Doherty envelope tracking power amplifier and method for treating radio frequency signal

[0028] In the Doherty envelope tracking power amplifier and its method for processing radio frequency signals of the present invention, the envelope signal is extracted from the input radio frequency signal through the envelope extraction unit, and the envelope signal is converted into the carrier amplifier working grid after the amplification process of the first linear amplification unit. The carrier amplifier can change according to the envelope of the input radio frequency signal. Under the condition that the output signal gain is basically unchanged, the linearization of the output signal can be optimized in real time, which improves the linearization of the output signal of the carrier amplifier. This improves the efficiency of the Doherty envelope tracking power amplifier.

[0029] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0030] The Doherty envelope tracking power amplifier of the present invention, such as figure 2 , Including power divider, peak amplifier, carrier amplifier, coupler, envelope extraction unit and first linear amplification unit;

[0031] The radio frequency signal input terminal is connected to the input terminal of the power divider and the input terminal of the envelope extraction unit through the coupler, and the output terminal of the power divider is connected to the input terminal and the input terminal of the peak amplifier respectively. The input terminal of the carrier amplifier is connected, the output terminal of the carrier amplifier is coupled to the output terminal of the peak amplifier, and the output terminal of the envelope extraction unit is connected to the gate terminal of the carrier amplifier through a first linear amplifying unit ;

[0032] The coupler divides the radio frequency signal into a first radio frequency signal and a second radio frequency signal. In an embodiment, the first radio frequency signal and the second radio frequency signal may be two radio frequency signals with different powers, wherein the first radio frequency signal Output to the power divider, and the second radio frequency signal is output to the envelope extraction unit; the power divider divides the first radio frequency signal into two radio frequency signals, and one radio frequency signal is amplified by the peak amplifier , The other radio frequency signal is coupled and output with the signal amplified and output by the peak amplifier after being amplified by the carrier amplifier;

[0033] The envelope extraction unit extracts an envelope signal from the second radio frequency signal and outputs it to the first linear amplifying unit, and the first linear amplifying unit amplifies and processes the envelope signal into a grid voltage value for the operation of the carrier amplifier . The amplification factor of the first linear amplifying unit is set according to the grid voltage parameter of the carrier amplifier to ensure that the linearization of the output signal reaches real-time with the envelope change of the input radio frequency signal when the carrier amplifier maintains the same gain. Optimal.

[0034] The first linear amplifying unit adjusts the amplification factor according to the parameter range of the grid voltage value of the carrier amplifier, so that the linearization of the output signal reaches real-time according to the envelope change of the input radio frequency signal under the condition that the carrier amplifier keeps the gain basically unchanged. Optimal. This can improve the linearization of the output signal of the carrier amplifier, thereby improving the output efficiency of the Doherty envelope tracking power amplifier.

[0035] In an embodiment, the Doherty envelope tracking power amplifier of the present invention further includes a second linear amplifying unit, such as image 3 , Connected between the output terminal of the envelope extraction unit and the gate terminal of the peak amplifier; the second linear amplifying unit is used to amplify the envelope signal output by the envelope extraction unit into the The gate voltage value of the peak amplifier. The second linear amplifying unit adjusts the amplification factor according to the parameter range of the gate voltage value of the peak amplifier, so that the output efficiency of the peak amplifier reaches the highest value in real time according to changes in the envelope of the input radio frequency signal, which can improve the output efficiency of the peak amplifier. The output efficiency of the Doherty envelope tracking power amplifier of the present invention is further improved.

[0036] In an embodiment, the Doherty envelope tracking power amplifier of the present invention further includes a first envelope filtering unit and a second envelope filtering unit, such as Figure 4 The first envelope filtering unit is connected between the output terminal of the envelope extraction unit and the input terminal of the first linear amplifying unit; the second envelope filtering unit is connected to the envelope extraction unit Between the output terminal and the input terminal of the second linear amplifying unit. The first envelope filtering unit and the second envelope filtering unit are respectively used to filter out high frequency interference of the signal output by the envelope extraction unit, and can output a relatively pure envelope signal to the first linear amplifying unit and the second Two linear amplification unit.

[0037] In an embodiment, the Doherty envelope tracking power amplifier of the present invention further includes a delay adjustment unit, such as Figure 5 , Connected between the output end of the coupler and the input end of the power divider, and used to delay the input first radio frequency signal and output it to the input end of the power divider to ensure that the input radio frequency signal passes through The time from the coupler, the power divider to the carrier amplifier is the same as the time from the input radio frequency signal through the coupler, the envelope extraction unit, and/or the first envelope filter unit, the first linear amplifying unit to the gate terminal of the carrier amplifier, It can also ensure that the input RF signal passes through the coupler, the power divider to the peak amplifier time and the input RF signal passes through the coupler, the envelope extraction unit, and/or the second envelope filter unit, the second linear amplification unit to the peak The timing of the gate terminal of the amplifier is the same. In this way, the working status of the carrier amplifier and the peak amplifier can be synchronized with the envelope change of the input radio frequency signal, and the carrier amplifier and the peak amplifier can work in a high efficiency state in real time.

[0038] Since the envelope extraction unit has a range of requirements for the power of the input radio frequency signal, the radio frequency signal with too much power will burn the envelope extraction unit. In order to protect the envelope extraction unit, in one embodiment, the Doherty envelope tracking power amplifier of the present invention ,Such as Figure 5 , Further comprising a power attenuation unit, connected between the output end of the coupler and the input end of the envelope extraction unit, for power attenuating the radio frequency signal coupled by the coupler and outputting it to the envelope Extraction unit.

[0039] In one embodiment, the Doherty envelope tracking power amplifier of the present invention, such as Figure 6 , Further comprising a first delay unit and a second delay unit; the first delay unit is connected between the output end of the power divider and the input end of the peak amplifier; one end of the second delay unit is connected to the carrier amplifier The output end is connected, and the other end is coupled to the output end of the peak amplifier;

[0040] The first delay unit is used to delay processing the radio frequency signal output by the power divider and then output to the input end of the peak amplifier; the second delay unit is used to delay the amplified signal of the carrier amplifier Output after processing. In order to ensure that the signal amplified by the carrier amplifier and the signal amplified by the peak amplifier have the same phase when coupled together, the output power of the Doherty power amplifier is further improved.

[0041] In a specific embodiment, the first linear amplifying unit in the Doherty envelope tracking power amplifier of the present invention, such as Figure 7 , Including a first differential amplifier U1, a first capacitor C1, a first resistor R1, and a second resistor R2; the output terminal of the envelope extraction unit is connected to the non-inverting input terminal of the first differential amplifier U1 and the first One end of a capacitor C1 is connected, the other end of the first capacitor C1 is connected to the negative input terminal of the first differential amplifier U1 through a first resistor R1, and the second resistor R2 is connected to the first differential amplifier Between the negative phase input terminal of U1 and the output terminal of the first differential amplifier U1, the first power supply terminal V1 is connected to the negative phase input terminal of the first differential amplifier U1 through the first resistor R1, and the first The output terminal of a differential amplifier U1 is connected to the gate terminal of the carrier amplifier. The amplification factor of the first linear amplification unit can be adjusted by adjusting the voltage value of the first power supply terminal V1 and the values ​​of the first resistor R1 and the second resistor R2.

[0042] In order to protect the first differential amplifier U1 and filter out the DC interference of the envelope signal output by the envelope extraction unit, the first linear amplifying unit further includes a third capacitor C3 and a fifth resistor R5. One end is connected to the output end of the envelope extraction unit, and the other end is connected to the non-inverting input end of the first differential amplifier U1 through the fifth resistor R5.

[0043] In a specific embodiment, the second linear amplifying unit in the Doherty envelope tracking power amplifier of the present invention, such as Figure 8 , Including a second differential amplifier U2, a second capacitor C2, a third resistor R3, and a fourth resistor R4; the output terminal of the envelope extraction unit is also connected to the non-inverting input terminal and the second differential amplifier U2. One end of the second capacitor C2 is connected, the other end of the second capacitor C2 is connected to the negative input end of the second differential amplifier U1 through a third resistor R3, and the fourth resistor R4 is connected to the second Between the negative input terminal of the differential amplifier U2 and the output terminal of the second differential amplifier U2, the second power supply terminal V2 is connected to the negative input terminal of the second differential amplifier U2 through the third resistor R3; The output terminal of the second differential amplifier U2 is connected to the gate terminal of the peak amplifier. The amplification factor of the second linear amplification unit can be adjusted by adjusting the voltage value of the second power supply terminal V2 and the values ​​of the third resistor R3 and the fourth resistor R4.

[0044] In order to protect the second differential amplifier U2 and filter out the DC interference of the envelope signal output by the envelope extraction unit, the second linear amplifying unit further includes a fourth capacitor C4 and a sixth resistor R6; the fourth capacitor C4 One end is also connected to the output end of the envelope extraction unit, and the other end is connected to the non-inverting input end of the second differential amplifier U2 through the sixth resistor R6.

[0045] In a specific embodiment, such as Picture 9 , The first envelope filtering unit in the Doherty envelope tracking power amplifier of the present invention includes a third differential amplifier U3, a fifth capacitor C5, a seventh resistor R7, and an eighth resistor R8; the output terminal of the envelope extraction unit Are respectively connected to the negative phase input end of the third differential amplifier U3 and one end of the fifth capacitor C5, and the other end of the fifth capacitor C5 is connected to the positive phase of the third differential amplifier U3 through a seventh resistor R7. The input terminal is connected, the eighth resistor R8 is connected between the non-inverting input terminal of the third differential amplifier U3 and the output terminal of the third differential amplifier U3, and the third power supply terminal V3 passes through the seventh resistor R7 Is connected to the non-inverting input end of the third differential amplifier U3; the output end of the third differential amplifier U3 is connected to the non-inverting input end of the first differential amplifier U1, or through the third capacitor C3, The five resistor R5 is connected to the non-inverting input terminal of the first differential amplifier U1. The filter bandwidth value of the first envelope filter unit can be adjusted by adjusting the voltage value of the third power supply terminal V3 and the values ​​of the seventh resistor R7, the fifth capacitor C5 and the eighth resistor R8.

[0046] In order to protect the third differential amplifier U3 and filter out the DC interference of the envelope signal output by the envelope extraction unit, the third envelope filtering unit further includes a seventh capacitor C7 and an eleventh resistor R11. The seventh capacitor One end of C7 is connected to the output end of the envelope extraction unit, and the other end is connected to the negative phase input end of the third differential amplifier U3 through the eleventh resistor R11;

[0047] In a specific embodiment, such as Picture 10 The second envelope filter unit in the Doherty envelope tracking power amplifier of the present invention includes a fourth differential amplifier U4, a sixth capacitor C6, a ninth resistor R9, and a tenth resistor R10; the output terminal of the envelope extraction unit It is also connected to the non-inverting input end of the fourth differential amplifier U4 and one end of the sixth capacitor C6, and the other end of the sixth capacitor C6 is connected to the fourth differential amplifier U4 through the ninth resistor R9. The tenth resistor R10 is connected between the negative input end of the fourth differential amplifier U4 and the output end of the fourth differential amplifier U4, and the fourth power supply terminal V4 passes through the first The nine resistor R9 is connected to the negative input terminal of the fourth differential amplifier U4; the output terminal of the fourth differential amplifier U4 is connected to the positive input terminal of the second differential amplifier U2, or through the fourth capacitor C4. The sixth resistor R6 is connected to the non-inverting input terminal of the second differential amplifier U2. The filter bandwidth value of the second envelope filter unit can be adjusted by adjusting the voltage value of the fourth power supply terminal V4 and the values ​​of the ninth resistor R9, the sixth capacitor C6 and the tenth resistor R10.

[0048] In order to protect the fourth differential amplifier U4 and filter out the DC interference of the envelope signal output by the envelope extraction unit, the fourth envelope filtering unit further includes an eighth capacitor C8 and a twelfth resistor R12. The eighth capacitor One end of C8 is connected to the output end of the envelope extraction unit, and the other end is connected to the negative phase input end of the fourth differential amplifier U4 through the twelfth resistor R12.

[0049] The present invention also discloses a method for processing radio frequency signals by a Doherty envelope tracking power amplifier, such as Picture 11 , Including steps:

[0050] S101. Divide the input radio frequency signal into a first radio frequency signal and a second radio frequency signal. In specific implementation, the input radio frequency signal can be divided into two channels of a first radio frequency signal and a second radio frequency signal with different powers, and the power of the first radio frequency signal is slightly greater than the power of the second radio frequency signal.

[0051] S102. Divide the first radio frequency signal into two radio frequency signals, one of which undergoes amplification processing by a peak amplifier, and the other one undergoes amplification processing by a carrier amplifier and is coupled to output signals amplified by the peak amplifier. In specific implementation, the first radio frequency signal can be divided into two radio frequency signals with equal power and consistent phase.

[0052] S103. Extract an envelope signal from the second radio frequency signal, and amplify and process the envelope signal into a grid voltage value at which the carrier amplifier operates according to a grid voltage value parameter of the carrier amplifier. The magnification of the envelope signal is set according to the grid voltage parameter of the carrier amplifier to ensure that the linearization of the output signal reaches the real-time optimum with the envelope change of the input RF signal when the carrier amplifier maintains the same gain. . This can improve the linearization of the output signal of the carrier amplifier, thereby improving the output efficiency of the Doherty envelope tracking power amplifier.

[0053] In one embodiment, after extracting the envelope signal from the second radio frequency signal, the method further includes the step of: amplifying and processing the envelope signal into the gate voltage of the peak amplifier according to the gate voltage value parameter of the peak amplifier value. The amplification processing factor of the envelope signal is adjusted according to the parameter range of the gate voltage value of the peak amplifier, so that the output efficiency of the peak amplifier reaches the highest value in real time according to the envelope change of the input radio frequency signal, which can increase the output of the peak amplifier The efficiency further improves the output efficiency of the Doherty envelope tracking power amplifier of the present invention.

[0054] In an embodiment, after extracting the envelope signal from the second radio frequency signal, before amplifying and processing the envelope signal into the grid voltage value of the carrier amplifier according to the grid voltage value parameter of the carrier amplifier, the method further includes Step: performing envelope filtering processing on the envelope signal;

[0055]After extracting the envelope signal from the second radio frequency signal, before amplifying and processing the envelope signal into the gate voltage value of the peak amplifier according to the gate voltage value parameter of the peak amplifier, the method further includes the step of: The envelope signal is subjected to envelope filtering processing. In this way, envelope filtering is performed after the envelope signal is extracted, which can filter out the high-frequency interference of the envelope signal, and can output a relatively pure envelope signal.

[0056] In an embodiment, before dividing the first radio frequency signal into two radio frequency signals, the method further includes the step of: performing a delay adjustment process on the first radio frequency signal. In order to ensure that the first radio frequency signal is divided into two channels of radio frequency signals to be output to the peak amplifier and the carrier amplifier respectively, and the envelope signal is extracted from the second radio frequency signal and amplified into the carrier amplifier and the peak amplifier. Consistent, this can ensure that the working status of the carrier amplifier and the peak amplifier change in real time with the envelope change of the radio frequency signal, which further improves the output efficiency of the Doherty envelope tracking power amplifier of the present invention.

[0057] Before extracting the envelope signal from the second radio frequency signal, the method further includes the step of performing power attenuation processing on the second radio frequency signal. This can prevent the high-power signal from affecting the envelope extraction process to improve the accuracy of the envelope signal.

[0058] In an embodiment, before the peak amplifier performs amplifying processing on one of the RF signals, the method further includes the step of: performing time delay processing on the RF signal;

[0059] After the carrier amplifier performs amplifying processing on another radio frequency signal, the method further includes the step of: performing time delay processing on the signal amplified by the carrier amplifier and then coupling and outputting the signal output by the peak amplifier. In order to ensure that the signal amplified by the carrier amplifier and the signal amplified by the peak amplifier have the same phase when coupled together, the output power of the Doherty power amplifier is further improved.

[0060] In combination with the above working principle, the specific implementation and working steps of the Doherty envelope tracking power amplifier of the present invention are as follows:

[0061] Step 1: After the input RF signal is received by the antenna, it enters the input end of the Doherty power amplifier with envelope tracking feature. These signals can be WCDMA, CDMA, TD-SCDMA, WiMax, GSM and other existing standard RF signals of different frequency bands ;

[0062] Step 2: After passing through the coupler, the radio frequency signal in step 1 can become two radio frequency signals with unequal power. The signal with higher power enters the delay adjustment unit at the next stage, and the signal with lower power is coupled by The device enters the next-level power attenuation unit. In specific implementation, the coupler can be implemented by a common 3dB power splitter, or by a microstrip line coupling method;

[0063] Step 3: The radio frequency signal entering the time delay adjustment unit in step 2 becomes a signal with a relatively time lag after the time delay adjustment processing. In specific implementation, the delay adjustment unit can adopt a dedicated delay device or delay line design, such as the delay line series of Anaren;

[0064] Step 4: The radio frequency signal after the time delay in step 3 is divided into two radio frequency signals with equal power and the same phase through a power divider. In specific implementation, the power divider adopts a microstrip line design;

[0065] Step 5: One of the two RF signals with equal power in Step 4 becomes a delayed RF signal after being delayed by the first delay unit. In specific implementation, the first delay unit is designed with a microstrip line;

[0066] Step 6: The delayed radio frequency signal in step 5 enters the peak amplifier for amplification, and becomes a power amplified radio frequency signal. In specific implementation, the peak amplifier can use LDMOS, GaN and other power amplifier tube devices;

[0067] Step 7: In step 4, the other one of the two RF signals with the same power is directly entered into the carrier amplifier for amplification, and becomes a power-amplified RF signal. In specific implementation, the carrier amplifier can use LDMOS, GaN and other power amplifier tube devices;

[0068] Step 8: The radio frequency signal amplified by the carrier amplifier in step 7, after being delayed by the second delay unit, and the radio frequency signal amplified by the peak amplifier in step 6, are coupled together at the radio frequency output terminal and output. In specific implementation, the second delay unit adopts a microstrip line design;

[0069] Step 9: The radio frequency signal that enters the power attenuation unit in step 2, after the power attenuation processing, becomes a signal with a suitable power value, which is convenient for the extraction of the subsequent signal envelope. The power value is determined by the subsequent signal envelope extraction unit. It depends on the parameter requirements. In specific implementation, the power attenuation unit adopts a resistance attenuation network design;

[0070] Step 10: The radio frequency signal subjected to the power attenuation processing in step 9 enters the envelope extraction unit, and the low frequency signal reflecting the envelope characteristics of the radio frequency input signal in step 1 is extracted. In specific implementation, the envelope extraction part can be realized by HSMS285X series detector tube, or by other company's envelope detector device;

[0071] Step 11: The low-frequency envelope signal obtained from step 10 is divided into two paths, one enters the second envelope filter unit and the second linear amplification unit for correlation processing, and the other enters the second envelope filter unit and the second linear amplification unit Carry out related processing;

[0072] Step 12: After entering the low-frequency envelope signal of the first envelope filtering unit and the first linear amplifying unit in step 11, the optimized DC offset value and filtering processing bandwidth are adjusted according to the actual working requirements of the subsequent carrier amplifier, and then used as The gate voltage value of the carrier amplifier makes the signal linearization optimal while keeping the output signal gain unchanged;

[0073] In specific implementation, the first envelope filter unit and the first linear amplifying unit are designed with high-speed, large time-bandwidth product differential operational amplifiers, such as AD829 of ADI or OPA357A of TI. The filter bandwidth in the first envelope filter unit is determined by the radio frequency signal format in step 1. The amplification factor of the first linear amplification unit is arbitrarily adjusted by the peak-to-peak value required by the grid voltage of the subsequent stage carrier amplifier.

[0074] Step 13: The low-frequency envelope signal that enters the second envelope filtering unit and the second linear amplifying unit in step 11, after adjusting the optimized DC offset value and filtering processing bandwidth according to the actual working requirements of the subsequent peak amplifier, is used as The gate voltage value of the peak amplifier makes it work in a high efficiency state in real time as the envelope of the radio frequency signal changes.

[0075] In specific implementation, the second envelope filter unit and the second linear amplifying unit are designed with high-speed, large time-bandwidth product differential operational amplifiers, such as AD829 of ADI or OPA357A of TI. The filter bandwidth of the second envelope filter unit is determined by the radio frequency signal format in step 1. The amplification factor of the second linear amplification unit is arbitrarily adjusted by the peak-to-peak value required by the gate voltage value of the subsequent peak amplifier.

[0076] Step 14: Since the grid voltage value of the carrier amplifier and the grid voltage value of the peak amplifier in steps 12 and 13 are both related to the envelope of the RF input signal, when the Doherty power amplifier of the present invention actually works, the frequency of the RF input signal The envelope changes in real time, resulting in the peak amplifier grid voltage value and the carrier amplifier grid voltage value also changing in real time, so that the Doherty power amplifier of the present invention has envelope tracking characteristics, and also further improves the efficiency and linearity index of the Doherty power amplifier .

[0077] Several key points that need to be guaranteed in specific implementation:

[0078] 1. It is necessary to pre-set the relationship between the RF input signal envelope and the carrier amplifier grid voltage value in step 12, including the peak-to-peak grid voltage value and the DC bias value at the power point of special requirements. The principle of determining this relationship is that at each specific input signal envelope value, the carrier amplifier can achieve the optimal linearization of the output signal while keeping the gain basically unchanged;

[0079] 2. The relationship between the envelope of the RF input signal and the gate voltage of the peak amplifier in step 13 needs to be pre-set, including the peak-to-peak value of the gate voltage and the DC offset value at the power point of special requirements. The principle of determining this relationship is to enable the peak amplifier to achieve the highest efficiency while keeping the gain basically unchanged at each specific input signal envelope value;

[0080] 3. For the two signals after the power divider in step 4, the first delay unit and the second delay unit need to be adjusted according to the actual situation, so that the two signals have the same phase when they are coupled together at the RF output end;

[0081] 4. The delay adjustment unit in step 3 needs to be debugged, so that the radio frequency signal in step 1 passes through the coupler, delay adjustment unit, power divider, the first delay unit to reach the peak amplifier, and passes through the coupler and power attenuation unit , The envelope extraction unit, the second envelope filtering unit and the second linear amplifying unit reach the gate terminal of the peak amplifier basically at the same time, and it is also necessary to ensure that the RF signal in step 1 passes through the coupler, delay adjustment unit, and power divider. The time taken by the amplifier to reach the carrier amplifier is basically the same as the time taken by the coupler, the power attenuation unit, the envelope extraction unit, the first envelope filtering unit and the first linear amplifying unit to reach the gate terminal of the carrier amplifier.

[0082] The present invention provides a brand-new Doherty power amplifier with envelope tracking characteristics, which overcomes the shortcomings of the fixed grid voltage value of the carrier amplifier in the existing Doherty power amplifier, the linearity cannot reach the real-time optimum, and the fixed grid voltage value of the peak amplifier. The shortcomings that the efficiency cannot reach the highest real-time level greatly improves the linearity and efficiency of the Doherty power amplifier, which not only meets the requirements of high linearity in the existing communication network, but at the same time, higher efficiency contributes to the development trend of future communication equipment miniaturization and portability, and Environmental protection and energy saving are of great significance. Therefore, a new Doherty power amplifier with envelope tracking characteristics proposed by the present invention will have a very broad application prospect in communication equipment.

[0083] The embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.