Radio frequency front-end circuit shared by matching network

Abstract

The invention discloses a radio frequency front-end circuit shared by a matching network, and belongs to the technical field of radio frequency front-end circuit design, the radio frequency front-end circuit comprises a low noise amplifier, a power amplifier, a series resonance network, a power amplifier output matching network, an antenna ANT and a power supply voltage VDD; wherein the low-noise amplifier and the power amplifier are electrically connected to the left and right ends of the antenna respectively; when the low-noise amplifier works, the power amplifier output matching network is in an open circuit state, and at the moment, the low-noise amplifier realizes matching through the series inductor Lg. When the power amplifier works, the matching inductor Lg and the matching inductor C2 resonate at two times of working frequency, so that a shunt capacitor needing to counteract the Lg is saved, and meanwhile, the linearity of the power amplifier is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency front-end circuit design, and in particular relates to a radio frequency front-end circuit shared by a matching network. Background Art

[0002] In a radio frequency transceiver, a power amplifier and a low noise amplifier have their own matching networks. When one of them is working, the matching network of the other will have a significant impact on the performance of the circuit, resulting in deterioration of the performance of the radio frequency transceiver circuit. Summary of the invention

[0003] The object of the present invention is to provide a radio frequency front-end circuit with a shared matching network, in which the power amplifier and the low noise amplifier not only do not affect each other but also help improve their performance, thereby solving the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: a radio frequency front-end circuit shared by a matching network, the radio frequency front-end circuit comprising a low noise amplifier, a power amplifier, a series inductor Lg, a capacitor C2, a power amplifier output matching network, an antenna ANT and a power supply voltage VDD;

[0005] The low noise amplifier and the power amplifier are electrically connected to the left and right ends of the antenna respectively, and the series inductor Lg, the antenna ANT and the power amplifier output matching network are electrically connected between the low noise amplifier and the power amplifier from left to right in sequence;

[0006] When the low noise amplifier is working, the power amplifier output matching network is in an open circuit state, and the low noise amplifier achieves matching through the series inductor Lg; when the power amplifier is working, the series inductor Lg and the capacitor C2 resonate at twice the operating frequency, short-circuiting the second harmonic of the power amplifier and improving the linearity of the power amplifier.

[0007] Preferably, the power amplifier output matching network includes an inductor L1, a capacitor C1, a capacitor Cp, a capacitor Ld and a switch SW1;

[0008] Among them, one end of the inductor L1 is connected in series with one end of the capacitor C1, the other end of the capacitor C1 is connected in series with the power amplifier, one end of the capacitor Ld is connected in parallel with the power amplifier, the other end of the capacitor Ld is connected to the power supply voltage VDD, one end of the capacitor Cp is connected in parallel with the power amplifier, one end of the switch SW1 is connected in parallel with one end of the capacitor C1, and the other ends of the capacitor Cp and the switch SW1 are both grounded.

[0009] Preferably, the series resonant network includes an inductor Lg, a capacitor C2 and a switch SW2;

[0010] Among them, one end of the inductor Lg is connected in series with the low noise amplifier, the other end of the inductor Lg is connected in series with the inductor L1, one end of the capacitor C2 is connected in parallel with the inductor Lg, the other end of the capacitor C2 is connected in series with one end of the switch SW2, and the other end of the switch SW2 is grounded.

[0011] Preferably, the antenna ANT is connected in parallel to the connection between the inductor Lg and the inductor L1.

[0012] Preferably, in the RF front-end circuit shared by the matching network, when the low-noise amplifier is working, the switch SW2 is disconnected, the capacitor C2 is not working, the switch SW1 is closed, and the power amplifier output matching network is open; when the power amplifier is working, the switch SW1 is disconnected, the switch SW2 is turned on, the inductor L1 and the capacitor C1 as well as the capacitor Cp and the capacitor Ld form a parallel class E power amplifier, and the inductor Lg and the capacitor C2 form a series resonant network, which resonates at twice the operating frequency, short-circuiting the second harmonic of the power amplifier and improving the linearity of the power amplifier.

[0013] Preferably, in the RF front-end circuit shared by the matching network, the switch SW1 and the switch SW2 are not turned on at the same time.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention ingeniously resonates the matching inductor Lg of the low noise amplifier with C2 at twice the operating frequency when the power amplifier is operating, which not only saves the parallel capacitor required to offset Lg, but also improves the linearity of the power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 4 is a circuit diagram of the matching network of the present invention.

[0017] Figure 2 This is a simulation result diagram of the matching network structure of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In a radio frequency transceiver, a power amplifier and a low noise amplifier have their own matching networks. When one of them is working, the matching network of the other will have a significant impact on the performance of the circuit, resulting in deterioration of the performance of the radio frequency transceiver circuit.

[0020] In order to solve the problems existing in the above-mentioned prior art, Figure 1As shown, an embodiment of the present invention provides a radio frequency front-end circuit shared by a matching network, the radio frequency front-end circuit comprising a low noise amplifier, a power amplifier, a series inductor Lg, a capacitor C2, a power amplifier output matching network, an antenna ANT and a power supply voltage VDD;

[0021] The low noise amplifier and the power amplifier are electrically connected to the left and right ends of the antenna respectively, and the series inductor Lg, the antenna ANT and the power amplifier output matching network are electrically connected between the low noise amplifier and the power amplifier from left to right in sequence;

[0022] When the low noise amplifier is working, the power amplifier output matching network is in an open circuit state, and the low noise amplifier achieves matching through the series inductor Lg; when the power amplifier is working, Lg resonates with C1 at twice the operating frequency, thereby short-circuiting the second harmonic of the power amplifier and improving the linearity of the power amplifier.

[0023] In this embodiment, the power amplifier output matching network includes an inductor L1, a capacitor C1, a capacitor Cp, a capacitor Ld and a switch SW1;

[0024] Among them, one end of the inductor L1 is connected in series with one end of the capacitor C1, the other end of the capacitor C1 is connected in series with the power amplifier, one end of the capacitor Ld is connected in parallel with the power amplifier, the other end of the capacitor Ld is connected to the power supply voltage VDD, one end of the capacitor Cp is connected in parallel with the power amplifier, one end of the switch SW1 is connected in parallel with one end of the capacitor C1, and the other ends of the capacitor Cp and the switch SW1 are both grounded.

[0025] In this embodiment, the series resonant network includes an inductor Lg, a capacitor C2 and a switch SW2;

[0026] Among them, one end of the inductor Lg is connected in series with the low noise amplifier, the other end of the inductor Lg is connected in series with the inductor L1, one end of the capacitor C2 is connected in parallel with the inductor Lg, the other end of the capacitor C2 is connected in series with one end of the switch SW2, and the other end of the switch SW2 is grounded.

[0027] In this embodiment, the antenna ANT is connected in parallel to the connection point between the inductor Lg and the inductor L1 .

[0028] In this embodiment, the RF front-end circuit shared by the matching network, when the low noise amplifier is working, the switch SW2 is disconnected, the capacitor C2 is not working, the switch SW1 is closed, and the power amplifier output matching network is open; when the power amplifier is working, the switch SW1 is disconnected, the switch SW2 is connected, the inductor L1 and the capacitor C1 as well as the capacitor Cp and the capacitor Ld form a parallel Class E power amplifier, the inductor Lg and the capacitor C2 resonate at twice the operating frequency, short-circuiting the second harmonic of the power amplifier to improve the linearity of the power amplifier.

[0029] In this embodiment, in the RF front-end circuit shared by the matching network, the switch SW1 and the switch SW2 are not turned on at the same time.

[0030] First, the real part of the input impedance of the low noise amplifier is designed to be around 50 ohms, and the imaginary part is capacitive. When the low noise amplifier is working, SW2 is disconnected, C2 does not work, SW1 is closed, the matching network of the power amplifier is open, and the series inductor Lg offsets the imaginary part of the capacitive input impedance of the low noise amplifier to achieve a 50 ohm match.

[0031] The power amplifier adopts a parallel class E power amplifier structure. According to the output power requirement and the equivalent resistance of 50 ohms, the power supply voltage is calculated, and then the Cp capacitance and Ld inductance are calculated. The formula is as follows:

[0032]

[0033] Where R is the equivalent resistance and ω is the angular frequency of the operating frequency.

[0034] When the power amplifier is working, SW1 is disconnected and SW2 is connected. Lg and C2 resonate at 2ω, short-circuiting the second harmonic of the power amplifier and helping to improve the linearity of the power amplifier.

[0035] Figure 2 The above simulation results are the results of the matching network structure of the present invention, and the following are the Lg and C2 networks without the dashed boxes. From the two data, it can be seen that the difference between the first and second harmonics is increased from the original 15.4dB to 55dB.

[0036] The present invention ingeniously resonates the matching inductor Lg of the low noise amplifier with C2 at twice the operating frequency when the power amplifier is operating, thereby not only saving the parallel capacitor required to offset Lg, but also improving the linearity of the power amplifier.

[0037] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0038] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A radio frequency front-end circuit shared by a matching network, characterized in that: The radio frequency front-end circuit includes a low noise amplifier, a power amplifier, a series inductor Lg, a capacitor C2, a power amplifier output matching network, an antenna ANT and a power supply voltage VDD; The low noise amplifier and the power amplifier are electrically connected to the left and right ends of the antenna respectively, and the series inductor Lg, the antenna ANT and the power amplifier output matching network are electrically connected between the low noise amplifier and the power amplifier from left to right in sequence; When the low noise amplifier is working, the power amplifier output matching network is in an open circuit state, and the low noise amplifier is matched through the series inductor Lg; when the power amplifier is working, the series inductor Lg and the capacitor C2 resonate at twice the operating frequency, short-circuiting the second harmonic of the power amplifier and improving linearity.

2. The RF front-end circuit shared by the matching network according to claim 1, characterized in that: The power amplifier output matching network includes an inductor L1, a capacitor C1, a capacitor Cp, a capacitor Ld and a switch SW1; Among them, one end of the inductor L1 is connected in series with one end of the capacitor C1, the other end of the capacitor C1 is connected in series with the power amplifier, one end of the capacitor Ld is connected in parallel with the power amplifier, the other end of the capacitor Ld is connected to the power supply voltage VDD, one end of the capacitor Cp is connected in parallel with the power amplifier, one end of the switch SW1 is connected in parallel with one end of the capacitor C1, and the other ends of the capacitor Cp and the switch SW1 are both grounded.

3. The RF front-end circuit shared by the matching network according to claim 2, characterized in that: The series matching inductor Lg, capacitor C2 and switch SW2; Among them, one end of the inductor Lg is connected in series with the low noise amplifier, the other end of the inductor Lg is connected in series with the inductor L1, one end of the capacitor C2 is connected in parallel with the inductor Lg, the other end of the capacitor C2 is connected in series with one end of the switch SW2, and the other end of the switch SW2 is grounded.

4. The RF front-end circuit shared by the matching network according to claim 3, characterized in that: The antenna ANT is connected in parallel to the connection point between the inductor Lg and the inductor L1.

5. The RF front-end circuit shared by the matching network according to claim 3, characterized in that: The RF front-end circuit shared by the matching network, when the low noise amplifier is working, the switch SW2 is disconnected, the capacitor C2 does not work, the switch SW1 is closed, and the power amplifier output matching network presents high impedance at the working frequency; when the power amplifier is working, the switch SW1 is disconnected, the switch SW2 is connected, the inductor L1 and the capacitor C1 as well as the capacitor Cp and the capacitor Ld form a parallel E-class power amplifier, the inductor Lg and the capacitor C2 resonate at twice the working frequency, short-circuiting the second harmonic of the power amplifier and improving the linearity of the power amplifier.

6. The radio frequency front-end circuit shared by the matching network according to claim 5, characterized in that: In the RF front-end circuit shared by the matching network, the switch SW1 and the switch SW2 are not turned on at the same time.

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