GaN C-Band HPA for Phased-Array Applications
In the UMS GH25-10 GaN MMIC technology a C-band high power amplifier (HPA) has been realized. The current design is primarily intended for use in a space-based SAR system with a center frequency of 5.4 GHz and a sweep bandwidth of 100 MHz. To enable reuse of the amplifier in other radar systems such as weather radar, a large bandwidth is required. A design bandwidth from 5 to 6 GHz has been used. Simulation and measurement data from on-wafer and mounted samples will be shown. Showing more than 50 W output power with 45% efficiency the HPA shows sufficient performance to be used in a module for state-of-the-art active electronically scanned arrays. The measured output power and efficiency are a record for MMIC amplifiers.
High Voltage Breakdown pHEMTs for C-band HPA
High Voltage Breakdown (HVB) HPA MMIC based on GaAs pHEMTs technology represents a useful way for high power RF application. To increase the breakdown voltage respect to conventional device, a field-plate (FP) gate structure is implemented in our standard 0.5 µm process. With this solution the off-state breakdown voltage of the device has been improved from 18V to 28V, while keeping constant the drain current. As expected, FP devices showed smaller drain current collapse than standard devices under pulsed DC measurement conditions and a significant increase in power density, i.e. 1.4 W/mm. To guaranty a full advantage for real HPA applications we have carried out numerical simulations, to optimise device thermal behaviour as a function of GaAs thickness and gate pitch. On the basis of this technology development, reliable and reproducible HPA have been fabricated with an output power of circa 30 W and power added efficiency (PAE) of circa 35% in the 4.9–6.1GHz frequency range. Therefore this proposed technological solution enables the realization of very high power T/R modules with reliable GaAs technology, waiting for more disruptive and less mature GaN HEMT one.
A 65 % drain efficiency GaN HEMT with 200 W peak power for 20 V to 65 V envelope tracking base station amplifier
A 200 W GaN high electron mobility transistor (HEMT) device was developed for envelope tracking (ET) base station amplifier. The device, which consists of a single die of 0.6 um-gate GaN HEMT of 43 mm gate periphery, has a saturated current of 680 mA/mm together with sufficiently high break down voltage of 300 V. We have estimated the average power efficiency of ET amplifier by using the GaN HEMT device over 20 V to 65 V drain bias range. As a result, the estimated average power efficiency reaches at 65.2%. Excellent results of RF high temperature operating life (RF-HTOL) test were also obtained. To the best of our knowledge, this is the highest drain voltage operation of the GaN HEMT device, allowing significant improvement of efficiency for ET amplifiers.