Studies on optical control of active integrated antennas

通过对有源元件的光照射改变有源天线的振荡条件，实验实现了对有源天线振荡频率的光学控制和辐射光束的扫描。原型天线具有FET振荡器和微带贴片辐射器;一种类型具有两个圆形贴片，另一种具有矩形贴片。首先，一个单一的有源天线的振荡和辐射特性进行了研究，和两个元件阵列的特点是反相和同相的情况下。然后研究了三元阵列天线。在每种情况下，测量的特性的变化，为黑暗和照明状态，测量的辐射模式与计算的比较。从比较中评估了元件的相位差。从这些结果可以证实：（1）有源天线的固有频率因照射振荡电路的FET而改变，（2）在通过自由空间辐射弱耦合的有源天线阵的情况下，振荡器之间的相位关系因照射而改变，（3）这种阵列的合成辐射方向图可以用光学手段扫描。这些结果可推广到波束宽度窄、波束可用光学手段扫描的多阵元阵列天线。这种新型天线没有移相器，没有射频馈线，也没有任何耦合线，只有直流偏置线，所以它们的结构非常简单。与电子控制相比，光控具有固有的高速度和良好的隔离特性，因此射频电路及其控制电路的设计可以独立进行。这一事实对于电路的设计简化和小型化是有用的。

Optical control of the oscillation frequency and optical beam scanning of the radiation of active antennas were experimentally realized based on the change of the oscillation condition by the optical illumination to the active elements. The prototype antennas have FET oscillators and microstrip patch radiators ; one type has two circular patches, the other has rectangular patches. First the oscillation and the radiation characteristics of a single active antenna have been investigated, and two element arrays have been characterized for both anti- and in-phase cases. Then array antennas of three elements have been studied. In each case, the change of the characteristics were measured for the dark and the illuminated states, and the measured radiation patterns were compared with the calculated ones. The phase differences of the elements were evaluated from the comparison. It is verified from these results that (1) the intrinsic frequency of the active antenna changes by the illumination to the FET of the oscillation circuit, (2) the phase relationship between the oscillators changes by the illumination in case of active antenna arrays which are weakly coupled via free space radiation, (3) the synthesized radiation pattern of such arrays can be scanned by optical means. These results can be developed to an array antenna of many elements which has a narrow beam width and whose beam can be scanned by optical means. Such new type of antennas have no phase shifters, no rf feeders, nor any lines for the coupling, and only have dc bias lines, so their structure is very simple. Optical control has inherently high speed comparing with the electronic control, and good isolation characteristics, due to which the designs for rf circuits and their controlling circuits could be independently performed. This fact is useful for the design simplification and the miniaturization of the circuits.