Universal FRFT-based algorithm for parameter estimation of chirp signals

The realization of the parameter estimation of chirp signals using the fractional Fourier transform （FRFT） is based on the assumption that the sampling duration of practical observed signals would be equal to the time duration of chirp signals contained in the former. However, in many actual circumstances, this assumption seems unreasonable. On the basis of analyzing the practical signal form, this paper derives the estimation error of the existing parameter estimation method and then proposes a novel and universal parameter estimation algorithm. Furthermore, the proposed algorithm is developed which allows the estimation of the practical observed Gaussian windowed chirp signal. Simulation results show that the new algorithm works well.

TCP flow identification by sequence and acknowledgement number

To reduce the TCP flow processing cost, some bit patterns selected from the TCP/IP packet can be used as TCP flow identification. Based on the entropy and randomness analysis of the distribution of sequence number （SN） and acknowledgement number （AN） in the first packet of a TCP flow, this paper proposes a new uniform TCP flow identification by sequence and acknowledgement number （FIDSAN） to the heavy-tailed IP or TCP traffic. The experimental results suggest that some bits in the TCP sequence number and acknowledgment number can be selected out as flow ID with acceptable confliction probability. The bit length of flow ID selected under given confliction probability can be conducted from an equation deduced from the observing window and flow ID range. FIDSAN has low computation cost in the comparison with the traditional methods, such as 5-tuple, CRC, and Checksum etc.

Arcing-based protection system for the klystron output window of the BEPCII Linac

Purpose The Beijing Electron–Positron Collider II(BEPCII)Linac is powered by 20 klystrons,and the output windows of each klystron need to be protected from being broken,which are currently protected by a system based on reflected radiofrequency(RF)power and vacuum levels.The primary weak point of reflection-based protection is the difficulty of accurately measuring the value caused by an uneven waveform.Moreover,vacuum protection is restricted by the long response time,which results in delayed protection.Both of the weak points may damage the output window of the klystron.An arcing-based protection system is then introduced into the BEPCII Linac,considering the constant presence of light during arcing and the experiences of other laboratories and colleagues in the RF group.Methods The system development mainly consists of the design and test of the E-bend waveguide observation window,selection of the arcing detection module,offline joint test,system assembling and online operation.Results The system was assembled with a new klystron at the K6 position on the summer of 2018.During the following annual operation year,the light signal was captured,and the interlock was successfully realized.Conclusion The arcing-based protection system assembled online was found to work well.Moreover,the light signal was successfully captured,and the interlock function worked fine.The system is planned to be applied in other klystron locations in the future.