Antenna Theory And Design

In general, Micropower Impulse Radar (MIR) depends on Ultra-Wideband (UWB) transmission systems. UWB technology can supply innovative new systems and products that have an obvious value for radar and communications uses. Important applications include bridge-deck inspection systems, ground penetrating radar, mine detection, and precise distance resolution for such things as liquid level measurement. Most of these UWB inspection and measurement methods have some unique qualities, which need to be pursued. Therefore, in considering changes to Part 15 the FCC needs to take into account the unique features of UWB technology. MIR is applicable to two general types of UWB systems: radar systems and communications systems. Currently LLNL and its licensees are focusing on radar or radar type systems. LLNL is evaluating MIR for specialized communication systems. MIR is a relatively low power technology. Therefore, MIR systems seem to have a low potential for causing harmful interference to other users of the spectrum since the transmitted signal is spread over a wide bandwidth, which results in a relatively low spectral power density.

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Response to FCC 98-208 notice of inquiry in the matter of revision of part 15 of the commission's rules regarding ultra-wideband transmission systems

Ultra Wideband Signals and Systems in Communication Engineering

소형 안테나 ( Small Antennas )

This paper addresses the problem of anisotropy in substrate materials for microwave integrated-circuit applications. It is shown that in modeling the circuit characteristics, a serious error is incurred which becomes larger with increasing frequency when the substrate anisotropy is neglected. Quasi-static, dynamic, and empirical methods employed to obtain the propagation characteristics of microstrip, coplanar waveguides, and slotlines on anisotropic substrates are presented. Numerical solutions such as the method of moments and the transmission-line matrix technique are outlined. The modified Wiener-Hopf, the Fourier series techniques, and the method of lines are also discussed. A critique of the aforementioned methods and suggestions for future research directions are presented. The paper includes new results as well as a review of established methods.

Integrated-Circuit Structures on Anisotropic Substrates

The objective is to design a frequency reconfigurable active antenna which involves the integration of active device such as FET with a passive structure. Here the dual port dual band antenna is independently designed and later connected to one port amplifier using matching network. The passive antenna serves as radiator, frequency selector as well as feedback network for the oscillator. First the two port, dual band antenna is simulated in CST. Then the S parameters of the antenna were substituted in ADS as two port item. Here annular slot antenna with shorted slots was selected as radiator which was designed to resonate at 2.4 GHz and 5.2 GHz respectively. The antenna was connected to the amplifier, the active antenna was then simulated and the simulated results were validated through measurement. When tested the oscillator was found to oscillate at 2.097 and 4.576 respectively.

http://ap-s.ei.tuat.ac.jp/isapx/2014/pdf/WE2E_02.pdf

Frequency reconfigurable active antenna

In this letter, we present an innovative filter configuration employing transversal coupled triple-mode spherical resonators while capable of realizing transmission zeros (TZs). Transversal coupling involves simultaneous source and load-controlled couplings to all the three modes of the spherical resonator. Spherical resonators inherently have very large quality factor (Qu) and exhibit a farther spurious response thus yielding bandpass filters (BPFs) with lower insertion loss and wider spurious-free window. The design methodology for transversal coupling is explained and is employed for designing a third-order bandpass filter with TZs. In addition, a sixth-order bandpass filter using cascaded trisection is also presented. A third-order BPF with symmetric TZs is fabricated for verifying proof of the concept. The filter designed at 6.545 GHz with a bandwidth of 120 MHz has an insertion loss better than 0.1 dB and a spurious-free window better than 1.7 GHz. The proposed filter promises to be useful in aerospace applications that demand high Qu, low volume, and wider spurious-free window.

Transversal Coupled Triple-Mode Spherical Resonator-Based Bandpass Filters

In-vivo and ex-vivo biomedical imaging and spectroscopy using sub-THz/THz radiation have proven highly attractive for many years because of their non-ionizing and non-invasive properties. Skin tissue is an ideal sample to analyze using these radiations because it allows overriding some inherent limitations, such as a small penetration depth. A popular application of THz imaging is the detection of melanoma and nonmelanoma skin cancers. The increasing incidence of skin cancer and the difficulty in assessing the clinical and histological characteristics of pigmented lesions have led to an increased demand for non-invasive techniques. The first part of this chapter covers non-invasive alternatives to biopsy and histopathology, such as electrical impedance spectroscopy (EIS), high-frequency ultrasonography (HFUS), magnetic resonance imaging (MRI), Multispectral imaging, and Optical coherence tomography (OCT) and their benefits and limitations for detecting skin cancers. Next, we will look at the progress made in the sub-THz/THz domain toward this field. For skin cancer detection applications, we will examine the role of dielectric and interaction models applied to the skin in the sub-THz/THz regime to assess the suitability of specific THz-based imaging systems. The following sections describe the modern research results that have been achieved from the application of THz technology to the skin, considering both the application for imaging as well as the treatment. 

Sub-Terahertz and Terahertz Waves for Skin Diagnosis and Therapy

In this paper, low-cost polycarbonate substrate is used for design of antennas operating in the 28 GHz band. First, a corner bent inset fed patch antenna is proposed with a forward gain of 7 dBi and a front to back ratio of more than 18 dB indicating minimal radiation towards the user post-integration with the mobile terminal. In order to cater to the landscape mode: a corner bent tapered slot antenna is also proposed with a gain of 7 dBi An overlapped architecture is investigated to demonstrate orthogonal pattern diversity with an effective radiating volume of 0.12λ 0 3 and a port to port distance of 0.13λ at 28 GHz and mutual coupling of less than 27 dB without deterioration in the pattern integrity of the corresponding modes. A corner bent phased array is also illustrated operating at 28 GHz

Polycarbonate based flexible antennas for mmWave 5G devices

In this paper, a low radar cross section (RCS) dipole antenna is proposed by using an absorptive frequency selective reflection (AFSR) structure as the ground plane. The proposed AFSR consists of a bandstop resonator integrated with a broadband absorber and exhibits a reflection notch within the absorption band. The reflection notch achieved in the AFSR structure coincides with the operating band of the dipole antenna. The performance parameter of the dipole antenna co-designed with the AFSR structure is nearly the same as obtained with a metallic reflector backed dipole. However, a significant out-of-band RCS reduction of more than 20 dB in the two side-bands on both sides of the operating band is achieved for the antenna co-designed with the AFSR structure compared to the antenna backed with metallic reflector. Furthermore, the AFSR backed dipole shows an increase in antenna gain by more than 1 dB compared to the reflector backed dipole.

Shiban K. Koul

Papers

Frequency reconfigurable active antenna

Transversal Coupled Triple-Mode Spherical Resonator-Based Bandpass Filters

Sub-Terahertz and Terahertz Waves for Skin Diagnosis and Therapy

Polycarbonate based flexible antennas for mmWave 5G devices

Low Radar Cross Section Dipole Antenna Integrated with Absorptive Frequency Selective Reflection Structure