Circuit system to improve dynamic EVM

Abstract

The present invention discloses a circuit system for improving dynamic EVM, which mainly includes a radio frequency channel and a main control chip, wherein the radio frequency channel also includes a power detection unit, the power detection unit includes a first transistor, a low-power detection subunit and a high-power detection subunit, the low-power detection subunit performs low-power detection on the input signal to form a first linear region, the high-power detection subunit performs high-power detection on the input signal to form a second linear region, the base of the first transistor is respectively connected to the output end of the low-power detection subunit and the output end of the high-power detection subunit to superimpose the outputs of the low-power detection subunit and the high-power detection subunit to form a continuous linear region; the emitter of the first transistor is connected to the main control chip, and the collector is connected to the power supply. The circuit system for improving dynamic EVM of the present invention realizes a dynamic compensation bias circuit and improves the DEVM performance.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency and microwave, and more particularly to a circuit system for improving dynamic EVM. Background Art

[0002] In the design process of WiFi RF front-end chips, the dynamic error vector value (DEVM) often fails to meet the index requirements. In order to improve the DEVM performance of WiFi RF front-end chips, it is often necessary to dynamically adjust the static bias current of the power amplifier in real time. The current mainstream design solution is to use an active bias circuit and build a temperature detection tube into the power amplifier to dynamically adjust the static current according to the temperature. However, this method is increasingly difficult to meet the requirements as WiFi is updated, and the design difficulty is further increased.

[0003] At present, most of the design schemes of WiFi RF front-end chips adopt active bias circuits, and place temperature detection tubes near the high temperature of power tubes for temperature compensation, thereby obtaining relatively good DEVM characteristics. For example, in the article "The Impact of Electro-thermal Coupling On HBT Power Amplifiers" published by Keysight application engineer Matthew Ozalas in 2014, he used the following method: Figure 1 The active bias circuit shown in the figure and Qmir as a temperature detection tube placed in the middle of the HBT can achieve good dynamic EVM performance. However, with the gradual evolution of WiFi standards, the requirements for EVM are becoming more and more stringent. Figure 1 It becomes increasingly difficult to improve the dynamic EVM characteristics by using the active bias circuit shown or other similar circuits to improve the thermal memory effect.

[0004] In addition, skyworks patent US10158333B2, such as Figure 2 As shown, the patent mainly uses a D trigger to select different current sources to dynamically adjust the static current of each level of HBT power tube. For example, in the third level, based on the IRFE current source, an ISMOOTH current source and an ISMOOTH amplitude control current source independent of the variable VCC are added to improve the dynamic EVM index by adjusting the ISMOOTH value. The solution of this patent is relatively complex to design the ISMOOTH current source and the variable ISMOOTH amplitude control current source independent of VCC, and the design difficulty is also relatively large.

[0005] Generally speaking, for WiFi RF front-end chips, the dynamic EVM index is a key indicator that directly affects the performance of the product. With the gradual evolution of WiFi standards, the requirements for dynamic EVM indicators have become more and more stringent. For example, in 11ac (WiFi5 standard), the dynamic EVM index is required to reach -35dB, and in 11ax (WiFi6 standard), due to the use of 1024QAM modulation and some other related technologies, the dynamic EVM of WiFi RF front-end chips has become -43dB or even -47dB. For those using similar Figure 1 As for the active bias circuit shown in the figure, the design difficulty gradually increases, which invisibly increases the product development cycle. Figure 2 For the circuit structure shown, although the dynamic EVM can be improved, since multiple current sources are designed and the trigger is required to adjust these current sources in real time to improve the dynamic EVM, the system has high requirements on the trigger and current source, which has a certain design difficulty.

[0006] Therefore, it is necessary to provide an improved circuit system for improving dynamic EVM performance to overcome the above-mentioned defects. Summary of the invention

[0007] The purpose of the present invention is to provide a circuit system for improving dynamic EVM, which jointly adjusts the variable voltage unit on the controller according to three variables: the intrinsic temperature of the chip environment, the internal relative temperature of the power unit, and the voltage output by the power detection unit, thereby realizing a dynamic compensation bias circuit and improving the DEVM performance.

[0008] To achieve the above-mentioned purpose, the present invention provides a circuit system for improving dynamic EVM, which is mainly used in front-end chips of WiFi radio frequency to improve the dynamic EVM of front-end chips of WiFi radio frequency. It mainly includes a radio frequency channel and a main control chip. The main control chip is used to collect and obtain the temperature and power information of the radio frequency channel, and dynamically adjust the static bias current of the radio frequency channel according to the obtained information; wherein the radio frequency channel includes a three-stage amplifier, and the input end of each stage of the amplifier is provided with a bias unit, and each of the bias units is connected to the main control chip, and the main control chip controls the bias unit to provide a bias current for the corresponding amplifier; wherein the radio frequency channel also includes a power detection unit, and the power detection unit detects the power of the output signal of the third-stage amplifier, and inputs the detection result into the main control chip. The chip is used for the main control chip to adjust the static bias current of the radio frequency channel; the power detection unit includes a first transistor, a low-power detection subunit and a high-power detection subunit, the low-power detection subunit and the high-power detection subunit respectively receive the signal output by the third-stage amplifier, the low-power detection subunit performs low-power detection on the input signal to form a first linear region, and the high-power detection subunit performs high-power detection on the input signal to form a second linear region, the base of the first transistor is respectively connected to the output end of the low-power detection subunit and the output end of the high-power detection subunit to superimpose the outputs of the low-power detection subunit and the high-power detection subunit to form a continuous linear region; the emitter of the first transistor is connected to the main control chip, and the collector thereof is connected to the power supply.

[0009] Preferably, the low-power detection subunit includes a second transistor, a coupling circuit and a bias circuit. The coupling circuit couples the low-power part of the output signal of the third-stage amplifier to the low-power detection subunit, and inputs the coupled signal into the second transistor. The second transistor rectifies the input signal to form a voltage signal and outputs it to the first transistor. The bias circuit is connected to the base of the second transistor to provide a bias current for the second transistor.

[0010] Preferably, the coupling circuit includes a first capacitor and a second capacitor, one end of the first capacitor is connected to the output end of the third-stage amplifier, the other end of the first capacitor is connected to one end of the second capacitor and the bias circuit, and the other end of the second capacitor is grounded.

[0011] Preferably, the bias circuit includes a first resistor, a second resistor, a third resistor and a third transistor, one end of the first resistor is commonly connected to the other end of the first capacitor, the collector of the third transistor, one end of the second resistor and one end of the third resistor, and the other end of the first resistor is connected to the high-power detection subunit; the other end of the second resistor is connected to the base of the third transistor, the emitter of the third transistor is grounded, and the other end of the third resistor is connected to the base of the second transistor.

[0012] Preferably, the low-power detection subunit further includes a third capacitor, one end of the third capacitor is connected to the base of the second transistor, and the other end of the third capacitor is grounded.

[0013] Preferably, the high-power detection subunit has completely the same structural features as the low-power detection subunit.

[0014] Preferably, the number of the low-power detection subunits is greater than or equal to 1, and the number of the high-power detection subunits is greater than or equal to 1.

[0015] Preferably, the power detection unit further includes a first anti-static electronic circuit and a second anti-static electronic circuit, the first anti-static electronic circuit is connected to the emitter of the first transistor, and the second anti-static electronic circuit is connected to the collector of the first transistor.

[0016] Preferably, the power detection unit also includes a fourth resistor and a fifth resistor, one end of the fourth resistor is connected to the other end of the first resistor, and the other end is connected to the base of the first transistor; one end of the fifth resistor is connected to the emitter of the first transistor, and the other end is connected to the first anti-static electronic circuit.

[0017] Preferably, the power detection unit further includes a fourth capacitor, one end of the fourth capacitor is connected to the collector of the first transistor, and the other end of the fourth capacitor is grounded.

[0018] Compared with the prior art, the circuit system for improving dynamic EVM of the present invention uses a power detection unit to fine-tune the static current according to the power detected in real time, and through the cooperation of the small-power detection subunit and the high-power detection subunit, the corresponding linear region can be obtained under different power conditions, the bias adjustment can be better performed, and the compensation performance of the bias unit can be enhanced, thereby realizing the dynamic EVM performance optimization of the RF front-end chip.

[0019] The present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, which are used to illustrate embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a structural schematic diagram of the active bias circuit of prior art 1.

[0021] Figure 2 It is a structural schematic diagram of a circuit system for improving dynamic EVM according to prior art 2.

[0022] Figure 3 A schematic diagram of the structure of a radio frequency channel of a circuit system for improving dynamic EVM of the present invention.

[0023] Figure 4 A schematic diagram of the structure of a power detection subunit of a radio frequency channel of a circuit system for improving dynamic EVM of the present invention.

[0024] Figure 5 The graph is a test result of the circuit system for improving dynamic EVM according to the present invention.

[0025] Figure 6 The figure is a comparison diagram of the power change curves corresponding to the circuit system for improving dynamic EVM of the present invention and the EVM of the existing active bias solution. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are now described with reference to the accompanying drawings, in which like element numbers represent like elements. As described above, the present invention provides a circuit system for improving dynamic EVM, which adjusts the variable voltage unit on the controller according to three variables: the intrinsic temperature of the chip environment, the internal relative temperature of the power unit, and the voltage output by the power detection unit, thereby realizing a dynamic compensation bias circuit and improving the DEVM performance.

[0027] The circuit system for improving dynamic EVM of the present invention is mainly used in the front-end chip of WiFi radio frequency to improve the dynamic EVM of the front-end chip of WiFi radio frequency. It mainly includes a radio frequency channel and a main control chip. The main control chip is used to collect and obtain the temperature and power information of the radio frequency channel, and dynamically adjust the static bias current of the radio frequency channel according to the obtained information.

[0028] Further, please refer to Figure 3As shown in the figure, the RF channel includes three-stage amplifiers OP1, OP2, and OP3. Each stage of the amplifier amplifies the input RF signal RFin in turn. A bias unit (BC1, BC2, BC3) is provided at the input end of each stage of the amplifier, and each bias unit is connected to the main control chip. The main control chip controls the bias unit to provide a bias current for the corresponding amplifier; for example, the bias unit BC1 provides a bias current for the first-stage amplifier OP1, the bias unit BC2 provides a bias current for the second-stage amplifier OP2, and the bias unit BC3 provides a bias current for the third-stage amplifier OP3; wherein, in a preferred embodiment of the present invention, the RF channel also includes a power detection unit CK, the power detection unit CK detects the power of the output signal of the third-stage amplifier OP3, and inputs the detection result to the main control chip, so that the main control chip can adjust the static bias current of the RF channel (the output current of each bias unit BC1, BC2, BC3) to enhance the compensation performance of the bias unit.

[0029] The main control chip of the present invention is provided with a plurality of temperature detection units, one of which is provided on the chip to detect the ambient temperature, so as to detect the ambient temperature of the chip in real time and adjust the influence of the ambient temperature on the static current; in addition, a temperature detection unit is also provided in the middle or edge of each amplifier (where the temperature is relatively high), that is, to collect the relative temperature of each amplifier, and to enter the main control chip after the collected temperature is compared and amplified in the form of current, so as to dynamically adjust the static current of each level. Specifically, the chip ambient temperature is detected by the temperature detection unit, and a voltage signal corresponding to the ambient temperature information is obtained. After the voltage signal is amplified by the comparator on the main control chip, it is compared with the register data in the main control chip to find the static current configuration under the ambient temperature, and then the configuration is determined to be correct by the current detection unit. The function is mainly to configure the ambient temperature, such as the overall temperature compensation under high and low temperatures; the specific static bias current given by the bias unit of each level is compared and amplified by the temperature detection unit in each level, and the corresponding temperature compensation curve is found in the register, and then the static bias current of each level is dynamically adjusted by adjusting the variable voltage source in the main control chip.

[0030] For details, please refer to Figure 4The power detection unit includes a first transistor Q1, a low-power detection subunit and a high-power detection subunit. The low-power detection subunit and the high-power detection subunit receive the signal output by the third-stage amplifier OP3 respectively. The low-power detection subunit performs low-power detection on the input signal to form a first linear region, and the high-power detection subunit performs high-power detection on the input signal to form a second linear region. The base of the first transistor Q1 is respectively connected to the output end of the low-power detection subunit and the output end of the high-power detection subunit to superimpose the outputs of the low-power detection subunit and the high-power detection subunit to form a continuous linear region. The emitter of the first transistor Q1 is connected to the main control chip, and its collector is connected to the power supply. In the present invention, the first linear region and the second linear region are superimposed by the first transistor Q1 to obtain a detection curve that tends to be ideally linear within the design power range, so that the bias current of the bias circuit is adjusted by detecting the power, thereby enhancing the compensation performance of the bias circuit.

[0031] Furthermore, the low-power detection subunit includes a second transistor Q2, a coupling circuit and a bias circuit. The coupling circuit couples the low-power part of the output signal of the third-stage amplifier OP3 to the low-power detection subunit, and inputs the coupled signal into the second transistor Q2. The second transistor Q2 rectifies the input signal and outputs it to the first transistor Q1. The bias circuit is connected to the base of the second transistor Q2 to provide a bias current for the second transistor Q2. Specifically, the coupling circuit includes a first capacitor C1 and a second capacitor C2, one end of the first capacitor C1 is connected to the output end of the third-stage amplifier OP3, the other end of the first capacitor C1 is connected to one end of the second capacitor C2 and the bias circuit, and the other end of the second capacitor C2 is grounded; the bias circuit includes a first resistor R1, a second resistor R2, a third resistor R3 and a third transistor Q3, one end of the first resistor R1 is connected to the other end of the first capacitor C1, the collector of the third transistor Q3, one end of the second resistor R2 and one end of the third resistor R3, and the other end of the first resistor R1 is connected to the high-power detection subunit; the other end of the second resistor R2 is connected to the base of the third transistor Q3, the emitter of the third transistor Q3 is grounded, and the other end of the third resistor R3 is connected to the base of the second transistor Q2. The low-power detection subunit also includes a third capacitor C3, one end of the third capacitor C3 is connected to the base of the second transistor Q2, and the other end of the third capacitor C3 is grounded to filter the signal input to the second transistor Q2.

[0032] The high-power detection subunit has the same structural features as the low-power detection subunit, and includes a capacitor C11, a capacitor C12, a resistor R11, a resistor R12, a resistor R13, a transistor Q12, a transistor Q13 and a capacitor C13. Figure 4 The only difference is that the high-power detection subunit detects the high-power part of the output signal of the third-stage amplifier OP3 and obtains a second linear region corresponding to the high power, which will not be repeated here.

[0033] In a preferred embodiment of the present invention, in order to make the linear region obtained by the power detection unit more stable and the corresponding relationship with the output power of the third-stage amplifier OP3 more accurate, the low-power detection subunit and the high-power detection subunit can be set to multiple; that is, the number of the low-power detection subunit is greater than or equal to 1, and the number of the high-power detection subunit is greater than or equal to 1; in actual application, the number of the low-power detection subunit and the high-power detection subunit can be flexibly selected based on the required linear region accuracy requirements and cost control. In addition, the combination of the low-power detection subunit and the high-power detection subunit can also be flexibly combined according to specific circumstances, and is not specifically limited in the present invention.

[0034] In addition, in the present invention, in order to ensure the accuracy of the output signal and avoid electrostatic interference of the input power supply Vsup, the power detection unit also includes a first anti-static electronic circuit ESD1 and a second anti-static electronic circuit ESD2. The first anti-static electronic circuit ESD1 is connected to the emitter of the first transistor Q1 to prevent static electricity from affecting the accuracy of the output signal. The second anti-static electronic circuit ESD2 is connected to the collector of the first transistor Q1. Since the first transistor Q1 is also connected to the input power supply Vsup, the second anti-static electronic circuit ESD2 can effectively avoid electrostatic interference of the input power supply Vsup.

[0035] Furthermore, the power detection unit also includes a fourth resistor R4, a fifth resistor R5 and a fourth capacitor C4, one end of the fourth resistor R4 is connected to the other end of the first resistor R1, and the other end is connected to the base of the first transistor Q1, so as to adjust and control the bias current of the first transistor Q1; one end of the fifth resistor R5 is connected to the emitter of the first transistor Q1, and the other end is connected to the first anti-static electronic circuit ESD1, so as to effectively isolate the output signal and ensure the purity of the output signal; one end of the fourth capacitor C4 is connected to the collector of the first transistor Q1, and the other end is grounded, so as to filter out the power supply ripple and bypass the RF signal.

[0036] Please refer to Figure 5The working principle of the power detection unit of the circuit system for improving dynamic EVM of the present invention is described as follows: the output signal RFin3 of the third-stage amplifier OP3 enters the power detection unit. First, in the low-power detection sub-unit, the first capacitor C1 and the second capacitor C2 form a capacitive coupling terminal element, coupling a part of the power (low-power part) into the low-power detection sub-unit, and forming a voltage signal after being rectified by the second transistor Q2 as an emitter follower, and output through the first transistor Q1. The third transistor Q3 plays a role of voltage stabilization, and cooperates with the first resistor R1, the second resistor R2 and the third resistor R3 to provide a suitable bias state for the second transistor Q2. Similarly, in the high-power detection subcircuit, capacitor C11 and capacitor C12 form a capacitor coupling unit, coupling a part of the power (high-power part), forming another voltage signal after being rectified by transistor Q12 as an emitter follower, and output through the first transistor Q1, and transistor Q13 cooperates with resistor R11, resistor R12, and resistor R12 to provide a stable and suitable bias current to transistor Q2; the transistors Q2 and Q12 form a voltage signal after rectification, which is superimposed on the base of the first transistor Q1 as an emitter follower, and undergoes secondary rectification, thereby forming a relatively linear detector. Among them, the two detectors of the low-power detection subunit and the high-power detection subunit can obtain two nearly linear regions (region) by reasonably selecting the coupling capacitance values ​​of capacitor C1, capacitor 11, and reasonably configuring the static points of transistor Q3 and transistor Q13. Figure 5 In the figure, the linear region between 3dBm and 15dBm is formed by the low-power detection subunit, i.e., the first linear region, and the linear region after 15dBm (the second linear region) is mainly realized by the high-power detection subunit). After the first transistor Q1 is superimposed, a detection curve approaching an ideal linearity within the designed power range can be obtained. Thus, the bias current of the bias circuit is adjusted by detecting the power, thereby enhancing the compensation performance of the bias circuit.

[0037] Please refer to Figure 6 A comparison diagram of the power change curves of the circuit system for improving dynamic EVM of the present invention and the EVM of the existing active bias solution is shown. As shown in the figure, before the output power reaches 24dBm, especially before the output power reaches 21dBm, the EVM curve of the solution of the present invention is significantly lower than the EVM curve of the existing active bias solution, thereby greatly improving the EVM power situation.

[0038] The present invention has been described above in conjunction with the best embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A circuit system for improving dynamic EVM, which is applied to the front-end chip of WiFi radio frequency to improve the dynamic EVM of the front-end chip of WiFi radio frequency, and mainly includes a radio frequency channel and a main control chip, wherein the main control chip is used to collect and obtain the temperature and power information of the radio frequency channel, and dynamically adjust the static bias current of the radio frequency channel according to the obtained information; wherein the radio frequency channel includes a three-stage amplifier, each stage of the amplifier is provided with a bias unit at the input end, and each of the bias units is connected to the main control chip, and the main control chip controls the bias unit to provide a bias current for the corresponding amplifier; characterized in that, The RF channel also includes a power detection unit, which detects the power of the output signal of the third-stage amplifier and inputs the detection result to the main control chip so that the main control chip can adjust the static bias current of the RF channel; the power detection unit includes a first transistor, a low-power detection subunit and a high-power detection subunit, the low-power detection subunit and the high-power detection subunit respectively receive the signal output by the third-stage amplifier, the low-power detection subunit performs low-power detection on the input signal to form a first linear region, and the high-power detection subunit performs high-power detection on the input signal to form a second linear region, the base of the first transistor is respectively connected to the output end of the low-power detection subunit and the output end of the high-power detection subunit to superimpose the outputs of the low-power detection subunit and the high-power detection subunit to form a continuous linear region; the emitter of the first transistor is connected to the main control chip, and its collector is connected to the power supply.

2. The circuit system for improving dynamic EVM as claimed in claim 1, characterized in that: The low-power detection subunit includes a second transistor, a coupling circuit and a bias circuit. The coupling circuit couples the low-power part of the output signal of the third-stage amplifier to the low-power detection subunit, and inputs the coupled signal into the second transistor. The second transistor rectifies the input signal to form a voltage signal and outputs it to the first transistor. The bias circuit is connected to the base of the second transistor to provide a bias current for the second transistor.

3. The circuit system for improving dynamic EVM as claimed in claim 2, characterized in that: The coupling circuit includes a first capacitor and a second capacitor, one end of the first capacitor is connected to the output end of the third stage amplifier, the other end of the first capacitor is connected to one end of the second capacitor and the bias circuit, and the other end of the second capacitor is grounded.

4. The circuit system for improving dynamic EVM as claimed in claim 3, characterized in that: The bias circuit includes a first resistor, a second resistor, a third resistor and a third transistor, one end of the first resistor is commonly connected to the other end of the first capacitor, the collector of the third transistor, one end of the second resistor and one end of the third resistor, and the other end of the first resistor is connected to the high-power detection subunit; the other end of the second resistor is connected to the base of the third transistor, the emitter of the third transistor is grounded, and the other end of the third resistor is connected to the base of the second transistor.

5. The circuit system for improving dynamic EVM as claimed in claim 4, characterized in that: The low-power detection subunit further includes a third capacitor, one end of which is connected to the base of the second transistor, and the other end of which is grounded.

6. The circuit system for improving dynamic EVM as claimed in claim 5, characterized in that: The high-power detection subunit has the same structural features as the low-power detection subunit.

7. The circuit system for improving dynamic EVM as claimed in claim 5, characterized in that: The number of the low-power detection subunits is greater than or equal to 1, and the number of the high-power detection subunits is greater than or equal to 1.

8. The circuit system for improving dynamic EVM as claimed in claim 4, characterized in that: It also includes a first anti-static electronic circuit and a second anti-static electronic circuit, wherein the first anti-static electronic circuit is connected to the emitter of the first transistor, and the second anti-static electronic circuit is connected to the collector of the first transistor.

9. The circuit system for improving dynamic EVM as claimed in claim 8, characterized in that: It also includes a fourth resistor and a fifth resistor, one end of the fourth resistor is connected to the other end of the first resistor, and the other end is connected to the base of the first transistor; one end of the fifth resistor is connected to the emitter of the first transistor, and the other end is connected to the first anti-static electronic circuit.

10. The circuit system for improving dynamic EVM as claimed in claim 9, characterized in that: A fourth capacitor is also included, one end of the fourth capacitor is connected to the collector of the first transistor, and the other end of the fourth capacitor is grounded.

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