Thermal-aware GaN/Si MMIC design for space applications

Abstract

Thermal stress in microwave power devices is a major issue for space applications, with a detrimental impact on the operating lifetime of MMICs on board satellites. To limit this, derating rules are applied to the maximum operating junction temperature, which however limit the potential device performance when GaN/Si technology is employed. In this framework, classical power amplifier design paradigm must be reconsidered, moving to a thermal-aware design approach. To this aim, it is crucial to have access to highly reliable thermal models of the adopted devices. This work will show that, adopting a simplified but effective thermal model and proper design strategy, GaN/Si technology can be successfully adopted for space-compliant MMIC design up to Ka-band. In particular, the preliminary design of a 10 W MMIC working in Ka-band at 36 GHz will be presented based on the 100 nm gate-length GaN/Si HEMT process from OMMIC foundry.

A 18‐23 GHz power amplifier design using approximate optimal impedance region approach for satellite downlink

“…Therefore, in the design of MMIC PAs with a strict junction temperature limit, it is necessary to start from the thermal dissipation load-pull of a transistor, take the junction temperature as an important additional constraint, and combine it with the selection of the optimal impedance region of the transistor and the synthesis of the matched impedance trajectory of MN. [16][17][18][19] In order to facilitate calculations, in this paper the equation for roughly estimating the junction temperature of the device described in References 16,17 is adopted as shown in Equations ( 13) and (14). The junction temperature constraint of a transistor can be transformed into the dissipation power (P diss ) constraint, as shown in Equation (15).…”

“…Once the topology of second harmonic matching has been obtained, its A matrix [A 2f0 ] as well as Г omn@2f0 can be calculated. Then the constraints (16) are applied under the condition of a = 1 and b = c = 0, to obtain the value of the components.…”

“…Equation ( 22) is then substituted into constraint Equation (16) while a = 0.5, b = 0.2 and c = 0.3 are chosen to obtain the values and components of each part of the fundamental matching network, which are marked on Figure 12. Figure 13 demonstrates the impedance transformation steps of the OMN and the reflection coefficients of each node at the fundamental and second harmonic frequency.…”

A high efficiency 10W MMIC PA for K-b and satellite communications

“…Considering the lower thermal conductivity of Si as compared to that of the standard silicon-carbide (SiC) typically adopted in GaN processes [26], a careful technology assessment and power budget analysis was initially carried out. In addition, an accurate thermal evaluation of the technology was performed by using Raman measurement [27].…”

“…7 together with the T j behavior of the device. The latter was evaluated relying upon the electrothermal model provided by the foundry, as discussed in [27].…”