variable resistance, and provide different resistance values by changing the gate bias voltage (first gate voltage Vg1), which is used to change the gain of the radio frequency transistor Q0, so that the radio frequency transistor Q0 is saturated The gain of the zone drops sharply, thereby realizing the function of power protection for the radio frequency transistor Q0. The gate of the MOS transistor Q4 is connected to the second gate voltage Vg2, the drain of the MOS transistor Q4 is connected to the gate of the RF transistor Q0, and the source of the MOS transistor Q4 is grounded. The second gate voltage Vg2 decreases as the input power of the RF transistor Q0 increases, the purpose is to use the MOS transistor Q4 as a variable resistor, and the resistance of the MOS transistor Q4 becomes larger when the input power of the RF transistor Q0 increases. The MOS transistor Q4 is used to prevent the RF input signal Vin from leaking to the ground, and at the same time can change (increase or decrease) the gain of the backoff region of the RF transistor Q0.

The self-bias power protection circuit is to supply the drain DC signal of the radio frequency transistor Q0 to the gate of the radio frequency transistor Q0 through four MOS transistors Q1 to Q4, and then realize the radio frequency transistor Q0 under the combined action of the input power of the radio frequency transistor Q0. The bias circuit of the gate, that is, to achieve "self-biasing".

In the self-bias power protection circuit, the four MOS transistors Q1 to Q4 all function as variable resistors. Alternatively, any one or more MOS transistors can also be used as variable resistors by switching diodes in series with resistors. Wherein, the MOS transistor Q4 can also be changed into an inductor. When the input power of the radio frequency transistor Q0 is very large and reaches or exceeds the rated power of the radio frequency transistor Q0 (shown schematically as 22dBm in FIG. 2 ), by changing the two gate voltages Vg1 and Vg2 of the four MOS transistors Q1 to Q4, the The four MOS transistors Q1 to Q4 are adjusted to different resistance values, which drives the gain of the radio frequency transistor Q0 to drop sharply, thereby realizing power protection for the radio frequency transistor Q0, as shown in FIG. 2 .

Please refer to Figure 3, the backoff region of the RF transistor refers to the region where the gain is compressed by more than 1dB, and the saturation region of the RF transistor refers to the region of the maximum output power. The cut-off point between the backoff zone and the saturation zone is the output power corresponding to 1dB of gain compression (that is, the rated power). The power rating of a transistor is related to the physical properties of the transistor. If referring to FIG. 2, if the rated power of the RF transistor Q0 is 22dBm, it can be considered that the input power above 22dBm is the saturation region of the RF transistor, and the input power below 22dBm is the fallback region of the RF transistor.

Compared with the prior art, the present invention has the following beneficial technical effects. First, the present invention sets a self-bias power protection circuit for the RF transistor, which not only realizes the self-biasing of the gate voltage of the RF transistor, but also realizes the power protection of the RF transistor under high input power. Second, the present invention does not require additional power attenuation circuits and power inspection circuits, which can greatly save circuit area and power consumption. Third, the present invention does not need to control or limit the power of the radio frequency input signal, and is applicable to a wider range of radio frequency power amplifiers.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Various modifications and variations of the present invention will occur to those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A self-biased radio frequency power amplifier with power protection is characterized in that it comprises a radio frequency transistor, an input matching network, an output matching network, a drain bias network and a self-biased power protection circuit; The radio frequency transistor has a gate, a source and a drain; The input matching network is connected to the gate of the radio frequency transistor, and is used to match the input impedance of the radio frequency transistor; The output matching network is connected to the drain of the radio frequency transistor, and is used to match the output impedance of the radio frequency transistor; The drain bias network is between the power supply voltage and the drain of the radio frequency transistor, and is used to provide a drain bias voltage for the radio frequency transistor; The self-bias power protection circuit is connected to the gate and source of the radio frequency transistor, including four MOS transistors; the gates of the three MOS transistors are all connected to the first gate voltage, and the drains are all connected to the source of the radio frequency transistor, and the source The poles are all grounded; the three MOS transistors are respectively used as variable resistors, and different resistance values are provided by changing the first gate voltage, so that the gain of the radio frequency transistor in the saturation region is reduced; the gate of the other MOS transistor is connected to the second gate voltage , the drain is connected to the grid of the RF transistor, and the source is grounded; the second gate voltage decreases with the increase of the input power of the RF transistor; the other MOS transistor also acts as a variable resistor, when the input power of the RF transistor increases When the resistance value becomes larger, it is used to prevent the RF input signal from leaking to the ground. 2. The self-biased radio frequency power amplifier with power protection according to claim 1, wherein the radio frequency transistor is a high electron mobility transistor (HEMT) or a MOS transistor. 3. The self-biased radio frequency power amplifier with power protection according to claim 1, characterized in that, there is also an input DC blocking capacitor between the input matching network and the gate of the radio frequency transistor. 4. The self-biased radio frequency power amplifier with power protection according to claim 1, characterized in that an output DC blocking capacitor is also provided between the drain of the radio frequency transistor and the output matching network. 5. The self-biased radio frequency power amplifier with power protection according to claim 1, characterized in that, the self-biased power protection circuit supplies the radio frequency transistor with the drain DC signal of the radio frequency transistor through four MOS transistors The grid, and the self-biasing of the grid of the radio frequency transistor is realized under the joint action of the input power of the radio frequency transistor. 6. The self-biased radio frequency power amplifier with power protection according to claim 1, characterized in that, in the self-biased power protection circuit, any one or more MOS transistors are replaced by switching diode series resistors. 7. The self-biased radio frequency power amplifier with power protection according to claim 1, wherein the other MOS transistor is changed to an inductor. 8. The self-biased radio frequency power amplifier with power protection according to claim 1, wherein the self-biased radio frequency power amplifier with power protection also includes a ground capacitor; the ground capacitor connects the source of the radio frequency transistor The pole is grounded to prevent the output signal of the RF transistor from leaking to the input. 9. The self-biased RF power amplifier with power protection according to claim 8, characterized in that, the four MOS transistors and a ground capacitor constitute the gate of the self-biased RF power amplifier with power protection extremely biased network.

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