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The rotational spectrum of the van der Waals complex NH3-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 112-139 GHz. Newly observed and assigned transitions belong to the K = 0-0, K = 1-1, K = 1-0, and K = 2-1 subbands correlating with the rotationless (jk)NH3 = 00 ground state of free ortho-NH3 and the K = 0-1 and K = 2-1 subbands correlating with the (jk)NH3 = 11 ground state of free para-NH3. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. Some of these transitions are continuations to higher J values of transition series observed previously [C. Xia et al., Mol. Phys. 99, 643 (2001)], the other transitions constitute newly detected subbands. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the ortho-NH3-CO and para-NH3-CO complexes. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of NH3-CO has been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations and an augmented correlation-consistent triple zeta basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the N atom closest to the CO subunit and binding energy De = 359.21 cm-1. The bound rovibrational levels of the NH3-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D 0 are 210.43 and 218.66 cm-1 for ortho-NH3-CO and para-NH3-CO, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the broadband permittivity measurements up to 170 GHz of plate samples by using a balanced-type circular-disk resonator (BCDR) excited by a 0.8-mm coaxial line. Because only the TM ${_{0m0}}$ modes are selectively excited in the BCDR and their resonant frequencies largely change by changing the size of the circular disk that constitutes the resonator, the BCDR method provides permittivity measurements at an almost arbitrary frequency across a wideband. We have increased the maximum measurable frequency of the BCDR method to 170 GHz by developing a BCDR excited by a 0.8-mm coaxial line and by improving the analysis method. We demonstrated that highly stable and rather simple permittivity measurements up to 170 GHz can be realized by the BCDR method by confirming that the measured complex permittivities of a low-loss material from 11.3 to 167 GHz at 59 frequency points obtained with five circular disks of different radii are consistent within the uncertainties. [ABSTRACT FROM AUTHOR]

We introduce the design of dihedral reflectors that are used to calibrate an instrumented, dual-linearly polarized, wide-bistatic compact radar range operating at 160 GHz. The polarization scattering matrix of this bistatic calibration object may be tailored to rotate the incident linear polarization state to a slant polarization state in a fashion that is similar to the 90° dihedral that is used for calibrating monostatic polarimeters. The bistatic calibration object that we describe here is capable of introducing this polarization rotation while simultaneously steering the mainlobe of its specular reflection to the receiver. As we demonstrate, this characteristic of the mainlobe-steered dihedral (MSD) object can be achieved over a wide range of bistatic angles. The MSD object possesses a variety of desirable qualities for the calibration of bistatic polarimeters, but they are particularly useful for those systems that do not possess the capability to rotate their feed arrangement (e.g., millimeter-/ submillimeter-wave waveguide-based systems). Through both computational and experimental results, we demonstrate the capability of the MSD object to calibrate and characterize the accuracy (better than 0.5 dB) and polarization purity (~50 dB) of a 160 GHz dual-linearly polarized, bistatic compact radar range at 15°, 45°, and 75° bistatic angles. [ABSTRACT FROM PUBLISHER]

In field measurements at millimeter-wave (mmWave) frequencies, the spatial propagation characteristics are usually obtained by using steerable high-gain horn antennas to compensate the large path loss. However, it is a challenging issue to deembed antenna patterns from the observed channel responses. This paper has two contributions. First, according to the steering-antenna sounding process, a spatial channel response model is designed, where the multipath propagation profile, antenna pattern, and channel response are spatially sampled and combined in a discrete convolutional form. Then, a low-complexity antenna deembedding algorithm, including two steps of deconvolutions, is proposed. Second, a field measurement campaign on the frequency-space mmWave channels in an office is presented to validate the method. The channels were sounded at 72.5 to 73.5 GHz using three horn antennas with different beam widths and gains. The omnidirectional angular channel responses (ACRs) were measured by rotating the receiver antenna. The observed and reconstructed ACRs are consistent, and the estimated antenna-free angular propagation profiles by using different horn antennas are also highly correlated, which validate the proposed antenna deembedding approach. Furthermore, the omnidirectional transfer functions in the mmWave band obtained using different horn antennas are compared, and the channel coherence bandwidth is analyzed based on the autocorrelation of the transfer functions. [ABSTRACT FROM PUBLISHER]

SUMMARY This report is regarding to a new measurement of a millimeter-wave using optical power. A calorie meter conventionally has been used to measure the millimeter-wave power above 100 GHz, which has high temperature dependence, and therefore finds the difficulty of small power measurement. To overcome this difficulty, we propose the new method to estimate millimeter-wave power by measuring optical power of optical 2-tone signals. This proposed method has low temperature dependence due to optical power, and therefore makes the small power of the above millimeter-wave enable. The principle and the estimation methods of this new method, and its experimental methods and results are explained. Noble results show that the difference between estimated and experiment value is maximally 0.99 dB at 110 GHz, the measurement possibility of frequency extending more than 170 GHz is referred to. [ABSTRACT FROM AUTHOR]

In this article, we propose an approach in the spectral domain to treat the interaction of a field with a dichroic surface in two dimensions. For a Gaussian beam illumination of the surface, the reflected and transmitted fields are approximated by one reflected and one transmitted Gaussian beams. Their characteristics are determined by means of a matching in the spectral domain, which requires a second-order approximation of the dichroic surface response when excited by plane waves. This approximation is of the same order as the one used in Gaussian beam shooting algorithm to model curved interfaces associated with lenses, reflector, etc. The method uses general analytical formulations for the GBs that depend either on a paraxial or far-field approximation. Numerical experiments are led to test the efficiency of the method in terms of accuracy and computation time. They include a parametric study and a case for which the illumination is provided by a horn antenna. For the latter, the incident field is firstly expressed as a sum of Gaussian beams by means of Gabor frames. [ABSTRACT FROM AUTHOR]

In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn2+ impurities(∼0.2%) in MgO. [ABSTRACT FROM AUTHOR]

The wide band at extremely high frequencies (EHF) above 30 GHz is applicable for high resolution directive radars, resolving the lack of free frequency bands within the lower part of the electromagnetic spectrum. Utilization of ultra-wideband signals in this EHF band is of interest, since it covers a relatively large spectrum, which is free of users, resulting in better resolution in both the longitudinal and transverse dimensions. Noting that frequencies in the millimeter band are subjected to high atmospheric attenuation and dispersion effects, a study of the degradation in the accuracy and resolution is presented. The fact that solid-state millimeter and sub-millimeter radiation sources are producing low power, the method of continuous-wave wideband frequency modulation becomes the natural technique for remote sensing and detection. Millimeter wave radars are used as complementary sensors for the detection of small radar cross-section objects under bad weather conditions, when small objects cannot be seen by optical cameras and infrared detectors. Theoretical analysis for the propagation of a wide "chirped" Frequency-Modulated Continuous-Wave (FMCW) radar signal in a dielectric medium is presented. It is shown that the frequency-dependent (complex) refractivity of the atmospheric medium causes distortions in the phase of the reflected signal, introducing noticeable errors in the longitudinal distance estimations, and at some frequencies may also degrade the resolution. [ABSTRACT FROM AUTHOR]

This paper presents an on-wafer millimeter-wave circuit’s characterization build on thin ceramic substrate having a high relative permittivity. An RF short circuit, designed with a quarter-wavelength radial stub, is used in load design and launch transition. To improve the design accuracy of electromagnetic (EM) tools, the dielectric constant of the ceramic substrate is extracted using measurements of several pairs of microstrip lines combined with EM simulations. The largest deviation obtained, compared with the mean value over the frequency band, is less than 1%. Thus, a new six-port circuit is designed and characterized using a millimeter-wave probe station. A comparison between the measurement and simulation results, using extracted manufacturer-recommended relative permittivity, is conducted. The six-port qi points’ location is close to the simulated and theoretical ones over the frequency band of interest. As demonstrated in this paper, the substrate permittivity extraction has improved the design accuracy of the millimeter-wave circuits. Excellent performance of this circuit in terms of matching, isolation, and amplitude and phase balance is obtained. [ABSTRACT FROM AUTHOR]

High-gain and beam-scanning antennas are extremely important in the applications of millimeter-wave (MMW) and terahertz (THz) technologies. Dielectric lens is a suitable candidate for this purpose, because it has no metal and quite small feeding loss. In this paper, discrete dielectric lenses are studied in which periodic antireflection (AR) structures are added to reduce impedance mismatch at the air–dielectric interfaces, leading to higher directivity. Meanwhile, a multifrequency phase matching method is proposed to realize a beam-scanning lens in both MMW and THz regions. The design concept of the beam-scanning lens is applicable to other frequency ranges as well, which opens new opportunities for future lens design. Moreover, three-dimensional (3-D) printing technology is employed to simplify the manufacturing process and reduce the cost. Experiments are done in both MMW and THz regions, and the results verify the concept of lens design. The 3-D printed MMW and THz lenses with fixed and scanning beams demonstrated in this work could be an important step toward MMW and THz communications, radar, and imaging systems for practical applications. [ABSTRACT FROM PUBLISHER]

Accurate dielectric properties are of great importance for the design and fabrication of the input and output windows in vacuum electronic devices. A reflection-type hemispherical open resonator (RTHOR) was designed through theoretical analysis and numerical simulation and also was utilized to measure the dielectric properties of the windows material sapphire. Compared with the two ports measurement, a simplified measurement system to obtain the dielectric performance was proposed and the RTHOR with only one coupling aperture was directly connected to a W-band vector network analyzer (VNA). The material properties can be easily calculated through the VNA measured port reflection coefficient (S) resonant curve. Investigation shows that the permittivity and the loss tangent of the measured sapphire, which is used to construct the input and output window, is respectively about 9.40 and 1.80 × 10 at room temperature in W-band, which agree well with the reported results. Measured results also show that the simplified measurement system can provide a high accuracy for the measurement of low-loss dielectric in a relatively convenient way. [ABSTRACT FROM AUTHOR]

This paper presents a millimeter-wave propagation-channel sounder that uses an optical-fiber cable to achieve phase coherence between transmitting and receiving antennas using two modulated light waves in the vicinity of 1550 nm. In the described sounder, the optical-fiber cable approach permits a separation of up to almost 1000 m between the transmitter and receiver because of the low level of attenuation per unit length in a single-mode optical-fiber cable. The measurement system can sweep from 500 MHz below 60.1 GHz (59.6 GHz) to 500 MHz above 60.1 GHz (60.6 GHz) and proceed to 10 001 in-phase and in-quadrature propagation channel measurements in \sim5~sec. Measurements of the frequency response of nonline-of-sight and line-of-sight indoor/outdoor propagation channels over medium (>100~m) and short ranges can be performed for two or more different lateral receiving antenna positions for antenna diversity studies. [ABSTRACT FROM AUTHOR]

In this work the free space optics (FSO) and the millimeter waves (MMW) links are studied for the Uruguayan weather conditions. FSO availability is affected by fog significantly, while MMW availability is mainly affected by rains. Considering visibility and rain intensity data, these availabilities are estimated for the Uruguayan weather conditions. The results are extensible to other areas with similar weather. Finally the use of both links simultaneously, one as a backup of the other, is discussed. [ABSTRACT FROM AUTHOR]

The design and evaluation of an active three dimensional (3D) millimeter wave imaging system for personnel security screening is presented in this work. The system is able to produce a high-resolution 3D reconstruction of the whole human body surface and reveal concealed objects under clothing. Innovative multistatic millimeter wave radar designs and algorithms, which have been previously validated, are combined to significantly improve the previous reconstruction results. In addition, the system makes use of a reduced amount of information, thus simplifying portal design. Representative simulation results showing good performance of the proposed system are provided and supported by sample measurements. [ABSTRACT FROM AUTHOR]

Abstract: Because of the severe vibration during flight process, the elastic deformation caused by the weight of avionic devices which are placed in the head nacelle of the helicopter such as millimeter wave radar cannot be measured through the optical-imaging and accelerometer-induction method. In order to survey this elastic deformation in real-time, this paper proposes the double-IMUs/DPGS tightly-coupled relative attitude measurement system (TRAMS): double IMUs are comprised by the same accuracy grade inertial sensors; one IMU is assembled in the head nacelle, while the other is in the airframe; the double-IMUs tightly-coupled with the DPGS respectively can measure the attitudes (pitch, roll and heading) of the nacelle and helicopter airframe in high accuracy; the relative attitudes between the two single IMU/DPGS TRAMSs reflect the elastic deformation between the nacelle and airframe. The double-IMUs/DPGS TRAMS have been effectively verified through the ground experiment in a vehicle and two flight tests in a military helicopter. The results present satisfactory stability and repeatability. This system can be popularized to other dynamic deformation measurement backgrounds. [Copyright &y& Elsevier]

Detection of ammonia plays a vital role for counter-bioterrorism applications. Using millimeter wave absorption measurements, ammonia dissolved in water solution is analyzed and compared to water-only solution. The inversion of ammonia molecule results in split rotational spectral lines and transitions of these lines can be detected. Two-port measurements were carried out with vector network analyzer and measurements revealed that ammonia presence can be identified, especially between 30--35 GHz. [ABSTRACT FROM AUTHOR]

A combined finite-difference time-domain/matrix-pencil method is presented for the efficient and rigorous calculation of the full-wave modal S-parameters of waveguide components including structures of more general shape or high complexity. The application of the S-parameter definition for unmatched ports requires merely standard Mur's absorbing boundaries for reliable results, and a nonorthogonal or contour path mesh formulation allows the convenient inclusion of curved boundaries. The efficiency of the method is demonstrated for the analysis of waveguide and monolithic microwave/millimeter wave integrated circuit (MMIC) components of practical importance, such as the twisted waveguide, the twisted waveguide bend, the post compensated magic T, the waffle-iron filter, and the MMIC spiral inductor including an air bridge. The method is verified by excellent agreement with measurements, with finite element method (FEM) or moment method results. [ABSTRACT FROM AUTHOR]