Research And Design Of Solid State RF Power Source

Solid-state power amplifiers have many advantages over vacuum tubes, including: availability, reliability, graceful degradation and ease of maintenance. Recent years, it has become more common to use solid-state RF power amplifiers providing the accelerators with power.Shanghai Soft X-ray Free Electron Laser(SXFEL), which acts as the 4th generation light source, can produce light with peak brightness 109 times of synchrotron radiation. SXFEL provides science community with unprecedented detecting ability. Free Electron Laser is a new form of light source which is generated by using a high-quality relativistic electron beam as the lasing medium. With periodic variation in the magnetic field of the undulator, electromagnetic radiation is amplified by stimulated emission, producing a very bright beam of light. The stability of the magnitude and phase of RF power source is important for the FEL to attain high brightness, a short pulse and good coherency.The general design methods and the parameter measuring processes of a 1 k W solid-state Radio Frequency(RF) power amplifier at 2856 MHz are presented. The power amplifier is manufactured for the Soft X-ray Free Electron Laser facility, Three-stage amplification process with a 4-way combination are used. A RF switch module is integrated in the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal, also renders the pulse width adjustable. The measured power gain is 57.7 d B at 60 d Bm output. The RF phase noise, which is measured by the low level RF(LLRF) system, is less than 0.015 degree(RMS), while the pulse frontier jitter is less than 5ns.this paper analyzes the reason of phase jitter in solid-state power amplifier design. This solid-state power source design uses modular design method. A solid-state power amplifier module designs with computer simulation makes it achieved the requirements of output power. Base on it, the design removes stray parameter and reduces the influences of electromagnetic coupling noise for the low phase jitter output. Meanwhile, using protect circuit of power source and optocoupler to reduce the influences of other modules on phase jitter. We did complete parameter measurement experiments after the solid-state power source design. Using spectrometer and power meter to measure the spectra curve and output power of power amplifier. We also used the LLRF system which developed by Shanghai institute of applied physics to measured phase jitter and flat-topped waveform of the solid-state power source. These experiments showed that all design requirements were met.This paper also introduces a design process of high linear solid-state power amplifier module. The module is a part of a 100 kw output solid-state power source which provides power to the energy poor linear accelerator. The design of matching network adopts the method of combining transmission lines and lumped elements. The design process was simulated and optimized by ADS program to achieve the design requirements. A compact structure was adopted in the input impedance design, reducing the circuit size. A ladder structure impedance matching network was used to effectively suppress the higher harmonic components of output power, improving the performance of amplifier. According to the simulation results, this amplifier design has many advantages, such as having a compact structure, a good performance of higher harmonics suppression, and a high power output.At the end of this paper, the design process of X band power amplifier is introduced, and we discussed the difficulties in the design of X band solid state power amplifier. We studied how the wire bonding effects on amplifier. Then we proposed a way that using gold compensation circuit to eliminating the wire bonding effect on the amplifier circuit.