RIA: A New Approach to Microwave/Millimeter-Wave Transmitters

在微波和毫米波范围内的雷达应用需要紧凑、高功率的源。在这个频率范围内，固态器件的输出功率水平是有限的。在这项研究启动基金中探索的一个可能的解决方案是将数百个有源设备的输出连贯地组合在一起，这些有源设备加载一个周期等于自由空间波长的一小部分的二维金属网格。这个有源表面既是天线又是信号源。这些器件可以是mesfet，以门反馈的方式布置。这种类型的振荡器有一个宽的频率调谐范围，因为在大多数应用中需要。振荡的活动表面背面有一个调谐镜，具有电可变反射系数。这面镜子是另一个装有变容二极管的金属网格。二极管的电容，因此该调谐表面的反射系数，是偏置相关的。镜面向振荡器表面提供正反馈，这是设备锁定到单一模式所必需的。例如，在雷达中，信号通常以脉冲形式传输。在发射机本身不能以高速率开关和关闭的情况下，可以使用开关活性表面。这个表面由一个装有引脚二极管的栅格组成，它用电开关从振荡器栅格传输的波。该系统结构紧凑，重量轻，因为它由一堆装载固态器件的平面电介质组成，不需要大的电源。它是通用的，例如，与振荡器平行放置的肖特基二极管的另一个有源表面可以具有可变相移，用于光束转向或光束形成应用，或者可以用作乘法器。此外，平面结构适合于晶圆级或模块化集成。

There is a need for compact, high-power sources for radar applications in the microwave and millimeter- wave range. The output power levels of solid-state devices in this frequency range are limited. A possible solution to be explored in this Research Initiation Grant is to coherently combine the outputs of hundreds of active devices that load a two- dimensional metal grid with a period equal to a fraction of a free-space wavelength. This active surface is an antenna as well as source. The devices can be MESFETs arranged in a gate-feedback configuration. This type of oscillator has a wide frequency tuning range, as is required in most applications. The oscillating active surface is backed with a tuning mirror that has an electrically variable reflection coefficient. This mirror is another metal grid loaded with varactor diodes. The capacitance of the diodes, and therefore the reflection coefficient of this tuning surface, is bias dependant. The mirror provides positive feedback to the oscillator surface, which is necessary for the devices to lock to a single mode. In a radar, for example, the signal is usually transmitted in pulses. In cases when the transmitter itself cannot be switched on and off at a high rate, a switching active surface can be used. This surface consists of a grid loaded with pin diodes, and it electrically switches the wave transmitted from the oscillator grid. This system is compact and light weight, since it consists of a stack of planar dielectrics loaded with solid-state devices that do not require large power supplies. It is versatile, for example, another active surface of Schottky diodes placed in parallel with the oscillator could have a variable phase shift for beam steering or beam forming applications, or can be used as a multiplier. In addition, the planar structure is suitable for wafer- scale or modular integration.