Of amplifier of radio frequency power nonlinear lack fidelity meeting makes its produce new frequency weight, be like to 2 rank lack fidelity meeting produces harmonic and Shuang Yin 2 times to pat frequency, to 3 rank lack fidelity meeting arises 3 times harmonic and polyphonic pat frequency. If these new frequency weight fall inside bandpass, will cause direct interference to emissive signal, if fall in the signal that other channel will disturb outside bandpass. Want amplifier of pair of radio frequency power for this undertake linearization is handled, so OK the problem of spectrum second birth that better land solves signal. The principle that radio frequency result puts basic linearization technology and method nothing more than be the amplitude that includes sth resembling a net in order to input RF signal and phasic as reference, with output signal is compared, arise then proper corrective. The commonly used technology that implements radio frequency result to put linearization has 3 kinds: Power is answered retreat, beforehand lack fidelity, before make a present of.
1, power is answered retreat
This is the most commonly used method, choose the pipe with greater power to make small-power canal use namely, it is with sacrificial dc power comsumption rises actually result put degree of linearity.
Power answers the power input that removing a standard is a power amplifier to reduce a point from 1dB (amplifier has a linear and dynamic range, inside this limits, the output power of amplifier increases along with power input linear. Increase as power input continuity, amplifier enters saturated area gradually, power gain begins to drop, the output power when dropping gain to lower than linear gain 1dB normally is worth a definition to reduce a point to output the 1dB of power, express with P1dB. ) answer backward retreat 6-10 decibel, the job is in far on the n that is less than 1dB to reduce a point, make power amplifier is far from saturated area, enter linear work area, improve power amplifier thereby 3 rank the coefficient that make shift. General situation, when base when wave power reduces 1dB, 3 rank make shift lack fidelity improvement 2dB.
Power is answered remove a standard simple and easy implementation, do not need to add any additional equipment, it is the method that improves effective of amplifier degree of linearity, defect is efficiency is reduced greatly. Additional, answer fall back on when power certain level, when 3 rank hand in modulation to achieve - when 50dBc is the following, continue to retreat the degree of linearity that will improve amplifier no longer. Accordingly, online sex spends the circumstance with very high demand, rely on power completely to answer retreating is insufficient.
2, beforehand lack fidelity
Beforehand lack fidelity increase before power amplifier namely nonlinear what circuit in order to compensates power amplifier is nonlinear lack fidelity.
Beforehand technology of lack fidelity linearization, its advantage depends on nonexistent stability problem, have broader signal frequency band, can process the signal that contains much carrier wave. Beforehand cost of lack fidelity technology is inferior, the component that chooses carefully by a few is enclosed into onefold module, put in signal source and result repeatedly between, form beforehand lack fidelity and linear result is put. The work that holds mobile Taichun is put already used beforehand lack fidelity technology, it is used only a few component reduced intermodulation production a few DB, but it is very crucial a few DB however.
Beforehand cent of lack fidelity technology is RF beforehand lack fidelity with digital base band beforehand lack fidelity two kinds of main types. RF beforehand lack fidelity and general use imitate circuit to come true, have circuit structure simple, cost is low, easily the advantage such as high frequency, broadband application, defect is improvement of heft of spectrum second birth it is more difficult that heft of less, high-ranking spectrum offsets.
Digital base band beforehand lack fidelity because working frequency is low, can come true with digital circuit, adaptability is strong, and can pass increase sampling frequency and the measure that increase a quantity to change rank number to offset high-ranking intermodulation is lack fidelity, it is a kind of method that has development outlook very much. This kind beforehand lack fidelity implement comprise by adjuster of gain of a vector, the basis searchs a watch (the extent that the content of LUT) will come to control input signal and phasic, break true size to be controlled by the input that searchs a watch beforehand. Once vector gain adjuster is optimized, will offer with result put contrary nonlinear characteristic. Below good case, the intermodulation product that exports at this moment should be passed with date of double mail message put output range is equal and result is phasic contrary, suit oneself namely adjust module should adjust namely the input that searchs a watch, the difference that makes input signal and result to put output signal thereby is the least. Noticing the bag sth resembling a net that inputs signal also is an input that searchs a watch, feedback method comes the lack fidelity output that sampling result puts, send through A/D commutation next suit oneself adjust in DSP, will search a watch newlier then.
3, before make a present of
" of traceable of technology of make a present of feedbacks before " , should say it is not what new technology, be in what 229 time put forward by lab of American shellfish Er early. Besides calibration (feedback) it is to be added at output besides, " feedback " is completely on the concept.
Amplifier of linear of make a present of carries fraction of line of coupler, attenuator, synthesizer, delay time, result before implement wait for composition two annulus road. After radio frequency signal is inputted, classics work is divided implement cent becomes two. Enter all the way advocate power amplifier, because its are nonlinear lack fidelity, output is carried besides what have need enlarge advocate outside frequency signal, still have 3 rank the interference that make shift. From advocate result the coupling in put output one part signal, adopt annulus way of 1 quits amplifier advocate carrier frequency signal, make its are remained only in opposition 3 rank the heft that make shift. 3 rank after the heft that make shift magnifies via assisting amplifier, adopt annulus way 2 quits advocate amplifier is nonlinear the heft making shift of generation, thereby improve result put degree of linearity.
Technology of make a present of offerred the advantage of taller calibration precision already before, was not stabilized again and bandwidth suffers the defect that be restricted. Of course, these good points are traded with high cost, because be in,output calibration, power n is bigger, calibration signal needs to magnify taller power n, this needs additional auxiliary amplifier, and over the index of system of the make a present of before asking the lack fidelity character of itself of this auxiliary amplifier should lie.
The quits demand that result of make a present of puts before is very tall, need to obtain extent, phasic when mixing, delay match, if appear power change, temperature
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