| The linearization technology of power amplifier(PA)is the key to balance the efficiency and linearity of amplifier.With the development of mobile communication,people are more and more eager to high-speed transmission,large bandwidth,low latency communication services.The operating band of communication system is subsequently increased,the bandwidth is getting wider,and the modulation method is getting more and more complicated,which also leads to the increasing peak-to-average ratio of the signal and puts forward higher requirements on the linearity of the amplifier.In this paper,based on the analog pre-distortion technology,the research on multidegree-of-freedom analog pre-distortion device is carried out for the linearization requirements of power amplifier such as broa d Band,amplitude-phase independent adjustment and high-precision compensation.The majors and innovative points of this paper are shown below:1.To solve the problem of narrow bandwidth of traditional linearization technique,a reflective analog predistorter design method based on load impedance matching network is proposed.The wideband analog predistorter is realized by fitting the frequency characteristics of the network impedance to the calculated target curve through the rational design of the load impedance matching network.Using this method,a reflective wideband predistorter operating at9.4 GHz ～ 11.4 GHz(19.2% relative bandwidth)is designed.The predistorter has good in-band consistency with gain compensation in the range of 3.9 d B to 4.4 d B and phase compensation in the range of-32.3° to-41.5° in the operating frequency band.Both the measured and simulated results show the effectiveness of the proposed method.2.In order to reduce the correlation of amplitude and phase characteristics of adjustable predistorter,a design method of adjustable analog predistorter with independently adjustable amplitude/phase is proposed to realize the accurate compensation of nonlinear characteristics of amplifier.Two reflective analog predistorters with independently tunable gain characteristics and independently tunable phase characteristics were designed and processed.The test results show that the two predistorters have an independent tuning range of 3.9 d B and 28.6° for amplitude and phase compensation at the center frequency of 30.5 GHz,respectively,which greatly extends the application scenario of the predistorter.Compared with the vector synthesis type amplitude and phase independent tuning circuit,this circuit has the advantages of low circuit complexity and large independent tuning range.3.To achieve high-precision compensation for amplifiers,an analog predistortion technique with multi-degree-of-freedom adjustable amplitude phase compensation amount and curve shape based on a hybrid impedance matching network is proposed.The hybrid impedance matching network consists of Schottky diodes(nonlinear devices),varactor diodes,and microstrip structures.A reflective predistorter with adjustable inflection depth and compensation amount operating in C-band(4.75 GHz～4.85 GHz)is designed for the problem of linearizing a double-inflection point solid-state amplifier with a bumpy gain curve characteristic.At 4.8 GHz,the measured results show that the amplitude and phase compensation of the proposed linearizer can be adjusted by increasing the bias voltage of the varactor diode,and the gain expansion is increased from 2.4 d B to 6.7 d B,and the phase compression is increased from 14.2° to 46.7°.And the inflection depth of the linearizer is positively correlated with the compensation amount,i.e.,the compensation amount increases the inflection depth as well.Adjusting the bias voltage of the Schottky diode in the network can realize the shape adjustment of the pre-distortion curve,and the maximum adjustment range of the inflection point depth is 0～4.1 d B,while the gain and phase compensation amount is basically unchanged,which greatly improves the compensation accuracy of the linearizer. |
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