# Sub-Milliwatt Transceiver IC for Transcutaneous Communication of an Intracortical Visual Prosthesis
## 6 Discussion  
### Comparison with the State of the Art  
Next, we benchmark our work with state of the art results from the literature. Table 2 compares our implanted transmitter with recently published general transmitter ICs. Clearly our transmitter performs similarly, or better, in terms of data rate. Power consumption is better than reported in [40; 41; 42] with the standard 180 nm CMOS technology available for IC design in our lab, but worse than reported in [43; 44]. The latter two [43; 44], however, use 0-200 MHz and use the body as a wire, respectively. The systems in [43; 44] are not suitable to meet the co-existence requirements for our overall system application. This is mainly due to differences in applications and intended ranges. However, this stresses the need for the low-power approach that we followed for the intracortical visual prosthesis. Table 3 compares with other high data rate state-of-the art medical implants. We achieved a lower power consumption but at a lower data rate, which is still sufficient for our current application. This shows that our IR-UWB transmitter approach to use predominantly digital components and simple architecture is effective. In [45; 46; 47], a much lower data rate of \(<\)30 Mbps was reported, which is not well-suited for our data rate requirements for the uplink. In [48], a higher data rate is shown at slightly lower power consumption, but the higher frequency band of 6.8-9 GHz reportedly used will face about 10 dB more attenuation through the skin tissue. Table 4 compares the implanted receiver with recently published general receiver ICs. While we have a comparable data rate, we achieve much lower power consumption, except for the results reported in [43] which is not designed for skin tissue interaction, its frequency spectrum of 0-200 MHz may not co-exist in frequency band with other parts of our system.This due to our short-range and coupled-coil link, which relaxes the need for very sensitive receiver, which would have raised the power consumption. Table 5 compares our receiver with other medical implants. Our receiver is of comparable data rate with much lower power consumption. Our power consumption is better than in the first five columns and only worse than in [49]. However, the data rate of 0.01 Mbps reported in [49] is low and 20 times below the minimum data rate requirement of 0.2 Mbps for the intracortical visual prosthesis. This shows that our non-coherent digital demodulator is effective in low-power consumption compared to traditional receivers. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & [50] & [51] & [52] & [53] & [54] & [55] & [43] & **This Work** \\ \hline Data rate & 1.3 Mbps & 10 Mbps & 11 Mbps & 1 Mbps & 1 Mbps & 50 Mbps & 1 Mbps \\ \hline Power consumption & 5.2 mW & 3.2 mW & 2.4 mW & 9.6 mW & 0.9 mW & 1.5 mW & 0.041 mW & 0.2 mW \\ \hline Frequency & 18–23 MHz & 40–120 MHz & 2.4 GHz & 2.4 GHz & 2.4 GHz & 2.4 GHz & 0–200 MHz & 4 MHz \\ \hline Modulation & BPSK & Double FSK & BLE & BLE & BLE & BLE & DDM & BPSK \\ \hline Technology & 130 nm & 180 nm & 40 nm & 65 nm & 28 nm & 28 nm & 180 nm \\ \hline Supply Voltage & 1.2 V & 1 V & 1 V & 3 V & 0.7 V & 1 V & 1.3 V \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison with recently published IC-receivers. (DDM—Differential detection method, BLE- Bluetooth Low Energy). \begin{table}
\begin{tabular}{c c c c c c c} \hline  & [40] & [41] & [42] & [43] & [44] & **This Work** \\ \hline Data rate & 1 Mbps & 1 Mbps & 11 Mbps & 50 Mbps & 30 Mbps & 50 Mbps \\ \hline Power consumption & 3.7 mW & 0.42 mW & 4 mW & 0.0237 mW & 0.093 mW & 0.3 mW \\ \hline Frequency & 2.4 GHz & 3–5 GHz & 401–428 MHz & 0–200 MHz & Broadband & 3–5 GHz \\ \hline Modulation & BLE & UWB & QPSK & TTC & HBC & UWB \\ \hline Technology & 28 nm & 180 nm & 130 nm & 180 nm & 180 nm & 180 nm \\ \hline Supply Voltage & 1 V & 1.8 V & 1 V & 1 V & 1 V & 1.3 V \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison with recently published IC-transmitter. (HBC—Human body communication, TTC—Transmission time control).