Millimeter-wave Band Research Articles

Enhanced 2-port MIMO antenna with composite two-step metasurface for 77 GHz Vehicle-to-Everything applications

The article presents a 2-port multiple-input multiple-output (MIMO) antenna array designed for millimeter-wave band operation, specifically optimized for Vehicle-to-Everything (V2X) applications. To enhance performance, a novel approach employing two types of metasurfaces on a single plate is utilized. The first metasurface, based on a loop structure, aims to improve the frequency bandwidth, while the second metasurface, utilizing a composite right/left-handed (CRLH) design, focuses on reducing mutual coupling. These two steps result in an improved frequency bandwidth exceeding 45% and a decreased structure width of about 50% compared to other designs. Notably, the compact nature of these metasurfaces, measuring approximately 32 × 3 mm2, is a significant feature that reduces manufacturing costs. The arrayed antenna, with 20 series elements, is suitable for medium-range radar in V2X applications, although our method is generally applicable to other ranges. Additionally, the radiation pattern exhibits a 40-degree beam rotation within the frequency bandwidth, making it well-suited for V2X applications. The results demonstrate impressive diversity performance, with a consistent maximum gain of 16 dB across the entire frequency bandwidth of approximately 68 GHz to 82 GHz, representing an 18.2% coverage.

Ultra-Compact 4-Port MIMO Antenna with Defected Ground Structure and SAR Analysis for 28/38 GHz 5G Mobile Devices

To tackle the challenge of keeping 5G mobile devices compact while supporting millimeter-wave bands, we've created an ultra-compact 4-port dual-band MIMO antenna with a defected ground structure (DGS). This design minimizes mutual coupling and covers a broad frequency range. Built on a Rogers TMM4 substrate with dimensions of 17.76×17.76 mm2, the antenna includes four planar patch antennas positioned perpendicularly at the corners. Each antenna operates at 28/38 GHz and features a rectangular patch with four rectangular slots and a full ground plane. The patches are separated by 0.5 λo, with the DGS further reducing mutual coupling. Both simulations and measurements indicate a significant reduction in mutual coupling (−39 to −60 dB), improving ECC, TARC, MEG, and DG. Time-domain and SAR analyses confirm the antenna's efficiency and its suitability for 5G devices.

Exquisite regulation of LZ-BaM/PPy composites for compatible absorption across centimeter-wave and millimeter-wave bands

The increasing complexity of the electromagnetic environment necessitates materials to exhibit superior microwave absorption performance for multitudinous bands. However, reaching satisfactory compatibility for absorption across centimeter-wave and millimeter-wave bands still remains a formidable challenge. In this work, a composite composed of Polypyrrole (PPy) and La3+-Zr4+ co-doped barium ferrite (LZ-BaM) is elaborately designed to address the issue facing us today. By exquisitely regulating the chemical composition, absorption peaks ascribed to different integral orders of interference can appear simultaneously in millimeter-wave and centimeter-wave bands. Ultimately, the as-prepared LZ-BaM/PPy composite reveals an efficient absorption (RL < −5 dB, absorptivity of 68.37 %), covering the centimeter-wave band of 8∼17 GHz and millimeter-wave band of 27∼40+ GHz concurrently under a matching thickness of 2.4 mm. This study thus offers valuable insights for the development of high-efficient absorbers across multiple frequency bands.

50 GHz Four-Port Coupling-Reduced Probe Card Utilizing Pogo Pins Housed in Custom Metallic Socket.

A design for a pogo-pin probe card featuring a metallic socket is proposed to eliminate signal leakage and coupling loss in a multi-port environment. The proposed metallic pogo-pin socket includes a metal wall structure between adjacent pogo pins, ensuring complete isolation. This metal wall offers an advantage in removing coupling issues between pogo pins that can occur with typical dielectric pogo-pin sockets. The designed probe card is fabricated as a prototype and verified for its performance. Measurement results using a test through line show that coupled power is minimized, providing a low-loss transmission performance of -2.14 dB to an RF chip at 50 GHz, all within a compact size. Although the dielectric spacer used to secure the pogo pins allows for some leakage, it can maintain a low coupling performance of under -15 dB in the millimeter-wave band. The prototype probe card can deliver an RF signal to a 5G circuit with a low loss of -0.7 dB at 28 GHz and -1.9 dB at 39 GHz frequency. The designed probe card is capable of transmitting multiple RF signals to the RF system without signal distortion in a multi-port environment.

Localization Performance Analysis and Algorithm Design of Reconfigurable Intelligent Surface-Assisted D2D Systems.

The research on high-precision and all-scenario localization using the millimeter-wave (mmWave) band is of great urgency. Due to the characteristics of mmWave, blockages make the localization task more complex. This paper proposes a cooperative localization system among user equipment (UEs) assisted by reconfigurable intelligent surfaces (RISs), which considers device-to-device (D2D) communication. RISs are used as anchor points, and position estimation is achieved through signal exchanges between UEs. Firstly, we establish a localization model based on this system and derive the UEs' positioning error bound (PEB) as a performance metric. Then, a UE-RIS joint beamforming design is proposed to optimize channel state information (CSI) with the objective of achieving the minimum PEB. Finally, simulation analysis demonstrates the advantages of the proposed scheme over RIS-assisted base station positioning, achieving centimeter-level accuracy with a 10 dBm lower transmission power.

Vegetation Loss Measurements for Single Alley Trees in Millimeter-Wave Bands.

As fixed wireless access (FWA) is still envisioned as a reasonable way to achieve communications links, foliage attenuation becomes an important wireless channel impairment in the millimeter-wave bandwidth. Foliage is modeled in the radiative transfer equation as a medium of random scatterers. However, other phenomena in the wireless channel may also occur. In this work, vegetation attenuation measurements are presented for a single tree alley for 26-32 GHz. The results show that vegetation loss increases significantly after the second tree in the alley. Measurement-based foliage losses are compared with model-based, and new tuning parameters are proposed for models.

A High-Gain Metallic-via-Loaded Antipodal Vivaldi Antenna for Millimeter-Wave Application

This paper presents a miniaturized-structure high-gain antipodal Vivaldi antenna (AVA) operating in the millimeter-wave (mm-wave) band. A gradient-length microstrip-patch-based director is utilized on the flares of the AVA to enhance gain. Additionally, an array of metallic vias is incorporated along the lateral and horizontal edges of the antenna for further gain enhancement and bandwidth extension. Based on the proposed structure, the AVA can achieve a peak gain of 11.9 dBi over a relative bandwidth of 71.24% within 16.5–36.6 GHz as measured, while the electrical dimension is only 1.54 × 2.69 × 0.07 λc3. The measured results show good agreement with the simulated ones. Owning the characteristics of being high-gain and ultra-wideband, and having a compact size, the proposed AVA can be a competitive candidate for future millimeter-wave communication.

Characteristics of a CaO–B2O3–SiO2–Al2O3–ZnO-based sandwich substrate and its dielectric properties in the 5G millimeter-wave band

In this study, a 34.5CaO–23B2O3–33.5SiO2–6Al2O3–3ZnO (CBSAZ) glass-ceramic substrate was prepared using a sol–gel method. A porous CaO–B2O3–SiO2–Al2O3–ZnO layer (CBSAZ0.5C) with a porosity of 72.6 % and thickness of 365 μm was inserted between two ∼120 μm thick dense CBSAZ layers to form a tri-layer substrate (CBSAZ/CBSAZ0.5C/CBSAZ). The dielectric constants (εr) and dielectric losses (tanδ) of the dense CBSAZ substrate at 20 and 60 GHz were 6.90 and 0.029, respectively, and 6.96 and 0.017, respectively. These values were almost independent of frequency. In contrast, the εr and tanδ values of the CBSAZ/CBSAZ0.5C/CBSAZ sandwich substrate at 20 and 60 GHz were 3.59 and 0.022, respectively, and 3.11 and 0.020, respectively. Thus, the εr value of the CBSAZ/CBSAZ0.5C/CBSAZ sandwich substrate was significantly lower than that of the CBSAZ substrate, whereas the tanδ and κ values of the CBSAZ/CBSAZ0.5C/CBSAZ and CBSAZ substrates were similar.

Highly integrable planar-structured printed circularly polarized antenna for emerging wideband internet of things applications in the millimeter-wave band

This paper proposes a numerically and experimentally validated printed wideband antenna with a planar geometry for Internet of Things (IoT) applications. This design tackles the challenges associated with deploying IoT sensors in remote areas or across extensive geographical regions. The proposed design exploits a coplanar-waveguide-fed modified microstrip line monopole for excitation of circularly polarized waves radiating in the broadside direction. The primary design is based on perturbations of the microstrip line protracted from a grounded coplanar waveguide. The capacitively coupled short rectangular stubs are periodically inserted alternately and excited asymmetrically on each side of the microstrip line parallel to the direction of the electric field vector. The sequential phase excitation of the periodic stubs generates a rectangular-cascaded electric field, which suppresses the stop band at the open end. As a result, the antenna radiates in the broadside direction. The impedance bandwidth of the antenna exceeds 8 GHz in the 28 GHz mm-wave band, i.e., it ranged from 25 to 33.5 GHz. Additionally, an axial ratio below 3 dB is achieved within the operating band from 26 to 33.5 GHz with the alterations of the surface current using straightforward topological adjustments of the physical parameters. The average in-band realized gain of the antenna is 10 dBic when measured in the broadside direction. These results indicate that the proposed design has the potential to improve the connectivity between IoT devices and the constantly varying orientation of satellites by mitigating the polarization mismatch.

Series-Fed Integrated Lens Antenna for High Gain in Millimeter-Wave Band

Series-Fed Integrated Lens Antenna for High Gain in Millimeter-Wave Band

OAM-MIMO Multiplexing Transmission System for High-Capacity Wireless Communications on Millimeter-Wave Band

OAM-MIMO Multiplexing Transmission System for High-Capacity Wireless Communications on Millimeter-Wave Band

Sub-6 GHz beamforming with low-cost software-defined radio: Design, testing, and performance evaluation

The rapid evolution of mobile communication systems has led to the introduction of novel technologies and techniques that address existing challenges, such as interference caused by multiple users and transmission through the millimetre-wave band. In this paper, we present a novel approach that utilises a low-cost software defined radio (SDR) unit to enable transmitting and receiving beamforming in the sub-6 GHz band. We provide a detailed account of the underlying concepts and background of beamforming and SDR, outline the design of multiple components, and report on the comprehensive testing and verification of a real-life prototype using over-the-air (OTA) methods. Our results demonstrate that the proposed approach achieves outstanding performance, with measurements of bit error rate (BER) that outperform existing solutions. In summary, this work contributes to the ongoing efforts to enhance mobile communication systems by providing an innovative, high-performance solution that is cost-effective and reliable using SDR technology in the sub-6 GHz band.

Tolerance Considerations for MHMIC Manufacturing Process at Millimeter-Wave Band.

This paper investigates the manufacturing uncertainties at a 60 GHz millimeter-wave band for the monolithic hybrid microwave integrated circuits (MHMIC) fabrication process. It specifically deals with the implementation tolerances of thin-film gold microstrip transmission lines, titanium oxide thin-layer resistors, microstrip quarter-wavelength radial stubs, and active device implementation using the gold-bonding ribbons. The impacts of these manufacturing tolerances are assessed and experimentally quantified through prototyped MHMIC circuits. This allows us, on one hand, to identify the acceptable amount of dimensional variation enabling reasonable performances. On the other hand, it aims to establish a relationship between the manufacturing tolerances and the circuit parameters to provide more flexibility for the tolerance compensation and accuracy enhancement of the MHMIC fabrication processes.

Low mutual coupling miniaturized dual-band quad-port MIMO antenna array using decoupling structure for 5G smartphones

Maintaining the compactness of 5G smartphones while accommodating millimeter-wave (mm-wave) bands presents a significant challenge due to the substantial difference in frequency. To tackle this issue, we introduce a miniaturized quad-port dual-band multiple-input, multiple-output (MIMO) antenna with low mutual coupling (MC) and a considerable frequency difference. This quad-port MIMO antenna, built on a Rogers TMM4 substrate, measures 17.76 × 17.76 mm2 and boasts a dielectric constant of 4.5. It incorporates four planar patch antennas, positioned at the corners in perpendicular orientations. For dual-band operation at 28/38 GHz, each antenna element features a rectangular patch with four rectangular slots, complemented by a full ground plane. The spacing between these elements is 0.5 λo, and we've included a decoupling structure (DS) to minimize mutual coupling (MC) among the MIMO antenna elements with minimal complexity and cost. Simulation and measurement results reveal a significant reduction in mutual coupling between the array elements, ranging from − 25 to − 60 dB. As a result, we’ve developed the envelope correlation coefficient (ECC) and made advancements in the total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG). The measured gains for this design are approximately 8.9 dBi at both 28 GHz and 38 GHz, with a radiation efficiency of nearly 93%. Furthermore, specific absorption rate (SAR) analysis confirms the MIMO antenna's suitability for smartphone handsets operating within the target frequency band.

Characteristic mode based self isolated MIMO antenna design for millimeter wave 5G communications

The paper introduces a self-isolated quad-port multi input multi output antenna system designed for fifth-generation wireless communication. The reported antenna structure possesses an overall dimension of 12.4 × 12.4 × 0.508 mm3 and is derived from a single-element antenna, featuring a circular patch accompanied by a sectoral slot. To achieve the desired frequency band, an additional circular patch is purposefully placed over the main radiator. The development of each design stage in the antenna structure is investigated using the theory of characteristic mode. This configured multi-element antenna structure achieves a broad operational bandwidth spanning 4.5 GHz, encompassing frequencies from 26.1 GHz to 30.6 GHz, rendering the antenna well-suited for deployment in the millimeter-wave frequency bands of n257, n258, and n261 respectively. A total gain of 6.27 dBi is achieved with port isolation of −24 dB. Furthermore, the antenna undergoes validation for diversity metrics, including envelope correlation coefficient, diversity gain, channel capacity loss, total active reflection coefficient, and mean effective gain. The antenna is fabricated and experimentally validated with the simulated counterpart. Later, a comparative analysis has been conducted which revealed that the proposed antenna demonstrates > 80 % increase in compactness compared to existing antenna designs documented in the literature.

Silicon-based waveguide technology for millimeter-wave antennas

This paper describes a method for the preparation of complex structured waveguides that can be used for millimeter-wave antennas based on a bulk silicon MEMS process. In this paper, a millimeter-wave band array of ridge waveguide slit antennas with multilayer step-matched feeds is realized by this method. A bulk silicon MEMS process is used to realize the complex structure and the high precision and flatness requirements on the millimeter scale, which cannot be achieved by machining. And the step height difference of more than 100um is realized by combining multiple lithography and silicon oxide mask. The step difference is larger than that achievable by dry etching using the etching selection ratio of silicon oxide and silicon. The waveguide fabricated by this method can work well in the millimeter wave band and is used for antenna feeding, power distribution, etc. It is characterized by compact structure, high precision, and high performance.

A compact and narrow-band bandpass filter based on substrate integrated waveguide and spoof surface plasmon polaritons for millimeter-wave applications

This paper presents bandpass filter (BPF) comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), achieving miniaturized size, low insertion loss in the millimeter-wave band. SIW with single-slotted SSPP structure is employing to obtain the transmission zero (TZ) at the low-frequency part, and by introducing the SIW with rhombic periodic walls to enhance the low-frequency rejection. The target passband and TZ of the high-frequency part are realized by increasing the number of etching slots. Furthermore, we innovatively incorporate nonradiative (NR) slots etched below the SSPP structure to gain high out-of-band rejection level. SIW with rhombic periodic walls and slotted SSPP structure as one unit cell is analyzed and demonstrated. Ultimately, the two SIW unit cells are cascaded together to get better out-of-band rejection characteristics and serve as our final design. To validate the proposed design, the BPF prototype is fabricated and measured, showing good electrical performance in terms of high selectivity, low loss, and compact size.

Genetic Algorithm for Mode Selection in Device-to-Device (D2D) Communication for 5G Cellular Networks

The widespread use of smart devices and mobile applications is leading to a massive growth of wireless data traffic. With the rapidly growing of the customers’ data traffic demand, improving the system capacity and increasing the user throughput have become essential concerns for the future fifth-generation (5G) wireless communication network. In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular spectrum and all communications take place through the base stations (BS) and core network. Device-to-Device (D2D) communication refers to a technology that enables devices to communicate directly with each other, without sending data to the base station and the core network. This technology has the potential to improve system performance, enhance the user experience, increase spectral efficiency, reduce the terminal transmitting power, reduce the burden of the cellular network, and reduce end to end latency. In D2D communication user equipment’s (UEs) are enabled to select among different modes of communication which are defined based on the frequency resource sharing. Dedicated mode where D2D devices directly transmit by using dedicated resources. Reuse mode where D2D devices reuse some resources of the cellular network. Outband mode where D2D communication uses unlicensed spectrum (e.g. the free 2.4 GHz Industrial Scientific and Medical (ISM) band or the 38 GHz millimetre wave band) where cellular communication does not take place. Cellular mode where the D2D communication is relayed via gNode B (gNB) and it is treated as cellular users. In this work, the target was to reach the optimal mode selection policy and genetic algorithm method was used with the objective of maximizing the total fitness function. Optimal mode selection policy was presented and analysed amongst cellular, dedicated, reused and outband mode. In the present study of mode selection issues in D2D enabled networks, genetic algorithm was proposed for the case when the cellular user equipment (UE) moves in the network. Quality of service (QoS) parameters, mobility parameters and Analytic Hierarchy Process (AHP) method were used to define the mode selection algorithm. To evaluate the performance of the proposed genetic algorithm, a study of the convergence of the algorithm and the signal-to-interference plus noise ratio (SINR) was done.

Broadband parasitic modeling of diodes in the millimeter-wave band

This paper presents the extraction of an equivalent circuit model for PIN diodes and varactors in the millimeter waves. This circuit model is handy for new communication applications involving, for example, electronic beam reconfigurability, where diodes are commonly used. For parameter extraction, the proposed model includes the effects of the device, the pads, and the gap underneath the device. From the measurement at various bias points (varactor) or states (PIN diode), it is possible to extract an equivalent circuit to properly model the behavior of these devices when using them to design reconfigurable elements. The results are validated experimentally, obtaining an excellent agreement between the measurements and the equivalent circuit models in a large frequency band up to 67 GHz.

Broadband InBiSe3 alloy photoelectric detector from visible to terahertz

With the demand for communication, imaging, spectroscopy, and other applications, broadband detection has always been a particularly popular direction. However, the current photodetectors have the problems of relatively narrow response bands, a low sensitivity, a slow response speed, and complex manufacturing processes. In this article, the alloy material InBiSe3 is proposed to manufacture a wideband photodetector from visible to terahertz at room temperature. The noise equivalent power (NEP) of the detector is 1.37 × 10−10 W Hz−1/2 at 635 nm, 1.2 × 10−10 W Hz−1/2 at 808 nm, and 1.56 × 10−10 W Hz−1/2 at 980 nm. The device also exhibits a good response in the terahertz and millimeter-wave bands, with a NEP of 8.33 × 10−15 W Hz−1/2 at 0.023 THz, 7.03 × 10−14 W Hz−1/2 at 0.14 THz, 6.14 × 10−15 W Hz−1/2 at 0.171 THz, 1.91 × 10−14 W Hz−1/2 at 0.35 THz, and 4.04 × 10−14 W Hz−1/2 at 0.5 THz based on the electromagnetic induced potential wells effect. The response time is as fast as 10 µs. Our results demonstrate the promise of the InBiSe3 alloy for photoelectric applications and provide a method for the high performance of broadband photodetectors.