A 700 GHz single chip balanced SIS mixer
A 700 GHz single chip balanced SIS mixer
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700 GHz 单芯片平衡 SIS 混频器
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
S. Withington
中科院分区：
文献类型：
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作者：
P. Grimes;G. Yassin;K. Jacobs;S. Withington
我们提出了一个单芯片平衡SIS混频器的600-720 GHz频段的设计和模拟性能。混频器是基于背靠背鳍线过渡，由一对Pickett-Potter喇叭反射器（PPHR）天线馈电。由于所有的信号组合都是在微带平面电路中的芯片上进行的，所以分裂混频器块的制造非常简单。仿真结果预测，平衡混频器的性能将明显优于以前的单端鳍线SIS混频器在这个频段，混频器具有比单端SIS混频器低得多的LO功率要求。我们还展示了如何使用的700 GHz正交混合的性能可以通过使用平衡混频器在直接检测模式作为测辐射热干涉仪测量。I.平衡式SIS混频器平衡式混频器联合收割机将两个相同的单端混频器组合在一起，RF信号路径中有一个3 dB、90 kHz或180 kHz的混合接头，IF信号路径中有一个3 dB、180 kHz的混合接头（图1）。与单端混频器相比，平衡混频器具有许多优点[1]：·在通往混频器的信号路径中不需要LO耦合器或双工器·与LO耦合较弱的单端混频器相比，所需的LO功率大幅降低·LO的边带噪声被抑制图1。使用90 kHz RF混合电路的一般平衡混频器电路图。已经报道了一些平衡SIS接收器。特别是加州理工学院亚毫米波天文台目前正在将其所有低于660 GHz频段的SIS接收机升级为平衡SIS接收机[2]，许多小组正在研究用于阿尔马的平衡和图像分离混频器[3]。大多数先前报道的平衡SIS接收器已经将RF混合器实现为波导支线电路，并且使用两个单独的SIS混频器芯片。由于在这些频率下加工波导混合体的困难，这限制了在高频下平衡SIS接收器的可用性。为了避免加工复杂波导电路的问题，Kerr等人[4]，[5]已经构建并测试了在200-300 GHz频带中工作的单芯片平衡和镜像分离SIS混频器。平衡混频器的LO边带抑制程度取决于电路两臂的幅度和相位是否精确匹配。总幅度和相位不平衡由下式给出：Δ A = Δ RF + Δ G + Δ IF（1）Δ θ = 2 Δ RF + Δ IF（2）其中RF和IF指的是两个混合耦合器，Δ G是两个SIS混频元件的增益差。从（1）可以看出，通过在I-V曲线上的不同点处偏置来控制两个混频元件的相对增益，可以至少部分地消除混合器中的幅度不平衡。在相位不平衡中不能实现这种抵消。图2显示了平衡混频器中LO边带抑制与幅度和相位不平衡的关系曲线。幅度失配（dB）P在ch（de g）处为m 8 dB 10 dB 12 dB 15 dB 20 dB 25 dB 30 dB 0 1 2 3 4 5 6 0 10 20 30 40图2。作为幅度和相位不平衡函数的LO边带抑制的轮廓（根据Kerr等人[4]）。第16届空间太赫兹技术国际研讨会
We present the design and simulated performance of a single chip balanced SIS mixer for the 600-720 GHz band. The mixer is based on back-to-back finline transitions, fed by a pair of Pickett-Potter horn-reflector (PPHR) antennas. As all of the signal combination is carried out on the chip in microstrip planar circuits, the split mixer block is very simple to manufacture. The simulation results predict that the performance of the balanced mixer will be significantly better than previous single-ended finline SIS mixers in this band, and that the mixer with have much lower LO power requirements than single-ended SIS mixers. We also show how the performance of the 700 GHz quadrature hybrid used can be measured by using the balanced mixer in the direct detection mode as a bolometric interferometer. I. BALANCED SIS MIXERS BALANCED mixers combine two identical single-ended mixers with a 3 dB, 90◦ or 180◦ hybrid junction in the RF signal path and a 3 dB, 180◦hybrid in the IF signal path (fig. 1). Balanced mixers offer a number of advantages over single-ended mixers[1]: • A LO coupler or diplexer is not required in the signal path to the mixer • The required LO power is substantially reduced over a single-ended mixer with weak LO coupling • Sideband noise from the LO is rejected Fig. 1. Circuit diagram of a general balanced mixer using a 90◦ RF hybrid. A number of balanced SIS receivers have been reported. In particular the CalTech Submillimeter Observatory is currently upgrading all of it’s SIS receivers below the 660 GHz band to balanced SIS receivers[2], and a number of groups are investigating balanced and image separation mixers for use on ALMA[3]. Most previously reported balanced SIS receivers have implemented the RF hybrid as a waveguide branchline circuit, and used two separate SIS mixer chips. This has limited the availability of balanced SIS receivers at high frequencies due to the difficulty in machining waveguide hybrids at these frequencies. In an effort to avoid the problem of machining complicated waveguide circuits, Kerr et al[4], [5] have built and tested single chip balanced and image separation SIS mixers operating in the 200-300 GHz band. The degree of LO sideband rejection in a balanced mixer depends on the accurate matching of the amplitude and phase through the two arms of the circuit. The total amplitude and phase imbalances are given by ∆A = ∆ARF + ∆G + ∆AIF (1) ∆θ = 2∆θRF + ∆θIF (2) where RF and IF refer to the two hybrid couplers and ∆G is the difference in the gains of the two SIS mixing elements. From (1) it can be seen that amplitude imbalance in the hybrids can be at least partially cancelled by controlling the relative gain of the two mixing elements by biasing at different points on the I-V curve. No such cancellation can be achieved in the phase imbalance. Fig. 2 shows contours of LO sideband rejection as a function of the amplitude and phase imbalances in a balanced mixer. Amplitude mismatch (dB) P ha se m is m at ch ( de g) 8 dB 10 dB 12 dB 15 dB 20 dB 25 dB 30 dB 0 1 2 3 4 5 6 0 10 20 30 40 Fig. 2. Contours of LO sideband rejection as a function of amplitude and phase imbalance (after Kerr et al[4].). 16th International Symposium on Space Terahertz Technology