Polar Transmitter Research Articles

GaN HEMT Class ${\hbox{E}}^{2}$ Resonant Topologies for UHF DC/DC Power Conversion

In this paper, the design and performance of class E2 resonant topologies for dc/dc power conversion at UHFs are considered. Combining the use of RF gallium-nitride HEMT devices, both for the inverter and synchronous rectifier, with high-Q lumped-element terminating networks, peak efficiency values over 70% may be obtained. Control strategies based on carrier bursting, switching frequency modulation, or outphasing are also shown to be feasible. Taking advantage of their improved dynamic response, when compared to low-frequency more traditional switched-mode converters, a class E3 polar transmitter for the EDGE standard has been designed and tested at 770 MHz, offering an average global efficiency over 46% at 4.3 W of output power, through RF-based amplitude and phase constituting branches. Finally, the potential of such a high frequency of operation in terms of power density is explored, absorbing undesired coil parasitics for the original LC series interconnecting network in a 1-GHz design methodology.

An energy-efficient polar transmitter for IEEE 802.15.6 body area networks: system requirements and circuit designs

This article discusses the radio system requirements and design trade-offs of a low-power 2.3/2.4 GHz IEEE 802.15.6-narrowband transmitter for body area network applications. The IEEE 802.15.6 narrowband PHY adopts nonconstant envelope DPSK modulations. Transmitter architecture selection is a major challenge because it needs to provide both amplitude and phase modulation, with good efficiency and strict requirements on modulation accuracy and linearity for non-constant envelope modulations. A PLL-based polar transmitter with a Sigma-Delta digitally controlled power amplifier (ΣΔ-DPA) is employed for its excellent energy efficiency. Finally, this article discusses the circuit design considerations and implementation results. With balance between analog and digital implementation, and careful planning of the radio system, the polar transmitter presented in this article can meet all of the specifications defined in IEEE 802.15.6 with abundant margin, while having extremely low power consumption of 5.4 mW and excellent energy efficiency of 5.4 nJ/bit.

Determining the retardation of a wave plate by using spectroscopic method

A method for determining the retardation of a wave plate is presented. The method is based on polychromatic polarization interference technique. Through accurate judgment of the intersection points' wavelengths of the two orthogonal polarization transmittance spectrum curves, the apparent retardation, the absolute retardation values and the physical thickness of a wave plate can be measured at a wide spectral range from 400nm to 800nm. Experimental results show that the proposed method has very high precision. In addition, the method has a significant advantage that has high misalignment tolerance. The method reported here should have applications in fabrication and measurement of a wave plate.

P‐146L: Late‐News Poster: Development of a Photochromic Circular Polarizer for OLEDs

AbstractA photochromic circular polarizer was studied for use in organic light‐emitting‐diode displays (OLEDs). This polarizer transmits light emitted from an OLED efficiently under ambient light, extending the life and lowering the power consumption of the OLED. Under bright ambient light, the polarizer changes to a high degree of polarization and low transmittance, which maintains the contrast ratio and retains image visibility by reducing light reflection from the OLED electrodes. An outdoor experiment confirmed that the photochromic circular polarizer enhanced the contrast ratio of the OLED.

A Fully-Integrated Efficient CMOS Inverse Class-D Power Amplifier for Digital Polar Transmitters

In this work, we have demonstrated a fully-integrated, high-efficiency CMOS inverse Class-D PA. Such efficient switching amplifiers can form the core of mixed-signal polar transmitters. A comprehensive analytical framework has been developed to determine optimum component values to maximize efficiency. Operating from a 1-V supply, the PA achieves a peak efficiency of 44% without any RF process options. This is comparable to that of state-of-the-art CMOS switching PAs despite using a much simpler output matching network.

Digitally-Controlled Polar Transmitter Using a Watt-Class Current-Mode Class-D CMOS Power Amplifier and Guanella Reverse Balun for Handset Applications

A digitally-controlled polar transmitter with a watt-class CMOS power amplifier is demonstrated, implemented in a 0.15 μm RF CMOS process. Stacked FETs in a current-mode class-D configuration are used to obtain high breakdown voltage and high efficiency in the output stage, and a doughnut-shaped Guanella reverse balun is applied to achieve a 1-to-4 impedance transformation with less than 1 dB insertion loss. The amplifier has 31 dBm output power with 51% drain efficiency at 0.75 GHz frequency under single tone testing. The output stage is fed by a buck converter employing digital pulsewidth modulation with 47 MHz pulse rate synchronized with a 3 GHz clock. Digital compensation techniques were developed to maintain linearity. WCDMA HPSK modulation was demonstrated using a pulse pattern generator-based measurement bench. Overall efficiency of 26.5% was achieved while maintaining ACLRs within 3GPP specifications at 24 dBm average output power.

Design Flow for High Switching Frequency and Large-Bandwidth Analog DC/DC Step-Down Converters for a Polar Transmitter

System-on-chip requirements for energy management push both technology and design of voltage regulators to their limits. Integration constraints are added to high performance needs in terms of power efficiency and dynamic performance of the power converters. Switch-mode power supplies (SMPSs) are intended to supplant linear voltage regulators. This paper details a methodology to deal with different tradeoffs introduced by various specifications and constraints of embedded SMPSs. The design methodology is applied to the standard analog step-down SMPS architecture operating at very high switching frequency, and verified experimentally. The results are measured on test chips fabricated in standard 0.25-m BiCMOS technology, operating between 10 and 200 MHz, respectively, with a power efficiency up to 80% and a small-signal bandwidth of 1.2 and 15 MHz, respectively.

The Design of All-Digital Polar Transmitter Based on ADPLL and Phase Synchronized ΔΣ Modulator

An improved architecture of polar transmitter (TX) is presented. The proposed architecture is digitally-intensive and mainly composed of an all-digital PLL (ADPLL) for phase modulation, a 1-bit low-pass delta sigma ΔΣ modulator for envelop modulation, and a H-bridge class-D power amplifier (PA) for differential signaling. The ΔΣ modulator is clocked using the phase modulated RF carrier to ensure phase synchronization between the amplitude and phase path, and to guarantee the PA is switching at zero crossings of the output current.

A Low-Power GSM/EDGE/WCDMA Polar Transmitter in 65-nm CMOS

A low-power, multimode polar transmitter based on a two-point injection PLL with a linearized VCO is implemented in 65-nm CMOS technology. A wideband feedback loop, nested inside the PLL with negligible area and power consumption overhead, linearizes and accurately controls the tuning characteristic of the VCO, which is a key requirement when directly modulating the oscillator. Differential delay between AM-PM paths is predictable and is self-calibrated. In WCDMA mode, the transmitter achieves 42/-58-dBc ACLR at 5/10-MHz offsets, -159-dBc/Hz receive band noise, and 2.9% EVM at 0-dBm output power while drawing 40-mA from a 3.6-V battery. The DG09 battery current is 25-mA based on a typical PA gain profile and the chip active area is 0.7-mm2.

A CMOS Power Amplifier With Integrated-Passive-Device Spiral-Shaped Directional Coupler for Mobile UHF RFID Reader

A CMOS power amplifier (PA) with a compact spiral-shaped directional coupler for a mobile UHF RF identification (RFID) reader is proposed here, and its output power combiner and the directional coupler are implemented using an integrated passive device process. The two-chip solution not only enables a CMOS PA to be highly efficient, but also allows the directional coupler and the power combiner to be mounted in a compact standard package. A polar transmitter is implemented using the CMOS PA with the directional coupler to verify the operation of the proposed configuration for a UHF RFID reader. Measurements indicate that the CMOS PA with the directional coupler transmits 27.3 dBm of output with 44.6% of power-added efficiency and that the implemented polar transmitter satisfies the required UHF RFID reader specifications.

An Amplitude Resolution Improvement of an RF-DAC Employing Pulsewidth Modulation

We propose a time-domain technique that significantly improves resolution of an RF-DAC. As an alternative to resorting to various resolution improvement attempts in the amplitude domain or through quantization noise shaping, pulsewidth modulation (PWM) of a single unit switching device is employed with fine timing accuracy easily afforded by advanced CMOS technology. The PWM is categorized into centered PWM and noncentered PWM depending on the relative pulse position, and their performance and implementation methods are compared. The technique is examined in the context of a commercial EDGE polar transmitter realized in 65 nm CMOS, which employs an amplitude modulator with basic 10-bit amplitude resolution limited by the RF-DAC switching device mismatches. The proposed architectures with centered PWM and noncentered PWM achieve the worst case resolution improvement of 2.2 bits and 2.5 bits, respectively, assuming 20-ps worst case time granularity of the PWM signal controls.

A 67-GHz low-phase-noise oscillator and its application in a polar transmitter

In this paper, a low-phase-noise 67-GHz CMOS oscillator is presented. This inductorless voltage-controlled oscillator (VCO) employs a combination of standing-wave and travelling-wave oscillators to generate multi-phase outputs. A filtering technique is used to reduce the phase noise of the VCO. The oscillator achieves a tuning range of 5.2 GHz using a combination of coarse and fine tuning methods. The proposed multi-phase oscillator is designed and fabricated in a 0.13-μm CMOS process. Operating at 67 GHz, the VCO consumes 14 mW from a 1.2-V supply and achieves an output phase noise of ?95.66 dBc/Hz (?107.89 dBc/Hz) at a 1 MHz (10 MHz) offset. The chip area is 0.9 mm2. As an application example for the presented multi-phase oscillator, a polar transmitter structure is proposed. The transmitter is designed for systems that use a circular quadrature-amplitude modulation (QAM) constellation. A specific example of a 16-QAM transmitter is presented. The desired output phase is chosen by an 8-to-1 multiplexer, and a variable gain amplifier (VGA) is used to achieve the desired amplitude. Based on post-layout simulations, the 60-GHz 16-QAM transmitter consumes 43.2 mW from a 1.2-V supply.

A Polar Transmitter Using Interleaving Pulse Modulation for Multimode Handsets

This paper presents a highly efficient polar transmitter using interleaving pulse modulation for multiple communication standards. Using the proposed interleaving pulse modulation technique, a polar transmitter can suppress the odd-order output spurs deeply with a feasible value of essential sampling frequency and keep the residual spurs from falling into the receive bands. To validate the proposed technique, a prototype polar transmitter was constructed and evaluated. Using global system for mobile communications, enhanced data rates for GSM evolution, and wideband code division multiple access (WCDMA) signals at 836.5 MHz, the polar transmitter achieved 68%, 45.5%, and 41.2% power-added efficiency at output power levels of 28, 26, and 25 dBm, respectively. The measurement results were able to pass the spectral requirements defined by the respective standards without the use of any pre-distortion or calibration techniques. Moreover, the polar transmitter was able to achieve an output dynamic range of 80 dB required by the WCDMA standard.

An Efficient Mixed-Signal 2.4-GHz Polar Power Amplifier in 65-nm CMOS Technology

A 65-nm digitally modulated polar transmitter incorporates a fully integrated, efficient 2.4-GHz switching Inverse Class-D power amplifier. Low-power digital filtering on the amplitude path helps remove spectral images for coexistence. The transmitter integrates the complete LO distribution network and digital drivers. Operating from a 1-V supply, the PA has 21.8-dBm peak output power with 44% efficiency. Simple static predistortion helps the transmitter meet EVM and mask requirements of 802.11g 54-Mb/s WLAN data with 18% average efficiency.

Analysis and Design of Small-Signal Polar Transmitters for Cellular Applications

In cellular applications, open-loop small-signal polar transmitters offer several advantages such as low power consumption and small silicon area. However, due to their complexity, circuit imperfections can severely affect performance, potentially rendering them impractical to meet the challenging cellular transmitter requirements. In this paper a detailed analysis of the direct-modulated and small-signal polar transmitters for GSM/EDGE/WCMA applications are provided followed by some case studies. Several key non-idealities will be discussed and circuit level as well as architectural remedies for each will be presented. A prototype EDGE transmitter fabricated in 65 nm CMOS with an 8PSK ±400 kHz modulation spectrum of -64/63 dBc for high/low bands, and an RMS EVM of 2.5/2.0% will be discussed.

Resonant wideband polarizer with single silicon layer

We present the design, fabrication, and characterization of a guided-mode resonance polarizer operating in the telecommunication band. This polarizer consists of a single one-dimensional silicon grating layer and a glass substrate. The device is designed using inverse mathematical methods and fabricated by thin-film deposition, holographic-interference patterning, and etching. The fabricated polarizer has high transmittance for transverse-magnetic polarization and low transmittance for transverse-electric polarization over a ∼200 nm wavelength range. Its experimental extinction ratio is ∼670:1 at a central wavelength λc=1563 nm. Experimental and theoretical results are in good agreement.

Circuits and System Design of RF Polar Transmitters Using Envelope-Tracking and SiGe Power Amplifiers for Mobile WiMAX

This paper discusses the circuits and system design methodology of a highly-efficient wideband RF polar transmitter (TX) using the envelope-tracking (ET) technique for mobile WiMAX applications. Monolithic power amplifiers (PAs) are designed and fabricated in IBM 0.18 μm SiGe BiCMOS technology, and a linear-assisted switch-mode envelope amplifier is applied to modulate the PA supply voltage to form the core of the RF polar TX. Nonlinearities caused by bandwidth limitation of the envelope amplifier and timing misalignment have been investigated. When driven by WiMAX 64QAM 8.75 MHz signals, the overall PAE of our ET-based polar TX system reaches 30.5% at 17 dBm average output power, while also meeting the stringent WiMAX linearity specs without using any predistortion. When the decresting algorithm using the soft limiter is applied to the baseband, the overall PAE increases to 33%, at the expense of a higher EVM of 4.9%. Based on measurement results, our ET-based polar TX system has demonstrated excellent efficiency with good linearity for high peak-to-average ratio (PAR) broadband signals when compared with the recent literature on state-of-the-arts polar TX designs.

Polarization and incidence angle-dependent transmittance of transparent nickel electrodes with various thicknesses

The polarization and incidence angle-dependent transmittance of thin nickel film with various thicknesses deposited on glass substrates was first investigated by using a modified UV–Vis spectrometer. The thin nickel films showed relatively high uniform transmittance over a wide range of wavelengths, 300–1100 nm. The thickness-dependent dielectric and optical constants extracted from the experimental transmittance are significantly distinct from those of the thick nickel film. In particular, the p-polarized light transmittance largely increases with larger incidence angle, but the s-polarized light transmittance behavior is opposite from that of p-polarized light. The difference of the polarization-dependent transmittance increases parabolically with the incidence angle.

A Novel Approach for Mitigation of RF Oscillator Pulling in a Polar Transmitter

A novel technique for mitigation of self interference in a highly integrated SoC transmitter is presented. The interference originates from the internal power amplifier (i.e., aggressor) that leads to injection pulling of the local RF oscillator (i.e., victim). The characteristic of injection pulling was found to be dependent on the AM signal applied to the power amplifier. A hypothesis describing the mechanism of injection pulling of the local oscillator is presented. A mathematical model is developed to study the characteristics of this self interference verified then by measurements. Based on this model, a digitally controlled delay circuit is proposed and implemented in a digital polar GSM/EDGE transmitter that makes the system less susceptible to injection pulling through automatic phase adjustment between the aggressor and the victim. Compliant EVM and spectrum performance is measured on SoC fabricated in 65-nm CMOS showing the effectiveness of the proposed solution.

A Polar-Transmitter Architecture Using Multiphase Pulsewidth Modulation

This paper presents a transmitter architecture based on a pulse-modulated polar transmitter using multiphase pulsewidth modulation. The modulation to the radio-frequency input signal, instead of conventional drain modulation, significantly reduces the circuit complexity, while the multiphase modulation technique reduces the out-of-band emissions. An 836.5-MHz four-phase prototype transmitter using four class-C power amplifiers in parallel was constructed. Using the transmitter, single-phase, two-phase, and four-phase pulsewidth modulated signals were tested to verify the benefits of using the proposed multiphase architecture. Using a CDMA2000 1X signal, 46.8% efficiency at a 29-dBm output power level was measured while passing the spectral-mask requirements without using any kind of digital predistortion or calibration.