Donald Y. C. Lie

A Monolithic High-Efficiency 2.4-GHz 20-dBm SiGe BiCMOS Envelope-Tracking OFDM Power Amplifier

A monolithic SiGe BiCMOS envelope-tracking power amplifier (PA) is demonstrated for 802.11g OFDM applications at 2.4 GHz. The 4-mm2 die includes a high-efficiency high-precision envelope amplifier and a two-stage SiGe HBT PA for RF amplification. Off-chip digital predistortion is employed to improve EVM performance. The two-stage amplifier exhibits 12-dB gain, <5% EVM, 20-dBm OFDM output power, and an overall efficiency (including the envelope amplifier) of 28%.

Wideband envelope elimination and restoration power amplifier with high efficiency wideband envelope amplifier for WLAN 802.11g applications

This paper presents the design of a silicon bipolar Class-E wideband envelope elimination and restoration (WBEER) power amplifier with a wideband high efficiency envelope amplifier. The envelope amplifier is composed of a linear op-amp stage and a switch buck converter, which achieves high fidelity and high efficiency amplification of wideband high peak to average (PAR) envelope signals. Experimental results show that the envelope amplifier has a bandwidth of 20MHz and 50-60% efficiency. An overall EER power added efficiency (PAE) of 28% at an output power of 19 dBm was achieved for a WEAN OFDM signal at 2.4 GHz.

A SiGe Envelope-Tracking Power Amplifier With an Integrated CMOS Envelope Modulator for Mobile WiMAX/3GPP LTE Transmitters

This paper presents a SiGe envelope-tracking (ET) cascode power amplifier (PA) with an integrated CMOS envelope modulator for mobile WiMAX and 3GPP long-term evolution (LTE) transmitters (TXs). The entire ET-based RF PA system delivers the linear output power of 22.3/24.3 dBm with the overall power-added efficiency of 33%/42% at 2.4 GHz for the WiMAX 64 quadrature amplitude modulation (64QAM) and the 3GPP LTE 16 quadrature amplitude modulation, respectively. Additionally, it exhibits a highly efficient broadband characteristic for multiband applications. Compared to the conventional fixed-supply cascode PA, our ET-based cascode PA meets the WiMAX/LTE spectral mask and error vector magnitude spec at close to its P1dB compression without the need of predistortion. The SiGe PA and the CMOS envelope modulator are both designed and fabricated in the TSMC 0.35-μm SiGe BiCMOS process on the same die. This study represents an essential integration step toward achieving a fully monolithic large-signal ET-based TX for wideband wireless applications.

III-Nitride full-scale high-resolution microdisplays

We report the realization and properties of a high-resolution solid-state self-emissive microdisplay based on III-nitride semiconductor micro-size light emitting diodes (µLEDs) capable of delivering video graphics images. The luminance level of III-nitride microdisplays is several orders of magnitude higher than those of liquid crystal and organic-LED displays. The pixel emission intensity was almost constant over an operational temperature range from 100 to −100 °C. The outstanding performance is a direct attribute of III-nitride semiconductors. An energy efficient active drive scheme is accomplished by hybrid integration between µLED arrays and Si CMOS (complementary metal–oxide–semiconductor) active matrix integrated circuits. These integrated devices could play important roles in emerging fields such as biophotonics and optogenetics, as well as ultra-portable products such as next generation pico-projectors.

A highly efficient SiGe differential power amplifier using an envelope-tracking technique for 3GPP LTE applications

This paper presents a highly-efficient polar transmitter (TX) system that adopts the envelope-tacking (ET) technique with a differential SiGe power amplifier (PA) for 3GPP Long Term Evolution (LTE) applications. The differential PA was designed using a cascode topology, reaching power-added efficiency (PAE) of 50% at output power of 22dBm in continuous wave (CW) mode. The experimental data also shows that the proposed ET-based polar TX system with the cascode PA delivers 21dBm average output power with 33.6% PAE at 1.42 GHz, while also meeting the LTE 16QAM linearity specs for both error vector magnitude (EVM) and TX emission mask without the need of PA predistortion.

Design of highly-efficient wideband RF polar transmitters using Envelope-Tracking (ET) for mobile WiMAX/Wibro applications

This paper discusses both circuits and system design aspects of highly-efficient wideband RF polar transmitters for mobile WiMAX/Wibro applications using an open-loop envelope tracking (ET) technique. The design of linear-assisted switching envelope amplifier and monolithic SiGe class-E power amplifier (PA) is discussed, while the SPICE simulation results are compared with the measurement data. WiMAX/Wibro circuit and system co-design that include RF circuits and digital DSP blocks co-simulations suggest that the entire highly integrated ET-based transmit (TX) system can meet the stringent 802.16e mobile-WiMAX TX mask with 64QAM modulation and reach ∼33% peak system efficiency.

Highly Efficient and Linear Class E SiGe Power Amplifier Design

This paper discusses the design of monolithic RF broadband Class E SiGe power amplifiers (PAs) that are highly efficient and linear. Load-pull measurement data on IBM 7HP SiGe power devices have been made at 900MHz and 2.4GHz and monolithic class E PAs have been designed using these devices to achieve highest power-added-efficiency (PAE) at these frequencies. It is found that high PAE can be achieved for monolithic single-stage Class E PAs designed using high-breakdown SiGe transistors at ~65% (900MHz) and ~40% (2.4GHz), respectively, which are roughly ~10% lower than the devices maximum PAE values obtained by load-pull tests under optimal off-chip matching conditions. We have also demonstrated that monolithic SiGe class E PAs can be successfully linearized using an open-loop envelope tracking (ET) technique as their output spectra pass the stringent EDGE transmit mask with margins, achieving overall PAE of 44.4% for the linearized PA system that surpasses the < 30% PAE with commercially available GaAs Class AB PAs for EDGE applications. These promising results indicate the feasibility of realizing true single-chip wireless transceivers with on-chip RF SiGe PAs for spectrally-efficient non-constant-envelope modulation schemes

Design of Highly Efficient Wideband RF Polar Transmitters Using the Envelope-Tracking Technique

This paper discusses the design issues of highly efficient and monolithic wideband RF polar transmitters, especially the ones that use the envelope-tracking (ET) technique. Besides first reviewing the current state-of-the-art polar transmitters in the literature, three focus topics will be discussed: 1) the system-on-a-chip (SoC) design considerations of the monolithic polar transmitter using ET versus EER (envelope elimination and restoration); 2) the design of highly efficient envelope amplifier capable of achieving the high efficiency, current, bandwidth, accuracy and noise specifications required for wideband signals; and 3) the design of high-efficiency monolithic Si-based class E power amplifiers (PAs) suitable for ET-based RF polar transmitters. A design prototype of a polar transmitter using ET and a monolithic SiGe PA that passed the stringent low-band EDGE (Enhanced Data rates for GSM Evolution) transmit mask with 45% overall transmitter system efficiency will be given; the simulated data of the entire polar transmitter system is also compared against the measurement. Further investigations on how to solve the technical challenges to successfully implement linear and high-efficiency ET-based polar transmitter for broadband wireless applications such as WiBro/WiMAX are also discussed.

Design of High Efficiency Monolithic Power Amplifier With Envelope-Tracking and Transistor Resizing for Broadband Wireless Applications

This paper presents the design insights for the implementation of a fully monolithic radio frequency (RF) power amplifier (PA) using both envelope-tracking (ET) and transistor resizing techniques for long-term evolution (LTE) applications. At the low output power region, some of the power cells in the PA can be disabled to further save power consumption, thus enhancing the efficiency from a traditional ET-PA. Our ET-PA system is first realized with a two-chip solution, consisting of a high voltage envelope modulator fabricated in a 0.35 μm Bipolar-CMOS-DMOS (BCD) technology, and a differential cascode PA in a 0.35 μm SiGe BiCMOS technology. This two-chip solution of the ET-PA is to showcase the effective efficiency enhancement of using the transistor resizing method. In the second design, a CMOS envelope modulator is integrated with the cascode PA on the same die in the 0.35 μm SiGe BiCMOS technology. Some insights are demonstrated regarding the optimization of the envelope modulator specific to our cascode PA for LTE broadband signals, where the finite bandwidth and the switching frequency of the envelope modulator are considered for achieving the minimal error-vector magnitude (EVM) and spurious noise. The fully monolithic BiCMOS ET-PA reaches the maximum linear output power (Pout) of 24 dBm and 23.4 dBm with overall power-added-efficiency (PAE) of 41% and 38% for the LTE 16QAM 5 MHz and 10 MHz signals at 1.9 GHz, respectively, without needing predistortion. At the low power mode of our ET-PA, an additional PAE enhancement of 4% is obtained at Pout of 16-20 dBm by disabling some of the PA power cells. Our fully monolithic ET-PA satisfies the LTE 16QAM linearity specs with high efficiency.

High-Efficiency Silicon-Based Envelope-Tracking Power Amplifier Design With Envelope Shaping for Broadband Wireless Applications

This paper presents a highly efficient silicon-based envelope-tracking power amplifier (ET-PA) for broadband wireless applications. A pseudo-differential power amplifier (PA) is designed using two integrated SiGe power cells fabricated in a 0.35- μm SiGe BiCMOS technology with through-silicon-via (TSV). In the continuous-wave (CW) measurement, the PA achieves a saturated output power (POUT) of around 2 W with power-added efficiency (PAE) above 65% across the bandwidth of 0.7-1.0 GHz. To optimize the ET-PA system performance, several envelope shaping methods such as dc shifting, envelope scaling, envelope clipping, and envelope attenuation at back-off have been investigated carefully. A highly efficient monolithic CMOS envelope modulator (EM) integrated circuit (IC) is designed in a 0.35- μm bipolar-CMOS-DMOS (BCD) process to mate with our SiGe PA. With the LTE 16 QAM 5/10/20-MHz input signals, our ET-PA system achieves around 28 dBm linear POUT, passing the stringent LTE linearity specs such as the spectrum emission mask with an average composite system PAE of 42.3%/41.1%/40.2%, respectively. No predistortion is applied in this work.