The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to cor...The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to correct it. The proposed algorithm enables clock synchronization error estimation from a pilot whose duration is only two symbol periods. The study shows that this method is simple and exact. The clock synchronization error can be corrected almost entirely.展开更多
High performance high-temperature superconducting (HTS) filters have been designed and constructed for satellite application. The filters are actually a superconducting integration of an 8-pole band-pass filter with a...High performance high-temperature superconducting (HTS) filters have been designed and constructed for satellite application. The filters are actually a superconducting integration of an 8-pole band-pass filter with an adjustable band-stop filter onto a single piece of LaAlO3 substrate (with dimension of 0.5×45×20 mm3). Typical results of the filters, i.e., Filters A (made by YBCO) & B (made by TBCCO) will be reported. The measured responses of Filter A showed excellent specifications, e.g., an insertion loss less than 0.1 dB, a return loss better than -22.5 dB in pass-band, band-edge steepness greater than 12 dB/MHz and out-of-band rejection at a certain band deeper than -110 dB. To satisfy the requirement of rocket launch and space operation, three filters of the above design have undergone mechanical environmental simulation tests for space qualification. Detailed analysis of the response curves of Filter B measured before and after the tests showed that no noticeable change in the per-formance can be found. All the filters passed the rigorous ground simulation tests, which is the first time in China for HTS devices and provided a solid foundation for satellite applications of high-temperature superconductors in the near future.展开更多
We propose a novel kind of cavity antenna based on a one-dimensional LHM-RHM cavity resonator. The resonance condition for such a cavity resonator is analytically presented. It is proved that the thickness of the ante...We propose a novel kind of cavity antenna based on a one-dimensional LHM-RHM cavity resonator. The resonance condition for such a cavity resonator is analytically presented. It is proved that the thickness of the antenna can be much smaller than the working wavelength. The simulation and experimental results for our cavity antenna agree with the theoretical prediction with relatively high directivity.展开更多
In this paper, an iterative carrier recovery algorithm of Gaussian filtered minimum shift keying （GMSK） in burst-mode was designed. The data utilization rate and precision of the traditional demodulation method for ...In this paper, an iterative carrier recovery algorithm of Gaussian filtered minimum shift keying （GMSK） in burst-mode was designed. The data utilization rate and precision of the traditional demodulation method for recovering carrier signal in burst data packet with limited-length is poor. In order to solve this problem, this paper proposed an iterative carrier recovery algorithm. This algorithm can improve the estimated precision of carrier recovery and data utilization rate of burst data packet in a large extent by performing multiple forward and backward iterations. And the algorithm can be implemented in Simulink environment. As the communication mode of automatic identification system （AIS） is abrupt, the algorithm is especially suitable for satellite-based AIS.展开更多
文摘The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to correct it. The proposed algorithm enables clock synchronization error estimation from a pilot whose duration is only two symbol periods. The study shows that this method is simple and exact. The clock synchronization error can be corrected almost entirely.
基金the Chinese Academy of Sciences (KJCX2-SW-W01)Beijing Mu-nicipal Science & Technology Commission (H010410050111)+1 种基金the Ministry of Sci-ence and Technology of China (2002AA306181)the National Natural Science Foundation of China (Grant No.10474127)
文摘High performance high-temperature superconducting (HTS) filters have been designed and constructed for satellite application. The filters are actually a superconducting integration of an 8-pole band-pass filter with an adjustable band-stop filter onto a single piece of LaAlO3 substrate (with dimension of 0.5×45×20 mm3). Typical results of the filters, i.e., Filters A (made by YBCO) & B (made by TBCCO) will be reported. The measured responses of Filter A showed excellent specifications, e.g., an insertion loss less than 0.1 dB, a return loss better than -22.5 dB in pass-band, band-edge steepness greater than 12 dB/MHz and out-of-band rejection at a certain band deeper than -110 dB. To satisfy the requirement of rocket launch and space operation, three filters of the above design have undergone mechanical environmental simulation tests for space qualification. Detailed analysis of the response curves of Filter B measured before and after the tests showed that no noticeable change in the per-formance can be found. All the filters passed the rigorous ground simulation tests, which is the first time in China for HTS devices and provided a solid foundation for satellite applications of high-temperature superconductors in the near future.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60531020, 60671003 and 60701007, the National High-Tech Research and Development Program of China under Grant No 2009AA01Z227, the New Century Excellent Talent Project of the Ministry of Education of China under Grant No NCET-07-0750, the Natural Science Foundation of Zhejiang Province under Grant No Y1080715, the Doctoral Program of Higher Education in China under Grant No 20070335120, and the National Key Laboratory Foundation under Grant Nos 9140C5304020901 and 9140C5304020704.
文摘We propose a novel kind of cavity antenna based on a one-dimensional LHM-RHM cavity resonator. The resonance condition for such a cavity resonator is analytically presented. It is proved that the thickness of the antenna can be much smaller than the working wavelength. The simulation and experimental results for our cavity antenna agree with the theoretical prediction with relatively high directivity.
文摘In this paper, an iterative carrier recovery algorithm of Gaussian filtered minimum shift keying （GMSK） in burst-mode was designed. The data utilization rate and precision of the traditional demodulation method for recovering carrier signal in burst data packet with limited-length is poor. In order to solve this problem, this paper proposed an iterative carrier recovery algorithm. This algorithm can improve the estimated precision of carrier recovery and data utilization rate of burst data packet in a large extent by performing multiple forward and backward iterations. And the algorithm can be implemented in Simulink environment. As the communication mode of automatic identification system （AIS） is abrupt, the algorithm is especially suitable for satellite-based AIS.
