Electrically Tunable Open-Stub Bandpass Filters Based on Nematic Liquid Crystals

Economou, Evangelos; Lovejoy, James; Harward, Ian; Nobles, Jason E.; Kula, Przemysław; Herman, Jakub; Glushchenko, Anatoliy; Celinski, Zbigniew

doi:10.1103/physrevapplied.8.064012

Cited by 15 publications

(10 citation statements)

References 22 publications

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“…Investigations of the transient behavior of this loaded-line phase shifter in MEMS technology is shown in Figure 29, where the rise and decay of the measured differential phase shift with respect to its maximum 8 for hLC in between 4.5 and 5 µm. Based on measurements of the reflection-type phase shifter with an MEMS switch at the end, the rise time and decay time were modeled in [268] 96 , respectively. The last one reveals 0.33 ms and 26.64 ms for the 90% and 10% values, respectively.…”

Section: Bottom Substratementioning

confidence: 99%

“…With the emergence and progress of newly developed LC mixtures specifically synthesized for microwaves since 2002 [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60], innovative concepts and designs with appropriate biasing schemes enabled numerous high-performance MLC components and devices in the RF domain, which fully exploit the microwave LC's unique properties: various planar delay line, metallic and dielectric waveguide phase shifters at different frequencies [45][46][47], tunable resonators and filters [85][86][87][88][89][90][91][92][93][94][95][96][97][98][99], tunable power dividers and RF switches [80,[99][100][101][102][103][104], tunable metamaterial structures, frequency-selective and high-impedance surfaces [105][106][107][108][...…”

Section: Introductionmentioning

confidence: 99%

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Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

Jakoby

Gaebler²,

Weickhmann³

2020

Crystals

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Future satellite platforms and 5G millimeter wave systems require Electronically Steerable Antennas (ESAs), which can be enabled by Microwave Liquid Crystal (MLC) technology. This paper reviews some fundamentals and the progress of microwave LCs concerning its performance metric, and it also reviews the MLC technology to deploy phase shifters in different topologies, starting from well-known toward innovative concepts with the newest results. Two of these phase shifter topologies are dedicated for implementation in array antennas: (1) wideband, high-performance metallic waveguide phase shifters to plug into a waveguide horn array for a relay satellite in geostationary orbit to track low Earth orbit satellites with maximum phase change rates of 5.1°/s to 45.4°/s, depending on the applied voltages, and (2) low-profile planar delay-line phase shifter stacks with very thin integrated MLC varactors for fast tuning, which are assembled into a multi-stack, flat-panel, beam-steering phased array, being able to scan the beam from −60° to +60° in about 10 ms. The loaded-line phase shifters have an insertion loss of about 3 dB at 30 GHz for a 400° differential phase shift and a figure-of-merit (FoM) > 120°/dB over a bandwidth of about 2.5 GHz. The critical switch-off response time to change the orientation of the microwave LCs from parallel to perpendicular with respect to the RF field (worst case), which corresponds to the time for 90 to 10% decay in the differential phase shift, is in the range of 30 ms for a LC layer height of about 4 µm. These MLC phase shifter stacks are fabricated in a standard Liquid Crystal Display (LCD) process for manufacturing low-cost large-scale ESAs, featuring single- and multiple-beam steering with very low power consumption, high linearity, and high power-handling capability. With a modular concept and hybrid analog/digital architecture, these smart antennas are flexible in size to meet the specific requirements for operating in satellite ground and user terminals, but also in 5G mm-wave systems.

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Section: Bottom Substratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

Jakoby

Gaebler²,

Weickhmann³

2020

Crystals

View full text Add to dashboard Cite

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“…The transition also contains cutouts on the CPW ground planes and the microstrip groundplane (outlined in green) to match impedance across the LC boundary. This arrangement was based on similar designs reported in other publications [26,27].…”

Section: Phased Array Antenna Assembly Design and Constructionmentioning

confidence: 97%

Eight-element liquid crystal based 32 GHz phased array antenna with improved time response

et al. 2021

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Phased array radar systems are used for a wide variety of applications including the precise tracking of airborne craft for air traffic control and providing accurate atmospheric condition information important in weather forecasting. Reducing the cost and size of these radar systems will open new fields to the use of this technology. Using phase control implemented through liquid crystal materials we have created a compact, phased array radar system operating in the microwave range. We report on the construction and testing of a linear, eight element phased array antenna system operating at 32 GHz with element phase controlled by a dual frequency nematic liquid crystal media used as a tunable dielectric. The system was designed using CST Design Studios and Ansys HFSS software. Dual frequency liquid crystals are used to improve beam steering response times. We demonstrate 42 millisecond beam switching times, defined as the time to change the beam focus from one point to another point, controllable beam formation, and beam steering profiles consistent with analytical results and simulation models. The device footprint is a square with sides 9.5 cm long and a thickness less than 2.5 mm. Such a module is easily stackable to create an 8 × 8 phased array system. Our design incorporates a modular construction using PCB for the antennas and input circuitry and a liquid crystal phase control cell with microwave glass substrates. This design simplifies design, construction, and testing as compared to on-glass designs. The device shows an improvement in point-to-point scanning speeds by a factor of 3 as compared to similar liquid crystal based devices and provides continuously variable tuning. Such a device can be used in a system for reduced visibility, directional range finding suitable for automobile collision avoidance systems and rotary wing aircraft landing aids.

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“…For filter with larger FBW, e.g. [46] and [47], larger tunability of the center frequency can be obtained. Although this work consists of a filter with tunable coupling resonators, the insertion loss is lower as other narrowband filter e.g.…”

Section: Fabrication and Characterizationmentioning

confidence: 99%

Bandwidth and Center Frequency Reconfigurable Waveguide Filter Based on Liquid Crystal Technology

Kamrath¹,

Polat²,

Matic³

et al. 2022

IEEE J. Microw.

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This paper presents for the first time a fully electronically reconfigurable waveguide filter tunable in bandwidth and center frequency based on liquid crystal (LC) technology. A continuously reconfigurable two pole bandpass filter is designed and characterized in the Ka-band at 30 GHz. To be able to tune both center frequency and bandwidth independently, the resonators and coupling structures are filled with LC as tunable material. Hence, the filter's center frequency and coupling strengths can be tuned and, furthermore, tuning with constant filter characteristic is possible. To tune the LC, a novel two-layer electrode design for waveguide structures is presented, which is simple to integrate and provides a high tuning efficiency with low insertion loss. By applying different bias configurations, the LC's effective permittivity can be varied, and therefore, also the resonators' electrical lengths. The presented two pole filter can adapt its center frequency from 29.8 GHz to 30.7 GHz with a maximum 3 dB bandwidth variation from 660 MHz to 870 MHz. The measurements are carried out with bias voltages up to ±250 V.INDEX TERMS Microwave filter, liquid crystals, millimeter wave communication, tunable circuits and devices, K-band.This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

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Electrically Tunable Open-Stub Bandpass Filters Based on Nematic Liquid Crystals

Cited by 15 publications

References 22 publications

Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

Eight-element liquid crystal based 32 GHz phased array antenna with improved time response

Bandwidth and Center Frequency Reconfigurable Waveguide Filter Based on Liquid Crystal Technology

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