CN106777533B - Power amplifier nonlinear simulation method based on lookup table - Google Patents
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Abstract
The invention discloses a lookup table-based power amplifier nonlinear simulation method, which comprises the following steps: establishing a lookup table LUT according to amplitude nonlinear AM-AM characteristics and amplitude-phase conversion nonlinear AM-PM characteristics of the power amplifier; receiving complex baseband input signal x (t) with any power, performing controllable gain amplification on the complex baseband input signal in an analog domain to generate an initial state power-adjusted signal xG(t); for xG(t) A/D sampling to generate corresponding digital domain A/D sampling signal xG(m) for xG(m) carrying out analog domain AGC coarse adjustment and digital domain power factor fine adjustment to obtain xF(m), calculating to obtain xF(m) instantaneous modulus and argument, then calculating the LUT address; looking up an AM-AM lookup table and an AM-PM lookup table to generate an instantaneous module value and an instantaneous argument of the power amplifier nonlinear analog output signal; and calculating to obtain a power amplifier nonlinear analog output digital signal represented by the in-phase component and the quadrature component, and performing D/A conversion to generate a final power amplifier nonlinear analog output signal. The invention has the outstanding advantages of wide application range, strong universality, high simulation precision and the like.
Description
Technical Field
The invention belongs to the technical field of power amplifier characteristic simulation, and relates to a power amplifier nonlinear simulation method based on a lookup table.
Background
The power amplifier is one of the most important nonlinear devices in satellite communication, measurement and control systems and the like, and mainly comprises nonlinear elements such as transistors, capacitors, inductors and the like. Generally, in order to improve the working efficiency, the actual power amplifier is often operated near the saturation point, and the nonlinear influence is serious. The nonlinearity of the power amplifier inevitably causes distortion of data transmission signals, intersymbol interference is generated, a constellation diagram is overturned, and the error rate is increased. In addition, the signal spectrum is expanded, adjacent channel interference is generated, the frequency band utilization rate is reduced, and the system capacity is influenced. The method has important significance for realistically simulating the channel characteristics, fully verifying and testing the functions and the performances of systems such as satellite communication, measurement and control and the like under the nonlinear influence of the power amplifier and developing the research work of the nonlinear simulation theory and the implementation method of the power amplifier.
At present, the study of the nonlinear characteristic of the power amplifier by scholars at home and abroad mainly focuses on the two aspects of the nonlinear modeling and the linearization technology of the power amplifier. The model research of the power amplifier is an important component of circuit and system simulation analysis, and aims to describe an actual power amplifier by using a set of mathematical equations. According to the difference of the types of the model extraction data, the models of the power amplifier are mainly divided into three types: physical models, equivalent circuit models, and behavioral models, with behavioral models being the most widely used. Representative behavior models mainly include memoryless models such as Taylor series, Saleh and Rapp, and memoryless models such as Volterra series, Wiener and Hammertein. In contrast, the linearization technique of power amplifier is the most direct technique for reducing the nonlinear influence of power amplifier, and mainly includes a back-off method, a negative feedback method, a feed-forward method, a predistortion method, an envelope reconstruction method, a harmonic injection method, and the like, where the predistortion technique is a hot spot for researchers at home and abroad. The research contents of the two aspects establish a description means of the nonlinear characteristic of the power amplifier, provide an effective method for reducing the nonlinear distortion of the power amplifier, and lay a foundation for nonlinear simulation of the power amplifier.
However, at present, no report is found on the non-linear simulation of power amplifiers at home and abroad, and meanwhile, the mature channel simulation products at home and abroad often do not include the non-linear simulation function of power amplifiers.
Disclosure of Invention
In view of the above, the present invention provides a lookup table based nonlinear simulation method for power amplifier.
In order to achieve the purpose, the technical scheme of the invention is as follows: a power amplifier nonlinear simulation method based on a lookup table comprises the following steps:
step 1: according to the amplitude nonlinear AM-AM characteristic G (r) and the amplitude-phase conversion nonlinear AM-PM characteristic psi (r) of the power amplifier, establishing a lookup table LUT (look-up table) for power amplifier nonlinear simulation under the condition of limited word length, namely:
wherein A isN_out(k) And
respectively AM-AM and AM-PM lookup tables under the condition of limited word length, W is preset LUT address line width, k is LUT address, VrefFor the A/D reference level, N, during the A/D sampling in the subsequent step 3LUTFor a predetermined number of bits of LUT expansion, r (k) is the input amplitude discretized by the functions G (r) and psi (r), i.e.
Wherein r ∈ [ r ]min,rmax]For any input amplitude range of AM-AM and AM-PM curves, rminTo a minimum input amplitude, rmaxFor maximum input amplitude, both units are in volts.
Step 2: receiving complex baseband input signal x (t) with any power, performing controllable gain amplification on the complex baseband input signal in an analog domain to generate an initial state power-adjusted signal xG(t), namely: x is the number ofG(t)＝G0x (t); wherein G is0For gain in the analog domain, G0The corresponding logarithmic gain is noted as GdB0。
And step 3: for the initial state power adjusted signal xG(t) A/D sampling to generate corresponding digital domain A/D sampling signal xG(m) that is
Wherein x isG_t(mTs) Indicating that the signal has been sampled in only the time dimension, xG(m) is at xG_t(mTs) On the basis, the amplitude dimension is quantized, VrefFor A/D reference level, NsigFor A/D significant bits, m is a discrete time variable in the digital domain, TsIs the sampling period.
And 4, step 4: for A/D sampled signal xG(m) making power statistics, i.e.
Wherein, PDIs xG(m) digital domain power, PsIs xG(m) corresponding analog domain signal xG(t) analog domain power, CpFor power conversion coefficients in the digital and analogue domains, i.e.
M is the number of discrete time variables in the sampling period.
And 5: the digital domain power P obtained according to the step 4DAnd a set automatic gain control threshold range [ P ]DG1,PDG2]Gain G of the analog domain by cyclic control0And coarsely adjusting the working point of the power amplifier, wherein the result of the coarse adjustment is as follows: when adjusted in place, the digital domain power P of the A/D sampling signalDSatisfies the following conditions: pD∈[PDG1,PDG2]；
Step 6: the power amplifier working point is roughly adjusted in the step 5Resultant digital signal xG(m) performing power fine adjustment according to the following formula to obtain a fine-adjusted complex signal
Wherein the content of the first and second substances,
indicating a rounding-down operation, FNFor fine-tuning the factor for the quantized power, i.e.
Wherein, PdB_objFor analog domain logarithmic target power, PDCompleting signal x for coarse tuning of AGCG(m) digital domain power, CpFor power conversion coefficients in the analog and digital domains, NFThe bit expansion bit number of the power fine adjustment factor is R, and the R is input impedance;
and 7: x is to beF(m) is expressed as a complex signal form:
xF(m)＝xF_I(m)+jxF_Q(m); x is to beF(m)xF(m)＝xF_I(m)+jxF_Q(m) converting direct coordinate to polar coordinate, and calculating to obtain instantaneous modulus | xF(m) | and minor angle
Namely, it is
Wherein int [ 2 ]]Denotes a rounding operation, atan [ alpha ], [ alpha ]]Is an arctangent function with a range of [ - π, π]，NLUTBit number expansion for LUT;
and 8: calculating the instantaneous modulus | x according to step 7F(m) l, calculating the LUT address
Wherein [ A ]N_min,AN_max]And is the input amplitude range of the quantized AM-AM and AM-PM curves, in particular
Wherein r ∈ [ r ]min,rmax]The input amplitude ranges of the original AM-AM and AM-PM curves.
And step 9: according to the LUT address k (m) calculated in the step 8, searching the AM-AM lookup table established in the step 1, and generating an instantaneous module value of the power amplifier nonlinear analog output signal y (m), namely | y (m) | ═ AN_out(k)|k＝k(m)。
Wherein, | y (m) | power amplifier nonlinear analog output signal y (m) instantaneous modulus.
Meanwhile, the established AM-PM lookup table in the step 1 is searched according to the LUT address calculated in the step 8, and the output of the AM-PM lookup table is compared with the instantaneous supplementary angle calculated in the step 7
Adding to obtain instantaneous auxiliary angle of power amplifier nonlinear analog output signal
Namely, it is
Wherein the content of the first and second substances,
the instantaneous argument of the nonlinear analog output signal y (m) is scaled.
Step 10: according to the instantaneous molding y (m) calculated in the step 8 and the instantaneous supplementary angle calculated in the step 9
Polar coordinate-rectangular coordinate transformation is carried out according to the following formula, and power amplifier nonlinear analog output represented by in-phase and orthogonal components is obtained through calculationDigital signals, i.e.
Wherein, yI(m) and yQ(m) in-phase and quadrature components, N, of y (m), respectivelycosThe bit expansion number is the function value of sine sin and cosine cos.
Step 11: for the in-phase component y generated in step 10I(m) and the orthogonal component yQ(m) D/A conversion is carried out, and the final power amplifier nonlinear analog output signal can be generated, namely y (t) ═ yI(t)+yQ(t)。
Further, the automatic gain control threshold range [ P ] set in step 5DG1,PDG2]The setting method is as follows:
obtaining the logarithmic power P of analog domain A/D quantization noise by testing AD significant bit or actual measurementdB_noiseThe power amplifier working point set by the user is PdB_setThen the logarithmic target power under the influence of quantization noise is
The dB subscript represents logarithmic power, namely, a power amplifier working point, quantization noise power and target power set by a user all take dBm as a unit;
according to logarithmic target power PdB_objThe logarithmic power control threshold of the analog domain is set as
Wherein, Δ PdBA threshold range is controlled for any logarithmic power;
according to the conversion relation between the power of the digital domain and the power of the analog domain after A/D conversion, the automatic gain control threshold of the digital domain is calculated according to the following formula
Wherein，PDG1And PDG2Is the digital domain automatic gain control threshold, and R is the input impedance.
Preferably, the specific process of roughly adjusting the operating point of the power amplifier is as follows:
1) if PD＜PDG1Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0+ΔGdB，ΔGdBIs a preset stepping value, and calculates:
2) If PD＞PDG2Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0-ΔGdBAnd calculates:
Wherein, Δ GdBIs the logarithmic gain adjustment of the controllable gain amplifier.
Has the advantages that:
aiming at two key factors which affect the nonlinear distortion of the power amplifier and are a nonlinear model of the power amplifier and a working point of the power amplifier, the invention adopts an LUT technology to establish a general description means of any nonlinear model of the power amplifier or actually measuring the characteristics of AM-AM and AM-PM, and adopts a two-stage adjustment scheme of analog domain AGC coarse adjustment and digital domain power factor fine adjustment to realize the accurate adjustment of the working point of the power amplifier of any power input signal. Therefore, the LUT-based power amplifier nonlinear simulation method has the outstanding advantages of wide application range, strong universality, high simulation precision and the like. In addition, the invention also fully considers the limited word length effect inevitably introduced in the engineering realization and deduces the nonlinear analog capacity of the power amplifier under the condition of the limited word length. Therefore, the method provided by the invention is particularly suitable for realizing the FPGA and has the outstanding advantage of high engineering realization degree.
Drawings
FIG. 1 is a block diagram of the system of the present invention.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
For a (memoryless means non-linear characteristic and input independence) memoryless power amplifier, a complex function is usually used to describe its complex gain, i.e.
f(r)＝G(r)exp[jψ(r)](1)
Where r is the amplitude of the input signal, g (r) and ψ (r) are real functions, which describe the amplitude non-linearity (AM-AM conversion) and phase non-linearity (AM-PM conversion), respectively, of the power amplifier.
If the power amplifier input signal is equivalent to the complex baseband and is assumed to be x (t), the power amplifier output signal y (t) can be expressed as
y(t)＝G{|x(t)|}exp{j[arg[x(t)]+ψ{|x(t)|}]} (2)
And there is:
the power amplifier comprises a power amplifier input complex signal x (t), an I (x (t)) I and arg { x (t) } which respectively represent the instantaneous module value and the auxiliary angle of the power amplifier input complex signal x (t), and an I (y (t)) I and arg { y (t) } which respectively represent the instantaneous module value and the auxiliary angle of the power amplifier output complex signal y (t).
The method provided by the invention is to receive a complex baseband input signal x (t), and according to the AM-AM (amplitude non-linearity) characteristic G (r) and AM-PM (amplitude phase transition characteristic) characteristic psi (r) of a power amplifier and a power amplifier working point P set by a userdB_setAnd accurately generating an analog output signal y (t) corresponding to the output of the power amplifier. (in the prior art, the FPGA may be adopted to realize the two characteristics by modeling and establishing a function model based on the real characteristics of the AM-AMAM-PM function, but the engineering realization amount is very large)
The method is realized by the following technical scheme:
a digital power amplifier nonlinear analog method based on LUT technology is implemented as follows:
step 1: establishing LUT (look-up table) for power amplifier nonlinear simulation under the condition of limited word length according to power amplifier AM-AM characteristic G (r) and AM-PM characteristic psi (r), namely
Wherein A isN_out(k) And
respectively AM-AM and AM-PM lookup tables under the condition of limited word length, W is LUT address line width (preset value, related to analog precision, and can be selected as 12 in practical implementation), k is LUT address, VrefFor A/D reference level, NLUTFor the number of bits of the LUT, r (k) is the input amplitude discretized by the functions G (r) and psi (r), i.e.
Wherein r ∈ [ r ]min,rmax]To set the input amplitude range of any AM-AM and AM-PM curves, rminTo a minimum input amplitude, rmaxFor maximum input amplitude, both units are in volts.
Step 2: receiving complex baseband input signal x (t) with any power, performing controllable gain amplification (realized by fixed gain and numerical control attenuation) in an analog domain to generate signal xG(t) that is
xG(t)＝G0x(t) (6)
Wherein G is0For analog domain gain, its corresponding logarithmic gain is denoted as GdB0。
And step 3: for the initial state power adjusted signal xG(t) A/D sampling to generate corresponding digital domain A/D sampling signal xG(m) that is
Wherein x isG_t(mTs) Indicating that the signal has been sampled in only the time dimension, xG(m) is based thereon a quantification of the amplitude dimension, VrefFor A/D reference level, NsigIs the A/D valid bit, m is the discrete time variable of the digital domain, and Ts is the sampling period.
And 4, step 4: for A/D sampled signal xG(m) making power statistics, i.e.
Wherein, PDIs xG(m) digital domain power, PsIs xG(m) corresponding analog domain signal xGAnd (t) analog domain power, wherein M is the number of discrete time variables in the sampling period. CpFor power conversion coefficients in the digital and analogue domains, i.e.
And 5: according to the step 4, the power statistic result PDAnd Automatic Gain Control (AGC) threshold range [ P ]DG1,PDG2]By cyclically controlling the controllable gain amplifier of the analog domain (i.e. controlling the gain G)0) So as to realize the coarse adjustment process of the working point of the power amplifier. When the digital domain power of the A/D sampling signal is adjusted in place, the digital domain power of the A/D sampling signal meets the following conditions: pD∈[PDG1,PDG2]。
The principle of the steps is as follows:
if the logarithmic power of the analog domain A/D quantization noise is assumed to be PdB_noise(obtained by testing AD valid bit or actual measurement), the power amplifier working point set by the user is PdB_setThen the target power under the influence of quantization noise can be calculated as follows
The "dB" subscript represents the logarithmic power, i.e., the power amplifier operating point, the quantization noise power, and the target power set by the user are all in dBm.
According to logarithmic target power PdB_objThe logarithmic power control threshold of the analog domain can be set as
Wherein, Δ PdBThe threshold range is any logarithmic power control threshold range (in practical implementation, the value can be between 1 dB and 2 dB).
According to the conversion relation between the power of the digital domain and the power of the analog domain after A/D conversion, the automatic gain control threshold of the digital domain can be calculated according to the following formula
Wherein, PDG1And PDG2Is the digital domain automatic gain control threshold, and R is the input impedance.
According to the power statistical result PDAnd digital domain AGC threshold range [ P ]DG1,PDG2]The course of rough adjustment of the working point of the power amplifier is as follows:
1) if PD＜PDG1Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0+ΔGdB(step-by-step), and calculates:
2) If PD＞PDG2Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0-ΔGdBAnd calculates:
Wherein, Δ GdBIs the logarithmic gain adjustment of the controllable gain amplifier.
Step 6: for the digital signal x of which the power amplifier working point is coarsely adjusted in the step 5G(m) (the power of which satisfies PD∈[PDG1,PDG2]) The power trimming is performed as follows, i.e.
Wherein the content of the first and second substances,
indicating a rounding-down operation, FNFor fine-tuning the factor for the quantized power, i.e.
Wherein, PdB_objLogarithmic target power (unit: dBm), P, for the analog domainDCompleting signal x for coarse tuning of AGCG(m) digital domain power, CpFor power conversion coefficients in the analog and digital domains, NFFor the number of bits of the power fine-tuning factor, R is an input impedance of 50 Ω.
And 7: for the complex signal x after power fine adjustmentF(m)＝xF_I(m)+jxF_Q(m) converting direct coordinate to polar coordinate, and calculating to obtain instantaneous modulus | xF(m) | and minor angle
Namely, it is
Wherein int [ 2 ]]Denotes a rounding operation, atan [ alpha ], [ alpha ]]Is an arctangent function, the range thereofIs [ - π, π]，NLUTBit numbers are expanded for the LUT. That is to say that the first and second electrodes,
bit number N is expanded according to LUTLUTAnd carrying out bit expansion processing.
And 8: instantaneous mold | x calculated according to step 7F(m) l, calculating the LUT address
Wherein [ A ]N_min,AN_max]And is the input amplitude range of the quantized AM-AM and AM-PM curves, in particular
Wherein r ∈ [ r ]min,rmax]The input amplitude ranges of the original AM-AM and AM-PM curves.
And step 9: according to the LUT address k (m) calculated in the step 8, searching the AM-AM lookup table established in the step 1 to generate the instantaneous module value of the power amplifier nonlinear analog output signal y (m), namely
|y(m)|＝AN_out(k)|k＝k(m)(18)
Wherein, | y (m) | power amplifier nonlinear analog output signal y (m) instantaneous modulus.
Meanwhile, the established AM-PM lookup table in the step 1 is searched according to the LUT address calculated in the step 8, and the output of the AM-PM lookup table is compared with the instantaneous supplementary angle calculated in the step 7
Adding to obtain instantaneous auxiliary angle of power amplifier nonlinear analog output signal
Namely, it is
Wherein the content of the first and second substances,
the instantaneous argument of the nonlinear analog output signal y (m) is scaled.
Step 10: according to the instantaneous molding y (m) calculated in the step 8 and the instantaneous supplementary angle calculated in the step 9
The polar coordinate-rectangular coordinate transformation is carried out according to the following formula, and the power amplifier nonlinear analog output digital signal expressed by in-phase and orthogonal components is obtained through calculation, namely
Wherein, yI(m) and yQ(m) in-phase and quadrature components, N, of y (m), respectivelycosThe bit expansion number is the function value of sine sin and cosine cos.
Step 11: for the in-phase component y generated in step 10I(m) and the orthogonal component yQ(m) D/A conversion is carried out to generate the final nonlinear analog output signal of the power amplifier, namely
y(t)＝yI(t)+yQ(t) (21)
Through the steps 1 to 12, the nonlinear simulation of the power amplifier of the complex baseband input signal x (t) with any power is realized according to any power amplifier nonlinear model and power amplifier working point setting, and the power amplifier nonlinear simulation output signal y (t) is accurately generated.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A power amplifier nonlinear simulation method based on a lookup table is characterized by comprising the following steps:
step 1: according to the amplitude nonlinear AM-AM characteristic G (r) and the amplitude-phase conversion nonlinear AM-PM characteristic psi (r) of the power amplifier, establishing a lookup table LUT (look-up table) for power amplifier nonlinear simulation under the condition of limited word length, namely:
wherein A isN_out(k) And
respectively AM-AM and AM-PM lookup tables under the condition of limited word length, W is preset LUT address line width, k is LUT address, VrefFor the A/D reference level, N, during the A/D sampling in the subsequent step 3LUTFor a predetermined number of bits of LUT expansion, r (k) is the input amplitude discretized by the functions G (r) and psi (r), i.e.
Wherein r ∈ [ r ]min,rmax]For any input amplitude range of AM-AM and AM-PM curves, rminTo a minimum input amplitude, rmaxThe maximum input amplitude is the unit of both in volts;
step 2: receiving complex baseband input signal x (t) with any power, performing controllable gain amplification on the complex baseband input signal in an analog domain to generate an initial state power-adjusted signal xG(t), namely: x is the number ofG(t)＝G0x (t); wherein G is0For gain in the analog domain, G0The corresponding logarithmic gain is noted as GdB0；
And step 3: for the initial state power adjusted signal xG(t) A/D sampling to generate corresponding digital domain A/D sampling signal xG(m) that is
Wherein x isG_t(mTs) Indicating that the signal has been sampled in only the time dimension, xG(m) is at xG_t(mTs) On the basis, the amplitude dimension is quantized, VrefFor A/D reference level, NsigFor A/D significant bits, m is a discrete time variable in the digital domain, TsIs a sampling period;
and 4, step 4: for A/D sampled signal xG(m) making power statistics, i.e.
Wherein, PDIs xG(m) digital domain power, PsIs xG(m) corresponding analog domain signal xG(t) analog domain power, CpFor power conversion coefficients in the digital and analogue domains, i.e.
M is the number of discrete time variables in a sampling period;
and 5: the digital domain power P obtained according to the step 4DAnd a set automatic gain control threshold range [ P ]DG1,PDG2]Gain G of the analog domain by cyclic control0And coarsely adjusting the working point of the power amplifier, wherein the result of the coarse adjustment is as follows: when adjusted in place, the digital domain power P of the A/D sampling signalDSatisfies the following conditions: pD∈[PDG1,PDG2]；
Step 6: for the digital signal x of which the power amplifier working point is coarsely adjusted in the step 5G(m) performing power fine adjustment according to the following formula to obtain a fine-adjusted complex signal
Wherein the content of the first and second substances,
indicating a rounding-down operation, FNFor fine-tuning the factor for the quantized power, i.e.
Wherein, PdB_objFor analog domain logarithmic target power, PDCompleting signal x for coarse tuning of AGCG(m) digital domain power, CpFor power conversion coefficients in the analog and digital domains, NFThe bit expansion bit number of the power fine adjustment factor is R, and the R is input impedance;
and 7: x is to beF(m) is expressed as a complex signal form: x is the number ofF(m)＝xF_I(m)+jxF_Q(m)；
X is to beF(m)＝xF_I(m)+jxF_Q(m) converting rectangular coordinate to polar coordinate, and calculating to obtain instantaneous modulus | xF(m) | and minor angle
Namely, it is
Wherein int [ 2 ]]Denotes a rounding operation, atan [ alpha ], [ alpha ]]Is an arctangent function with a range of [ - π, π]，NLUTBit number expansion for LUT;
and 8: calculating the instantaneous modulus | x according to step 7F(m) l, calculating the LUT address
Wherein [ A ]N_min,AN_max]And is the input amplitude range of the quantized AM-AM and AM-PM curves, in particular
Wherein r ∈ [ r ]min,rmax]The input amplitude ranges of the original AM-AM and AM-PM curves are obtained;
and step 9: looking up the LUT address k (m) calculated in step 8 after step 1The built AM-AM lookup table generates the instantaneous module value of the power amplifier nonlinear analog output signal y (m), namely | y (m) | AN_out(k)|k＝k(m)；
Wherein, | y (m) | power amplifier nonlinear analog output signal y (m) instantaneous modulus;
meanwhile, the established AM-PM lookup table in the step 1 is searched according to the LUT address calculated in the step 8, and the output of the AM-PM lookup table is compared with the instantaneous supplementary angle calculated in the step 7
Adding to obtain instantaneous auxiliary angle of power amplifier nonlinear analog output signal
Namely, it is
Wherein the content of the first and second substances,
(ii) discharging the instantaneous argument of the nonlinear analog output signal y (m);
step 10: according to the instantaneous modulus | y (m) | of y (m) calculated in the step 9 and the instantaneous argument calculated in the step 9
The polar coordinate-rectangular coordinate transformation is carried out according to the following formula, and the power amplifier nonlinear analog output digital signal expressed by in-phase and orthogonal components is obtained through calculation, namely
Wherein, yI(m) and yQ(m) in-phase and quadrature components, N, of y (m), respectivelycosThe bit expansion number is the function value of sine sin and cosine cos;
step 11: for the in-phase component y generated in step 10I(m) and the orthogonal component yQ(m) D/A conversion is carried out, and the final power amplifier nonlinear analog output signal can be generated, namely y (t) ═ yI(t)+yQ(t)。
2. The lookup table based nonlinear analog method of power amplifier as claimed in claim 1 wherein the automatic gain control threshold range [ P ] set in step 5DG1,PDG2]The setting method is as follows:
obtaining the logarithmic power P of analog domain A/D quantization noise by testing AD significant bit or actual measurementdB_noiseThe power amplifier working point set by the user is PdB_setThen the logarithmic target power under the influence of quantization noise is
The dB subscript represents logarithmic power, namely, a power amplifier working point, quantization noise power and target power set by a user all take dBm as a unit;
according to logarithmic target power PdB_objThe logarithmic power control threshold of the analog domain is set as
Wherein, Δ PdBA threshold range is controlled for any logarithmic power;
according to the conversion relation between the power of the digital domain and the power of the analog domain after A/D conversion, the automatic gain control threshold of the digital domain is calculated according to the following formula
Wherein, PDG1And PDG2Is the digital domain automatic gain control threshold, and R is the input impedance.
3. The lookup table-based nonlinear analog method for a power amplifier as claimed in claim 2, wherein the specific process of coarsely adjusting the operating point of the power amplifier is as follows:
1) if PD＜PDG1Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0+ΔGdB，ΔGdBThe logarithmic gain adjustment for the controllable gain amplifier is calculated
And (3) controlling the controllable gain amplifier in the step (2) until the following conditions are met: pD∈[PDG1,PDG2]；
2) If PD＞PDG2Let the logarithmic gain of the analog domain controllable gain amplifier be GdB0＝GdB0-ΔGdBAnd calculate out
And (3) controlling the controllable gain amplifier in the step (2) until the following conditions are met: pD∈[PDG1,PDG2]。
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