In this paper, a low profile Frequency Selective Surface is presented, for obtaining electromagnetic shielding in four distinct frequency regions. The designed structure consists of three rectangular strips Resonators, Jerusalem cross in the top side and diagonal metallic strips on bottom side of the dielectric. The proposed structure provides electromagnetic shielding at 9.9 GHz, 12.3 GHz, 13.5 GHz, and 16.4 GHz frequency regions. Besides these frequency regions, we also obtain five transparent windows suitable for telemetry application. The prototype of the proposed structure is fabricated. It is observed that the measured results are nearly similar to simulated results because of minor fabrication errors. Furthermore the proposed low profile structure can be deployed for applications like radoms, spatial filters, antenna reflectors and RCS reductions.
In this paper, a full-360° reflection-type phase shifter (RTPS) using a trans-directional (TRD) coupler with multi-resonance loads is presented. It features the characteristics of wide bandwidth, small size, and wide phase shifts with a compact structure and inherent DC blocking. Influences of the multi-resonance loads on the phase shifts and insertion losses of the RTPS are analyzed, and design procedures are given for guidance. For validation, a prototype is designed at 2 GHz. The overall size is 0.56λg × 0.17λg. Measured results show a bandwidth of 20% under the criterion of more than 10-dB return loss. Meanwhile, a relative phase variation of 425° with a maximum insertion loss of 3.6 dB is achieved when the varactor capacitance is varied among 0.35 pF~3.2 pF.
A Negative Group delay (NGD) triple passband filter with a lossy Meander Step Impedance Resonator (MSIR) is introduced in this article. The size miniaturization technique by increasing the number of meander turns is presented. In the process of filter design, the calculation of the total inductance value of the meander section is discussed in a simplified way. At the same time, the electrical and physical lengths of each section of meander resonator are calculated. The proposed filter has three passbands at 2.4, 5.0, and 7.4 GHz. The Group Delay (GD) in the three pass bands is -2.5 ns, -2.1 ns, and -2.0 ns, respectively. The more the number of meander turns is, the more the NGD will be. The proposed design is well equipped to be used in feed-forward and feed-back power amplifier applications. The frequency response exhibits satisfactory Return Losses (RLs) of -24, -25, and -22 dB at these three passbands. Four Transmission Zeros are generated at 3.35, 3.98, 6.2, and 8.31 GHz using an absorptive Folded SIR (FSIR) structure which improve the stopband performance. The overall dimension of the filter is (20.7 x 12) mm = (0.16 x 0.09)λg.
A wideband interdigital Metal-insulator-metal (MIM) capacitor is created and built in a two-layer low temperature co-fired ceramic (LTCC) substrate. To reduce the amount of stopbands and eliminate unexpected spurs which restrict the bandwidth, short-interconnection that interconnects the open ends of interval fingers is proposed. The increment of bandwidth and capacitance of the proposed interdigital MIM capacitor is 206% and 25%, respectively. The proposed interdigital capacitor has a wider frequency applicational range and a compact size of only 8.2×6.2 mm. Performance discussion and comparisons are also carried out.
In this paper, a dipole antenna is investigated for 5G New Radio portable devices. This antenna adopts the characteristics of multiple mode resonance. Then, by adjusting the spacing between dipole pairs, the antenna has a good impedance match in a wide frequency band. The -10 dB impedance bandwidth of the antenna is 2.31-5.34 GHz (79.2%). In the operation frequency band, the maximum gain and average gain of the antenna are 8.68 dBi and 4.67 dBi, respectively. It can be used in the 5G Sub-6 GHz NR frequency bands n7/n38/n41/n77/n78/n79 and also compatible with WLAN/WiMAX band.
A four-element multiple-input multiple-output (MIMO) antenna based on a modified Complementary Split Ring Resonator (MCSRR) is presented in this paper for dual-band 5G smartphone applications. An inverted L-shaped radiator is used with MCSRR as an open stub in the ground, where MCSRR is responsible for dual operating bands and enhances the impedance matching. The MCSRR as an open stub in the ground plane creates a notch band that minimizes the interference in 5G wireless communication. The four elements of the antenna are placed in such a way that minimum isolation between antenna elements is obtained, 16.5 dB, without any decoupling, whereas more than 20 dB isolation is achieved by using T-shaped decupling. The antenna achieves dual 10 dB bandwidths from 3.40 GHz to 3.625 GHz and from 3.90 GHz to 4.525 GHz. Envelop correlation coefficient (ECC) is extracted from far-field results to analyse the MIMO antenna performance in practical design consideration.
An infrared (IR) pyroelectric detector for applying to the terahertz (THz) waveband that uses diffraction limited focusing of the THz beam on the sensitive area of the detector is studied. The signal to be detected is coupled to the optical window of the detector through a two-wavelength diameter polytetrafluoroethylene spherical particle-lens based on the terajet effect. We have experimentally demonstrated an enhancement of the IR detector sensitivity by 5.6 dB at 0.2 THz without degradation of the noise equivalent power value. The results show that the proposed method could be applied to increase the sensitivity of various commercial IR sensors in the THz range, requiring no modification of the internal structure and may be applied also to acoustics and plasmonics.
The tapered waveguide as a microwave plasma excitation structure is widely used in the industrial field. However, it needs high input microwave power to ignite and sustain plasma because its electric field is not sufficiently focused in the discharge area. In order to solve this problem, this paper proposes a novel microwave plasma source based on a ridged waveguide. The structure of the proposed microwave plasma source is optimized to focus the electric field in the discharge region by electromagnetic calculations before the plasma excitation. Then, the equivalent circuit model is used to analyze the impedance matching characteristics of the novel device after the plasma excitation. In order to validate this device, a microwave plasma system is built to measure the plasma exciting power and sustaining power in both air and argon at atmospheric pressure. The simulation and experiment are carried out in both tapered waveguide and the proposed device. Simulation results show the electric field of the ridged waveguide is 1.9 times of that of the tapered waveguide when the input power is 1500 W. Moreover, in the experiments, the exciting power and sustaining power of the air and argon plasma in the novel device are lower than those of the tapered waveguide at different gas flow rates.
A compact ultra-wideband Multiple-Input-Multiple Output (MIMO) orthogonal microstrip fed linear tapered slot antenna (LTSA) is planned for frequency notched applications. The projected MIMO antenna comprises of two indistinguishable linear tapered slot antennas excited by two orthogonal microstrip feeds. In this paper, double split-ring resonators (DSRRs) are suggested to develop the isolation between two linear tapered slot antenna elements. A quarter wavelength spur line is entrenched on the feeding part of the micro-strip antenna to attain the notch frequency. The L-shaped spur line adds to the notch frequency at 5.5 GHz targeted to dodge interference from 5-6 GHz WLAN band. The planned antenna is fabricated and labelled in terms of impedance and radiation parameter measurements, compliant with that of properties achieved from full wave simulation. The antenna has congruous gain and well-built radiation pattern. Radiation pattern portrayal confirms high gain in the end-fire direction.
This article reports the development and test of a radio-propagation measurement system based on an 8-bit software-defined radio. Tests are performed in an urban area at the frequency of 733 MHz and compared with numerical prediction from the Altair WinProp commercial suite. The system is portable (1.2 kg), low-cost, based on non-proprietary open-source tools and has the capability of tracking the GPS coordinates of the measured points. Frequency limit of the system is bounded by the software-defined radio in use, and the limit of this present case spans 24 MHz to 1700 MHz. The integrated system does not need user intervention after its initial setup can be operated autonomously.