Ground Vias Research Articles

Deep Reinforcement Learning-Based Ground-Via Placement Optimization for EMI Mitigation

Placing ground vias plays a crucial role in mitigating electromagnetic radiation from printed circuit board (PCB) edges. Stitching dense ground vias along PCB edges is not always feasible due to limited layout areas. Finding a ground-via placement strategy to achieve the best electromagnetic interference (EMI) mitigation using a specified number of ground vias is desired in the industry. However, this process is usually tedious and labor-intensive because of the enormous search space. This article proposes an optimization algorithm based on deep reinforcement learning to adaptively seek the optimal ground-via placement strategy in complex packages. First, an evaluation module based on convolutional neural networks (CNNs) is trained to predict the EMI mitigation for any possible ground-via placement. Then, relying on the well-trained CNN, an optimization module based on dueling double deep Q network is developed to find the best ground-via placement strategy through exploration and training without prior electromagnetic knowledge. The final optimization strategy obtained by our proposed algorithm has more effective EMI mitigation than the commonly used “edge-wrapping” solution in industrial products. Our proposed algorithm also provides guidelines and insights about the design rule and the behind physics.

Optimization of Ground-via Patterns for via Transitions by Minimizing Loop Inductance

Via is a commonly-used interconnect structure for vertically connecting signal traces or power or ground planes in packages and boards. As the speed of data transfer increases, the electrical properties of via structure becomes more and more important for getting better signal quality. Modeling a via structure typically involves complex computation. In this article, authors use partial element method to model the structure as coupled inductor array. It firstly proves that the loop inductance of a single-ended via transition is minimized through perturbation analysis. On the other hand, the differential-mode loop inductance of a via pair surrounded by 2, 4, 6, and 8 ground vias respectively is also derived. The full-wave simulation results all show good agreement with the ones predicted by formulae. Thus, with these formula, the optimization of ground via placement could be quickly found.

Design of a Dual-Polarization Dipole Antenna for a Cylindrical Phased Array in Ku-Band

This paper proposes a dual-polarization dipole antenna for a cylindrical phased array working in Ku-band. The dipole antenna is double-layer structured and is composed of two orthogonal butterfly shaped dipole radiators, two ground co-planar waveguide (GCPW) feeding structures and vias. Each dipole is in the shape of a butterfly. The dipole patch is grooved triangularly and one side of it is bent into an N shape, which effectively expands the working frequency band of the antenna. The double-layer structure improves the isolation between the antenna ports. The antenna works between 15 GHz to 16.2 GHz and the isolation between the antenna’s two feeding ports in this band is better than 20 dB. The proposed dipole antenna is applied in a 32-element cylinder array. The simulation and measured results show that the array can scan between −60° to +60° in the azimuth plane with a gain fluctuation less than 2.5 dB. Therefore, the proposed design is an attractive candidate for conformal devices at Ku-band frequencies, and it also has a great potential for application in larger antenna arrays.

Novel Highly Flexible PCB Design Based on a Via-Less Meander Ground Structure to Transmit mm-Wave RF Signals in 5G Foldable Mobile Products

Recently, new form factors, such as foldable, have increased demand for mobile products.Moreover, mobile phones should support the RF signal frequency up to the mm-wave frequencydue to the expansion of 5G mobile products. Therefore, 5G foldable products require componentsthat facilitate both mm-wave RF transmission and ultra-high flexibility for interconnecting throughthe hinge structure of foldable products. To improve flexibility, a flexible PCB must be thin with noground vias in its bending section; in contrast, the low-loss flexible PCB for mm-wave transmissionmust be thick and have many ground vias, so there is a trade-off relationship between flexibilityand RF characteristics. This paper proposes a new flexible PCB structure that does not experienceproblems regarding signal transmission to the mm-wave band, even when folded 200,000 times.To overcome the physical limits of the trade-off relationship, an interlayer air-gap was formed; astructure with a via-less and meander ground shape is proposed. The simulated loss of the proposedstructure was 0.0254 dB/mm @ 10 GHz, and the isolation between signals ranged from 21.98 dBto 10 GHz. The simulated results of insertion loss and isolation were experimentally verified. Theproposed structure is currently being applied to the RF flexible PCB that interconnects through thehinge of a foldable phone, and is currently being mass-produced.

Printed Dual-Beam Fixed-Beam Leaky-Wave Antenna Based on Leaky Grounded Coplanar Waveguide

A novel dual-beam fixed-beam leaky-wave antenna (LWA) is proposed in this article. This antenna has a very simple structure, which is basically a grounded coplanar waveguide (GCPW) printed on a specially shaped printed circuit board (PCB). Its working principle is that, for a GCPW with no ground vias (leaky GCPW), there will be a parallel plate waveguide (PPW) mode between its two ground layers, which couples with its GCPW mode. Because the GCPW mode has a phase velocity higher than that of the PPW mode, leaky-wave radiation will be generated from the GCPW to the PPW. This radiation is then radiated into the free space through a metal flare. Since the GCPW is nearly non-dispersive, the beam direction of this radiation is inherently not frequency scanning. Besides its simplicity, the proposed antenna has a pretty good performance. Measured results show a 3 dB realized gain bandwidth and −10 dB impedance bandwidth of larger than 26–40 GHz, a peak gain of 17.5 dBi, and a negligible beam scanning range of only 2.5° (±1.25°) across 26–40 GHz.

A novel low‐profile patch antenna with integrated RF internal calibration line

This article presents a novel structure of integrated radio frequency（RF） internal calibration line for patch antenna without increasing the antenna profile. The RF internal calibration line is realized by introducing a microstrip line in the middle of the nonradiation side of the two patch antenna units. Metalized grounding strips (MGS) are composed of metal strips on the upper surface of printed circuit board, metalized ground vias, and the ground layer. The MGS with gaps is set between the calibration line and the antenna units to adjust the mutual coupling. A 16 × 32 antenna array is fabricated and measured for verification. The measured results are in good agreement with the theoretical simulation. It shows that the mutual coupling between the coupling port of the calibration line and each port of the antenna unit is between −32.5 and −27 dB in the X and Ku frequency band (12–13.2 GHz, 9.5% relative bandwidth), and the antenna pattern is not distorted by the integrated calibration lines.

Assessment of through‐silicon‐vias with different configurations of ground vias and accounting for substrate losses

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.

Compact Planar Multipole Antenna for Scalable Wide Beamwidth and Bandwidth Characteristics

This article proposes a concept of compact planar multipole antenna configured by multiple magnetic and electric dipoles as a single radiation element with a single signal excitation port. The proposed structure uses diverse orientations in magnetic field and electric coupling through segmented radiation conductors and ground vias. The uniqueness of multipole antenna can be emphasized by its compactness, wide beamwidth in both the E- and H-planes with a finite ground plane size, and wide impedance bandwidth characteristics. To verify the concept of multipole structure, four different types of antennas are proposed and analyzed. With a radiation element size of $0.33\lambda _{\mathrm {o}}\,\, \times 0.33\lambda _{\mathrm {o}}$ ( $\lambda _{\mathrm {o}}$ for free-space wavelength) and a finite ground size of $1.1\lambda _{\mathrm {o}}\,\, \times 1.1\lambda _{\mathrm {o}}$ at 5.9 GHz, the half-power beamwidths (HPBWs) of 175° and 133° in both the E- and H-planes were measured, respectively. A wider bandwidth characteristic compared to previously reported wide beamwidth planar antennas was also achieved by one of the proposed structures. The measured 10 dB impedance bandwidth was about 13% with HPBWs of 111° and 160° in both the E- and H-planes, respectively. Also, the measured peak gains were better than 5.3 dBi for all structures with an excellent gain flatness at the operation band.

Decoupling capacitor power ground via layout analysis for multi-layered PCB PDNs

A modeling methodology to calculate the decoupling capacitor interconnect inductance in a multi-layer PCB is proposed herein. The methodology is based on the resonant cavity model of parallel planes. The self-inductance and mutual inductance are extracted to understand the via configuration influence on the effectiveness of decoupling capacitors. A special layout of decoupling capacitor is proposed to increase the effectiveness of the decoupling capacitors by taking maximum advantage of the mutual inductance between interconnect vias with two decoupling capacitors placed in a pair, and two pairs of power and ground vias placed in alternating directions as close as possible. The number of decoupling capacitors needed can be reduced dramatically. Three PCB PDN designs are used to present the effectiveness of doublet layout in different design scenarios. Similar analysis is extended to 3-terminal decoupling capacitor layout design. The decoupling capacitor interconnect inductance of the five via layouts for 3-terminal capacitors is analyzed. The number of decoupling capacitors needed for a commercial product using the doublet layout and 3-terminal capacitor layout is compared to the design with an alternating decoupling capacitor layout to reflect the impact of the decap layout design on the PCB PDN performance.

Efficient Simulation of Substrate-Integrated Waveguide Antennas Using a Hybrid Boundary Element Method

This paper presents a hybrid boundary element method for the efficient simulation of substrate-integrated waveguide (SIW) horn antennas. It is applicable with good accuracy to relatively thin structures with conventional circular ground vias. In the multiscale simulations, a 2-D contour integral method is used for the modeling of the fields inside the structure with numerous vias and a method of moments is used for the radiated fields outside. The contour integral method is extended in this paper by a new waveguide port of finite size based on the unit cell analysis of an SIW segment. Several SIW horn antennas are studied to validate the proposed method in terms of the input impedance, the field distribution on the aperture, and the radiation diagram. The proposed method shows good to reasonable accuracy and has a numerical efficiency which is about 2–3 orders higher than FEM-based full-wave simulations. It is therefore well suited for fast optimizations.

A 25.78-Gbit/s × 4-ch Active Optical Cable with Ultra-Compact Form Factor for High-Density Optical Interconnects

A 25.78-Gbit/s × 4-ch active optical cable (AOC) with an ultra-compact form factor is proposed. The size of the proposed AOC is 5.2 cm3, which is 55% smaller than the standard form factor of Quad Small Form-factor Pluggable (QSFP28), and 45% smaller than that of Micro Quad Small Form-factor Pluggable (μQSFP). As a result of utilizing a high-efficiency heat-dissipation structure and optimizing signal transmission lines and ground vias, the proposed AOC achieves high-heat dissipation and low-crosstalk characteristics. Furthermore, the proposed AOC demonstrated 25.78-Gbit/s error-free optical transmission over a 100-m Optical Multimode 3 (OM3) multimode fiber under all-channels (4-ch) operation and case temperature (Tc) of 70 °C.

A Miniature Ultrawideband Electric Field Probe Based on Coax-Thru-Hole via Array for Near-Field Measurement

In this paper, a miniature electric field probe with an ultrawideband of 9 kHz–20 GHz is proposed, fabricated, and tested. The electric field probe is fabricated on a four-layer printed circuit board using high-performance and low-loss Rogers material ( $\varepsilon _{\mathrm{r}}= 3.48$ and tan $\delta = 0.0037$ ). Coax-thru-hole via array is used to control the signal via impedance to achieve impedance $50~\Omega $ match over the whole working band, reducing the harmful influence on the probe’s characteristic. The ground vias, called via fence, are utilized to suppress the resonance caused by the parallel-plate mode of conductor-backed coplanar waveguide (CB-CPW), expanding the working frequency band. Experimental result shows $\vert S_{21}\vert $ rather smooth in operation band, demonstrating the working frequency band is up to 9 kHz–20 GHz. The electric field probe has a 2–3 mm spatial resolution, which has a good ability to locate the interference source.

Microwave Filter Design Optimized for Ceramic Multilayer Technique

Abstract Low Temperature Co-fired Ceramic (LTCC) is a proven packaging technology for microwave and millimetre-wave applications. Advanced low-loss material systems and improved manufacturing technology facilitate economic and highly reliable packaging solutions for automotive, telecom, medical and security applications. One of the virtues of LTCC is the option to integrate all kinds of components into the multilayer. Embedded passives include resistors, capacitors and inductors. Moving matching networks and filters into inner layers is further increasing density of integration. Microwave filters in LTCC can be used as an integral part of a larger package but also as single components mounted as drop-in or SMT. Ceramic multilayer technology allows for new filter concepts with three-dimensional routing and integration. Tolerances in material properties and manufacturing are challenges to be met with the design and production of microwave filters. Tape thickness, permittivity, shrinkage, registration of conductor pattern to via position, conductor width and thickness are some of the parameters that influence filter performance and reproducibility. This paper shall compare two different concepts for a 20 GHz band pass filter regarding their sensitivity to manufacturing tolerances. An optimized filter design shows improved robustness against manufacturing tolerances. This concept particularly reduces the sensitivity to registration tolerances of conductors and ground vias. A filter synthesis and simulation which takes into account systematic and random manufacturing effects takes out some of the guesswork of filter design and fabrication. It will also reduce the trial and error loops traditionally involved with this part of microwave engineering.

Differential-Type CRLH Leaky-Wave Antenna Using Stepped Impedance Resonators

A composite right/left-handed (CRLH) leaky-wave antenna (LWA) using a stepped impedance resonator (SIR) is presented. By applying the SIR technique to a conventional CRLH structure, a balanced condition is achieved through the adjustment of the SIR parameters. Therefore, the structure requires no interdigital or multilayered capacitor to achieve the balanced condition. A differential microstrip configuration is also used for the utilization of a virtual ground to eliminate the need for ground vias. The simplicity of the structure allows for applications at high frequencies. An LWA consisting of 14 unit cells of the proposed structure is designed and measured. Continuous beam scanning from the backward direction to the forward direction is demonstrated.

Gap Waveguide-Based PMC Packaging for via Holes-Caused Nonsmooth PEC Surface

We investigate the application of perfect magnetic conductor (PMC) packaging for a nonsmooth perfect electric conductor surface, caused by metalized via holes. The PMC shielding is artificially built by a metal lid of pins, based on the gap waveguide (GW) technology. As a foundation, the effects of via hole in a unit cell are studied first considering its diameter, substrate thickness, pin size, pin height, as well as relative position between the via hole and the pin. The via adjacent space and pin rows are also considered for a general grounded coplanar waveguide along with ground vias. The effectiveness of package for such a transmission line containing metalized via holes is then verified experimentally. It is shown that the measured performance agrees well with the simulation. This paper presents a guideline for the GW-based PMC packaging technology.

BPF integrated amplifier module using LTCC technology for millimeter‐wave applications

ABSTRACTA compact amplifier module integrating a low‐loss stripline (SL) band‐pass filter (BPF) using low‐temperature cofired ceramic (LTCC) technology is presented for millimeter‐wave (mm‐wave) applications. A parasitic resonance‐free SL BPF is proposed by modifying a distribution of ground vias in the SL LTCC BPF. The SL BPF fabricated in the 6 LTCC layers showed a 3‐dB bandwidth of 8.4% at the center frequency of 41.8 GHz. Its measured insertion and return loss were as small as 1.7 dB and 10.2 dB, respectively. The SL BPF integrated amplifier LTCC module was implemented in the single LTCC substrate in a size of 11.3 × 12.2 × 0.6 mm3. Its gain of 10 dB and output power of 18 dBm is achieved in the pass band from 39.5 to 42 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1821–1825, 2015

Chebyshev Filter Design Using Vias as Quasi-Transmission Lines in Printed Circuit Boards

This paper presents a novel concept for microwave filter design using vias (plated through-holes) in multilayered printed circuit boards. By using the concept that vias accompanied by a sufficient number of ground vias in close proximity can be approximated as transmission lines in a certain frequency range, corresponding effective impedances and phase velocities for different configurations of vias and ground vias are deduced. By controlling these transmission-line parameters, standard microwave filter methodology is applied for the design of low-pass and bandpass Chebychev filters in the frequency range of 5–20 GHz. Measurements and full-wave simulation results are presented as validation. Advantages and limitations of the proposed method are discussed.

Dual-band differential bandpass filter using stepped impedance resonators

In this article, a novel dual-band differential bandpass filter using (SIRs) is designed. To demonstrate the design ideas, the differential and common mode equivalent half circuits are built and studied. Two resistors are connected between the two ends of the SIRs to consume the power in common mode. A capacitor is connected between the Ground and Center of the SIR to adjust the spurious frequencies, also strength the coupling of the two SIRs. The theoretical analysis shows the second band can be obtained by the proper impedance ratios of the resonances and the capacitor connected to the resonator. Two through ground vias (TGVs) connecting the top and bottom sides of the SIR filter, are used to realize the common mode rejection. To investigate the proposed filter in detail, a set of design equations are derived based on the circuit theory and transmission line theory. A phototype dual-band differential filter operating at 1.5 and 2.75 GHz has been realized to validate the proposed concept and theory. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:468–473, 2015.

Modeling and Design of Microstrip Patch Antenna-in-Package for Integrating the RFIC in the Inner Cavity

This letter presents the circuit model of the antenna-in-package (AiP) for integrating the RFIC in the inner cavity. The closed-form expression for the inductance of the ground via is provided in the case that two ground vias are arranged under the nonradiating edge of the AiP. The new expression takes account of the radius and length of the vias, the relative positions of vias, and the distances between via holes and the feeding point of the antenna. Based on the circuit model, the influences of vias on the performance of the AiP are analyzed. It is found that the bandwidth of the AiP can be effectively improved by properly arranging two via holes under the nonradiating edge of the antenna. Finally, an AiP with the center frequency of 5.12 GHz is realized, and a bandwidth of 400 MHz is obtained. The calculated results are in agreement with the simulated and measured.

Efficient DC Analysis of Power Planes Using Contour Integral Method With Circular Elements

Contour integral method, well-known for the analysis of 2-D full-wave effects on power planes, is extended here for the computation of DC resistances of power planes. In particular, circular elements, e.g., vias and antipad holes, are treated using cylindrical modal expansion functions, which leads to a more efficient and accurate calculation than the conventional implementation by the linear discretization. For individual power planes, the method produces a resistor network consisting of only the nodes that are associated with power or ground vias, which can be further employed to formulate solutions for complete multilayer structures. The method is applied to several power plane configurations and results are validated by a 3-D finite element method solver. The efficiency of the extended method is analyzed and a reduction of the number of unknowns by a factor of four for the circular elements can be expected by the modal expansion. Good accuracy can be achieved by including up to the second higher order mode for dense clusters of antipad holes.