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Doherty power amplifier basics of accounting

JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser. Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product. Fully updated to address cutting-edge technologies, the new edition of this practical guide provides comprehensive, state-of-the-art coverage of RF and microwave power amplifier design. The book describes both existing and new schematic configurations, theoretical approaches, circuit simulation results, and implementation techniques. New chapters discuss linearization and efficiency enhancement and high-efficiency Doherty power amplifiers.


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WATCH RELATED VIDEO: Doherty Amplifier (NXP BLD6G22L-150) Teardown From a Nokia Siemens PA

EP2541759A1 - Doherty power amplifier and implementation method therefor - Google Patents


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Download Free PDF. Part I: Theory. A short summary of this paper. Download PDF. Translate PDF. Starting from the simplified model of an active device, the analysis of the AB-C Doherty behavior is carried out as a function of the input signal. In particular, the proposed approach is based on the analysis of the output drain current waveforms gen- erated by the two active devices, while assuming a Tuned Load configuration i.

A closed form formulation is derived in order to directly design an AB-C Doherty amplifier, while fully understanding the basis of its physical behavior. Finally, which Doherty parameters can be chosen by the designer or have to be implicitly fixed are discussed and clarified. V C Wiley Periodicals, Inc. Keywords: Doherty Amplifier; power amplifier; high efficiency; main; auxiliary; active load modulation I.

More- over, the high average efficiency becomes a key fac- In recent years, the rapid development of communi- tor in mobile communication systems to increase bat- cation systems and the consequently increasing tery lifetime. Therefore, solutions to improve the request to transmit growing amounts of information average efficiency are becoming mandatory in mod- has pushed the development of complex modulations ern power amplifier PAs design.

From the RF In such a scenario, the original idea proposed by transmitter site, the new signal coding implies the ampli- W. Doherty in [4] seems to be a promising fication of signals characterized by larger time-vary- and feasible solution to improve the average effi- ing envelope behaviors, with typical peak-to-average ciency [5—8]. As a based on the idea to modulate the load presented to consequence, such critical operating condition causes an active device vacuum tube in the original article , a lower average efficiency in classical power stages namely Main or Carrier , exploiting the active load Class AB, B, F, etc.

In fact, as the power namely Auxiliary or Peaking. The resulting typical density of active devices increases while their size is DPA implementation is reported in Figure 1, and the reduced, becoming more compact, the lower effi- behavior of the theoretical expected drain efficiencies of each device and of the overall DPA stage is Correspondence to: R.

C Wiley Periodicals, Inc. However, if the input power splitter dimensioning Figure 1. Typical DPA configuration. Simi- larly, the approach adopted to find an analytical way For a low input power level, only the Main device to properly fix the Class C bias level and the uneven is active, whereas the Auxiliary is kept off.

When the power splitting level is mainly based on a linear input power is increased and the Main device reaches extension of the classical B-B Doherty design rela- its saturation condition, and then the Auxiliary is tionships [16]. In fact, only the final values of the turned on, modulating the load seen by the Main de- resulting RF current components, due to different de- vice.

To optimize both the active device behaviors vice biasing classes, are examined, whereas the actual i. The relevant nonlin- ances. Such a network, which has to be connected at ear behavioral relationships, together with accurate the output of the Main PA, can be easily realized by and useful design guidelines are discussed.

Finally, the DPA power gain behavior from the two devices. In the first DPA implementation [4], both devices The proposed theory has been validated through Main and Auxiliary were biased in Class B experimental results, showing the right approach to condition, carrying out the relevant design relation- design a Doherty amplifier, which will be discussed ships [4, 12]. It means that it becomes mandatory to complicate the hardware implementation using a switching cir- cuitry to control the on-off Auxiliary condition [13].

To avoid such criticisms, a proper Class C bias condi- tion for the Auxiliary device is typically adopted. However, in this case the input power splitter dimen- sioning becomes a further design key facet [6, 14].

Finally, a pure Class B bias condition for the Main device does not seem to be advisable because of the large distortion generated by the active device biased near the pinch-off cross-over distortion. To avoid this further drawback, usually a Class AB bias condi- tion for the Main is preferred, resulting in a small Figure 2.

Theoretical drain efficiency behavior of DPA. For this purpose, in the following The behavioral analysis of the DPA can be performed expressions the subscript AB or Main and C or considering the following operating conditions refer- Aux will be used, respectively, for the quantities ring to Fig. The resulting output current waveforms for the 1. Low-power region where only the Main Main and Auxiliary devices are plotted in Figures 3a device is on and the Auxiliary is kept off. It and 3b, respectively.

Medium-power region when both devices are current value IMax,Main : active, i. The corresponding scheme to be analyzed becomes the one depicted in Figure 4, where the Main device has been replaced by its equivalent current source model.

Doherty scheme to be analyzed before the selected to assure the maximum drain voltage swing break. In fact, each de- region i. Under these assumptions, the fulfilling of different as will be later demonstrated maximum the maximum drain efficiency condition is assured drain current values IMax,Main and IMax,Aux, respec- for the Main amplifier. As in the classical B-B DPA case, it seems to be Let us now identify with x 5 xbreak the condition for advisable to relate the output power delivered by the which the Main reaches its saturation i.

Main load curve when at the break point. Therefore, under the hypothesis that the drain voltage remains unchanged in the Doherty region, i. Thus, the parameter a also represents the selected level of the overall amplifier output back-off O.

For instance a 5 0. Analogously, the xbreak value is related to the input back-off harmonic components of the current on the input I. Thus the following two fig- Starting from eq. The relationship 11 is a tran- 2 scendental equation in the unknown xbreak, if a is fixed. Conversely, fixing the value of Icritical and con- Moreover, for the output voltage swing across the Main sequently xbreak , the value of a can be easily derived. As an example, an I. Moreover, such a difference tends to vanish if a available.

Thus it is possible to evaluate its and thus classical B-B DPA is considered see gray dashed for the overall DPA output power, dc power, and line in the plot. In the latter case, in fact, both the efficiency behaviors as functions of the normalized input and output back-off levels are the same due to input driving signal x or of the corresponding input the identical linear dependence of the fundamental power which is proportional to x2.

It follows that the current supplied by the Main de- vice to the load RL i. Thus, for the external load it follows B. On the contrary, its fundamental current component I1,Main hx could vary as a function of the input signal x if the load seen by the Main de- vice is modulated by the Auxiliary device. If it is done in the proper way, at the DPA saturation i. In fact, the fulfillment of the latter condition is not automatically obtained but passes through a proper dimensioning of the Auxiliary device.

To evaluate all the relevant output quantities of the DPA, it is possible to start from the power conser- vation property through the assumed lossless quarter- wave TL refer to Fig. Load curve for the Main a and Auxiliary b of the current at the other port I2 in the same range.

For this purpose, it is useful to analyze the situa- In Figure 9 is reported the ratio between the maxi- tion when both devices are reaching their maximum mum output current for the Auxiliary and Main de- output current IMax,Main and IMax,Aux, respectively.

Con- versely, from Figure 10, for a fixed O. RL load its maximum swing, i. This facet has to be accounted for to prevent Auxil- In fact, by replacing the expression of RL and VL iary gate breakdown. As a consequence, the drain current of the Main device loses its simple truncated sinusoidal shape, due to the fact that the class C Auxiliary amplifier has not the right pace to properly modulate the Main load condition, as it does in the B-B case.

It means that the input driving signal x is partially loosing its control on the Main device current genera- tion. Current waveform for the Main device in the increasing as a function of the increasing driving sig- Doherty region.

Sequentially, the con- sponding quantities as calculated through the Fourier analysis of 1 , as a function of x, while assuming a 5 0. Moreover, it is possible to plot the behavior of the loads seen by the Main and Auxiliary amplifiers, respectively, which are given by the ratio between the voltage and current components. When the Main device reaches the break point condition i. Afterward, the Auxiliary device has to be driven into its conduction state to achieve the IMax,Aux value, while assuring the Main device to simultaneously reach its maximum current IMax,Main.

From these considerations and assuming for sim- plicity a constant transconductance value gm,Main and gm,Aux for the Main and Auxiliary devices, respec- tively FET assumption , the following equations can be written at the saturation point x 5 1 Figure Moreover, while a 5 0.

In the example, due to the quasi-B biasing level for the Main device n 5 0. In fact, while the proper turning on condition for the Auxiliary device is assured by its Class C bias condition, a proper unbalanced input power splitting has to be considered to guarantee the expected features of the overall DPA. Therefore, to Figure On the contrary, the value of LC is auto- matically determined by 42 , when other design pa- rameters have been chosen i.

Main bias point and desired O. In particular, assuming a Tuned Load configuration and Figure Power splitting factor of Auxiliary amplifier the maximum voltage and current swings, for a LC as a function of the Main device bias point n , for generic CCA, h, the power gain can be expressed as: different O. Starting from a simplified plete DPA using the power splitting factors LAB and model of active device, used for both amplifiers, the LC previously defined.

In fact, being the DPA output analysis was carried out analyzing the DPA behavior power given by: as a function of the input driving signal. The behavioral analysis was performed dividing the DPA evolution in two parts as a function of the For the power gain it follows: input signal.

Under Choi, J. Lim, Y. Jeong, and C. Kim, these assumptions, a closed form formulation is given Doherty amplifier using load modulation and phase which allows the complete design of an AB-C Doh- compensation DGS microstrip line, Paper Presented at erty power amplifier, while highlighting all the the 36th European Microwave Conference, September , pp.

In particular, it has Jung, U.


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Use of high PAPR signals result in the power amplifier ity density function (PDF) of the complex-modulated.

TECHNICAL FIELD


Meanwhile, wireless carriers will be making much greater use of the millimetre-wave spectrum region. All these scenarios demonstrate the need for optimum efficiency in radio frequency RF power transistors and amplifiers — after all, the transmit element of a transceiver accounts for a significant chunk of the overall operating costs. In small cells and IoT kits, in particular, minimizing power consumption is essential. This is why considerable effort is being spent on increasing efficiency, both by RF equipment manufacturers and academic researchers. As a result, we see more-efficient devices, higher classes of amplifiers and the use of design techniques including digital pre-distortion, crest-factor-reduction, and envelope tracking. We will look at these in more detail shortly. First, however, there is gallium-nitride GaN technology. This product is aimed at L-band radars, such as those used in long-range surveillance, weather systems, air traffic control and anti-missile defense. The return to the Doherty architecture design is also helping improve RF power efficiency. Created in , this approach lay dormant for many years before making a comeback and is now used in the majority of base station amplifiers, thanks to recent advances in its design.

RF Module Amplifier Architectural Analysis and Simulation

doherty power amplifier basics of accounting

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A Bandwidth Enhanced Doherty Power Amplifier with a Compact Output Combiner


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Try out PMC Labs and tell us what you think. Learn More. The data presented in this study are available upon reasonable request from the corresponding author. The power amplifier PA is the most critical subsystem in terms of linearity and power efficiency. Digital predistortion DPD is commonly used to mitigate nonlinearities while the PA operates at levels close to saturation, where the device presents its highest power efficiency. Since the DPD is generally based on Volterra series models, its number of coefficients is high, producing ill-conditioned and over-fitted estimations. Recently, a plethora of techniques have been independently proposed for reducing their dimensionality.

-Interested in RF/mmWave Power Amplifier, MMIC, Doherty Power Amplifiers, RF/mmWave IEEE Transactions on Microwave Theory and Techniques June 22,

8.2 Power amplifiers (PAs): concepts and challenges

Power Amplifiers and Automatic in-Situ Identification. A new point of view is evaluated and an automatic. It is also emphasized the.

However, efficient amplifiers introduce distortions which prevent an accurate recognition of the transmitted signal. We need to find a compromise between distortion-free and a still-efficient amplifier. The Doherty configuration offers a least expensive solution for achieving this compromise. There are many excellent papers on the subject of Doherty amplifiers; however, they focus on the specifics of its implementation.

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