Hardware Solutions for High Data Rate Modems

Licentiate thesis, 2011

The exponentially-growing mobile data traffic imposes significant demands on the capacity of the mobile network. Fiber optic and microwave links are two main solutions for the mobile backhaul network, which provides connectivity between radio base station (RBS) sites and the switch sites. As compared to fiber, a microwave solution is much easier to deploy, however, its capacity is lower. This thesis is devoted to the design and implementation of modems supporting high data rate transmission. This thesis includes the design and implementation of one MMIC-based on- /off- keying (OOK) modem and two FPGA-based differential phase shift keying (D-QPSK) modems. The OOK modem is designed for short-distance applications. The D-QPSK modems are made for high capacity microwave radio applications. The OOK modulator is implemented in a heterojunction bipolar transistor (HBT) process, and is capable of transmitting data at rate of 14 Gbps. The OOK demodulator is implemented in a metamorphic high electron mobility transistor (mHEMT) process with a detection range of 10 to 60 GHz. An OOK link is set up and 10 Gbps transmission is achieved. For the D-QPSK scheme, a 2.5 Gbps and a 5 Gbps D-QPSK modem are implemented with FPGAs and microwave components. Modifications at the modulator and demodulator are explained, which doubles the data rate of the D-QPSK modem. It also enables the possibility of scaling up to even higher data rates. A point-to-point radio is demonstrated by using such a modem and commercial E-band RF front-end components, which achieves 5 Gbps full-duplex data transmission.