Transmission Of Microwave Signals Research Articles

Investigation of optical fiber line with a positive transmission ratio of analog microwave signal

The influence of optical radiation power on the one-decibel compression point, harmonic distortion and dynamic range due to interference in a fiber-optic transmission line of an ultra-high frequency (microwave) signal has been studied. The line had a positive microwave signal transmission coefficient, and there were no amplification elements between the input and output. The amplification effect was achieved through the use of increased power of the carrier optical radiation and a photodetector with a high photocurrent. It has been shown that an increase in optical radiation power leads to a decrease in one-dB compression power and an increase in harmonic distortion, but an increase in optical radiation power does not lead to a change in the dynamic range of interference. It was found that the dynamic range free from interference was about 85…87 dB.

Design, simulation and manufacture of a flexible frequency selective surface based on aramid/carbon fiber woven fabric

Frequency selective surfaces (FSSs) are significant for the efficient and accurate transmission of microwave signals due to its ability to selectively shield electromagnetic (EM) waves of different frequencies. In some special scenarios, mechanical properties are vitally required. Herein, a flexible frequency selective fabric (FSF) is proposed. Different from traditional FSSs or reported FSFs, aramid/carbon fiber woven fabric serve as the flexible substrate in which carbon fiber provides functionality instead of metallic materials, and patches made of carbon fiber prepreg are periodically applied for property reinforcement. Equivalent circuit model is used to guide the basic determination of patch’s geometry, and it is further optimized via full-wave simulation software HFSS. A simulation model that reasonably reflect the correlation between structure and frequency-selection characteristic is provided, and structural factors affecting the characteristic are analyzed and discussed. Further, an FSF sample is prepared and its frequency response is measured. Measurement revealed the FSF selectively shields EM waves in the frequency range of 8.9 GHz to 11.4 GHz, and is of the bandpass-bandstop-bandpass characteristic. Benefit from EM property and flexibility, the proposed FSF has advantages in applications pursue lightweight, high strength, and require excellent EM functionality, such as aerospace and structure-EM function integrated products.

Ferromagnetic resonance measurement with frequency modulation down to 2 K.

Ferromagnetic resonance (FMR) spectroscopy is a powerful technique to study the precessional dynamics of magnetization in thin film heterostructures. It provides valuable information about the mechanisms of exchange bias, spin angular momentum transfer across interfaces, and excitation of magnons. A key desirable feature of FMR spectrometers is the capability to study magnetization dynamics over a wide phase space of temperature (T), frequency (f), and magnetic field (B). The design, fabrication, and testing of such a spectrometer, which uses frequency modulation techniques for improved detection of microwave absorption, reduces heat load in the cryostat and allows simultaneous measurements of inverse spin Hall effect (ISHE) induced dc voltages, is described in this paper. The apparatus is based on a 2-port transmitted microwave signal measurement using a grounded co-planar waveguide. The input radio frequency (RF) signal, frequency modulated at a tunable f-band, excites spin precession in the sample, and the attenuated RF signal is measured phase sensitively. The sample stage, inserted in the bore of a superconducting solenoid, allows magnetic field and temperature variability of 0 to ±5T and 2-310K, respectively. We demonstrate the working of this Cryo-FMR and ISHE spectrometer on thin films of Ni80Fe20 and Fe60Co20B20 over a wide T, B, and f phase space.

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

A photonic architecture for remote multi-parameter measurement and transmission of microwave signals is proposed and demonstrated, which utilizes a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) in the antenna unit and a dual-drive Mach-Zehnder modulator (DDMZM) in the processing unit. Doppler frequency shift (DFS) and angle of arrival (AOA) can be determined by analyzing the down-converted intermediate frequency signals. Introducing a reference signal in the processing unit ensures DFS measurement without directional ambiguity. The proposed architecture can also be applied for instantaneous frequency measurement based on down-conversion. Due to the use of optical single sideband modulation, long-distance transmission of radio frequency (RF) signals without dispersion-induced power fading can be achieved. Experiments for accurate and stable DFS and AOA measurement as well as long-distance RF signal transmission with dispersion-induced power fading are presented. The approach avoids the use of optical filters and polarization-related devices, facilitating wideband and stable operation, which is highly desirable. The proposed architecture is a potential solution for microwave photonic antenna remoting, offering support for both remote transmission and multi-parameter measurement.

Integrated lithium niobate microwave photonic processing engine.

Integrated microwave photonics (MWP) is an intriguing technology for the generation, transmission and manipulation of microwave signals in chip-scale optical systems1,2. In particular, ultrafast processing of analogue signals in the optical domain with high fidelity and low latency could enable a variety of applications such as MWP filters3-5, microwave signal processing6-9 and image recognition10,11. An ideal integrated MWP processing platform should have both an efficient and high-speed electro-optic modulation block to faithfully perform microwave-optic conversion at low power and also a low-loss functional photonic network to implement various signal-processing tasks. Moreover, large-scale, low-cost manufacturability is required to monolithically integrate the two building blocks on the same chip. Here we demonstrate such an integrated MWP processing engine based on a 4 inch wafer-scale thin-film lithium niobate platform. It can perform multipurpose tasks with processing bandwidths of up to 67 GHz at complementary metal-oxide-semiconductor (CMOS)-compatible voltages. We achieve ultrafast analogue computation, namely temporal integration and differentiation, at sampling rates of up to 256 giga samples per second, and deploy these functions to showcase three proof-of-concept applications: solving ordinary differential equations, generating ultra-wideband signals and detecting edges in images. We further leverage the image edge detector to realize a photonic-assisted image segmentation model that can effectively outline the boundaries of melanoma lesion in medical diagnostic images. Our ultrafast lithium niobate MWP engine could provide compact, low-latency and cost-effective solutions for future wireless communications, high-resolution radar and photonic artificial intelligence.

Movable Typography Inspired Tunable Meta‐Cylinder for Multi‐Directional Microwave Beam Shaping

AbstractIn this paper, a multi‐directional microwave beam shaping function through a tunable meta‐cylinder inspired by the movable typography technology is demonstrated. The meta‐cylinder is constructed with stacked identical octagonal layers. On each side wall of the octagonal layer, a 1D metasurface row is patterned. The metasurface rows on different side walls are designed to reflect microwave at different phase delays. As a result, each facet of the meta‐cylinder can be arranged into different metasurface row combinations and reflect a microwave into different beam shapes when rotating the stacked octagonal layers to different states. In addition, the rotation causes the same phase delay distribution change in all meta‐cylinder facets at the same time, therefore the meta‐cylinder can manipulate the microwave from different directions in the same way simultaneously. Based on this approach, a multi‐directional beam focusing function with tunable focal length is experimentally demonstrated. The dynamical beaming shaping of the microwave in multi‐direction will have high application potential in wireless communication and microwave signal transmission and omnidirectional antennas.

Quadruplex independent vector microwave signal transmission over 100 km using DSM and optical polarization multiplexing

Quadruplex independent vector microwave signal transmission over 100 km using DSM and optical polarization multiplexing

Research on space temperature environmental performance and technology of aerospace RF cable assembly

The aerospace RF cable assembly is an important component for the propagation of space communication signals, which can achieve impedance matching and energy transmission of microwave signal transmission paths. In addition to the requirements for a wide frequency range, low insertion loss, and low standing wave as required for conventional RF cable components, it must also possess high reliability, spatial temperature resistance, vacuum high-power transmission, and other spatial adaptability capabilities. This article primarily discusses the damage to the insulation materials of cable components under space-limit temperatures and its impact on the performance of the cable components. The problem of deterioration and even failure of the performance of aerospace RF cable components in high and low-temperature alternating environments in space has been addressed through the adoption of corresponding measures.

Wide dynamic range photodiodes for microwave photonics and comunication systems

The influence of the design of high-speed photodiodes for microwave photonics and signal transmission systems on the diode dark current is studied experimentally. It is shown that Schottky barrier photodiodes demonstrate the lowest dark currents, excelling photodiodes of the pin design. Photodiodes of 25 micron mesa diameter with the dark current average value as low as 0.4 mA have been manufactured. It is shown the dark current value is controlled by the mesa side wall leakage.

Microwave Photonics Advancements in Radar Application

Microwave photonics (MWP) Technology brings Microwave and optical domains together. Due to its extraordinary capabilities and solution especially towards generation, transmission and processing of Microwave signals, the MWP field has potential to break barrier, which was not possible with RF technology alone. MWP technologies provide new opportunities in many areas like 5G networks, Advanced Radar and Internet of things. As demand for multi-functionality and reduced size is growing in every field, Radar is no exception. Radar systems capabilities in terms of functionality, precision, response time have significantly improved in past decades. MWP technologies are one of the key factors in that. With Modern photonics technologies Radar performance in terms of Speed, resolution, coverage, precise target identification has improved drastically. To understand the photonics technologies in detail, this paper is designed, which highlights the important features of Microwave photonics techniques applied in Radar and its subsystems

Magnetoelectric gradient structures: Properties and applications

This paper is devoted to a comprehensive study on a new type of microwave structures named magnetoelectric (ME) gradient structures. These structures are studied in this paper to understand the possibilities and application principles in feasible devices. The structure under study was calculated at different values of the applied electric field and different values of the relative permittivity of the artificial dielectric layer. The layered multiferroic structure in inhomogeneous electric and magnetic fields was calculated on the basis of the previously proposed mathematical model. The eigenwaves spectrum for several considered cases was the result of the performed calculation. The concept of using ME gradient structures in the design of electronically controlled microwave devices is formed on the basis of the results of a numerical experiment. Structures of this type will preferably be used in electronically controlled devices for the directional transmission of microwave signals, as it was shown in the theoretical part of the paper.

Near-field mapping of high permittivity dielectric microwave resonator modes via optically induced conductance.

In this paper, we demonstrate a straightforward, low-cost, and high resolution optical-based method to measure the three-dimensional relative electric field magnitude in microwave circuits without the need to monitor reflected laser beams or the requirement of photoconductive substrates for the device under test. The technique utilizes optically induced conductance, where a focused laser beam excites electron-hole-pairs (EHPs) in a semiconductor thin film placed in the near-field of a microwave circuit. The generated EHPs create localized loss in the resonator and modulate the transmitted microwave signal, proportional to the local microwave electric field. As a proof of principle, several different modes of a high permittivity (ɛ ∼ 80) cylindrical dielectric resonator are mapped.

Nonreciprocal light transmission via optomechanical parametric interactions.

Nonreciprocal transmission of optical or microwave signals is indispensable in various applications involving sensitive measurements. In this paper, we study optomechanically induced directional amplification and isolation in a generic setup including two cavities and two mechanical oscillators by exclusively using blue-sideband drive tones. The input and output ports defined by the two cavity modes are coupled through coherent and dissipative paths mediated by the two mechanical resonators, respectively. By choosing appropriate transfer phases and strengths of the driving fields, either a directional amplifier or an isolator can be implemented at low thermal temperature, and both of them show bi-directional nonreciprocity working at two mirrored frequencies. The nonreciprocal device can potentially be demonstrated by opto- and electromechanical setups in both optical and microwave domains.

High-power InAlAs/InGaAs Schottky barrier photodiodes for analog microwave signal transmission

The design, manufacturing and DC and microwave characterization of high-power Schottky barrier InAlAs/InGaAs back-illuminated mesa structure photodiodes are presented. The photodiodes with 10 and 15 μm mesa diameters operate at ≥40 and 28 GHz, respectively, have the output RF power as high as 58 mW at a frequency of 20 GHz, the DC responsivity of up to 1.08 A/W depending on the absorbing layer thickness, and a photodiode dark current as low as 0.04 nA. We show that these photodiodes provide an advantage in the amplitude-to-phase conversion factor which makes them suitable for use in high-speed analog transmission lines with stringent requirements for phase noise.

Vehicle Platform Effects on Performance of Flexible, Lightweight, and Dual-Band Antenna for Vehicular Communications

This paper highlights the impact of the ground, of the vehicle surroundings and of the car body on signal transmission and reception of a dual-band microwave antenna tested on two automotive plastic parts on a convertible vehicle for cellular and Cellular - Vehicle To Everything (C-V2X) communications. The implemented antenna operates at 975 MHz and 5.5 GHz and facilitates the future vehicular communications in vehicles without steady rooftops. Four experiments are performed with the antenna placed (a) in the Satimo near field system; (b) on a stanchion at an outdoor range facility without the presence of a car; (c) at the outdoor facility in the side mirror of the convertible vehicle; and (d) on the trunk lid of the same vehicle. Antenna co- and cross- polarization radiation patterns are measured and results indicate that the ground and the vehicle’s body affect the radiation performance of the antenna. The presence of ground causes an increase in the antenna’s cross-polarization level. The reflections caused by the car’s body perturb the omni-directional radiation pattern of the antenna and may degrade the vehicular microwave signal transmission due to the presence of nulls.

Transmission of dual-chirp microwave signal over fiber with suppression chromatic-dispersion-induced power-fading based on stimulated Brillouin scattering

We report a microwave photonic link to transmit dual-chirp microwave signals over fiber based on stimulated Brillouin scattering (SBS) using a dual-polarization Mach–Zehnder modulator (DPol-MZM). The DPol-MZM is driven by a radio frequency (RF) carrier and a baseband single-chirp waveform to realize carrier-suppressed single-sideband (CS-SSB) modulation based on SBS. The dual-chirp waveforms centered at 12.4 GHz and 15.5 GHz with bandwidths of 0.4 GHz have been successfully generated. In our link, the CS-SSB modulation based on SBS is performed to overcome fiber chromatic-dispersion-induced power fading (CDIP). The proposed scheme is theoretically analyzed and experimentally verified.

Study on the Influence of Inserting Clearance on the Voltage Standing Wave Ratio in RF Connector

RF (Radio Frequency) connector has been extensively applied in the field of communication for it is a key device of transmitting microwave signals. If he RF connector end is designed improperly in dimension, a clearance will be observed after inserting, resulting in an abnormal phenomenon in the voltage standing wave ratio (VSWR) of the RF connector. This paper studied the influence of the inserting clearance of RF connector on the voltage standing wave ratio through theoretical analysis and performance simulation. Moreover, the solution to the abnormal voltage standing wave ratio was also proposed. At last, the abnormal phenomenon of voltage standing wave ratio of the connector in the inserting process was handled by means of carrying out optimization design and test validation on the RF connector.

Research on High-power Transmission Technology of Satellite Borne RF Connector

The reliability of the communication link shall be affected severely due to failure modes such as multipactor, low pressure discharge, and thermal damage that are commonly found in the RF connector when it performs high-power microwave signal transmission in the vacuum environment of outer space. This paper proposes supporting measures in respect of design against multipactor, low pressure discharge and thermal damage after analyzing mechanisms of failure modes of the RF connectors when it transmits high-power microwave signals in a vacuum environment. Upon tests, these proposed measures can effectively guarantee the reliability of the RF coaxial connector transmitting high-power signals in vacuum.

Multi-Functional Microwave Photonic Radar System for Simultaneous Distance and Velocity Measurement and High-Resolution Microwave Imaging

A photonic-assisted multi-functional radar system for simultaneous distance and velocity measurement and high-resolution microwave imaging is proposed and experimentally demonstrated by using a composite transmitted microwave signal of a single-chirped linearly frequency-modulated (LFM) signal and a single-tone microwave signal. In the system, the transmitted signal is generated via photonic frequency up-conversion based on a single integrated dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM), while the echo signals scattered from the target are de-chirped to two low-frequency signals using a microwave photonic frequency mixer. By using the two low-frequency de-chirped signals, the real-time distance and radial velocity of the moving target can be measured accurately according to the round-trip time of the echo signal and its Doppler frequency shift. Compared with the previously reported distance and velocity measurement methods, where two LFM signals with opposite chirps are used, these parameters can be obtained using only a single-chirped LFM signal and a single-tone microwave signal. Meanwhile, high-resolution inverse synthetic aperture radar (ISAR) imaging can also be realized using ISAR imaging algorithm. An experiment is performed to verify the proposed multi-functional microwave photonic radar system. An up-chirped LFM signal from 8.5 to 12.5 GHz and an 8.0 GHz single-tone microwave signal are used as the transmitted signal. The results show that the absolute measurement errors of distance and radial velocity are less than 5.9 cm and 2.8 cm/s, respectively. ISAR imaging results are also demonstrated, which proves the high-resolution and real-time ISAR imaging ability of the proposed system.

FSS Design for Improving Transmission of Microwave Signals and Wireless Security in Modern Buildings

A fractal frequency selective surface (FSS) has been presented for hard coated energy saving glass (ESG) used in modern building architecture. Without FSS, the presence of coating on ESG surface blocks the transmission of useful radio frequency (RF)/microwave signals. The FSS consists of two self-similar cross dipole elements designed in the coating to provide a low-pass response from 0 GHz to 2.1 GHz with two additional band-stop responses at 2.45 GHz and 5.25 GHz. An average transmission loss of less than 2 dB has been achieved in the low-pass band while attenuations of 36 dB and 30 dB have been achieved for 2.45 GHz and 5.25 GHz wireless local area network (WLAN) bands, respectively, providing required security. The low-pass response improves the transmission of useful RF/microwave signals. However, the amount of removed coating due to FSS design is relatively higher, but heat loss has been minimized by pasting an inexpensive thin solar film on the back side of glass. This thin film has provided additional thermal insulation with almost no blockage to transmission of useful RF/microwave signals. A detailed parametric analysis has been done and their effect on FSS structure has been described. An equivalent circuit model has also been presented for the proposed FSS structure. A finite prototype containing 7 × 7 elements have been constructed and evaluated. The measured results have been found to be in good agreement with the simulated results. The proposed FSS design is an excellent candidate for WLAN security.