A kind of predistorter and adopt the TD-SCDMA power amplifier module of this predistorter
Technical field
The present invention relates to the power amplifier linearization equipment in a kind of transmitting set field, the analog predistortion power amplifier that relates in particular to a kind of predistorter and adopt this predistorter.
Background technology
3-G (Generation Three mobile communication system) is day by day risen at home at present, and Digital Television and Wimax insert is also becoming the hot spot application field.All there is the linearization problem of transmitting set in these fields, wherein the most importantly linearisation of power amplifier.Present linearization technique has feedforward (FF), three kinds of digital pre-distortion (DPD) and analog predistortions (APD).Feed-forward technique is relatively ripe, is present mainstream technology; The digital pre-distortion technology difficulty is bigger, has only only a few producer to grasp at present; These two kinds of technology are relatively complicated, and offseting of spectral re-growth component is effective, realize the cost height.The analog predistortion technology is a kind of simple relatively technology, can be used in cheaply in the scheme.Just because of can not realize, add the difficulty of predistortion scheme itself, so we often can see that the situation that does not have neutralization effect occurs in actual use with complicated method.Single with regard to technology realizes, it in addition surpassed the difficulty of digital pre-distortion.In some occasion, in the power amplifier module such as TD-SCDMA, because the restriction of cost and volume, we have to use the analog predistortion technology again.
Fig. 1 shows the principle of analog predistortion technology.See also Fig. 1, the principle of predistortion is to place a predistorter 11 to compensate because power amplifier compresses AM/AM and the AM/PM effect that causes before main power amplifier passage, makes final output linearisation.Certainly, Fu Za predistortion scheme has also been considered the solution of memory effect.
As non-linear generator, there are two problems in this method to existing analog predistortion with diode.Non-linear and the non-linear of power amplifier that first diode produces do not match; It two is that the non-linear of diode mainly is third-order intermodulation product, thereby can not reach wide power output dynamic range.
Summary of the invention
The objective of the invention is to address the above problem, a kind of predistorter is provided and has adopted the TD-SCDMA power amplifier module of this predistorter, it can reach non-linear generator the wideband intermodulation component, and wide output dynamic tracking scope is arranged, and the heat that wide bandwidth of operation is become reconciled is followed the tracks of main power amplifier path.
Technical scheme of the present invention is: a kind of predistorter, comprise first distributor, first mixer, be connected first delay line on first branch road between described first distributor and first mixer, and being connected on the loop and first attenuator on second branch road between described first distributor and first mixer successively, wherein said loop further comprises second distributor, second mixer, be connected on first nonlinear amplifier on first branch road between described second distributor and second mixer successively, second attenuator, first phase shifter, and second branch road that is connected described second distributor and second mixer.
Above-mentioned predistorter, wherein, described second branch road is provided with the 3rd attenuator and first linear amplifier that is in series.
Above-mentioned predistorter, wherein, described second branch road is provided with second delay line.
Above-mentioned predistorter wherein, on second branch road of described first distributor, also is provided with the switch that switches usefulness before the input of second distributor.
Above-mentioned predistorter wherein, is provided with second phase shifter after described first attenuator.
A kind of TD-SCDMA power amplifier module, described power amplifier module comprises first directional coupler, first driving stage, the 4th attenuator, predistorter, second driving stage, the 5th attenuator, drive(r) stage, final stage power amplifier, circulator and second directional coupler of series connection successively, and described circulator also is connected with first diverter switch and a LNA successively; Described power amplifier module further comprises a control circuit, described control circuit comprises microprocessor controller, D/A converting circuit and drive circuit, described control circuit is controlled described first diverter switch, described the 4th attenuator, the 5th attenuator and predistorter, described drive circuit connects described drive(r) stage and final stage power amplifier, wherein, described predistorter comprises first distributor, first mixer, be connected first delay line on first branch road between described first distributor and first mixer, and being connected on the loop and first attenuator on second branch road between described first distributor and first mixer successively, wherein said loop further comprises second distributor, second mixer, be connected on first nonlinear amplifier on first branch road between described second distributor and second mixer successively, second attenuator, first phase shifter, and second branch road that is connected described second distributor and second mixer.
Above-mentioned TD-SCDMA power amplifier module wherein, is provided with isolator or resistor network between described drive(r) stage and the final stage power amplifier.
Above-mentioned TD-SCDMA power amplifier module, wherein, described analog predistortion power amplifier comprises that also one is positioned at second diverter switch of input, is used for the switching of receiving and transmitting signal, and the switch port of described second diverter switch connects described first directional coupler and LNA respectively.
The present invention contrasts prior art following beneficial effect: be provided with two loops in the predistorter of the present invention, first loop is used to produce nonlinear component, offsets carrier component; Second loop is used to produce complete pre-distorted signals, comprises the nonlinear component of original carrier component and needs.This predistorter can obtain better linearity together with the power amplifier passage to be improved.This predistorter also is applicable to the TD-SCDMA power amplifier module.The invention enables the analog predistortion device to have wideband intermodulation component, wide output dynamic tracking scope, wide bandwidth of operation and good heat to follow the tracks of main power amplifier path.
Description of drawings
Fig. 1 is the cubic model figure of predistortion principle.
Fig. 2 is the circuit diagram of the preferred embodiment of analog predistortion device of the present invention.
Fig. 3 is the circuit diagram of the preferred embodiment of TD-SCDMA power amplifier module of the present invention.
Embodiment
The invention will be further described below in conjunction with drawings and Examples.
Fig. 2 shows the circuit of analog predistortion device one preferred embodiment of the present invention.As shown in Figure 2, this predistorter comprise first distributor 202, first mixer 219, be connected first delay line 204 on first branch road between first distributor 202 and first mixer 219 and be connected on first distributor 202 successively and first mixer 219 between second branch road on switch 205, loop 230, first attenuator 217 and second phase shifter 218.In loop 230, be provided with second distributor 207, second mixer 212, be connected on first nonlinear amplifier 209, second attenuator 210, first phase shifter 211 on first branch road between second distributor 207 and second mixer 212 successively, and be connected on the 3rd attenuator 213, first linear amplifier 214 and second delay line 215 on second branch road between second distributor 207 and second mixer 212 successively.Wherein, resistance 203,206,208,216,220 is 50 ohm, and resistance 206 is as absorbing load, and mating with the 3dB bridge of other used.And distributor 202,207 is 3dB, 90 degree distributors, and mixer 219,212 is 3dB, 90 degree mixers.
When signal is input to first distributor 202, the effect of this distributor 202 is that the purified signal of input is divided into two-way up and down, one road to first delay line 204, and another road is to switch 205.This first delay line 204 is done to postpone usefulness, and its retardation equals the time of delay of following branch road.This switch 205 is used for switching and has or not predistortion function.When switching to resistance 206, switch 205 just shielded predistortion circuit.The setting of switch has two effects: the one, the time can compare the effect of predistortion in debugging; The 2nd, hour can shield predistortion circuit at signal.Signal is through switch 205 to second distributors 207, and this second distributor 207 is the same with first distributor 202, also plays distributional effects, and purified signal is divided into two-way again, one road to first nonlinear amplifier 209, another road to the three attenuators 213.On the way, first nonlinear amplifier 209 produces the nonlinear component consistent with the power amplifier passage, the nonlinear component of second attenuator 210 and 209 outputs of 211 pairs first nonlinear amplifiers of first phase shifter carries out the adjustment of signal amplitude and phase place, and signal is again to second mixer 212.In addition on the way, the signal of first linear amplifier, 214 linear amplification after 213 decay of the 3rd attenuator, this signal by second delay line 215 postpone the back second mixer 212 with above non-linear branch close the road, thereby offset carrier signal, stayed that nonlinear component is sent into first attenuator 217 and second phase shifter 218 is done amplitude and phase place adjustment.It with on first mixer 219, close the road through the purified signal behind first delay line 204.The signal that closes behind the road is complete pre-distorted signals, and it and subsequently power amplifier compressed signal complementation make the high linear high-power signal of whole power amplifier output.
There are two rings in whole predistortion circuit, and first loop 230 is used to produce nonlinear component, offsets carrier component; Second loop 240 is used to produce complete pre-distorted signals.Should be understood that second phase shifter 218, switch 205 and resistance 206 can omit.In second branch road of second distributor 207, can omit delay line 215 or omit the 3rd attenuator 213, first linear amplifier 214.
Fig. 3 shows the circuit of the TD-SCDMA power amplifier module embodiment that adopts this predistorter.As shown in Figure 3, this power amplifier module comprises second diverter switch 301, first directional coupler 302, first driving stage 304, the 4th attenuator 305, predistorter 306, second driving stage 307, the 5th attenuator 308, drive(r) stage 309, isolator 310, final stage power amplifier 311, circulator 312, second directional coupler 313 of series connection successively.Also be connected with first diverter switch 315 and LNA 317 on the circulator 312 in addition, this LNA 317 is connected with second diverter switch 301 simultaneously.Power amplifier module also comprises a control circuit 318, and control circuit 318 mainly is made up of other circuit of microprocessor controller 401, D/A converting circuit 402, drive circuit 403 and some.This control circuit 318 connects the 4th attenuator 305, the 5th attenuator 308 and predistorter 306.This drive circuit 403 connects drive(r) stage 309 and final stage power amplifier 311.
Signal at first is input to second diverter switch 301, and this switch is used for the transmitting-receiving switching of TX (posting a letter) and RX (collection of letters).First directional coupler 302 and second directional coupler 313 are coupled out part input and output power respectively and are used for separately input and output power detection, the reflection power detection that reverse ouput power detection circuit is used for delivery outlet can also be set if necessary, detect the standing-wave ratio information that obtains together with power output.First driving stage 304 and second driving stage 307 are used for amplifying to improve signal level, and the requirement that gains according to real system can increase and decrease its progression.305 controls of the 4th attenuator enter the level of predistorter 306, make the neutralization effect of predistorter 306 reach best.The function of predistorter 306 is its aforesaid functions.The 5th attenuator 308 is used to adjust the gain of whole power amplifier.Drive(r) stage 309 and final stage power amplifier 311 are used for high-power amplification.Because they are heating active elements, its bias point can be along with temperature drift, thereby influence the linearity of power amplifier.Here introduce temperature-compensating, make that the temperature variant influence of power amplifier is little.Isolator 310 is used for inter-stage and isolates, and can adopt resistor network to replace when power is little.Circulator 312 is used for the protection of power amplifier output, can also make the receive path of RX, makes TX and RX passage that good isolation be arranged.First diverter switch 315 is used to switch the state of TX and RX, further protects the RX passage.LNA 317 is used to amplify the small-signal of RX path.318 pairs of whole power amplifier modules of control circuit are controlled, and comprise the control to first diverter switch 315.Control circuit 318 utilizes the level of 305 pairs of the 4th attenuators input predistorter 306 to control and thereby the control of predistorter 306 is reached good intermodulation neutralization effect.Control circuit 318 utilizes the gain of the 5th attenuator 308 Adjustment System, the biasing of control back level power amplifier 309,311, and the protection of controlling whole power amplifier damages and control and outside interface communication to avoid power amplifier.Microprocessor controller and DAC remove to control power tube bias voltage, attenuator, phase shifter and nonlinear generator after signal is driven, along with the variation of temperature and level etc., these values are adjusted automatically.Should be understood that in the present embodiment second diverter switch 301, inter-stage isolator 310 are omissible, driver 304,307 can omit or adjust.
Should be understood that predistorter of the present invention also can be used for cdma, WCDMA, Wimax and Digital TV power amplifier module.
The foregoing description provides to those of ordinary skills and realizes or use of the present invention; those of ordinary skills can be under the situation that does not break away from invention thought of the present invention; the foregoing description is made various modifications or variation; thereby protection scope of the present invention do not limit by the foregoing description, and should be the maximum magnitude that meets the inventive features that claims mention.