Antenna-in-package Research Articles

Miniaturized Dual-Band Broadside/Endfire Antenna-in-Package for 5G Smartphone

This paper proposes a miniaturized antenna in package (AiP) for 5G millimeter-wave smartphone that incorporates broadside and end-fire arrays and supports a dual band covering 28 and 39 GHz. This paper demonstrates that the proposed AiP is 5.8 mm × 19 mm × 1.122 mm. It is believed that this is the smallest 5G AiP that can support a 10 dBi antenna gain, a 10 dB return-loss bandwidth of 3 GHz, and more than 10 dB isolation for both broadside and end-fire arrays. AiP consists of a 1 × 4 patch antenna array for broadside radiation and a 1 × 4 dipole antenna array for end-fire radiation. To miniaturize the patch antenna elements, a multi-layer Reactive Impedance Surface (RIS) is embedded between the patch layer and the ground plane. This multi-layer RIS idea greatly fits in 5G PCB-stack up antennas where each stack-up layer essentially requires certain portion of copper area. For the end-fire array antenna miniaturization with bandwidth improvement is achieved by modifying the Vertically Bent Folded Dipole Antenna (VBFDA) and adding a tightly-coupled T-shape side via wall. The AiP achieves a 10 dB return-loss bandwidth of 26.22 to 29.57 GHz and 35.18 to 41.00 GHz for Multi-Layer RIS Patch Antenna(MLRPA), and 26.40 to 29.74 GHz and 36.65 to 40.72 GHz for VBFDA. The antenna gain is 11.6 dBi for MLRPA and 10.0 dBi for VBFDA.

Structured glass substrates in wafer- and panel level packaging: Status and recent achievements.

Abstract Glasses can be used as core substrate for panel- and/or wafer-level packaging to achieve heterogeneous integration of chiplets and integrated passives in increasingly complex packages. Glass has a large number of advantages: The stiffness of glass (i) allows manufacturing of highly accurate buildup layers. These buildup layers can have manufacturing precision of 1μm and below on large dies with sizes of 50mm x 50mm and more, needed for antenna in package (AiP) applications and high performance computing (HPC). Special glasses can be made with adjusted thermal expansion (CTE) (ii), either adjusted to silicon or with larger thermal expansion to allow packages with buildup layers of epoxy molds and metallization that see high thermal loads either during manufacturing or during operation. Glasses can also be optimized with very good dielectric properties (iii) and can be utilized in antenna-in-package applications. But most of all, economic glass structuring techniques (iv) which can provide millions of vias and thousands of cut-outs in a glass panel are important and are being developed. SCHOTTs Structured Glass Portfolio FLEXINITY® and related technologies provide an excellent starting point for highly sophisticated structured glass substrates required for Advanced Packaging. The biggest hurdle for a large-scale commercialization of glass panel packaging is industrial readiness along the whole process chain. This is needed, to bring glass panel packaging in applications like IC-packaging, RF-MEMS packaging and medical diagnostics or, in combination with cutouts for fan-out, embedding of active and passive components. In addition, metallization processes with good adhesion, excellent electrical properties and high geometric accuracy for glasses are an important step. In the current manuscript, we review the status and discuss our contribution towards achieving industrial readiness for glass in panel- and wafer-level packaging.

Low Temperature Curable Low Dk & Df Polyimide for Antenna in Package

Abstract In this paper, we developed novel low temperature curable (around 200~250 °C) low Dk (2.7) & Df (0.002) polyimide with high glass transition temperature (170 °C) and elongation (100%). We also developed negative tone photosensitive polyimide with low Dk (3.0) & Df (0.007) by photo initiator and cross linker. Material types of them are liquid or B-stage sheet materials. Patterning methods of the non-photosensitive polyimides were imprint and UV laser ablation. Resolution of those process were 10um via and 30um via respectively. Photosensitive polyimide was patterned by photolithographic tool. We fabricated fine patterned polyimide of photosensitive polyimide by photolithography. We investigated the frequency dependence of the novel low Dk & Df polyimide up to 95 GHz, and confirmed that Df gradually increased from 0.002 to 0.005 as the frequency increased. To confirm effect of the novel polyimide, insertion loss of micro-strip line whose length was 10 mm were measured using the new developed polyimide. Insertion loss (S21 parameter) of the novel polyimide was 0.8 and that was less than half of conventional polyimide. RDL structure was fabricated by novel low Dk and Df polyimide and we tested bump shear strength after thermal cycle test. All shear mode were ductile solder failure without polyimide delamination. Because our novel polyimides show excellent dielectric, thermal and mechanical properties, they are suitable to insulator of RDL for FO-AiP.

A Hybrid Antenna in Package Solution Using FOWLP Technology

Abstract Widespread millimeter wave applications have promoted rapid development of system in package (SiP) and antenna in package (AiP). Most AiP structures take the form of flip chip onto antenna substrate, where signal interconnect losses are introduced by solder bumps. The integration may be unavailable for chips with fine pad pitches. Fan-out wafer level package (FOWLP) with antenna patterning on redistributed layers (RDL) is another method for millimeter wave AiP. In this project, a hybrid integration AiP structure is developed. The microwave monolithic integrated circuit (MMIC) chip and antenna unit are integrated with chip-first FOWLP process. Multilayer organic substrate with fine pitch RDL interconnections meets the requirements of wideband antenna design. Modified coplanar waveguide is adopted to feed 2 × 2 aperture array formed on RDL layer. Package warpage is measured using Shadow Moire techniques. The antenna forms an aperture-coupled stacked patch array with bandwidth 25% and gain 8.5dBi for 60 GHz digital communication system. The proposed approach is a convenient hybrid integration solution adopting FOWLP process for millimeter wave AiP systems.

A Wideband Compact Magnetoelectric Dipole Antenna Fed by SICL for Millimeter Wave Applications

A wideband compact magnetoelectric (ME) dipole antenna is investigated for millimeter-wave applications. First, an aperture coupled ME dipole is proposed with wideband and low profile. Next, transverse slots are added to miniaturize the antenna. The radiation performance of the higher-order mode is also improved. The antenna is finally miniaturized to 2.5×3.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ( 0.27 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.35 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space at center frequency) when it is used in the array environment. A bandwidth of 48.8% (24.3-40 GHz) for SWR <; 2 can be achieved, with unidirectional radiation performance over the operating band. By combining the proposed compact antenna with an eight-way substrate integrated coaxial line (SICL) feed network, a 1 ×8 linear array is designed, fabricated, and measured. Good beam scanning capability is also verified by active simulation. With the advantages of wide bandwidth, compact size, promising radiation pattern and wide-angle beam scanning potential, the proposed antenna would be attractive for millimeter-wave devices and antenna in package (AiP) applications.

Over-the-Air Array Calibration of mmWave Phased Array in Beam-Steering Mode Based on Measured Complex Signals

Accurate knowledge of initial complex excitation coefficients for phased-array elements is essential to ensure accurate array performance. In the literature, many array calibration algorithms have been proposed for this purpose, which generally requires customized phase setting for individual phase shifters connected to array elements. In this article, a new array calibration method is proposed for phased array operating in beam-steering mode only, that is, phase shifts of elements are only simultaneously set according to the beam-steering directions, and therefore, there is no need for dedicated individual element phase tuning. The proposed method requires a minimum number of complex-signal measurements in principle, which enables fast measurement. Furthermore, it is found that the performance of the proposed method is determined by the beam-steering matrix, whose condition number is mainly ruled by the beam-steering angle interval. The proposed method is numerically simulated and experimentally validated in a millimeter-wave (mmWave) phased-array antenna-in-package (AiP) platform at 28 GHz. The proposed method presents good agreement with the well-known rotating element electric field vector (REV) array calibration method, with an amplitude error and phase error within ±0.5 dB and ±5°, respectively. Furthermore, the reconstructed array pattern with the proposed method offers excellent match with the measured array pattern.

An Ultrawide Ku- To W-Band Array Antenna Package Using Flip-Chipped Silicon Integrated Passive Device With Multilayer PCB Technology

A new antenna-in-package (AiP) solution for a tightly connected bowtie array antenna using a silicon-based integrated passive device (IPD) on a multilayer printed circuit board (PCB) is developed. The proposed IPD antenna is flip-chipped on the PCB through solder balls and gold studs, whereas a vertical coax-via-based feeding structure is used to provide differential excitation. The proposed 5 × 5 array AiP shows a bandwidth of 18.58-100 GHz with differential VSWR ≤ 3.5 when only exciting the central antenna element. The simulations are validated through the fabrication and measurement of prototypes, demonstrating a reasonable agreement in differential VSWR and radiation patterns.

An Overview of Probe-Based Millimeter-Wave/Terahertz Far-Field Antenna Measurement Setups [Measurements Corner

In recent years, there has been great interest in millimeter-wave (mmwave) and terahertz (THz) technologies due to an increasing demand for ultrahigh data transfer rate. Two novel solutions, i.e., antenna on chip (AoC) and antenna in package (AiP), have been proposed for the development of highly integrated radio and radar systems [1]-[5]. To measure the antenna characteristics of AoC and AiP, a reliable probe-based mm-wave/THz antenna measurement setup became essential. Over the last 20 years, the world has witnessed the prosperous development of various mmwave/THz antenna measurement setups, most of which can be divided into two types, i.e., probe-station and quasi-in-air based. The former type has a feature that allows the testing equipment to be compactly established on a large metal stage, which has been widely used for near-field based and as part of the farfield-based setups [6]-[10]. The antenna under test (AUT) is maintained on a wafer chuck placed on the stage and thus, only the radiation pattern in the upper half-space is measurable due to the metal stage obstruction. The latter type reduces the defect by using an extended supporting structure to hold the AUT in midair away from the stage so that the radiation patterns in both the upper and lower half-spaces are measurable. Many setups of this type measure antennas at far-field distances, and some of them are also compatible with near-field testing. Compared to probe-station based, quasi-inair based takes up much more space and is less compact.

A Wideband Differentially Fed Dual-Polarized Laminated Resonator Antenna

A wideband differentially fed dual-polarized laminated resonator antenna (LRA) is presented in this communication. Two differential pairs of L-probes are inserted into the LRA to excite degenerate dominant modes in LRA for dual-polarized operation. As a proof of concept, a prototype antenna centered at 5 GHz is designed, fabricated, and measured. The measured results agree well with the simulated ones. The experimental results show that the designed antenna achieves a wide bandwidth of 29% with differential reflection coefficient less than -10 dB. Moreover, it exhibits stable and symmetrical radiation patterns within the bandwidth. Benefiting from the differentially fed scheme, high port-to-port isolation better than 35 dB and low cross-polarization level less than -25 dB are achieved across the entire operating band. The proposed antenna is the first differentially fed dual-polarized LRA. Taking advantage of its planar structure integrated in the substrate, the proposed antenna is a promising candidate for future 5G wireless communications and antenna-in-package (AiP) solutions in millimeter-wave frequencies.

H-Band Quartz-Silicon Leaky-Wave Lens With Air-Bridge Interconnect to GaAs Front-End

Thanks to the large bandwidth availability, millimeter and submillimeter wave systems are getting more attractive to be used in a wide range of applications, such as high-resolution radar or high-speed communications. In this contribution, a new lens antenna in-package solution is presented for the H-band (220–320 GHz), including a wideband quartz-cavity leaky-wave feed combined with an air-bridge chip interconnect technology, based on spray coating and laser lithography. This interconnection acts as a wideband, low-loss transition between the GaAs front-end and the quartz antenna, avoiding the use of expensive waveguide split-blocks. An antenna prototype including the interconnect has been manufactured and characterized, validating the full-wave simulated results for the integrated H-band leaky-wave with aperture efficiency higher than 74% over 34% bandwidth, and radiation efficiency higher than 70% over 37% of bandwidth.

Experimental Comparison of On–Off and All-On Calibration Modes for Beam-Steering Performance of mmWave Phased Array Antenna-in-Package

Antenna-in-package (AiP) technology has been implemented for millimeter-wave (mmWave) phased array design with antenna elements and radio frequency (RF) chips integrated. The radiation pattern beam of mmWave phased array AiP is typically steered after the in-homogeneous RF branches are aligned (i.e., AiP calibration). The RF branch discrepancies among elements are directly obtained with one element enabled sequentially each time (i.e., on–off mode) by default in the industry. A recent study has reported that the AiP element branch discrepancies obtained in the on–off mode might be different from those obtained in the normal all-on working mode with all elements active. However, experimental results that demonstrate the impact of the difference between the two calibration modes on the beam-steering performance of mmWave phased array AiP have been rarely reported in the literature. In this article, the beam-steering performance of two mmWave AiPs after the two calibration modes is experimentally compared, which is demonstrated by the beam-steering pattern defined in this article. Following the statement on the source of difference between the two calibration modes of AiP, the system model is described for the calibration and beam-steering measurements of AiP in the experimental campaign. Experimental results show that the on–off calibration mode obtains the same beam-steering performance as the all-on mode for the main beam pattern, though element branch discrepancies obtained in the two modes are different.

Evolution of Innovative 5G Millimeter-Wave Antenna Designs Integrating Non-Millimeter-Wave Antenna Functions Based on Antenna-in-Package (AiP) Solution to Cellular Phones

This article presents an inspiring retrospect and prospect on the evolution of innovative 5G millimeter-Wave (mm-Wave) antenna designs integrating non-mm-Wave functions based on the antenna-in-package (AiP) solution to cellular phones. The innovative designs include mm-Wave antennas-in-package integrating non-mm-Wave antennas (AiPiA), mm-Wave antennas-in-package as non-mm-Wave antennas (AiPaA), and mm-Wave antennas-in-package integrating and as non-mm-Wave antennas (AiPiaA). In comparison with conventional AiP-based mm-Wave antenna designs, these designs advance to achieve the total solutions for the 5th generation mobile communications (5G) antennas to cellular phones, which remarkably benefit design efforts of antenna designers for cellular phones, occupied space by antennas in cellular phones, and applications of 5G antennas to cellular phones.

A Review of Design and Integration Technologies for D-Band Antennas

This article reviews the current state-of-the-art of millimeter-wave (mm-wave) antennas for communication and sensing applications in the D-band between 110 and 170 GHz. The most popular design techniques, including Antenna-on-Board (AoB), slotted waveguides, Antenna-in-Package (AiP) and Antenna-on-Chip (AoC), are described using relevant examples from scientific literature. Potential benefits and limitations of integration technologies, such as specialized packaging, chip post-processing steps and interconnects, are listed as well. The reported performances of all listed designs are compared against each other, taking the antenna size relative to operating frequency into account. This novel comparison indicates that small-scale integrated AiP and AoC designs can achieve competitive performance levels with short and low-loss interconnects.

A 60 GHz Millimeter-Wave Antenna Array for 3D Antenna-in-Package Applications

This paper presents a 60 GHz millimeter-wave (mm-wave) antenna array using standard printed circuit board (PCB) for 3D Antenna-in-package (AiP) implementation. The array consists of a 4 microstrip patch elements, differentially fed with an open stub matching feed network to enable 3D integration. The $1\times 4$ finite antenna array with ball grid array (BGA) and silicon (Si) interposer operates from 58.46 to 62.14 GHz with 3.6 GHz instantaneous bandwidth, low mutual coupling of about $1\times 4$ array consists of two substrates and one bondply layer with antennas, via-to-open stub matching network, and a differential to single-ended corporate feed network for the measurement. A prototype with a differential to single-ended corporate feed network was fabricated and tested showing a gain of about 10.02 dBi at the operating frequency with $\geq 90$ % radiation efficiency. Such a gain and efficiency make the presented design a leading candidate for 3D AiP applications.

A Wideband Dual-Polarized Antenna for Millimeter-Wave Applications

A wideband dual-polarized magneto-electric (ME) dipole for millimeter waveband applications is presented. The ME dipole consists of four shorted patches, which are fed by two pairs of T-shaped probes orthogonally oriented on the same layer. The feed lines are connected with the T-shaped probes through metallic vias. Simulated overlapped impedance bandwidth of 50% with return loss larger than 10 dB, gain up to 9.4 dBi, and isolation higher than 17.8 dB between dual polarizations are achieved. By combining the antenna elements with single-layered feed networks, a 2 ×2 array is designed, fabricated, and measured. The overlapped working bandwidth is 50%, with gain up 14.8 dBi. With the advantages of wide bandwidth, single-layered radiation structure, and promising radiation pattern, the proposed antenna with dual polarizations would be attractive for millimeter-wave antenna in package (AiP) applications.

2020 John Kraus Antenna Award

The 2020 award was presented to Yueping Zhang and Duixian Liu “For pioneering and significant contributions to the development of antenna-in-package (AiP) technology.”

Adaptive 5G Architecture for an mmWave Antenna Front-End Package Consisting of Tunable Matching Network and Surface-Mount Technology

Adaptive 5G architecture consisting of three functional sections (four antenna components, tunable matching network (TMN), and radio frequency (RF) front-end package) is proposed, analyzed, and verified. In the 5G millimeter-wave (mmWave) spectrum, the RF performance is highly dependent on the specific antenna package technology. However, compact antenna packages, oftentimes, result in undesired interference between the antenna elements. This eventually leads to severe RF performance degradation. For the first time in the literature, an mmWave 5G RFIC and the TMN are integrated for efficient operation that is applicable to real-life 5G mobile devices. Moreover, the proposed antenna-in-package (AiP) architecture enables independent frequency control at multiple frequencies. The proposed solution is simulated and measured at the system level. As a result, the devised AiP solution exhibits a simulated effective isotropic radiated power (EIRP) of 22.05–23.96 dBm at the cumulative distribution function (CDF) of 50% by applying the conducted power of 17 dBm (per channel), and the peak gain of the antenna exhibits 13.7 dBi at 27 GHz (state A) and 12.6 dBi at 28 GHz (state B) with an amplifier having an output power of 5 dBm.

Low‐profile and low‐cost transmitarray antenna at 122 GHz based on unit‐cells with 1‐bit phase resolution

This Letter presents the design of a low-profile and low-cost transmitarray antenna operating at 122 GHz. The transmitarray design is based on unit-cells with 1-bit phase resolution. A single RO4350B substrate layer is used to form the unit-cells resulting in a total thickness of 0.326 mm. A wideband shift in the transmission phase of 180 ° is generated by rotating one metal layer of the unit-cell by 180 ° . The simulation of the transmitarray with 30 × 30 elements and a feed distance of 35 mm shows a maximum directivity of 28 dBi at 122 GHz. Steering angles of 0 ° and 15 ° are investigated. Measurements of the fabricated transmitarrays are performed with an open waveguide and a package antenna as feed showing similar results but slightly different maximum relative gain values of 11.8 and 9.5 dB for the 0 ° version. The measured main beam directions are in good agreement with the simulations and the design values.

Comparison of 122 GHz Lens Antennas for System-on-Chip FMCW Radar With Minimum Back Reflection and High Gain

Three different dielectric lens antennas are designed to enhance range of a commercially available 122 GHz radar system-on-chip transceiver with antennas in package. A Fresnel-zoned lens antenna, a plano-hyperbolic lens antenna with one-refracting surface, and a conventional plano-hyperbolic lens antenna with two refracting surfaces are compared. All lens antennas are made of Teflon (PTFE). Problem of back-reflection and its degrading effect on radar performance is addressed. In addition to simulations, an in-house 122 GHz radar system utilizing a system-on-chip transceiver is used to measure radiation pattern, gain, and back-reflection. It is shown that conventional plano-hyperbolic lens antenna with two-refracting surface has higher gain and lower back-reflection than plano-hyperbolic lens antenna with one-refracting surface. However, weak targets near the radar can only be detected by Fresnel-zoned lens antenna which causes no additional back-reflection. If transmit power is increased, Fresnel-zoned lens antenna outperforms conventional plano-hyperbolic lens antenna with two-refracting surfaces.

Low Cost AIP Design in 5G Flexible Antenna Phase Array System Application

In this paper, a low cost 28 GHz Antenna-in-Package (AIP) for a 5G communication system is designed and investigated. The antenna is implemented on a low-cost FR4 substrate with a phase shift control integrated circuit, AnokiWave phasor integrated circuit (IC). The unit cell where the array antenna and IC are integrated in the same plate constructs a flexible phase array system. Using the AIP unit cell, the desired antenna array can be created, such as 2 × 8, 8 × 8 or 2 × 64 arrays. The study design proposed in this study is a 2 × 2 unit cell structure with dimensions of 18 mm × 14 mm × 0.71 mm. The return loss at a 10 dB bandwidth is 26.5–29.5 GHz while the peak gain of the unit cell achieved 14.4 dBi at 28 GHz.