A New Two-Branch Amplification Architecture and its Application with Various Modulated Signals

This paper proposes a new two-branch amplification architecture that combines baseband signal decomposition with RF front-end optimization. In the proposed architecture, the filtered modulated signals are separated into two components that are then amplified independently and combined to regenerate an amplified version of the original signal. A branch with an efficient amplifier transmits a low-varying envelope signal that contains the main part of the information. Another branch amplifies the residual portion of the signal. The baseband decomposition and parameters of the RF part are optimized to find the configuration that gives the best power efficiency and linearity. For M-ary quadrature amplitude modulation （M-QAM） signals, this technique is limited in terms of power efficiency. However, for filtered continuous phase modulation （CPM） signals, especially for minimum shift keying （MSK） and Gaussian MSK （GMSK） signals, high power efficiency can be achieved with no significant impact on the overall linearity. The results show that this technique gives better performance than the single-ended ctass-B amplifier.

A wideband large dynamic range and high linearity RF front-end for U-band mobile DTV

A wideband large dynamic range and high linearity U-band RF front-end for mobile DTV is introduced, and includes a noise-cancelling low-noise amplifier （LNA）, an RF programmable gain amplifier （RFPGA） and a current communicating passive mixer. The noise/distortion cancelling structure and RC post-distortion compensation are employed to improve the linearity of the LNA. An RFPGA with five stages provides large dynamic range and fine gain resolution. A simple resistor voltage network in the passive mixer decreases the gate bias voltage of the mixing transistor, and optimum linearity and symmetrical mixing is obtained at the same time. The RF front-end is implemented in a 0.25 #m CMOS process. Tests show that it achieves an IIP3 （third-order intercept point） of -17 dBm, a conversion gain of 39 dB, and a noise figure of 5.8 dB. The RFPGA achieves a dynamic range of-36.2 to 23.5 dB with a resolution of 0.32 dB.

Higher harmonic voltage analysis of magnetic-alloy cavity for CSNS/RCS upgrade project

Background A rapid cycling synchrotron(RCS)in China Spallation Neutron Source(CSNS)would be upgraded,and the proton beam power will reach 200-500 kW.Three RF cavities loaded by magnetic-alloy(MA)material will be added in RCS tunnel to form a dual-harmonic RF system with eight ferrite-loaded cavities in RCS.The bandwidth of the MA cavity is wide because of its intrinsic Q value of less than 1.Higher harmonics can be excited in MA cavities,because the RF power is directly fed into the MA cavity from the final stage of the RF power amplifier.The distortion of voltage in the cavity gap caused by higher harmonics may deteriorate the beam quality.The influence of the higher harmonics to beam needs to be evaluated and the amplitude of higher harmonics should to be suppressed.Methods We built a mathematical model with two functions based on the RF bucket acceptance and bunch factor to evalu-ate this influence.Groups of harmful amplitudes and phases of higher harmonics were found according to the mathematical model by using multi-objective particle swarm optimization(MOPSO).Conclusion The dual-harmonic RF system with higher harmonics in CSNS/RCS and a suitable harmonic suppression for MA cavities was discussed according to the results of MOPSO and the beam dynamics simulations.