A Negative Group Delay (NGD) filter prototype design based on cascaded identical 2nd-order baseband stages is presented. The prototype design achieves an NGD-bandwidth product that in the upper asymptotic limit for a distributed design is a function of out-of-band gain in decibels raised to the power 3/4. This is an improvement of previous cascaded first-order designs that have an NGD-bandwidth functional dependency of out-of-band gain in decibels to the power of 1/2. The bandwidth is taken as the 3 dB amplitude response bandwidth. The corresponding NGD design upshifted to a non-zero center frequency, i.e. a Band-Stop Filter (BSF) design, is shown to be possible to implement with Sallen-Key topology, and an example is presented for a 500 MHz center frequency and a 100 MHz (20%) 3 dB bandwidth. The filter shows a 4.05 ns negative group delay with a 1.28 ns in-band variation and a 3-dB amplitude response over the bandwidth of 100 MHz, achieving an NGD-bandwidth product of 0.405. An in-band distortion metric is presented, which can be evaluated for any specified time-domain input waveform. It is shown that the bandwidth, order of filter and desired distortion for a particular input waveform are interrelated. Therefore, the proposed in-band distortion metric constitutes another trade-off quantity to be checked for any type of NGD design.....

A co-planar waveguide-fed symmetrical staircase-shaped ultra-wideband antenna is proposed in this work. This antenna consists of three pairs of rectangular notches, two symmetrical C-shaped slots and two pairs of quarter-circular-ring-slits which are etched on the rectangular radiator and ground plane, respectively. By sequentially inserting three pairs of rectangular notches with proper positions, an excellent impedance bandwidth of 1.55-16.95 GHz (166.51%), i.e., a 10.94:1 ratio bandwidth is obtained. The total volume of the prototype is merely 0.239×0.224×0.004λ_l³, λ_l wavelength of the free space at the lowest operating frequency (i.e., 1.55 GHz). As a result, wider impedance bandwidth, fair gain and better impedance matching of the proposed antenna are obtained. It is observed that the simulation results are in good agreement with the measurement results. The transmission line model (TLM) of the proposed antenna is presented, and it shows the antenna behavior based on the effect of each element. It is observed that the characteristics of the TLM model are close to the simulation result using the CST simulator. The prototype is successfully implemented, fabricated, and compared with the experimental results.....

This paper proposes an absorption-transmission-absorption (A-T-A) type frequency-selective rasorber (FSR) with high selectivity that is loaded above a polarization conversion structure (PCS) and applied to a circular polarization (CP) slot antenna array for ultra-wideband radar cross section (RCS) reduction. Outside the operational frequency band (out-of-band) of the antenna, the energy of the incident electromagnetic (EM) wave is directly absorbed by the FSR, whereas from within the operational frequency band (in-band) of the antenna, the incident EM wave penetrates the FSR and irradiates it on the PCS placed on the lower layer of the FSR structure, which meets the phase cancellation condition and is diffused at the same time, thereby realizing the in-band RCS reduction. Due to the lower insertion loss in the passband, higher quality factor (Q value) in the transmission band, and wider absorption band, the proposed FSR can minimize the gain loss (only 0.2 dB) of the CP slot antenna array and widen the RCS reduction bandwidth to 135.5% (5-26 GHz). In addition, due to the central symmetry of the FSR and PCS structures, the CP slot antenna array has monostatic RCS reduction performance for both horizontally polarized (HP) and vertically polarized (VP) incoming waves.....

Shale oil and gas are unconventional oil and gas resources that can be used as alternative energy sources in the future. Shale reservoirs are the new growth point for the exploitation of oil and gas and development of China's oil and gas industry. The heterogeneity of the shale stratum determines the complexity of its mining. Accurate identification and detection of its oil-bearing characteristics are principal tasks in the oil shale deposit evaluation and economically exploitable interval division. Dielectric logging cannot rely on traditional resistivity logging curves, and it is not affected by the formation water salinity, which can provide the formation water porosity. Combined with other types of logging, it can effectively evaluate the formation oil saturation. In this study, we applied a new type of high-frequency dielectric logging tool in the production of shale oil, developed by the 22nd Institute of China Electronics Technology Group Corporation, based on different dielectric constants of oil, rock matrix, and water. We first introduced the principle of dielectric logging and the major advantages of the dielectric logging tool, and further proposed a new complex refractive index model with clay correction and explained the processing methods, which improved the accuracy of calculating the formation water saturation. Furthermore, the developed technology was applied and evaluated in the Songliao Basin.....