Triangular Pulse Generator Research Articles

A Digitally Controlled Multichannel Spectrally Efficient Low-Power Transceiver for Ultra-Wideband Cognitive Radio Applications

A multichannel transceiver design with low hardware complexity, flexibility and efficient spectrum use intended for Impulse Radio (IR) Ultra-Wideband (UWB) apertures, is proposed in this paper. The transceiver supports 14 channels and is implemented in TSMC CMOS process. The transmitter adopts a symmetrical triangular narrow pulse generator, a multiband LC-VCO, a mixer and a Variable-Gain Amplifier. A digital control of transmitter output power and carrier frequency is achieved by a current-steering Digital-to-Analog Converter (CS-DAC). The receiver follows the noncoherent Energy Detection (ED) scheme including Low-Noise Amplifier (LNA) which takes the benefits of the body biasing technique to further reduce power consumption, squarer and comparator. The LNA achieves high gain of up to 30[Formula: see text]dB allowing to enhance the receiver sensitivity which is [Formula: see text]83.7[Formula: see text]dBm at 25[Formula: see text]Mbps. The transmitter provides output pulses with a width of 3[Formula: see text]ns, a pulse repetition rate of 20[Formula: see text]ns and a maximum Power Spectral Density (PSD) of [Formula: see text]42[Formula: see text]dBm/MHz. The power consumptions of transmitter and receiver are 35.6[Formula: see text]pJ/bit and 0.207[Formula: see text]nJ/bit at 25[Formula: see text]Mbps, respectively. Maximizing utilization of the scarce wireless spectrum, enhancing spectral flexibility and efficiency and reducing power consumption are the main contributions brought by this work, enabling this transceiver to be able to deal with the current debate on producing single multifunctional Cognitive Radio (CR) UWB systems.

Efficient generation of triangular optical pulses in an erbium-doped chalcogenide fiber amplifier by exploiting the time transformation technique.

The time transformation (TT) technique is used to study the nonlinear pulse reshaping towards triangular pulse (TP) generation by efficiently optimizing the pulse parameters in an erbium-doped chalcogenide fiber amplifier (EDCFA), for the first time, to the best of our knowledge. The effects of input chirp parameter, optical gain, and dipole relaxation time are also depicted in the context of TP generation. The results obtained from the TT approach when compared with that from the nonlinear Schrodinger equation show excellent agreement. The study also reveals that spectral pulse doubling can be achieved at a shorter length when a pre-chirped Gaussian pulse is propagated through the proposed EDCFA.

Triangular pulse generation by using chalcogenide fibers and creation of tunable High frequency oscillations from the Interaction of reshaped pulse pair

Designing few normal dispersion chalcogenide fibers leads to obtain a Normal Dispersion Decreasing Chalcogenide Fiber with a value of group velocity dispersion (β2) varying from ∼ 240.45 ps2/km to 221.52 ps2/km and nonlinear coefficient (γ) within a range from ∼ 62.82 W−1 km−1 to 108.17 W−1 km−1 throughout a fiber length of 75 m. The so designed fiber is preferable for generation of Triangular Pulse at relatively shorter optimum length (Lopt) when compared to previously reported works. Such reshaped pairs of triangular pulses interact as their tails start to overlap while propagating through the fiber and generates high frequency (∼THz) oscillating pulse train. This frequency can be easily altered in a controlled manner by carefully changing the propagation length or the separation between the input pulse pair. The so designed fiber alongwith the optimum input pulse parameters can be potentially applied in the domain of tunable high frequency pulse generators along with many standard applications of TP.

A Multiband, Spectrally-Efficient Impulse Radio Transmitter Design with Low-Complexity CMOS Pulse Generator for IEEE 802.15.4a Application

A novel multiband impulse radio ultra-wideband (MB-IR-UWB) transmitter with an energy-efficient and low-complexity pulse generator design technique compliant with the IEEE 802.15.4a standard is investigated in this paper. This transmitter is made up of a new differential narrow triangular pulse generator, a new multiband voltage-controlled oscillator (VCO), an active mixer and a variable-gain power amplifier (PA). It operates at 14 UWB bands and generates an output signal with the duration of 3[Formula: see text]ns, more than 500[Formula: see text]MHz of channel bandwidth and more than 20[Formula: see text]dB of sidelobe suppression, while achieving an average energy efficiency of 51.36 pJ/pulse from 1.4-V supply. Improving spectral flexibility and worldwide compliance is the major contribution brought by this paper to make this circuit as a multifunction wireless device well suited for low-cost, low-power multiband applications.

A Modulator-Free Photonic Triangular Pulse Generator Based on Semiconductor Lasers

A modulator-free photonic triangular pulse generator is proposed and demonstrated based on two semiconductor lasers. In this method, a direct-modulated semiconductor laser is employed to generate a fundamental frequency component. Meanwhile, a third-order harmonic signal is generated by external optical injection together with 1/3 subharmonic microwave modulation of another semiconductor laser. After properly setting the amplitude and time delay between the fundamental and third-order harmonics, the combined signal composes a triangular waveform. The generation of a 11.4-GHz triangular pulse train is experimentally demonstrated. Without using any modulator, the proposed approach is a promising method for triangular pulse generation with low cost and simple structure.

Performance of different normal dispersion fibers to generate triangular optical pulses

To identify the best possible normally dispersive optical fibers (NDF) in view of efficient triangular pulse (TP) generation, the optimization of several passive NDFs are reported in this work. The study shows that TPs, which sustain over a reasonably good fiber length, can be generated at shorter length when higher values of dispersion and nonlinearity are considered. A suitable NDF with high value of dispersion and nonlinearity is chosen and renamed as normally dispersive highly nonlinear fiber (ND-HNLF). The fiber parameters and pulse conditions are optimized here in such a way that the pulse maintains its triangular shape throughout a longer length in transient state. A detail analysis is performed on generation and stability of triangular pulses through the ND-HNLFs in absence and in presence of gain. When compared, the ND-HNLF with gain is found to be preferable due to their lower input power requirement and lesser broadening of the output triangular pulses whereas passive ND-HNLF performs better in terms of formation of TPs at shorter length and sustainability of those pulses over moderately larger fiber length. It is also shown that the suggested fibers, competent enough to generate stable TPs can be potentially applied in the area of optical signal doubling and a new fiber based approach is mentioned as well for saw-tooth pulse formation.

Self-Oscillating Triangular Pulse Generator Based on 90° Photonic-Assisted Phase Shifter

In this letter, we proposed and experimentally demonstrated a novel self-oscillating triangular pulse generator based on a 90° photonic-assisted phase shifter. The fundamental harmonic is produced by the optoelectronic oscillation loop for generating triangular pulses. Meanwhile, the even-order harmonic suppression and the phase matching between odd-order harmonics are simultaneously realized by carrier phase-shifted double sideband modulation using a dual-parallel Mach-Zehnder modulator. Furthermore, the nine times amplitude ratio between the fundamental and third-order harmonics can be achieved by properly tuning the gain of the open oscillation loop. In the proof-of-concept experiment, self-oscillating triangular pulses with the repetition rates of 4 and 5.7 GHz are successfully generated with the phase noises of about -114 and -122 dBc/Hz at 10-kHz offset frequency. The corresponding root-mean-square errors between the generated and the ideal triangular waveforms are 5.9777e-4 and 6.0002e-4, respectively.

Full-duty triangular pulse generation based on a polarization-multiplexing dual-drive Mach-Zehnder modulator.

A simple and flexible photonic approach to generating a triangular microwave waveform using a single integrated polarization-multiplexing dual-drive Mach-Zehnder modulator (PM-DMZM) and a polarizer is proposed and demonstrated, which needs no specific large modulation indices or an optical filter. In the proposed method, one sub-Mach-Zehnder modulator (MZM) in the PM-DMZM is driven by a fundamental frequency, which generates an optical signal composed of an optical carrier and a + 1st-order sideband along one polarization direction; and the other sub-MZM is driven by a frequency tripled signal, generating an optical carrier and a -1st-order sideband along the orthogonal polarization direction. By adjusting the polarization direction of the polarizer following the PM-DMZM, which changes the power ratio of the two sidebands, optical intensity with expression corresponding to the Fourier expansion of a triangular-shaped waveform is obtained. Different from the previously reported approaches, neither specific large modulation index nor optical filtering is required, which guarantees a large operational frequency range and improved robustness. A proof-of-concept experiment is carried out. 5-GHz triangular-shaped waveform signals are successfully generated with different modulation indices.

Reconfigurable symmetric pulses generation using on-chip cascaded optical differentiators.

We report a type of programmable pulse shaping method based on cascaded frequency-detuned optical differentiators. By properly adjusting the central wavelength of each differentiator, a large variety of symmetric pulses can be generated from a transform-limited Gaussian-like pulse. We numerically and experimentally demonstrate the generation of flat-top, parabolic and triangular pulses with tunable pulse widths from a 20-ps Gaussian-like pulse, using no more than three cascaded differentiators. It can be found that as more differentiators are used, higher synthesized accuracy and larger tuning range of pulse widths can be obtained in general. Additionally, in our experiment, we design and fabricate thermally tunable delay interferometers on the silicon-on-insulator (SOI) platform to work as optical differentiators, which can help us realize the shaping system with small footprint (943μm × 395μm) and high stability.

Triangular Pulse Generation by Polarization Multiplexed Optoelectronic Oscillator

A novel triangular pulse generator is proposed based on a polarization multiplexed optoelectronic oscillator (OEO). Employing a dual-polarization modulator, the proposed OEO can simultaneously oscillate at two frequencies of $f$ and $3f$ along the two orthogonal polarizations of the same optical carrier. Thanks to the harmonic injection coupling between the two OEO oscillations, the generated two signals have an exact frequency ratio of 1:3 and can be tuned to be in phase with each other. By properly setting the amplitudes of the two signals, a triangular pulse train can be generated. The generation of a 4.44-GHz triangular pulse train is experimentally demonstrated. A very clean electrical spectrum incorporating the 4.44- and 13.32-GHz components is obtained, and the two tones have good phase noises of −100.6 dBc/Hz at 10 kHz and −99.2 dBc/Hz at 10 kHz, respectively. The generated triangular waveform is very close to an ideal waveform, and the root-mean-square error between the generated and the ideal waveforms is $5.145\times 10^{-4}$ .

Tunable triangular pulse‐generator for ISM band radar

A simple tunable triangular pulse-generator for 24 GHz ISM band pulse radar is reported, which consists of V–I converters and charge pumps where the control signals are produced by a resistive ladder, digital logic, and switches. In the proposed pulse-generator, by applying tunable input signals to the V–I converters, the amount of currents flowing through the charge pumps can be controlled without requiring the current source switching, and thus the switching noise can be avoided. Implemented in a 0.13 μm CMOS technology, measured tuning ranges of pulse-width and -amplitude are 12.7–28.5 ns and 15.0–216.1 mVpp, respectively, while dissipating 4.5 mW from a 1.5 V supply.

Photonic Generation of Triangular Pulses Based on Phase Modulation and Spectrum Manipulation

A photonic triangular pulse generation method based on spectrum manipulation of phase-modulated signals is proposed and experimentally demonstrated. A light wave is first phase modulated by a sinusoidal signal to generate optical sidebands. Then, the optical spectra are manipulated by attenuating the optical carrier and one of the first-order sidebands with the same suppression ratio. By choosing a proper modulation index, a full-duty-cycle triangular pulse train with a repetition rate equal to the frequency of the drive signal can be generated. To improve the practical feasibility and the repetition-rate tunability, the spectrum manipulation is realized using a Sagnac loop and a fiber Bragg grating (FBG). In the experiment, four full-duty-cycle triangular pulse trains with different repetition rates (3–6 GHz) are successfully generated, and the repetition rate can be further improved if larger bandwidth measuring instruments are used. In addition to the large and tunable repetition rate, the proposed scheme also features the advantages of simple structure, low cost, and freedom from bias drift.

Generation of Triangular Pulses Based on an Optoelectronic Oscillator

A novel scheme for the generation of full-duty-cycle triangular pulses based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The fundamental tone corresponding to the repetition rate of the pulses is generated by the OEO. Biasing the Mach-Zehnder modulator at the quadratic point, the small-signal gain of the OEO is maximized, while even-order harmonics in the optical intensity are suppressed. By properly setting the gain of the OEO loop, the amplitude of the first-order harmonic is nine times that of the third-order harmonic. After a 90° electrical phase shifter adjusts the phase of the electrical signal at the output of the photodetector, triangular pulses are obtained in the time domain. The oscillating frequency is tuned from 2 to 10 GHz by the yttrium-iron-garnet filter, and the phase noise of generated signal is also investigated. Triangular pulses with repetition rates of 3 and 6 GHz are successfully generated. The root-mean-square errors between the generated and the ideal triangular waveforms are 6.4927e-4 and 9.0932e-4 at 3 and 6 GHz, respectively.

Photonic generation of triangular pulses based on nonlinear polarization rotation in a highly nonlinear fiber.

We propose a novel method to generate triangular pulses based on the nonlinear polarization rotation (NPR) effect in a highly nonlinear fiber. A continuous wave probe beam is polarization-rotated by an intensity-modulated control beam via the NPR effect. A polarization-division-multiplexing emulator is exploited to split the probe beam into two orthogonally polarized states with imbalanced time delay. After detection by a photodetector, a 90° microwave phase shifter is used to compensate the phases of the fundamental and the third-order harmonic components in order to generate triangular pulses. Triangular pulses at 5 and 6 GHz with full duty cycles are experimentally generated. The root mean square errors between the generated and the simulated waveforms are 3.6e-4 and 1e-4 for triangular pulses at 5 and 6 GHz, respectively.

Triangular pulse generation using a dual-parallel Mach–Zehnder modulator driven by a single-frequency radio frequency signal

A simple scheme for the generation of full-duty-cycle triangular pulses is proposed and experimentally demonstrated using a dual-parallel Mach-Zehnder modulator driven by a single-frequency RF signal. By properly setting the bias voltages and the RF power, even-order harmonics in the optical intensity are suppressed, and the amplitude of the first-order harmonic is 9 times of that of the third-order harmonic. A periodical triangular pulse train is obtained in the time domain. 2.5, 5, and 10 GHz triangular pulse trains are experimentally generated, which verifies the feasibility of the proposed scheme.

20-pJ/Pulse 250 Mbps Low-Complexity CMOS UWB Transmitter for 3–5 GHz Applications

This letter presents a CMOS on-off keying 3-5 GHz ultra-wideband (UWB) transmitter with low complexity, low power and high speed. In the transmitter, a new differential narrow triangular pulse generator using push and pull integrating technique was designed for reducing quiescent current and common-mode interference, and a new complementary switch mode on-off voltage controlled ring oscillator (VCRO) was proposed by breaking the oscillation loop instead of breaking the power to avoid base-band energy without extra shaping filter. Without using delay resistor and capacitor in the VCRO, the transient response speed of the transmitter can be increased by only utilizing the parasitic resistances and capacitances. The design was successfully implemented with a 0.18 μm CMOS technology. The test results show that the new UWB transmitter can obtain a sidelobe rejection of more than 20 dB, a low energy consumption of 20 pJ/pulse at 250 Mbps, and a small core chip size of 0.08 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

A novel 7 Gbps low-power CMOS ultra-wideband pulse generator

In this study, a novel low-power high data rate ultra-wideband (UWB) pulse generator circuit is presented, which can be fully integrated in complementary metal oxide semiconductor (CMOS) process. The basic part of the circuit generates a UWB Gaussian monocycle pulse using the triangular pulse generation technique. A new bipolar phase shift keying pulse modulator is designed to control the polarity of the output pulses. The design includes additional functionality to make the pulse generator also applicable for transmitted reference (TR) signalling system. The circuit can generate pulses at a maximum rate of 7 giga pulse per second (Gpps) without TR pulse (TRP) and 3.5 Gpps with TRP. The generated pulses are symmetrical, each having a width of 142 ps and a peak-to-peak swing of 500 mV. The −3 dB bandwidth of the pulse spectrum is 9 GHz. The pulse generator consumes only 1.13 pJ per pulse from 1.2 V supply. The circuit is designed and simulated in 90 nm CMOS technology.

Experimental research of triangular optical pulse generation in normal dispersive fiber

Generation of triangular optical pulses in conventional normal dispersive (ND) fiber is experimentally realized using a passive nonlinear pulse shaping method based on a combination of pulse pre-chirping, group-velocity dispersion and self-phase modulation in a section of ND fiber. It is found that by optimizing the parameters of launching pulse power level and ND fiber length, high-quality triangular optical pulses with nearly constant gradients of leading and trailing edges and linear frequency chirp profiles can be obtained for a wide range of different pulse pre-chirping values. For different pulse pre-chirpings, high launch power is required for triangular optical pulse generation. The tolerance of triangular pulse formation to ND fiber length and launch power level is improved with the increase of pulse pre-chirping, which means that it is easy to obtain triangular pulses for higher pulse pre-chirping.

An Efficient Wavelength Converter Exploiting a Grating-Based Saw-Tooth Pulse Shaper

We experimentally demonstrate the generation of picosecond triangular optical pulses using a superstructured fiber Bragg grating and show experimentally that use of this pulse shape can provide a three-fold improvement in conversion efficiency relative to the use of Gaussian pulses with similar pulsewidths when used in a wavelength conversion scheme based on self-phase modulation and subsequent offset filtering.

Codesign of an impulse generator and miniaturized antennas for IR-UWB

The codesign of an impulse generator and miniaturized antennas for ultra-wideband impulse radio is described. The impulse generator, discussed by Bragga in 2004, is designed with differential outputs that are fed to the antenna, producing an optimum match of the generator to the antenna, an improved magnitude response, and reduced ringing of the radiated pulse. The impulse generator is preceded by a programmable pulse-position modulator and consists of a triangular pulse generator and a cascade of complex first-order systems, which, in turn, are made up of differential pairs employing partial positive feedback to approximate a Gaussian monocycle waveform. The complete pulse generator is fabricated in IBM 0.18-/spl mu/m Bi-CMOS IC technology. Measurements show the correct operation of the circuit for supply voltages of 1.8 V and a power consumption of 45 mW. The output pulse approximates the Gaussian monocycle having a pulse duration of about 375 ps. Proper modulation of the pulse in time is confirmed. A number of antennas with differentially fed baluns and input impedances of 100 /spl Omega/ have been designed. From measurements, it can be seen that ringing is considerably smaller as compared to conventionally fed antennas.