Beamforming of active antenna array with self-oscillating harmonic mixers

研究了采用自振荡谐波混频器的有源天线阵列进行波束控制。有源天线由接收射频信号的贴片天线和作为自振荡谐波混频器的并联反馈型振荡器组成，并将接收到的射频下变频为中频信号。混频器有两个端口用于本地振荡（LO）信号。一个是提取LO信号的输出端口。另一个是用于同步本地振荡的注入信号的输入端口。通过将输出端口连接到下一个混频器的输入端口，该混频器可以在没有其他非互易组件的情况下进行单边耦合。在单侧耦合阵列中，通过改变自振荡混频器的局部自由运行频率，可以改变注入锁定状态下相邻混频器之间LO信号的相位差，而无需移相器。接收模式可以通过组合来自各个有源天线的中频信号来控制，这些天线的相位与本振信号相关联。中频在RF和本LO频率的两倍之间不同，因此可以为输出中频信号提供从0到2π弧度的任意相位差。利用二元阵列和三元阵列的实验验证了波束控制能力。此外，通过优化自振荡混频器反馈环路上定向耦合器的耦合强度，提高了从射频到中频的转换效率。

Beam control using active antenna arrays with self-oscillating harmonic mixers has been investigated. The active antenna is composed of a patch antenna receiving RF signal and a parallel feedback type oscillator which operates as the self-oscillating harmonic mixer, and down-converts the received RF into IF signal. The mixer has two ports for local oscillating (LO) signal. One is an output port extracting the LO signal. The other is an input port for an injection signal to synchronize the local oscillation. The mixers can be coupled unilatarally without other nonreciprocal components by connecting the output port to the input port in the next mixer. In the unilaterally coupled array, the phase differents of the LO signals between the adjacent mixers can be varied without phase shifters in injection locking state by changing the local free-running frequencies of the self-oscillating mixers. The receiving pattern can be controlled by combining the IF signals from the individual active antennas, which have phases associated with the LO signals. The IF is different between the RF and double of the LO frequency so that arbitrary phase differences from 0 to 2π radian can be providedto the output IF signals. The experiments using the two- and three-element arrays demonstrated beam control capability. In addition, conversion efficiency from RF to IF was increased by optimizing coupling strength of a directional coupler on a feedback loop in the self-oscillating mixer.