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

高频（毫米波及以上）无线通信链路受到链路路径损耗急剧增加的严重限制。与这种增加是由传播或自由空间路径损失的增加引起的常见和公认的措辞相反，这实际上不是真正的原因。路损增加的真正原因是所用接收天线在频率增加时有效接收面积的减小。增大有效接收面积将大大提高天线的增益，但缺点是天线的波束宽度变得很窄。这使得大型接收区域天线难以对齐，并限制了它们在多输入多输出（MIMO）配置中的可用性。为了克服这些限制，提出研究和实现同时具有大有效面积和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，所提出的概念利用频率转换到较低的频带，然而，在那里，没有由接收器传递的本地振荡器信号被用于转换。保持大波束宽度的目标是通过将信号与自身混合来实现的，例如在方形探测器中，以及在下变频后将低频范围内的各种天线元件的信号相干地组合在一起。接收器中的混合过程可以通过发射具有从古代调幅中已知的特定载波的信号来辅助。然而，更复杂的信号形式也需要研究和专门设计。提出的概念将克服毫米波及以上频率无线链路在通往超高速通信的道路上的一些限制，同时它将导致相对简单的接收器前端，因为不需要产生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大大缓解。传统的数字波束形成解决方案需要100多个完整的接收通道（每个天线单元一个），包括混频器、本地振荡器、低噪声放大器和模数转换器，以实现所需的有效接收孔径，与此相反，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探测器。对于MIMO，将实现几个拟议的接收天线，彼此独立或可能相互交错，其中每个MIMO信道需要一个接收信道。

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.