• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Compact millimeter-wave air-filled substrate-integrated waveguide crossover employing homogeneous cylindrical lens*#

    2023-09-21 06:31:18ChunGENGJiweiLIANDazhiDING
    關鍵詞:前沿性教學大綱知識結構

    Chun GENG ,Jiwei LIAN ,Dazhi DING

    1Qian Xuesen College, Nanjing University of Science and Technology, Nanjing 210094, China

    2School of Microelectronics (School of Integrated Circuits), Nanjing University of Science and Technology, Nanjing 210094, China

    3State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China

    We propose a new method to design crossovers by employing an embedded homogeneous cylindrical lens (HCL).Compared with traditional crossover designs,this strategy introduces an HCL within the air-filled substrate-integrated waveguide (SIW) crossover cavity to direct the incident waves in the desired direction.According to ray-tracing analysis,the added HCL can efficiently concentrate the electromagnetic wave propagating from the input to the output without increasing the fabrication complexity or footprint.The operating mechanism of this method is elaborated in detail,and is further verified by E-field distributions.Using the air-filled SIW technology,two-,three-,and four-channel crossovers operating at the millimeterwave are developed and fabricated to demonstrate the practical feasibility of the proposed method.Some transitional structures are designed for experimental purposes.It is found that the simulated fractional bandwidths (FBWs) related to two-,three-,and four-channel air-filled SIW crossovers are 33%,14%,and 10%,respectively;the dimensions of their core areas are 0.74λ×0.74λ,1.43λ×1.43λ,and 1.90λ×1.90λ,respectively.Comparisons between our method and similar approaches in the literature illustrate the advantages of our method.

    1 Introduction

    Most reported crossovers operating at the microwave frequency are based on microstrip technology because of its merits of planar structure and ease of integration (Feng et al.,2016;Jiao et al.,2018;Tajik et al.,2018;Yu and Sun,2019).Recently,millimeterwave and terahertz applications have attracted great interest due to the higher availability of unallocated frequency spectrum resources.In this situation,some close or quasi-close structures are preferable in crossover designs,which include waveguide (Cheng et al.,2021),substrate-integrated waveguide (SIW) (Djerafi and Wu,2009;Hesari and Bornemann,2017;Sun et al.,2020;Qi et al.,2021),and printed ridge gap waveguide (Ali and Sebak,2018).

    Traditional crossovers usually comprise four ports and deal with the intersections between two channels.As the circuit complexity increases,intersections among more than two channels appear and they should be taken into account in circuit designs.One feasible alternative is to cascade multiple two-channel crossovers.For instance,three two-channel crossovers can be combined into a three-channel crossover,or six two-channel crossovers can cooperatively build a four-channel crossover.However,apparently too many two-channel crossovers are required and cascaded in these cases,which can lead to larger sizes and increased losses (Li and Luk,2016).

    Facing this issue,the design of crossovers dealing with more than two channels simultaneously has become a significant and challenging research topic.Tang and Chuang (2015) used double rings in the microstrip to construct a three-channel crossover,which was later extended to a four-channel crossover (Chu and Tang,2018).Wu et al.(2014) proposed a different three-channel crossover by using lumped inductors.Subsequently,a microstrip three-channel crossover with the filtering property was developed (Wu and Mao,2016).However,for reasons explained above,these crossovers in the microstrip technology are not suitable for millimeter-wave or above millimeter-wave applications.

    Some crossovers have been proposed that use close or quasi-close transmission lines.Using a cavity for excitation TE011,TE101,and TM110modes (Lin et al.,2019),a three-channel waveguide filtering crossover was reported at the expense of a large size.Lian et al.(2020) designed a four-channel crossover using SIW technology by adding a power divider to each port,which eventually led to a larger footprint.When resorting to TE102and TE201modes,four-,five-,and sixchannel SIW filtering crossovers have been realized.To support the TE102and TE201modes simultaneously,the whole design is formed by cascaded rectangular cavities,while it suffers from a relatively large footprint (Zhan et al.,2020;Zhou and Wu,2020).

    Given the state-of-the-art development of crossovers,a new method to design air-filled SIW crossovers using an embedded homogeneous cylindrical lens (HCL) was proposed by Geng et al.(2022).In previous studies,HCLs (two-dimensional case) or homogeneous spherical lenses (three-dimensional case) have been widely applied and explored in antenna designs (Bekefi and Farnell,1956;Gunderson,1972;Schoenlinner et al.,2002;Boriskin et al.,2008;Costa et al.,2009;Zhang et al.,2011).As for the antenna design,the introduced HCL enables the conversion from spherical or cylindrical wave to planar wave,so that a high-directivity radiation can be achieved.Meanwhile,the feasibility of such lens in crossover designs is still questionable.In the proposed crossover design,the introduced HCL helps concentrate the electromagnetic wave and suppress the wave scattering within the airfilled SIW crossover cavity.Compared with previously published designs,the proposed method has mainly three salient merits.Firstly,this method drills an airfilled area to build an HCL without increasing the crossover footprint.Secondly,it is applicable to the two-channel crossover and can be extended to three-,four-channel crossovers,etc.Thirdly,it can be applied in single-layer SIW technology,which serves as an attractive candidate for low-loss and highly-integrated millimeter-wave applications.

    2 Air-filled SIW crossover design

    2.1 Operation principle

    Fig.1 depicts the topology of the proposed method for two-,three-,and four-channel crossovers.For the simplest case,it is composed of four ports (two channels).Different from traditional crossover designs,an extra HCL is inserted at the intersection.As a result,the electromagnetic wave coming from port 1 as an example will exclusively propagate toward port 3,while satisfactory isolation is observed between port 1 and port 2 (port 4).This two-channel topology can be extended to three-and four-channel cases by adjusting the diameters of the crossover cavity and the inserted HCL.

    Fig.1 Topologies of two-channel (a),three-channel (b),and four-channel (c) crossovers

    Fig.2a describes the design parameters from both the top view and side view.The width of the open air-filled SIW is denoted bywand the thickness of the substrate ish;ais the radius of the HCL,whiler0is the distance between the input air-filled SIW and the center of the HCL.The relative dielectric constants inside and outside the HCL are indicated byεr2andεr1,respectively.

    Fig.2 Design parameters of the HCL (a) and ray-tracing analysis of the crossover with HCL (b)

    Fig.3 E-field distribution with (a) and without (b) HCL at 30 GHz (T is the period of the electromagnetic field)

    To further reveal the operation mechanism of the proposed method,the ray-tracing analysis of the crossover with HCL is displayed in Fig.2b.Lian et al.(2020) demonstrated that concentrating the incoming electromagnetic wave is an effective method to design crossovers,which introduces a power divider at each port,so that the electromagnetic wave is concentrated.At the same time,the added power dividers lead to a larger footprint.In contrast,the proposed topology with an embedded HCL has the merit of better compactness,which is an alternative to concentrating the electromagnetic wave.In this case,the ray escaping out of the HCL should be parallel to thex-axis,as shown in Fig.2b.In contrast,when designing a crossover,each ray encountering two refractions is expected to arrive at the position mirrored to the source point,as shown in Fig.2b.

    按照“厚基礎、強應用、有特色”的原則,精簡課程體系,設置實用性、前沿性強的專業(yè)課程,補齊短板,增加關聯(lián)大、交叉多的基礎課程開設,打破專業(yè)與學科之間的橫向壁壘,積極開發(fā)綜合性特色課程。通過調(diào)研學生對知識的多層次需求,適當增加選修課數(shù)量,滿足學生全面發(fā)展的需要。從全面提升和完善學生的科學文化素養(yǎng)、合理的知識結構和創(chuàng)新創(chuàng)業(yè)實踐能力出發(fā),制訂符合社會需要的教學大綱和教學計劃,確定教學內(nèi)容,[5]鼓勵教師將最新學術動態(tài)、技術成果和創(chuàng)新經(jīng)驗融入課堂教學。

    The above is a brief description of the operation mechanism of the proposed method,and a more detailed description can be found in Section 1 of the supplementary materials.More details about this result can be found in (Gunderson,1972).

    To give a clearer view of the impact brought by the HCL,we compute the model using the High-Frequency Structure Simulator (HFSS) and show the E-field distribution,and the results contains two open air-filled SIWs with or without an HCL.As depicted in Figs.3a and 3b,it is observed that the E-field is bound in the HCL and most of the incoming energy propagates toward the other port.In contrast,if the HCL was removed,the energy would scatter outward and severe energy leakage would appear.

    2.2 Design process

    Derived from the abovementioned topology,a two-channel air-filled SIW crossover is designed,as shown in Fig.4a,wherea1is the radius of the HCL of the two-channel crossover,d1is the distance between the centers of two adjacent metal holes,andd2is the diameter of the metal holes.The first step of the design procedure is to determine the relative dielectric constants inside and outside the HCL.To simplify the fabrication,an air-filled area is built by drilling the substrate.In this way,one can obtain an interface between two materials within a single substrate.Here,a Rogers RT/duroid 5880 substrate with a thickness of 0.787 mm is applied.Then,we haveεr1=1.0 andεr2=2.2.Secondly,the width of the open air-filled SIWwshould be large enough to support the dominant mode within the interested frequency spectrum.In this work,w=7.2 mm is chosen.Then,one open air-filled SIW should be duplicated to four and placed clockwise to build a closed cavity.Finally,an HCL is inserted at the center and its diameter is optimized to achieve the minimum reflection and isolation.

    Fig.4 Simulated HFSS model (a),E-field distribution (b),and S-parameters (c) of the two-channel SIW crossover (d1=0.80 mm,d2=0.40 mm, a1=2.00 mm,and w=7.20 mm)

    The E-field distribution of the designed twochannel crossover at 30 GHz is displayed in Fig.4b,in which a crossed transmission is observed.The simulatedS-parameters of the designed two-channel crossover are plotted in Fig.4c,whereS11is the reflection coefficient of port 1,S21is the isolation coefficient of port 1 and port 2,andS31is the isolation coefficient of port 1 and port 3.From 25.8 to 38.3 GHz,the reflection coefficient and the isolation coefficients are lower than -15 dB,indicating a fractional bandwidth (FBW) of 39%.Within this frequency range,the insertion loss varies from 0.1 to 0.5 dB.

    To describe the design process more clearly,parametric study is given in Section 2 of the supplementary materials.In the above,the design details of the twochannel air-filled SIW crossover have been elaborated.Interestingly,the proposed method can be directly extended to crossovers with more channels.As shown in Fig.5a,a three-channel air-filled SIW crossover is designed using the proposed topology.Since the design process and operation principle are similar to those in the two-channel case,only the final model and simulation results are provided here.The E-field distribution at 34 GHz is displayed in Fig.5b,in which a crosspassing property is observed.The optimalS-parameters are plotted in Fig.5c.Due to the symmetry of the configuration,S51andS61are omitted.From 31.9 to 36.6 GHz,both the reflection and isolation coefficients are less than -15 dB;i.e.,the FBW is 14%.Within this frequency range,the minimum and maximum transmission losses are 0.1 dB and 0.7 dB,respectively.

    Fig.5 Simulated HFSS model (a),E-field distribution (b),and S-parameters (c) of the three-channel SIW crossover (a2=2.10 mm,w=7.20 mm)

    Similarly,a four-channel counterpart is designed (Fig.6a),and its E-field distribution is shown (Fig.6b).Indicated by theS-parameters in Fig.6c,the FBW is 7.5% (32.0 to 34.5 GHz).The minimum insertion loss is 0.2 dB,while the maximum insertion loss is 0.7 dB.

    Fig.6 Simulated HFSS model (a),E-field distribution (b),and S-parameters (c) of the four-channel SIW crossover (a3=4.00 mm,w=7.20 mm)

    3 Results and discussion

    3.1 Simulation and measurement

    For the experiments,transitions from SIW to airfilled SIW and coplanar waveguide (CPW) to SIW are designed,as shown in Fig.7a (Parment et al.,2015).The simulated reflection and transmission coefficients are plotted in Fig.7b.From 25.9 to 41.6 GHz,the reflection coefficient is below -15 dB,corresponding to a maximum insertion loss of 0.8 dB and a minimum insertion loss of 0.4 dB.The fabricated prototypes of the two-,three-,and four-channel air-filled SIW crossovers are shown in Fig.8.The interior,top,and bottom views are illustrated in Figs.8a-8c.Two aluminum plates are added on the top and bottom of the substrate to act as ground planes.The design parameters of the crossover are listed in Table 1.

    Table 1 Design parameters and values

    Table 2 Comparisons between the designed two-channel crossovers and similar designs

    Fig.7 Simulated HFSS model (a) and S-parameters (b) of the transition

    Fig.8 Interior (a),top (b),and bottom (c) views of the fabricated prototypes (two-channel,three-channel,and four-channel crossovers from left to right)

    To describe the experimental results more clearly,an analysis based on the simulated and measured results of the crossovers is given in Section 3 of the supplementary materials for a detailed description.It can be concluded that the largest difference between the simulation and the measurement is in the insertion loss,about 1.7 dB.This discrepancy comes mainly from the insertion loss of the connectors,that of the connection between the connectors and the CPW,and the fabrication tolerance.The additional insertion loss mentioned above can be calibrated by using a thru-reflect-line (TRL) calibration to correct the effects of connectors and transitions,to correct characterize the demonstrator.The details of the calibration process are demonstrated in Doghri et al.(2015).

    3.2 Discussion

    The comparisons between the proposed air-filled SIW crossovers and similar designs with two or more channels are summarized in Tables 2 and 3,respectively.It is concluded that using microstrip line can build extraordinarily compact two-channel crossover (Tajik et al.,2018).However,the microstrip line as an open structure would lead to increased loss operating at higher frequencies.Considering designs in the literature (Djerafi and Wu,2009;Hesari and Bornemann,2017;Ali and Sebak,2018;Sun et al.,2020),it is noted that all of them suffer from relatively small bandwidth and large footprint when using either SIW or printed ridge gap waveguide technology.This brings the advantage of the proposed method in two-channel crossover designs;that is,the two-channel air-filled SIW crossover has a large FBW of 33% in the simulation and a reduced size of 0.74λ×0.74λ(λis the freespace wavelength at the center frequency).For fair comparisons,the FBW result is extracted from the complete model in the simulation including the SIW crossover and the transitions from air-filled SIW to CPW,and the size is related to the coupling area,which is surrounded by the open air-filled SIWs.

    Table 3 describes crossovers with more than two channels.It can be seen that using a microstrip can build similar compact crossovers (Wu et al.,2014;Tang and Chuang,2015;Chu and Tang,2018).However,SIW technologies usually suffer from a larger footprint (Lian et al.,2020;Zhou and Wu,2020).The designed three-and four-channel crossovers effectively reduce the occupied areas while maintaining sufficient FBWs.

    Table 3 Comparisons between the designed multi-channel crossovers and similar designs

    4 Conclusions

    In this work,a new method of crossover designs is presented by introducing an HCL in the middle of the air-filled SIW crossover cavity.According to raytracing analysis,the introduced HCL can concentrate and direct the electromagnetic wave in the desired direction and suppress the scattering within the cavity.Two-,three-,and four-channel air-filled SIW crossovers are designed and fabricated successively to demonstrate the feasibility of the proposed method.The corresponding FBWs of these cases in the simulation are 33%,14%,and 10%,separately.The dimensions of their core areas are only 0.74λ×0.74λ,1.43λ×1.43λ,and 1.90λ×1.90λ,separately.Compared with similar approaches,the designed crossovers show the merits of simple structure,compactness,and wide FBWs.

    Contributors

    Chun GENG and Jiwei LIAN designed the research.Chun GENG processed the data.Chun GENG and Jiwei LIAN drafted the paper.Dazhi DING revised and finalized the paper.

    Compliance with ethics guidelines

    Chun GENG,Jiwei LIAN,and Dazhi DING declare that they have no conflict of interest.

    Data availability

    The data that support the findings of this study are available from the corresponding author upon reasonable request.

    List of supplementary materials

    1 Supplement to the operation principle

    2 Supplement to the design process

    3 Supplement to the experiment

    猜你喜歡
    前沿性教學大綱知識結構
    把握核心概念 優(yōu)化知識結構
    物理之友(2020年12期)2020-07-16 05:39:18
    以綱為要,創(chuàng)新課程體系建設
    ——上海老年大學教學大綱建設實踐探索
    論專業(yè)論文寫作的先進性和前沿性
    以人為本 以綱為綱
    ——老年大學教學大綱實踐與探索
    互動式教學大綱在本科教學中的實踐與探索
    ——以《工程制圖與識圖》為例
    贏未來(2019年33期)2019-12-17 09:45:28
    我國正當防衛(wèi)研究的網(wǎng)絡知識結構與核心脈絡
    法大研究生(2019年2期)2019-11-16 00:39:26
    解讀《魯科版化學必修一新教材》
    概率統(tǒng)計知識結構與方法拓展
    音樂學的學科現(xiàn)狀與前沿問題研究
    基于九因子模型的新手教師TPACK知識結構分析
    国产aⅴ精品一区二区三区波| 99国产综合亚洲精品| 我的老师免费观看完整版| 欧美日本视频| 法律面前人人平等表现在哪些方面| 国产亚洲精品久久久久久毛片| 中文在线观看免费www的网站 | 日韩大尺度精品在线看网址| 成人手机av| a级毛片a级免费在线| 97碰自拍视频| 成人国产综合亚洲| 99精品在免费线老司机午夜| 国产成人一区二区三区免费视频网站| 亚洲国产欧洲综合997久久,| 国产av一区二区精品久久| 国产99白浆流出| 日韩欧美在线二视频| 后天国语完整版免费观看| 久久久久久久久久黄片| 亚洲全国av大片| 国产99久久九九免费精品| 日韩欧美国产在线观看| 好男人在线观看高清免费视频| 国产亚洲欧美在线一区二区| 天天躁夜夜躁狠狠躁躁| 搞女人的毛片| 黄色a级毛片大全视频| 国产熟女午夜一区二区三区| 一卡2卡三卡四卡精品乱码亚洲| 免费看十八禁软件| 国产欧美日韩精品亚洲av| 97碰自拍视频| 一进一出抽搐gif免费好疼| 韩国av一区二区三区四区| 欧美日韩亚洲国产一区二区在线观看| 国内精品久久久久久久电影| 99热6这里只有精品| 一个人免费在线观看的高清视频| 女人高潮潮喷娇喘18禁视频| 激情在线观看视频在线高清| 欧美乱色亚洲激情| 可以在线观看毛片的网站| 女人被狂操c到高潮| 高清毛片免费观看视频网站| 一个人观看的视频www高清免费观看 | 日韩 欧美 亚洲 中文字幕| 中文亚洲av片在线观看爽| 女同久久另类99精品国产91| 一本大道久久a久久精品| 国产人伦9x9x在线观看| 成年免费大片在线观看| 一本久久中文字幕| 国产精品 国内视频| 一个人免费在线观看电影 | av在线播放免费不卡| 高潮久久久久久久久久久不卡| 1024视频免费在线观看| 黄频高清免费视频| 亚洲欧美一区二区三区黑人| 成人国产一区最新在线观看| 99精品在免费线老司机午夜| 国产日本99.免费观看| 老鸭窝网址在线观看| 久久久精品欧美日韩精品| 亚洲男人天堂网一区| 不卡一级毛片| 中文资源天堂在线| 伦理电影免费视频| 后天国语完整版免费观看| 波多野结衣高清作品| 日韩 欧美 亚洲 中文字幕| 两个人的视频大全免费| 777久久人妻少妇嫩草av网站| 日日爽夜夜爽网站| 国产精品永久免费网站| 精品熟女少妇八av免费久了| 在线观看午夜福利视频| 18禁国产床啪视频网站| 18禁黄网站禁片免费观看直播| 神马国产精品三级电影在线观看 | 午夜福利18| 熟妇人妻久久中文字幕3abv| 99国产精品一区二区三区| 亚洲av成人一区二区三| 一本精品99久久精品77| 色综合欧美亚洲国产小说| www国产在线视频色| 成熟少妇高潮喷水视频| 国产麻豆成人av免费视频| 亚洲一码二码三码区别大吗| 亚洲精品粉嫩美女一区| 欧美av亚洲av综合av国产av| 久久久久久人人人人人| av免费在线观看网站| 精品国内亚洲2022精品成人| 高潮久久久久久久久久久不卡| 美女扒开内裤让男人捅视频| 人妻久久中文字幕网| 色综合欧美亚洲国产小说| 成年女人毛片免费观看观看9| 黄片大片在线免费观看| 一二三四社区在线视频社区8| 精品电影一区二区在线| 日韩欧美 国产精品| 天天一区二区日本电影三级| 可以在线观看毛片的网站| 夜夜躁狠狠躁天天躁| 欧美日本视频| 手机成人av网站| netflix在线观看网站| 亚洲精品av麻豆狂野| 免费在线观看日本一区| 久久午夜综合久久蜜桃| x7x7x7水蜜桃| 国产精华一区二区三区| 欧美国产日韩亚洲一区| 久99久视频精品免费| 欧美日韩乱码在线| 亚洲国产欧洲综合997久久,| 国产精品一区二区三区四区久久| 两个人免费观看高清视频| 草草在线视频免费看| 老汉色av国产亚洲站长工具| 亚洲性夜色夜夜综合| 午夜福利18| av中文乱码字幕在线| 欧美激情久久久久久爽电影| 国产精品一区二区精品视频观看| 一二三四在线观看免费中文在| 亚洲欧美精品综合一区二区三区| 久久久久免费精品人妻一区二区| 国内精品一区二区在线观看| 亚洲熟女毛片儿| ponron亚洲| 老司机深夜福利视频在线观看| 亚洲男人的天堂狠狠| 国内精品久久久久久久电影| 日韩欧美在线二视频| 国产1区2区3区精品| 搞女人的毛片| 老熟妇乱子伦视频在线观看| 欧美绝顶高潮抽搐喷水| 国产精品亚洲美女久久久| 女人爽到高潮嗷嗷叫在线视频| 成人国产综合亚洲| 每晚都被弄得嗷嗷叫到高潮| 此物有八面人人有两片| 亚洲av成人不卡在线观看播放网| 欧美乱码精品一区二区三区| 麻豆一二三区av精品| 成人永久免费在线观看视频| 欧美日韩瑟瑟在线播放| 国产激情偷乱视频一区二区| 成人一区二区视频在线观看| 精品国内亚洲2022精品成人| 一级毛片高清免费大全| 一级毛片女人18水好多| 欧美久久黑人一区二区| 精品久久久久久久久久免费视频| 亚洲免费av在线视频| 欧美3d第一页| 国产麻豆成人av免费视频| 无人区码免费观看不卡| 国产精华一区二区三区| 一级片免费观看大全| 精品久久久久久久末码| a级毛片在线看网站| av超薄肉色丝袜交足视频| 黄色视频,在线免费观看| 欧美日韩中文字幕国产精品一区二区三区| 男女床上黄色一级片免费看| 亚洲熟妇中文字幕五十中出| 久久精品综合一区二区三区| 深夜精品福利| 免费av毛片视频| 最近视频中文字幕2019在线8| 日韩大码丰满熟妇| 在线观看免费日韩欧美大片| 亚洲aⅴ乱码一区二区在线播放 | 久久久精品国产亚洲av高清涩受| 日韩欧美国产在线观看| 日日爽夜夜爽网站| 亚洲午夜精品一区,二区,三区| 欧美乱色亚洲激情| 国产精品乱码一区二三区的特点| 国产精品久久久久久久电影 | 一进一出好大好爽视频| 国产在线观看jvid| 久久精品91蜜桃| 午夜福利在线在线| 免费在线观看完整版高清| 久久中文字幕人妻熟女| 精品国产乱码久久久久久男人| 亚洲av熟女| 一级片免费观看大全| 免费看十八禁软件| 丝袜人妻中文字幕| 久久久久国产一级毛片高清牌| 国产激情欧美一区二区| 窝窝影院91人妻| 久久草成人影院| 久久精品国产99精品国产亚洲性色| 欧美大码av| 成人永久免费在线观看视频| 国产精品1区2区在线观看.| 此物有八面人人有两片| 国内揄拍国产精品人妻在线| 午夜免费观看网址| 丰满的人妻完整版| 国产精品一区二区三区四区久久| 欧美性猛交╳xxx乱大交人| 91字幕亚洲| 亚洲无线在线观看| 极品教师在线免费播放| 亚洲av电影在线进入| 男插女下体视频免费在线播放| 亚洲一卡2卡3卡4卡5卡精品中文| 久久久国产成人免费| 久久香蕉激情| bbb黄色大片| 日本撒尿小便嘘嘘汇集6| 国产成人aa在线观看| 欧美黄色淫秽网站| 国产成人欧美在线观看| 国产成人啪精品午夜网站| 黄色a级毛片大全视频| 免费观看精品视频网站| 国内精品久久久久精免费| 9191精品国产免费久久| 欧美绝顶高潮抽搐喷水| 亚洲精品一卡2卡三卡4卡5卡| 久久国产精品影院| 999久久久精品免费观看国产| 熟女电影av网| 欧美又色又爽又黄视频| 国产高清激情床上av| 久久精品影院6| 香蕉丝袜av| 成人午夜高清在线视频| 国产视频内射| 亚洲 欧美一区二区三区| 日本黄色视频三级网站网址| 精品不卡国产一区二区三区| 国内少妇人妻偷人精品xxx网站 | 免费无遮挡裸体视频| 久久欧美精品欧美久久欧美| 久久精品综合一区二区三区| 18美女黄网站色大片免费观看| 女警被强在线播放| 18禁黄网站禁片午夜丰满| 法律面前人人平等表现在哪些方面| 国内精品久久久久精免费| 国产亚洲精品综合一区在线观看 | 啦啦啦免费观看视频1| 一区二区三区激情视频| av天堂在线播放| 国产免费av片在线观看野外av| 黄色视频不卡| 又大又爽又粗| 国产区一区二久久| 国产精品 欧美亚洲| 韩国av一区二区三区四区| 曰老女人黄片| 日本免费一区二区三区高清不卡| 黄色女人牲交| 99在线人妻在线中文字幕| 69av精品久久久久久| 亚洲黑人精品在线| 人成视频在线观看免费观看| 亚洲成av人片免费观看| 久久久久国产一级毛片高清牌| 国产亚洲精品综合一区在线观看 | 亚洲乱码一区二区免费版| 久久这里只有精品中国| 久久久国产精品麻豆| 99riav亚洲国产免费| 亚洲成人久久爱视频| 欧美国产日韩亚洲一区| 欧美乱码精品一区二区三区| 老汉色∧v一级毛片| 色哟哟哟哟哟哟| 国产精品av视频在线免费观看| 免费看美女性在线毛片视频| 国产亚洲av嫩草精品影院| 97超级碰碰碰精品色视频在线观看| 精品久久久久久久久久久久久| 亚洲国产欧美网| 小说图片视频综合网站| av中文乱码字幕在线| 亚洲美女视频黄频| 叶爱在线成人免费视频播放| 亚洲欧美日韩高清专用| 蜜桃久久精品国产亚洲av| 无限看片的www在线观看| 久久久久久免费高清国产稀缺| 久久精品夜夜夜夜夜久久蜜豆 | 高清毛片免费观看视频网站| 欧美色欧美亚洲另类二区| 国产精品永久免费网站| 一级毛片女人18水好多| 中文字幕高清在线视频| 欧美日韩黄片免| 国产精品香港三级国产av潘金莲| 免费在线观看完整版高清| 男女之事视频高清在线观看| 久久性视频一级片| 精品一区二区三区av网在线观看| 精品不卡国产一区二区三区| 在线观看一区二区三区| 淫秽高清视频在线观看| www.www免费av| 亚洲第一电影网av| 成人高潮视频无遮挡免费网站| 欧美av亚洲av综合av国产av| 亚洲全国av大片| 久久精品夜夜夜夜夜久久蜜豆 | 18禁黄网站禁片午夜丰满| 91大片在线观看| 好看av亚洲va欧美ⅴa在| 999久久久精品免费观看国产| 51午夜福利影视在线观看| 欧美日韩福利视频一区二区| www.精华液| 日韩国内少妇激情av| 亚洲成人中文字幕在线播放| 国产成人精品久久二区二区91| bbb黄色大片| 韩国av一区二区三区四区| 中文亚洲av片在线观看爽| 国产精品av视频在线免费观看| 国产成人精品久久二区二区91| 中文字幕精品亚洲无线码一区| 国产成+人综合+亚洲专区| 成人特级黄色片久久久久久久| 12—13女人毛片做爰片一| 18禁黄网站禁片免费观看直播| 亚洲性夜色夜夜综合| 在线观看免费午夜福利视频| 国产在线精品亚洲第一网站| 亚洲av五月六月丁香网| avwww免费| 一个人观看的视频www高清免费观看 | 亚洲专区字幕在线| 黑人巨大精品欧美一区二区mp4| 午夜福利在线在线| 欧美一区二区国产精品久久精品 | 成人18禁在线播放| 久久久久久久久中文| 亚洲成人免费电影在线观看| 最好的美女福利视频网| 久久久久久大精品| 国产欧美日韩一区二区精品| 色综合欧美亚洲国产小说| 欧美乱码精品一区二区三区| 日韩免费av在线播放| 他把我摸到了高潮在线观看| а√天堂www在线а√下载| 97超级碰碰碰精品色视频在线观看| 免费一级毛片在线播放高清视频| 一本大道久久a久久精品| 欧美激情久久久久久爽电影| 美女大奶头视频| 亚洲欧美一区二区三区黑人| x7x7x7水蜜桃| 在线国产一区二区在线| 久久婷婷成人综合色麻豆| 黄片小视频在线播放| 后天国语完整版免费观看| 在线看三级毛片| 色综合婷婷激情| 国内少妇人妻偷人精品xxx网站 | 国产免费av片在线观看野外av| 日本 欧美在线| 欧美一级a爱片免费观看看 | 日日干狠狠操夜夜爽| svipshipincom国产片| 亚洲中文字幕一区二区三区有码在线看 | netflix在线观看网站| 国产精品综合久久久久久久免费| 88av欧美| 色精品久久人妻99蜜桃| 一卡2卡三卡四卡精品乱码亚洲| 又紧又爽又黄一区二区| 999久久久精品免费观看国产| 精品国产美女av久久久久小说| 两个人视频免费观看高清| 亚洲天堂国产精品一区在线| 久久久久久九九精品二区国产 | 久久久久国产一级毛片高清牌| av福利片在线观看| 免费电影在线观看免费观看| 黄片大片在线免费观看| 国产又黄又爽又无遮挡在线| 欧美日韩黄片免| 久久精品国产亚洲av香蕉五月| 在线观看免费日韩欧美大片| 夜夜躁狠狠躁天天躁| 免费无遮挡裸体视频| 欧美黑人精品巨大| 成人手机av| 亚洲av成人一区二区三| 国产三级在线视频| 大型av网站在线播放| 夜夜夜夜夜久久久久| 91在线观看av| 久久人人精品亚洲av| 亚洲aⅴ乱码一区二区在线播放 | 国产亚洲精品第一综合不卡| 国产成人精品久久二区二区91| 精品久久久久久成人av| 亚洲专区国产一区二区| 免费电影在线观看免费观看| tocl精华| 国产精品一区二区免费欧美| 欧美三级亚洲精品| 哪里可以看免费的av片| 精品一区二区三区四区五区乱码| 看片在线看免费视频| 久久精品人妻少妇| 极品教师在线免费播放| 亚洲免费av在线视频| 国产精品国产高清国产av| 免费av毛片视频| 国产精品一区二区三区四区免费观看 | 亚洲性夜色夜夜综合| 久久久久国产一级毛片高清牌| 亚洲熟女毛片儿| 精品国产乱码久久久久久男人| 午夜久久久久精精品| 神马国产精品三级电影在线观看 | 色综合婷婷激情| 村上凉子中文字幕在线| 国产精品 国内视频| 精品久久久久久久人妻蜜臀av| 女人高潮潮喷娇喘18禁视频| 日韩高清综合在线| 午夜精品一区二区三区免费看| 国产高清视频在线播放一区| 国产av不卡久久| 性欧美人与动物交配| 日本黄色视频三级网站网址| 丝袜美腿诱惑在线| 九色国产91popny在线| 久久人人精品亚洲av| 久久性视频一级片| 一本综合久久免费| 久久精品aⅴ一区二区三区四区| 18禁黄网站禁片午夜丰满| 91在线观看av| 搡老岳熟女国产| 国产av又大| 国产熟女xx| 男女床上黄色一级片免费看| 91麻豆av在线| 成人av一区二区三区在线看| 国产精品av久久久久免费| 男女那种视频在线观看| 黄色 视频免费看| 日韩欧美免费精品| 精品久久久久久成人av| 国产精品影院久久| 国产精品久久视频播放| 真人做人爱边吃奶动态| 国产精品久久久av美女十八| 99久久无色码亚洲精品果冻| 久久 成人 亚洲| 男女做爰动态图高潮gif福利片| 免费在线观看黄色视频的| 老熟妇乱子伦视频在线观看| 欧美黑人欧美精品刺激| 欧美一级毛片孕妇| 一区二区三区激情视频| 国产亚洲精品久久久久5区| 校园春色视频在线观看| 国产精品亚洲一级av第二区| 国产av不卡久久| svipshipincom国产片| 午夜福利18| 后天国语完整版免费观看| 搡老熟女国产l中国老女人| 国内揄拍国产精品人妻在线| 免费在线观看黄色视频的| 色老头精品视频在线观看| 精品乱码久久久久久99久播| 国产精品美女特级片免费视频播放器 | 男人的好看免费观看在线视频 | 波多野结衣高清作品| 亚洲av电影不卡..在线观看| 日本免费一区二区三区高清不卡| 亚洲国产精品成人综合色| 真人做人爱边吃奶动态| 啦啦啦免费观看视频1| 欧美乱妇无乱码| 91九色精品人成在线观看| 婷婷六月久久综合丁香| 可以在线观看的亚洲视频| 曰老女人黄片| 久久久国产精品麻豆| 日本一本二区三区精品| 在线视频色国产色| 禁无遮挡网站| 国产精品一区二区三区四区免费观看 | 夜夜看夜夜爽夜夜摸| 免费观看人在逋| 亚洲精品av麻豆狂野| 丰满人妻一区二区三区视频av | 黄色成人免费大全| 老汉色av国产亚洲站长工具| 亚洲国产精品久久男人天堂| 亚洲欧美日韩无卡精品| 久久久精品国产亚洲av高清涩受| 麻豆久久精品国产亚洲av| 高清毛片免费观看视频网站| 国产精品1区2区在线观看.| 亚洲av第一区精品v没综合| 国产精品电影一区二区三区| 91麻豆精品激情在线观看国产| 欧美中文日本在线观看视频| 免费在线观看影片大全网站| 日本免费a在线| 国产精品电影一区二区三区| 1024香蕉在线观看| 国产激情久久老熟女| 亚洲欧美日韩无卡精品| 日本一区二区免费在线视频| 中文亚洲av片在线观看爽| 国产高清有码在线观看视频 | 人妻夜夜爽99麻豆av| 一本久久中文字幕| 老熟妇乱子伦视频在线观看| 午夜福利免费观看在线| 看免费av毛片| 88av欧美| 久久国产精品人妻蜜桃| 欧美在线黄色| 可以免费在线观看a视频的电影网站| 午夜福利高清视频| 亚洲精品久久国产高清桃花| 国产精品国产高清国产av| 我要搜黄色片| 国产激情偷乱视频一区二区| 99在线人妻在线中文字幕| 99热这里只有是精品50| 亚洲成人国产一区在线观看| 中出人妻视频一区二区| 欧美又色又爽又黄视频| 成人av在线播放网站| 亚洲人成网站在线播放欧美日韩| 人成视频在线观看免费观看| 搞女人的毛片| 香蕉丝袜av| 国产午夜精品论理片| 欧美日韩中文字幕国产精品一区二区三区| 在线播放国产精品三级| 欧美av亚洲av综合av国产av| 一进一出抽搐动态| 亚洲中文字幕一区二区三区有码在线看 | 在线视频色国产色| 最新在线观看一区二区三区| 国产精品久久久久久亚洲av鲁大| 女警被强在线播放| 久久香蕉精品热| 亚洲av熟女| 中文字幕高清在线视频| 久久久久久国产a免费观看| 丁香六月欧美| 日韩三级视频一区二区三区| 久久久久精品国产欧美久久久| 成人三级黄色视频| 国产亚洲欧美98| 一进一出抽搐gif免费好疼| 国产av又大| а√天堂www在线а√下载| 欧美高清成人免费视频www| 国产精品九九99| 两个人看的免费小视频| 亚洲激情在线av| 国内久久婷婷六月综合欲色啪| 国产成人系列免费观看| 最新在线观看一区二区三区| 大型黄色视频在线免费观看| 青草久久国产| 动漫黄色视频在线观看| 午夜福利在线观看吧| 国产精品乱码一区二三区的特点| 我要搜黄色片| 亚洲专区字幕在线| 欧美性猛交黑人性爽| 午夜日韩欧美国产| 天天添夜夜摸| 好看av亚洲va欧美ⅴa在| 91成年电影在线观看| 久久 成人 亚洲| 亚洲人成77777在线视频| 亚洲av成人一区二区三| av有码第一页| 搡老熟女国产l中国老女人| 国产精品日韩av在线免费观看| 看免费av毛片| 国产午夜精品久久久久久| 精品国产乱子伦一区二区三区| 国产欧美日韩一区二区三| svipshipincom国产片| 国产私拍福利视频在线观看| 亚洲人成网站高清观看| 19禁男女啪啪无遮挡网站| 色综合婷婷激情| 午夜福利免费观看在线| 搡老熟女国产l中国老女人| 淫秽高清视频在线观看| 韩国av一区二区三区四区| 九色成人免费人妻av| 精品高清国产在线一区| 色综合站精品国产|