Mm-wave Applications Research Articles

Injection Compression Molding of LDS-MID for Millimeter Wave Applications

LDS-MIDs (laser direct structured mechatronic integrated devices) are 3D (three-dimensional) circuit carriers that are used in many applications with a focus on antennas. However, thanks to the rising frequencies of HF (high-frequency) systems in 5G and radar applications up to the mmWave (millimeter wave) region, the requirements regarding the geometrical accuracy and minimal wall thicknesses for proper signal propagation in mmWave circuits became more strict. Additionally, interest in combining those with 3D microstructures like trenches or bumps for optimizing transmission lines and subsequent mounting processes is rising. The change from IM (injection molding) to ICM (injection compression molding) could offer a solution for improving the 3D geometries of LDS-MIDs. To enhance the scientific insight into this process variant, this paper reports on the manufacturing of LDS-MIDs for mmWave applications. Measurements of the warpage, homogeneity of local wall thicknesses, and replication accuracy of different trenches and bumps for mounting purposes are presented. Additionally, the effect of a change in the manufacturing process from IM to ICM regarding the dielectric properties of the used thermoplastics is reported as well as the influence of ICM on the properties of LDS metallization—in particular the metallization roughness and adhesion strength. This paper is then concluded by reporting on the HF performance of CPWs (coplanar waveguides) on LDS-MIDs in comparison to an HF-PCB.

Investigation on the new reliability issues of PCB in 5G millimeter wave application

PurposeThe purpose of this paper is to illustrate the new technical demands and reliability challenges to printed circuit board (PCB) designs, materials and processes when the transmission frequency increases from Sub-6 GHz in previous generations to millimeter (mm) wave in fifth-generation (5G) communication technology.Design/methodology/approachThe approach involves theoretical analysis and actual case study by various characterization techniques, such as a stereo microscope, metallographic microscope, scanning electron microscope, energy dispersive spectroscopy, focused ion beam, high-frequency structure simulator, stripline resonator and mechanical test.FindingsTo meet PCB signal integrity demands in mm-wave frequency bands, the improving proposals on copper profile, resin system, reinforcement fabric, filler, electromagnetic interference-reducing design, transmission line as well as via layout, surface treatment, drilling, desmear, laminating and electroplating were discussed. And the failure causes and effects of typical reliability issues, including complex permittivity fluctuation at different frequencies or environments, weakening of peel strength, conductive anodic filament, crack on microvias, the effect of solder joint void on signal transmission performance and soldering anomalies at ball grid array location on high-speed PCBs, were demonstrated.Originality/valueThe PCB reliability problem is the leading factor to cause failures of PCB assemblies concluded from statistical results on the failure cases sent to our laboratory. The PCB reliability level is very essential to guarantee the reliability of the entire equipment. In this paper, the summarized technical demands and reliability issues that are rarely reported in existing articles were discussed systematically with new perspectives, which will be very critical to identify potential reliability risks for PCB in 5G mm-wave applications and implement targeted improvements.

Role of AlGaN back-barrier in enhancing the robustness of ultra-thin AlN/GaN HEMT for mmWave applications

In this work, the robustness of three different AlN/GaN structures targeting high frequency applications with ultra-thin 3 nm AlN barrier and devices with different gate-to-drain spacing are evaluated. Devices were step-stress tested in off-state, semi-on-state, and on-state conditions. Different failure mechanisms were identified. Devices without AlGaN back-barrier show a fast increase of gate leakage current, leading to a significant degradation of electrical parameters such as the threshold voltage Vth, extrinsic transconductance GM, drain saturation current IDSsat and on-resistance Ron. This study reveals the role of the AlGaN back-barrier in the improvement of the device robustness presenting a good electrical parameters stability. The presence of an AlGaN back-barrier on low carbon- doped buffer leads to better gate leakage current stability, low trapping-related and self-heating mechanisms. The AlGaN back-barrier shows an extension of the operational Safe Operating Area for AlN/GaN technology.

Three-Dimensional Printed mm-Wave Circularly Polarized Filtering Antenna With Flexible Design and Spurious Suppression

In this communication, a 3-D printed circularly polarized (CP) filtering antenna with spurious suppression for 5G mm-wave applications is presented. First, a composite resonator, serving as both the last-stage resonator of a waveguide filter and an aperture antenna, is utilized to realize a filtering linearly polarized (LP) antenna. The 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -order electric cross-coupling topology is employed to generate two radiation nulls at both sides of the passband, enhancing the selectivity. Then, a polarizer is presented and placed in front of the LP antenna to obtain the CP radiation. The operating principles of the polarizer are analyzed in detail, which features flexible size and insensitivity to the original filtering response. To demonstrate the concept, three filtering CP antennas with different polarizer dimensions are designed, exhibiting similar responses. After that, to suppress spurious modes and extend the spurious-free region, the defected ground structures (DGSs) are introduced. Finally, all three CP antennas are fabricated using 3-D printing and tested. Measured results show that 10 dB return loss and 3 dB AR bandwidths for all antennas are about 7% and 9%, respectively.

Broadband Effective Permittivity Simulation and Measurement Techniques for 3-D-Printed Dielectric Crystals

Frequency-dependent dielectric properties of 3-D-printed structured dielectrics (dielectric crystals) with engineered effective permittivity for micro-and mmWave applications are studied. Different modeling and measurement techniques for broadband dielectric properties of such 3-D-printed crystals are reviewed, their tradeoffs discussed, and individual results compared. Numerically obtained results from the plane wave expansion method (PWEM) and Floquet port scattering are compared with traveling-wave measurements in both guided and free-space setups. Furthermore, the shortcomings of effective media theories (EMTs) and resonance measurement methods are addressed and contrasted against broadband methods. Individual simulation and measurement setups are reviewed with respect to dielectric crystals with simple cubic (SC) and face-centered cubic (FCC) symmetry, with different unit cell sizes and volumetric infill fractions. Extracted effective permittivity values from PWEM and Floquet port simulations show excellent agreement with traveling-wave measurements in both guided and free-space scenarios. Furthermore, the discussed broadband methods predict and measure frequency-dependent effects that are not covered by EMTs and resonance measurement setups, highlighting the necessity to adopt more sophisticated simulation tools for the design of graded-index devices. It is shown that the effective media bandwidth of dielectric crystals depends on the respective unit cell symmetry and that FCC symmetry obtains a significantly increased bandwidth compared with SC symmetry.

Interconnected square splits ring resonator based single negative metamaterial for 5G (N258, N257, N260 and N259) band sensor/EMI shielding/and antenna applications

This article proposed a new triple-band transmission block metamaterial (MTM) for 5G mm-wave applications. The peak transmission-blocking attributes are achieved at 27.09 GHz, 38.71 GHz, and 41.81 GHz frequency by interconnected square split ring resonators (ISSRR). A thin Rogers RT5880 substrate material of thickness 0.79 mm is employed to design the MTM structure, and the unit cell dimension is 5 × 5 mm2. The designed metamaterial shows a −10 dB transmission coefficient (S21) from 24.60 to 28.47 GHz, 36.50–39.65 GHz and 40.77–44 GHz frequency bands. The design evolution, metamaterial properties, surface current distribution, electric field, magnetic field, and equivalent circuit model are investigated to understand the transmission-blocking property of the MTM. The simulated results of the MTM are validated by measurement of the fabricated prototype, and both results agree well. The transmission-blocking attributes lead the proposed MTM as a potential candidate for different fields like EMI shielding, sensing, and antenna performance enhancement. The dielectric sensor performance of the MTM structure is investigated for different dielectric materials. Besides, MIMO antenna performances are also investigated, and gains of 1–3 dBi, isolations of 5–10 dB, and the radiation pattern deflection angle of 45˚ are enhanced by the proposed MTM. These significant features and applications of the proposed MTM make it a special candidate for 5G mm-wave applications.

Wide-Angle Scanning Microstrip Patch Antenna Array for mmWave Applications with High Gain

This paper presents a modified rectangular microstrip patch antenna (MRMPA) array conforming to the hemisphere for wide-angle beam scanning. Two different conformal antenna array designs are presented in this work. The first of these designs, a 13-element MRMPA array conformal to the surface of a circular arc, and the second one, a 9-element array conformal to the surface of a hemisphere, are designed and optimized. The geometrical approach of calculating the phase value is used to calculate the phase value of each antenna. The simulated results show that the 13-element conformal MRMPA array is achieving a beam scanning angle of ±84° with a gain of 13.89 dBi with low side lobe levels, and further, the gain of the array is enhanced by a dielectric superstrate that improved the gain by ∼2 dBi at all the scanning angles. Second, an MRMPA array conformal to a hemisphere with nine elements is designed with beam scanning ability from φ = 0°−360° and θ = ±30° with a gain of 15.69 dBi, and further, the gain is enhanced by ∼3 dBi with the dielectric superstrate. Full-wave simulations have proven both designs to be accurate and aligned with theoretical calculations.

Circularly Polarized Ka-Band High-Gain Antenna Using Printed Ridge Gap Waveguide and 3-D-Printing Technology

A low cost high gain circularly polarized antenna is proposed, the proposed antenna achieves a gain of 20-dBi, and an axial ratio bandwidth of 6.5%. The proposed antenna is extremely low in cost as it uses Printed Ridge Gap Waveguide (PRGW) technology. The use of PRGW technology suppresses the parasitic and back-lobe radiation from the feed, which maintains neat radiation characteristics for the radiating antenna. The structure is made of a Magneto-Electric (ME) dipole which illuminates a set of adjacent dielectric slabs. The diffracted fields from the edges of the dielectric slabs add up constructively with the ME dipole radiated fields in the boresight, and boost the gain of the ME dipole. Accordingly, the antenna structure relaxes the need for designing a feeding network by utilizing the diffracted fields from dielectric slabs edges. A 3D printed dielectric polarizer is used to further boost the gain and transform the polarization of the antenna to circular polarization. The antenna possesses a focused pencil-beam pattern that is well-suited for several mm-wave applications.

A Low-Loss Via-Free Ridge Air-Filled Substrate Integrated Waveguide on Printed Circuits Board for mmWave Application

A Low-Loss Via-Free Ridge Air-Filled Substrate Integrated Waveguide on Printed Circuits Board for mmWave Application

Temperature-Dependent Study of Large-Signal Reliability of p-FET-Based Power Amplifier for mmWave Applications

Temperature-Dependent Study of Large-Signal Reliability of p-FET-Based Power Amplifier for mmWave Applications

Characterization of Microstrip Line and SIW on ABF in Glass Interposers for mmWave Applications

Characterization of Microstrip Line and SIW on ABF in Glass Interposers for mmWave Applications

A 28/32/38 GHz Circularly Polarized DRA Micro-strip Antenna for 5G mm-Wave Applications

In modern communication system, mobile communication spectrum, below 3 GHz bands, faces more shortage and is not able to serve people with more efficient device connectivity and required data speed. Upon this background, 5G wireless communication – the 5th generation mobile technology standards are able to deliver high data rates, low latency communications, and massive device connectivity. For the efficient deployment of the 5G systems, and in order to support higher bandwidth, there is a dire need to design a compact and efficient antenna at mm wave frequencies (26/28 and 38). The resulting antenna, as the outcome, has been established to possess a compact size of 10 × 12 × 0.254 mm3 that covers three bands from the frequency spectra. The lower band resonant frequency is located at 26.74 GHz, the range between 25.44 GHz and 28.37 GHz, the middle band resonant frequency is located at 32 GHz, the range between of 31.08 GHz and 32.48 GHz, and the higher resonant frequency is located at 38.76 GHz, the range between 36.04 GHz and 40.34 GHz. In this article a modified novel structure of partial ground plane and DRA are used to get the better radiation enhancement and circular polarization. In this, the circularly polarized bands consist of the axial ratios &lt;3 dB which are 27.95 GHz to 28.37 GHz, 31.08 GHz to 31.67 GHz, and 36.04 GHz to 38.73 GHz. The gain achieved is greater than 6.5 dBi and the efficiency is greater than 96% over the three bands. Ultimately, it is proved to the right option for 5G mm wave applications.

Physical insights into the reliability of sunken source connected field plate GaN HEMTs for mm-wave applications

This article investigates the incorporation of field plates in AlGaN/GaN High Electron Mobility Transistors (HEMTs) which leading to enhancement in the device breakdown voltage and a reduction in the reverse leakage current. Using Atlas TCAD software breakdown behavior of gate-connected field plate (GFP), gate-source (dual) field plate, and discrete source-connected field plate (Sunken SC-FP) designs with field plate length variation is probed and physical insight is developed through electric field profile, and impact ionization contour plots. By employing a Sunken SC-FP with gate length of 0.4 μm in the gate-drain access region the device breakdown voltage is improved and has high JFOM (4.8 THz·V). Also, on-resistance (RON) degradation is minimum in the Sunken SCFP (20.12 %), compared with GFP (31.20 %) and dual FP (24.96 %) architectures, when the device is stressed in the off-state (VGS = −40 V) for 1 min. The RF performance of the Sunken SC-FP HEMT is studied using small signal parameters and the load pull measurements as a function of drain bias.

Miniaturization of a Fully Metallic Bandpass Frequency Selective Surface for Millimeter-Wave Band Applications

This article presents a miniaturized all-metallic bandpass frequency selective surface (FSS) for millimeter-wave (mmWave) applications. The designed FSS is realized as a slot-type element that can be easily incorporated into all-metallic device architectures. The miniaturization is achieved by a convoluted or meander slot structure, i.e., a miniaturization technique borrowed from conventional substrate-based FSS design. It is demonstrated that the proposed FSS element provides a stable and wide bandpass performance from 24.9 to 31.4 GHz for both the transverse electric (TE) and the transverse magnetic (TM) polarizations at the broadside direction ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = 0^{\circ }$</tex-math></inline-formula> ). Adequate performance is maintained at oblique incidence angles up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = \pm \,45^{\circ }$</tex-math></inline-formula> . A 25 × 25-elements FSS array prototype has been manufactured using the cost-effective chemical etching technique and experimentally characterized utilizing a free-space measurement setup. The results demonstrate a remarkably good correlation between simulations and measurements. Hence, the proposed miniaturized FSS represents an excellent potential to realize an all-metallic FSS with low insertion loss, low profile, and wideband performance at low fabrication costs for mmWave applications.

Voltage-margin limiting mechanisms of AlScN-based HEMTs

In this work, the off-state characteristics of AlScN/GaN high electron mobility transistors (HEMTs) grown by metalorganic chemical vapor deposition (MOCVD) were studied and directly compared to an AlGaN- and an AlN-HEMT grown in the same MOCVD. Pinch-off instability and leaky capacitive measurements were observed for AlScN-based HEMTs, which was correlated with a higher ideality factor and lower effective potential barrier height than the AlGaN and AlN-HEMTs. However, the reverse bias characteristics exhibited a sudden drain-current increase without a significant increase in gate-leakage current. The drain-leakage current is assumed to be related to a parasitic channel across the AlScN-barrier as a result of trap-assisted carrier transport with a Poole–Frenkel characteristic. The demonstrated pinch-off instability led to significant gain expansion in load-pull measurements and early soft-breakdown, which, in turn, limits the achievable voltage-margin. The results demonstrate a key issue to reveal the full potential of AlScN-based HEMTs for mm-wave applications.

Additive manufacturing in compact high-gain wideband antennas operating in mm-wave frequencies

A wideband dual-reflector 3D-printed antenna is proposed to operate in the mm-Wave band. The design is based on a Cassegrain reflector optics but including a dielectric piece for merging the feeding system and the support structure of the subreflector. The operational principle of this antenna is presented, as well as the design parameters. Then, a prototype to operate at Ka-band is manufactured combining a 3D-printed technique using PLA as printable material and a spray to coating the antenna, providing a low-cost affordable solution. The different pieces of the antenna are evaluated, and the antenna is also measured in a spherical compact range. An excellent agreement between simulations and measurements is obtained, resulting in a 48.2% of operational bandwidth. These results validate the use of coating procedures and the design technique at these demanding frequencies. Its operation shows a stable gain in the entire Ka-band (including 28 and 39 mathrm{GHz}), which makes the antenna as a suitable light, low-cost, and broadband solution for mm-Wave applications.

Double N Stubs for Impedance Matching Improvement of Pogo Pin Test Board at mmWave Applications

Double N Stubs for Impedance Matching Improvement of Pogo Pin Test Board at mmWave Applications

Dual-Band Dielectric Resonator Antenna with Filtering Features for Microwave and Mm-Wave Applications.

This paper presents a new design for a dual-band double-cylinder dielectric resonator antenna (CDRA) capable of efficient operation in microwave and mm-wave frequencies for 5G applications. The novelty of this design lies in the antenna's capability to suppress harmonics and higher-order modes, resulting in a significant improvement in antenna performance. Additionally, both resonators are made of dielectric materials with different relative permittivities. The design procedure involves the utilization of a larger cylinder-shaped dielectric resonator (D1), which is fed by a vertically mounted copper microstrip securely attached to its outer surface. An air gap is created at the bottom of (D1), and a smaller CDRA (D2) is inserted inside this gap, with its exit facilitated by a coupling aperture slot etched on the ground plane. Furthermore, a low-pass filter (LPF) is added to the feeding line of D1 to eliminate undesirable harmonics in the mm-wave band. The larger CDRA (D1) with a relative permittivity of 6 resonates at 2.4 GHz, achieving a realized gain of 6.7 dBi. On the other hand, the smaller CDRA (D2) with a relative permittivity of 12 resonates at a frequency of 28 GHz, reaching a realized gain of 15.2 dBi. The dimensions of each dielectric resonator can be independently manipulated to control the two frequency bands. The antenna exhibits excellent isolation between its ports, with scattering parameters (S12) and (S21) falling below -72/-46 dBi at the microwave and mm-wave frequencies, respectively, and not exceeding -35 dBi for the entire frequency band. The experimental results of the proposed antenna's prototype closely align with the simulated results, validating the design's effectiveness. Overall, this antenna design is well-suited for 5G applications, offering the advantages of dual-band operation, harmonic suppression, frequency band versatility, and high isolation between ports.

Impact of dielectric substrate on the performance of an 8 × 8 magneto-electric dipole phased array antenna for 5G mmWave applications

The impact of the substrate dielectric material on the performance of a wideband magneto-electric dipole (MED) phased array antenna is systematically studied in this article. Four commercially available dielectric substrates for mmWave applications, i.e., Rogers RO 5880, RO 3003, RO 4350B, and Panasonic Megtron-6, are considered in the design investigation of the proposed MED phased array antenna. First, the influence of the dielectric constant on the operating frequency of the unit cell MED antenna is explored in the broadside direction (θ = 0°). Second, the scanning impedance is assessed at various scanning angles for both E- and H-plane scanning. Finally, the radiation performance of the proposed design of a finite 8 × 8 MED phased array antenna is examined. This study gives a foundational understanding of the impact of dielectric characteristics on the performance of MED phased arrays. The analysis revealed that the MED phased array antenna based on substrates with a higher dielectric constant exhibited a smaller scanning angle than the substrate with a lower dielectric constant. The findings may serve as practical guidelines for selecting the dielectric substrates for the 5G mmWave phased array antenna in order to adapt their design to an application’s specifications.

Enabling Spherical Beam Coverage for Millimeter-Wave Stationary and Mobile Applications: A stackable patch antenna

The limited beam-scanning angles of planar phased arrays are one of the most critical challenges for millimeter-wave (mm-wave) wireless communication systems. This article proposes a new class of antenna topology, denoted as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">stackable patch antenna</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SPA</i> ), that achieves near-spherical beam-steering coverage for mm-wave applications. The proposed SPA consists of two identical rectangular patch antenna elements. By separately controlling the magnitude and phase of the excitation ports, the proposed antenna can radiate in multiple directions that are normal or parallel to the patch elements. In addition, the proposed structure has the advantage of enabling end-fire radiation when the structure is encompassed by the full metallic frame of a device. This is accomplished without any deformation or modification of the metal frame.