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This paper presents a large-scale base station antenna assembly structure that is low-cost, reliable, and easy to manufacture. The antenna element is composed of a low-loss liquid crystal polymer based on a plastic molded module and a modified wideband stacked patch antenna. The base station antenna consists of a 4 × 8 antenna module, with each module comprising 3 × 1 subarrays along with dual-polarized antenna elements. The antenna element achieved an efficiency of 91% and an impedance bandwidth of 1.14 GHz within a height of 10 mm at 3.7 GHz. Furthermore, the fabricated array antenna structure was tested and verified to have an effective isotropic radiated power of 75.6 dBm at boresight and a steering range of less than ±60°. Therefore, the proposed structure meets the required antenna and beam-forming performance for commercial 5G active antenna systems.

This paper presents an ultra-broadband, low-loss, flexible liquid crystal polymer substrate-to-substrate interconnect with a bandwidth of more than 130 GHz. The transition discontinuity was minimized by maintaining both the reference impedance and the electromagnetic field conformity across the transition from alumina substrate to flip-chip foil. Therefore, more than 600 $\mu$m long flexible flip-chip interconnects can be realized for bridging millimeter-wave sub-modules and enabling ultra-broadband heterogeneous system design with a measured return loss of above 20 dB. Furthermore, the interconnect can realize ramp interconnections between monolithic microwave integrated circuits or substrates with different substrate heights due to the flexible foil substrate. Minimum parasitic radiation at the transition is realized through a closely spaced signal-to-ground connection. Furthermore, the robustness of the proposed interconnect against lateral misalignment in the assembly is presented through simulation and measurement. An outstanding insertion loss of less than 0.3 dB per transition over a bandwidth of more than 130 GHz is shown.

Lightweight and deployable phased arrays are important in Small-Satellite (Small-Sat) constellation systems to reduce price and increase link distance. This article proposes a Ka-band deployable active phased-array TX on a 4-layer liquid crystal polymer (LCP) board for a lightweight and high stowage rate solution to break through the trade-off between high antenna aperture size and small form factor in phased arrays. This article describes detailed designs of the phased array and its building blocks with the proposed 4-layer LCP substrate structure. Assembled with the beamformer ICs (BFIC), a Ka-band $8 \times 4$ -element deployable active phased-array TX on the 4-layer LCP substrate is fabricated. The proposed deployable phased-array TX can steer the beam from −50° to 50°. The phased-array TX can drive 32-APSK DVB-S2 signal with a −28.7 dB EVM as well, revealing that the deployable phased-array TX performs with high phased-array performance. Furthermore, the TX achieved the lightest and thinnest phased array with 0.96 kg/m2 areal mass and 0.9 mm thickness. This groundbreaking research sets the stage for the realization of affordable and user-centric satellite communication (SATCOM) in low-earth orbit (LEO).

Liquid crystal polymer (LCP) with excellent microwave and millimeter-wave properties is widely applied in high frequency multilayer substrates. The design of an excellent via-hole transition in multilayer circuits board is important to employ as an interconnect to route signal traces on different layers or connect components. Recently, with the operating frequency increasing, the problem of discontinuity in the via-hole transition structure has become increasingly prominent. Therefore, electromagnetic modeling of via-plate-pair structures is essential for the design of microwave and millimeter-wave circuits. In this paper, an efficient and fast via-hole transition modeling method for the ground coplanar waveguide-strip line-ground coplanar waveguide(GCPW-SL-GCPW) structure based on the four-layer LCP circuit board is proposed. By segmented modeling of the multilayer structure and introducing a fast convergence algorithm in the parasitic parameter calculation process, a via-hole lumped parameter equivalent circuit structure is established. Finally, the equivalent circuit model of the GCPW-SL-GCPW structure is quickly constructed based on the microwave network cascade method. Compared with the full-wave simulation results of HFSS high frequency structure simulator, which is a 3D high-frequency electromagnetic software, it is found that this modeling process is simple and fast. The GCPW-SL-GCPW circuit structure has been fabricated using the LCP multilayer process. The test results show that the test results and the equivalent circuit analysis results are highly consistent in the wide frequency range of 10 MHz—40 GHz, which verifies the effectiveness of the via-hole transition modeling method.

Summary: This work presents a compact and conformal frequency reconfigurable antenna for automotive applications. The antenna is designed on a liquid crystal polymer substrate of footprint 40 × 30 × 0.1 mm3. The proposed antenna is having coplanar waveguide feeding with a circular ring radiating element and a pair of parasitic circular elements to obtain the multiband operation. The proposed antenna is studied for frequency reconfigurable characteristics by placing the PIN diodes as switching elements in the desired locations and obtained the reconfigurability in the 4.5–6.5 GHz region. Further, the bending effects of the antenna with respect to its operating bands and the conformal effects with PIN diodes for the reconfigurable performance make this study a trailblazing work. The simulated and measured results describe that the on‐glass conformal antenna is covering 1.58–2.33 (GPS, PCS, GSM1800/1900), 3.22–3.7 (WiMAX), and 4.25–6.8 GHz (WLAN, DSRC, WAVE, V2X) bands for vehicular communications with various switching cases. The obtained gain varies from 3.2 to 4.1 dB in the boresight direction and 6.9 to 9.8 dB in the lateral directions of the vehicle with placement on the vehicle body. As per the obtained results, the antenna is suitable to use for conformal usage on the windshield glass of the vehicle for connected driving scenarios. [ABSTRACT FROM AUTHOR]

A 2 × 2 ultra-wideband MIMO flexible antenna with a low profile and good isolation was designed for Internet of Things (IoT) realms and wearable devices. The antenna elements were placed on a novel flexible substrate of liquid crystal polymer (LCP) with compact dimensions fed by a coplanar waveguide (CPW). In order to ameliorate isolation, the cross-shaped decoupling branches were placed among the antenna elements. The proposed UWB antenna can operate from 2.9 GHz to 10.86 GHz with a good reflection coefficient of S11 < −10 dB as well as a high isolation better than 22 dB. Its operating bands include 5G, WiFi, X-band, etc. Moreover, the parameters of diversity performance were also tested. These parameters included an average gain of approximately 4 dB, a low ECC of less than 0.01, and good diversity gain of 9.999. The flexible MIMO antenna performs well in bending and on-body conditions. To sum up, the antenna has good prospects in IoT applications and wearable fields. [ABSTRACT FROM AUTHOR]

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A quasi-reflectionless frequency division multiplexer (FDM) with directional filters (DFs) in multilayer liquid crystal polymer (LCP) substrates is proposed for $E$ - and $W$ -band applications. The in-series cascaded DFs are designed at 74, 84, and 94 GHz, each of which comprises two microstrip lines in the first layer, two pairs of coupling slots in the second layer, and loop resonators in the third layer. The distance between DFs is optimized for suppressing reflection and insertion losses, and the asymmetric distribution of DFs is designed to obtain a low profile. The experimental data demonstrate a 3-dB passband of 8.3%, 8.8%, and 9.7% centered at 74, 84, and 94 GHz, respectively, for the proposed FDM, showing a good match with the simulation. The corresponding insertion loss is measured as 3.63, 3.4, and 2.72 dB at 74, 84, and 94 GHz, respectively. The proposed device may find many applications in multiband and ultrawideband communication and radar systems. [ABSTRACT FROM AUTHOR]

In this paper, a 4-pole quasi-elliptic planar bandpass filter at Q-band on the liquid crystal polymer (LCP) is presented. The conventional design and development process of millimetre wave filters required to consider the surface roughness effects from the design stage for accurate development of filter at high frequency. Finite surface roughness of rolled copper and its impact on electrical performance are studied. Polishing is one of the methods to improve the conductor surface roughness. An improvement of 50% in surface roughness is reported for the rolled copper on the LCP, resulting in better than 1 dB insertion loss of the bandpass filter. Commensurate simulation and measurement results are presented. [ABSTRACT FROM AUTHOR]

A compact coplanar waveguide-fed triple-band multiple input multiple output (MIMO) antenna is designed based on flexible substrate named liquid crystal polymer in this work. The proposed antenna comprises two antenna elements placed side by side. By adding a double Y-shaped branch between two antenna elements, good isolation is achieved successfully, which is better than 21 dB. According to the measured results, it can operate bandwidth covering 2.263–2.925, 3.063–4.5 and 4.588–7.25 GHz, meeting the radio spectrum, including 5G, WLAN and WiMAX. Moreover, the proposed antenna also has virous suitable characteristics including envelope correlation coefficient (<0.01), diversity gain (>9.99), channel capacity loss (<0.4 bits/s/Hz), the difference of mean effective gain (<0.15 dB) and total active reflection coefficient (<−10 dB). The bending test and the effect of human body have also been analyzed. The actual measurement indicates that the presented MIMO antenna is desirable for integration in wearable 5G/WLAN/WiMAX devices. [ABSTRACT FROM AUTHOR]

Minimizing the size of mobile antennas is necessary for integrating the components inside a mobile device. Wideband and multiband antennas are also required to cover various 5G mobile communication frequency spectra. This article presents a vertically stacked dipole antenna array operating in the 28/38 GHz dual-band. The proposed antenna is small and satisfies the need for wide bandwidth in the form of a dual band. The antenna structure has symmetric 38 GHz band radiators positioned above and below a multilayer substrate, and a 28 GHz band radiator positioned on the middle plane, providing a dual-band antenna structure with small lateral width. Herein, two types of antenna structures are proposed, each with a single-ended and differential feed structure for compatibility with various RF front ends. The single antenna yields −10 dB bandwidth for return loss of 23.9% and 14.4%, and gain of 4.8 and 4.6 dBi at 28 and 38.5 GHz, respectively. The 4-element antenna array yields a gain of 9.0 dBi at 28 GHz and 10.3 dBi at 38.5 GHz. It was fabricated on a flexible substrate and can be bent and inserted into the lateral edge of the terminal. The proposed antenna elements and arrays satisfy the performance factors requisite for millimeter wave 5G communication including compact size, wideband, dual-band, and adequate gain. [ABSTRACT FROM AUTHOR]

Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP-based bioelectronic device, however, still necessitates a low form factor packaging solution to protect the electronics in the body. In this work, we investigate two promising encapsulation coatings based on thin-film technology as the main packaging for LCP-based electronics. Specifically, a HfO2–based nanolaminate ceramic (TFE1) deposited via atomic layer deposition (ALD), and a hybrid Parylene C-ALD multilayer stack (TFE2), both with a silicone finish, were investigated and compared to a reference LCP coating. T-peel, water-vapour transmission rate (WVTR) and long-term electrochemical impedance spectrometry (EIS) tests were performed to evaluate adhesion, barrier properties and overall encapsulation performance of the coatings. Both TFE materials showed stable impedance characteristics while submerged in 60 °C saline, with TFE1-silicone lasting more than 16 months under a continuous 14V DC bias (experiment is ongoing). The results presented in this work show that WVTR is not the main factor in determining lifetime, but the adhesion of the coating to the substrate materials plays a key role in maintaining a stable interface and thus longer lifetimes. [ABSTRACT FROM AUTHOR]

In this article, a co‐planar waveguide‐fed ultra‐wideband (UWB) multiple‐input multiple‐output flexible antenna with dual band‐notched characteristics on liquid crystal polymer substrate with high isolation for wireless body area network application is designed and fabricated. Two fan‐shaped monopole UWB antenna elements are designed and placed vertically, with tampered feeder, asymmetrical ground plane and two C‐shaped slots on the radiation patch. The measured working bandwidth can reach 2.63–11.6 GHz and the rejection bands are 3.25–4.36 and 5.41–6 GHz. The port isolation (S21) is better than −22 dB. When the bending radius is 35 and 45 mm, the antenna is measured for flexibility. In addition, the antenna is placed on human tissue to test its performance. All the results show that it has good radiation, high isolation and flexibility, and has broad application prospects in the wearable field. [ABSTRACT FROM AUTHOR]

For polymer matrix microwave composites, the agglomeration of ceramic particles at a high filling ratio will cause the microwave dielectric properties, mechanical properties and thermal conductivity of the materials to deteriorate sharply. This paper examines the reinforcement effect of LCP A950 fibers on PTFE and ZnNb 2 O 6 /PTFE composites to prevent this phenomenon. SEM, DMA, and other analysis methods showed that the incorporation of a small amount of LCP can promote the crystallization of PTFE and the mechanical strength of composites. When the volume fraction of the ZnNb 2 O 6 /PTFE/LCP three-phase is 50/45/5, the composites have a medium dielectric constant (ε r = 6.46), extremely low loss (t a n δ = 7.54 × 10−4) and a near-zero temperature coefficient of the dielectric constant (τ ε = +2.25 ppm/°C). Under the same conditions, the linear expansion coefficient of the material is 45.4 ppm/°C, which is 30.5% lower than that before doping with LCP, and the flexural strength is 37.8 MPa, which is an increase of 17% com、pared to the previous value. The LCP-reinforced composites have excellent overall properties, but when the LCP content is too high, its reinforcement effect on the composites is gradually weakened. [ABSTRACT FROM AUTHOR]

A 2 × 2 ultra-wideband MIMO flexible antenna with a low profile and good isolation was designed for Internet of Things (IoT) realms and wearable devices. The antenna elements were placed on a novel flexible substrate of liquid crystal polymer (LCP) with compact dimensions fed by a coplanar waveguide (CPW). In order to ameliorate isolation, the cross-shaped decoupling branches were placed among the antenna elements. The proposed UWB antenna can operate from 2.9 GHz to 10.86 GHz with a good reflection coefficient of S11 < −10 dB as well as a high isolation better than 22 dB. Its operating bands include 5G, WiFi, X-band, etc. Moreover, the parameters of diversity performance were also tested. These parameters included an average gain of approximately 4 dB, a low ECC of less than 0.01, and good diversity gain of 9.999. The flexible MIMO antenna performs well in bending and on-body conditions. To sum up, the antenna has good prospects in IoT applications and wearable fields.

Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP-based bioelectronic device, however, still necessitates a low form factor packaging solution to protect the electronics in the body. In this work, we investigate two promising encapsulation coatings based on thin-film technology as the main packaging for LCP-based electronics. Specifically, a HfO2–based nanolaminate ceramic (TFE1) deposited via atomic layer deposition (ALD), and a hybrid Parylene C-ALD multilayer stack (TFE2), both with a silicone finish, were investigated and compared to a reference LCP coating. T-peel, water-vapour transmission rate (WVTR) and long-term electrochemical impedance spectrometry (EIS) tests were performed to evaluate adhesion, barrier properties and overall encapsulation performance of the coatings. Both TFE materials showed stable impedance characteristics while submerged in 60 °C saline, with TFE1-silicone lasting more than 16 months under a continuous 14V DC bias (experiment is ongoing). The results presented in this work show that WVTR is not the main factor in determining lifetime, but the adhesion of the coating to the substrate materials plays a key role in maintaining a stable interface and thus longer lifetimes.

The design of microstrip patch (MP) antenna using Moth–Flame optimization (MFO) algorithm for UWB applications is presented in this article. MP antennas are designed to operate in dual and multi-band application as it possess the following advantages such as low cost, light weight and easy installation. To reduce the microstrip patch cross-polarized radiation and to attain the essential radiation parameters, the MP antenna is designed with a defected ground structure. The substrate of liquid crystal polymer is used here to reduce the material cost and the applicable geometry parameters are used to improve antenna performance. The MFO optimized antenna represents 50 mm × 50 mm compact size, which improves the performance of antenna. However, the simulation procedure is done by the MATLAB tool along with high frequency structure simulator for parameter optimization and performance analysis respectively. The operational bandwidth of the antenna is 3.1 GHz and the return loss is − 20 dB that covers the UWB (3.1–10.6 GHz) applications. The simulation outcomes exhibit good impedance bandwidth, radiation pattern, directivity, and relatively constant gain over the entire band of frequency comparing with the earlier methods. Finally, the proposed system can be a better option for the design of microstrip antenna in the communication system, to cover Bluetooth operations, Wi-Fi, Wi-MAX, Telemedicine and UWB applications. [ABSTRACT FROM AUTHOR]

In this work, a metamaterial loaded circularly polarized (CP) flexible CPW fed antenna is presented. The flexible behavior of the antenna is analyzed and tested at various bending angles. The overall dimension of the liquid crystal polymer (LCP) antenna is 0.44 λ0 × 0.37 λ0, which is having thickness of 0.1 mm. The planar LCP antenna works at WiMAX (3.5 GHz), WLAN (5.8 GHz), and at vehicular communication band (5.9 GHz). Using metamaterial exhibiting split ring resonators and CSRR placement on the either side of the feedline and ground, we obtained circular polarization. Both planar and bending antenna cases are analyzed and results such as axial ratio, reflection coefficient, and radiation patterns with respect to planar and bending angles are validated with measurement results. [ABSTRACT FROM AUTHOR]

In this article, the co-design of novel self-packaged balanced bandpass filters (BPFs) integrated with the functionality of impedance transformation is presented for the first time. The proposed design is based on a modified branch-line structure, which is composed of two different branch lines and two identical coupled-line sections. Analysis results show that the considered filters can not only achieve Chebyshev equal-ripple responses with impedance transformation properties for the differential mode (DM) but also can efficiently improve the bandwidth of the common-mode (CM) rejection with resorting to this modified branch-line structure. Furthermore, according to the specified equal-ripple fractional bandwidth (FBW), in-band return loss (RL) level, and impedance transformation ratio ${m}$ , the DM frequency response can be directly determined. Two design prototypes, the second-order balanced BPF with a 50–75- $\Omega $ ($m= 1.5$) impedance transformation and the third-order one with a 50–200- $\Omega $ ($m= 4$) impedance transformation, are implemented in self-packaged forms by using the multilayer liquid crystal polymer (LCP)-bonded printed circuit board (PCB) technology. Theoretical, simulated, and measured results are recorded in good agreement, well verifying the design concept. [ABSTRACT FROM AUTHOR]

This letter presents the design, fabrication, and performance evaluation of a flexible millimeter-wave (mm-wave) antenna array for the fifth generation (5G) wireless networks operating at Ka-band (26.5–40 GHz). The single element antenna is comprised of a coplanar-waveguide-fed rectangular patch tapered at its sides with two vertically oriented slots. The ground is designed with L-shaped stubs to converge the dispersed radiation pattern for improving the directivity and gain. The antenna fabrication is accomplished by two advanced methods of laser-milling and inkjet printing on a thin film of flexible liquid crystal polymer. A novel and time-efficient method for postprinting sintering is also proposed in this letter. The design is extended in a two-element array for the gain enhancement. Measurements have validated that the proposed antenna array exhibits a bandwidth of 26–40 GHz with a peak gain of 11.35 dBi at 35 GHz, and consistent high gain profile of above 9 dBi in the complete Ka-band. These features recommend the proposed antenna array as an efficient solution for integration in future flexible 5G front ends and mm-wave wearable devices. [ABSTRACT FROM AUTHOR]

Abstract In the present work, low profile proximity feed multiband patch antenna array have been investigated and presented. The proposed antenna is array of five similar split ring resonator (SRR) structures patch that are mounted on the upper layer of the liquid crystal polymer substrate and photonic band gape (PBG) structures are created in the underneath substrate to improve the performance of radiation characteristics. SRR characteristic has been matched with resonance frequencies of designed antenna and observed multi-band resonances below −14 dB at 0.58 THz, 0.61 THz, 0.64 THz, 0.67 THz, 0.74 THz, 0.77 THz, 0.800 THz, 0.84 THz, 0.86 THz and 0.89 THz. The proposed antenna is mounted on Liquid crystal polymer (LCP) substrate having dielectric constant of 2.9 and loss tangent of 0.00025. Out of ten multiband frequencies, we obtained peak gain, directivity and efficiency are 14.6 dB, 15.32 dBi and 85.4% respectively, at the corresponding resonance frequency of 0.74 THz with minimum return loss of −50.942. The achieved fractional bandwidth and performance of designed antenna are suitable for security, Video rate imaging, homeland, medical and material characterization application in the THz spectrum. [ABSTRACT FROM AUTHOR]

We studied the eutectic behaviour in binary miscible blends of a rigid and two semi-flexible Liquid Crystal Polymers (LCP) model systems for self and thermoplastic reinforcement. At the eutectic point of the studied LCP-LCP blends, the systems showed suppressed crystal-nematic temperatures and wider nematic range with lower process temperature than the single LCP components. This approach broadens the application of LCPs as high-performance polymers, as well as in reinforcement of engineering plastics. The eutectic points of LCP blends could be a blueprint for development of varieties of multi-component LCP materials. [ABSTRACT FROM AUTHOR]

A double band-notched UWB compact antenna based on ultrathin liquid crystal polymer (LCP) substrate is designed and experimented for flexible electronics in this paper. The antenna is constituted by swallow tail radiation patch and trapezoid ground. Two elliptic single complementary split-ring resonators (ESCSRRs) are used to realize double band-notched characteristic in UWB band. The measurement results show that the VSWRs of antennas are lower than 2 in the whole UWB band (3.1 GHz-10.6 GHz) except the two band-notched frequency-bands in 3.7 GHz-4.2 GHz and 5.15 GHz-5.825 GHz. The bending performance of band-notched UWB antenna are measured. The measured radiation patterns indicate that the antenna is an omni-directional antenna both at flat and bent circumstances. The overall dimension of the antenna is 27 mm × 21 mm × 0.05 mm. These results suggest that this compact mechanical flexible antenna would be useful for flexible UWB wireless system. [ABSTRACT FROM AUTHOR]

This communication presents a novel cactus-shaped ultrawideband (UWB) monopole antenna fabricated on liquid crystal polymer (LCP). The proposed antenna is a very compact design, since it can be fabricated on a board with dimensions only $20\times28$ mm ^{2} , while the three linear segments that comprise the cactus-shaped monopole provide a direct control on antenna matching. The proposed antenna is operating from 2.85 to 11.85 GHz and it presents very consistent omnidirectional patterns throughout the UWB frequency range. Return loss and pattern measurements are presented and the operation principles are discussed in detail. The simplicity of this topology, with the easily controllable return loss, allows for its easy implementation for various UWB subband designs, just by building suitable monopole versions, for which the only difference is the length of the three linear segments. [ABSTRACT FROM AUTHOR]

Background Ideally, neural probes should have channels with a three-dimensional (3-D) configuration to record the activities of 3-D neural circuits. Many types of 3-D neural probes have been developed; however, most of them were designed as an array of multiple shanks with electrodes located along one side of the shanks. New method We developed a novel liquid crystal polymer (LCP)-based neural probe with four-sided electrodes. This probe has electrodes on four sides of the shank, i.e. , the front, back and two sidewalls. To generate the proposed configuration of the electrodes, we used a thermal lamination process involving LCP films and laser micromachining. Results The proposed novel four-sided neural probe, was used to successfully perform in vivo multichannel neural recording in the mouse primary somatosensory cortex. Comparison with existing method The multichannel neural recording showed that the proposed four-sided neural probe can record spiking activities from a more diverse neuronal population than single-sided probes. This was confirmed by a pairwise Pearson correlation coefficient (Pearson’s r) analysis and a cross-correlation analysis. Conclusion The developed four-sided neural probe can be used to record various signals from a complex neural network. [ABSTRACT FROM AUTHOR]

In this paper, a gallium nitride (GaN)-based power amplifier (PA) is cooled and tuned thanks to multifunctional hybrid microfluidic channels integrated on a multilayer organic substrate composed of liquid crystal polymer and ceramic-filled polytetrafluoroethylene. The tuning microchannels are integrated in the organic materials, while the cooling microchannels are micromachined in a copper carrier. The tuning allows the PA to switch the frequency of operation from 2.4 to 5.8 GHz and vice versa. Heat removal is achieved by the motion of distilled water below the GaN die, while tuning is achieved by swapping air and acetone inside the source and load matching network microchannels. The novel idea behind the design of such tunable PAs relies on the design of microfluidically tunable matching networks. For the first time, tunability parameters are introduced and a generic methodology is described for the design of microfluidically tunable matching networks for any dies, frequencies, fluids, or stackups. The measured power added efficiency (PAE) and output power ( $P_{{\mathrm {out}}}$ ) are: 1) PAE = 33.9% and $P_{{\mathrm {out}}} = 37.1$ dBm at 2.4 GHz with acetone and 2) PAE = 51.1% and $P_{{\mathrm {out}}} = 37.9$ dBm at 5.8 GHz with air. The liquid cooling seems to have no effect on $P_{{\mathrm {out}}}$ for all measurements but shows a 1.5% increase in PAE for the 5.8-GHz measurements. [ABSTRACT FROM PUBLISHER]

This paper studies on the RF MEMS switch based on flexible liquid crystal polymer (LCP) substrate and the influence of the LCP substrate bending characteristics on mechanical properties of the switch. Due to the excellent properties of flexible LCP materials, RF MEMS devices based on LCP substrates will be very suitable for microwave systems with high space requirements and wearable devices. Obviously, the deformation of flexible substrate will affect the performance of RF MEMS switch. Therefore, this paper proposes a modeling of the substrate bending to analyze it. The experimental results of the fabricated switches show that the pull-in voltage of the switch is $\sim 22$ V, the insertion loss is better than −0.6 dB, the isolation is better than −15 dB, and the return loss is better than −18 dB up to 20 GHz. According to the experiments, we can find that when the curvature of the substrate is increased from zero to 22.2 (1/m), then the measured pull-in voltage is increased from 22.1 to 23.9 V and when the curvature of the substrate is increased from 22.2 to 44.2 (1/m), then the measured pull-in voltage is decreased from 23.9 to 18.9 V. In conclusion, with the increase of substrate curvature, the switch pull-in voltage will increase at first and then decrease. The experimental results are in good agreement with the modeling. [ABSTRACT FROM AUTHOR]

Coupling between closely spaced wideband analog radio frequency integrated circuits can cause degradation in device performance. Methods for reducing the coupling between packages were tested, with a strong focus on maintaining manufacturability and minimizing any increase in coupling between structures within the package. Methods include the application of magnetic absorbing material or resistive sheets to the package surface and the inclusion of conductive vias in the package walls. Package modifications were tested from 5–40 GHz through both full-wave simulation and physical measurement. The best tradeoff in performance and manufacturability below 20 GHz was found using 250-Ω/sq. resistive sheets connected to the return plane with vias in the package corners, while above 20 GHz, the best tradeoff was found by covering the package with magnetic absorbing materials. The magnetic absorbing material can be embedded directly in the package polymer itself, allowing easy manufacture. [ABSTRACT FROM AUTHOR]

Polymers are increasingly being used in implantable biomedical applications owing to their flexibility and compatibility with micro-fabrication processes. A liquid crystal polymer (LCP) is an inert, highly water-resistant polymer that is suitable for the encapsulation of electronic components and as a substrate material for fabricating neural interfaces. Therefore, the monolithic integration of a neural interface and electronics packaging is enabled by the use of an LCP, which has salient benefits in terms of performance and reliability. For these reasons, LCPs have been studied extensively as a base material for neural prosthetic devices. In this paper, we review recently developed enabling technologies, and demonstrate prototype devices and their performance capabilities. Lifetime estimations and technical challenges of LCP-based neural prosthetic devices are also described. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication of an inkjet-printed multilayer bandpass filter using the liquid crystal polymer (LCP) system-on-package (SOP) technology. The LCP-SOP technology adopted by lamination bonding process reduces the occupied area of a device and is suitable for radio frequency (RF) package applications. The surface morphologies and RF performance of the inkjet-printed silver film on an LCP substrate after the lamination bonding process, which entails applying high temperatures and pressures, were observed and analyzed. Acceptable performance of the inkjet-printed silver film of an optimal lamination bonding condition was 0.69 MPa at 270 °C. Using the inkjet-printing and LCP-SOP technologies, a miniature bandpass filter was created with a minimal S21 value and a maximal S11 value of −1.5 and −17.4 dB at 10.6–14.5-GHz passband, respectively. A strain effect of silver line and bandpass filter was also analyzed. The results demonstrated the effectiveness of the proposed design methodology and the fabrication technique. [ABSTRACT FROM PUBLISHER]

A grid array antenna working around 145 GHz is proposed in this paper. The antenna is built on liquid crystal polymer (LCP) and designed for the $D$ -band antenna-in-package application. The intrinsic softness of the LCP material is a limiting factor of the antenna’s aperture size. A 0.5-mm-thick copper core is used to compensate. By doing this, the rigidness of the antenna is effectively improved, compared with an antenna without the copper core. Wet etching is used to realize the patterns on the top and bottom conductor. Compared with a low-temperature cofired ceramic counterpart, we obtain a considerable cost reduction with acceptable performance. The proposed antenna has an impedance bandwidth of 136–157 GHz, a maximum gain of 14.5 dBi at 146 GHz, and vertical beams in the broadside direction between 141 and 149 GHz. The fabrication procedures of the antennas are introduced, and a parametric study is carried out, which shows the antenna’s robustness against fabrication tolerances, such as the not-well-controlled etching rate and the substrate surface roughness. This makes the antenna a promising solution for mass production. [ABSTRACT FROM AUTHOR]

ABSTRACT Development of high thermally conductive and electrically insulative composites is of interest for electronic packaging industry. Advancements in smaller and more compact electronic devices required improvements in packing materials, including their weight, thermal conductivity, and electrical resistivity. In addition, with the increasing environmental awareness, the usage of green (bio-based) alternatives was equally important. In the present study a hybrid based on fibers of highly concentrated hexagonal boron nitride (hBN) in liquid crystal polymer (LCP) matrix were fabricated. These hybrids were formed by arranging hBN platelets into LCP fiber form to reach high filler concentration and then randomly mix it in polylactide (PLA) matrix. With appropriate filler interaction within the hybrid, thermal conductivity similar to that of pure fiber could be achieved. Filler interaction may be tailored by optimizing the fibers aspect ratio. This study demonstrated the effect of random fillers in fibers shape in increasing the overall thermal conductivity of PLA polymeric hybrid using hBN and LCP fibers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 457-464 [ABSTRACT FROM AUTHOR]

Advances in CMOS and SiGe technologies have made millimeter (mm)-wave multielement arrays with complex architectures, high yields, and good interelement matching feasible. However, the antenna-in-package approach is challenging with a larger number of array elements due to the increase in mm-wave I/O, the need for impedance-controlled via/routing symmetry. In this work, we describe an antenna-IC cointegration approach that relies on aperture coupling between on-chip feed/ground-plane slot and an antenna-on-substrate to simultaneously achieve wide bandwidth and high efficiency. The proposed approach is validated through a 60-GHz packaged prototype in which a 60-GHz quadrupler and aperture-coupled antenna feed fabricated in a 0.18-μm SiGe technology is cointegrated with a 60-GHz patch antenna on a 100-μm liquid crystal polymer substrate. Measured E-plane and H-plane antenna patterns show 0-dB gain at 61 GHz (corresponding to 40% efficiency) and cross-polarization ratio of ~10 dB, demonstrating the feasibility of the proposed approach. [ABSTRACT FROM PUBLISHER]

[Display omitted] • An UV-irradiated chlorine dioxide radical oxidation of LCP substrate is proposed. • This oxidation method chemically modified the LCP substrate surface. • The modified LCP showed increased and long-term interfacial adhesion with metal. • The metal-LCP showed superior metallic conductivity and fatigue resistance. Surface metallization of the liquid crystal polymer (LCP) substrate will play a vital role in a large variety of potential technological applications in the high-frequency and high-speed 5G era. However, the pretreatment of surfaces is a major issue in the polymer metallization process. A facile green and mild surface oxidation method is proposed for the fabrication of flexible, stretchable, compressible, for enhanced metal-LCP interfacial adhesion. The surface oxidation process is accomplished by exposing the LCP substrate to the ultraviolet light-activated chlorine dioxide (ClO 2 ) radical ambiance. The chlorine dioxide radical will chemically alter and modify the LCP substrate surface to promote increased adhesion of the metal and LCP layer during the lamination and electroless plating process. Moreover, flexible metal-LCP substrates are obtained based on the electroless deposition of metal (copper, nickel) on the LCP films. For the case of Cu-LCP substrate, excellent metallic conductivity of 2.6 × 107 S m−1, and excellent fatigue resistance under various deformations are shown. Adhesion strength of the modified LCP was enhanced by increasing the oxidation temperature and time. This work also provides a successful strategy for the pretreatment of other polymer substrates used for the selective metallization with precise patterns. [ABSTRACT FROM AUTHOR]

Thermal management is an important aspect for any packaging technology incorporating high power devices. In this paper, we present an integrated microfluidic cooling solution for high power suiface mount thin film resistors on liquid crystal polymer (LCP) substrate. High power resistors are mounted on top of a 50.8 pm (2 mil) LCP layer, a coolant can circulate, thanks to a micropump, inside a Duroid micromachined channel beneath the LCP layer in order to take away the generated heat. A thermal model is combined from existing thermal models in literature to predict the overall thermal resistance of the organic heat sink in the case of a moving coolant inside the microfluidic channel. Four sets of microfluidic channels with different thicknesses are fabricated and tested. Temperature measurements of resistors with different power ratings and sizes on top of these channels agree with the model predictions and the simulations in the case of static (nonmoving) and dynamic (moving) distilled (Dl) water. With this integrated solution, the case temperature of the 40W resistor, which is mounted on the 254 pm (lOmil) microchannel, can be cooled down to 121°C at room temperature while the resistor is dissipating 23.2 W of power; this resistor fails to operate beyond 13.3 W in the absence of fluid circulation. This is, to the best of our knowledge, the best thermal cooling performance ever achieved on multilayer organic substrates. [ABSTRACT FROM AUTHOR]

The design of a radiation-efficient D-band end-fire on-chip antenna utilizing a localized back-side etching (LBE) technique, as well as an antenna-in-package (AiP) on a low-cost organic substrate, is presented. Quasi-Yagi-Uda antennas are chosen for end-fire radiation because of their compact size. The on-chip antenna is realized in the back-end of the line (BEOL) process of a 130-nm SiGe BiCMOS technology, whereas the in-package antenna is realized in liquid crystal polymer (LCP) technology for comparison. The on-chip antenna design is optimized to meet both process reliability specifications and radiation performance, and corresponding design guidelines are provided. The fabricated on-chip antennas show the state-of-the-art performance with a peak gain of 4.7 dBi, simulated radiation efficiency of 82%, and measured radiation efficiency of 72%–76% using the gain/directivity (G/D) and wheeler-cap methods at 143 GHz. The antenna demonstrates a 3-dB gain bandwidth of more than 30 GHz and 10-dB impedance bandwidth greater than 20 GHz (14% impedance bandwidth). The measurements of the on-package end-fire antenna showed very comparable results with a peak measured gain of 6 dBi and a simulated and measured radiation efficiency of 92% and 86% at 143 GHz. These results demonstrate that highly efficient on-chip end-fire antenna implementation is possible in standard commercially available BiCMOS process. [ABSTRACT FROM PUBLISHER]

A novel retinal prosthetic device was developed using biocompatible liquid crystal polymer (LCP) to address the problems associated with conventional metal- and polymer-based devices: the hermetic metal package is bulky, heavy, and labor-intensive, whereas a thin, flexible, and MEMS-compatible polymer-based system is not durable enough for chronic implantation. Exploiting the advantageous properties of LCP such as a low moisture absorption rate, thermobonding, and thermoforming, we fabricate a small, light-weight, long-term reliable retinal prosthesis that can be conformally attached on the eye-surface. A LCP fabrication process using monolithic integration and conformal deformation was established enabling miniaturization and a batch manufacturing process as well as eliminating the need for feed-through technology. The functionality of the fabricated device was tested through wireless operation in saline solution. Its efficacy and implantation stability were verified through in vivo animal tests by measuring the cortical potential and monitoring implanted dummy devices for more than a year, respectively. [ABSTRACT FROM AUTHOR]

In this study, micro-arc oxidation (MAO) technology was used to coat the surface of pure aluminum disks. Then the liquid crystal polymer (LCP) was used in the mesh method to form a micro-bump structure on the MAO coating. Compared with a single MAO coating, the micro-bump composite coating has a low coefficient of friction, high corrosion resistance, and excellent resistance to frictional corrosion. The microstructure and composition of both coatings were characterized by metallurgical microscopy, SEM, EDS, XRD, and XPS. And the protection mechanism, as well as the physical model of the LCP micro-bump coating, are presented and discussed. In summary, the preparation of micro-bump structures on MAO surfaces using the mesh method provides a feasible improvement idea for the shortcomings of MAO technology. • Micro-bump surface structure prepared by mesh separation method. • The LCP micro-bump structure reduces the wear volume of the friction counterpart. • The composite coating is wear and corrosion resistant. [ABSTRACT FROM AUTHOR]

In this letter, an ultrawideband microstrip line (MSL)-to-MSL transition in multilayer liquid crystal polymer (LCP) substrate is presented for millimeter-wave applications. The proposed transition consists of three circuit layers and three LCP layers. The MSLs’ signal lines are in the top circuit layer, while their grounds are distributed in the inner and bottom layers, respectively, and are connected using through vias. Full-wave simulation reveals an insertion loss of less than 1.1 dB for the proposed transition from dc to 110 GHz. To experimentally demonstrate this design, its back-to-back transition was fabricated and characterized. The measured insertion loss and reflection of the back-to-back transition are less than 2.5 and −13 dB below 110 GHz, respectively, showing a good agreement with the simulated data. [ABSTRACT FROM PUBLISHER]

A compact self-packaged dual-band filter structure using multilayer liquid crystal polymer technology is presented in this paper. The frequency and bandwidth of each passband can be more conveniently controlled by means of vertically embedded elements, i.e., metal patches, placed above the coupled folded multi-stepped impedance resonators. The packaged solution is connected to the outer environment through a coplanar waveguide that allows flip-chip interconnection to a host board. The proposed design is validated with the fabrication of two prototypes. The measured results show good agreement with the simulations. [ABSTRACT FROM AUTHOR]

This paper presents a series-fed two-dipole antenna, fabricated on a liquid crystal polymer (LCP) substrate using inkjet-printing technology. The radio frequency characteristics of inkjet-printing silver film onto an LCP substrate are studied using the microstrip line. The proposed antenna consists of two modified dipole elements of distinct lengths: a modified ground plane and a balun filter yielding a wide bandwidth with bandpass responses. The proposed antenna can be used at frequency band of 26–33 GHz. The bending behaviors of the microstrip line and antenna are also measured. Inkjet printing on LCP substrates provides a low-cost, compact, and flexible packaging solution that can be used in future communication technology. [ABSTRACT FROM AUTHOR]

This paper, for the first time, presents successful integration of a W-band antenna with an organically flip-chip packaged silicon–germanium (SiGe) low-noise amplifier (LNA). The successful integration requires an optimized flip-chip interconnect. The interconnect performance was optimized by modeling and characterizing the flip-chip transition on a low-loss liquid crystal polymer organic substrate. When the loss of coplanar waveguide (CPW) lines is included, an insertion loss of 0.6 dB per flip-chip-interconnect is measured. If the loss of CPW lines is de-embedded, 0.25 dB of insertion loss is observed. This kind of low-loss flip-chip interconnect is essential for good performance of W-band modules. The module, which we present in this paper, consists of an end-fire Yagi–Uda antenna integrated with an SiGe BiCMOS LNA. The module is 3 mm \times 1.9 mm and consumes only 19.2 mW of dc power. We present passive and active E- and H-plane radiation pattern measurements at 87, 90, and 94 GHz. Passive and active antennas both showed a 10-dB bandwidth of 10 GHz. The peak gain of passive and active antennas was 5.2 dBi at 90 GHz and 21.2 dBi at 93 GHz, respectively. The measurements match well with the simulated results. [ABSTRACT FROM PUBLISHER]