Modulation spectrum circuit and power amplifier

Abstract

The application provides a modulation spectrum circuit and a power amplifier, wherein the modulation spectrum circuit comprises an operational amplifier, a field effect transistor, a first resistor, a first control circuit, a second control circuit, a second resistor, a third control circuit, a third resistor and a comparison circuit; a first end of the first resistor and a drain of the field effect transistor are connected and serve as an output end of the modulation spectrum circuit, and are used for outputting a modulation signal with a preset modulation spectrum to a final stage amplifier in the power amplifier; an input end of the second control circuit is used for connecting a feedback signal formed by an output current of the final stage amplifier; and the comparison circuit is used for controlling the conduction or the turn-off of the first control circuit, the second control circuit and the third control circuit. The modulation spectrum circuit of the application can not only meet the modulation spectrum under the condition of large power output, but also optimize the modulation spectrum under the condition of small power output.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a modulation spectrum circuit and a power amplifier. Background Technology

[0002] The generation of modulation spectrum in power amplifiers (PAs) fabricated using complementary metal-oxide-semiconductor (CMOS) technology is a complex radio frequency phenomenon. This modulation spectrum, also known as the modulation spectrum, is mainly generated by the nonlinear characteristics of the power amplifier, power supply modulation effect, impedance mismatch problem, and memory effect.

[0003] The power supply modulation effect originates from the impact of power supply voltage fluctuations on the power amplifier's performance during operation. Noise on the power supply line is coupled into the power amplifier's circuitry through the power supply pins and directly modulates the output signal. This coupling results in modulation components in the output signal that are related to the power supply noise frequency.

[0004] like Figure 1 As shown, the modulation spectrum circuit of the related technology mainly includes an operational amplifier OPA, a field-effect transistor M, a first resistor R1, a second resistor R2, and a third resistor R3. Among them, the non-inverting input terminal of the operational amplifier OPA is used to connect the ramp voltage vramp, the source of the field-effect transistor M is used to connect the working voltage vdd, and the drain of the field-effect transistor M serves as the output terminal vout of the modulation spectrum circuit, which is used to output a modulation signal with a preset modulation spectrum. This modulation signal is a modulated voltage signal, which can be understood as a voltage signal with a specific modulation spectrum. One end of the first resistor R1 is used to connect the feedback signal ifb, and one end of the second resistor R2 is used to connect the bandgap reference voltage vbg.

[0005] For example, a power amplifier may include a primary amplifier 1, a second-stage amplifier 2, a third-stage amplifier 3, a final-stage amplifier 4, and a matching circuit 5. The input of the primary amplifier 1 is used to receive the radio frequency signal RFin, and the output of the matching circuit 5 is connected to an antenna. When the aforementioned modulation spectrum circuit is applied to this power amplifier, the output vout of the modulation spectrum circuit is used to provide a modulation signal with a preset modulation spectrum to the final-stage amplifier 4.

[0006] To optimize the modulation spectrum of the aforementioned modulation spectrum circuit, the related technology adopts the method of optimizing the operational amplifier OPA, the connected bandgap reference voltage VBG, and the connected feedback signal IFB. This method can only guarantee the modulation spectrum under high power output conditions. When the power decreases, the characteristics of the operational amplifier OPA will change, and the power amplifier will enter the linear segment. At this time, the noise modulation effect will increase, which will eventually lead to a deterioration of the modulation spectrum. That is, although the modulation spectrum circuit in the related technology can meet the modulation spectrum under high power output conditions, its modulation spectrum will deteriorate under low power output conditions.

[0007] Therefore, there is an urgent need for a new modulation spectrum circuit and power amplifier to solve the above problems. Summary of the Invention

[0008] To address the shortcomings of the aforementioned related technologies, this invention proposes a novel modulation spectrum circuit and power amplifier to solve the problem that while the modulation spectrum circuit in the related technologies can meet the modulation spectrum requirements under high power output conditions, its modulation spectrum deteriorates under low power output conditions.

[0009] To solve the above-mentioned technical problems, in a first aspect, the present invention provides a modulation spectrum circuit applied to a power amplifier, which includes an operational amplifier, a field-effect transistor, a first resistor, a first control circuit, a second control circuit, a second resistor, a third control circuit, a third resistor, and a comparator circuit.

[0010] The non-inverting input of the operational amplifier is used to connect to the ramp voltage;

[0011] The gate of the field-effect transistor is connected to the output terminal of the operational amplifier, and the source of the field-effect transistor is used to connect to the operating voltage.

[0012] The drain of the field-effect transistor serves as the output terminal of the modulation spectrum circuit, used to output a modulation signal with a preset modulation spectrum to the final stage amplifier in the power amplifier.

[0013] The first terminal of the first resistor is connected to the drain of the field-effect transistor;

[0014] The first terminal of the first control circuit is connected to the second terminal of the first resistor, and the second terminal of the first control circuit is connected to the first terminal of the first resistor.

[0015] The input terminal of the second control circuit is used to receive the feedback signal formed by the output current of the final stage amplifier in the power amplifier, and the output terminal of the second control circuit is connected to the second terminal of the first resistor;

[0016] The first end of the second resistor is connected to the inverting input of the operational amplifier and the output of the second control circuit, respectively.

[0017] The input terminal of the third control circuit is used to connect to the bandgap reference voltage, and the output terminal of the third control circuit is connected to the second terminal of the second resistor.

[0018] The first end of the third resistor is connected to the first end of the second resistor, and the second end of the third resistor is grounded;

[0019] The input terminal of the comparator circuit is used to receive the ramp voltage, and the output terminal of the comparator circuit is used to output control signals to the first control circuit, the second control circuit and the third control circuit respectively according to the ramp voltage, so as to control the first control circuit, the second control circuit and the third control circuit to be turned on or off.

[0020] Preferably, the first control circuit includes a first single-pole single-throw switch; the common terminal of the first single-pole single-throw switch serves as the second terminal of the first control circuit, and the normally open terminal of the first single-pole single-throw switch serves as the first terminal of the first control circuit.

[0021] Preferably, the second control circuit includes a second single-pole single-throw switch; the common terminal of the second single-pole single-throw switch serves as the output terminal of the second control circuit, and the normally open terminal of the second single-pole single-throw switch serves as the input terminal of the second control circuit.

[0022] Preferably, the third control circuit includes a third single-pole single-throw switch; the common terminal of the third single-pole single-throw switch serves as the output terminal of the third control circuit, and the normally open terminal of the third single-pole single-throw switch serves as the input terminal of the third control circuit.

[0023] Preferably, the comparison circuit includes a comparator and an inverter;

[0024] The non-inverting input of the comparator serves as the input of the comparator circuit, and the inverting input of the comparator is used to connect to the reference voltage. The output of the comparator serves as the first output of the comparator circuit, and is used to output a first switch control signal to the common terminal of the second single-pole single-throw switch and the common terminal of the third single-pole single-throw switch, respectively, so as to control the conduction or de-conduction of the second single-pole single-throw switch and the third single-pole single-throw switch.

[0025] The input terminal of the inverter is connected to the output terminal of the comparator. The output terminal of the inverter serves as the second output terminal of the comparator circuit, which is used to output a second switch control signal to the common terminal of the first single-pole single-throw switch to control the first single-pole single-throw switch to be turned on or off.

[0026] Preferably, the modulation spectrum circuit further includes a fourth resistor; the fourth resistor is connected in series between the second end of the first resistor and the output end of the second control circuit.

[0027] Secondly, the present invention provides a power amplifier, which includes the modulation spectrum circuit as described above and a primary amplifier, a second-stage amplifier, a third-stage amplifier, a final-stage amplifier and a matching circuit connected in sequence; the input terminal of the primary amplifier is used to receive a radio frequency signal, and the output terminal of the matching circuit is used to connect to an antenna.

[0028] Compared with related technologies, the modulation spectrum circuit of the present invention, through the design of the connection of operational amplifier, field-effect transistor, first resistor, first control circuit, second control circuit, second resistor, third control circuit, third resistor, and comparator circuit, and the limitation of the output terminal of the comparator circuit to output control signals to the first control circuit, second control circuit, and third control circuit respectively according to the ramp voltage, so as to control the conduction or cutoff of the first control circuit, second control circuit, and third control circuit. In this way, under high power conditions, the first control circuit can be turned off while the second and third control circuits are both turned on to meet the modulation spectrum under high power output conditions. When applied to a power amplifier, this improves the output power and efficiency of the power amplifier. Under low power output conditions, the first control circuit is turned on while the second and third control circuits are both turned off to cut off the noise generated by the feedback branches of the second and third control circuits, thereby optimizing the modulation spectrum under low power output conditions. Attached Figure Description

[0029] The present invention will now be described in detail with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and more readily understood through the detailed description following the accompanying drawings. In the drawings:

[0030] Figure 1 A circuit diagram showing the modulation spectrum circuit provided for related technologies applied to a power amplifier.

[0031] Figure 2 A circuit block diagram of a power amplifier provided in an embodiment of the present invention;

[0032] Figure 3 The circuit diagram of the ramp voltage detection circuit in the power amplifier provided in the embodiment of the present invention. Detailed Implementation

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This invention provides a modulation spectrum circuit 100, combined with... Figure 2 and Figure 3 As shown, it includes an operational amplifier OPA, a field-effect transistor M, a first resistor R1, a first control circuit 1, a second control circuit 2, a second resistor R2, a third control circuit 3, a third resistor R3, and a comparator circuit 4.

[0038] The modulation spectrum circuit 100 is applied to the power amplifier 200, which is fabricated using complementary metal-oxide-semiconductor (CMOS) technology.

[0039] The non-inverting input of the operational amplifier OPA is used to connect the ramp voltage Vramp.

[0040] The gate of the field-effect transistor M is connected to the output of the operational amplifier OPA, and the source of the field-effect transistor M is connected to the operating voltage VDD.

[0041] The drain of the field-effect transistor M serves as the output terminal VOUT of the modulation spectrum circuit 100, which is used to output a modulated signal with a preset modulation spectrum to the final stage amplifier 40 in the power amplifier 200. This modulated signal is a modulated voltage signal, which can also be understood as a voltage signal with a specific or preset modulation spectrum.

[0042] The first terminal of the first resistor R1 is connected to the drain of the field-effect transistor M.

[0043] The first terminal of the first control circuit 1 is connected to the second terminal of the first resistor R1, and the second terminal of the first control circuit 1 is connected to the first terminal of the first resistor R1.

[0044] In this embodiment, the first control circuit 1 includes a first single-pole single-throw switch S1; the common terminal of the first single-pole single-throw switch S1 serves as the second terminal of the first control circuit 1, and the normally open terminal of the first single-pole single-throw switch S1 serves as the first terminal of the first control circuit 1.

[0045] The input terminal of the second control circuit 2 is used to receive the feedback signal IFB formed by the output current of the final stage amplifier 40 in the power amplifier 200. The output terminal of the second control circuit 2 is connected to the second terminal of the first resistor R1. The branch where the second control circuit 2 is located serves as the first feedback branch.

[0046] In this embodiment, the second control circuit 2 includes a second single-pole single-throw switch S2; the common terminal of the second single-pole single-throw switch S2 serves as the output terminal of the second control circuit 2, and the normally open terminal of the second single-pole single-throw switch S2 serves as the input terminal of the second control circuit 2.

[0047] The first end of the second resistor R2 is connected to the inverting input of the operational amplifier OPA and the output of the second control circuit 2.

[0048] The input terminal of the third control circuit 3 is used to connect the bandgap reference voltage VBG, and the output terminal of the third control circuit 3 is connected to the second terminal of the second resistor R2; the branch where the second resistor R2 and the third control circuit 3 are located serves as the second feedback branch.

[0049] In this embodiment, the third control circuit 3 includes a third single-pole single-throw switch S3; the common terminal of the third single-pole single-throw switch S3 serves as the output terminal of the third control circuit 3, and the normally open terminal of the third single-pole single-throw switch S3 serves as the input terminal of the third control circuit 3.

[0050] The first end of the third resistor R3 is connected to the first end of the second resistor R2, and the second end of the third resistor R3 is grounded.

[0051] The input terminal of the comparator circuit 4 is used to connect the ramp voltage Vramp, and the output terminal of the comparator circuit 4 is used to output control signals to the first control circuit 1, the second control circuit 2 and the third control circuit 3 respectively according to the ramp voltage Vramp, so as to control the first control circuit 1, the second control circuit 2 and the third control circuit 3 to turn on or off.

[0052] In this embodiment, the comparator circuit 4 includes a comparator COMP and an inverter INV.

[0053] The non-inverting input of comparator COMP serves as the input of comparator circuit 4, and the inverting input of comparator COMP is used to connect the reference voltage VREF. The output of comparator COMP serves as the first output of comparator circuit 4, and is used to output the first switch control signal det to the common terminal of the second single-pole single-throw switch S2 and the common terminal of the third single-pole single-throw switch S3, respectively, so as to control the conduction or cutoff of the second single-pole single-throw switch S2 and the third single-pole single-throw switch S3.

[0054] The input of inverter INV is connected to the output of comparator COMP. The output of inverter INV serves as the second output of comparator circuit 4, used to output a second switch control signal detN to the common terminal of the first single-pole single-throw switch S1, thereby controlling the first single-pole single-throw switch S1 to turn on or off. Inverter INV is used to flip the received first switch control signal det to obtain the second switch control signal detN.

[0055] The modulation spectrum circuit 100 in this embodiment also includes a fourth resistor R4; the fourth resistor R4 is connected in series between the second end of the first resistor R1 and the output end of the second control circuit 2, that is, the first end of the fourth resistor R4 is connected to the second end of the first resistor R1, and the second end of the fourth resistor R4 is connected to the output end of the second control circuit 2.

[0056] The modulation spectrum circuit 100 in this embodiment works as follows: a ramp voltage Vramp is connected to the non-inverting input of comparator COMP, and a reference voltage VREF is connected to the inverting input of comparator COMP. After the ramp voltage Vramp and the reference voltage VREF are compared by comparator COMP, a first switch control signal det is output. After receiving the first switch control signal det, inverter INV flips the first switch control signal det to output a second switch control signal detN. Both the first switch control signal det and the second switch control signal detN are level signals.

[0057] When the ramp voltage Vramp is less than the reference voltage VREF: the first switch control signal det is low, controlling both the second single-pole single-throw switch S2 and the third single-pole single-throw switch S3 to turn off, thus cutting off the first and second feedback branches and no longer connecting the feedback signal IFB and the bandgap reference voltage VBG; the second switch control signal detN is high, controlling the first single-pole single-throw switch S1 to turn on, meaning the signal no longer passes through the first resistor R1. At this time, the voltage output at the output terminal VOUT of the modulation spectrum circuit 100 is Vramp. (R2+R3) / R2, where R2 is the resistance value of the second resistor R2 and R3 is the resistance value of the third resistor R3; the corresponding voltage coefficient will decrease, which can not only greatly reduce the noise contribution of the first feedback branch and the second feedback branch, but also reduce the contribution of each residual noise at the feedback point B to the output terminal VOUT of the modulation spectrum circuit 100. At this time, as long as the operational amplifier OPA and the final stage amplifier 40 are designed reasonably, the total noise voltage of the output terminal VOUT of the modulation spectrum circuit 100 can be well controlled, thereby reducing the modulation spectrum under low power output conditions and achieving the effect of optimizing the modulation spectrum under low power output conditions.

[0058] When the ramp voltage Vramp is greater than the reference voltage VREF: the first switch control signal det is high, controlling both the second single-pole single-throw switch S2 and the third single-pole single-throw switch S3 to conduct, thus opening the first and second feedback branches and connecting the feedback signal IFB and the bandgap reference voltage VBG; the second switch control signal detN is low, controlling the first single-pole single-throw switch S1 to turn off, meaning the signal passes through the first resistor R1. At this time, the voltage output at the output terminal VOUT of the modulation spectrum circuit 100 is jointly determined by the feedback signal IFB formed by the output current of the final stage amplifier 40, the bandgap reference voltage VBG, the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4, that is, the voltage output at the output terminal VOUT of the modulation spectrum circuit 100 is Vramp + (Vramp / R3 - IFB - (VBG - Vramp) / R4) (R1+R2), where R1 is the resistance value of the first resistor R1 and R4 is the resistance value of the fourth resistor R4; by reasonably designing the values ​​of the feedback signal IFB, the bandgap reference voltage VBG, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4, the output terminal VOUT of the modulation spectrum circuit 100 can be made exactly equal at the junction where the ramp voltage Vramp equals the reference voltage VREF, so as to generate a smooth output power curve. At the same time, when the ramp voltage Vramp is full, the voltage output by the output terminal VOUT of the modulation spectrum circuit 100 in this embodiment is the same as the voltage output by the output terminal vout of the modulation spectrum circuit in the related art. That is, the output terminal VOUT of the modulation spectrum circuit 100 in this embodiment can output a higher voltage value, so that it can be applied to the power amplifier 200 to enable the power amplifier 200 to obtain higher output power and efficiency.

[0059] Compared with related technologies, the modulation spectrum circuit 100 of the present invention, through the design of the connection of the operational amplifier OPA, field-effect transistor M, first resistor R1, first control circuit 1, second control circuit 2, second resistor R2, third control circuit 3, third resistor R3, and comparator circuit 4, and the limitation of the output terminal of comparator circuit 4 to output control signals to the first control circuit 1, second control circuit 2, and third control circuit 3 respectively according to the ramp voltage Vramp, so as to control the conduction or cutoff of the first control circuit 1, second control circuit 2, and third control circuit 3. In this way, under high power conditions, the first control circuit 1 can be turned off while the second control circuit 2 and the third control circuit 3 are both turned on to meet the modulation spectrum under high power output conditions. When applied to the power amplifier 200, it can improve the output power and efficiency of the power amplifier 200. Under low power output conditions, the first control circuit 1 can be turned on while the second control circuit 2 and the third control circuit 3 are both turned off to cut off the noise generated by the feedback branches of the second control circuit 2 and the third control circuit 3, thereby optimizing the modulation spectrum under low power output conditions.

[0060] Example 2

[0061] This embodiment provides a power amplifier 200, such as Figure 2 As shown, it includes the modulation spectrum circuit 100 in Embodiment 1 and a primary amplifier 10, a second-stage amplifier 20, a third-stage amplifier 30, a final-stage amplifier 40 and a matching circuit 50 connected in sequence; the input terminal of the primary amplifier 10 is used to receive the radio frequency signal RFIN, and the output terminal of the matching circuit 50 is used to connect to the antenna.

[0062] Of course, the modulation spectrum circuit 100 in Embodiment 1 can not only be applied to the power amplifier 200 including a four-stage amplifier in this embodiment, but also to a power amplifier module including a two-stage amplifier, a three-stage amplifier, or a five-stage amplifier.

[0063] Since the power amplifier 200 in this embodiment uses the modulation spectrum circuit 100 in embodiment one, it can also achieve the same technical effect as the modulation spectrum circuit 100 in embodiment one, which will not be described in detail here.

[0064] It should be noted that the various embodiments described above with reference to the accompanying drawings are merely illustrative of the present invention and not intended to limit its scope. Those skilled in the art should understand that any modifications or equivalent substitutions made to the present invention without departing from its spirit and scope should be included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include those in the plural, and vice versa. Additionally, unless specifically stated otherwise, all or part of any embodiment may be used in conjunction with all or part of any other embodiment.

Claims

1. A modulation spectrum circuit, applied to a power amplifier, characterized in that, The modulation spectrum circuit includes an operational amplifier, a field-effect transistor, a first resistor, a first control circuit, a second control circuit, a second resistor, a third control circuit, a third resistor, and a comparator circuit. The non-inverting input of the operational amplifier is used to connect to the ramp voltage; The gate of the field-effect transistor is connected to the output terminal of the operational amplifier, and the source of the field-effect transistor is used to connect to the operating voltage. The drain of the field-effect transistor serves as the output terminal of the modulation spectrum circuit, used to output a modulation signal with a preset modulation spectrum to the final stage amplifier in the power amplifier. The first terminal of the first resistor is connected to the drain of the field-effect transistor; The first terminal of the first control circuit is connected to the second terminal of the first resistor, and the second terminal of the first control circuit is connected to the first terminal of the first resistor. The input terminal of the second control circuit is used to receive the feedback signal formed by the output current of the final stage amplifier in the power amplifier, and the output terminal of the second control circuit is connected to the second terminal of the first resistor; The first end of the second resistor is connected to the inverting input of the operational amplifier and the output of the second control circuit, respectively. The input terminal of the third control circuit is used to connect to the bandgap reference voltage, and the output terminal of the third control circuit is connected to the second terminal of the second resistor. The first end of the third resistor is connected to the first end of the second resistor, and the second end of the third resistor is grounded; The input terminal of the comparator circuit is used to receive the ramp voltage, and the output terminal of the comparator circuit is used to output control signals to the first control circuit, the second control circuit and the third control circuit respectively according to the ramp voltage, so as to control the first control circuit, the second control circuit and the third control circuit to be turned on or off.

2. The modulation spectrum circuit as described in claim 1, characterized in that, The first control circuit includes a first single-pole single-throw switch; the common terminal of the first single-pole single-throw switch serves as the second terminal of the first control circuit, and the normally open terminal of the first single-pole single-throw switch serves as the first terminal of the first control circuit.

3. The modulation spectrum circuit as described in claim 2, characterized in that, The second control circuit includes a second single-pole single-throw switch; the common terminal of the second single-pole single-throw switch serves as the output terminal of the second control circuit, and the normally open terminal of the second single-pole single-throw switch serves as the input terminal of the second control circuit.

4. The modulation spectrum circuit as described in claim 3, characterized in that, The third control circuit includes a third single-pole single-throw switch; the common terminal of the third single-pole single-throw switch serves as the output terminal of the third control circuit, and the normally open terminal of the third single-pole single-throw switch serves as the input terminal of the third control circuit.

5. The modulation spectrum circuit as described in claim 4, characterized in that, The comparison circuit includes a comparator and an inverter; The non-inverting input of the comparator serves as the input of the comparator circuit, and the inverting input of the comparator is used to connect to the reference voltage. The output of the comparator serves as the first output of the comparator circuit, and is used to output a first switch control signal to the common terminal of the second single-pole single-throw switch and the common terminal of the third single-pole single-throw switch, respectively, to control the second single-pole single-throw switch and the third single-pole single-throw switch to be turned on or off. The input terminal of the inverter is connected to the output terminal of the comparator. The output terminal of the inverter serves as the second output terminal of the comparator circuit, and is used to output a second switch control signal to the common terminal of the first single-pole single-throw switch to control the first single-pole single-throw switch to be turned on or off.

6. The modulation spectrum circuit as described in claim 1, characterized in that, The modulation spectrum circuit further includes a fourth resistor; the fourth resistor is connected in series between the second end of the first resistor and the output end of the second control circuit.

7. A power amplifier, characterized in that, The power amplifier includes a modulation spectrum circuit as described in any one of claims 1 to 6, and a primary amplifier, a second-stage amplifier, a third-stage amplifier, a final-stage amplifier, and a matching circuit connected in sequence; the input terminal of the primary amplifier is used to receive radio frequency signals, and the output terminal of the matching circuit is used to connect to an antenna.

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