Receiving Frequency Band Research Articles

The Design and Implementation of a Wide-band Circularly Polarized Conformal Antenna

Background: It gives out the design and verification of single-layer dual-band antenna unit and multi-layer dual-band broadband antenna unit of phased array antenna, and verifies that the multi-layer dual-band broadband antenna unit can meet the design requirements of the receiving frequency band. Objective: It gives out the design and implementation of a wide-band circularly polarized conformal antenna, and presents the characteristics analysis of the antenna. Method: Through related simulation methods, the proposed methods are verified and they can effectively solve the array phase compensation and beam shaping and control in the wide-band circularly polarized conformal antenna. Results: Based on the basic design of the antenna, the active superposition algorithm, phase compensation technology and particle swarm optimization antenna beam shaping technology are both studied. Conclusion: The proposed wide-band circularly polarized conformal antenna can be used in the actual application.

A tunable ultra‐wideband superheterodyne radio frequency receiver with high‐image‐rejection levels

This article presents the superheterodyne radio frequency (RF) receiver composed of two receiving channels, which can realize an ultra-wide receiving frequency band. The RF signal can be received and demodulated in a variable frequency band by controlling the voltage of RF switches, which makes the RF signal enter the appropriate frequency conversion channel and tuning the local oscillator frequency according to the RF signal frequency. Therefore, the receiver realizes the adjustable working frequency band and an ultra-wide receiving frequency band. The designed superheterodyne RF receiver is simulated, manufactured, and measured. Finally, the article achieves a tunable ultra-wideband superheterodyne RF receiver with an image-rejection architecture that can provide rejection of more than 29.0 dB. The receiving frequency band of the receiver is 2.5 GHz –12 GHz. When the proposed receiver link receives multiple types of quadrature signals with a symbol rate of 50 M Baud, the error vector magnitude is less than 1.90%.

Broadband (100 kHz – 100 MHz) ultrasound PVDF detectors for raster-scan optoacoustic angiography with acoustic resolution

Spherical ultrasonic antennas are used in raster-scan optoacoustic (OA) angiography to record broadband signals generated by haemoglobin molecules in blood when they absorb pulsed optical radiation. Depending on the size of haemoglobin-containing structures, the characteristic frequencies of OA signals can vary quite significantly, ranging from hundreds of kilohertz to hundreds of megahertz. Meanwhile, the bandwidth of the receiving frequency band of standard piezoelectric sensors, as a rule, does not exceed the centre frequency value. It is possible to expand the receiving band of ultrasonic detectors to the required 0.1 kHz – 100 MHz values by using nonresonant piezomaterials based on polyvinidylene fluoride (PVDF). Two ultra-wideband detectors based on PVDF piezofilms of different thicknesses (9 μm and 25 μm) with different amplitude-frequency characteristics are experimentally compared. Comparative OA imaging of a tissue-like phantom demonstrates that the low-frequency sensor (film thickness l = 25 μm) has a greater depth of field, while the high-frequency sensor (l = 9 μm) has a better sensitivity in the range of 40 – 100 MHz. Using OA imaging of an experimental tumour in vivo, it is shown that a sensor with l = 25 μm is better suited for examining normal tissue containing relatively large blood vessels, while a sensor with l = 9 μm is better suited for studying tumour tissue containing a large number of multidirectional blood vessels of minimal size comparable to the maximum spatial resolution of the OA system.

A Dual-Band Orthogonally Polarized Contour Beam Transmitarray Design

A dual-band (12.5/14.25 GHz) orthogonally polarized contour beam transmitarray has been designed to accomplish the contour beam pattern for a European coverage region in both transmit and receive frequency bands. A quad-layer transmitarray unit cell configuration is optimized theoretically for an efficient dual-band operation. An orthogonally polarized 3-dipole unit cell with 360° phase range is used to control transmission phases at both frequencies independently. A modified intersection approach with a fast Fourier transform algorithm is used to optimize the aperture phase distribution of transmitarray at each frequency independently. An antenna prototype has been fabricated and tested. The measured contour beam patterns are in good agreement with the calculated patterns in both frequency bands. The measured minimum gains in the required coverage region are 25 and 25.3 dBi at 12.5 and 14.25 GHz, respectively.

Акустооптические модуляторы с расширенной частотной полосой для волоконно-оптических линий

A modulator-frequency shifter with single-mode optical fibers for a radiation wavelength of 1064 nm has been developed and manufactured. The light beam was focused in the center of the sound column. Modulator switching time ≃ 18 ns. Operating mode: pulse, continuous. Total optical loss at center frequency: -3.2 dB. An expression for the frequency band of reception of the modulator is obtained. The estimates are in good agreement with the experimental data ≃ 40 MHz. It is shown that the use of a scheme with a focused beam makes it possible to implement a modulator with a minimum switching time ≃ (2-3) ns and a receiving frequency band ≃ (200-300) MHz.

Third-order passive intermodulation distortion cancellation using a cubic Volterra filter for wireless relay systems

Passive intermodulation distortion (PIMD) is a phenomenon in which two or more transmission signal frequencies interfere with each other due to non-linearity in passive elements of a wireless communication system and undesired signals are generated. Such intermodulation distortion increases the noise level in the receive frequency band of the wireless communication system, thereby degrading the performance of the receiver. In this paper, a PIMD mitigation scheme based on a modified cubic Volterra filter is proposed to reduce a passive intermodulation distortion level to enhance the uplink signal receive performance. The performance of the proposed approach is evaluated by applying it to the data sampled at a repeater for the long term evolution (LTE) system. The proposed approach demonstrates a notable reduction of PIMD in the receive band. The conventional least mean square (LMS) approach is considered in this study for the purpose of comparison.

Research of Antenna for Microwave Energy Transmission System for IOT

This paper is oriented to the specific networking applications of wireless energy transmission system. No need to accredit 2.45/5.8GHz microwave as energy carrier by using the system, and the array antenna transmitting microwave energy, both improve the emission efficiency of the energy, and the energy to the transmission. Through improved microstrip-fed slot design of receiving antenna of microstrip branch and groove, it does not only solve the receiving frequency band narrow problem, but also improve the 2.45 GHz and 5.8 GHz two frequency microwave energy receiving efficiency of the microstrip fed slot antenna. Experiment and simulation results show that the wireless energy transmission system energy projection direction is strong, and the transmit and receive efficiency is high, taking into account the energy transfer and communication. The results of this study will be of great significance to the practical application and industrialization of the Internet of things technology.

High-Performance Electrically Thin Dual-Band Polarizing Reflective Surface for Broadband Satellite Applications

This paper describes an anisotropic impedance surface that provides dual-band linear-to-circular polarization conversion in reflection with the peculiar property that a same linear polarization is converted into a given circular polarization handedness over the first frequency band and into the orthogonal one over the second frequency band. This property is of interest for multiple beam satellite communication systems, as the transmit and receive signals are commonly operating in orthogonal polarizations. This paper demonstrates that a simple, electrically thin polarizer design can provide high-performance conversion over the extended frequency bands used for broadband satellite applications. Some insight on the operation of the proposed polarizer is provided, supported by equivalent circuit models and analytical formulas, and compared with full-wave simulation results. The proposed design achieves an axial ratio better than 0.2 dB in simulation at normal incidence. A further iteration of the design and breadboard, taking into account measurement and practical implementation errors, provides an axial ratio better than 0.5 dB in measurement over the full transmit and receive frequency bands allocated to broadband satellite applications within the K/Ka bands.

Design and Optimization of a Single-Layer Planar Transmit-Receive Contoured Beam Reflectarray With Enhanced Performance

This paper presents the design and optimization of a 1.2-meters single-layer planar contoured beam reflectarray in Ku-band. The reflectarray is optimized to fulfill the requirements of a Direct Broadcast Satellite mission, which covers a South American coverage in both transmit and receive frequency bands for dual linear polarization. The reflectarray is designed using a direct optimization approach where all the array elements are optimized simultaneously, thus resulting in a design with enhanced performance compared to designs obtained using a phase-only optimization approach. The reflectarray fulfills all the coverage requirements in both transmit and receive frequency bands and the performance is validated by means of full-wave Method of Moments simulations.

MEASUREMENT OF RADIATED COMPUTER RGB SIGNALS

The present study was conducted to evaluate the information leakage of the display image that can be reconstructed using the electromagnetic interference emitted from a computer. A reconstructed image was generated from the information signal that correlated with the switching of the RGB signals of the computer display. Based on this observation, a measurement method and system for the information signal was developed by displaying an image with vertical stripes. To check the validity of this measurement method and system, test measurements were carried out. The test result revealed that the information signal can be detected in the electromagnetic interference. In addition, the information signal was found to be contained in high volume between 300 and 600 MHz, depending on the receiving frequency band.

舶用レーダーの受信可能周波数範囲の測定例(日本航海学会第28回講演会)

Marine Radar can receive frequencies for instance Radar Beacon and others than its own. Providing the frequency signal to the operating Radar and with the Electronic Tuner of the Radar Reflex Klystron Oscillator (2A25) was able to result the receiving frequency band of 51Mc.