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Input backoff power amplifier

System performance depends on input power back-off IBO and SEFDM parameters, such as modulation scheme, frequency spacing between subcarriers and total number of subcarriers. IBO corresponding to minimum TD is obtained. Unable to display preview. Download preview PDF. Skip to main content.


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(SD2019-364) Method For Enhancing Power Amplifier Efficiency And Linearity


The IER was generated using the peaking amplifier with the help of a desired impedance transformation in the low-power region to enhance the back-off efficiency of the carrier amplifier. To convert the impedances properly, both in the low-power region and at saturation, a two-impedance matching method was employed to design the output matching networks. For verification, a symmetric DPA with large back-off power range over 2. The linearity improvement of the DPA for multistandard wireless communication system was also verified with a dual-band modulated signal.

In future wireless communication systems, such as the 5th generation of mobile communication network 5G , the ever increasing demand for high transmission data rate results in the employment of wideband and multiband modulated signals characterized by high peak-to-average power ratios PAPRs.

To efficiently amplify these signals at back-off power BOP range, the Doherty power amplifier DPA has garnered great research attention because of its significant efficiency enhancement and ease of configuration [ 1 — 6 ].

These two kinds of DPAs utilize excessive modulation current of the peaking amplifier to achieve enlarged load span of the carrier amplifier for extended BOP range, leading to tradeoffs between design complexity, cost, and power utilization factor. However, these approaches might suffer from complicated design methodology. Recently, the effect of the output impedance of the peaking stage has been investigated to extend the high-efficiency power range or bandwidth [ 19 — 21 ] in DPA designs.

In [ 21 ], we have proposed a novel method to extend the bandwidth of the DPA based on integrated compensating reactance, which was chosen near the open-circuit area in Smith chart. However, after further analysis, it is found that a reactance near the short-circuit point can also be used to enhance the back-off efficiency and thus extend the BOP range. In this paper, after analyzing the effect of a reactive load at the combining point on the back-off efficiency of the carrier amplifier, a new symmetric DPA with large BOP range based on enhancing reactance integrated in the peaking amplifier is proposed.

This integrated enhancing reactance IER was obtained by using a two-impedance matching method to extend the BOP range. Unlike conventional DPA, the output impedance of the peaking amplifier in the proposed design has a lower reactance value for efficiency enhancement when the peaking amplifier is in off-state.

For verification, a 2. Experimental results of the output power and efficiency as well as the linearization results are also presented. The simplified schematic of the proposed DPA is shown in Figure 1 , which comprises the carrier and peaking amplifiers, an input power divider, and a common load.

In Figure 1 , , , , and represent the carrier and peaking load impedances at the device output and at the combining point when the DPA is at saturation, while , , , and are the output and load impedances before the peaking amplifier turns on, respectively.

At saturation, the IER would not introduce undesirable effect on load modulation of the DPA when both carrier and peaking amplifiers turn on. The design procedure of the proposed DPA is presented as follows. To analyze the effect of the IER on the back-off efficiency of the carrier amplifier, the carrier output matching network OMN should be designed firstly. During the Doherty operation, the carrier OMNs should convert the load impedances to the desired values to obtain proper Doherty behavior.

To evaluate performance over wide operation band, the simulated impedances between 2. In the proposed DPA, a shunted reactance at the combining point was employed to achieve high efficiency of the carrier amplifier in the low-power region.

To determine the value of this shunted reactance , using the schematic in Figure 4 , the effect of the reactance on the carrier back-off efficiency was analyzed. When compared with the case without the shunted reactance, significant efficiency enhancement can be observed in the low-power region, which means larger BOP range can be achieved. However, according to Doherty operation principle, if an additional shunted reactance at the combining point is employed as the enhancing reactance for efficiency improvement, the load modulation at saturation will be improper, leading to unavoidable degradation of the output power and efficiency.

To solve this problem, in this paper, the output impedance of the peaking amplifier in off-state was employed to generate this enhancing reactance, which is integrated in the peaking amplifier output, that is, the IER. It should be mentioned that, unlike conventional DPA, the peaking output impedance in the proposed DPA is not an open circuit but a reactance in the low-power region.

To obtain desired IER, a two-impedance matching method was employed to design the OMN of the peaking amplifier, as introduced in the following section. The OMN of the peaking amplifier should satisfy the desired impedance transformation, as illustrated in Figure 6.

The peaking OMN should convert the output impedance to desired value of to generate the IER at BOP, while transforming to at saturation, which can be achieved using the following design method. Considering the peaking OMN in Figure 6 , the impedances at BOP region and at saturation can be expressed as By means of 1 and 3 , the following expressions are obtained:.

Then, the OMN can be designed accordingly. In the peaking OMN design, the optimum load impedance at 2. To determine the output impedance when the peaking amplifier is in off-state, the transistor model was simulated without output matching network under small input signal stimulation in ADS large signal S -parameter simulation. According to Section 2.

The load impedances at saturation power and the peaking output impedances in class-C operation are also depicted. The results show that, using the two-point matching technique, the designed OMN can satisfy the impedance transformation of the peaking amplifier.

To verify the proposed method, a 2. Both the carrier and peaking IMNs are designed by using stepped-impedance matching network theory to cover the required frequency band, as shown in Figure In Figure 11 , the simulated load impedance traces of the carrier and peaking device are depicted.

The load impedances of both carrier and peaking devices at saturation thus still satisfy the desired load impedance shown in Figures 2 and 8. In Figure 12 , the simulated drain efficiencies of the proposed and conventional DPAs are depicted. To analyze the influence of this IER on the overall performance of the DPA, the power leakages of the carrier amplifier at the combining point were simulated, as shown in Figure The efficiency enhancement confirms that expected BOP range extension can be achieved using the proposed IER, while the output power performance is similar to conventional design.

To evaluate the efficiency over wide frequency band, the simulated drain efficiencies of the proposed DPA at 2. In addition, the efficiency plateau in large BOP range, which verifies the high-efficiency range extension based on IER, can also be observed. The measurement results using continuous wave signals and modulated signals are given as follows.

Figure 16 shows measured drain efficiencies and gains versus output powers at 2. The peak output power ranges from 44 to One can observe that the drain efficiency can maintain appropriate consistency over large BOP range, especially at the frequency band of 2. Figure 17 depicts the measured average efficiencies and adjacent channel leakage ratios ACLRs versus the average output powers.

To validate the linearity improvement over the whole frequency band, the DPD linearization was implemented at the frequencies of 2. The two dimensional decomposed vector rotation-based model was used for linearization [ 23 , 24 ].

The linearization results show that good linearity and efficiency performance of the designed DPA can be achieved for multistandard wireless communication systems. Table 1 shows the performance comparison with published DPAs. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors. Read the winning articles. Journal overview. Special Issues. Academic Editor: Shichang Chen. Received 21 Dec Accepted 11 Mar Published 15 Apr Introduction In future wireless communication systems, such as the 5th generation of mobile communication network 5G , the ever increasing demand for high transmission data rate results in the employment of wideband and multiband modulated signals characterized by high peak-to-average power ratios PAPRs.

Figure 1. Figure 2. Designed carrier OMNs and the simulated impedances over the frequency band of 2. Figure 3. Simulated efficiency of the carrier amplifier versus output powers under different loads at 2. Figure 4. Carrier amplifier with a shunted reactance at the combining point.

Figure 5. Figure 6. Figure 7. Graphical illustration of the two-impedance matching technique for the peaking OMN. Figure 8. Designed peaking OMN and simulated impedances over the frequency band of 2. Figure 9. Figure Simulated load traces of the carrier and peaking device in the Doherty operation. Simulated drain efficiencies of the proposed and conventional DPAs as a function of output power at 2.

Simulated power leakages of the carrier amplifier in proposed and conventional DPAs. Simulated drain efficiencies of the proposed DPA at the frequencies of 2. Measured drain efficiency and gain versus output power at different frequencies.

Type Freq. GHz Effi. Table 1. Measured power spectral density with the dual-band modulated signal before and after DPD. References A. Grebennikov and S. Rawat and F. Chen and Q. Mohamed, S. Boumaiza, and R. Lee, J. Son, and B.


Design and Characterization of a Multipurpose PCS Class A Amplifier/April 97

Both the main and the peaking amplifiers are designed and optimized using equivalent lumped parameters and power combiner models. The novel design consumes a DC power of 2. The simulation results show a very good capability of drive current, high gain, and very low input and output insertion losses. The precise active load-pull controlling of fundamental and harmonic terminations of the DPA is simulated and analyzed, including the parasitics of the transistors. The measurements of the DPA with the phase difference, input power ratio adjustment, and envelope tracking of the auxiliary PA are discussed in detail in order to achieve a competitive performance. In brief, a dual-band doherty power amplifier employing reactance compensation with gallium nitride high-electron-mobility transistor technology is discussed. This design is developed for long-term evolution LTE frequency operation, particularly for the application of two-way radio to improve the efficiency at the back-off point from saturation output power for selected dual frequencies in the LTE bandwidth.

As the input power increases the gain of the amplifier is gradually to maintain linear amplification is called backoff, expressed in dB.

A 90-W peak power GaN outphasing amplifier with optimum input signal conditioning


Programming commands. Many compression parameters to choose from, including gain, input power at compression, output power at compression, input match, and compression level. Compression Analysis allows traditional power sweep view at a selected frequency. Receiver Leveling provides continuous source power accuracy. Option S9xA software option only must be enabled. Unratioed receiver measurements A, B, R. Narrowband Pulse measurements using the Integrated Pulse App.

A Doherty Power Amplifier with Large Back-Off Power Range Using Integrated Enhancing Reactance

input backoff power amplifier

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Simulate and Verify Power Amplifier Backoff


Continue with email. When a number of carriers are present simultaneously in a TWTA, the operating point must be backed off to a linear portion of the transfer characteristic to reduce the effects of intermodulation distortion. Such multiple carrier operation occurs with frequency division multiple access FDMA. The point to be made here is that backoff BO must be allowed for in the link budget calculations. If the saturation flux density for single-carrier operation is known.

Measurement and Control of RF Power (Part II)

Metrics details. Orthogonal frequency division multiplexing OFDM has been adopted in many modern communication systems due to its robustness against frequency-selective fading channels as well as its near-rectangular spectrum that can achieve high spectral efficiency. However, its major drawback is the resulting signal with high peak-to-average power ratio PAPR , which causes severe nonlinear distortion at the power amplifier PA unless input backoff is chosen sufficiently large. The effect of the nonlinear distortion is two-fold: out-of-band radiation and signal quality degradation. The former causes adjacent channel interference and thus degrades the bandwidth efficiency. The latter affects the system level performance and is often measured by the error vector magnitude EVM.

tion power amplifiers simultaneously at maximum and backoff output power levels. To this end, the present pow- er amplifier comprises two.

RF power amplifier

A three stages cascaded PA is designed which observes a high power gain. The final stage device dimension has been selected diligently in order to deliver a high output power. The inter-stage match between the driver and main stage has been designed to provide maximum power transfer. With the cascaded topology, a maximum

FIELD OF THE INVENTION

RELATED VIDEO: Fundamentals of RF Power Amplifier Linearizers (RFPAL)

James Crescenzi, Jr. Strifler Watkins-Johnson Co. The rapid expansion of personal communications service PCS base stations and services has resulted in an increased demand for linear power amplifiers in the 1. Typically, single-channel base station PCS amplifiers produce 2 to 50 W of average output power.

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Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Optimal input power back-off with nonlinear power amplifier for electric power systems Abstract: The nonlinear distortion from power amplifier PA distorts the signal and causes significant impact on the symbol-error-rate SER performance for the electric-power-systems EPS communications. This paper proposes a calculation of the optimal input power back-off IBO to resist PA nonlinearity, as well as guarantee an appropriate signal-to-noise ratio SNR , by minimizing the mean square error MSE between the received symbols and the standard constellation points. Simulations indicate that the optimal IBO is variable and increases as the noise level grows.

The flux density required in the receiving antenna to produce saturation of the TWTA is termed the saturation flux density. Amplifier back off To reduce inter-modulation distortion, the operating point of the TWT must be shifted to the linear portion of the curve from nonlinear portion, the reduction in input power being referred as input back off. When multiple carriers present, the power around saturation, for any carrier, is somewhat less than the achieved with single carrier operation. Input back-off The input back-off is the difference in decibels between the carrier input at the operating point, and saturation input that would be required for single carrier operation.




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