Detlev Hollmann

A 29 GHz DRO in coplanar waveguide configuration with an AlGaAs HEMT

A millimeter-wave GaAs HEMT MMIC oscillator at 29 GHz with a new linear and nonlinear HEMT model has been developed which is able to describe the single side source grounded configuration. The resonance frequency and output power has been predicted by the nonlinear simulation. The output power of the oscillator is greater than 6 dBm and with different dielectric resonators (DRs) the oscillator can lock to resonance frequencies from 26.5 to 29.5 GHz. The active device is a AlGaAs-GaAs HEMT with a gatelength of 0.2 /spl mu/m and a gatewidth of 2/spl times/40 /spl mu/m.

A monolithic broadband 10-50 GHz distributed HEMT mixer including active LO-RF combiner

A millimeter-wave GaAs HEMT MMIC distributed mixer covering the RF frequency range from 10 to 50 GHz with IF frequencies from several MHz to 5 GHz was developed. The active devices are AlGaAs-GaAs HEMTs with a gatelength of 0.2 /spl mu/m and a gatewidth of 2/spl times/25 /spl mu/m. The conversion gain of the mixer is better than -3 dB over the frequency range at an LO power of less than 5 dBm without IF amplification. The RF and the LO signals are fed through an active distributed combiner with 2 dB gain and LO to RF port isolation of 20 dB. The size of the single mixer is 1.5/spl times/1 mm/sup 2/ and of the combiner including bias networks is 2/spl times/1 mm/sup 2/. An integrated broadband mixer chip including the LO and RF combiner was fabricated with a size of 4/spl times/1 mm/sup 2/.

The introduction of surface resistance in the three-dimensional finite-difference method in frequency domain

A full-wave treatment of lossy three-dimensional structures using the finite-difference method in the frequency domain is presented. This accounts for both dielectric and conductor losses. By the introduction of a surface resistance, the effect of conductor losses and surface roughness can be modeled very efficiently. The modifications of the finite-difference-frequency-domain (FDFD) algorithm are presented. Comparisons between the conventional approach using elementary cells with finite conductivity and this new discretization method with surface current cells are given, and the advantages and limitations of the surface current model are shown. >

A monolithic 2-52 GHz HEMT matrix distributed amplifier in coplanar waveguide technology

This paper discusses design, performance and fabrication of a two-stage four-section GaAs monolithic matrix distributed amplifier covering the frequency range from 2 to 52 GHz. The achieved gain is about 9 dB and the return loss is better than 12 dB. The devices we used are 2/spl times/25 /spl mu/m, 0.2 /spl mu/m recessed gate AlGaAs-HEMTs and the coplanar waveguide was the propagation medium for this broadband amplifier. The chip dimensions of the amplifier including the bias networks are 2.0 mm/spl times/2.5 mm.<<ETX>>

A monolithic 1-55 GHz HEMT distributed amplifier in coplanar waveguide technology

A single stage four section 1-55 GHz GaAs monolithic distributed amplifier in coplanar technology has been developed. The achieved gain is more than 5 dB, the noise figure between 10 - 40 GHz less than 5.5 dB and the return loss is better than 10 dB. The active devices for the amplifier are 0.2 ¿m recessed gate AlGaAs HEMTs. The chip dimensions are 1.5 mm × 1.5 mm including bias networks.

A nonlinear HEMT model for the design of frequency doubler and mixer circuits

This paper presents a nonlinear transistor model for millimeter wave HEMT devices. The model has been implemented in both parameter extraction and commercial circuit simulation software. It takes into account the nonlinearities of the gate-source and the gate-drain capacitances, and it allows accurately modeling of the transconductance as a function of the gate-source voltage. The model has been validated using a large-signal measurement system. Several nonlinear circuits comprising frequency doublers, oscillators and mixers have been designed and the measured results are in good agreement to the nonlinear simulation.

A monolithic integrated HEMT frontend in CPW technology from 10-50 GHz for measurement systems or broadband receivers

In this paper the design, performance and fabrication of a broadband frontend is shown. The frontend consists of a broadband matrix distributed amplifier with a gain of about 10 dB and a noise figure of 6.5 dB, a four stages distributed amplifier with 5 dB gain and an output power of 12 dBm, and a distributed mixer with a conversion gain of 0 dB with a LO-power of 0 dBm including the LO buffer amplifier. The active devices are 0.2 /spl mu/m recessed gate AlGaAs HEMTs and the coplanar waveguide is used as the propagation medium. The devices have been simulated by using own models for the active device and the passive coplanar elements. For the mixer design a nonlinear HEMT model was used. The total size of the frontend is 6 mm/spl times/6 mm including bias networks and block capacitors.<<ETX>>In this paper the design, performance and fabrication of a broadband frontend is shown. The frontend consists of a broadband matrix distributed amplifier with a gain of about 10 dB and a noise figure of 6.5 dB, a four stage distributed amplifier with 5 dB gain and an output power of 12 dBm, and a distributed mixer with a conversion gain of 0 dB with a LO-power of 0 dBm including the LO buffer amplifier. The active devices are 0.2 /spl mu/m recessed gate AlGaAs-HEMTs and the coplanar waveguide is used as the propagation medium. The devices have been simulated by using our own models for the active device and the passive coplanar elements. For the mixer design a nonlinear HEMT model was used. The total size of the frontend is 6 mm/spl times/6 mm including bias networks and block capacitors.<<ETX>>

Full Wave Analysis for S-Parameter Calculation of Arbitrary Three-Dimensional Lossy Structures

A three dimensional complex finite difference method treatment of transmission line discontinuity problems is presented. The generalized scattering parameters can be computed for any arbitrary one port or two port structure. Dielectric and conductor losses are taken into account for the first time. The full wave analysis accounts for losses, higher order modes, and all substrat effects. The general formulation and the procedure of the method are described. Results for a gap in a coplanar transmission line, a microstrip parallel resonator and a MMIC planar resistor are presented for the lossy and non lossy case.

Nonlinear Monolithic Circuits in Coplanar Waveguide Technology for Receiver Applications up to 55 GHz

Nonlinear circuits including oscillators, frequency doublers and mixers were designed and fabricated in coplanar waveguide. techhology. For the design commercial CAD software was used with an implemented in-house nonlinear MODFET model for the active device. The 27 GHz to 54 GHz frequency doubler achieves a conversion loss of 8 dB at an input power of 5 dBm. A buffer amplifier suppresses the fundamental frequency and amplifies the doubled frequency at 54 GHz by 10 dB, thus giving a resulting conversion gain of about 2 dB. A very broadband distributed mixer was developed operating over 10 - 50 GHz RF-bandwidth with IF frequencies from several MHz to 5 GHz. The conversion gain is better than - 3 dB over the frequency range without IF amplification. A broadband distributed combiner is used to feed the RF and LO signals with an LO to RF port isolation of 20 dB.

S-Parameter Calculation of Arbitrary Three-Dimensional Lossy Structures by Finite Difference Method

A three-dimensional treatment of transmission line discontinuity problems by the finite difference method is presented. Maxwell’s equations are solved in the frequency domain by solution of a boundary value problem. The presented method allows to compute the scattering parameters of an arbitrary structure, including coupling of higher order modes. The general formulation and the procedure of the method is described. Verification calculations are given and results for different microstrip discontinuities are included for the lossy and non-lossy case.