Non-Foster Loaded Parasitic Array for Broadband Steerable Patterns
Non-Foster Loaded Parasitic Array for Broadband Steerable Patterns
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DOI：
10.1109/tap.2014.2361903
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发表时间：
2014-10
影响因子：
5.7
通讯作者：
M. Jacob;J. Long;D. Sievenpiper
中科院分区：
文献类型：
--
作者：
M. Jacob;J. Long;D. Sievenpiper
寄生阵列可以使用寄生元件上的可调电抗负载来产生可控制的图案，以提供散射辐射所需的相位。然而，耦合到寄生元件并被附加负载反射的辐射具有频率相关的相位延迟，导致波束/零斜视效应和有限的瞬时无斜视带宽。在本文中，我们介绍了一种利用非福斯特寄生负载消除这种频率依赖性的技术，该负载的反射相位具有正的相位色散斜率，可以抵消与传输延迟相关的负的相位色散斜率。此外，通过调整非福斯特负载，我们可以调整总的散射相位，以获得可操纵的图案。可调非福斯特阻抗可以使用基于晶体管的负阻抗转换器(NIC)电路来设计。针对分立器件网卡的工作频率，设计了一种二元寄生阵列。利用阵列理论和仿真计算了在不同方位角下获得宽带或无斜视零点所需的非福斯特阻抗。制作了一个产生宽边宽带零点非福斯特阻抗的网卡，并将其连接到寄生天线上。仿真和测量结果表明，从180-350 MHz的宽带均匀零点提供了大约两倍于无源寄生负载的零点带宽。在调谐时，NIC的稳定性约束限制了在某些方位角上的零位转向。通过对寄生天线和网卡的合理设计，我们可以利用非福斯特寄生阵列获得更宽的带宽和可控的方向图。
Parasitic arrays can generate steerable patterns using tunable reactive loads at the parasitic elements to provide the required phase for the scattered radiation. However, the radiation that is coupled to the parasitic elements and reflected by the attached loads has a frequency dependent phase delay, leading to a beam/null squint effect and a limited instantaneous squint-free bandwidth. In this paper, we introduce a technique for eliminating this frequency dependence using non-Foster parasitic loads, whose reflection phase has a positive phase dispersion slope that can cancel the negative phase dispersion slope associated with propagation delays. Further, by tuning the non-Foster load, we can tune the total scattered phase to achieve steerable patterns. Tunable non-Foster impedances can be designed using transistor-based negative impedance convertor (NIC) circuits. A two element parasitic array was designed for the frequencies of operation of discrete device NICs. Non-Foster impedances required for obtaining broadband or squint-free nulls at different azimuth angles were calculated using array theory and simulations. An NIC that generated the non-Foster impedance for a broadside broadband null was fabricated and attached to the parasitic antenna. Simulation and measurement results showed broadband uniform nulls from 180-350 MHz, providing about twice the null bandwidth of a passive parasitic load. Null steering across some angles of the azimuth was restricted by the stability constraints of the NIC while being tuned. With a judicious design of the parasitic antenna and the NIC, we can achieve broader bandwidths and steerable patterns with non-Foster parasitic arrays.