This paper presents the design of a novel lowpass–bandpass diplexer with compact size and good performance using microstrip cells. For this purpose, two microstrip lowpass and bandpass filters are separately designed and mathematically analyzed. The proposed microstrip diplexer has a novel and simple structure. It occupies a compact area of 0.037 λg2 (722 mm2), and its insertion loss and S11 at both channels are low. The insertion loss at the lower and upper channels is only 0.047 and 0.16 dB, respectively. Meanwhile, both channels are flat with the maximum group delay of 1.68 ns which is the lowest compared to the previously reported diplexers mentioned in this paper. To design the proposed diplexer, first, a lowpass diplexer with good performance is designed which has low losses and a good figure of merit. It has a flat passband with a sharp roll-off. Then, to achieve the proposed diplexer, a bandpass resonator is added to the lowpass filter without any extra matching circuit, which saves the overall size. The proposed diplexer is designed, simulated, and fabricated, where the simulation and measurement results are close.

In this paper, a passive double-balanced mixer in SiGe HBT technology is presented. Owing to lack of suitable passive mixing elements in the technology, the mixing elements are formed by diode-connected HBTs. The mixer uses lumped element Marchand baluns on both the local oscillator (LO) and the radio frequency (RF) port. A break out of the Marchand balun is measured. This demonstrates good phase and magnitude match of 0.7° and 0.11 dB, respectively. The Marchand baluns are broadband with a measured 3 dB bandwidth of 6.4 GHz, while still having a magnitude imbalance better than 0.4 dB and a phase imbalance better than 5°. Unfortunately with a rather high loss of 2.5 dB, mainly due to the low Q-factor of the inductors used. The mixer is optimized for use in doppler radars and is highly linear with a 1 dB compression point above 12 dBm IIP2 of 66 dBm. The conversion gain at the center frequency of 8.5 GHz is −9.8 dB at an LO drive level of 15 dBm. The whole mixer is very broadband with 3 dB bandwidth from 7 to 12 GHz covering the entire X-band. The LO–IF, RF–IF, and RF–LO isolation is better than 46, 36, and 36 dB, respectively, in the entire band of operation.

In this paper, a novel design of compact wideband multiple-input multiple-output (MIMO) antenna operating over a frequency range of 1.8–4.0 GHz at 10 dB is presented for mobile terminals. The MIMO antenna design consists of two symmetrical and orthogonal radiating elements with a small size of 15.5 × 16.5 mm2 printed on the corners of a mobile circuit board. The radiating element is composed of four meandered monopole branches with a strip-line fed by a probe. By triangularly trimming the corners of the common ground plane beneath the radiating elements, not only the mutual coupling is reduced, but also impedance bandwidth is increased. Although, the antenna in this form has sufficient correlation level between the radiating elements for MIMO operation, a novel design of plus-shaped parasitic element is inserted to the ground plane between those radiating elements in order to further enhance the isolation. The performance of the MIMO antenna is investigated in terms of s-parameters, radiation pattern, gain, envelope correlation coefficient (ECC), and total active reflection coefficient (TARC), and is verified through the measurements. The results demonstrate that the proposed MIMO antenna has good characteristics of wideband, isolation, gain, radiation pattern, and is compatible with LTE, WiMAX, and WLAN, besides it is small, compact, and embeddable in mobile terminals.

In this paper, we propose a novel integrated ultra-wideband (UWB) monopole antenna with dual-band antenna. The antenna consists of planar rectangular with semi-elliptical base and a rectangular dielectric resonator antenna (DRA) with dual-band operation. Both of them are excited via coplanar waveguide (CPW) lines. The experimental measurements show that the planar monopole provides an impedance bandwidth between 2.44 and 11.9 GHz which largely covers the entire UWB spectrum, and the rectangular DRA operates at two bands; 5.3–6.2 and 8.5–9.4 GHz. Additionally, the proposed structure ensures low mutual coupling between the two ports (with S21 less than −20 dB in the whole operating frequency band). The measured and numerical results show a good agreement.

Thinning a large concentric ring array by an evolutionary algorithm needs to handle a large amount of variables. The computational time to find out the optimum elements set increases with the increase of array size. Moreover, thinning significantly reduces the directivity of the array. In this paper, the authors propose a pattern synthesis method to reduce the peak sidelobe level (peak SLL) while keeping first null beamwidth (FNBW) of the array fixed by thinning the outermost rings of the array based on Gravitational Search Algorithm (GSA). Two different cases have been studied. In the first case only the outermost ring of the array is thinned and in the second case the two outermost rings are thinned. The FNBW of the optimized array is kept equal to or less than that of a fully populated, uniformly excited and 0.5 λ spaced concentric ring array of same number of elements and rings. The directivity of the optimized array for the above two cases are compared with an array optimized by thinning all the rings, while keeping the design criteria same as the above two cases. The optimized array by thinning the outermost rings gives higher directivity over the optimized array by thinning all the rings. Time required for computing the optimum elements state for the above two cases using GSA are shown lesser compared to the optimized array by thinning all the rings using the same algorithm. The peak SLL and the FNBW of the optimized array for the above two cases are also compared with the optimized array by thinning all the rings.

This Paper reveals a novel single layer five band frequency selective surface (FSS). Novelties of the proposed FSS lie in its five closely spaced stop bands at 2.4, 3.38, 4.82, 6.32, and 7.75 GHz as well as the reduced single layer structural thickness (0.0016 λ0) and the miniaturized unit cell size (0.0656 λ0) at lower resonant frequency as compared to the existing multiband FSS. The unit cell structure consists of six octagonal concentric interconnected loops. Adjacent loop interconnection technique reduces the cell size by more than 44%. Furthermore, arrow-shaped rings are also introduced on each corner of the outermost octagonal loop, and using this technique approximate 23% cell miniaturization can be achieved. In addition, the proposed FSS exhibits excellent angular stability.

This paper presents the design and analysis of a wideband X/Ku and Ku band reflectarray antenna. The proposed unit cell of the reflectarray antenna comprises a patch loaded with two distinct slots, viz. a square ring and a cross loop, printed on a low loss substrate, which is backed by a foam-loaded ground plane. The unit cell element offers a linear and large dynamic reflection phase range, which is achieved by optimizing the shape, location, and geometrical parameters of the two slots loaded on the patch. A 324 element microstrip reflectarray antenna of size 200 × 200 mm2 is constructed and analyzed for its radiation characteristics by simulation and measurement. The reflectarray offers a 3 dB gain bandwidth of 50.75% with the operating frequency range of 10–16.8 GHz. It offers a peak gain and aperture efficiency of 25.4 dB and 40% at 12.6 GHz, respectively. The cross-polarization level is below −40 dB over the entire operating frequency range.

This paper presents the design and analysis of a miniaturized, coplanar waveguide-fed ultra-wideband monopole on-chip antenna with band-notch characteristics. By incorporating a “U”-shaped slot in the feedline, a band-notch is realized in the frequency range of 7.9–8.4 GHz to avoid interference from the X-band uplink satellite communication system. The proposed antenna achieved good voltage standing wave ratio (VSWR) characteristics with VSWR value <2 for the frequency range of 2.5–20.1 GHz excluding the band-notched frequencies. The fractional bandwidth and bandwidth ratio are obtained as 156% and 8.04:1, respectively. Dominant factors that affect the center frequency and bandwidth of the notched band are thoroughly investigated. This paper addresses both frequency as well as time domain behavior of the proposed structure. Standard 675 µm thick, high resistive silicon substrate (ρ≥8 kΩ-cm, εr = 11.8, and tan δ = 0.01) is used to design the proposed compact antenna structure with a layout area of 8.5 × 11.5 mm2. Fabrication process steps along with simulated and measured data are presented here. A close analogy between simulated and measured data is observed.

A highly efficient design procedure for dielectric-loading multi-band coaxial-type feed antennas is proposed in this paper. Cylindrical modal matching method is employed for generalized scattering matrix calculation inside the feed, while spherical wave expansion is adopted for the feed aperture discontinuity in consideration of the outer shape. Closed-form scattering matrices with respect to different junctions help realize higher computational efficiency than the full-wave simulation solvers, and thus enable rapid optimization in terms of various electrical functional requirements across multiple frequency bands simultaneously. A Ku/Ka multi-band feed is investigated as a numerical example. Excellent radiation performances, including the low cross-polarization level, constant beamwidth, stable phase center, high return loss, and high isolation between bands of interest are achieved by employing multi-scalar rings, dielectric loading, and a three-port hybrid junction. The design is validated by experimental results from a manufactured prototype. Good consistency confirms the accuracy of our numerical approach, and demonstrates the proposed feed a good candidate for Ku/Ka-band satellite communication antenna systems.

In this paper, a microstrip lowpass filter with wide stopband and sharp roll-off is presented. The proposed filter consists of a modified radial stub resonator which is cascaded by four suppressing cells. To reduce the overall size, the transmission lines are folded. The cut-off frequency of the proposed filter is 1.19 GHz. The transition band is approximately 0.2 GHz from 1.19 to 1.39 GHz with corresponding attenuation levels of 3–20 dB. The stopband is from 1.39 to 19 GHz with attenuation level of <20 dB. The insertion loss and return loss in the passband from DC to 0.8 GHz are better than 0.26 and 14 dB, respectively. The proposed filter is fabricated and measured. The simulated and measured results are in good agreement.

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of 865–867 MHz. The size of the proposed tag antenna is 43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of 20.55 − j191.45 Ω at centre frequency 866 MHz. The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from 87.5 to 35 cms depending on mounting on non-metal and metal packages, respectively.

A new flexible and miniaturized power divider (PD), based on the Wilkinson PD topology, is carried out in this paper. Flexibility and size reduction are achieved simultaneously thanks to both an open-stub loading the input port and additional transmission lines (TLines) connecting the output ports to the isolation resistance. Design equations and rules are given. As a proof-of-concept, two PDs working at 2.45 GHz were fabricated and measured. Then, on the basis of the previous developments, a 1:4 power-dividing feeding network was realized. It highlights the high performance and flexibility of the proposed PD. Agreement between simulation and measurement results is very good, for PDs as well as for the feeding network, thus validating the proposed approach. This concept is straightforward to be applied at higher frequencies, in particular in the millimeter-wave range on CMOS technologies, where flexibility in the choice of the TLines characteristic impedances and size reduction are mandatory.

In this paper, the analysis and simulation of a novel geometrical structure of the frequency selective surface (FSS), which has been achieved through the conductive loading of the simple circular ring with wedge-shaped metal vanes has been discussed. The electrical performance and behavior of the proposed structure have been studied in Ku band (12–18 GHz) of the electromagnetic spectrum for satellite communication. We have radially optimized the proposed structure to enhance the performance, such as reflection and transmission bandwidth. We have also discussed the effect of incident electric field at 0°, 10°, 30°, and 50° on the electrical performance of the proposed FSS. In addition to this, the effect of angular sensitivity on the proposed structure through increasing the number of conductive loaded wedge-shaped metal vanes is also explored. However, the structural parameters of the proposed FSS have been obtained through the synthesis technique. The analytical results obtained from the synthesis technique have been supported by the simulation results achieved through CST Microwave Studio as well as Ansoft high frequency structural simulator (HFSS), which are commercially available simulators based on the finite integral and finite-element technique, respectively. Furthermore, for validation of the numerical results, the Ansoft circuit simulator which is based on mixed potential integral equations (MPIE) and solved by the method-of-moment has also been used to obtain the reflection and transmission parameters through the values of inductance and capacitance, which have been achieved by the numerical analysis.

In this research study, a compact dual-polarized co-radiator ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with improved impedance bandwidth and isolation is proposed for wireless applications. The designed co-radiator has an overall area of 0.3λo × 0.3λo mm2 (where, λo is free space wavelength corresponding to the lower cut-off frequency, i.e., 3.1 GHz). The proposed resonator comprises of a hybrid geometry which is created with the combinations of a circular-shaped patch, a square, and two rectangular stubs. It is centrally aligned between two 50 Ω micro-strip feed lines that are positioned orthogonal to each other. Further, the modified ground plane is attached with the end-loaded line which provides broadband isolation over entire UWB frequency band. The simulated results of the proposed antenna exhibit wideband characteristics with impedance bandwidth of 3.1–16.9 GHz with minimum isolation of −15 dB. Moreover, all the radiation performance parameters are analyzed and discussed. Some important diversity parameters such as envelope correlation coefficient, mean effective gain, effective diversity gain, and channel capacity loss have also been evaluated. Furthermore, all the measured results of proposed antenna agree well with the simulated results which make the proposed antenna a suitable candidate for UWB-MIMO wireless applications.

The silicon/porous silicon (PS) hybrid substrate is an interesting candidate for the monolithic integration of radiofrequency (RF) circuits. Thus, passive components can be integrated on the insulating PS regions close to the active devices integrated on silicon. Regarding silicon, hybrid substrates allow the improvement of RF circuits performances. To demonstrate it, coplanar waveguides have been integrated on glass, silicon, and localized PS substrates. The characterization results show that the substrate losses are reduced with PS.

The paper proposes a new design for a single-arm, rectangular, spiral antenna (SARSA) with a wide azimuth space coverage. The antenna, operating at around 3.3 GHz, is capable of steering the beam in four separate directions in the azimuth plane. Only three DC signals are required to control the seven PIN diodes attached along the spiral arm. The antenna has a 200-MHz-bandwidth around 3.3 GHz with stable maximum beam directions that are defined by setting of the switches. Considerations required in selecting switch positions when designing such antennas for other frequencies, are presented. The measured return loss, radiation pattern and gain, all have close correlation with the simulation results. A detailed comparison of our design with those already proposed in the literature is given.

In order to encrypt/encode data based on the magnitude level of the radar cross-section (RCS), we propose an approach with a precise estimation considering the resonant characteristics of a multipatch backscatter-based chipless radio frequency identification (RFID) dedicated for chipless tags depolarization. The working principle is based on the polarization mismatch between the tag and the reader antenna to control the magnitude of the backscatter, which allows a reliable detection in real environments. We introduce in this paper a new 4-bit chipless RFID tag with an enhanced RCS, based on a triangular patch antenna with multiple resonators. Additionally, we propose an ultra-wideband impulse radar (UWB-IR)-based reader that interrogates the chipless tag with a UWB pulse, and the received backscatter was studied in both time- and frequency-domains. The antenna was operating from 4.7 to 6.1 GHz, a band allocated for RFID systems. The obtained experimental measurement results in the environment of anechoic chamber were exceptionally relevant to validate the simulation results.

A new circularly polarized planar array antenna using linearly polarized microstrip patches is designed and optimized for X-band wireless communication applications. Four square patch elements with feed network are used to design the circularly polarized array antenna. The feed network consists of microstrip lines on the obverse side of the dielectric substrate and slot line on the reverse side of the substrate. Both-sided MIC technology is successfully employed to apply its inherent advantages in the design process of the array structure. The unequal feed line is used to create 90° phase difference between the linearly polarized patches. Therefore, the circular polarization is realized by the combination of linearly polarized patches and unequal feed line. Characteristics of the proposed array are investigated by using two electromagnetic (EM) simulators: advanced design system and EMPro. The −10 dB impedance bandwidth of the antenna is around 5%. The 3 dB axial ratio bandwidth of 1.48% is obtained. The design of the proposed antenna along with parametric study is presented and discussed.

In this work, the authors report the operation of a cylindrical dielectric resonator antenna (CDRA) in the high gain HEM13δ mode, for the first time. This mode, excited with a standard microstrip slot, radiates in the broadside direction with gain in the range of 8−10 dBi. It is shown that through feed optimization, the HEM13δ mode can be excited dominantly by suppressing the fundamental HEM11δ mode of the CDRA. Detailed simulation studies show that the HEM13δ mode is supported by cylindrical dielectric resonators with an aspect ratio (radius to height ratio or a/d) >1, and it resonates at a frequency approximately 2.2 times that of the fundamental HEM11δ mode. The above features of the HEM13δ mode CDRA can be used as approximate design rules. For a CDRA with dielectric constant ɛr = 24, diameter 2a = 19.43 mm, and height d = 7.3 mm (a/d = 1.3), the HEM13δ mode is excited at 6.125 GHz with a peak gain of 10.14 dBi in simulation. Corresponding values from prototype measurement are 5.981 GHz and 9.62 dBi, respectively for the resonant frequency and the gain, verifying the simulation.

Antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.