Doherty amplifier and its distortion characteristic compensation method

Abstract

Pre-distortion compensation circuits (11, 12) are provided at the front stages of a carrier amplifier (13) and a peak amplifier (14), respectively. The pre-distortion compensation circuit (11) has a characteristic to compensate the distortion produced characteristically on the operation of the carrier amplifier (13), particularly the amplitude-phase (AM-PM) distortion. The pre-distortion compensation circuit (12) has a characteristic to compensate the distortion produced characteristically on the operation of the peak amplifier (14), particularly the AM-PM distortion. As a result, the AM-PM display characteristic of the amplifier as a Doherty amplifier can be compensated, a low distortion characteristic is achieved, and ideal power combining operation of the Doherty amplifier is realized.

Description

technical field [0001] The present invention relates to a Doherty amplifier comprising two amplifiers whose operation types are different from each other for realizing high-efficiency amplification. Background technique [0002] Due to the explosive growth of the portable terminal market in recent years and the associated infrastructure improvement, the market has imposed stricter requirements to improve the efficiency of base station transmit amplifiers and mobile station transmit amplifiers. Therefore, attention has been paid in recent years to the trend of realizing high-performance amplifiers by combining techniques for amplifying signals with high efficiency (represented as Doherty amplifiers) with techniques for reducing distortion and, more recently, distortion compensation (for example, see the following references 1- 6). [0003] Reference 1: JP-2002-124840-A [0004] Reference 2: JP-7-22852-A [0005] Reference 3: JP-8-330873-A [0006] Reference 4: Japanese Tr...

AI Technical Summary

Problems solved by technology

[0025] Although high efficiency can be achieved with the conventional Doherty amplifier described above, the problem is that AM-PM distortion increases with increasing input power

Therefore, relying on uniform compensation of predistortion compensation circuits as in the prior art is not always the best solution

Specifically, when considering the Doherty amplifier as a single amplifier and the predistortion compensation for it, it is not always possible to achieve optimal AM-PM compensation in each of the carrier amplifier 13 and peaking amplifier 14, thus cannot provide optimal distortion compensation effect and ideal operation as a Doherty amplifier

In addition, there is a problem that the phase difference is not compensated for the output combining point, so that ideal power combining operation cannot be achieved

[0029] In other words, although a high efficiency can be obtained, since the Doherty amplifier is composed of a carrier amplifier and a peaking amplifier with different operating classes, the above-mentioned conventional Doherty amplifier and related distortion characteristic compensation methods have the disadvantage of being unable to reduce such as AM-PM distortion Distortion problem

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