UCLA

In the earlier days of the Complementary Metal Oxide Semiconductor (CMOS) industry, much effort was dedicated to the performance of device speed and number of transistors per processor core in response to Gordon Moore's law. However, the attention has gradually migrated to the system-level design, such as signaling and timing conventions for efficient data transactions. This is because the system clock speed is no longer limited by CMOS device cutoff frequencies, and the system performance becomes limited by either on- or off-chip interconnects. In order to overcome such difficulties, various ideas have been proposed including pre-distortion, equalization, and multi-level signaling. However, the burden on transferring data becomes dominant in overall system design as the demands for higher computing capabilities ever increase. My research focuses on maximizing the bandwidth efficiency by exploiting RF/Wireless techniques and minimizes the interconnect complexity. I explored 3 different hypotheses.

The first case is an on- and off-chip communication through copper wires. When a point-to-point or point-to-multi-point communication is established, the data signal experiences discontinuities through vias and connectors. Then, it affects the channel frequency response with deep notches where the signal undergoes resonances. A typical solution would equalize the channel based on the worst case notch, but the penalty is the reduced signal to noise ratio (SNR). Instead of sacrificing SNR, I accept the channel impairments and send data where there is no such notches using RF modulation on top of baseband signal.

The second case is a short-range wireless data communication through the air. Data connectors are everywhere in our daily lives. For instance, USB connectors in computers and cell phones, HDMI connectors in monitors and TVs. The mechanical parts are not only expensive but also bulky in size. Just as in first case, the high speed signal suffers discontinuities as well. Instead of struggling with mechanical parts, the wireless interconnect utilizes the abundant free-license band at 60GHz and provides giga-bits-per second (Gb/s) data rate with a minimum complexity and power efficiency because of its nature in short-range communication.

The last one is a mid-range (1meter to 10meter) data communication through plastic cables. In an example of data server communication market, the fiber optics has been a dominant solution because of the long-distance capability and large data bandwidth. However, it requires electrical to optical, and optical to electrical conversion with a strict temperature control. Keeping the advantage of low-loss channel characteristic, modulated RF signals can propagate through plastic tubes or strips without the cost of conversion process.