Karlheinz Muth

4.25 Gb/s laser driver: design challenges and EDA tool limitations

This paper describes the design methodology, simulation, and tools used to design a 4.25 Gb/s high output swing laser driver (LD) and the electrical to optical interface from the LD to the laser diode. The quality of the optical output of a fiber optic communication channel is mainly determined by the LD and the electrical interface from the LD to the laser diode. Of particular importance in the interface is how well the LD overcomes the impact of the parasitic, resistive, capacitive, and inductive elements associated with the bondpad, bondwires, package, PCB transmission lines, passive components, and laser diode and its bondwires. The EDA tools used to model the electrical parasitics focus on RF and microwave applications and provide high frequency S-parameter models. This environment requires a stable time domain model of the electrical to optical interface. The presented LD integrated circuit operates from 155 Mb/s to 4.25 Gb/s with rise and fall times of 70 ps or less and a wide output voltage range, and a modulation current range of 5 mA to 85 mA

Millimetre wave VCOs with wide electronic tuning range for synthesised radios

A series of new and very compact local oscillators for point-to-multipoint (PMP) and point-to-point (PtP) radio link systems has been developed in the 26GHz to 36GHz frequency range. The oscillators mainly consist of a GaAs-pHEMT microwave monolithic integrated circuit (MMIC) and a planar ring resonator (RR), Three MMICs have been designed to cover the whole frequency range. The ring resonator operates at harmonic frequencies. An innovative fully automated active laser-trimming procedure is used to adjust the centre frequency, the varactor tuning sensitivity, the electronic tuning range, respectively, and the electrical line length between the MMIC and the ring resonator. The laser tuneable frequency range is larger than 10% without any significant deterioration of the oscillators characteristics. The maximum electronic tuning range can be adjusted by laser-trimming to values of more than 2.5% of the centre frequency. A typical single side-band phase noise value of approx.-108dBc/Hz is achieved at an offset frequency of 1MHz. The temperature drift of the oscillator frequency is typ. 9ppm/K.