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

Elements of Microwave Integrated Circuits. Planar Transmission Lines-- Methods of Analysis. Analysis of Striplines and Stripline-Like Transmission Lines. Analysis of Coupled Striplines and Stripline-Like Transmission Lines. Design Data on Single Strip Conductor Stripline-Like Transmission Lines--Characteristic Impedance and Effective Dielectric Constant. Design Data on Edge-Coupled Stripline-Like Transmission Lines--Characteristic Impedances and Effective Dielectric Constants. Design Data on Broadside-Coupled Stripline-Like Transmission Lines--Characteristic Impedances and Effective Dielectric Constants. Design Data on Broadside-Edge Coupled Stripline-Like Transmission Lines and Some Special Structures. Hybrid-Mode Analysis and Dispersion Data on Stripline-Like Transmission Lines. Discontinuities in Stripline-Like Structures. Losses in Stripline-Like Transmission Lines. Circuit Design and Applications. References. Index.

Stripline-Like Transmission Lines for Microwave Integrated Circuits

In this letter, a high-gain, aperture-efficient cavity resonator antenna using metamaterial superstrate is reported. Highly reflective compact metamaterial surface resonating at 10.15 GHz with measured 3-dB bandwidth stopband characteristic of 4.10 GHz from 8.1 to 12.2 GHz is proposed. Material property of the metasurface is studied by using the free-space technique. Next, the metasurface is used as a superstrate to a patch antenna operating at 10.09 GHz, forming Fabry-Perot cavity. Gain enhancement of 11.85 dB in H-plane and 12.5 dB in E-plane with improved cross-polarization level and front-to-back ratio is observed. The prototype cavity antenna shows calculated gain of 16.35 dB achieving 92.42% of maximum gain due to effective aperture area in H-plane.

High-Gain and High-Aperture-Efficiency Cavity Resonator Antenna Using Metamaterial Superstrate

This letter presents a highly isolated compact four-element planar ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna array configuration. The main advantages of the proposed array configuration are that it requires no isolation/decoupling circuit and the configuration is easily extendable to larger size array. The array consists of novel miniaturized slotted annular ring monopole antenna and each element in the array is placed orthogonal to its adjacent elements. The fabricated structure provides good impedance bandwidth matching and high isolation between elements over the range from 3 to 15 GHz. The absence of decoupling circuit results in overall compact size of the proposed design. The prototypes are fabricated and tested. The simulated and measured results are in good agreement. Moreover, the envelope correlation coefficient and channel capacity loss of the array are calculated, which shows good MIMO performance. The proposed monopole antenna structure supports multielement UWB MIMO antenna array design with easy extension of elements and without any decoupling circuit. An example of eight-element array is also investigated.

Easily Extendable Compact Planar UWB MIMO Antenna Array

In this letter, frequency selective surface (FSS) properties of a uniplanar electromagnetic band-gap (EBG) unit cell are studied. The unit cell consists of meander-line inductor and interdigital capacitors on one side of a substrate. Simulation results indicate that the unit cell exhibits passband characteristics centered at 10.04 GHz. FSS property of the structure is verified by measurement using X-band waveguides. The measured results show passband characteristics at 9.45 GHz. A 13 × 13 array of these unit cells (FSS screen) is used as a superstrate at a distance ≈ 0.5λ
 0
 over a patch antenna operating at 10.8 GHz, offset from center frequency of the FSS passband. Directivity improvement of 6.95 dB is observed along 0° in the measurements of patch antenna with FSS superstrate as compared to the patch antenna without superstrate.

FSS Properties of a Uniplanar EBG and Its Application in Directivity Enhancement of a Microstrip Antenna

This paper presents a unified analytical approach to solve a class of shielded strip and shielded microstrip-like transmission lines with multilayer dielectrics under TEM-wave approximation. The analysis makes use of the variational technique in the space domain combined with the "transverse transmission line" method. Expressions are derived for the capacitance of a single line, coupled two-line and coupled four-line structures. The same formulas can be used for a class of such structures by the substitution of a single parameter, namely, the admittance at the charge plane, which can be obtained using the standard transmission line formulas. Numerical results of two special structures, namely, the broadside-coupled suspended microstrip lines, and broadside-coupled inverted microstrip lines, using two suspended, dielectric substrates are included. The technique presented is the simplest compared to any other analytical procedures reported in the literature.

Shiban K. Koul

Papers

Stripline-Like Transmission Lines for Microwave Integrated Circuits

High-Gain and High-Aperture-Efficiency Cavity Resonator Antenna Using Metamaterial Superstrate

Easily Extendable Compact Planar UWB MIMO Antenna Array

FSS Properties of a Uniplanar EBG and Its Application in Directivity Enhancement of a Microstrip Antenna

Unified Approach to Solve a Class of Strip and Microstrip-Like Transmission Lines