Broadband Doherty power amplifier based on compensation to parasitic capacitance

Abstract

The invention provides a broadband Doherty power amplifier based on compensation to parasitic capacitance. The power amplifier comprises an equal split Wilkinson power divider, a carrier power amplifier branch, a peak value power amplifier branch and a load modulation network, wherein the carrier power amplifier branch comprises a carrier power amplifier input matching circuit, a carrier power amplifier and a carrier power amplifier output matching circuit sequentially connected in series, and a first microstrip line Z1 is connected with the output end of the carrier power amplifier in parallel; the peak value power amplifier branch comprises a phase delay line, a peak value power amplifier input matching circuit, a peak value power amplifier and a peak value power amplifier output matching circuit, and a second microstrip line Z2 is connected with the output end of the peak value power amplifier in parallel. Compared with the prior art, the broadband Doherty power amplifier has the advantage that a section of shorted microstrip line is added at the output end of each of main and auxiliary branch transistors, so that influence of the parasitic capacitance on saturation efficiency of the amplifier and bandwidth is suppressed, and bandwidth performance and efficiency of the Doherty power amplifier are improved.

Description

technical field [0001] The invention relates to the technical field of radio frequency communication, in particular to a Doherty power amplifier which widens the working bandwidth range and improves the bandwidth performance. Background technique [0002] With the rapid development of wireless communication technology, radio frequency microwave technology is becoming more and more important in people's daily life. In order to transmit as much data as possible within a limited spectrum bandwidth, communication providers usually use very complex modulation methods, which will lead to a larger peak-to-average ratio (PAPR) of the signal. To ensure acceptable linearity, the peak The average ratio limits the power amplifier back-off power level. If a traditional power amplifier is used, the amplifier efficiency is very low, especially in the case of high power back-off. The Doherty power amplifier adopts the load-pull technology, which can improve the efficiency during power bac...

AI Technical Summary

Problems solved by technology

[0003] The current wireless communication system is facing the challenge of a sudden increase in the amount of transmitted information, and the available frequency band resources are worrying, and the way to improve the frequency band utilization is complicated and difficult to implement, so it is imperative to increase the frequency bandwidth of the communication system

[0004] In order to improve the bandwidth range of the Doherty power amplifier, the existing mainstream methods include the following two methods: (1) a quarter-wavelength line is usually used in the load modulation network, and the quarter-wavelength line itself has a narrow bandwidth, making the entire Doherty The bandwidth of the power amplifier is severely limited. Therefore, the existing technology adopts the method of adjusting the quarter-wavelength line in the load modulation network to expand the bandwidth by changing the impedance conversion ratio; in this way, for the main power amplifier, it needs to be The best impedance is matched to the output impedance value required by the user for high and low power input, but the optimal impedance value is not unique, because the quarter-wavelength line can only achieve a certain impedance transformation, and cannot achieve the best for all Impedance is matched, so that impedance modulation in the broadband range cannot be achieved. The same is true for peak amplifiers. There are many solutions to the optimal impedance. It is difficult to achieve broadband requirements only through a quarter-wavelength line. This is the limit of the Doherty power amplifier. (2) In addition, the existing technology can also increase the bandwidth by reducing the limitation of the compensation line of the peak power amplifier to the bandwidth, that is, when designing the peak power amplifier, it is necessary to ensure that it is within the required bandwidth, from The impedance seen by the compensation line port is infinite, so as to ensure that in the low power area, the fallback efficiency of the main power amplifier and the output power of the main power amplifier will not leak to the peak power amplifier. In practice, for the entire frequency band, the output impedance of the peak power amplifier Not all are infinite, only near the center frequency, the impedance is close to infinity, which will lead to power leakage of the main power amplifier and affect the overall performance of the Doherty power amplifier, which is one of the factors limiting the bandwidth of the Doherty power amplifier

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