【摘要】 地基太阳射电观测系统观测信号频带较宽,覆盖十米至毫米波段.限于ADC采样率和输入带宽,通常需要通过变频电路将射电信号分段变频后再进行模数转换.由于模拟器件的差异性,多通道变频电路存在幅相不一致的情况,造成通道间幅相误差,影响接收机测量精度,对极化测量影响尤为严重.本文通过测量太阳射电观测系统中变频电路各通道之间的幅频和相频偏差,计算出每个频点的补偿系数,存入太阳射电观测系统数字接收机的FPGA中.观测时,在FPGA中将ADC输入的数据进行FFT处理,每个通道各频点数据乘以相应补偿系数,削弱通道间不一致性,提升数据质量.选取山东大学槎山太阳射电观测站150～500 MHz太阳射电观测系统进行实验验证,经补偿后通道间幅度差降低至0.5 dBm以下,一些频点差值为0 dBm,相位一致性得到显著提升.实际应用表明,本方法为提升宽频带变频电路一致性提供了解决方案,为低频对周天线阵数字波束合成、同频段多天线相干测量的多通道一致性校正提供了有效参考.更多还原

【Abstract】 The observing frequency of Ground-based Solar Radio Observation Systems(SROS) ranges from tens of MHz(10-m-wave) to tens of GHz(millimeter-wave). Due to the limitation of the ADC input bandwidth and sampling rate, the broadband solar radio signals acquired by the SROS will be segmented by mixing circuit and then processed the analog-to-digital conversion. The analog device inconsistency leads to the inconsistencies of the amplitude and phase between different channels of mixing circuits, which affects the accuracy of the receiver. The compensation coefficient of each frequency point is first calculated by measuring the deviation of the amplitude and phase between different channels, and then stored in FPGA of the receiver. The data achieved by ADC are proceed by FFT and then compensated by the compensation coefficients. The validation experiments are carried out using 150–500 MHz SROS located in Chashan Solar Radio Observatory(CSO). The amplitude difference between different channels can be as small as 0.5 dBm.The phase consistency can also be significantly improved. The practical application shows that this method can improve the consistency of the wideband mixing circuit, and can be used to correct of multi-channel consistency of the digital beam forming(DBF) for the low-frequency log-periodic antenna array and interference of the multiple antennas.更多还原