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We demonstrate a simple method to generate a high speed pulse train from a relatively low speed pulse source by spatial spectral filtering using a pulse shaper. For spectral filtering, we build a simple line-by-line pulse shaper with 5 GHz resolution at 1.55 µm, where we use a grating, collimating lens, and intensity mask. By applying a 10 GHz mode-locked spectral comb to the shaper, we generate relatively...
The application of intrinsically nonlinear class-D power amplifiers can be significantly broadened to amplify a wider class of time-varying envelope signals provided a suitable pulse train is synthesized for amplification. Radio-Frequency Pulse-Width Modulation (RFPWM) is one method of encoding the source signal into a binary level pulse train. The performance of class-D power amplifiers with RFPWM...
Output multiplexer (OMUX) is a key building block of a communication satellite payload system. One of the important concerns in an OMUX design is spurious free in the whole working bandwidth to ensure no interference to the high power signal integrity. Although some spurious resonances caused by the fundamental mode can be predicted at circuit level simulation, many hidden spurious resonances caused...
We report on the use of a knife blade as a scanning probe for scattering-type scanning near-field microscopy at millimeter wavelengths. Since the knife blade probe is a wider version of the metal tip antenna (whisker antenna) widely used in the terahertz and infrared regions, an improvement in signal intensity, and hence in the image contrast was expected. A scanning method and an image reconstruction...
A power-scalable, efficient and very wideband GaN class-E high-power amplifier is described. The large bandwidth performance is achieved by employing the so-called “class-E with parallel-circuit” loading conditions using a very compact all-lumped element implementation. The fundamental loading is realized by the magnetizing inductance of a novel bondwire-based transformer connected directly at the...
We proposed a grounded-stub coupling technique to enhance operating band of a planar monopole antenna. An effectiveness of the proposal is verified with a prototype design of a compact size printed monopole that has been fabricated and measured to demonstrate a broadband behavior of the antenna in a frequency band that ranges from 2.3GHz to 6.5GHz. A return loss characteristic of the prototype antenna...
A simple and fast coupling matrix synthesis technique to directly synthesize generalized bandpass filters of arbitrary bandwidth is briefly discussed in this paper. Unlike those well-known coupling matrix synthesis techniques for generalized Chebyshev filtering function that are only accurate for narrowband filters, the technique is this paper can be used to synthesize filters of arbitrary bandwidth...
S-matrix reconstruction transforms are based on two stages of matrix transformation to remove the mismatch-induced errors. Over the years, these transforms are widely used in measurements of multiport devices using two-port vector network analyzer, especially for noncoaxial applications because high-quality matched loads are hardly accessible. In this paper, analytical error analysis of the S-matrix...
The objective of this paper is to investigate a methodology, which can extract approximate results for the free space radiation pattern from non-anechoic measurements. Using an impulse response both in the time and angular domains of the non-anechoic measurement environment, the free space pattern of the device under test is estimated. Simulated data has been used to illustrate the applicability of...
A new three-dimensional holographic microwave imaging technique is proposed to reconstruct targets in the near-field range. It is based on the Fourier analysis of the wideband transmission and reflection signals recorded by two antennas scanning together along two rectangular parallel apertures on both sides of the inspected region. The complex scattering parameters of the two antennas are collected...
A wireless sensor node based on a chipless RFID tag with integrated sensor element is presented. The chipless tag is multiresonator-based and encodes data as spectral signature. The sensor element is attached to a dedicated resonator of the chipless tag. Two types of sensor elements are used - resistive and capacitive. The resistive sensor output changes the Q factor of the spiral resonator effectively...
A novel design and related research of two-dimensional monopulse radar system with instantaneous polarization measurement capability is introduced. The radar system is designed to obtain and make effective use of the complete polarization scattering matrix (PSM) of radar targets. Polarization diversity technique is absorbed in both transmitting and receiving (T/R) paths. Orthogonal signals are used...
A time-domain beam propagation based on finite element method has been proposed for analyzing anisotropic photonic crystal waveguide structures. The proposed method is useful for simulation of optical wave propagation in 2-D optical waveguides, especially photonic crystals with defects. The numerical examples have been carried out. In addition, a design of coupling-type polarization splitter has been...
This paper proposes that terahertz waves may be generated from higher frequency sources by exploiting the difference-frequency nonlinear effect in ferroelectric crystals. The nonlinear response of ferroelectric crystals together with the fact that they are resonant in the terahertz region is the main reason for proposing their use.
This paper presents a dual-band circularly polarized slotted monopole antenna. This antenna is fed by a 50 O microstrip line. The measured results demonstrate that the slotted monopole antenna has a return loss < 10dB, an axial ratio (AR) < 3dB, and 6 % circular polarization bandwidth with respect to the center frequency at 2.4 GHz, and 1.7 % circular polarization bandwidth with respect...
This paper proposes a novel methodology to automate the design process of patch antennas using Improved Sequential Quadratic Programming (ISQP). Patch antennas are widely used in the automotive domain and are a key enabler of car-to-car and car-to-infrastructure communication. Although simulation tools have been improved in term of accuracy, a manual design process still takes a lot of time as well...
An advanced concept for the visual observation of microwave signal propagations is proposed and demonstrated experimentally, where features of Fourier components included in a radio frequency (RF) wave packet are emphasized. The concept is based on the ultra-parallel measurement scheme in the space domain: the live electrooptic imaging technique. Theoretical explanation of the concept is given first...
A compact 80-GHz band (81–86 GHz) 90° coupler using capacitively center-loaded microstrip transmission lines is proposed. The coupler is implemented in a 0.15 µm GaAs pHEMT technology and has longitudinal and transverse arms of the same characteristic impedances of 50-Ω to reduce the effect of manufacturing tolerance and to facilitate the layout. The experimental results demonstrated a phase difference...
Image formation with high dynamic range is a crucial requirement of next-generation radio telescopes such as the Square Kilometer Array (SKA). Effects that may limit dynamic range include time variations of antenna beams against the celestial sphere during multiple measurements that decrease the effects of thermal noise and increase spatial resolution. Such beam variations must be small or known and...
A compact directional coupler with tunable coupling ratio is proposed. It essentially consists of a pair of 180-degree long transmission-lines and two varactors, which are used for tuning of the coupling ratio in real-time. The particular coupler considered in this work makes use of the broadside coupling configuration to achieve size miniaturization and is, theoretically, capable of having any levels...
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