Organic Liquid Crystal Polymer Research Articles

Reduction of solar infrared heating by using highly transparent thin films based on organic chiral nematic liquid crystal polymer.

This paper demonstrates a thin and transparent reflector film for the near infrared, based on chiral nematic liquid crystal (CLC) polymers. Two films reflect almost 50% of unpolarized incident light from 730 to 820 nm and from 880 to 1030 nm, while remaining completely transparent in the visible region with transmittance >90%. An efficient window uses the combination of two reflectors. After exposing two window-cubes for 2 h to direct sunlight, the temperature inside the cube with reflector windows was 4°C lower than in cube with plain windows. This reveals that the infrared (IR) reflectors can effectively control the indoor temperature. These films, which are 8 µm in thickness, can be detached from the glass substrates and used as a free-standing film, or be attached to a flexible optical foil or a solid window. The foils can be applied in buildings, offices, and automobiles to statically reduce the energy consumption required for air conditioning or lighting. The free-standing foils show acceptable resistance to polar protic solvents and are thermally stable up to 100°C.

Bio-inspired spectropolarimetric sensor based on tandem organic photodetectors and multi-twist liquid crystals

Simultaneous spectral and polarimetric imaging enables versatile detection and multimodal characterization of targets of interest. Current architectures incorporate a 2×2 pixel arrangement to acquire the full linear polarimetric information causing spatial sampling artifacts. Additionally, they suffer from limited spectral selectivity and high color crosstalk. Here, we demonstrate a bio-inspired spectral and polarization sensor structure based on integrating semitransparent polarization-sensitive organic photovoltaics (P-OPVs) and liquid crystal polymer (LCP) retarders in a tandem configuration. Color tuning is realized by leveraging the dynamic chromatic retardation control of LCP films, while polarization sensitivity is realized by exploiting the flexible anisotropic properties of P-OPVs. The structure is marked by its ultra-thin design and its ability to detect spectral and polarimetric contents along the same optical axis, thereby overcoming the inherent limitations associated with conventional division-of-focal plane sensors.

Effect of varying the composition and nanostructure of organic carbonate-containing lyotropic liquid crystal polymer electrolytes on their ionic conductivity

Nanostructured composite electrolyte films consisting of a cross-linked lyotropic liquid crystal (LLC) monomer, an organic carbonate liquid electrolyte (propylene carbonate, dimethylcarbonate, diethylcarbonate) and a Li salt (LiClO_4, LiBF_4, LiPF_6) were systematically prepared and characterized at two electrolyte concentrations (0.245 and 1.0 m) and four liquid loading levels (5, 15, 30, 50 wt %). The LLC morphology of the films was investigated using polarized light microscopy and powder X-ray diffraction; their ionic conductivity was investigated using AC impedance measurements. Higher liquid electrolyte loadings and Li salt concentrations generally increased ionic conductivity, regardless of the liquid electrolyte or salt used. Some mixed-phase LLC morphologies displayed good ionic conductivity; however, as initially prepared, these formulations were at the limit of liquid uptake. In contrast, composites with a type II bicontinuous cubic (QII) LLC phase containing ordered, three-dimensional interconnected nanopores exhibited good conductivity using much less liquid electrolyte and a lower Li salt concentration, indicating that this structure is more amenable to ion transport than less ordered/uniform morphologies. When wetted with electrolyte solution and integrated into Li/fluorinated carbon coin cells, the QII films were sufficiently strong to act as an ion-conductive separator and displayed stable open-circuit potentials. Many of the mixed-phase films gave shorted cells.

Common‐mode suppression for balanced bandpass filters in multilayer liquid crystal polymer technology

A new multilayer differential transmission line for common-mode suppression fabricated using an organic liquid crystal polymer multilayer substrate is proposed and analysed. The structure consists of a pair of parallel strip lines printed on the top layer of the substrate that are capacitively coupled to conductor patches periodically etched in an intermediate interface. These patches are symmetrically connected to a solid ground plane by means of short-circuited high-impedance microstrip line sections and metalised via holes. The differential signal supported by the coupled strips is not significantly affected by the presence of the middle layer layout, whereas the common-mode signal propagation is strongly suppressed within a certain frequency band. When this structure is cascaded with a simple differential bandpass filter exhibiting poor common mode rejection, a good common mode response is achieved within the unperturbed differential passband. The measurements confirm a significant enhancement of common-mode rejection thanks to the use of the proposed differential lines.

Design of Ka Band Patch Microstrip Antenna Array on LCP Substrate

This paper presents a 35 GHz patch microstrip antenna array on an organic LCP (Liquid Crystal Polymer) substrate. To achieve a higher gain and narrower 3 dB beamwidth, a 4×4 antenna array has been designed and simulated using a 2×2 antenna array as unit array. The results show that an 18.9 dBi of gain and a 3 dB beamwidth of 20.7degrees.

A 60-GHz Active Receiving Switched-Beam Antenna Array With Integrated Butler Matrix and GaAs Amplifiers

This paper presents for the first time a 60-GHz receiving switched-beam antenna on organic liquid crystal polymer (LCP) platform. A 4 × 1 quasi-Yagi array is incorporated with a 4 × 4 Butler matrix beamforming network and GaAs low-noise amplifiers on an LCP substrate. The active beam is controlled by GaAs single-pole-double-throw switches to access the four output states of the Butler matrix. The entire 4 × 1 active array is 1.4 cm × 1.75 cm and consumes 1.1 W of dc power. Successful comparisons of the measured and simulated results verify a working phased array with a return loss better than 10 dB across the frequency band of 56.7-63.7 GHz. A comparison of radiation patterns demonstrate beam steering of ±40° with a peak active gain of 27.5 dB. The combined antenna and receiver noise performance at 60 GHz exhibits an estimated merit G/T of -18.6 dB/K and noise figure of 5.4 dB.

Multilayer Integration of Low-Cost 60-GHz Front-End Transceiver on Organic LCP

This letter presents a low-cost and lightweight transceiver with RF front-end components integrated on multilayer organic liquid crystal polymer (LCP) substrate for 60-GHz wireless communication applications. Two embedded dual-mode filters with an insertion loss of 3.1 and 2.4 dB are included, while they are designed to improve the isolation between the transmitting and receiving modes. A package-integrated high-gain vertical dipole is used for the radiating element with orthogonal polarization between the transmitting and receiving modes. The transceiver module after integrating a power amplifier (PA) and a low noise amplifier (LNA) for each mode has a measured gain of 12 dBi for the transmitting mode at 61.5 GHz and 22 dBi for the receiving mode at 66 GHz.

Integrated Wideband 2-D and 3-D Transitions for Millimeter-Wave RF Front-Ends

This letter reports on broadband 3-D and 2-D transitions on flexible organic liquid crystal polymer (LCP) substrate with return loss below 15 dB for frequencies up to 110 GHz. The presented novel 3-D coplanar waveguide-coplanar waveguide-microstrip (CPW-CPW-MSTRIP) transition features an insertion loss (IL) of 0.45 dB for a 3.3-mm total (longitudinal) length of transition, while the novel 3-D CPW-CPW transition has an IL of 0.25 dB for a 2.8-mm (longitudinal) length of transition. These transitions require strategically placed vias and tapering of the CPW ground planes in order to suppress radiation loss and optimize the performance over a very broad frequency range. This letter also includes a 90° CPW bend that shows a return loss lower than 15 dB up to 100 GHz and an insertion loss of 0.75 dB for a 6.35-mm total length of the transition. All these transitions are simple to realize and are compatible with low-cost substrate fabrication guidelines allowing for the easy integration of ICs in 3-D modules, especially in compact automotive radar applications and beam-steering wideband antenna arrays. An example of the integration of the proposed 3-D transitions with a practical antenna array is presented, and experiments verify the very good performance of the integrated topology up to 100 GHz.

Compact Wide Stopband Ultra Wideband Bandpass Filter Using Multilayer Liquid Crystal Polymer Technology

Novel ultra-wideband (UWB) bandpass filters (BPFs) are proposed based on broadside coupled capacitive-loaded transmission line resonators (C-L TLR) in this letter. By utilizing the wideband harmonic suppression behavior of C-L TLR, the proposed UWB BPFs were designed with wide stopband and implemented using multilayer organic liquid crystal polymer (LCP) technology. As demonstrations, a vialess five-pole BPF was designed first, and then by adopting shunt short-circuited microstrip stubs at input/output ports, a compact UWB BPF was designed to meet FCC-defined UWB indoor mask. The proposed UWB BPFs were fabricated using multilayer LCP technology. Good agreements between simulated and measured results of fabricated filters were observed. The measured results show that the fabricated BPFs have good selectivity, wide stopband and high rejection level. The fabricated UWB BPFs have compact sizes of 15.15 mm by 4.7 mm about 0.55 lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> by 0.17 lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> and 9.6 mm by 9.2 mm about 0.35 lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> by 0.33 lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> respectively, where lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g0</sub> is the guided wavelength of 50 Omega microstrip line at 6.85 GHz. They are attractive for UWB communications and radar systems.

Compact ultra-wideband bandpass filter using broadside coupled hairpin structures on multilayer liquid crystal polymer substrate

A novel ultra-wideband (UWB) bandpass filter (BPF) using a broadside-coupled hairpin structure and multilayer organic liquid crystal polymer (LCP) technology is presented. To suppress stopband harmonic response, folded stepped impedance structures were adopted as hairpin resonators in the design. The proposed filter has been investigated numerically and experimentally. Multilayer LCP technology was used to implement designed UWB BPF. Good agreement between simulated and measured results of the proposed filter was observed. They show that the fabricated UWB BPF has a good performance, including a small insertion loss, a flat group delay with a variation within 0.1 ns in most of its passband, a wide stopband from 11.0 20.0 GHz with a high rejection level up to 20.0 dB, and a very compact size of 9.8 times 7.5 mm (0.36 lambdag times 0.27 lambdag, where lambdag is the guided wavelength of 50 Omega microstrip line at 6.85 GHz).

Low Cost 60 GHz Gb/s Radio Development

The recent advances of CMOS and SiGe process technologies have now made the design of lowcost highly integrated millimeter-wave radios possible in Silicon. In combination with an optimum organic Liquid Crystal Polymer packaging approach, this represents a unique opportunity to develop Gb/s radio that could address the increasing demand in term of data rate throughput of the emerging broadband wireless communication systems. In this paper we discuss the circuit and module challenges that will enable a successful deployment of 60GHz gigabits wireless systems.