Ultra Wideband Signals and Systems in Communication Engineering

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

Recent advances in photonic integration have propelled microwave photonic technologies to new heights. The ability to interface hybrid material platforms to enhance light–matter interactions has led to the development of ultra-small and high-bandwidth electro-optic modulators, low-noise frequency synthesizers and chip signal processors with orders-of-magnitude enhanced spectral resolution. On the other hand, the maturity of high-volume semiconductor processing has finally enabled the complete integration of light sources, modulators and detectors in a single microwave photonic processor chip and has ushered the creation of a complex signal processor with multifunctionality and reconfigurability similar to electronic devices. Here, we review these recent advances and discuss the impact of these new frontiers for short- and long-term applications in communications and information processing. We also take a look at the future perspectives at the intersection of integrated microwave photonics and other fields including quantum and neuromorphic photonics. This Review discusses recent advances of microwave photonic technologies and their applications in communications and information processing, as well as their potential implementations in quantum and neuromorphic photonics.

Integrated microwave photonics

A new class of planar optics has emerged using subwavelength gratings with a large refractive index contrast, herein referred to as high-contrast gratings (HCGs). This seemingly simple structure lends itself to extraordinary properties, which can be designed top-down based on intuitive guidelines. The HCG is a single layer of high-index material that can be as thin as 15% of one wavelength. It can be designed to reflect or transmit nearly completely and with specific optical phase over a broad spectral range and/or various incident beam angles. We present a simple theory providing an intuitive phase selection rule to explain the extraordinary features. Our analytical results agree well not only with numerical simulations but also experimental data. The HCG has made easy fabrication of surface-normal optical devices possible, including vertical-cavity surface-emitting lasers (VCSELs), tunable VCSELs, and tunable filters. HCGs can be designed to result in high-quality-factor (Q) resonators with surface-normal output, which is promising for wafer-scale lasers and optical sensors. Spatially chirped HCGs are shown to be excellent focusing reflectors and lenses with very high numerical apertures. This field has seen rapid advances in experimental demonstrations and theoretical results. We provide an overview of the underlying new physics and the latest results of devices.

/pdf/high-contrast-gratings-for-integrated-optoelectronics-3ykfc99oae.pdf

High-contrast gratings for integrated optoelectronics

A vertical-cavity surface emitting laser (VCSEL) was invented 30 years ago. A lot of unique features can be expected, such as low-power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years, and they are now key devices in local area networks using multimode optical fibers. Also, long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area network applications. In addition, a VCSEL-based disruptive technology enables various consumer applications such as a laser mouse and laser printers. In this paper, the recent advance of VCSEL photonics will be reviewed, which include the wavelength extension of single-mode VCSELs and their wavelength integration/control. Also, this paper explores the potential and challenges for new functions of VCSELs toward optical signal processing

https://cnst.nctu.edu.tw/mbe08/abstract/6-13.30-14.00-koyama.pdf

Recent Advances of VCSEL Photonics

A photonics-assisted approach to dual-functional analog signal transmitter that can simultaneously generate radio-frequency (RF) signal and linear frequency modulation (LFM) signal is proposed and experimentally demonstrated. Two types of beat notes can be independently generated by heterodyning of two lasers in a photodiode using a 4-channel monolithic integrated distributed feedback (DFB) laser array. In this system, the frequency scanning for the analog signal is achieved by adding a saw-tooth signal modulating on DFB3. To the LFM signal, the center frequency and bandwidth can be tuned only by changing the direct current and the voltage of driving signal, respectively. In the experimental demonstration, the center frequency for the generated analog signal is ranging from 2 GHz to 35 GHz, limited only by the bandwidth of PD. The instantaneous bandwidth reaches to 10 GHz as well as the time-bandwidth product ~ 480,000 at the peak-to-peak voltage ~ 3.5 V. Dual-functional integration analog signal transmitter is possible to adapt to variable environments, with more flexible frequency tunability for multiple function and broadband bandwidth for high resolution.

Dual-Functional Transmitter for Simultaneous RF/LFM Signal Using a Monolithic Integrated DFB Array

We report a novel photonic scheme to generate background-free phase-coded microwave pulses with elimination of power fading by cascading a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) and a polarization modulator (PolM). The DP-DPMZM is driven by a radio frequency (RF) signal to generate two first-order optical sidebands with an orthogonal polarization state, while the PolM is driven by a three-level electrical coding signal. By properly adjusting the polarization state, a series of background-free frequency-doubled phase-coded microwave pulses can be generated after optical-to-electrical conversion. Benefiting from the carrier-suppressed single-sideband (CS-SSB) modulation, the proposed signal generator can suppress the chromatic-dispersion-induced power-fading effect, which has excellent potential for long-distance fiber transmission. In addition, the system can directly generate phase-coded microwave signals in pulse mode by truncating continuous wave (CW) microwave signals. Moreover, the microwave signal generator has wideband tunability since no optical filter is involved in our scheme. The proposed method was theoretically analyzed and experimentally verified. Phase-coded microwave pulses centered at 14 GHz and 19.2 GHz with a bit rate of 0.5 Gb/s were successfully generated.

/pdf/photonic-generation-of-background-free-phase-coded-microwave-1p4cnuq1.pdf

Photonic Generation of Background-Free Phase-Coded Microwave Pulses with Elimination of Power Fading

A piezoelectric ceramic photoelectric link microwave signal true time delay control device comprises a laser device, an optical modulator, piezoelectric ceramic, an optical fiber ring, a photoelectric detector, a piezoelectric ceramic control circuit and a signal generator, wherein the input end of the optical modulator is connected with the output end of the laser device; the piezoelectric ceramic is a hollow cylinder; the optical fiber ring is tightly wound on the outer surface of the piezoelectric ceramic and comprises an input end and an output end, and the input end of the optical fiber ring is connected with the output end of the optical modulator; the input end of the photoelectric detector is connected with the output end of the optical fiber ring; the control end of the piezoelectric ceramic control circuit is connected with the inner wall and the outer wall of the piezoelectric ceramic; the output end of the signal generator is connected with the control end of the optical modulator According to the device, the electrostriction effect of the piezoelectric ceramic is used, the piezoelectric ceramic is controlled to retract through a drive circuit, an optical fiber wound on the piezoelectric ceramic is stretched, and an optical signal propagation optical path in the optical fiber is modulated Furthermore, the phase and the light intensity of light output by the optical fiber and a propagation mode in a link are adjusted

Piezoelectric ceramic photoelectric link microwave signal true time delay control device

We report a photonic scheme to generate a millimeter-wave ultra-wideband (MMW-UWB) pulse based on optoelectronic oscillation (OEO). Normally, a millimeter-wave signal source is essential for the generation of a MMW-UWB pulse. The key novelty of our work is that no millimeter-wave signal source is required. The MMW-UWB pulses are directly generated by truncating an OEO signal into pulses. The principle behind the proposed scheme is analyzed in detail. A proof-of-concept experiment shows that the generated MMW-UWB pulses fit the Federal Communications Commission (FCC) spectral mask very well.

FCC-compliant millimeter-wave ultra-wideband pulse generator based on optoelectronic oscillation.

A multi-band channel encrypting switch control device is provided. The device comprises a transmission part and a receiving part. The transmission part comprises: a first controller to store a secret key and to send a digital signal; an encrypting unit to encrypt the digital signal; a multi-band transmitter to select a plurality of wavebands to transmit the encrypted signal on the plurality of wavebands under control of the secret key; and a switch. The receiving part comprises: a multi-band detector to receive the encrypted signal transmitted on the plurality of wavebands; a decrypting unit to decrypt the encrypted signal; and a second controller to store the secret key and to decide whether or not to issue a switch signal by processing the signal and making decisions using the process result. A transmission device, a receiving device, and a control method are also provided. The encrypted data is transmitted via different channels to reduce possibility of signal interception during the transmission, thereby improving security significantly.

Ninghua Zhu

Papers

Dual-Functional Transmitter for Simultaneous RF/LFM Signal Using a Monolithic Integrated DFB Array

Photonic Generation of Background-Free Phase-Coded Microwave Pulses with Elimination of Power Fading

Piezoelectric ceramic photoelectric link microwave signal true time delay control device

FCC-compliant millimeter-wave ultra-wideband pulse generator based on optoelectronic oscillation.

Multi-band channel encrypting switch control device and control method