Disruptive Beamforming Trends – 2 Improving mmWave 5G – Challenges
In response to the challenges of designing 5G-ready beamformer hardware at mmWave (re. my article of last month), disruptive technological trends have emerged that are likely to change the way we look at mmWave beamforming hardware.
One such example is the use of a multi-stage lens-based beamformer, in which the requirement of the complex phase shifter and power networks is avoided. As a result, many antennas can be fed using a smaller number of radio frequency chains (power amplifier, mixer, and filter). This way, beamforming gain is achievable, thanks to many antennas, while the cost of the system is kept minimal since the phase-shifting required for beamforming is done in low-cost lens structures.
A simple example of such a system is shown below, in which a 15-element antenna array is shown to be capable of generating nine independent radio beams . The system is designed to operate on 28 GHz and is in line with 3GPP standards for 5G. This system is scalable to 64 or even 128 antenna elements, and still, low cost because the beamforming is possible without the requirement of complex and costly phase-shifting networks.
A second example is related to successful channel sounding in mmWave 5G bands. The classical radio channel sounder hardware that works well at sub-6 GHz bands of 5G is not efficient enough to support mmWave channels. A new technique of sounding requires much simpler beamforming hardware than the conventional fully connected antenna array and can deliver fast and accurate direction-of-arrival estimations in the mmWave bands. This technique requires only a metallic cavity with sub-wavelength holes on one side and a scatterer placed inside the cavity [2-3].
An example structure is shown Fig. 2. The cavity uses a frequency-diverse computational approach to do the direction-of-arrival estimation, which requires a single radio frequency chain, hence a low-cost solution again.
Next month, we will describe two more examples for addressing these challenges.
Disruptive Beamforming Trends – 2
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