Multilayer Liquid Crystal Polymer Research Articles

Broadband directional filter in multilayer liquid crystal polymer films at W-band

In this work, a four-port directional filter (DF) with a broad passband and low reflection is proposed at the W-band, which comprises three unit filters at 92, 95, and 97 GHz, cascaded in series. Each unit consists of two microstrip lines in the top circuit layer for signal input and output, two pairs of apertures in the middle ground layer for directional coupling, and one square loop in the bottom layer as a selective resonator. By sweeping the working frequencies of the three units and optimizing the phase delays between them, the proposed filter achieves a 3-dB bandwidth as broad as 16%, an insertion loss of 2.5 dB at 95 GHz, and an out-of-band rejection of −28 and −23 dB at 80 and 110 GHz, respectively. The corresponding reflection attenuation is larger than 9.6 dB from 60 to 105 GHz. To verify our design, a prototype is fabricated and characterized, and its experimental data are consistent with the simulation. This work significantly expands the bandwidth of DFs and may find many applications in frequency division multiplexing and high-gain wireless systems.

A Fully Packaged Wideband Bandpass Power Divider Based on Four-Port Common-Mode Network

This brief describes a generalized method to realize an in-phase power splitter based on a four-port common-mode network (CMN). By enforcing one of the four ports open-or short-circuited, a three-port network with in-phase property and equal power division at two output ports is presented. A specific CMN consisting of two identical coupled-line sections is discussed and applied to the design of a wideband power divider with bandpass frequency response. The converted circuit can not only achieve the function of equal power splitting, but also flexibly allows for the control of equal-ripple bandwidth and in-band return loss (RL) level. Furthermore, the reflection coefficients and isolation of two output ports could be ideally enhanced by installing the synthesized lumped resistors. To confirm the design concept, a fully packaged wideband power divider working at 2.0 GHz with the fractional bandwidth (FBW) of 105% has been designed and fabricated using multilayer liquid crystal polymer (LCP) circuit technology. Final measured results, well agreeing with the simulated ones, exhibit wideband bandpass response, high port-to-port isolation, and port matching condition, as well as good in-band magnitude and phase difference.

Compact Integrated Lumped-Element Bandpass Filter Loaded with Defected Ground Structure Based on Multilayer Liquid Crystal Polymer Substrate

Compact Integrated Lumped-Element Bandpass Filter Loaded with Defected Ground Structure Based on Multilayer Liquid Crystal Polymer Substrate

Stopband enhanced patch‐type filter using common‐mode feeding method based on multilayer liquid crystal polymer lamination technology

AbstractIn this study, a new common‐mode feeding approach to the 2‐D square patch resonator is proposed and applied in the design of bandpass filter (BPF) with wideband harmonic suppression. Different from the conventional single‐point feeding structure, the proposed one has two physical feeding points on the patch. It is indicated from the electric field distributions that the presented feeding method can not only support the excitation of the desired fundamental TM01 mode, but also enable the rejection of high‐order modes by selecting proper feeding positions. For demonstration, a second‐order BPF centred at 4.0 GHz with wide stopband suppression has been implemented by using multilayer liquid crystal polymer circuit technology. Moreover, benefitting from mixed‐coupling, a transmission zero is introduced to improve the filtering selectivity. Measured and simulated results are in good agreement with each other, validating the proposed feeding concept.

Frequency Division Multiplexer With Directional Filters in Multilayer LCP Films at - and -Band

A quasi-reflectionless frequency division multiplexer (FDM) with directional filters (DFs) in multilayer liquid crystal polymer (LCP) substrates is proposed for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -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.

A Fully Packaged Bandpass Filter on Stripline Patch Resonator With Wide Upper Stopband

In this letter, a fully packaged dual-mode bandpass filter (BPF) with wide upper stopband is presented. The stripline patch resonator loaded by the shorting slabs is adopted to achieve the dual-mode bandpass performance under operation of TM00 mode and TM01 mode. To remove other harmonic resonances of the stripline patch resonator, a common-mode double-point inset-feeding technique is proposed at the very beginning to prevent the excitation of high-order modes. To verify the design concept, a prototype packaged dual-mode BPF working at 4.0 GHz with the fractional bandwidth (FBW) of 8.2% is designed and fabricated using the multilayer liquid crystal polymer (LCP) circuit technology. Final results theoretically demonstrate and experimentally confirm that a wide stopband rejection up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.3f_{0}$ </tex-math></inline-formula> is obtained, well verifying the feeding method.

Self-Packaged Balanced Bandpass Filters With Impedance Transformation Characteristic

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.

Novel stacked‐defected ground structures for ultra‐wideband low loss balun designs

AbstractA novel stacked‐defected ground structure (SDGS) for ultra‐wideband and low‐loss balun design was developed. The balun implements an inductive compensation method on a multilayer liquid crystal polymer (LCP) substrate to control phase and amplitude imbalances. Based on a 15‐dB input return loss and 0.5 dB insertion loss criterions, the balun has a measured bandwidth from 70 MHz to more than 2.1 GHz, a measured amplitude and phase imbalances are less than 0.5 dB and 5°, respectively. With a compact size of 36 mm × 51 mm × 0.23 mm, the 0.5 dB loss‐balun achieves both the largest bandwidth ratio (30:1 ratio) and the most improved imbalances reported to date on a printed circuit board.

Packaging of High-Gain Multichip Module in Multilayer LCP Substrates at $W$ -Band

In this paper, we packaged a multichip module (MCM) in multilayer liquid crystal polymer (LCP) substrate using V-shaped wire bond and 3-D-printed housing. In the proposed module, two low-noise amplifiers (LNAs) are cascaded in series to obtain high gain and low noise figure, and multilayer circuit is designed to achieve high assembly density. To minimize mode mismatch between microstrip lines on LNA and LCP with low dielectric constant, V-shaped wire bond was designed for LNA integration, achieving low insertion loss and low reflection at $W$ -band. To verify this bonding design experimentally, a single-chip module was first integrated and characterized, successfully achieving a gain of more than 26.5 dB from 80 to 100 GHz. Then, the MCM was investigated and packaged, in which substrate integrated waveguides and via barriers are introduced to eliminate the potential substrate modes, and 3-D-printed plastic housing coated with gold is designed to capsulate the LNAs and isolate them in free space. The measured data demonstrate a high gain of 50 dB, a low noise figure of less than 6 dB, and linear phase from 80 to 97 GHz.

Ultra-Wideband Microstrip Line-to-Microstrip Line Transition in Multilayer LCP Substrate at Millimeter-Wave Frequencies

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.

Broadband SIW-to-Waveguide Transition in Multilayer LCP Substrates at W-Band

In this letter, we present a substrate-integrated waveguide (SIW) to air-filled rectangular waveguide (WG) transition in multilayer liquid crystal polymer substrates at W-band. The proposed transition is achieved by using a SIW-fed linearly flared antipodal slot line inserted into a WG. To minimize packaging leakage, no guided vias are utilized in the slot line region. Full-wave simulation reveals a low insertion loss of 0.8 dB for the proposed transition at W-band. To experimentally demonstrate this design, a WG-to-SIW-to-WG transition was fabricated and characterized. The measured insertion and reflection loss of the back-to-back transition is less than 1.8 and −11 dB, respectively, at W-band.

Slot-Coupled Directional Filters in Multilayer LCP Substrates at 95 GHz

In this paper, traveling-wave directional filters (DFs) in multilayer liquid crystal polymer substrates were proposed at 95 GHz, consisting of two terminating microstrip lines (MSLs) in the top circuit layer, a shared ground and coupling slots in the second layer, and MSL loop resonators in the bottom layer. By using asymmetric phase topology for the loop, the proposed DFs address higher directivity and Q-factor over the traditional symmetric traveling-wave DFs. The single-loop DF was demonstrated with a 3-dB passband width of 4.8% and an insertion loss of 4.6 dB at 94 GHz. To improve the directivity, particularly the insertion loss, two identical DFs were cascaded in series in the direction of the terminating lines. A bandwidth of 8% and a low insertion loss of 2.6 dB can be obtained with a phase delay of 360° between the two DFs. Limited by the practical application, the proposed DFs were fabricated and demonstrated in hybrid substrates, which slightly increases the insertion loss. The measured insertion loss of the single-loop and double-loop DFs is 5.2 and 3.1 dB at 95 GHz, respectively, showing good agreement with the simulated data.

A Novel Slot Array Antenna With Substrate Integrated Coaxial Line Technique

In this letter, a novel slot array antenna with a substrate-integrated coaxial line (SICL) technique is proposed. The proposed antenna has radiation slots etched homolaterally along the mean line in the top metallic layer of SICL and achieves a compact transverse dimension. A prototype with 5 $\times$ 10 longitudinal slots is designed and fabricated with a multilayer liquid crystal polymer (LCP) process. A maximum gain of 15.0 dBi is measured at 35.25 GHz with sidelobe levels of $-$ 28.2 dB ( E -plane) and $-$ 33.1 dB ( H -plane). The close correspondence between experimental results and designed predictions on radiation patterns has validated the proposed excogitation in the end.

空间调制光传播方向及偏振态的多层图案化液晶聚合物薄膜研究

空间调制光传播方向及偏振态的多层图案化液晶聚合物薄膜研究

Backlobe and Sidelobe Suppression of a Q-Band Patch Antenna Array by Using Substrate Integrated Coaxial Line Feeding Technique

A low profile aperture-coupled patch antenna array with high front-to-back-ratio (FTBR) is designed at Q -band by using substrate integrated coaxial line technique, the intrinsic shielded enclosure of which is capable of constructing an equal-phase and amplitude-tapering feeding network with backlobe suppression. An illustrative example of a 6 $\times$ 6 patch antenna array is designed and fabricated with a 2 $\times$ 2 prior verification module by using multilayer liquid crystal polymer process. Measured results indicate that the array can achieve a gain of 17.6 dBi at 41.5 GHz and the first sidelobe levels is $-$ 24.1 dB in the E -plane and $-$ 20.4 dB in the H -plane. The holistic FTBR is better than 27 dB in both planes.

High Efficiency GaN 2.5 to 9 GHz Power Amplifiers Realized in Multilayer LCP Hybrid Technology

This letter presents wide bandwidth and high efficiency hybrid balanced and push-pull amplifier circuit topologies using Gallium Nitride (GaN) transistors and Liquid Crystal Polymer (LCP) multilayer circuit techniques. Push-pull circuit configurations allow differential and common mode impedances to be presented at even and odd harmonics independently, enabling the continuous mode (class BJ) design space to be exploited. Push-pull amplifiers display drain efficiencies $>$ 40%, output power $>$ 5 W over a bandwidth of 3.5 to 8.5 GHz at 2 dB compression levels, and under CW conditions. By comparison, although designed with identical performance goals, a conventional quadrature balanced amplifier performance is below that of the push-pull configuration.

23:1 Bandwidth ratio quasi‐lumped component balun on a multilayer organic substrate

Author(s): Pham, BL; Ta, HH; Pham, AV; Leoni, RE; Leviatan, Y | Abstract: In this study, the authors present the design and development of a novel ultra-wideband coupled-line balun on a multilayer liquid crystal polymer substrate. The balun is designed using a quarter wavelength (λ/4) asymmetric broadside coupled line. The defected ground structure and a lumped phase compensation circuit are developed to achieve wide bandwidth performance for the balun. The balun has a measured bandwidth ratio of 23:1, from 80 to 1860 MHz. Within the operating bandwidth, the experimental results demonstrate that the balun achieves an input return loss of better than 10 dB, an insertion loss of better than 1 dB, an amplitude imbalance of better than ±0.4 dB and a phase imbalance of better than ±10°. The size of the balun is 40.64 mm × 40.64 mm or 0.22 λg × 0.22 λg, where λg is the guided wavelength at the centre frequency of 970 MHz.

High Rejection, Self-Packaged Low-Pass Filter Using Multilayer Liquid Crystal Polymer Technology

A compact low-pass filter based on the principle of destructive interference is proposed and analyzed, followed by an improved design demonstrating very high rejection levels better than 40 dB over a wide frequency span. Both filters, fabricated using liquid crystal polymer (LCP) multilayer techniques, are self-packaged, with small footprint and profile, and also very lightweight. Simulation and measured results are presented, showing good agreement.

Ultra-wideband (UWB) Bandpass Filter with Cascaded Lowpass Filter on Multilayer Liquid-Crystal Polymer (LCP) Substrate

ABSTRACTAn ultra-wideband (UWB) bandpass filter with extended upper-stopband on multilayer liquid-crystal-polymer (LCP) substrate is presented in this paper. The proposed filter is designed to select the frequency band from 1.0 to 20 GHz. The filter consists of two parallel-coupled stub-loaded resonators separated by a composite lowpass filter. The composite lowpass filter is implemented to obtain a very wide rejection band. The proposed filter is fabricated using multilayer LCP technology. Excellent agreement between expected and measured results of the filter is obtained. The measurement results show that the fabricated filter has a fractional bandwidth of 180% and a very low insertion loss of less than 0.6 dB at center frequency of 10.5 GHz. The measured filter has a wide stopband and an excellent rejection level higher than 40 dB.

Parallel-coupled stub-loaded resonator bandpass filter with ultra-wideband passband on multilayer liquid crystal polymer substrates

A multilayer bandpass filter with ultra-wideband passband is presented in this paper. The filter is designed to have a very wide passband with a fractional bandwidth of about 180% at a center frequency of 10.5 GHz. The filter consists of two sections of parallel-coupled lines loaded at the center with short-circuited stub. Each of the coupled line sections and short-circuited stubs is designed to be a quarter-wavelength long at the desired center frequency. As a result, the filter exhibited a selective filtering characteristic equivalent to a five-pole Chebyshev filter with a very low insertion loss. The proposed filter is realized and fabricated using multilayer liquid crystal polymer substrate. The design is successfully realized in theory and verified by full-wave electromagnetic simulation of the full layout and the experiment where excellent agreement is obtained.