Analog predistortion is an efficient method for improving the linearity of power amplifiers. This paper presents a simple and tunable analog predistortion linearizer with low insertion loss, capable of reducing the non-linearity effects of microwave power amplifiers. The linearizer employs Schottky diodes as a distortion generator and does not require any additional matching circuit. By controlling the DC bias of the diodes, various combinations of characteristics can be obtained; therefore, this structure can be used to match different device behaviors. Experimental validation using a εr = 3.38, 20-mil thick Rogers substrate at the center frequency of 2 GHz shows that the fabricated linearizer can provide up to 7.5 dB gain expansion. The fractional bandwidth and insertion loss of the linearizer are 10% and 1.7 dB, respectively. The simulated and measured results are in good agreement with each other. To illustrate an approach for compensating the limited phase characteristics of the presented structure, the design and simulation of a dual-branch linearizer utilizing the reflective Schottky diode predistortion linearizer as a nonlinear unit are also presented.
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