Reconfigurable intelligent surfaces (RISs) enhance the performance of wireless communication networks, particularly within millimeter wave (mm-Wave) bands. When a line-of-sight link is not strong enough or is fully blocked. The location of RIS has a significant impact on the RIS’s wireless channel and system performance. A wireless communication model has been proposed in a mm-Wave environment supported by RIS. The proposed model contains one transmitter and five users at the receiving end. Due to the small distance between users, there is interference between them and the received signal-to-interference-plus-noise ratio (SINR) decreases. Three RISs separated by different interspace distances were proposed to serve users at various distances from the transmitter to reduce inter-user interference. The simulation results showed that increasing the distance between the RIS site and the TX-User line served a larger number of users, and the three heights of the RIS provided a coverage range domain complementary to each other for different user sites. The improvement percentages in SINR for the second and third RIS are 48.46% and 77.38%, respectively. Enlarging the size of the RIS only increases the signal capacity and does not affect the coverage range domain of the single RIS.

A long-range, compact, wideband Ultra High Frequency (UHF) radio frequency identification (RFID) tag is proposed. The design features a triangular patch, designed to achieve wideband impedance matching. The tag exhibit −10 dB bandwidth from 753 to 917 MHz with a substrate thickness of 1.575 mm. The overall size of the tag is 121 × 30 × 1.575 mm3. The gain and bandwidth for varying substrate thickness is investigated. Further, two parasitic strips are designed alongside the patch to operate the tag more effectively at Federal Communications Commission (FCC) band in simultaneous with European Telecommunications Standards Institute (ETSI) band with increased read range. With parasitic strips, the tag exhibits −10 dB bandwidth from 766.5 to 896.5 MHz and 905 to 943.6 MHz which covers the bandwidth requirements in Europe, Asia, and North America. A prototype of the proposed tag is fabricated and experimentally tested with the RFID Higgs 4 IC. The tag provides a read range of over 14 m in 865–870 MHz and 13 m in 902–928 MHz when the tag is operated in free space and a read range of over 10.2 m in 865–870 MHz range and 10.3 m in 902–928 MHz range when mounted on a metallic surface of size of 200 × 200 m2 . The performance parameters of the designed tag are also compared with some commercially available designs.

This paper presents a flexible SiGe monolithic microwave integrated circuit (MMIC) chipset for 120 GHz ultra-wideband frequency-modulated continuous wave radar systems. The highly integrated chipset is implemented with multiple-input and multiple-output radar in mind which leads to transmit and receive MMICs with four integrated channels in each chip. The transmitter achieves an output power of 12.9 dBm with a total power consumption of only 403 mW. The receiver chip incorporates a sub-harmonic approach for suppression of leakage radiation at 120 GHz through a receive channel. Both chips integrate active multiplier chains that are driven by a third reference dual band voltage-controlled oscillator (VCO) MMIC that can deliver an output at center frequencies of 15 or 30 GHz. The reference VCO MMIC demonstrates relative tuning ranges of 32%.

In this paper, a large, compact array antenna that can be expanded in the 2-D plane is proposed for near-field radio frequency identification applications. By the introduction of the fractal structure and corner joint method, the array is easy to expand in the 2-D plane. An antenna element can be divided into a dozen or so loops, and traveling wave distribution makes sure that every loop is excited in a time period. So that a strong and uniform magnetic field could be generated in a large area. As a proof of concept, array antennas with $1 \times 8$, $2 \times 4$, and $3 \times 3$ elements are designed, fabricated, and measured. The measured bandwidth of the antennas covers the entire Chinese standard. Reading distances of the proposed large array antennas achieved up to 57 mm. Results show that the proposed antenna could realize flexibility and extendibility in a large area with stable and uniform magnetic field distribution.

This manuscript presents a millimeter-wave GaN high-power amplifier (HPA) intended for next generation inter-satellite links (ISLs). The proposed architecture achieves a fractional bandwidth wider than 18% in the V-band spectrum, to deliver a 10 Gbit/s throughput compatible with multi-thousand-km ISLs. Core of the HPA is the monolithic microwave integrated circuits (MMIC ) power amplifier which covers the whole 59–71 GHz band with high efficiency through innovative topologies and a cutting-edge gallium nitride on silicon carbide (GaN-on-SiC) process. The MMIC is then parallelized by means of a 1-to-8 splitter/combiner to obtain a V-band 10 W GaN HPA. Measurement results show a peak small-signal gain of 25.6 dB, 6.5% peak power-added efficiency, and a maximum P1dB of 40.3 dBm.

In this article, a qualitative work has been carried out based on airborne pulsed Doppler (PD) RF sensor consist of its operational requirements in terms of phase noise modeling and associated contributing factors. Precise and efficient theoretical modeling of phase noise requirement for airborne-PD radar or long-range RF sensor is presented. This work also emphasis on the limitation of conventional phase noise modeling practices used for PD RF sensor. An improved equation has been derived for accurate phase noise estimation considering the range correlation effect and inline flicker contribution on residual phase noise requirement. Random vibrations causes increase in phase noise level around low frequency offsets region in local oscillator. The proposed phase noise model is efficient enough to counter phase noise degradation at lower frequency offsets. The proposed model is also experimentally validated. Improved modeling offers benefit in reducing the stringent RF sensor phase noise specifications at close-in frequency offsets using range correlation effect and precise inclusion of inline flicker contribution. Present work can be used to mitigate random vibration effects at close-in phase noise offsets, which avoids complex stabilization practices and stringent oscillator design phase noise specification.

Antenna arrays are a main driver of next generation millimeter-wave communication and radar systems as shrinking antenna sizes leverage larger arrays to compensate for reduced link budget. However, conventional phase controlled arrays exhibit a frequency dependent scan angle that appears as loss to a fixed counterpart. Bandwidth limitations introduced by the so-called beam squint effect hinder larger array sizes and data rates thereby generating a demand for timed arrays as a solution. This paper gives a quantified overview of the beam squint phenomenon, different hardware architectures as well as evaluation parameters and common shortcomings of true-time delay (TTD) elements. A broad variety of TTD realizations from literature are compared by their operational principles and performance. Finally, the delay interpolation principle, its non-idealities, and their impact on a hierarchically time delay controlled D-band antenna array are described. Extended content on a previously published, continuously tunable TTD implementation at a center frequency of 144 GHz with a bandwidth of 26 GHz and a delay range of 1.75 ps that requires only 0.53 × 0.3 mm2 of core chip area is presented. Measurement results have been obtained from a demonstrator manufactured in 130 nm BiCMOS technology.

This work describes the design process of a single-pole double-throw (SPDT) microwave switch operating at Ka-band. It is tailored to a tunable reflective termination design that can be used in tunable power amplifier configurations. A high electron mobility transistor and a resonating network are employed in shunt configuration to enhance the performance in the output port’s active and inactive conditions. The small and large signal measurements showcase a 2 GHz bandwidth with an insertion loss and isolation better than −1.8 dB and −25 dB, respectively, and handling power levels of up to 3 W at 30.5 GHz. The load-pull measurements across the entire Smith chart offer comprehensive insights into the behavior of the SPDT when operating with complex and reactive loads, fulfilling the purpose of tunable reactive termination.

This paper presents a vertically folded gap waveguide filter for use as the filter element for each antenna in an array of slotted waveguide antennas, at W-band. Loaded gap-waveguide resonators are used to reduce the footprint of the filter, and the filter is vertically folded to reduce the length. New input and output transitions are proposed, as well as inter-resonator coupling structures that conform to the basic gap-waveguide structure. A 7th order filter with a bandwidth of 10 GHz and a center frequency of 101 GHz is designed to meet geometric constraints of a transmitter system. A sensitivity analysis was performed on the structure to determine the required manufacturing tolerances. The filter was manufactured and measured yielding 10 dB of return loss in the passband and a detuning of the passband by 1 GHz. The return loss at 88 GHz peaked due to deviations in manufactured gap height in the gap waveguide. Deviations from the simulated response were accounted for with a parameter extraction from the measured results.

A novel high-selectivity ultra-wideband (UWB) balanced bandpass filter (BPF) with harmonic suppression characteristics is proposed. The differential-mode UWB passband is constructed using quarter-wavelength asymmetrical parallel-coupled transmission lines, resulting in sharp filtering selectivity, while common-mode noises are suppressed by loading the T-type stubs. A simple design method of integrating bandstop filter branches into the BPF for third harmonic suppression without increasing the circuit size is described and confirmed. A planar high-selectivity balanced BPF prototype is manufactured and measured at 2.6 GHz with a measured 3-dB fractional bandwidth of 108% to validate the framework principle. More importantly, with third harmonic suppression characteristics, the measured out-of-band rejection is more than 20 dB, spanning 4.35 GHz until 12.4 GHz.

Worldwide adoption of 5G mobile devices has been one of the main driving engines behind semiconductor industry. Since the initial release in 2020, 5G-enabled devices have surpassed the market penetration of 3G/4G smartphones. 5G brings higher data capacity, low latency, and new applications. These are possible due to lower feature nodes such as FinFET 3 nm/5 nm but also due to improvements of the 5G radio frequency (RF)front-end circuitry. This paper presents 5G RF front-end architectures with novel circuits and measurement details which will be part of future 5G advanced and 6G mobile devices and are easier to be controlled using digital circuitry. The paper presents an envelope-controlled power amplifier (PA) principle, along with a novel simplified calibration architecture designed for 5G/5G+ operating under 6 GHz, as well as for frequency range 2 millimeter-wave PAs. An earlier version of this paper was presented at the 2023 53rd European Microwave Conference and was published in the Proceedings [Balteanu F, Thoomu K, Pingale A, Venimadhavan S, Sarkar S, Choi Y, Modi H, Drogi S, Lee J and Agarwal B (2023) Enabling RF circuit techniques for 5G and beyond In 53rd European Microwave Conference (EuMC), Berlin, Germany, 22–25].

In order to recover the magnetic energy that leaks from an induction cooktop, this study suggests a straightforward and cost-effective magnetic-field energy harvester (MFEH) circuit. With the aid of the intended circuitry, the acquired magnetic energy is transformed into DC electrical energy. We harvested the magnetic-field energy (MFE) from the induction cooktop at various heights and locations of the energy harvesting coil. With a load resister of 46.6 Ω and a capacitance of 1 mF, the developed MFEH circuit, when positioned 2 cm beneath the cooktop, can capture an average DC power of 1936 mW. Placing the energy-harvesting coil 7.5 cm beneath the induction cooktop lowers the power output to 142 mW. For a range of load resister values, the MFE gathered at various locations along the energy harvesting coils is examined. Batteries can be used to store the gathered energy for later use. Additionally, the suggested device is shown to be capable of wirelessly powering low-power Internet of things devices and charging mobile devices. The suggested device differs from the previously published magnetic harvesting circuits due to the induction cooktop’s superior performance and capacity to gather MFE.

This paper proposes a compact coplanar waveguide-fed slot antenna for ultra-wideband wearable applications, featuring six notch bands. The antenna utilizes a flexible liquid crystal polymer substrate with a thickness of 0.1 mm. The antenna achieves six band-notched characteristics by incorporating a split concentric ring etched on the radiating patch and L-shaped branches loaded on the ground plane. The proposed flexible antenna has dimensions of 30 × 30 mm2(0.65λ0*0.65λ0,λ0 is the free space wavelength at 6.5 GHz.). Measurement results show an impedance bandwidth ranging from 2.37 to 13.7 GHz and a fractional bandwidth of 134%. The notch bands cover 2.9–3.77 GHz for WiMAX applications, 4.14–4.9 GHz for the ARN band, 5.09–5.55 GHz for the WLAN downlink band, 5.86–6.46 GHz for the C-band uplink band, 6.66–7.39 GHz for the C-band/INSAT/super-extended band, and 7.93–8.43 GHz for ITU-8 GHz. The maximum gain in the operating band is 6.5 dBi. The performances of the flexible antenna are analyzed under bending conditions. The ANSYS HFSS electromagnetic simulator was used for the design and simulation of the proposed antenna. The flexible antenna is suitable for wearable applications.

This paper presents the bit efficiency of 28 GHz digital beamforming in over-the-air (OTA) measurements and simulations for distributed massive multiple-input–multiple-output (D-MIMO) and collocated massive multiple-input–multiple-output (C-MIMO) systems, as well as simulations for a 3.75 GHz small-cell scenario. Under the condition that users are randomly located in the line of sight coverage indoor area and spatially selected from each other by the normalized zero-forcing method, the OTA measured D-MIMO system exhibits an average of 4–7 dB better signal-to-noise ratio compared to C-MIMO when the number of simultaneously connected users “K” approaches the number of transceivers “M.” This means that the D-MIMO system provides higher bit efficiency than the C-MIMO system when K/M is large. Furthermore, the D-MIMO 3.75 GHz simulation predicts a relatively approximate 30% higher maximum efficiency than C-MIMO due to the shorter average distances between user equipment and access points in the D-MIMO system. To the best of the author’s knowledge, an earlier version of this paper has been presented at the 53rd European Microwave Conference as a first report on the 28 GHz OTA measured bit efficiency between C-MIMO and D-MIMO, highlighting D-MIMO’s advantage.

This paper outlines the design of a six-element multiple-input–multiple-output (MIMO) antenna with pattern diversity for industrial scientific medical (ISM)/5G-enabled wireless body area networks (WBANs). Within the MIMO configuration, each element has a quasi-yagi antenna configuration implemented on an ultrathin microwave laminate. The proposed quasi-yagi antenna has a small form factor of 25 × 25 mm, featuring a dipole-like radiator excited through a microstrip-line to tapered slot-line transition. The antenna’s radiators are patterned to ensure a dual-narrow impedance bandwidth. The conventional strip-line director in the planar yagi is replaced with a semicircular loop-like director, enhancing directional radiation patterns. This proposed flexible antenna offers versatile functionality by operating at both ISM standards of 2.45 GHz and the 5G wireless local area network standard at 3.5 GHz. The quasi-yagi elements are strategically distributed in a hexagonal formation to construct the six-element MIMO scheme with pattern diversity, resulting in a tangential radiation pattern suitable for on-body communication. Following fabrication, the prototype MIMO antenna’s simulation results are validated through real-time measurements. The proposed antenna exhibits an average gain exceeding 3.5 dBi across both operating bands. Furthermore, the proposed MIMO antenna exhibits promising performance metrics suitable for densely cluttered WBAN environments.

In recent years, the significance of terahertz (THz) and (sub-)THz communications has grown substantially due to its promising trade-off between higher capacity compared to microwave-based communication and better resilience against weather dependent influences (e.g., fog and rain). While electronic and optoelectronic techniques have been extensively explored, each offering distinct advantages and limitations, they have predominantly been demonstrated and discussed as individual experiments, making performance comparison challenging. This paper addresses this gap by systematically benchmarking electronic and optoelectronic signal generation approaches under comparable conditions. Our experiments incorporate various receiver types, revealing that best performance is achieved by combining optoelectronic signal generation techniques at the transmitter in combination with an all-electric intradyne receiver. This results in a remarkable line rate of 200 Gbit/s over a distance of 52 m. To our knowledge, this represents the highest line rate achieved for technically relevant transmission distances for indoor access or outdoor small cell networks.

This paper provides the details of a novel systematic design methodology for two-way in-phase filtering Gysel splitter/combiner networks with high selectivity, which finds application in high power amplifier modules. It simultaneously realizes a filtering function and a two-way splitter/combiner function. The proposed five-port filtering device, based on the Gysel topology, is transformed into a ring of coupled resonators. A rigorous coupling matrix describing the network is used to synthesize the integrated filtering and combining functions. This general network can be implemented in any of the available filter technologies. In this paper, a few design examples are provided, and a six-pole prototype utilizing compact combline coaxial resonators is demonstrated. The proposed design provides an integrated dual function module, reducing component counts and system complexity. A design was fabricated and tested demonstrating good experimental results.

A compact, wideband, and high-gain circularly polarized array antenna is proposed based on substrate integrated gap waveguide (SIGW) using sequential rotational phase (SRP). The array antenna consists of four $2\times2$ corner-cutting corner patches and an SIGW-SRP feeding network. The SIGW-SRP feeding network is achieved by utilizing the spatial vector addition property to compensate for phase, aiming to improve the bandwidth and gain. Unlike the traditional SRP feeding network, the proposed feeding scheme is simpler and easier to fabricate, and each port can achieve more stable phase and bandwidth. In addition, benefiting from the surface wave suppression and in-phase reflection property of SIGW, the proposed array antenna has a stable radiation pattern and low cross-polarization covering wideband frequencies. The measured results indicate that the −10-dB impedance bandwidth ranges from 12.2 to 17.3 GHz (34.6%), the 3-dB axial ratio bandwidth ranges from 13.5 to 16.7 GHz (21.2%), and the peak gain is 16 dBic.