Monocycle Pulse Research Articles

Ultra‐wideband microwave imaging for breast tumor screening using step recovery diode‐based pulse generator

SummaryThe feasibility of a multistatic imaging system built on step recovery diode (SRD)‐based pulse generator for microwave breast cancer detection is investigated to develop a low‐cost and portable non‐invasive screening device in the future. The system consists of a pulse generator, an antenna array, and a sampling oscilloscope, in which the pulse generator generates monocycle pulse with a frequency bandwidth from 510 MHz to 6.1 GHz. Experiments are performed on a breast phantom made up of a breast model using 3D printing technology and soybean oil as internal filler, without the usage of any coupling medium. Four identical omnidirectional antennas sequentially transmit ultra‐wideband (UWB) signal and collect signals scattered inside the breast phantom, and then, the interior image of the phantom is reconstructed by background subtraction method and delay and sum (DAS) imaging algorithm. The system can successfully detect and distinguish a variety of test scenarios including cancerous breast phantom containing target with different size and different depth made by iron ball and bacon and healthy breast phantom. The smallest detectable target is 3 mm bacon, with signal to clutter ratio (SCR) and signal to mean ratio (SMR) metrics of 1.63 and 7.79 dB, respectively, and positioning error and relative error of 2.2 mm and 1.7%, respectively. It proves that the proposed time‐domain imaging system is promising for scaling up the detection range of early breast cancer.

A Marx-Based Gaussian Monocycle Pulse Generator With Low Ringing Level for Ground Penetrating Radar Applications

The Gaussian pulse generator is the core component of the pulse ground penetrating radar (GPR) system, which requires high amplitude, narrow pulse width, and low ringing levels. Marx circuits are widely used to generate Gaussian pulses. However, due to the complex pulse-forming process, the high-amplitude pulses generated by conventional Marx circuits suffer from oscillation and severe ringing. In this study, a refined model of the Marx circuit based on lossy transmission line theory is proposed, which effectively reduces the oscillation and ringing level of the generated Gaussian pulses. Furthermore, a monocycle pulse-shaping network is proposed based on the short-circuit stub. The unipolar Gaussian pulse is converted into a Gaussian monocycle pulse for antenna radiation. Waveform experiment results show that the peak-to-peak value of the output pulse is 428 V, the pulse width is about 0.8 ns, and the ringing level is low at about 9%. The profile imaging result of the sand tank detection experiment further shows that the generated high-quality Gaussian monocycle pulse can provide good detection performance of underground buried targets for the pulse GPR system.

A compact ultra-wideband sub-nanosecond pulse generator with step recovery diodes

This article presents a compact ultra-wideband (UWB) sub-nanosecond monocycle pulse generator. The proposed circuit has a simple structure and low cost, and its core components are step recovery diodes (SRDs). It is composed of a power supply circuit, pulse drive circuit, short pulse-forming circuit, and pulse-shaping circuit. A transistor-based drive circuit is used to generate a drive pulse with sharp fall time. Then, a sub-nanosecond pulse width is realized through the combination of two SRDs in series and parallel. Finally, a monocycle pulse is directly formed by the inductance-based differentiator. This design achieves a full pulse width of 406 ps with a 260 mV peak-to-peak amplitude and a −10 dB bandwidth of 510 MHz to 6.1 GHz at a pulse repetition frequency of 10 MHz square waveform. The symmetry and ringing level are 96.9% and −25.3 dB, respectively, providing good symmetry and low ringing with a circuit size of 55 × 15 mm. In actual experiments, two identical UWB antennas with appropriate bandwidth are used to radiate a monopulse to breast phantoms. The results and uncertainty analyses of the test system show that there are distinguishable differences under diverse tumor phantoms and locations, proving that the proposed pulse generator is attractive for the application of UWB breast cancer detection.

Design and Analysis of Impulse Radio (IR) Based UWB Transmitter with Antenna

The use of ultra-wideband (UWB) in target detection, radar and wireless connectivity, specifically in the medical world, has attracted a lot of attention. The concept that the IR-UWB system does not necessarily require carrier signals is one of its most appealing features. IR-UWB can transmit information using short Gaussian monocycle pulses. In light of these advantages, this paper proposes a novel UWB transmitter system which consists of UWB signal generating circuits and UWB antenna, which work together to create entire UWB transmitter. It is based on impulses and has a simple architecture with low power consumption. The proposed transmitter is realized in Cadence tools with 90nm CMOS technology and proposed UWB antenna is simulated using Advanced Design System (ADS) simulator software. In addition, the transmitter circuit and the antenna are co-simulated using ADS software. The illustrated UWB transmitter uses a low-power supply and generates pulse amplitude with pulse duration of for the Gaussian monocycle pulse. Due to its increased output voltage swing and reduced power consumption when comparing to other circuits, the proposed architecture is functional and suitable for use in short-range wireless networks and medical applications.

A Reconfigurable Picosecond Pulse Generator in Non-linear Transmission Line for Impulse Radar Ultrawideband Applications

This letter presents a reconfigurable picosecond (ps) pulse generator (PG) having Gaussian and monocycle pulse shapes for impulse radar ultrawideband (IR-UWB) applications. A mixed step recovery diode (SRD) topology is used in combination with a non-linear transmission line (NLTL) and pulse-shaping circuit to realize the PG. The pulse-shaping network comprises an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> differentiator embedded with a single p-i-n diode to provide two different switchable states. This PG is capable of directly switching from a Gaussian to a monocycle pulse without resorting to the increase in pulsewidth twice of the original Gaussian pulse as deployed in the previous reconfigurable PGs. The PG based on the proposed technique has a pulse duration of almost 70 ps with a promising ringing level in both cases (Gaussian and monocycle). Moreover, not only is the implementation of this technique easy, but it can also modify the pulse into other important shapes, such as the doublet and higher order Gaussian pulses. The proposed reconfigurable PG is measured in both cases, and the results are presented in each case.

Proposal to generate a pair of intense independently tunable attosecond pulses from undulator radiation

We propose and numerically evaluate two schemes to generate a pair of extreme-ultraviolet monocycle pulses with gigawatt-level peak power, whose time delay and central wavelengths can be precisely controlled. The methods are based on coherent emission of radiation by an ultrarelativistic electron beam with a current profile given by a chirped sinusoid, which is generated through the interaction with a conventional broadband laser. The possibility to produce phase-locked attosecond pulses with independently tunable properties in the extreme-ultraviolet spectral region has the potential to significantly advance studies of charge dynamics in molecules of biological interests.

A Nonlinear Transmission Line Technique for Generating Efficient and Low-Ringing Picosecond Pulses for Ultrabroadband and Ultrafast Systems

This paper presents a nonlinear transmission line (NLTL)-based scheme to develop an efficient and low-ringing picosecond pulse generator for ultrabroadband and ultrafast system applications. The proposed NLTL scheme stems from a unique combination of single varactor diode and stacked varactor diode per NLTL cell, which is designed to exploit a significant effect of non-linearity in connection with the varactor diode. This technique generates a higher compression factor in both rise and fall time of NLTL circuits in comparison to single varactor diodes per NLTL section. This scheme is validated to work well in a triple-stacked NLTL topology by maximizing the compression factor. Two pulse generators are then developed based on the proposed concept, where a mixed SRD topology is used for gaussian pulse generation and integrated with a triple-stacked NLTL. This achieves shorter pulse durations and a higher compression capability. The use of NLTLs with triple-stacked varactor diodes in a cell is also explored theoretically and is shown to maximize the compression capability by effectively increasing the punch through, turn-on, and break down voltages. Theoretical development and simulation of two triple-stacked NLTLs based on the rise and fall time-compression are provided, and final experimental prototypes for pulse generators are fabricated and measured. It is found from measurements that the full-width half maximum (FWHM) of the rise time-compression-based pulse generator is almost 15.78ps with a ringing level of -11.29dB, while the FWHM of the fall time-compression-based pulse generator is almost 17ps with a ringing level of -8.43dB. Finally, these pulse generators are compared with the current states of the art in terms of the implemented scheme, pulse duration, FWHM, pulse shapes, and detailed ringing level. The reconfigurable capability of the pulse generators is also briefly explored, and it is shown that the proposed pulse generators can easily be reconfigured between gaussian and monocycle pulse shapes. The power spectrum of the proposed pulse generators is also presented. It is found that they are well suitable for ultra-broadband and ultrafast systems, such as Impulse Radar Ultrawideband (IR-UWB) applications, due to higher pulse compression capability, ease of integration, flexible pulse tunability, and modification to higher order gaussian waveforms.

Mono-cycle terahertz pulses from intersubband shift currents in asymmetric semiconductor quantum wells

Both second-order frequency mixing in nonlinear optical media and photoconductive antennas have provided terahertz (THz) transients in a wide parameter range. Here, we demonstrate a novel type of ultrafast nonlinear optical response in asymmetric semiconductor quantum wells, originating from electron shift currents. Resonant intersubband excitation by a femtosecond mid-infrared pulse induces a transient spatial shift of electronic charge, which leads to the emission of a mono-cycle THz pulse. This mechanism is characterized and separated from conventional difference frequency mixing by nonlinear two-dimensional THz spectroscopy. The amplitude of the THz electric field emitted by the shift current reaches several percent of the mid-infrared driving field, significantly higher than in difference frequency mixing. Changes in time structure of the THz pulse upon nonlinear saturation of intersubband absorption allow for generating tailored THz transients. The present concept can be implemented in highly compact devices driven by mid-infrared pulses at megahertz repetition rates to provide versatile THz pulses for spectroscopy and optoelectronics.

CMOS Gaussian Monocycle Pulse Transceiver for Radar-Based Microwave Imaging

A single-chip Gaussian monocycle pulse (GMP) transceiver was developed for radar-based microwave imaging by the use of 65-nm complementary metal oxide semiconductor (CMOS) technology. A transmitter (TX) generates GMP signals, whose pulse widths and -3 dB bandwidths are 192 ps and 5.9 GHz, respectively. A 102.4 GS/s equivalent time sampling receiver (RX) performs the minimum jitter, input referred noise, signal-to-nose-ratio (SNR), signal-to-noise and distortion ratio (SNDR) effective number of bits (ENOB) of 0.58 ps, 0.24 mVrms, 28.4 dB, 26.6dB and 4.1 bits, respectively. The SNR for the bandwidth of 3.6 GHz is 36.3 dB. The power dissipations of transmitter and receiver circuits are 19.79 mW and 48.87 mW, respectively. The GMP transceiver module can differentiate two phantom targets with the size of 1 cm and the spacing of 1 cm by confocal imaging.

Wideband Rapidly Tunable Delay-Controlled Optoelectronic Oscillator

With the recent advancements in photonic integrated circuits, integrated RF photonics has increasingly been considered as a viable avenue to meet the demands of many emerging applications in telecommunication, sensing and signal processing. In this paper, an integrated, rapidly tunable, wideband optical delay line is used to implement an optoelectronic oscillator that can be continuously tuned from 594 MHz to 634 MHz. The oscillator exhibits a relatively flat modulation response at high frequencies (larger than 400 MHz), accommodating wideband fast frequency chirp generation with applications in radar and imaging. The on-chip variable delay line is characterized by continuously delaying an ultra-wide band 0.5-5 GHz monocycle pulse between 0-100 ps. The photonic integrated chip consists of silicon nanowaveguides, phase modulators, multimode interference coupler, a Mach-Zehnder interferometer, and a photodiode. The chip is fabricated on IME 180 nm Silicon Photonics platform and has an area of 0.55 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Ultra-Wideband Signal Generation Based on a Silicon Segmented Mach-Zehnder Modulator

In this paper, we demonstrate a method to generate a low-chirp ultra-wideband pulse (UWB) signal based on a silicon single-drive push-pull segmented Mach-Zehnder modulator (SMZM). The concept is analyzed theoretically and demonstrated experimentally. We get positive monocycle pulses with different relative time delays between the two driving signals. The center frequency and fractional bandwidth of the generated positive monocycle pulse is 5.97 GHz and 161% with a relative time delay of 56 ps. By changing the operating point of the SMZM, we can get negative monocycle pulses. We modulate the UWB signals with on-off keying and pulse position formats by properly coding the driving signal. As far as we know, this is the first time to realize low-chirp UWB signals using only one silicon modulator. The successful generation of UWB signals poses a significant step in realizing a compact low-cost and low-chirp UWB generator on the silicon photonics platform.

Development of a compact monocycle pulse generator for UWB impulse radar applications

AbstractIn this paper, a compact size (16 × 16 mm) of the monocycle pulse generator is proposed for Ultrawide‐band (UWB) impulse radar applications. The proposed circuit is based on the step recovery diodes (SRDs) and has a very simple structure. It consists of a coupling part, short pulse generating part, and monocycle forming part. The performance of the pulse generator is compared against simulation results which are performed by advanced design system (ADS). The measured monocycle waveform has a pulse width of 150 ps with the tail ringing level of −11 dB and symmetry of 87%. The corresponding spectrum has a center frequency of around 2.6 GHz with −10 dB bandwidth of 4 GHz. The performance of the pulse generator is validated by analyzing the receiving waveform. The pulse width and the ringing level of the received waveform are observed to be 250 ps and −11 dB, respectively. The developed compact monocycle pulse generator is very attractive because of the ease of integration into the limited physical space inside the UWB system.

Ultra-wideband doublet signal generation with tunable notch band based on delay-line filter

ABSTRACT A novel and simple scheme to generate Ultra-wideband (UWB) doublet signal with tunable notch band based on a tunable delay-line filter is presented. The first-order differentiation is realized by a dual-drive Mach–Zehnder modulator (DD-MZM), which differentiates the Gaussian pulses to the monocycle pulses. Subsequently, the UWB monocycle pulses are transmitted to an optical delay-line filter implemented by a balanced photo-detector and a tunable delay line for both differentiation and photodetection. Consequently, the desired UWB doublet signal can be obtained with a 10-dB bandwidth of 8.75 GHz. Besides, the polarity reversibility of the generated doublet signal is demonstrated by changing the bias voltage of the DD-MZM. Moreover, the desired notch can be introduced in the generated frequency spectrum to eliminate the interference between the existing narrowband systems and the UWB systems. And the tunability of the band-notched position is implemented by simply adjusting the delay time of the delay-line filter. The feasibility of the presented scheme is investigated by mathematical models and simulations.

Two-Stage Design of High Power UWB Monocycle Generator for Radar Sensor Applied in The Fourth Industry Revolution

This paper presents a high power monocycle generator for Radar Sensor detection in IoT application. The generator was made up of three essential parts-circuits, an avalanche transistor, an Step Recovery Diode (SRD) pulse sharping and an Monocycle Forming Network (MFN). The main idea in this work is to generate a high power monocycle pulse with a minimum of ringing in the output waveform. To overcome this challenge, a useful technique consists of introducing a twice stage of the transistor after the triggering with an overvoltage. The measurement results give an output waveform of 2.3 volts in amplitude with a minimum ringing around 3.6% in overshoot at 1 MHz, which is nearly fourfold of the peak power produced by a single transistor. The generator circuit is completely fabricated using microstrip structure technology characteristics. Good agreements between the measured and theoretical results are achieved which can consider very attractive in many application fields.

DDS-Based Flexible UWB Pulse Generator Using Anti-Nyquist Sampling Theorem

A real all-digital and all-coherent arbitrary ultra wideband pulse generator is presented. The generator is a multi-core & single-channel (MCSC) direct-digital-synthesizer (DDS) which consists of 16 sub-cores and a high speed digital analog converter AD9739. The ultra-wideband pulses are generated according to the proposed anti-Nyquist sampling theorem. Their frequencies are aliasing in the first and second Nyquist zones. By purposely aliasing the spectrum, the output bandwidth can be increased greatly. All the parameters including pulse width, bandwidth, amplitude, pulse type, pulse repeat frequency and modulation are user-controlled on-the-fly. In order to test the performance, monopole pulse, monocycle pulse and two 4th order Gaussian pulses are generated. The monopole pulse whose pulse rate can achieve 2.5 GHz has a 10% pulse width of 450 ps, a 200 mV peak amplitude and a -10 dB bandwidth of 2.15 GHz.

An Accurate and Compact High Power Monocycle Pulse Transmitter for Microwave Ultra-Wideband Radar Sensors with an enhanced SRD model: Applications for Distance Measurement for lossy materials

In This paper, a high power sub-nanosecond pulse transmitter for Ultra-wideband radar sensor is presented. The backbone of the generator is considered as a step recovery diode and unique pulse injected into the circuit, which gives rise to an ultra-wide band Gaussian pulse. The transistor driver and transmission line pulse forming the whole network are investigated in detail. The main purpose of this work is to transform a square waveform signal to a driving pulse with the timing and the amplitude parameters required by the SRD to form an output Gaussian pulse, and then into high monocycle pulses. In simulation aspect, an improved output response is required, in this way a new model of step recovery diode has been proposed as a sharpener circuit. This proposition was applied to increase the rise-time of the pulses. For a good range radar, a high amplitude pulse is indispensable, especially when it comes to penetrate thick lossy materiel. In order to overcome this challenge, a simple technique and useful solution is introduced to increase the output amplitude of the transmitter. This technique consists to connect the outputs of two identical pulse generators in parallel respecting the restrictions required. The pulse transmitter circuit is completely fabricated using micro-strip structure technology characteristics. Waveforms of the generated monocycle pulses over 10V in amplitude with 3.5 % in overshoot have been obtained. Good agreement has been achieved between measurement and simulation results.

Manipulation of Gaussian derivative pulses and vector solitons in fiber lasers with analytic modeling by the coupled complex Ginzburg–Landau equations

Both positive- and negative-polarity Gaussian monocycle and doublet pulses, for which the pulse shapes are the first and second derivatives of Gaussian functions plus some continuous-wave backgrounds respectively, are generated in a ring-cavity erbium-doped fiber laser from polarization-locked vector solitons by using passive optical technology. The pulse states are switchable and are found to be the superposition of bright and dark solitons with different widths, amplitudes, time delays, polarizations, and wavelengths. Qualitative analysis of the properties of vector solitons are performed by solving coupled complex Ginzburg–Landau equations, and analytic modeling of the fiber laser is presented. By representing the envelopes of bright soliton by sech- and dark soliton by tanh-based functions, the incoherent superposition of these two soliton components have simulated the experimental observations, and the underlying mechanisms for the formation of monocycle and doublet pulses are attributed to the polarization locking of bright and dark solitons. The theoretical modeling is used to calculate the pulse parameters of the fiber laser, and the intracavity birefringence can be estimated. The results of tunable optical vector solitons are compared with atomic solitons in the system of Bose–Einstein condensation. Since the governing equations for soliton generation in fiber lasers and Bose–Einstein condensation have many properties in common, thus the simulation and propagation of pulsating waves may open a new route to explore the classical solitary dynamics in nonlinear optics and its quantum analogy in ultracold fields.

Abstract P6-02-17: Hand-held impulse-radar detector for breast cancer: development and a pilot study

Abstract Background: Microwave breast imaging, which using the difference in the dielectric properties between breast cancer and normal breast tissue, is a painless and non-radiation method. We have created a novel hand-held prototype of breast cancer detector using impulse-radar based imaging system, and conducted a pilot clinical study. Methods: The detector consists of complementary metal-oxide-semiconductor (CMOS) integrated circuits covering the ultrawideband width from 3.1 to 10.6 GHz, which enable the generation and transmission of Gaussian monocycle pulse (GMP) trains and single port eight throw switching matrices (SP8T-SW) for controlling a 4×4 cross-shaped dome antenna array. The size of the detector was 19.1 × 17.7 × 18.8 cm. After evaluation using a breast tumor phantom and the resected breast specimens obtained through mastectomy, we recruited 5 patients with histologically confirmed breast cancers in the clinical study. The detector was placed on the breast with the patient in a supine position. The primary endpoint was a detection rate of breast cancers, and the secondary endpoints were positional accuracy and adverse event. This study was registered with the UMIN Clinical Trials Registry (UMIN000026181). Results: The three-dimensional positions of the tumors in the imaging results using a phantom and resected specimens are consistent with the results of histopathology analysis. In the clinical study, all 5 targeted breast cancers were detected and were visualized at the sites confirmed by other diagnostic modalities. Among 5 tumors, one was not detected via mammography because of heterogeneously dense breast and another was a microinvasive carcinoma of invasive tumor size 0.5 mm. No study-related adverse events occurred. Conclusions: We succeeded in creating a new device of hand-held impulse-radar detector for breast cancer. The detector has sufficient detective capability, is safe for clinical use, and might detect an early stage breast cancer. In the future, we will proceed with the development to clinical application. Citation Format: Sasada S, Masumoto N, Song H, Goda N, Kajitani K, Emi A, Kadoya T, Arihiro K, Kikkawa T, Okada M. Hand-held impulse-radar detector for breast cancer: development and a pilot study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-02-17.

All-optical regenerative technique for width-tunable ultra-wideband signal generation

We demonstrate all-optical generation of width-tunable mono-cycle pulses for ultra-wideband communication. It has been shown that the width of the mono-cycle pulses can be tuned dynamically by simply varying the power of the optical signal. We also investigate the regenerative property of the nonlinear medium-based technique for the generation of mono-cycle pulses. For the purpose of comparison, ultra-wideband mono-cycle pulses are also generated through the optical delay line-based technique. It has been demonstrated through numerical simulations that the nonlinear medium-based technique is highly resilient to amplified spontaneous emission noise that is induced over the optical signal. Furthermore, we have shown that the highly nonlinear fiber-based nonlinear medium performs better than the semiconductor optical amplifier-based medium. Bit error rate measurements are taken for different values of optical signal-to-noise ratios in order to elaborate our work.

Photonic generation of millimeter-wave ultra-wideband monocycle signal using up-conversion based on stimulated Brillouin scattering effect

We propose a novel scheme for photonic generation of millimeter-wave (MMW) ultra-wideband monocycle signal free of strong local oscillation (LO) and low-frequency component. A theory and a mathematical model are built to investigate the proposed scheme. Firstly, a differentiator is implemented using a dual-drive Mach–Zehnder modulator to attain monocycle pulses by differentiating a series of Gauss pulses. Subsequently, a dual-parallel Mach–Zehnder modulator and stimulated Brillouin scattering effect are employed to realize single-sideband modulation for up-converting the monocycle pulses to the MMW band. In the calculation, the generated signal is centered at 26 GHz with 10-dB bandwidth of 7 GHz and its power efficiency is about 50.08%. In addition, on–off keying modulation, amplitude modulation (PAM) and pulse position modulation monocycle pulses are generated. The spectrum of the generated signal meets with the FCC mask efficiently, so this technique has a potential application in MMW radar communication systems.