Semiconductor deposition on magnetron's cathode surface using different materials such as gallium nitride (GaN) and silicon carbide (SiC) semiconductors is conducted to grow approximately 80, 100 and 120 nm plasma layers. The cathode is then used to generate high frequency and low-power microwave for further comparison and analysis with the conventional magnetron operation. Parameter of analysis to identify the efficiency includes electron drift velocity, harmonic order, total harmonic distortion, low harmonic distortion, and spectrum observation. The sputtered cathode of the magnetron is used to generate a low-power microwave observing a generator efficiency up to 93 and 88% for GaN and SiC materials, respectively, compared to the conventional material, which observes 37% of efficiency at 2450 MHz, 5 W. Also reported is the quality of semiconductor sputtering on the magnetron cathode, which was manipulated by the deposition period, temperature, and plasma layer growth thickness.

The microstrip active patch antenna behaves like a resonant circuit/cavity with multiple resonant frequencies; furthermore, depending on the non-linearity of the device, it generates significant amount of second harmonic radiation. The location of the device on the patch that maximizes the fundamental radiated power output is found to be not the position corresponding to the minimum second harmonic content in radiated power. An optimum location of the diode on the patch has been suggested. The paper also discusses the modification of the behavior of the active antenna, which is first an oscillator; and then a radiator, under injection-locked condition. The results are presented with respect to a Gunn-mounted rectangular patch.

This paper presents the first experimental results of a novel MEMS-based waveguide filter for mobile back-hauling at K-band with adjustable center frequency. The tuning concept employs commercial packaged RF MEMS switches, wire-bonded within a rectangular cavity. The switches are used to perturb the current distribution of the TE101 mode so as to tune the resonant frequency of the cavity. A tuning range up to 2% with unloaded Qs of the order of 1000 in K-band can be obtained. A second-order filter prototype employing commercially available MEMS on silicon substrate has been tested. Measurements show a 160 MHz frequency shift (0.7%) and Qs up to 1000 using only one MEMS per resonator. New higher-order prototypes using low-loss substrate MEMS (e.g. quartz) will be fabricated in order to get higher Qs. The concept here present leads to a very simple structure. The number of MEMS per resonator is, in fact, minimized (we use only one MEMS) and the design is simple. On the other hand, the achievable tuning range is lower (<2%) than the other concepts. Higher tuning ranges are achievable using more MEMS, but at the expense of lower Qs of the resonators.

We report on the development of W-band (75–110 GHz) heterodyne receiver technology for large-format astronomical arrays. The receiver system is designed to be both mass producible, so that the designs could be scaled to thousands of receiver elements, and modular. Most of the receiver functionality is integrated into compact monolithic microwave integrated circuit (MMIC) amplifier-based multichip modules. The MMIC modules include a chain of InP MMIC low-noise amplifiers, coupled-line bandpass filters, and sub-harmonic Schottky diode mixers. The receiver signals will be routed to and from the MMIC modules on a multilayer high-frequency laminate, which includes splitters, amplifiers, and frequency triplers. A prototype MMIC module has exhibited a band-averaged noise temperature of 41 K from 82 to 100 GHz and a gain of 29 dB at 15 K, which is the state-of-the-art for heterodyne multichip modules.

A frequency diverse array (FDA) radar has attracted wide attention, due to its capability to provide a range-angle dependent beampattern and to scan the spatial without phase shifters or rotating arrays. However, FDA systems will suffer from low echo signal energy or high sidelobe peaks when detecting targets by beamforming based on existing receivers. To reduce the sidelobe peak of detection results while increasing the echo signal energy, in this paper, we propose an FDA radar system based on diversity linear frequency modulation waveforms. Correspondingly, we propose a receiver architecture with a time-variant beamforming chain. The proposed system retains the ability of the FDA system to automatically spatial beam scanning, owing to the frequency increment across elements. By increasing the pulse duration of transmitted signals, we enhance the echo signal energy. By applying the artificial bee colony algorithm to design the bandwidth of each chirp signal, the proposed system reduces the sidelobe level of detection results while increasing pulse width. Numerical simulation results are presented to demonstrate the effectiveness of the proposed system.

In this study, we propose an artificial neural network in conjunction with spectral domain approach (SDA), for fast and accurate determination of the resonant frequency and half-power bandwidth of rectangular patch over the ground plane with rectangular aperture. The performances evaluation of the neurospectral method reveals superiority over the conventional SDA model in terms of errors and time. The results obtained from the neurospectral method are in very good agreement with the experimental and theoretical results available in the literature. Finally, numerical results for the effect of rectangular aperture dimensions on the resonant characteristics of the rectangular patch are also investigated.

In this paper, a new multi-layered triple-passband bandpass filter using embedded and stub-loaded stepped impedance resonators (SIRs) is proposed. The filter is designed to have triple-passband at 1.8, 2.4, and 3.5 GHz. The 1st and 2nd passbands (1.8/2.4 GHz) are simultaneously generated by controlling the impedance and length ratios of the embedded SIRs (on top layer). The 3rd passband (3.5 GHz) is generated by using the stub-loaded SIR (on bottom layer). Using the embedded SIR, the even modes can be tuned within very wide frequency range and without affecting the odd modes. Therefore, the design of multi-band filters with very close passbands can be easily achieved and having a high isolation between the passbands. The filter can provide the multi-path propagation to enhance the frequency response and achieving the compact circuit size. The measured results are in good agreement with the full-wave electromagnetic simulation results.

In this paper, a novel and compact center-fed dual-band WiFi printed antenna is presented. This antenna is designed using two different arms which correspond to the oscillation points of the dual band, and uses parasitic capacitance and U-shaped microstrip line to match and control the necessary bandwidth. The measured frequency bandwidth of this antenna is 2.3–2.61 GHz (310 MHz, 12.7%) at 2 GHz, and the high-frequency bandwidth is 4.82–5.84 GHz (1020 MHz, 19.1%) at 5 GHz, which meets the requirements for applications in global WiFi communication. This PCB antenna is double-sided, long, and narrow; its size is 7 × 45.9 × 1 mm3; it can be applied to wireless access point; and it has a near-omni-directional radiation pattern. The design, analysis, and measured results of this proposed antenna will be presented.

The development in high-end microwave transceiver systems toward the software defined radio has brought about the need for tunable frontend filters. Although the problem is being tackled by the microwave community, there still appears to be an unmet demand for practical tunable filter technologies. With this motivation, this work presents a tuning method that delivers a resonator Q0 of 2000–3621 within a minimum tuning ratio of 1:1.42. A continuously tunable notch filter based on this tuning method is presented. The design is manufactured, measured, and verified. It is shown that the tuning technology compares favorably to other selected technologies.

This paper reports on the ohmic contacts of an radio-frequency micro-electro-mechanical-system (RF MEMS) switch. The structure of the MEMS is described briefly to give information about the organization of the switch device. The most significant performance data are reported, indicating very low actuation voltage below 5 V, switching time of <10 µs and good RF performance for frequencies up to 5 GHz. Since the contact performance is a key for excellent RF performance in the actuated state and for high reliability as well the article is focused on the contacts. It is supposed that asperities are building the current path in a closed contact, which is proved by measurements of the closing process with high time resolution. The measurements exhibit very good power-handling capabilities of the contacts. The reported findings render prior theoretical experiments with a physical device.

In this paper, staircase-shaped ultra-wideband (UWB) response is proposed. UWB technology being emerging technology of decade needs development of antennas with small size. This paper proposed the design of antennas for UWB technology with small overall size. The feed used in the proposed design is microstrip feed line. The defected ground structure and staircase patch have been used to enhance bandwidth (BW) of antenna, to miniaturize its shape and to reduce the surface wave. The proposed design is carried out with different types of substrate materials and the best results are considered. The proposed antenna performs well in terms of BW and gain while reduction in size is reported. The proposed antenna can be used for Wireless Personal Area Network.

Continuous mode class-J radio-frequency (RF) power amplifier is a promising technique that extends the operating bandwidth of the conventional class-B power amplifier. However, the maximum theoretical efficiency is limited to that of the class-B power amplifier. In this paper, an enhanced mode of operation for the class-J power amplifier is proposed by incorporating a third harmonic voltage component to produce an optimum waveform for maximizing the fundamental voltage component and thereby to increase the drain efficiency and introduce a new design space. A detailed derivation for the necessary relations of output power, drain efficiency, and the required harmonic load impedances is provided, showing a significant improvement in theoretical maximum efficiency from 78.5 to 89.8%. In order to confirm the developed analytic approach, a 10 W prototype amplifier model was designed and fabricated to operate within the global system for mobile communications (GSM) frequency band 850–950 MHz using a commercial GaN power high electron mobility transistor (HEMT). The experimental results have indicated that the drain efficiency of the circuit varies from 68 to 80% within the desired band.

A significant measureable development of inductance gain per unit of space in loop fractals for a suite of inductors which occupy the same layout space and require only a single-fabrication layer is investigated. All structures are fabricated on a borofloat glass substrate with dielectric constant loss tangent of 0.004. A chrome layer of 30 nm for adhesion followed by a 180 nm gold layer were sputtered and etched. To increase the surface area is implemented a simple geometrical strategy through fractalization and consequently the inductive performances is improved. Also, the higher fractal orders can be developed the inductive performance over 9 times from 0th to 3rd order. The fractal derivations of the original loop due to its space filling properties are examined and it suggests that although the effective electrode length increases, overall, the arrangement still essentially occupies the same space. In terms of design space for 0th, 3O-5O-7O of 1st, 2nd, and 3rd orders of fractals, 0, 26.2, 34.6, 38.6, 65.5, and 75.8% of occupied conductor surface area are saved. The measured inductances and resistances for aforementioned orders of fractals are 4.6 nH and 5 Ω, 8.6 nH and 10.5 Ω, 12 nH and 11.6 Ω, 12.8 nH and 17.3 Ω, 19.2 nH and 23.2 Ω, and 44.7 nH and 63.5 Ω, respectively.

This work describes the integration of Schottky diodes into fast GaN MMIC process technology suitable for the realization of switch-mode power amplifier core chips for class-S operation at 2 GHz. With the demonstration of this technology, the so-called third-quadrant issue, which reduces the efficiency in band pass-Δ-Σ class-S operation can be diminished on device level. Compared to a hybrid diode assembly, the broadband properties of the amplifier module with on-chip-integrated diode can be improved by the reduction of parasitic losses. The GaN heterostructure field effect transistors (HFETs) with integrated series diode show a cut-off frequency of 28 GHz with drain breakdown voltages exceeding −100 and +100 V and comparable large signal performance to conventional GaN HFETs at 10 GHz. MMIC core chips for class-D and class-S switch-mode power amplifier modules are demonstrated for the operation at mobile communication frequencies between 0.45 and 2 GHz and signal bit rates up to 8 Gbps. The circuits yield broadband output power levels between 4 and 9 W with efficiencies of up to 80%.

A simple method for the full characterization of passive n-port microwave monolithic integrated circuit (MMIC) structures using standard two-port vector network analyzer (VNA) measurements is presented. Its main advantages are: it does not require to perform measurements from all the ports of the network, no special calibration procedure is needed, the auxiliary terminations required by the procedure can be integrated at the border of the structure under test with minimal area increase, and it can be easily implemented in commercial CAD software. The method was applied to a nine-port microstrip structure corresponding to the output power combiner and impedance matching network of an X-band MMIC high power amplifier (HPA). The full S-parameter matrix was derived from two-port measurements and compared to the circuit–as well as electromagnetic (EM)-based simulations of the structure.

A low-profile slant ±45° polarized antenna for a 4G/5G base station with a dominant path wave propagation model (DPM) is reported in this paper. For dual-polarization and wide impedance bandwidth, the two dipole radiators are crisscrossed and a square metallic ring is integrated with the dipole arms and screwed with the four shorting vias. The antenna operates in Band 40/41/42/43 with strong isolation and low ECC (Envelop Correlation Coefficient). Fabricated antenna results show that the predicted wideband antenna has 13.38% bandwidth in 4G, which is Band 40/41, and 29.33% bandwidth in 5G sub-6 GHz Band 42/43. The antenna has a consistent radiation pattern, a 40 dB XPD (Cross Pol Discrimination), and a beam width of 69.5° ±1.5° in the entire frequency band. Three base station sites were explored to deploy the radiation pattern of a dual-polarized antenna in the 3D EM (Electromagnetic Analysis) tool. To evaluate signal quality, strength, radio network planning, and wave propagation analysis by analyzing antenna performance in real-time scenarios with 64 and 256 QAM (Quadrature Amplitude Modulation) techniques. For the proposed four-stream MIMO (Multiple-Input-Multiple-Output) antenna arrangement at deployed cell sites for 4G/5G base station applications, the maximum downlink and uplink data rates are 3.826/2.8 Mbps and 1044/800 Mbps respectively.

A stepped-impedance configuration for coaxial resonators is employed to realize filters in the L-, S-, and C-bands exhibiting a wide spurious-free range. The geometry of a single rod resonator is optimized, by enlarging its top head, in order to maximize the ratio between the frequency of the first higher-order mode and that of the fundamental mode. This leads to the design of a very compact filter with high Q-factors and wide spurious-free bands, up to nearly 5 times the center frequency. To prove the effectiveness of the approach, a sixth-order filter has been designed and manufactured; the comparison between the full-wave simulations and the measurement show excellent agreement.

Design and fabrication of a traveling-wave printed planar composite right/left-handed (CRLH) antenna are presented in this paper. The proposed traveling-wave antenna constructed of four unit cells with b-shaped geometries, which each occupy 2.49 mm length, 6.32 mm width, and 0.8 mm height. In this paper, with designing the optimized b-shaped printed planar structure by the standard manufacturing techniques on the printed circuit boards, which perform the roles of the series left-handed (LH) capacitances (CL), the antenna size, bandwidth, and radiation specifications may be improved to the desirable range. Also, to obtaining the desired results the spiral inductors have been used, which play the roles of the shunt LH inductances (LL). The fabricated antenna with the proposed structure can be covered more from 2 GHz measured impedance bandwidth with minimum of the measured gain and radiation efficiency equal to 6.1 dBi and 52.3%, respectively, which happen at 9 GHz. According to the provided results, the proposed compact ultra-wideband traveling-wave antenna is a potential candidate to use in the embedded electronic systems and portable wireless communication devices.

In this paper, a new configuration of dual-band, dual-polarized microstrip antenna applicable to mobile base stations is proposed. The concept behind the new design is the use of an artificial magnetic conductor (AMC) structure that operates in the required two bands beneath a radiating diamond shaped slot. The choice of the diamond-shaped slot is due to its support of an infinite number of resonant modes where the dimensions of the diamond shape have more degree of freedom that controls the excited modes when compared to the rectangular slot. The proposed antenna works over the 870–960 MHz (GSM850/GSM900) band and the 1710–2170 MHz (DCS1800/PCS1900/UMTS2100) bands for mobile communication systems. The antenna is suitable for transmitting and receiving mobile signals since it has two ports of orthogonal polarization. The antenna is fabricated on a combination of FR4 dielectric substrate and foam layers in order to achieve low cost. The proposed antenna yields high isolation between its two ports not exceeding −30 dB and a front-to-back ratio exceeding 15 dB. The average antenna gains are about 6.6 dBi at the GSM850/GSM900, 7.1 dBi at the DCS1800/PCS1900, and 6.8 dBi at the UMTS2100 bands. The theory of radiation is proved analytically and verified by comparing its results with some simulated results. Finally, a good agreement between the simulated and measured results is noticed.

Magneto-dielectric antennas (MDAs) provide small sizes, enhanced bandwidths, and frequency/polarization agility. We describe the fabrication and efficiency characterization at 0.4–0.8 GHz of five microstrip MDAs, whose gradually thicker substrates were 3D-printed using an off-the-shelf polylactic acid (PLA) filament doped with ferromagnetic particles. It was experimentally discovered that efficiency increases monotonically from 12% (−9.2 dB) to 37% (−4.3 dB) as substrate thickness goes from 1.6 to 4.3 mm; the rate is faster than expected for microstrip antennas. Numerical analysis indicated that the apparent magnetic loss tangent of the MD substrate experiences a threefold decrease as the 3D printer deposits more layers of iron-doped PLA. The MDAs exhibit radiation quality factors that are 3.7–7.2 times better than the dielectric counterparts. Moreover, a simple optimization of ground plane size could increase efficiency to 55% (−2.6 dB). The reduction in magnetic loss is attributed to a reduction in eddy current loss due to the separation of agglomerate iron particles. Therefore, despite the inherently lossy material used, the potential of 3D-printed MD substrates in providing acceptable antenna efficiencies is demonstrated together with unprecedented design freedom and fabrication flexibility.