We present our recent work on high-speed optical interconnects with advanced modulation formats and directly modulated 850 nm VCSELs. Data transmission at nearly 100 Gbps was achieved with 4-PAM. Forward error correction, equalization and preemphasis are also explored. The system aspects of the advanced modulation formats and their impact on the VCSEL requirements are discussed. Requirements on the optical output power, frequency response and the relative intensity noise are discussed. Finally, co-optimization of the VCSELs and VCSEL driver amplifiers in CMOS and InP technologies is discussed.
This paper presents a pre-amplified detector receiver based on a 250 nm InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) process available from the Teledyne scientific. The front end consists of a double slot antenna followed by a five stage low noise amplifier and a detector, all integrated onto the same circuit. Results of measured responsivity and noise are presented. The receiver is characterized through measuring its response to hot (293) and cold (78) K terminations. Measurements of the voltage noise spectrum at the video output of the receiver are presented and can be used to derive the temperature resolution of the receiver for a specific video bandwidth.
The development of a 210 GHz radar system intended to study security applications such as personnel scanning is reported.
The system is designed to operate with a transmit antenna floodlighting the target scene and a mechanically
scanned antenna-integrated receiver module. For increased performance and potential future volume production the receiver
front-end is based on highly integrated MMICs manufactured using the IAF 0.1 μm GaAs mHEMT process made
available through a Swedish-German MoU. A single-chip MMIC solution is being developed containing feed antenna,
LNA, mixer and an LO multiplier-chain. The transmitter part is based on a high-power HBV quintupler source-module.
Noise parameters of AlGaAs/GaAs and InGaP/GaAs HBTs were measured in microwave frequency range and modeled using the small-signal equivalent circuit approach. Correlated current noise sources in the base and collector currents with thermal noise in the circuit resistive elements were accounted for by the model and yielded good agreement with the measured data. This enabled an extraction of the different noise source contributions to minimum noise figure (NFmin) in AlGaAs/GaAs and InGaP/GaAs HBTs. Decomposition of the (NFmin) in to the different contributors showed that the main noise sources in investigated HBTs are correlated base and collector current shot noise. The observed minimum of NFmin versus frequency at lower collector current is explained by the reduction of the emitter/base junction shot noise component due to the spike in the emitter/base junction and associated accumulation of the quasi-thermalized electrons forming a space charge, which screens the electron transfer through the barrier. The bias (VCE) increase creates an efficient electric field in collector/base junction, capable of 'washing out' the accumulated charge. Such shot noise reduction in HBTs could be exploited in the LNA for the RF application.