An Integrated 5 GHz Wideband Quadrature Modem for OFDM Gbit/s Transmission in SiGe:C BiCMOS

Abstract

This paper presents a 5 GHz wideband I/Q modulator/demodulator for 650 MHz OFDM signal bandwidth, which is integrated with a 5 GHz phase locked loop for I/Q generation. The quadrature signals are derived from a 10 GHz CMOS VCO followed by a bipolar frequency divider. The phase noise at 1 MHz offset is −112 dBc/Hz for the modulator as well as for the demodulator. The chips were produced in a 0.25 μm SiGe BiCMOS technology. The signal-to-noise ratio (SNR) of transmitted/received OFDM signal and the corresponding I/Q mismatch versus baseband frequency are given. The modulator achieves an SNR of 22–23 dB, and the demodulator realizes an SNR up to 22 dB. The modulator reaches a data rate of 2.16 Gbit/s using 64 QAM OFDM, and the demodulator realizes 1.92 Gbits/s.

An integrated differential 60 GHz sliding-IF receiver in SiGe BiCMOS

“…This design is based on [6] with operation frequency optimized from 5 GHz to 12 GHz. The topologies of the IQ mixers and VGAs are different from those in [6]. Both IF and baseband VGAs share the same topology as shown in Figure 3.…”

“…Above 15 dB tuning is not recommended because the current becomes too small and the linearity is not acceptable. In mixer core, the tail current source (TCS) in [6] is separated into two current sources and the degeneration resistor is placed across these two TCSs as shown in Figure 5. This extra freedom of tuning the two TCSs independently can compensate for the mismatches due to process variation.…”