LUT-Based Focal Beamforming System Using 2-D Adaptive Sequential Searching Algorithm for Microwave Power Transfer

Abstract

This paper presents a look-up table (LUT)-based focal beamforming system that can effectively transmit RF power up to mid-range distances (≤ 3 m) including when the Rx is in the nearfield zones. The Tx elements control and radiate signals for the Rx even at the near-field zone ensuring the received signals are in-phase. Since the proposed system uses a LUT for storing the phase sets of the signals for the Tx elements, it requires only very simple hardware and a very simple adaptive control algorithm compared to conventional retroreflective method. In order to track the moving Rx, a 2-D adaptive sequential searching algorithm is proposed. The system can find the optimum phase set by sequentially searching the phase sets for a predetermined 2-D area. The LUT of the phase sets are generated using geometric analysis over the entire 2-D area where the Rx could be located. To verify the proposed method, a 5.2 GHz mid-range (≤ 3 m) MPT system composed of a 4×8 Tx array and a 2×3 Rx array was designed and implemented. Using the proposed 2-D adaptive sequential searching algorithm, the optimum phase set for focal beamforming can be quickly found for a given position of the Rx. In our experiments, the results showed an RF power level of 177.8 mW was received at the Rx with a distance of 1 m with a total radiated RF power of 16 W. Since the measured received power levels for various Rx positions agree well with the simulation results, the proposed system was proved to be an excellent candidate for the practical application. INDEX TERMS Microwave power transfer, Look-up table, Focal beamforming, 2-D adaptive sequential searching algorithm.

Dual-Band RF Wireless Power Transfer System with a Shared-Aperture Dual-Band Tx Array Antenna

“…On the other hand, if the phase according to Equation ( 3) is applied as the excited phase of the m-th element, the transmitted beam is concentrated to a specific point (here, it is the location of Rx (x ,y ,z )), known as beamfocusing. According to the literature [7,[32][33][34], in the Fresnel region, using beam-focusing rather than beam-forming as a beam-steering method can improve the received power. Thus, we assume that the beam is sequentially formed to the 25 Rx position in Equation ( 1) by applying the beam-focusing method.…”

Adaptive Irregular Constellations for Full-Duplex Relaying With Residual Self-Interference

“…The higher is the transistor packing density and the more regular are the memory based structures, the less is the dynamic power power consumption and the lower is the latency in the implementation [14]. Therefore, LUT-based approaches have gained popularity in many modern wireless systems [12], [13], [26]. For storing constellation points, LUT-based transmission can be feasible up to 256-ary constellations in real-time applications [27].…”

“…In addition to the demapping complexity, the use of multiple constellations requires look-up table (LUT)-based structures where the constellation points are stored in them along with suitable labels. The LUT-based approaches were proposed in beamforming techniques [12], optimum input distribution for signaling [13] as well as adaptive irregular constellations over coded scenarios [3]. The complexity analysis and storage requirements of LUT-based systems can be found in [14].…”

5.8 GHz 4-Channel Beamforming Tx IC for Microwave Power Transfer

“…Since both retrodirective and retroreflective methods require a pilot Tx in the Rx and a pilot Rx in the Tx element, the systems utilizing these methods can be complex, and the Rx has additional power consumption arising from the pilot generation and transmitting circuits. To reduce the system complexity of the retrodirective or retroreflective methods, methods using a look-up table (LUT) were proposed [33], [34]. The phase sets for various Rx locations were predetermined, and stored in the LUT.…”

“…The phase sets for various Rx locations were predetermined, and stored in the LUT. The Tx should find the best phase set for the Tx array using a backscatter communication with the Rx [33], or an outband communication using a Bluetooth Low Energy (BLE) between the Tx and Rx [34]. In [35], a beamforming Tx based on an orthogonal or pseudo-orthogonal masks was proposed for near-field MPT.…”