G. Baumann

51 GHz frontend with flip chip and wire bond interconnections from GaAs MMICs to a planar patch antenna

In this paper the difference between flip chip and wire bond technology is demonstrated. Test assemblies with coplanar waveguides have been attached in flip chip and wire bond technology and measured up to 75 GHz. Further, the influence of a metallic lid on a coplanar waveguide structure is examined. To compare flip chip and wire bond interconnections, 51 GHz frontends with GaAs devices in coplanar waveguide technology have been realized. In one frontend the low noise amplifier (LNA) is connected to a planar patch antenna by wire bonding and in a second one by flip chip attachment. RF evaluations show the clear advantage of the flip chip version due to the lower insertion loss of the flip chip interconnections and the higher flexibility of mounting the MMICs directly on the back structure of the planar patch antenna, leading to reduced losses of the feedline.<<ETX>>

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/.

Evaluation of Glob Top and Underfill Encapsulated Active and Passive Structures for Millimeter Wave Applications

The protection of active devices against mechanical and environmental influences is necessary to guarantee a proper performance and life time. Packaging of the devices however is a very cost intensive factor and therefore it is very important to search for more economical packaging methods for RF-applications, too. In order to investigate the influence of epoxy encapsulation material we have characterized active and passive devices, which are wire bonded with subsequent glob top encapsulation as well as flip chip bonded with underfill encapsulation. The devices have been measured up to 70 GHz in order to evaluate the change of RF-transmission line characteristics and device parameters due to mounting and encapsulation. With a parameter extraction method the elements of an equivalent electrical circuit for the inner active device and the parasitics are determined. A change of impedance for encapsulated transmission lines of about 3 ¿ for a 50 ¿ line was found. Wire bonded devices exhibit a stronger variation of parasitics due to encapsulation in comparison to flip chip bonded devices, a reduction in Gmax of 1.2 dB and 0.2 dB at 20 GHz were found, respectively. For both HEMT and MESFET the inner device was unchanged. For MMIC and hybrid circuit packaging epoxy encapsulation is suitable even for mmwave range. For circuit design modified parameters should be considered.

Comparison of flip chip and wire bond interconnections and the technology evaluation on 51 GHz transceiver modules

On test vehicles realized in flip chip and wire bond versions, RF-measurements up to 70 GHz had been performed. The evaluation of the results shows the superiority of the flip chip mounting technology. To demonstrate the gain on system performance, two 51 GHz transmitter/receiver modules were realized, one in flip chip and one in wire bond technology. In the flip chip version the low noise amplifier (LNA) and the transmitter chip are directly flip chip mounted on the back structure of a planar patch antenna. In the wire bond version the chips were mounted on one edge of the planar patch antenna to achieve shortest wire bond connections possible. RF-evaluations show the clear advantage of the flip chip version, where a system gain of more than 7 dB could be achieved in comparison to the wire bond version. Further advantages of flip chip mounting technology are a higher reproducibility and an enhanced flexibility for design and construction. In case of transceiver modules, this higher flexibility enables to reduce the length of the feedline drastically in the flip chip version by mounting the MMICs directly on the back structure of the planar patch antenna again leading to reduced losses. The technology used for flip chip assembling consists of a substrate bumping process by Au microplating and a Au/Au-thermocompression bonding process for mounting of the MMICs.

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>>

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.