通过碎片孔径分阶段的效率提高效率

The world’s demand for broadband connectivity has created a new generation of high-throughput satellites in geosynchronous Earth orbit (GEO), medium Earth orbit (MEO), and now low Earth orbit (LEO). But technology innovation in the ground segment has struggled to catch up to the space segment, especially when it comes to developing the most elusive of all antennas: Those that are low-cost and electronically steerable to power these next-generation, lower-orbit satellite networks.

Electronically steerable antennas (ESAs), often referred to as flat panels, are the critical link for next-generation constellations. Compared with their bulkier mechanical cousins, flat-panel antennas offer greater efficiency and performance while being modular and dynamically steerable—all of which are needed for the future ground segment.

While ESAs’ flat and conformal characteristics can have aesthetic benefits, the real benefit comes from their performance. LEO and MEO satellites require the ability to track and communicate with two or more satellites in view at the same time, and this can only be done with multiple mechanical antennas. With no moving parts, ESAs are more reliable and efficient as they can connect to multiple satellites at the same time. This gives a single ESA the ability to interoperate with multiple orbits—not just GEOs.

这样的下一代天线对于进入大众消费者的连接市场至关重要，但是每个人都同意的第一批用户将来自商业和国防流动市场。

Ground Segment Growth

NSR是一家市场研究和咨询公司NSR，估计到2028年，整个地面领域的累计收入总计1450亿美元。该公司在最近的报告中说，到2028年，该市场每年将每年产生144亿美元Commercial Satellite Ground Segment, 4th Edition (CSGS4)。The user terminal will command a substantial portion of this spend.

寻找ESA的圣杯

Given the importance of these terminals, how are antenna developers tackling the ESA challenge from an architecture perspective, and when will this technology be accessible on broadband networks?

Many different approaches can be taken to develop next-generation flat-panel antennas. All consist of small antennas, known as radiating elements, and both receive- and transmit-side amplification. From here, broadly speaking, these can be categorized as passive or active antennas.

A passive antenna takes one signal from the power amplifier (PA) on the transmit side and divides this signal out to the transmit radiating elements, then combines the receive signals from the radiating elements before feeding the receive-side low-noise amplifier (LNA). An active antenna, in contrast, has a single amplifier per radiating element, for both transmit (TX) and receive (RX). In general, passive antennas are less complex, while active antennas provide greater gain performance.

Next, we need to look at how the signal paths are formed, where either analog or digital beamforming are applicable. New materials, from improved RFICs to custom ASICs to lenses, provide many ways to solve this challenge. But all of these new approaches require invention, development effort, and time before they are likely to be deployed in the field.

最近的发展已经进入了back of the antenna—how beams are formed, how one develops better RFICs, and so on. However, not much innovation capital has been invested in the front side itself, known as the radiating elements.

nxtcomm’s天线利用了零散的驱动技术，这是数十年来国防研发投资以及与其技术研究合作伙伴合作的结果Georgia Tech Research Institute。The company’s phased-array antenna design focuses on more efficient radiating elements to improve the portion of the antenna facing the satellite.

More Efficient Radiating Elements

Traditional radiating-element design takes a monolithic approach—namely, a single circle of copper, a square, a trapezoidal solid, or an iron cross. These radiators are then stepped and repeated around the array to meet the required gain for the use case.

One limitation is that those shapes can contribute to a reduction in gain by causing parasitic coupling. Simply put, one element close to another can interfere with its neighbor. The more elements in the array, the greater the parasitic coupling, and the lower the efficiency. This interference impacts gain in general but can also lead to undesirable grating lobes, and perhaps contribute to an undesirable antenna pattern, especially on the transmit side. These elements may also be resonant structures, limiting the antenna’s overall frequency.

Such factors negatively impact the overall efficiency of the aperture. Typical antennas using these radiating elements achieve an aperture efficiency of 60% to 70% when scaled up to a size appropriate for satellite communications.

In a fragmented aperture, the radiating element isn’t a single piece of copper. Instead, it’s pixelated, like an array within an array(Fig. 1)。这种方法不仅有助于减少元素之间的寄生耦合，而且还有助于提高增益并提高侧虫性能。

In addition, the fragmented-aperture architecture allows for significantly greater antenna bandwidth. Because the elements aren’t inherently resonant structures, they can be designed to cover very wide bandwidths. This flexibility is particularly important in the emerging LEO use case as the antenna needs to target multiple satellites simultaneously, requiring use of different ranges within the frequency band.

Wideband Frequency Coverage

The fragmented-aperture approach can support bandwidths of up to 100:1 and typically 33:1. In the bands of interest for satellite communications, fragmented-aperture flat panels support the entire Ku-band (10.7 GHz to 14.75 GHz) or even the Ka-band (17.2 GHz to 30 GHz) with a single element, making it possible to use a single antenna across a wide range of satellite networks.

In terms of aperture efficiency, these antennas achieve efficiencies in the 85% to 90% range when scaled up to a size suitable for satellite communications. When compared in terms of aperture efficiency, a fragmented-aperture antenna array achieves efficiency of 80% to 90% while a traditional square-element antenna array delivers efficiency of 60% to 70%(Fig. 2)。

Better Efficiency Means Better Performance

Increased efficiency at the satellite-facing side of the antenna improves overall system performance. The greater the gain, the lower the power consumption of the antenna system. With lower power consumption comes the added benefit of less heat to dissipate.

NXTCOMM的方法将零散的光圈与主动拼错的阵列架构结合在一起。众所周知，传统的活跃阵列非常渴望，需要异国情调的冷却。通过采用这种方法，这两个有害的伪影大大减少了。

在射频层使天线更有效率also makes it more efficient to manufacture. NXTCOMM’s fragmented-aperture antenna can be built on a single printed circuit board (PCB), reducing part count and complexity and making the overall antenna less costly. Elements comprise subarrays, and subarrays comprise complete antenna arrays(Fig. 3)。

为了满足Leo Mega-Contellations新现实的潜力，用户终端是关键。该行业需要寻找可以按时交付的经过验证的技术，并需要为服务不足的高速连通性带来高速连接所需的规模，并在移动市场中解锁了完整的宽带。

参考

nxtcomm/GTRI Antenna Design Collaboration

nxtcommAeroMax Antenna Announcement

nxtcommBlog Q&A: Meet Carl Novello, NXTCOMM’s New CTO

Patent: CITE Fragmented aperture antennas and broadband antenna ground planes US6323809B1

“新设计创建超宽带天线,”Georgia Tech News