Monte Miller

High efficiency linear GaAs MMIC amplifier for wireless base station and Femto cell applications

We have demonstrated a 1W 1.8~2.2GHz high efficiency and high linearity power amplifier that was fabricated in a InGaP hetero-junction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) technology. The 2-stage power amplifier was biased at Class AB with 60mA quiescent current and showed 28dB gain. In conjunction with the linearization active bias circuit, harmonic trap circuits were incorporated with the matching networks to simultaneously achieve good bandwidth response, low distortion and low harmonic spurious output. The power amplifier exhibited a 45dBm output third-order intercept point (OIP3) at 5V power supply. This is one of the highest third-order intercept points reported given such a low quiescent current. The power amplifier can be used as a linear driver amplifier in wireless base station applications as well as an output stage in Femto cell or repeater applications.

A GaN HFET Device Technology on 3" SiC Substrates for Wireless Infrastructure Applications

This report presents a GaN HFET technology for wireless infrastructure applications. Using an optimized process, low DC-RF dispersion is seen via pulsed I-V measurements. At a drain bias of 48 V and frequency of 2.14 GHz, devices with 0.3 mm gate periphery produce 10-11 W/mm with associated PAEs in the range of 62-67%. Devices with 12.6 mm gate widths produce a saturated output power of 74 W (5.9 W/mm) with an associated power-added efficiency (PAE) of 55%. Under single-carrier W-CDMA conditions, an output power of approximately 10 W and 27% associated power-added efficiency (PAE) is realized at an ACPR of -40 dBc

Wide bandwidth GSM/WCDMA/LTE base station LNA with ultra-low sub 0.5 dB noise figure

This paper presents a highly integrated, sub 0.5 dB noise figure (NF) low noise amplifier (LNA) targeting 700/900 MHz GSM/CDMA/LTE base station receiver and tower mount antenna (TMA) applications. The amplifier is realized using a GaAs pHEMT process, and is housed in a very small 2 × 2 mm2 low cost plastic surface mount DFN style package. State-of-the art noise performance of less than 0.5 dB NF is achieved through an innovative design methodology and circuit architecture which takes full advantage of the selected GaAs device technology. This work represents one of the best matched LNA noise figures reported to-date in this frequency band. In addition to very low noise performance, the amplifier simultaneously exhibits gain greater than 21 dB, excellent linearity, and is closely matched to 50 Ω at the input and output ports. Very wide bandwidth performance from 300 MHz to beyond 1400 MHz is demonstrated, and performance within this frequency range can be further enhanced through selection of specific off-chip components.

Characterization and thermal analysis of a 48 V GaN HFET device technology for wireless infrastructure applications

This report presents the DC, pulsed I–V, small signal, and large signal characteristics of Freescale’s 48 V GaN HFET technology. Characterization of large signal performance for a 12.6 mm at 48V drain bias shows 89 W output power with an associated power density of 7.1 W/mm, linear gain of 17.5 dB, and a power-added efficiency (PAE) of 62%. Analysis of channel temperature over drain bias shows that the maximum channel temperatures at 28 V and 48 V are 107 °C and 245 °C, respectively during saturated RF operation. Data for RF drift over time on a 16.2 mm device show less than 0.2 dB of RF drift for ≫1000 hrs. of testing. This level of RF performance represents a significant ≫4 dB gain and ≫2 W/mm power density improvement over Freescale’s previously reported GaN HFET technology.

Overcoming pHEMT Linearity Dependence on Fundamental Input Tuning by Digital Pre-Distortion

In order to achieve highest possible gain and lowest input reflection coefficient, a conjugate match at the input of power transistors is desired. Unfortunately, as will be shown in this paper, such an input termination is not adequate for best linear performance of pHEMT power transistors operated in class AB. Therefore, these parameters need to be traded off against each other, if the device is used as a stand alone amplification stage. The use of digital pre-distortion allows operation of the transistor at best gain, input return loss, and linearity simultaneously.

Reduction of Low-Temperature Nonlinearities in Pseudomorphic AlGaAs/InGaAs HEMTs Due to Si-Related DX Centers

The linearity of conventional pseudomorphic AlGaAs/InGaAs/AlGaAs high-electron mobility transistors with planar doping in the AlGaAs layers is shown to degrade at low temperatures down to -40°C, as measured by the adjacent-channel power ratio under wideband code-division multiple-access modulation. A modified structure, in which the planar Si doping layers are placed within thin single GaAs quantum wells inside the AlGaAs barrier layers, eliminates this degradation. Deep-level transient spectroscopy and persistent photocapacitance measurements show that trapping on DX centers is effectively eliminated. The linearity improvements are therefore attributed to the elimination of this trapping. Self-consistent solutions of the Schro¿dinger and Poisson equations show that the transfer of the donor electrons into the channel is essentially the same in the modified and conventional structures.

High Gain, High Efficiency 12V pHEMT Power Transistors for WiMAX Applications

The combination of Freescales production pHEMT process with a self-aligned field plate, creates a device technology that delivers high gain and efficiency while meeting WiMAX linearity requirements. Compared to the standard production process, field plate devices show gain improvement of about 3 dB while other important device parameters such as power density, linearity, and efficiency are maintained. To demonstrate the improved performance of the field plate technology, three devices with total gate width of 7.2 mm, 14.4 mm, and 25.2 mm were designed and evaluated using a 64 QAM OFDM signal at 3.55 GHz. The devices delivered power of 28.5 dBm, 31.2 dBm, and 33 dBm, respectively, while meeting an EVM linearity requirement of 3%.