ABSTRACT
Recent development on wireless medical applications, such as wireless endoscopy and multichannel neural recording IC, has spurred the need for energy-efficient high data rate transmitter. For example, wireless endoscopy with image resolution of 640 × 480, 6 fps and 8-bit color depth requires a few tens of Mbps if on-chip image compression is not available. Similar requirement applies to 256-channel neural recording IC with 10-bit resolution and sampling rate of 10 kS/s. Such applications are often characterized by asymmetric data link as shown in Figure 14.1 where high data rate uplink is required to upload critical biomedical data and low data rate downlink is used only for configuring the implanted device. Therefore, complex modulation, which supports high data rate, does not necessarily lead to power-hungry solution if power-efficient transmitter architecture can be realized as the complex receiver function is usually implemented off-body without stringent power constraint. In addition,
14.1 Introduction .................................................................................................. 371 14.2 Modulation .................................................................................................... 372 14.3 Frequency and Phase Generation ................................................................. 374
14.3.1 LC-Based Injection-Locked Oscillator ............................................. 375 14.3.2 Injection-Locked Ring Oscillator ..................................................... 376
14.4 Band Shaping and Side-Band Suppression ...................................................380 14.5 Energy-Efficient Transmitters....................................................................... 381
14.5.1 QPSK and O-QPSK Transmitter Based on ILO ............................... 381 14.5.2 QPSK and 8 PSK Transmitter Based on ILRO ................................ 387 14.5.3 QPSK and 16-QAM Transmitter Based on ILRO with
Band Shaping .................................................................................... 394 14.5.4 Comparison ....................................................................................... 398
14.6 Conclusion ....................................................................................................400 Acknowledgment ...................................................................................................400 References ..............................................................................................................400
