A 2 W CMOS Hybrid Switching Amplitude Modulator for EDGE Polar Transmitters

This paper presents a hybrid switching amplitude modulator for class-E2 EDGE polar transmitters. To achieve both high efficiency and high speed, it consists of a wideband buffered linear amplifier as a voltage source and a PWM switching amplifier with a 2 MHz switching frequency as a dependent current source. The linear amplifier with a novel class-AB topology has a high current-driving capability of approximately 300 mA with a bandwidth wider than 10 MHz. It can also operate on four quadrants with very low output impedance of about 200 at the switching frequency attenuating the output ripple voltage to less than 12 . A feedforward path, a PWM control, and a third-order ripple filter are used to reduce the current burden of the linear amplifier. The output voltage of the hybrid modulator ranges from 0.4 to 3 V for a 3.5 V supply. It can drive an RF power amplifier with an equivalent impedance of 4 up to a maximum output power of 2.25 W with a maximum efficiency of 88.3%. The chip has been fabricated in a 0.35 m CMOS process and occupies an area of 4.7 .     

Master–Slave Predictive Current-Tracking Approach in Multiswitching Systems

This paper deals with an innovative approach to control multiswitching converters. The proposed modulation strategy directly controls the external current. Once the switching action is decided by a master routine, the choice of which leg has to be effectively switched is demanded to a separate slave routine. An acceleration algorithm and a maximum leg current protection are also considered. Under the proposed approach, the system bandwidth is related to the global switching frequency equal to the valve frequency multiplied by the number of valves. Consequently, both system dynamics and accuracy over external current are greatly improved. An unconventional predictive current-tracking technique, characterized by constant overall switching frequency and high dynamic performances, is discussed for a single switching element and extended to multiswitching systems. Details of the proposed control, simulation, and experimental results are reported.      

Fault-Tolerant Master–Slave Synchronization for Lur'e Systems Using Time-Delay Feedback Control

This paper deals with fault-tolerant master–slave synchronization for Lur'e systems using time-delay feedback control. Taking a general nature of fault in the master system into account, a new synchronization scheme, namely, fault-tolerant master–slave synchronization, is proposed, by which the master–slave synchronization can be achieved no matter if the fault occurs or not. By making use of an observer-based fault estimator and a modified time-delay feedback controller, the fault-tolerant master–slave synchronization is formulated so as to discuss the global asymptotic stability of the error system and the bound of energy gain from fault to state and fault estimation error vectors. Some new delay-dependent criteria are derived to analyze the synchronization error system, and based on the analysis results, a sufficient condition on the existence of such a master–slave synchronization scheme and a solution to the controller and fault-estimator gain matrices are obtained in terms of linear matrix inequalities. Finally, a Chua's circuit is used to illustrate the effectiveness of the proposed method.      

Master–Slave Current-Sharing Control of a Parallel DC–DC Converter System Over an RF Communication Interface

Using analog wireless communication, we demonstrate a master-slave load-sharing control of a parallel dc-dc buck converter system, thereby eliminating the need for physical connection to distribute the control signal among the converter modules. The current reference for the slave modules is provided by the master module using radio-frequency (RF) transmission, thereby ensuring even sharing of the load current. The effect of delay due to RF transmission on system stability and performance is analyzed, and regions of operation for a stable as well as satisfactory performance are determined. We experimentally demonstrate a satisfactory performance of the master-slave converter at 20-kHz switching frequency under steady state as well as transient conditions in the presence of a transmission delay. The proposed control concept, which can potentially attain redundancy that is achievable using a droop method, may lead to more robust and reconfigurable control implementation of distributed converters and power systems. It may also be used as a (fault-tolerant) backup for wire-based control of parallel/distributed converters.     

A 1.9-GHz Triple-Mode Class-E Power Amplifier for a Polar Transmitter

A 1.9-GHz CMOS power amplifier for polar transmitters was implemented with a 0.25-mum radio frequency CMOS process. All the matching components, including the input and output transformers, were fully integrated. The concepts of mode locking and adaptive load were applied in order to increase the efficiency and dynamic range of the amplifier. The amplifier achieved a drain efficiency of 33% at a maximum output power of 28dBm. The measured dynamic range was 34dB for a supply voltage that ranged from 0.7 to 3.3V. The measured improvement of the low power efficiency was 140% at an output power of 16dBm     

A Wideband ΔΣ Digital-RF Modulator for High Data Rate Transmitters

A wideband software-defined digital-RF modulator targeting Gb/s data rates is presented. The modulator consists of a 2.625-GS/s digital DeltaSigma modulator, a 5.25-GHz direct digital-RF converter, and a fourth-order auto-tuned passive LC RF bandpass filter. The architecture removes high dynamic range analog circuits from the baseband signal path, replacing them with high-speed digital circuits to take advantage of digital CMOS scaling. The integration of the digital-RF converter with an RF bandpass reconstruction filter eliminates spurious signals and noise associated with direct digital-RF conversion. An efficient passgate adder circuit lowers the power consumption of the high-speed digital processing and a quadrature digital-IF approach is employed to reduce LO feedthrough and image spurs. The digital-RF modulator is software programmable to support variable bandwidths, adaptive modulation schemes, and multi-channel operation within a frequency band. A prototype IC built in 0.13-mum CMOS demonstrates a data rate of 1.2 Gb/s using OFDM modulation in a bandwidth of 200 MHz centered at 5.25 GHz. In-band LO and image spurs are less than -59 dBc without requiring calibration. The modulator consumes 187 mW and occupies a die area of 0.72 mm².     

A Hybrid Silicon–AlGaInAs Phase Modulator

We demonstrate a carrier depletion phase modulator based on the hybrid silicon evanescent platform. A low temperature and robust bonding process is employed to transfer III–V epitaxial layers to patterned silicon waveguides. An external electric field is applied across the doped multiple quantum wells so that carriers are depleted, resulting in an index change. The device has a voltage-length product, ${V}_{pi }$ L, of 4 V-mm at 1550 nm. An optical bandwidth of 100 nm with an extinction ratio over 10 dB is achieved. The device can handle optical power up to 28 mW.      

24Gb/s GaAs PHEMT激光二极管/调制器驱动器

采用0.2μm GaAs PHEMT工艺设计并实现了超高速光纤通信系统用激光二极管/调制器集成驱动器电路.整个电路由带源极跟随器的两级差分放大电路、电容耦合电流放大器和输出电路组成.电路芯片面积为1.0mm×0.9mm.测试结果表明,采用单一 5V电源供电时直流功耗为1.5W,输出最高电压幅度为2.4V,电路最高工作速率高于24Gb/s,可以应用于光纤通信SDH(synchronous digital hierarchy)传输系统.     

24Gb/s GaAs PHEMT激光二极管/调制器驱动器

采用0.2μm GaAs PHEMT工艺设计并实现了超高速光纤通信系统用激光二极管/调制器集成驱动器电路.整个电路由带源极跟随器的两级差分放大电路、电容耦合电流放大器和输出电路组成.电路芯片面积为1.0mm×0.9mm.测试结果表明,采用单一+5V电源供电时直流功耗为1.5W,输出最高电压幅度为2.4V,电路最高工作速率高于24Gb/s,可以应用于光纤通信SDH(synchronous digital hierarchy)传输系统.     

A New Broad-Band Absorption Modulator for Rapid Switching of Microwave Power

This paper describes a new technique for obtaining a broad-band absorption modulator for high-speed switching or amplitude modulation of microwave power. This ferrite modulator, an outgrowth of the longitudinal-field rectangular-waveguide phase shifter, has electrical characteristics particularly desirable in a microwave switch. These include a zero-field insertion loss of approximately 0.5 db in the ON state, an isolation of greater than 60 db in the OFF state which is nearly independent of the magnetic control field in this state, and a nearly matched input impedance for all values of applied field. These electrical characteristics are nearly constant over a 30 per cent bandwidth at X band. Also, it is possible to design the amplitude modulator to have negligible phase shift at the desired operating frequency. Other characteristics of this ferrite modulator include small physical size, magnetic control fields of less than 50 oersteds, operating temperatures up to 150°C, and a capability of less than one µsec switching time.     

A Digital Envelope Modulator for a WLAN OFDM Polar Transmitter in 90 nm CMOS

A digital envelope modulator as part of a polar transmitter architecture for the 802.11a/g WLAN OFDM standards is investigated. The digital envelope modulator is quite similar to a state-of-the-art DAC design, but now it has been optimized to deal with envelope signals. A thermometer-coded envelope DAC has been implemented in a 90 nm digital CMOS process. Measurements of a test chip show the digital envelope modulator to reach an OFDM output power of 5 dBm for 54 Mb/s using 64 QAM at 2.45 GHz and fulfilling EVM specifications and in-band spectral mask requirements using just 12.7 mW from a 1.2 V supply. Combining the digital envelope modulator with an off-chip power amplifier gives an output power of 20.4 dBm, while fulfilling EVM specifications and in-band spectral mask requirements. The output power of the presented envelope DAC can be increased in a re-design by scaling device sizes. The envelope DAC is a key component in a software-defined-radio transmitter.     

Combined Linear and $Delta$-Modulated Switch-Mode PA Supply Modulator for Polar Transmitters

A combined linear and delta-modulated (DeltaM) switch-mode PA supply modulator for polar transmitters in wireless handsets is designed in a 0.25 mum CMOS process. The modulator employs a DeltaM switch-mode DC-DC buck converter to enhance the efficiency of a linear regulator at backed-off supply voltages and powers. The delta-modulator's noise-shaping characteristic, linear regulator's power supply rejection, digital pre-emphasis of the input envelope, and a closed-loop amplitude path from the PA output are simultaneously used to achieve state-of-the-art modulator performance. The presented supply modulator follows the input signal's envelope with 20 dB output dynamic range, maximum efficiency of 75.5% at an output power of 30.8 dBm, and 75 dB SFDR for envelope signals up to 4 MHz occupied RF bandwidth. For a 1625 kb/s 8 PSK RF input signal at 900 MHz, polar modulation of a commercial low-power GSM-900 PA provides 10 dB ACPR improvement.     

A 0.6-V Delta–Sigma Modulator With Subthreshold-Leakage Suppression Switches

A 0.6-V 34-$muhbox{W}$ delta–sigma modulator implemented by using a standard 0.13-$muhbox{m}$ complementary metal–oxide–semiconductor technology is presented. This brief analyzes a subthreshold-leakage current problem in switched-capacitor circuits and proposes subthreshold-leakage suppression switches to solve the problem. To verify the operation of the subthreshold-leakage suppression switches, two different fifth-order delta–sigma modulators are implemented with conventional switches and new switches. The input feedforward architecture is used to reduce the voltage swings of the integrators. A high-performance low-quiescent amplifier architecture is developed for the modulator. The modulator, with new switches, achieves a dynamic range of 83 dB, a peak signal-to-noise ratio of 82 dB, and a peak signal-to-noise-plus-distortion ratio of 81 dB in a signal bandwidth of 20 kHz. The power consumption is 34 $muhbox{W}$ for the modulator, and the core chip size is 0.33 $hbox{mm}^{2}$ .      

A 12-bit 3.125 MHz Bandwidth 0–3 MASH Delta-Sigma Modulator

We demonstrate a 12-bit 0–3 MASH delta-sigma modulator with a 3.125 MHz bandwidth in a 0.18 $muhbox{m}$ CMOS technology. The modulator has an oversampling ratio of 8 (clock frequency of 50 MHz) and achieves a peak SNDR of 73.9 dB (77.2 $~$dB peak SNR) and consumes 24 mW from a 1.8 V supply. For comparison purposes, the modulator can be re-configured as a single-loop topology where a peak SNDR of 64.5 dB (66.3 dB peak SNR) is obtained with 22 mW power consumption. The energy required per conversion step for the 0–3 MASH architecture (0.95 pJ/step) is less than half of that required by the feedback topology (2.57 pJ/step).      

Wideband, Low Driving Voltage Traveling-Wave Mach–Zehnder Modulator for RF Photonics

We report the design, fabrication, and testing of a traveling-wave Mach-Zehnder modulator on a GaAs substrate. Operating at 870-nm wavelength, we obtained an extremely low driving voltage of 0.45 V and a high measurement-instrument-limited small-signal modulation bandwidth of 18 GHz, projected to an estimated bandwidth of 50 GHz. We have also monolithically integrated photodetectors with an impulse response of 8-ps full-width at half-maximum, and a saturation power of 330 mW, giving a flexible high-performance platform for RF photonics.     

A 1.9-GHz, 1-W CMOS class-E power amplifier for wirelesscommunications

This paper presents a 1-W, class-E power amplifier that is implemented in a 0.35-μm CMOS technology and suitable for operations up to 2 GHz. The concept of mode locking is used in the design, in which the amplifier acts as an oscillator whose output is forced to run at the input frequency. A compact off-chip microstrip balun is also proposed for output differential-to-single-ended conversion. At 2-V supply and at 1.98 GHz, the power amplifier achieves 48% power-added efficiency (41% combined with the balun)     

A Power-Efficient Two-Channel Time-Interleaved ΣΔ Modulator for Broadband Applications

A two-channel time-interleaved second-order sigma-delta modulator for broadband applications including asymmetrical digital subscriber line (ADSL) is presented. The proposed two-channel SigmaDelta modulator uses a single integrator channel which does not require additional active elements for the quantizer input generation, since the integrator outputs are directly used as the input of the quantizers. As a result, the entire modulator can be implemented using only two op-amps, which is beneficial for both power consumption and area. Furthermore, this architecture is robust to channel mismatch effects and can operate with a simple clocking scheme. The SigmaDelta modulator achieves a dynamic range of 85 dB over a 1.1-MHz signal bandwidth with an effective clock frequency of 132 MHz. The circuit is implemented in 0.18-mum CMOS technology using metal-insulator-metal capacitors. The total power consumption of the SigmaDelta modulator is 5.4mW from a 1.8-V supply and occupies an active area of 1.1 mm²     

Pump–Push–Probe for Ultrafast All‐Optical Switching: The Case of a Nanographene Molecule

In the last two decades, the three‐beam pump–push–probe (PPP) technique has become a well‐established tool for investigating the multidimensional configurational space of a molecule, as it permits disclosure of precious information about the multiple and often complex deactivation pathways of the excited molecule. From the spectroscopic point of view, such a tool has revealed details about the efficiency of charge pair generation and conformational relaxation in π‐conjugated molecules and macromolecules. In addition, PPP is effectively utilized for modulating the gain signal in conjugated materials by taking advantage of the spectral overlap between stimulated emission and charge absorption in those systems. However, the relatively low stability of conjugated polymers under intense photoexcitation is a crucial limitation for their real employment in plastic optical fibers (POFs) and for signal control applications. Herein, the role of PPP for achieving ultrafast all‐optical switching in π‐conjugated systems is highlighted. Furthermore, new experimental data on optical switching of a newly synthesized nanographene molecule, namely dibenzo[hi,st]ovalene (DBOV), is reported. The superior environmental and photostability of DBOV and, in general, of graphene nanostructures can represent a great advantage for their effective applications in POFs and information and communications technology.     

Surface Mountable 10-Gb/s InP Mach–Zehnder Modulator Module for SFF Transponder

We have developed a small, surface mountable InP-based Mach-Zehnder modulator module. New designs for the electrical ports enable the modulator to be directly mounted on a printed circuit board. We demonstrated a 100-km transmission through single-mode fiber with a 10-Gb/s nonreturn-to-zero signal and a 220-km transmission with a 10-Gb/s optical duobinary signal to confirm the applicability of this device as an ultralong-haul small form factor transponder.