This paper reports the development of very compact broad-band baluns using Lange couplers. Theoretical simulations indicate that less than 0.07 dB and 0.45 degrees for the amplitude and phase balances, respectively, can be achieved over the 25-50 GHz bandwidth. Measured amplitude and phase balances of less than 0.3 dB and 2.5 degrees, respectively, from 1 to 2.2 GHz were also obtained. Compared to other reported baluns, they are more compact, simpler, easier to design, and fabricated on only one side of the substrate and, thus, are attractive for microwave and millimeter-wave hybrid and monolithic integrated circuits (MIC's and MMIC's).
This paper discusses the RF interferometry at millimeter-wave frequencies for sensing applications and reports the
development of a millimeter-wave interferometric sensor operating around 35 GHz. The sensor is completely realized
using microwave integrated circuits (MICs) and microwave monolithic integrated circuits (MMICs). It has been used for
various sensing including displacement and velocity measurement. The sensor achieves a resolution and maximum error
of only 10 μm and 27 μm, respectively, for displacement sensing and can measure velocity as low as 27.7 mm/s with a
resolution about 2.7mm/s. Quick response and accurate sensing, as demonstrated by the developed millimeter-wave
interferometric sensor, make the millimeter-wave interferometry attractive for sensing of various civil and mechanical
structures.
We report a millimeter-wave stepped-frequency radar operating from 29.72 to 37.7 GHz for sensing applications. The
radar is implemented using coherent super-heterodyne scheme and completely realized using microwave and millimeterwave
integrated circuits. The developed radar has been demonstrated for different sensing applications with high accuracy and resolution. It can be used for various sensing applications including pavement and bridge assessment, liquid-level measurement, detection and location of buried mines and unexploded ordnance (UXO), detection of intrusion to structures including important civil facilities, detection of slow moving objects, surveillance and monitoring of hidden activities and objects.
We present an impulse ultra-wideband (UWB) sensor and demonstrate its sensing capability through various tests. The
sensor, consisting of transmitter, receiver and antennas integrated together in a single package, is capable of transmitting
impulse signals varying from 450 to 1170 ps and detecting signals up to 5.5 GHz. It has a range resolution of about 1 inch. The system can vary the transmitting pulse duration, thus effectively simulating multiple UWB systems working together consecutively.
Controlled-source electromagnetic (CSEM) spatial profiles and 2-D conductivity maps were obtained on the Brazos Valley, TX floodplain to study the fractal statistics of geological signals and effects of man-made conductive targets using Geonics EM34, EM31 and EM63. Using target-free areas, a consistent power-law power spectrum (|A(k)| ~ k ^-β) for the profiles was found with β values typical of fractional Brownian motion (fBm). This means that the spatial variation of conductivity does not correspond to Gaussian statistics, where there are spatial correlations at different scales. The presence of targets tends to flatten the power-law power spectrum (PS) at small wavenumbers. Detection and localization of targets can be achieved using short-time Fourier transform (STFT). The presence of targets is enhanced because the signal energy is spread to higher wavenumbers (small scale numbers) in the positions occupied by the targets. In the case of poor spatial sampling or small amount of data, the information available from the power spectrum is not enough to separate spatial correlations from target signatures. Advantages are gained by using the spatial correlations of the fBm in order to reject the background response, and to enhance the signals from highly conductive targets. This approach was tested for the EM31 using a pre-processing step that combines apparent conductivity readings from two perpendicular transmitter-receiver orientations at each station. The response obtained using time-domain CSEM is influence to a lesser degree by geological noise and the target response can be processed to recover target features. The homotopy method is proposed to solve the inverse problem using a set of possible target models and a dynamic library of responses used to optimize the starting model.
Dynamic characteristic impedances of the broadside-coupled coplanar waveguide (CPW) are calculated using the spectral-domain approach. It is found that variation of the mode characteristics impedances can be substantial over the dominant-mode frequency range, indicating the need for dynamic characteristic impedances for accurate designs of broadside- coupled CPW circuits at high frequencies.
This paper reports the development of an ultra-wide slotline antenna. The antenna is fed using a broad-band coplanar waveguide-to-slotline transition. A return loss of better than 10 dB over a very wide bandwidth of 0.5 to 6 GHz has been measured. Typical measured gain is 8 dBi at 5 GHz. As the antenna can easily be scaled for operations at millimeter and submillimeter wavelengths, its achieved extremely wide bandwidth demonstrates the potential for ultra-wide- band applications in these regimes.
New planar transmission lines employing multilayer structures are examined for possible applications in microwave and millimeter-wave integrated circuits. Detailed investigations are presented through numerical results calculated using the spectral domain technique. The newly proposed transmission lines have many attractive features such as large impedance ranges, flexibility and the ability to realize complicated, densely packed integrated circuits, as well as miniaturization through the use of thin dielectric layers.
A frequency dependent analysis of suspended stripline step discontinuities using the mode matching technique is presented. Numerical results of scattering parameters are presented in microwave as well as in millimeter-wave frequencies.
This paper presents recent work on coplanar waveguide (CPW) step discontinuities and broadside-coupled CPW for microwave and millimeter-wave integrated circuits (MIC's and MMIC's) using the full-wave mode-matching and spectral- domain methods. Various numerical results are presented and discussed. It has been found that the broadside-coupled CPW has a very weak dispersion, a desirable feature for wide-band microwave and millimeter-wave integrated circuits (MIC's and MMIC's) and high-speed digital integrated circuits.
The results of design and study of diminutive surface wave magnetrons (SWMs) of mm radio wave range with
thermocathode and super diminutive SWMs with heatless cathode are presented.
Modal analysis of microstrip and flnline stepjunctions, commonly seen in microwave and millimeter-waveintegrated circuits, are derived. Numerical results ofscattering parameters are presented in W-band (75 - 110 GHz).There is a good agrrement between our calculated results andpublished data.
This paper reports the development of a new class of end- coupled band-pass filters using broadside-coupled coplanar waveguides (CPWs) suitable for microwave and millimeter- wave integrated circuits. The filters consist of a sequence of CPW broadside-coupled sections periodically located along CPW. Several three-resonator band-pass filters have been developed at X-band (8-12 GHz) and Ka-band (26.5-40 GHz). Good agreement between the theoretical and ex- perimental results has been found.
An efficient implementation of the harmonic balance method, using novel numerical algorithms, that are both robust and efficient, coupled with analytical expressions developed for the elements of the Jacobian matrix, is presented. The approach possesses excellent convergence property and speed. Simulated performances using the developed approach for a 10-GHz GaAs MESFET amplifier are found in good agreement with the measured results. Developed techniques should be very useful for analyzing nonlinear microwave as well as optical components.
A new and efficient analysis approach for the microwave and millimeter-wave MESFET mixers is developed. The approach incorporates the harmonic balance large signal analysis, implemented using novel, robust and fast numerical algorithms, into an extended small signal analysis originally developed for diode mixers. Simulated performances of a GaAs MESFET mixer circuit using the developed analysis and the commerically available software LIBRA agree very well.
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