Junming Diao

Junming Diao
Mississippi State University | MSU · Bagley College of Engineering

PhD
Fully-funded doctoral positions are available for Spring/Fall 2023

About

24
Publications
2,438
Reads
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168
Citations
Citations since 2017
12 Research Items
144 Citations
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2017201820192020202120222023010203040

Publications

Publications (24)
Article
Streamlines of the Poynting vector field connect antenna figures of merit with the energy flow characteristics near a receiving antenna. Poynting streamlines properties and absorption aperture of antenna under different load conditions have been studied in this work. Based on its Poynting streamline characteristics, the short-circuit dipole can be...
Article
The flow of energy around array antenna in receiving mode can be modeled by generating streamlines of the Poynting vector field. From the streamlines that terminate on the array element loads, a geometrical shape can be assigned to the effective area of the array. These concepts provide an intuitive tool for understanding mutual coupling effects in...
Article
Full-text available
A new 1.4 GHz 19-element, dual-polarization, cryogenic phased array feed (PAF) radio astronomy receiver has been developed for the Robert C. Byrd Green Bank Telescope (GBT) as part of FLAG (Focal L-band Array for the GBT) project. Commissioning observations of calibrator radio sources show that this receiver has the lowest reported beamformed syste...
Article
Full-text available
Fundamental limits on the degree of practical achievable superdirectivity for antennas include narrow bandwidth, large antenna loss and sensitivity to excitation and fabrication errors. Superdirective antennas are commonly considered as transmitters, but thinking of the antenna as a receiver may help to understand and overcome some of these limits...
Article
Full-text available
Array antennas with aperiodic element placement provide a way to mitigate grating lobe level when the array element spacing is larger than one half wavelength. Design techniques for aperiodic arrays include thinning, numerical optimization, and other methods, but even with modern tools, designing electrically large aperiodic arrays remains computat...
Article
Full-text available
For phased arrays used in satellite communications and radio astronomy, high sensitivity is required, and minimizing antenna losses is critical. Losses for single antennas can be minimized by using high conductivity materials. It is less well understood that loss for array antennas is also influenced by mutual coupling between array elements and th...
Article
A receiving antenna alters an incident field in such a way that the field is concentrated at the terminals of the antenna. The Poynting power flux density vector associated with the field carries to the antenna the power dissipated in the antenna structure and the load. Streamlines of the Poynting vector field can be used to understand electromagne...
Article
For reflector antennas with broadband multiple feed systems, under optimal beamforming conditions, the feed operates at low frequencies as a phased array feed (PAF), with multiple elements contributing to a synthesized illumination pattern, whereas at high frequencies, each element forms a single independent beam. There is a frequency range between...
Conference Paper
A receiving antenna can be considered as a electromagnetic energy concentration device that the field around the antenna either terminated by the antenna load or pass by the antenna. In this paper, streamlines of the Poynting density vector are used to understand the field energy flow near the linear antenna, aperture antenna and superdirective ant...
Conference Paper
The Brigham Young University (BYU) Radio Astronomy group, in collaboration with Cornell University, the University of Massachusetts, and the National Radio Astronomy Observatory (NRAO), have developed a phased-array feed receiver with sufficient bandwidth and elements for basic scientific use. This paper summarizes the capabilities of this 20-MHz,...
Conference Paper
Wide-field phased array feeds (PAFs) are part of the next generation of receivers for astronomical observatories. Groups around the world are developing array feeds for medium to large size dish antennas. The Brigham Young University (BYU) radio astronomy group is focusing its efforts on modeling and developing new high performance PAF systems for...
Conference Paper
We discuss the theory and implementation of phased array receivers in the focal plane of a telescope as applied to the mm-wave band. Simulated performance and construction details are given for a 64 element, 70–95 GHz array receiver for use on the Green Bank Telescope (GBT).
Conference Paper
A collaboration has been underway for the last several years to develop an L-band multipixel phased array feed for the Green Bank Telescope. These efforts will culminate in the deployment of a new wide-field observing instrument, Focal L-band Array for the GBT (FLAG).We report on progress on the cryogenic front end receiver system and real-time dig...
Article
Full-text available
We investigate the emission of terahertz (THz) radiation from two kinds of recently reported fractal photoconductive antennas by the method of separating antennas from transmission lines. A model for analyzing the separation design is presented. From the numerical simulations, the radiation power and center frequency of Sierpinski fractal photocond...
Article
Full-text available
The center frequency of terahertz (THz) pulse radiated from photoconductive antenna is located at the low-frequency range of THz band. None of the antenna designs have been done to enhance the center frequency without decreasing antenna's dimension, which would largely decrease the radiation power. We introduce here the idea of separating antennas...
Article
Full-text available
A transient quasi-analytic method is improved to analyze the offset reflector for impulse radiating antenna (IRA) applications. Physical optic (PO) approximation and analytic time transform (ATT) are utilized to investigate the time domain (TD) radiating characteristics of the offset reflector. With the appropriate coordinate transformation, the TD...
Conference Paper
This paper presents a design of wide-band power amplifier for applications of advanced wireless communication system. Diamond buffer and parallel cascode structure are used in this amplifier. In order to further expand the bandwidth, the inductance and capacitance compensation are also adopted. This has been developed and shown its 3dB bandwidth fr...
Article
Full-text available
We study the rectangular tips of the dipole photoconduc-tive antenna, which has been widely used for terahertz radiation and detection, with different blend radii effect on the emission performance of terahertz (THz) radiation. For the amplitude of THz radiation pulse is proportional to the local electric field in the gap, the increased max-imum bi...

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