Volume 73, Issue 1-2 -

High- Q substrate integrated waveguide (SIW) resonator and its application to low phase noise oscillators are focused in this paper. By drilling air holes in the substrate, SIW bandpass filters (BPFs) with high Q factor could be achieved. This SIW filter is embedded into the feedback loop to be treated as a frequency stabilization element in designing the oscillator. The complex quality factor ( Q sc )-peak frequency of the filter is chosen as the final oscillation frequency to obtain low phase noise performance. Moreover, air boxes are utilized instead of the air holes in the substrate to design another oscillator with lower phase noise performance and good harmonic suppression. Two low phase noise oscillators based on fourth-order SIW BPFs with dielectric loading have been studied, demonstrated and fabricated to verify the design concept.

A simple and successful design for a microstrip stepped-impedance resonator (SIR) bandpass filter (BPF) based on inductive coupling is presented. It is well known that SIRs are used to shift or suppress the higher order frequencies. In order to achieve compact circuit size, a perceptual stepped-impedance resonator is utilized. Based on theoretical analysis, this resonator can shift the spurious frequency to 3.8 f 0 . The experimental results show good agreement with theory and simulations.

In this paper, two compact balanced bandpass filters (BPFs) using half-wavelength folded S-shaped slotline resonators (FSSRs) are designed. The proposed FSSR is realized by extending and folding a traditional S-shaped slotline resonator, which can affect the internal coupling of resonator and reduce the size of the resonator. The balanced stepped-impedance microstrip-slotline transition structures are employed to generate a wideband common-mode (CM) suppression. The proposed filters can realize a single-band differential-mode (DM) bandpass response or a dual-band one by employing one or three FSSRs, respectively. Moreover, the center frequencies of the DM passbands are independent from the CM responses, which can simplify the designs procedure significantly. In order to validate their practicability, a compact balanced dual-band BPF with controllable center frequencies and bandwidths is fabricated and good agreement between the simulated and measured results is observed.

In this paper, a new compact, vialess and vertical microstrip-to-microstrip differential transition is presented based on half-wavelength slotline structure. The equivalent-circuit model is constructed, and theoretical analyses based on equivalent circuit model reveal that good differential mode (DM) signal transmission between the top- and bottom-layer differential microstrip lines can be achieved over a wide frequency range determined while the common mode (CM) signal is rejected. Moreover, the systematic design method is presented to extract the values of electrical parameters from prescribed performance in terms of its operating bandwidth and ripple levels. In addition, owing to the employment of half-wavelength slot, the proposed differential transition has a compact size. Finally, the proposed differential transition and design theories are well vindicated by an exemplary circuit centered at 2.45 GHz with the measured relative frequency bandwidth (FBW) of 114 %.

This paper presents a novel design approach of a compact dual-band monopole antenna with an overall size of 18.9x13x1.6mm 3 . The proposed antenna is composed of a fractal ring shaped patch fed by a Y-shaped transmission line on the top side of the substrate and a second fractal ring along with a U-shaped ground plane on the bottom side. The second fractal ring, identical to the radiating ring, is loaded and a rectangular slot is etched at the top side of the ground plane respectively, to achieve dual-band characteristic and improve the impedance matching. The effect of standard ground-plane (SGP) of a laptop computer is incorporated in the design; the antenna is mounted on a SGP in order to investigate its performance. The antenna covers widely the frequency bands of the WLAN 2.4 GHz (2.2–2.52 GHz) and WiMAX 3.5 GHz (3.32–4.35 GHz), and exhibits an omnidirectional radiation pattern in the H-plane and a monopole like radiation pattern in the E-plane. A good agreement between the simulated and measured results indicates that the proposed dual-band antenna design is suitable for WLAN/WiMAX applications.

A triple band-notched ultra-wideband (UWB) monopole antenna etching novel folded resonator on the radiating patch, ground and between the feeding-line, is presented in this paper. The tri-rejection bands are 5.1–6.1 GHz, 7.6–8.8 GHz and 10.1–10.8 GHz which have covered bands of WLAN and ITU 8 GHz. To analyze the principle of proposed antenna, the simulation of parametric study and distribution of surface current are carried out. The size of antenna is 32 mm×19 mm×1 mm. And the test results are in good agreement with the simulation, which indicate that the antenna is promising for UWB system.

In this paper, a Tri-band microstrip-line-fed low profile microstrip patch antenna is proposed for future multi-band 5 G wireless communication applications. The proposed antenna is printed on a compact Rogers RT5880 substrate of dimensions 20×16.5×0.508 mm 3 with relative permittivity, ε r of 2.2 and loss tangent, tan δ of 0.0009. To improve return loss and bandwidth of the proposed antenna, a partial ground plane technique is employed. The proposed antenna operates at 10, 28, and 38 GHz, three of the selected frequencies which are allocated by the International Telecommunication Union (ITU) for 5 G mobile communications. To reduce interference between the 5 G system and other systems in the band, a pair of T-shaped slots is etched in the radiating patch to reject unwanted frequency bands. The proposed design provides a gain of 5.67 dB at 10 GHz, 9.33 dB at 28 GHz and 9.57 dB at 38 GHz; the radiation pattern is mostly directional. The proposed antenna is designed and optimized using two commercial 3D full-wave software, viz. CST microwave studio and Ansoft HFSS. A prototype of the designed antenna that was fabricated and showed good agreement between the actual measurements of S11 & VSWR and the simulation results using both software.

A novel pulse encoding strategy for RF switch-mode power amplifier (SMPA) is proposed in this paper to achieve benefits of multi-level delta-sigma modulators (DSM) while alleviating challenges that multi-level DSM brings to SMPA. The pulse encoder consists of a multi-level delta-sigma modulators (DSM) followed by a level transformation module (LTM). Based on the equal-area criterion, LTM directly maps the multi-level DSM pulse train into a binary pulse train which enables a simple system configuration. The feasibility and effectiveness of proposed strategy are verified by numerical simulation and experimental measurement. Results show that, with a similar coding efficiency, the proposed strategy obtains more than 7 dB improvement in average in-band signal to noise ratio (SNR) compared to traditional two-level DSM.

In this work, an efficient non-invasive terahertz pulse technique is proposed and investigated to determine the thickness and refractive index of each layer in an optically thick stratified media. A closed form formulations are derived for simultaneous extraction of the thickness and complex refractive index of each layer with the help of primary reflected signals from the multilayered structure. The proposed technique is numerically tested using a full wave electromagnetic simulator and is experimental verified in the millimeter wave frequency range by utilizing the power peaks corresponding to the primary reflected signals. The numerical and measured results of multilayered samples under test are in good agreement with the reference data. The proposed terahertz pulse technique can be used for non-destructive testing of the multilayered system existing in various industries.

Based on the theory of time reversal technique and through the use of temporal dispersive delay lines, this paper presents a demonstration of temporal cloaked signal transmission at microwave frequencies. When compared with a conventional signal processing system, the related dispersive delay lines are not required to provide linear group delay response. Thus the proposal simplifies the system structure for temporal cloaking, avoids the drawbacks of easy detection, easy decoding and easy analysed brought by linear modulation system, and then strengthen the safety and reliability in signal transmission. Theoretical analysis and experimental results validate the proposed system. The proposed method and achieved results indicate potential application in secure communications and data multiplexing subject to channel bandwidth requirements.