Equation-Based Optimization for Inductive Power Transfer to a Miniature CMOS Rectenna

Miniaturised Wireless Power Transfer Systems for Neurostimulation: A Review

“…M 12 can be calculated using complete elliptic integrals of first and second kind K(k) and E(k) [43]: (17) where x and y are the spatial coordinates and d 12 is the distance between the coils. Another approach is to compute the value of the mutual inductance from the coil geometry and deriving the magnetic flux over a surface by superposing the effect of all the segments of the coil geometry, as in (18) [44]: [36] 2013, [37] * 2017, [38] 2019, [39] 2018, [40] 2018, [41] 2013, [42] IPT…”

“…Biederman and collaborators proposed a 2-coils link with a 250 × 500 µm 2 on-chip receiver coil integrated in a 65 nm CMOS processes to transmit almost 10.5 µW with a PTE of 0.021% across 1 mm of air at 1.5 GHz [42]. In a second study, the same technology was used to simulate a 100 × 100 µm 2 on-chip coil operating at 2 GHz for a powering distance of 1.2 mm [41]. Here, the authors provided an efficient equation-based optimisation procedure able to predict the efficiency of a 2-coils IPT system with an enormous advantage in terms of computational cost.…”

“…One of the most important properties of the APT technique is the focusing of the acoustic beam generated by the Tx transducer. The focal zone is the point of transition between the near-field and the far-field regions [84], and it is mathematically expressed by the Rayleigh distance L as in (41):…”

“…Several ultrasonic beam-forming algorithms were proposed: from simple time delay and sum transmit beam-forming algorithms to more sophisticated ones suitable for high spatial resolution [97]. Since the Rayleigh distance strongly depends on both the Tx diameter and the sound propagation wavelength in the medium (41), another solution is increasing the Tx diameter and/or the operating frequency. In both cases, the focal point is pushed deeply inside in the tissue increasing the US near-field area available to power multiple implants.…”

A Radio Frequency Magnetoelectric Antenna Prototyping Platform for Neural Activity Monitoring Devices with Sensing and Energy Harvesting Capabilities

“…The distance measurement range was selected as 3.5-13.5 mm, which is of interest for brain implantable devices based on the assessments in [4,9]. The measured PTE from this experiment was approximately 0.28% at 3 mm distance between the Tx coil and ME antenna in free space, which is one of the highest among the reported PTEs for receivers using antennas of small size [16][17][18][19]. The specific absorption rate (SAR) was not simulated because it is highly contingent on the application.…”