A Multi-Beam 2SB Receiver for Millimeter-Wave Radio Astronomy
A Multi-Beam 2SB Receiver for Millimeter-Wave Radio Astronomy
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发表时间：
2009
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通讯作者：
W. Shan;Joseph Yang;S. Shi;Q. Yao;Y. Zuo;Shujun Chen;A. Cao;Zhenhui Lin;W. Duan;J. Zhong;Zhen Li;Louis Liu
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作者：
W. Shan;Joseph Yang;S. Shi;Q. Yao;Y. Zuo;Shujun Chen;A. Cao;Zhenhui Lin;W. Duan;J. Zhong;Zhen Li;Louis Liu
目前正在为德令哈毫米波望远镜研制3x3多波束接收机，该望远镜是中国毫米波射电观测的主要开放设施，旨在大幅提高毫米波测线测绘能力。接收机采用灵敏的SIS混频器，工作在85 - 116GHz的频率范围内。采用边带分离（2SB）方案，以实现高精度的校准过程，并降低空闲边带噪声，特别是在某些季节大气透明度不好时。SIS混频器的设计具有近乎恒定的动态电阻和均匀的转换增益，可实现稳定的偏置，并可直接连接SIS混频器和低温低噪声放大器，而无需IF隔离器。此外，低噪声和稳定的数字SIS偏置电路已被设计成有效地操作SIS混频器。九个2SB混频器由单个LO信号源驱动。由6个分支线定向耦合器实现的两级级联功率分配器在路径之间以良好的隔离度分配LO信号。LO由频率合成器产生，随后是一个分频器-乘法器模块，在整个RF频带内提供不小于10 mW的输出功率。中频波段中心频率为2.64GHz，带宽为1GHz，可以同时观测CO、CO和CO三条谱线，是探测大范围气体密度的有效观测模式。9个像素产生18个独立的IF输出。该系统具有200MHz-1GHz可重构带宽和16384通道的数字FFT谱仪，与现有的模拟AOS系统相比，具有明显的优点，可构成一个紧凑可靠的焦阵接收机后端系统。整个多波束接收系统将于2009年底在实验室进行演示。
A 3x3 multi-beam receiver is being developed for Delingha millimeter telescope, the major open facility for millimeter-wave radio observation in China, aiming to significantly enhance the mapping capability in millimeter-wave line observation. The receiver employs sensitive SIS mixers, working over 85-116GHz frequency range. Sideband separation (2SB) scheme is adopted to enable high-precision calibration procedure and to reduce the idle sideband noise especially when the atmosphere transparency is not good in some seasons. The SIS mixers were designed to have nearly constant dynamic resistance and uniform conversion gain, allowing stable bias and direct connection of the SIS mixer and the cryogenic low noise amplifier without an IF isolator. Besides, low noise and stable digital SIS bias circuit has been designed to operate the SIS mixer efficiently. The nine 2SB mixers are driven by a single LO signal source. Two stages of cascaded power dividers realized by 6-branch line directional couplers distribute the LO signal with good isolation between paths. The LO is generated by a frequency synthesizer followed by an amplifier-multiplier module providing output put power not less than 10mW across the RF band. The IF band is centered at 2.64GHz and bandwidth 1GHz allowing simultaneously observing three CO lines (CO, CO and CO), which has been proved to be an efficient observation mode in probing a broad range of gas density. The nine pixels yield 18 independent IF outputs. Each of them is processed by a digital FFT spectrometer with 200MHz-1GHz reconfigurable bandwidth and 16384 channels, which has obvious merits over the present analog AOS system to form a compact and reliable backend system for focal array receiver. The whole multi-beam receiver system will be demonstrated in lab by the end of 2009.