A Millimeter-Wave Non-Magnetic Passive SOI CMOS Circulator Based on Spatio-Temporal Conductivity Modulation
A Millimeter-Wave Non-Magnetic Passive SOI CMOS Circulator Based on Spatio-Temporal Conductivity Modulation
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DOI：
10.1109/jssc.2017.2759422
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发表时间：
2017-12-01
影响因子：
5.4
通讯作者：
Krishnaswamy, Harish
中科院分区：
文献类型：
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作者：
Dinc, Tolga;Nagulu, Aravind;Krishnaswamy, Harish
由具有对称介电常数和磁导率张量的常规材料构造的线性时不变无源电路和系统是互逆的。打破洛伦兹互易性使得能够实现非互易组件，诸如回转器、隔离器和循环器，其在许多无线通信系统中找到应用。非互易组件传统上使用铁氧体材料来实现，铁氧体材料在施加外部磁场偏置的情况下表现出法拉第效应。然而，铁氧体材料不能集成到CMOS制造工艺中，并且需要外部偏置磁体，因此体积大且昂贵。最近，人们对使用时间调制实现非磁性非互易组件产生了重大的研究兴趣，包括在45 nm SOI CMOS中完全集成的25 GHz环行器，首次在毫米波下展示了硅上的无磁无源非互易性。本文对毫米波环行器进行了详细的时域和频域分析。毫米波非互易操作通过时空电导率调制的概念实现，其在理论上无限带宽（BW）上实现宽带非互易回转器功能。与基于N通道滤波器的现有方法相比，时空电导率调制仅需要四相50%占空比时钟，频率显著低于工作频率，从而能够扩展到毫米波。25 GHz环行器实现了最小发射机（TX）到天线（ANT）/ANT到接收机（RX）插入损耗分别为3.3 dB/3.2 dB，1 dB带宽为4.6 GHz。在相同带宽下，TX到RX隔离为18.3-21.2 dB（受测量设置限制）。环行器IC占据1.2 mm x 1.8 mm（lambda/8 x lambda/6）的面积。时空电导率调制概念在频率上是容易可缩放的，并且可以是更高毫米波（例如，77 GHz）环行器以及光隔离器。
Linear, time-invariant, passive circuits and systems constructed from conventional materials with symmetric permittivity and permeability tensors are reciprocal. Breaking Lorentz reciprocity enables the implementation of non-reciprocal components, such as gyrators, isolators, and circulators, which find application in numerous wireless communication systems. Non-reciprocal components are traditionally implemented using ferrite materials, which exhibit the Faraday effect under the application of an external magnetic field bias. However, ferrite materials cannot be integrated into CMOS fabrication processes and require an external biasing magnet, and hence are bulky and expensive. Recently, there has been significant research interest in the implementation of non-magnetic non-reciprocal components using temporal modulation, including a fully integrated 25-GHz circulator in a 45-nm SOI CMOS, demonstrating magnetic-free passive non-reciprocity on silicon at millimeter waves for the first time. This paper presents a detailed analysis of the millimeter-wave circulator in both time and frequency domains. Millimeter-wave non-reciprocal operation is enabled by the concept of spatio-temporal conductivity modulation, which achieves broadband non-reciprocal gyrator functionality over theoretically infinite bandwidth (BW). When compared with prior approaches based on N-path filters, spatio-temporal conductivity modulation requires only four-phase 50% duty-cycle clocking at frequencies significantly lower than the operation frequency, enabling scaling to millimeter waves. The 25-GHz circulator achieves minimum transmitter (TX)-to-antenna (ANT)/ANT-to-receiver (RX) insertion losses of 3.3 dB/3.2 dB, respectively, with a 1-dB BW of 4.6 GHz. TX-to-RX isolation is 18.3-21.2 dB (limited by the measurement setup) over the same BW. The circulator IC occupies an area of 1.2 mm x 1.8 mm (lambda/8 x lambda/6). The spatio-temporal conductivity modulation concept is readily scalable across frequency and can be an enabler for higher millimeter-wave (e.g., 77 GHz) circulators as well as optical isolators.