Outmane Lemtiri Chlieh

Design of A Transformer-Based Reconfigurable Digital Polar Doherty Power Amplifier Fully Integrated in Bulk CMOS

This paper presents a digital polar Doherty power amplifier (PA) fully integrated in a 65 nm bulk CMOS process. It achieves +27.3 dBm peak output power and 32.5% peak PA drain efficiency at 3.82 GHz and 3.60 GHz, respectively. The proposed digital Doherty PA architecture optimizes the cooperation of the main and auxiliary amplifiers and achieves superior back-off efficiency enhancement (a maximum 47.9% improvement versus the corresponding Class-B operation). This digital intensive architecture also allows in-field PA reconfigurability which both provides robust PA operation against antenna mismatches and allows flexible trade-off optimization on PA efficiency and linearity. Transformer-based passives are employed as the Doherty input and output networks. The input 90 ° signal splitter is realized by a 6-port folded differential transformer structure. The active Doherty load modulation and power combining at the PA output are achieved by two transformers in a parallel configuration. These transformer-based passives ensure an ultra-compact PA design (2.1 mm 2) and broad bandwidth (24.9% for -1 dB P out bandwidth). Measurement with 1 MSym/s QPSK signal shows 3.5% rms EVM with +23.5 dBm average output power and 26.8% PA drain efficiency. Measurement with 16-QAM signal exhibits the PAs flexibility on optimizing efficiency and linearity.

A +27.3dBm transformer-based digital Doherty polar power amplifier fully integrated in bulk CMOS

This paper presents a digital Doherty polar power amplifier fully integrated in a 65 nm bulk CMOS process. It achieves +27.3 dBm peak output power and 32.5% peak PA drain efficiency at 3.82 GHz and 3.60 GHz, respectively. The PA demonstrates a maximum 7% back-off efficiency enhancement compared with a class-B PA and shows a robust Doherty PA operation against load variations. The 90° signal splitting at the Doherty input is realized by a compact folded transformer-based differential quadrature coupler. Active Doherty load modulation and output power combining are achieved by two transformers in a parallel configuration at the PA output. The transformer-based passive networks make the PA design ultra-compact (2.1 mm2) and broadband (24.9% for -1 dB bandwidth). Measurements with QPSK (1 MSym/s)/16QAM (0.5 MSym/s) signals show 3.5/4.7% rms EVM with +23.5/+22.1 dBm average output power and 26.8/24.1% PA drain efficiency.

L-band tunable microstrip bandpass filter on multilayer organic substrate with integrated microfluidic channel

This paper presents, for the first time, a tunable microstrip microfluidic bandpass filter, with a center frequency of 1 GHz, on liquid crystal polymer (LCP). A 60 mil cavity, initially filled with distilled (DI) water (εr = 80), is placed below a 2 mil LCP layer. Based on this multilayer structure, the dimensions of microstrip lines are determined. In order to tune the filter center frequency, DI water is replaced by acetone, with a dielectric constant that is 4 times lower than that of DI water (εr = 20.7). A micropump is used to inject the different fluids and provide the necessary pressure to trap the liquid inside the microfluidic channel. Measured results show 50% tuning which translates into a maximum center frequency shift of 500 MHz. The insertion loss is 1.4 dB and the return loss is 25 dB at 1 GHz for the DI water filter while the insertion loss is 1.3 dB and the return loss is 15.8 dB at 1.5 GHz for the acetone filter.

An X-band GaN HEMT hybrid power amplifier with low-loss Wilkinson division on AlN substrate

The high-power operation of a modular and compact power amplifier (PA) is demonstrated using gallium nitride (GaN) transistors and power-combining networks implemented on an aluminum nitride (AlN) substrate. The power-combining network, tuned for X-Band operation, includes matching circuits and Wilkinson power dividers (WPDs) with tantalum nitride (TaN) thin-film resistors. PA efficiency is increased by minimizing network thermal loss with the AlN substrate, which is an excellent thermal conductor. All system components were mounted on a metal carrier, and were interconnected through gold wire bonds. Large-signal measurements showed power added efficiency (PAE) of 44% and a peak output power of 6.5 W at 9.5 GHz with a 3 dB fractional bandwidth of 14%.

Integrated microfluidic cooling for GaN devices on multilayer organic LCP substrate

This paper presents, for the first time, an integrated microfluidic cooling scheme on multilayer organic liquid crystal polymer (LCP) substrate for high power X-band gallium nitride (GaN) devices and amplifiers. The channel is micromachined on LCP and a mixture of water and ethylene glycol is used as a coolant. A 3D electro-thermal model of the microfluidic channel has been created, which illustrates the advantage of having a micro-channel beneath LCP in the case of a static and moving fluid. Measurements were done at 10.5 GHz on a GaN power amplifier (PDC = 1.68 W, PAE = 15 %) that was placed both on LCP and on a microfluidic channel with a static fluid.

Integrated microfluidic cooling of high power passive and active devices on multilayer organic substrate

This paper presents a microfluidic cooling solution for passive and active devices on liquid crystal polymer (LCP). Distilled (DI) water circulates inside a 15 mil micromachined channel and takes away the dissipated heat from passive and active heat sources. A micropump is used to provide enough pressure to inject the fluid and to ensure its circulation. A 20 W surface mount resistor is cooled with moving DI water and operated at 12.3 W at 25 °C, while this device can only dissipate 7 W at 25 °C if the DI water is static. A 5 W discrete power gallium arsenide (GaAs) die is attached to the microfluidic channel and cooled to operate at 3.45 W at 60 °C under DC operation.

A feasibility study of flip-chip packaged gallium nitride HEMTs on organic substrates for wideband RF amplifier applications

Gallium nitride (GaN) technology has emerged as a frontrunner for high power electronics applications. By performing a survey of wire-bond and flip-chip-packaged GaN HEMTs on either AlN (a ceramic with high thermal conductivity) or LCP (an organic polymer with low thermal conductivity), the thermal and electrical limits of each package are established. Flip-chip packaging has the benefit of improving the bandwidth of a hybrid PA. Dies that were wire-bonded on AlN showed best performance, and were able to dissipate more than 6 W of power while remaining below the maximum operating junction temperature. On the other hand, flip-chipped devices on LCP were severely limited by thermal effects, even at a 10% duty cycle. This study motivates the need for advanced packaging techniques, such as integrated microfluidics or backside heat-sinking, in order to make LCP a viable material for high-power applications.

Microfluidically reconfigurable GaN power amplifier on multilayer organic substrate for s-band and c-band applications

This paper presents, for the first time, a microfluidic tuning solution on a multilayer organic substrate to tune the frequency response of a GaN-based power amplifier (PA) from 2.4 GHz to 5.8 GHz and vice versa. By changing the fluid inside the matching networks microchannels, the packaged PA large signal response can be tuned allowing it to work optimally at the two specified frequencies based on the fluid in use. In this work, the fluids used are acetone and air and are meant to work for 2.4 GHz and 5.8 GHz respectively. The measured large signal data for the PA shows that Pout = 35.02 dBm, PAE = 36.41 % for Pin = 21 dBm at 2.3 GHz (acetone configuration) and Pout = 36.88 dBm, PAE = 44.03 % for Pin = 25 dBm at 5.7 GHz (air configuration). These numbers improve significantly for higher input power levels.

Microfluidic channel on organic substrates as size reducing technique for 915 MHz antenna designs

This paper presents for the first time, the use of a microfluidic channel with organic substrates to reduce the size of different antenna designs at 915 MHz (dipole and loop). The channel was created by drilling a cavity on a 50 mil RO3003™ substrate and bonding it to two 5 mil substrates in order to seal the structure. Compared to designs fabricated on an unperturbed substrate, the overall size reduction in length for the dipole with water-filled channel was ~44% (60 mm), while a 54% reduction in area was observed for its loop counterpart. Broad bandwidths of 22% and 11% were achieved for the water loaded dipole and loop, respectively. The results obtained for both designs agreed well with simulations.