Ultra-wideband Pulse Generator Research Articles

Photonic ultra-wideband pulse generation, hybrid modulation and dispersion-compensation-free transmission in multi-access communication systems

We propose and demonstrate a scheme for optical ultrawideband (UWB) pulse generation by exploiting a half-carrier-suppressed Mach-Zehnder modulator (MZM) and a delay-interferometer- and wavelength-division-multiplexer-based, reconfigurable and multi-channel differentiator (DWRMD). Multi-wavelength, polarity- and shape-switchable UWB pulses of monocycle, doublet, triplet, and quadruplet are experimentally generated simply by tuning two bias voltages to modify the carrier-suppression ratio of MZM and the differential order of DWRMD respectively. The pulse position modulation, pulse shape modulation, pulse amplitude modulation and binary phase-shift keying modulation of UWB pulses can also be conveniently realized with the same scheme structure, which indicates that the hybrid modulation of those four formats can be achieved. Consequently, the proposed approach has potential applications in multi-shape, multi-modulation and multi-access UWB-over-fiber communication systems.

All‐Optical Fiber Interferometer‐Based Methods for Ultra‐Wideband Signal Generation

We report two new, simple, and cost‐effective all‐optical methods to generate ultra‐wideband (UWB) impulse radio signals. The proposed methods are based on fiber‐interferometric structures, where an input pulse is split and propagates along the two interferometer arms. The interference of these pulses at the output of the interferometer leads to UWB pulse generation. A theoretical analysis is provided and some relevant simulation results are presented. Large bandwidths are obtained while satisfying the requirements of the Federal Communication Commission (FCC). With these two techniques, UWB pulses can be readily generated and cost‐effectively propagated through optical fibers.

Ultra-Wideband Generation Based on Cascaded Mach–Zehnder Modulators

A simple approach to generating ultra-wideband (UWB) pulses with a single optical carrier is proposed and demonstrated. The approach is realized by using a single laser diode (LD) and two cascaded Mach-Zehnder modulators (MZMs). In the experiment, the two MZMs are biased at opposite slopes of their modulation curves respectively and the time delay between them is variable. Negative monocycle pulses with a center frequency of 4.3 GHz and a fractional bandwidth of 165%, and positive monocycle pulses with a center frequency of 4.3 GHz and a fractional bandwidth of 188% are generated, respectively. The feasibility of high order UWB pulses generation with a single optical carrier is also discussed.

Impulse radio ultrawideband pulse shaper based on a programmable photonic chip frequency discriminator

We report and experimentally demonstrate the generation of impulse radio ultrawideband (UWB) pulses using a photonic chip frequency discriminator. The discriminator consists of three add-drop optical ring resonators (ORRs) which are fully programmable using thermo-optical tuning. This discriminator chip in combination with a phase modulator forms a temporal differentiator where phase modulation is converted to intensity modulation (PM-IM conversion). By means of tailoring the discriminator response using either the individual or the cascade of drop and through responses of the ORRs, first-order or second-order temporal differentiations are obtained. Using this principle, the generation of UWB monocycle, doublet and modified doublet pulses are demonstrated. The use of this CMOS-compatible discriminator is promising for the realization of a compact and low cost UWB transmitter.

Simulation analysis of a photonic ultrawideband pulse generator by using a dual-parallel Mach–Zehnder modulator

This study analyzes a photonic ultrawideband pulse generator by using a dual-parallel Mach-Zehnder modulator. A simple configuration capable of generating two popular types of ultrawideband pulse shape, Gaussian monocycle and doublet, is proposed. The generated ultrawideband pulses have very high quality, and the exact waveform is tunable with respect to parameter settings. By changing the time delay between two-path driving pulses applied to the upper and lower sub-Mach-Zehnder modulator of the dual-parallel Mach-Zehnder modulator, the generated ultrawideband pulses can be switched from Gaussian monocycle to doublet. The proposal is first analyzed and then validated by simulations. Results of the study demonstrate that it can offer a realistic solution to photonic ultrawideband pulse generation.

Photonic Generation of UWB Pulses Using a Nonlinear Optical Loop Mirror and Its Distribution Over a Fiber Link

A novel approach is proposed for generating ultra-wideband (UWB) doublet pulses using a nonlinear optical loop mirror (NOLM). In this scheme, a polarization controller is used to shift the NOLM transfer function so that for a fixed operating condition (pump power), we can access the nonlinear portion of the transfer function. The UWB doublet pulses are then modulated using on-off keying and transmitted over a 10-km span of standard single-mode fiber to assess system performance. Error-free transmission is achieved with a power penalty of 1.5 dB compared with the back-to-back measurement.

Power-efficient impulse radio ultrawideband pulse generator based on the linear sum of modified doublet pulses

We propose a new and power-efficient impulse radio ultawideband (IR-UWB) pulse design concept. The proposed concept is based on a linear sum of modified doublet pulses. The proposed concept is both simulated and experimentally demonstrated. The experimental demonstration employs a photonic scheme that generates the designed pulse using two main steps, mainly optical shaping and differential detection. The optical shaping is performed using a single electro-optic modulator biased in the nonlinear portion of its transfer function, and the differential detection is performed using a balanced photodetector. The generated IR-UWB pulse is fully Federal Communications Commission compliant, even in the highly power-restricted global positioning system band. The proposed optical scheme has potential to be integrated on a compact optical chip and thus suitable for reliable, low-cost, high-speed, short-range UWB wireless access, such as in-building networks.

Photonic Ultrawideband Pulse Generation With HNL-DSF-Based Phase and Intensity Modulator

We propose and experimentally demonstrate a photonic ultrawideband (UWB) pulse (monocycle and doublet) generator based on a highly nonlinear dispersion-shifted fiber (HNL-DSF). The pulsed pump, located in the anomalous group-velocity dispersion regime of the HNL-DSF, performs as both an intensity and a phase modulator in our scheme. We experimentally prove, for the first time to the best of our knowledge, that the UWB doublet pulse can be generated when the optical carrier is located at the center of a narrow tunable filter's passband. Furthermore, the encoded doublet signal, fully compliant with the Federal Communications Commission (FCC) regulations, is transmitted at 950 Mb/s through a 25-km single-mode fiber without introducing any obvious pulse distortion.

All-optical switchable UWB pulses generation, modulation and transmission

We proposed and demonstrated all-optical polarity- and shape-switchable ultrawideband (UWB) Gaussian pulses generation schemes using a single polarization interferometer (PI) or a semiconductor optical amplifier (SOA) cascaded by a PI. When an optical signal with dark return-to-zero (RZ) format propagates directly through a single PI, a pair of polarity-reversed UWB monocycle pulses and a positive UWB doublet pulse is acquired respectively only by adjusting the polarization controllers, without changing the bias of the intensity modulator. If a SOA is connected at the input of the PI to firstly implement the first-order differential function to the input dark RZ pulse utilizing gain saturation effect of the SOA, both polarity- and shape-switchable UWB Gaussian monocycle and doublet pulses are all acquired from the cascaded system. Moreover, if a nonreturn-to-zero control signal is introduced into the SOA, utilizing the cross-gain modulation (XGM) effect of the SOA and the differential characteristic of PI, all-optical shape modulation to UWB signals can be realized, and the polarity of the modulated UWB pulses can also be switched. Also, UWB signal transmission characteristics in fiber link were investigated.

DESIGN AND ANALYSIS OF HIGH-VOLTAGE HIGH-EFFICIENCY ULTRA-WIDEBAND PULSE SYNTHESIZER

A novel ultra-wideband (UWB) pulse synthesizer is proposed, which uses a distributed amplifler to combine Gaussian pulses of difierent polarities, amplitudes and delays. The center frequency and bandwidth of the synthesized pulse can be adjusted by varying the number of the Gaussian pulses and the delays between them. Compared to other UWB pulse generators, the present synthesizer is capable of higher voltages and higher e-ciencies. Using 0.25-m pHEMTs, a prototype synthesizer has been designed and fabricated with a center frequency of 4.0GHz and a bandwidth of 1.9GHz. Under a Gaussian input pulse of 1.5V and 100ps, the synthesizer outputs into 50› a pulse of 4.5V and 1ns. At a pulse- repetition frequency of 10MHz, the synthesizer consumes 1mA at 3V with 17% e-ciency. Approaches to maintain high e-ciency by scaling the supply voltage for difierent input amplitudes and pulse-repetition frequencies have also been verifled experimentally.

高功率超宽谱脉冲产生实验

高功率超宽谱脉冲产生实验

Sub-Nanosecond Greater-Than-10-V Compact Tunable Pulse Generator for Low-Duty-Cycle High-Peak-Power Ultra-Wideband Applications

An ultra-wideband pulse generator was designed and fabricated in GaAs HBT IC technology. The generator includes delay and differential circuits to convert a TTL input into a Gaussian pulse signal as well as a Class-C amplifier to boost the pulse amplitude while compressing the pulse width. By adjusting the collector bias of the Class-C amplifier, the pulse amplitude can be varied linearly between 3.5 V and 11.5 V while maintaining the pulse width at 0.3 ± 0.1 nanosecond. Alternatively, by adjusting the base bias of the Class-C amplifier, the pulse width can be varied linearly between 0.25 ns and 0.65 ns while maintaining the pulse amplitude at 10 ± 1 V. Finally, the amplified Gaussian signal can be shaped into a monocycle signal by anL-Cderivative circuit. The present pulse generator compares favorably with pulse generators fabricated in CMOS ICs, step-recovery diodes, or other discrete devices.

Efficient passive low-rate pulse generator for ultra-wideband radar

The design of a passive ultra-wideband (UWB) pulse generator using cascaded sections of shunt-mode step-recovery diodes with decreasing lifetimes is presented. This pulse generator circuit generates 241 ps, 5.6 V pulses at 10 MHz pulse repetition frequency without the use of an additional amplifier. This pulse generator can be used in UWB radar systems that require sub-nanosecond pulses at low pulse repetition rates.

Safe Operating Area of GaAs HBTs Based on Sub-Nanosecond Pulse Characteristics

Using a novel sub-nanosecond pulse current-voltage measurement technique, InGaP/GaAs heterojunction bipolar transistors (HBTs) were shown to survive strong impact ionization and to have a much larger safe operating area (SOA) than previously measured or predicted. As the result, an empirical model for impact ionization with both voltage and current dependence was extracted and added to a commercially available HBT model. The modified model could predict the HBT characteristics across the enlarged SOA, as well as the performance of ultra-wideband pulse generators and the ruggedness of continuous wave Class-C power amplifiers.

Ultra-wideband monocycle generation by using electroabsorption modulator and polarization differentiation method

A novel scheme of ultra-wideband pulse generation is proposed and experimentally demonstrated. The scheme is based on polarization differentiation control in an electroabsorption modulator. The optical structure is simple. Ultra-wideband monocycle pulses with a 10-dB bandwidth of 8.0 GHz have been generated. This generation system has the potential for large bandwidth, low-voltage operation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2817–2819, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25610

UWB-Over-Fiber Communications: Modulation and Transmission

The distribution of ultra-wideband (UWB) signals over optical fiber, or UWB over fiber (UWBoF), is proposed to extend the area of coverage and to offer the availability of undisrupted service across different networks. Various techniques have been reported recently for optical UWB pulse generation, but the study on the implementation of different modulation schemes based on these UWB pulses has just started. In addition, the influence of fiber dispersion on the power spectral density (PSD) of an UWB signal, and the bit-error-rate performance of an UWBoF system with different modulation schemes have not been systematically investigated. In this paper, we perform a comprehensive investigation of techniques to implement on-off keying (OOK), bi-phase modulation (BPM), pulse-amplitude modulation (PAM), pulse shape modulation (PSM), and pulse-position modulation (PPM) based on a phase modulator and an asymmetric Mach-Zehnder interferometer (AMZI). The AMZI is electrically reconfigurable by employing a polarization modulator (PolM). UWB signals with OOK, BPM, PAM, PSM, and PPM are realized by adjusting the polarization controllers in the AMZI and the amplitude of the electrical drive signal to the PolM. The UWB signals with OOK, BPM, PAM, and PSM are transmitted over a wired (single-mode fiber) and wireless link. Error-free operation is obtained for all the modulation schemes. The power penalties of transmission are less than 1.8 dB. The fiber dispersion on the PSD of the UWB signals is also theoretically studied and experimentally evaluated. An excellent agreement between the theoretical and the experimental results is achieved. The system is potentially integratable, which may provide a simple and cost-effective solution for UWBoF applications.

Simultaneous multi-channel CMW-band and MMW-band UWB monocycle pulse generation using FWM effect in a highly nonlinear photonic crystal fiber

We propose and experimentally demonstrate a scheme to simultaneously realize multi-channel centimeter wave (CMW) band and millimeter wave (MMW) band ultra-wideband (UWB) monocycle pulse generation using four wave mixing (FWM) effect in a highly nonlinear photonic crystal fiber (HNL-PCF). Two lightwaves carrying polarity-reversed optical Gaussian pulses with appropriate time delay and another lightwave carrying a 20 GHz clock signal are launched into the HNL-PCF together. By filtering out the FWM idlers, two CMW-band UWB monocycle signals and two MMW-band UWB monocycle signals at 20 GHz are obtained simultaneously. Experimental measurements of the generated UWB monocycle pulses at individual wavelength, which comply with the FCC regulations, verify the feasibility and flexibility of proposed scheme for use in practical UWB communication systems.

Design of a Tunable All-Digital UWB Pulse Generator CMOS Chip for Wireless Endoscope

A novel tunable all-digital, ultrawideband pulse generator (PG) has been implemented in a standard 0.18-¿ m complementary metal-oxide semiconductor (CMOS) process for implantable medical applications. The chip shows that an ultra-low dynamic energy consumption of 27 pJ per pulse without static current flow at a 200-MHz pulse repetition frequency (PRF) with a 1.8-V power supply and low area of 90 × 50 ¿m(2). The PG generates tunable pulsewidth, amplitude, and transmit (Tx) power by using simple circuitry, through precise timing control of the H-bridge output stage. The all-digital architecture allows easy integration into a standard CMOS process, thus making it the most suitable candidate for in-vivo biotelemetry applications.

Range Extension and Channel Capacity Increase in Impulse-Radio Ultra-Wideband Communications

We theoretically analyze the channel capacity of a 5th-order Gaussian pulse-based ultra-wideband (UWB) system and experimentally demonstrate 2 Gbit/s UWB-over-fiber transmission systems incorporating wireless transmission. Both electrical and photonic UWB pulse generation methods are employed and its performance is compared. By utilizing optimum UWB pulse design and employing a digital signal processing (DSP) receiver, a bit-error-rate above the forward error correction (FEC) limit for 8 meters of wireless emission is obtained in our photonic generation UWB system. A noticeable increase in the channel capacity is achieved compared to previously reported results.

Photonic generation of ultra-wideband signals by direct current modulation on SOA section of an SOA-integrated SGDBR laser

Photonic ultra-wideband (UWB) pulses are generated by direct current modulation of a semiconductor optical amplifier (SOA) section of an SOA-integrated sampled grating distributed Bragg reflector (SGDBR) laser. Modulation responses of the SOA section of the laser are first simulated with a microwave equivalent circuit model. Simulated results show a resonance behavior indicating the possibility to generate UWB signals with complex shapes in the time domain. The UWB pulse generation is then experimentally demonstrated for different selected wavelength channels with an SOA-integrated SGDBR laser.