mm-Wave Antennas with Large Effective Receiving Area Over a Wide Angular Range

高频(毫米波及以上)的无线通信链路受到链路路径损耗急剧增加的严重限制。与普遍接受的措辞相反，这种增加是由传播或自由空间路径损耗的增加引起的，实际上这并不是真正的原因。路径损耗增加的真正原因是在不断增加的频率下使用的接收天线的有效接收面积减小。增加有效接收面积将大大增加天线的增益，但缺点是天线的波束宽度变得非常窄。这使得大接收面积天线很难对齐，并限制了它们在多输入多输出(MIMO)配置中的可用性。为了克服这些局限性，提出研究和实现同时具有较大有效面积和较大波束宽度的接收天线。很明显，这一要求违反了互惠原则。因此，所提出的概念利用到较低频带的频率转换，然而，不使用由接收器传送的本机振荡器信号来进行转换。保持大波束宽度的目标是通过例如在正方形检测器中将信号与其自身混合并且通过在下变频之后相干地组合在较低频率范围内的各种天线元件的信号来实现的。接收器中的混频过程可以通过利用从古老的幅度调制获知的特定载波来传输信号来辅助。然而，还应调查和特别设计更复杂的信号形式。拟议的概念将克服无线链路在迈向超高速通信的过程中在毫米波频率和更高频率上的一些限制，同时它将导致相对简单的接收器前端，因为不需要生成和分发本地振荡器信号。此外，天线阵列中通常难以满足的间距要求将得到相当大的缓解。传统的数字波束形成解决方案在60 GHz频段需要100多个完整的接收通道(每个天线单元一个)才能获得所需的有效接收孔径，与之不同的是，所提出的天线概念只需要一个带有低噪声放大器和模数转换器的接收通道以及每个天线单元的方形检测器。对于MIMO，将实现几个建议的接收天线，它们彼此独立或可能彼此交错，其中每个MIMO信道将需要一个接收信道。

Wireless communication links at high frequencies (mm-wave and above) are severely restricted by the strongly increasing pathlosses of the links. In contrast to the common and accepted wording that this increase is caused by an increase of the propagation or free-space pathloss, this is actually not really the cause. The true cause of the pathloss increase is the decrease of the effective receiving areas of the used receiving antennas at increasing frequencies. Increasing the effective receiving area will substantially increase the gain of the antennas, but for the disadvantage that the beamwidth of the antennas becomes very narrow. This makes large receiving area antennas hard to align and restricts their usability within multiple input multiple output (MIMO) configurations. To overcome these limitations, it is proposed to investigate and realize receiving antennas which have a large effective area and a large beamwidth at the same time. It is clear that this requirement violates reciprocity. Therefore, the proposed concept utilizes a frequency conversion to a lower frequency band, where, however, no local oscillator signal delivered by the receiver is used for conversion. The goal of maintaining a large beamwidth is achieved by mixing the signal with itself, e.g. in a square detector, and by coherently combining the signals of various antenna elements within the lower frequency range after down-conversion. The mixing process in the receiver can be assisted by transmitting a signal with a particular carrier as known from the ancient amplitude modulation. However, more sophisticated signal forms shall also be investigated and particularly designed. The proposed concept will overcome some of the limitations of wireless links at mm-wave frequencies and above on the way to ultra high-speed communications and it will lead at the same time to relatively simple receiver frontends, since no local oscillator signals need to be generated and distributed. Moreover, the often hard to fulfill spacing requirements in antenna arrays will be considerably relieved. In contrast to a “conventional” digital beamforming solution, which needs e.g. in the 60 GHz band more than 100 complete receive channels (one per antenna element) with mixer, local oscillator, low-noise amplifier and analog to digital converter in order to achieve the desired effective receiving aperture, the proposed antenna concept would need only one receive channel with low-noise amplifier and analog to digital converter together with the square detectors for every antenna elements. For MIMO, several of the proposed receiving antennas would be realized, independent from each other or possibly interlaced with each other, where one receive channel would be needed for every MIMO channel.