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

在微波和毫米波范围内的雷达应用中需要紧凑型、高功率源。在此频率范围内，固态设备的输出功率电平是有限的。在这项研究启动拨款中探索的一种可能的解决方案是将数百个有源设备的输出相干地组合在一起，这些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栅格。这个有源面既是天线又是源。这些器件可以是以栅极反馈配置排列的MESFET。这种类型的振荡器具有宽的频率调谐范围，这在大多数应用中都是必需的。振荡的有源表面背靠具有电可变反射系数的调谐镜。这面镜子是另一个装有变容二极管的金属栅格。二极管的电容以及该调谐表面的反射系数与偏置有关。该反射镜向振荡器表面提供正反馈，这是器件锁定到单模所必需的。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打开和关闭的情况下，可以使用开关有源表面。这个表面由一个装有管脚二极管的栅极组成，它对从振荡器栅极传输的波进行电开关。该系统结构紧凑，重量轻，因为它由一堆加载了固态设备的平面介质组成，不需要大量的电源。它有多种用途，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，用于波束控制或波束形成应用，或者可以用作乘法器。此外，该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.