Wireless telemetries power telemetry

Suster M, et al. An optically powered wireless telemetry module for hightemperature MEMS sensing and communication. J Microelectromech Syst 2004. 

These applications, by nature, impose serious limitations on power and area in the design of neural-recording systems. Researchers have developed several kinds of neural-recording systems [23-27], and those systems are generally composed of preamplifiers to amplify the small extracellular potentials, low-pass filters to reject the high frequency noise, multiplexers, and analog-to-digital converters (ADCs) followed by the wireless telemetry circuits to transmit data out of the body. 

Wireless pH measurement systems have been used in clinical studies. Unlike a standalone pH electrode, a power source, control electronics, and a signal transmitter have to be incorporated into a wireless system. Watanabe et al. [138] have reported a wireless pH sensor to record salivary pH continuously. The sensor system transmits pH data via a telemetry system for about 19 hours with a 3V lithium battery (190mAh). The error of transmitted pH data was less than 0.15 pH in the range of pH 5.0 to 9.0. 

A simplex telemetry system is employed for the transmission using straightforward modulation schemes such as amplitude modulation, on-off keying, amplitude-shift keying, and phase-shift keying [101-103]. Because the physiological signals vary slowly, such modulation schemes are preferable for miniaturized and low-power wireless biosensors. 

Figure 30 shows a simplified dual-band wireless power and data telemetry. There are six different coupling coefficients, named Ki2 pw. Ki2 data, Kn, K22, Kdata pw, and Kpw-data between 4 coils. Among these six coefficients, the Ki2 j9w and Ki2 data affect power and data transfer efficiencies, and the others, Kn, K22, Kdata pw. and K -data determine the power interference to the data transmitter and receiver [117]. 

Although there are several communication standards for biomedical applications, most of them eannot provide enough bandwidth for simultaneous recording from more than 100 ehannels. For example, MICS band, which is allocated for the unlicensed use of implantable devices, allows only 300 kHz for data transmission. Other wireless technologies such as Wi-Fi and Bluetooth cannot be used directly due to the power and area constraint of the implanted device. Therefore, there is a need for higher-bandwidth data transmission telemetry that consumes low power and occupies less physical area. 

Wang G (2006) Wireless power and data telemetry for retinal prosthesis. Ph.D. dissertation, University of California, Santa Cruz, EE Dept., CA, USA, Mar. 2006. 

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