T. Cavanna

High data-rate millimetre-wave modulator modelling and design

In this paper a linear and nonlinear model for microwave modulator has been realized and discussed. The model is thought to be applied to modern high data rate digital communications. The model is specialized to the widely used direct conversion quadrature modulator architecture. The EVM, Image and LO rejection performances are modelled and estimated for QAM modulation schemes. Design charts have been extracted to help the design of the building blocks of the modulator. To validate the model a 45GHz – 65GHz MMIC vector modulator, based on a doubly balanced star mixer, has been designed using 0.2 commercial PHEMT process.

Compact GaAs HEMT D flip-flop for the integration of a SAR MMIC core-chip digital control logic

The paper presents a novel, ultra-compact, reduced-area implementation of a D-type flip-flop using the GaAs Enhancement-Depletion (ED) PHEMT process of the OMMIC with the gate metal layout modified, at the device process level. The D cell has been developed as the building block of a serial to parallel 13-bit shifter embedded within an integrated core-chip for satellite X band SAR applications, but can be exploited for a wide set of logical GaAs-based applications. The novel D cell design, based on the Enhancement-Depletion Super-Buffer (EDSB) logical family, allows for an area reduction of about 20%, with respect to the conventional design, and simplified interconnections. Design rules have been developed to optimize the cell performances. Measured and simulated NOR transfer characteristics show good agreement. A dedicated layout for RF probing has been developed to test the D-type flip-flop behaviour and performances.

Design of Sub-Harmonic Mixer MMIC for EHF Satellite Links

This paper presents the design flow of a compact GaAs MMIC for Extremely High Frequency (EHF) satellite communications. The proposed circuit enables sub-harmonic mixing capability and integrates a LO buffering section, thus allowing for low frequency and low power reference signal interface. Circuit design is described in detail providing a comprehensive view of the followed theoretical approach, starting from mixer core definition until the complete synthesis of LO/RF/IF interfaces. In particular, the design flow of an innovative three-conductor Marchand balun is deeply analysed. Fabricated MMIC operates in the 43.5–50 GHz band and results in a compact layout (2.4×2.4mm2) featuring a port-to-port isolation better than 25 dB with a typical conversion loss of 12 dB.

FEM-based evaluation of manufacturing tolerances on a millimeter-waves rectangular to coplanar waveguide transition

Rectangular to coplanar waveguide hermetic transitions are frequently used in satellite payloads, to interconnect rectangular waveguides toward antennas with internal active circuits, often realized in MMIC technology. The effects of manufacturing tolerances on this kind of transition are analyzed both in qualitative terms and in quantitative ones using a Monte Carlo method applied to FEM electromagnetic simulations. Results are compared with measures on a W-band prototype.