This article presents a comprehensive and intuitive analysis of the impact of packaging on diode performance and a two-step method for packaging parameter extraction. This is performed using a single forward bias point, one-port measurements and probe tips on a conventional printed circuit board (PCB). A PIN diode was used to validate the method, biased from reverse (−5 V) to forward (1.22 V) bias. Measurements were performed up to 27 gigahertz (GHz). The complete diode characterization process—from the design and the electrical modeling of the test fixture to the extraction of the unpackaged diode measurements—is detailed. The parameters of the package model were extracted, its effects were removed from the measurement, and the behavior of the unpackaged diode was determined. Three operating regions based on their radiofrequency and direct current (RF-DC) behavior were proposed, and an electrical model of the unpackaged diode was derived for each region. The results showed that the influence of the package caused the diode to remain in an unchanged behavior under different biases, indicating that it no longer rectified. The results presented herein are validated by the excellent correlation between the diode’s measured S-parameters, impedance, and admittance and their corresponding models.

This paper presents the design of a double-patch, double-beam directional microstrip patch antenna, with circular polarization and enhanced bandwidth. The antenna design was accomplished by first creating a square patch resonating at the desired frequency. Subsequently, the ground plane was replaced by a second patch, identical to the initially designed one, resulting in a significant back lobe, nearly equivalent in size to the main lobe. Additionally, cuts were made at the corners of the patches to enhance antenna bandwidth and achieve circular polarization. This resulted in an antenna with an enhanced bandwidth of $\mathbf{1 . 6 9}$ $\mathbf{G H z}$ (27.17-28.86 GHz), covering the 28 GHz band (27.5-28.35 GHz). Moreover, it exhibits circular polarization within the frequency range of 27.88 GHz to 28.09 GHz, and a gain of 6.03 dBi for the principal lobe. The back one attains a comparable value. The antenna achieves an efficiency of $\mathbf{9 0 \%}$. The antenna size is $0.31 \lambda_{0} \times 0.31 \lambda_{0}$.

Millimeter wave frequencies have become a key element for the development of the 5th (5G) and 6th (6G) generations of wireless communications. These bands provide wide bandwidth and high-speed data transfer. Antennas for these frequency ranges should attain high gain in order to compensate for atmospheric losses, and should be easily manufacturable and of low cost. In this article we present the design, manufacture and measurement of a three-element series-fed antenna that achieves a wide bandwidth covering the n259 and n260 bands, from 36.05 GHz to 45 GHz, gain better than 10 dBi, and a reduced size of 15 mm X 31.835 mm. This antenna has the dimensions and properties to be successfully incorporated in wireless devices, especially for 5G applications. To the best of our knowledge, no other antenna with these characteristics has been reported.

The rapid evolution of wireless technology demands an ever-growing number of connected devices, and hence, a greater availability of antennas for a gamut of applications in different frequency ranges [1]–[3]. The size, materials, and geometry of antennas, however, depend on the application as well as on important considerations, including resonant frequency, bandwidth, gain, efficiency, shape of the radiation pattern, input impedance, and many more [4]. Hence, a universal measuring technique for antennas cannot be derived, and in general, each case requires that it be treated individually. In addition, as frequency of measurement increases, more effects must be taken into account when interpreting data; one of relevance is that introduced by the surface roughness at the interface between the printed circuit board (PCB) substrate and the metal foil that serves as a conductor [5]–[6]. In fact, the surface roughness of the copper foil is necessary to achieve good adherence to the dielectric substrate, and thus, it is voluntarily included in the manufacturing process. Unfortunately, the variation of the metal surface from the ideal smooth case increases the resistance of the foil at microwave frequencies. In consequence, it negatively impacts the electrical performance of structures and should be considered when assessing the response of antennas on PCB.

In this paper we present the design of a compact low-cost microwave sensor and a method to determine the relative permittivity and loss tangent of liquid samples. The experiments have been done using full-wave simulations. The microwave sensor is built on a PLA substrate and copper adhesive tape, and its total size is 3,324.35 mm 3 . The determination of relative permittivity is done by curve-fitting based on the shift of the loaded resonant frequency with respect to the unloaded resonant frequency of the sensor, whereas the loss tangent is predicted from the data obtained from the normalized difference in areas of the reflection coefficient, referred to the response of the sensor with a lossless sample. The sensor can respond in a stable way even with high loss-tangents, and low or high relative permittivity samples, as is the case with most liquids.

In this paper, we present a dual-band antenna working at 2.45 GHz and 5.8 GHz. The design is based on two radiating rectangular slots with one upper Split Ring Resonator (SRR) to enhance the radiation pattern at 5.8 GHz, one Complementary Split Ring Resonator (CSRR), and three Split Rings (SR) to improve the input reflection coefficient. The dual-band antenna covers the 2.45 GHz and 5.8 GHz Industrial, Scientific and Medical (ISM) bands. The total size of the proposed antenna is 31 × 70 × 70 mm3. The proposed antenna was manufactured and tested. The attained gain is better than 7.5 dBi, and 6.5 dBi at 2.4 GHz and 5.8 GHz, respectively. The measured gain and input reflection coefficient have good correlation with the simulated results, covering the ISM bands around 2.45 GHz and 5.8 GHz. The performance of the proposed antenna is remarkable and suitable for applications where the size is not a severe limitation, such as sensors, LPWAN/WLAN modules, health care devices, base stations, IoT, and control applications.

In this paper, a multi-band Vivaldi antenna design on a 3D-printed substrate is presented. The frequency reconfiguration is achieved using different small dielectric bars. The proposed antenna was built using a low-cost PLA printed substrate and two layers of copper adhesive tape. The simulated and measured results confirm the good performance of this design operating as a frequency reconfigurable antenna covering the band from 3.5 GHz to 13.6 GHz. The design is suitable for applications in the C and X bands, including the 5.8 GHz ISM band, for uses in radar, medical devices, and IoT devices.

It is well known that the fluctuations in experimentally obtained characteristic impedance versus frequency curves are associated with resonances originated by standing waves bouncing back and forth between the transitions at the transmission line terminations. In fact, microwave engineers are aware of the difficulty to completely remove the parasitic effect of these transitions, which makes obtaining smooth and physically expected frequency-dependent curves for the characteristic impedance a tough task. Here, we point out for the first time that these curves exhibit additional fluctuations within the microwave range due to standing waves taking place within the transition itself. Experimental verification of this fact was carried out by extracting this fundamental parameter from measurements performed on on-chip and printed circuit board (PCB) lines using probe pad adapters and coaxial connectors. We demonstrate that the lumped circuit approach to represent the transitions lacks validity when the additional fluctuations due to the connectors become apparent, and we propose a new model including transmission line effects within the transition.

In this paper, a compact SISO (Single-Input Single-Output) antenna with a novel slotted-decahedral geometry is presented. The design was performed using a full-wave simulator (FWS). A decahedral patch with an eight-pointed star-shaped slot and two rectangular grooves is the main characteristic of the proposed novel radiator. The decagon shape, eight-pointed star-shaped slot, rectangular grooves, and separate section give rise to radiation. The SISO antenna operates from 23.1 to 29.94 GHz covering the proposed frequency bands for 5G wireless communication systems. The radiation pattern stability, moderate to high gain values (6.5 dBi, average), good radiation efficiency (higher than 89.4%), wide impedance bandwidth (6.84 GHz), compactness (13 × 13 × 0.787 mm3) and ease of manufacture are the principles advantages of this novel geometry. The experimental validation of the SISO antenna was performed, and good agreement was obtained with simulation results, and an equivalent circuit model was proposed. The proposed SISO antenna can be easily integrated into wireless sensors, drones, backhaul, and 5G devices which support IoT, working in the n257, n258 and n261 frequency bands.

A dual-band antenna based on two radiating rectangular slots working at 2.45 GHz and 5.8 GHz, respectively, with one upper Split Ring Resonator (SRR) to enhance the radiation pattern at 5.8 GHz is proposed in this work. Additionally, one Complementary Split Ring Resonator (CSRR) and three Split Rings (SR) are used to improve the input reflection coefficient. The dual-band antenna covers from 2.39 GHz to 2.52 GHz, and from 5.76 GHz to 5.95 GHz, covering the 2.45 GHz and 5.8 GHz ISM bands. The total size of the proposed antenna is $\mathbf{31 \mathrm{x}70\mathrm{x}70} \mathbf{mm}^{3}$ . The theoretical gain is better than 8 dBi and 6 dBi, and the radiation efficiency is close to 90% and 80%, in the first and second bands, respectively, from full-wave simulations. The performance of the proposed antenna is very good, which makes it suitable for IoT applications where the size is not a limitation, such as sensors, and LPWAN/WLA modules, health care devices, base stations, and control applications.

In this paper we present a novel metamaterial-based antenna simulated using HFSS. The unit cell parameters were extracted using periodic boundary conditions and wave-port excitation. The metamaterial is magnetically coupled to the CPW line, the induced current in the hexagonal ring gives rise to a field perpendicular to the incident one. The antenna can be modeled by an LC circuit. This design achieves a significant impedance bandwidth of 8.47 GHz (S11 = − 10 dB from 72.56 GHz to 81.03 GHz), and a minimum return loss of − 40.79 dB at 76.89 GHz, which clearly indicates good impedance matching to 50Ω. The proposed antenna offers gains from 4.53 to 5.25 dBi, with radiation efficiencies better than 74%. Compactness, simple design layout, a novel design, and good radiation characteristics for this antenna are the main contributions of this work. The antenna can be built on top of a 300 µm thick silicon wafer, for application on HR-SOI-CMOS technology. When compared to other antenna designs for the same frequency band, the proposed antenna achieves very good performance. This design is suitable for the reception stage of long-range automobile radar systems, due to its wide HPBW, as well as E-band applications, such as backhaul systems.

We present the design of metamaterial-based antennas for on-chip applications using the Jerusalem Cross metamaterial structure to improve the radiation and electrical properties of three types of antennas: Monopole, dipole, and Vivaldi. The enhancements were derived from full-wave simulations. The central frequency of these antennas is 78.5 GHz. The three topologies were designed on a high resistivity silicon wafer and a silicon dioxide insulation layer. The frequency range, and materials used for the design are suitable for on-chip applications such as vehicular radar systems as well as other E-band applications.

A full characterization and modeling methodology for the electrical transitions introduced by coaxial connectors serving as interfaces for accessing microstrip (MS) lines is presented and verified up to 40 GHz. The associated two-port network parameters are obtained from measurements performed on MS lines of different lengths. Subsequently, two circuit models for the transition are proposed and used to assess the performance of the connector transition as the lines vary in width.

In this article, we characterize and model two parasitic effects that become apparent in the performance of coplanar waveguide interconnects in CMOS. One is the transverse resistance introduced by a patterned ground shield in coplanar waveguide interconnects, which significantly contributes to the shunt losses. The other one is the parasitic coupling between the input and output ports through the ground shield. The latter effect is particularly accentuated in relatively short lines and complicates the determination of the propagation constant using line-line algorithms at several tens of gigahertz. We demonstrate that using the proposed methodology, excellent model-experiment correlation can be achieved in the modeling of these types of interconnects up to at least 60 GHz.

This article presents an S-parameter based equivalent circuit implementation for performing CAD-oriented RF simulations of through-silicon-vias (TSVs) in SPICE. In this regard, the accurate representation of TSVs in silicon dies exhibiting different conductivity and varying number of ground vias used as the return path is achieved. Moreover, it is demonstrated that the equivalent circuit can be cascaded to represent TSVs passing through several chips, provided that the transition bumps are included in the model. The proposal shows advantages over directly using tabular S-parameters, and substantially reduces the simulation time when compared with 3D electromagnetic solvers.

In this article, the design, construction and characterization of band-pass filters (BPF), based on the classic single-structure, square-loop, dual-mode resonator rings (SL-DMRR) is revisited. A specific requirement is proposed for using such a basic topology: the design and fabrication of L-band SL-DMRR filters to be part of the intermediate frequency (IF) section of a heterodyne K-band microwave transceiver. The heterodyne K-band transceiver has been designed and implemented to measure atmospheric attenuation at 22.4 GHz, in the vicinity of the strong absorption peak by water vapor molecules in the atmosphere. The BPFs are designed to operate at a center frequency of 1.1 GHz and a minimum bandwidth of 200 MHz. SL-DMRR filters in the L-band microwave range are more compact when compared to other microstrip structures such as parallel coupled lines, tapped input digital filters, hairpin filters, and so on. Filter realizations on FR4 and RT/Duroid 6010 substrates are optimized by resolving narrow coupling gap (0.07-0.1 mm), between the input/output stubs and the resonator ring. Narrow gaps (less than 0.1 mm) are an original achievement in our work to ensure insertion losses of 1 dB for FR4, 0.5 dB for RT/Duroid, return losses better than 20 dB and a minimum bandwidth of 200 MHz. These figures represent an appreciable advancement of the state-of-the-art for these classic structures for filters. The simulated and measured electrical responses of the filters show an excellent agreement. The IF filter has been incorporated to the K-band receiver and the system's performance is also reported in this article.

In this paper we present the design and fabrication of a two-antenna array to resonate at 5.8 GHz, a frequency that satisfies a host of applications, especially those associated with the ISM band, but including IoT applications. The design incorporates several techniques to improve figures of merit and reduce its size. The array presents a measured bandwidth of 617 MHz (from 5.503 to 6.120 GHz, or 10.63% about the central frequency) when built on a thin substrate, and of 455 MHz (from 5.517 to 5.972 GHz; 7.84%) when fabricated using a thicker one. The simulated gains were of 6.89 dBi and 7.63 dBi, whereas the measured ones were 6.7 dBi and 7.2 dBi, respectively. Size reduction is better than 30% and the simulated efficiencies are higher than 90%.

A model for integrated spiral inductors which incorporates the physically expected frequency-dependent effects modifying the device’s impedance is proposed. Moreover, it is demonstrated that the effect of resonances occurring outside the bandwidth of applicability for the device may considerably influence the performance around the peak of the Q-factor versus frequency curve. In this paper, we present the use of cascaded resonant circuits to represent the additional resonances occurring in the device to improve model accuracy up to 60 GHz.

In this paper, the design, construction and characterization of closed-loop, dual-mode resonator band-pass filters operating at a center frequency of 1.1 GHz, using a low-cost FR4 substrate, is described. Dual-mode resonator microwave filters are being studied as they are more compact when compared to other microstrip classical structures (parallel coupled microstrip lines, tapped input digital filters, hairpin filters, etc.), mostly when operating in low-frequencies such as the L and S microwave bands. An important contribution of this paper is showing that dual-mode resonator filters can be built on low-cost FR4 substrates. This is an original feature and becomes an attractive alternative for this kind of filters, which are mainly built on more specialized substrates such as Duroid or alumina. In this paper we present the design, simulation and fabrication of a 1.1 GHz IF filter, which is part of a heterodyne K-band receiver designed to measure atmospheric attenuation in the 22–23 GHz band. The proposed filter, centered at 1.1 GHz and with a 250 MHz bandwidth, is based on square loop dual-mode resonators. Filters in two architectures are proposed: single and compound resonators (two cascaded resonators). The simulated electrical responses are compared and reported. At this time, only single structures have been fabricated and measured, showing an excellent agreement between simulation and experimental results.