CN-121984452-A - Novel reflection-type analog predistortion circuit

CN121984452ACN 121984452 ACN121984452 ACN 121984452ACN-121984452-A

Abstract

The invention relates to a novel reflection type analog predistortion circuit which comprises a 90-degree bridge, a Wilkinson equal power divider, two multiplication reflection branches, a fixed reflection branch and a 90-degree bridge, wherein the 90-degree bridge is used for generating a first path of signal and a second path of signal with a phase difference of 90 degrees, the Wilkinson equal power divider is used for dividing the first path of signal into two paths of equal division signals, the two multiplication reflection branches are used for generating two paths of nonlinear reflection signals, the Wilkinson equal power divider is also used for synthesizing the two paths of nonlinear reflection signals into a first reflection signal, the fixed reflection branch is used for reflecting the second path of signal to obtain a second reflection signal, and the 90-degree bridge is also used for vector synthesizing the first reflection signal and the second reflection signal to output a predistortion signal. The invention can be effectively complemented with the nonlinear characteristic of the solid-state power amplifier, thereby improving the linearity of the solid-state power amplifier.

Inventors

LIU XIN
MA XIAOHUA
ZHANG CHENGLONG
LU YANG
YI CHUPENG
ZHAO ZIYUE
FENG TING

Assignees

西安电子科技大学

Dates

Publication Date: 20260505
Application Date: 20251226

Claims (10)

1. A novel reflective analog predistortion circuit comprising: The 90-degree bridge is used for receiving a radio frequency input signal and converting the radio frequency input signal into a first path of signal with a phase difference of 0 degrees and a second path of signal with a phase difference of-90 degrees; the wilkinson equal division power divider is connected with the 90-degree electric bridge and is used for equally dividing the first path of signals into two paths of identical equal division signals; The first multiplication reflection branch and the second multiplication reflection branch with the same structure are connected with the wilkinson aliquoting power divider and are respectively used for receiving two paths of aliquoting signals, nonlinear processing is carried out on the aliquoting signals to obtain nonlinear reflection signals, and the nonlinear reflection signals respectively generate the same first reflection coefficient and second reflection coefficient; The wilkinson equal power divider is further configured to receive two paths of the nonlinear reflection signals, and synthesize the two paths of the nonlinear reflection signals into a first reflection signal, so that the first reflection coefficient and the second reflection coefficient are synthesized into multiplied equivalent reflection coefficients; The fixed reflection branch is connected with the 90-degree bridge and is used for receiving a second path of signals, reflecting the second path of signals to obtain second reflection signals and generating a fixed reflection coefficient; the 90-degree bridge is further configured to receive the two paths of the first reflection signal and the second reflection signal, and perform vector synthesis on the equivalent reflection coefficient and the fixed reflection coefficient to obtain a transmission coefficient, and finally output a predistortion signal.
2. The novel reflective analog predistortion circuit of claim 1 wherein said 90 ° bridge comprises microstrip line TL 1 , microstrip line TL 2 , microstrip line TL 3 , microstrip line TL 4 , microstrip line TL 5 , microstrip line TL 6 , microstrip line TL 7 and microstrip line TL 8 , wherein: The first end of the microstrip line TL 1 is connected to the input port IN, the second end of the microstrip line TL 1 is connected to the first end of the microstrip line TL 3 and the first end of the microstrip line TL 4 , the second end of the microstrip line TL 3 is connected to the first end of the microstrip line TL 2 and the first end of the microstrip line TL 5 , the second end of the microstrip line TL 2 is connected to the output port ISO, the second end of the microstrip line TL 4 is connected to the first end of the microstrip line TL 6 and the first end of the microstrip line TL 7 , the second end of the microstrip line TL 5 is connected to the second end of the microstrip line TL 6 and the first end of the microstrip line TL 8 , the second end of the microstrip line TL 7 is connected to the through port, and the second end of the microstrip line TL 8 is connected to the coupling port.
3. The novel reflective analog predistortion circuit of claim 2 wherein said wilkinson divider comprises microstrip TL 9 , microstrip TL 10 , microstrip TL 11 , microstrip TL 12 , microstrip TL 13 , and resistor R 1 , wherein: The first end of the microstrip line TL 9 is connected to the second end of the microstrip line TL 7 , the second end of the microstrip line TL 9 is connected to the first end of the microstrip line TL 10 and the first end of the microstrip line TL 11 , the second end of the microstrip line TL 10 is connected to the first end of the resistor R 1 and the first end of the microstrip line TL 12 , the second end of the microstrip line TL 11 is connected to the second end of the resistor R 1 and the first end of the microstrip line TL 13 , the second end of the microstrip line TL 12 is connected to the first multiplication reflection branch, and the second end of the microstrip line TL 13 is connected to the second multiplication reflection branch.
4. The novel reflective analog predistortion circuit of claim 3 wherein said first multiplying reflection leg comprises a capacitor C 1 , a resistor R 2 , a resistor R 3 , a microstrip line TL 14 and a schottky diode D 1 , wherein: The first end of the capacitor C 1 is connected to the second end of the microstrip line TL 12 , the second end of the capacitor C 1 is connected to the first end of the resistor R 2 and the anode of the schottky diode D 1 , the second end of the resistor R 2 is connected to the power supply V 1 , the cathode of the schottky diode D 1 is connected to the first end of the resistor R 3 and the first end of the microstrip line TL 14 , the second end of the resistor R 3 is grounded, and the rf grounding is completed through the microstrip line TL 14 .
5. The novel reflective analog predistortion circuit of claim 3 wherein said second multiplying reflection leg comprises a capacitor C 2 , a resistor R 4 , a resistor R 5 , a microstrip line TL 15 and a schottky diode D 2 , wherein: The first end of the capacitor C 2 is connected to the second end of the microstrip line TL 13 , the second end of the capacitor C 2 is connected to the first end of the resistor R 4 and the anode of the schottky diode D 2 , the second end of the resistor R 4 is connected to the power supply V 2 , the cathode of the schottky diode D 2 is connected to the first end of the resistor R 5 and the first end of the microstrip line TL 15 , the second end of the resistor R 5 is grounded, and the rf grounding is completed through the microstrip line TL 15 .
6. The novel reflective analog predistortion circuit of claim 2 wherein said fixed reflection branch comprises an open microstrip line TL 16 , a first end of said open microstrip line TL 16 being connected to a second end of said microstrip line TL 8 .
7. The novel reflective analog predistortion circuit of claim 1 wherein said first and second reflection coefficients are expressed as: Wherein, the For the first reflection coefficient to be the same, For the second reflection coefficient, Is the port conductance of the 90 deg. bridge, Is the equivalent conductance of the schottky diode, Is the equivalent capacitance of the schottky diode, In order to be a frequency of the light, Is the imaginary unit of complex number.
8. The novel reflective analog predistortion circuit of claim 7 wherein said equivalent reflection coefficient is expressed as: Wherein, the Is the equivalent reflection coefficient.
9. The novel reflective analog predistortion circuit of claim 8 wherein said fixed reflection coefficient is expressed as: Wherein, the For a fixed reflection coefficient, θ=2pi l/λ, l is the physical length of the fixed reflection leg, which has an electrical length of λ/4.
10. The novel reflective analog predistortion circuit of claim 9 wherein said transmission coefficients are expressed as: Wherein, the Is the transmission coefficient.

Description

Novel reflection-type analog predistortion circuit Technical Field The invention relates to the technical field of wireless communication, in particular to a novel reflection type analog predistortion circuit. Background With the urgent need for modern wireless communication systems to evolve in the fifth generation (5G) and in the future, there is an increasing demand for data transmission rates, system capacity, and spectral efficiency. In order to carry more information within limited spectrum resources, communication systems commonly employ higher order modulation techniques such as orthogonal frequency division multiplexing (OFIDM), 64-QAM, 256-QAM, or even 1024-QAM. The signals produced by these modulation techniques have high peak-to-average power ratio (PAPR) and non-constant envelope characteristics, which place extremely stringent demands on the linearity of the system radio frequency front-end, and in particular the Power Amplifier (PA). The performance of the power amplifier as the last stage of the radio frequency transmission link directly determines the communication quality, power consumption and out-of-band radiation level of the whole system. However, the inherent non-linear characteristics of power amplifiers are a core challenge. When a high peak-to-average ratio, broadband signal passes through a power amplifier, two main nonlinear distortions are induced, namely harmonic distortion, and more critical third-order intermodulation distortion (IMD 3) and fifth-order intermodulation distortion (IMD 5). The distortion products can have two serious consequences, namely, one is that in-band distortion can pollute an original signal, so that constellation diagram distortion and Bit Error Rate (BER) are increased, and communication quality is seriously deteriorated, and the other is that out-of-band distortion energy can be expanded to adjacent channels to generate spectrum regeneration, so that Adjacent Channel Leakage Ratio (ACLR) indexes are deteriorated, normal communication of other frequency bands is interfered, and the spectrum specification of international standards organizations such as 3GPP and the like are violated. To overcome the non-linearity problem of the power amplifier, various linearization techniques have been proposed in the industry. Among them, digital Predistortion (DPD) technology is dominant in scenes where the macro base station and the like have extremely high requirements on performance due to its high accuracy and flexibility. The DPD technique performs inverse nonlinear preprocessing on the input signal in the digital baseband domain to compensate for the nonlinearity of the power amplifier. However, DPD technology also has its inherent limitations in that firstly, it requires a high-speed, high-precision digital-to-analog converter (DAC/ADC) and a powerful Digital Signal Processor (DSP), resulting in high system complexity, high cost and huge power consumption, secondly, as the 5G band is extended to the millimeter wave band, the signal bandwidth may exceed 1GHz, which constitutes a nearly limiting challenge for the sampling rate and processing capacity of the DPD system, and finally, convergence speed and adaptability of the DPD algorithm still present stability risks in the face of rapid changing signal environment and power amplifier temperature drift. Under the background, the Analog Predistortion (APD) technology has the unique advantages of simple structure, low cost, extremely low power consumption, high response speed (no delay) and the like, and has regained wide attention and research value in application scenes of low and medium power and extremely sensitive to cost and power consumption, such as small base stations, millimeter wave integration front ends, large-scale MIMO units, vehicle-mounted radars, consumer electronic equipment and the like. The APD circuit directly works in the radio frequency analog domain, a complex digital processing unit is not needed, and distortion components opposite to the nonlinear characteristics of the power amplifier can be generated in real time, so that the signal is compensated before entering the power amplifier. Among the various types of analog predistortion techniques, the reflective analog predistortion architecture presents great potential due to its unique mechanism. Compared with a traditional transmission line type APD (such as an attenuation network based on a diode or an FET), the reflective type APD core utilizes a nonlinear device (such as a Schottky diode, a varactor diode or a nonlinear capacitance of a transistor) to generate a reflective nonlinear signal when being excited by an input signal, and then the reflective signal is subjected to vector superposition with an original signal on a main path through a directional coupler, so that predistortion is realized. The structure can independently regulate amplitude and phase distortion in a more flexible way theoretically, and realizes more accurate n