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1、文章编号：1009-8119（2005）12-0036-02基于SERENADE软件的微波带通滤波器的设计和仿真张 磊 夏永祥（北京理工大学信息科学技术学院，北京 100081）摘 要 论述了应用Ansoft 公司的Serenade 8.7 微波仿真软件设计微波带通滤波器的方法，并给出了优化仿真结果。试验结果表明，利用此软件的优化结果设计出的滤波器具有良好的滤波性能，而且无需调试，一致性好，适用于工程设计。关键词 带通滤波器，Ansoft, 耦合微带线Design and Simulation of Microwave Band-pass Filter Based on SERENADEZha
2、ng Lei Xia Yongxiang（School of Information and Science，Beijing Institute of Technology，Beijing 100081）Abstract In this paper，the method of design and simulation of microwave band-pass filter based on Serenade8.7 was introduced，and one specific design and simulation is given too. Through the result o
3、f the test, we can see that the filter designed based on Serenade8.7 has very good performance and consistency. Keywords Microwave filter，Ansoft， Microstrip line1 引 言在设计模拟电路时，对高频信号在特定频率或频段内的频率分量做加重或衰减处理是个十分重要的任务，因此，微波带通滤波器便成为现代电子系统中的一种关键部件，它的好坏直接决定系统的整体性能。微带平行耦合带通滤波器是工程上较为常见的一种微波带通滤波器，它是根据反对称原型滤波器设计
4、的，这样构成的平行耦合滤波器是关于其中心对称的。它由N节平行耦合微带线组成，两个微带线之间通过平行耦合线进行耦合，这些耦合线的两端开路，长度在中心频率上为半个波长，这种滤波器可看作由N+1个平行耦合节组合而成，这些耦合节在中心频率上是1/4波长。它的输入、输出由微带T型接头与之相连接，输入、输出阻抗为50欧姆。具有结构简单，易于实现微波部件和系统的集成化等优点。传统的滤波器设计计算方法比较复杂，而且工作量十分大，而由于现在软件技术的飞速发展，设计手段也变得越来越多，工作效率也越来越高。本设计就是利用ANSOFT公司的SERENADE软件来进行设计和优化。2 设计步骤本文所述的微波带通滤波器的设
5、计方法主要包括两个部分：1将标准切比雪夫低通滤波器变换为符合要求的特定带通滤波器。 首先建立归一化低通切比雪夫滤波器的结构； 利用频率变换将其低通频率特性变换为带通滤波器频率特性。2根据将集总参数元件变为分布参数元件的Richards变换和Kuroda规则用分布参数元件实现这些滤波器。3 设计实例滤波器设计要求如下。信号带宽：16381658MHz。 插入损耗：小于1.5dB。带内波动：小于0.2dB。带外抑制：频带两端（f015，f0为中心频率）处带外抑制到-50dBc,频带外（f030，f0为中心频率）抑制到60dBc。 滤波器设计过程为：工作频率超过500MHz的滤波器是难以用分立元件实
6、现的，这是由于工作波长与滤波器元件的物理尺寸相近，从而造成了多方面的损耗并使电路性能严重恶化。所以，实际滤波器的实现必须将一些工具（Richards变换、单位元件和Kuroda规则）的集总参数元件变换为分布参数元件。下面用耦合微带线来实现此滤波器：1选择标准低通滤波器参数。根据所要设计滤波器的性能指标，决定采用切比雪夫滤波器设计方法。查“给定波纹及插入损耗时选定切比雪夫滤波器节数的列表图”，可知滤波器可用三节来实现。 查表可知0.2dB波纹的标准三节切比雪夫滤波器参数为 g0=g4=1.0000，g1=g3=1.2275，g2=1.1525。2确定归一化带宽BW = =0.0121363根据带
7、宽指标计算下列参数Z0J01= = =0.12462 Z0J12= = =0.016027Z0J23= =0.016027Z0J34= = =0.12462这些参数可以用于计算传输线的奇模，偶模特性阻抗： Z0|i，i+1 =Z0(1-Z0Ji,i+1+(Z0Ji,i+1)2) Ze|i，i+1 =Z0(1+Z0Ji,i+1+(Z0Ji,i+1)2) 可得：Z0|0，1 =Z0(1-Z0J0，1+(Z0J0，1)2) =50（10.124620.124622）44.54551Ze|0，1 =Z0(1+Z0J0，1+(Z0J0，1)2)=50（10.124620.124622）57.00751Z
8、0|1，2=Z0(1-Z0J1，2+(Z0J1，2)2)=50（1-0.016027+0.0160272）=49.2115Ze|1，2 =Z0(1+Z0J1，2+(Z0J1，2)2)=50（1+0.016027+0.0160272）=50.8142Z0|2，3 =Z0(1-Z0J2，3+(Z0J2，3)2)=50（1-0.016027+0.0160272）=49.2115Ze|2，3 =Z0(1+Z0J2，3+(Z0J2，3)2)=50（1+0.016027+0.0160272）=50.8142Z0|3，4 =Z0(1-Z0J3，4+(Z0J3，4)2)=50（10.124620.124622
9、）=44.54551 Ze|3，4 =Z0(1+Z0J3，4+(Z0J3，4)2)=50（10.124620.124622）=57.00751 由这些参数利用Serenade的Tools工具中的Transmission Lines 可求出耦合微带线的W，S，P。考虑到优化时，中心频率会向低频方向偏移，所以，此处把中心频率设为1.668GHz，比实际的中心频率1.648GHz稍大。分别求出各段的W，S，P：W1=2.666649mm W2=2.76869mm W3=2.76869mm W4=2.66649mmS1=0.94787mm S2 =5.23893mm S3=5.23893mm S4 =
10、0.94787mmP1=30.7162mm P2=30.5697mm P3=30.5697mm P4=30.7162mm滤波器电路如图1所示：图1滤波器电路图微波滤波器仿真结果如图2所示：图2微波滤波器仿真结果由图2可知，只带外抑制一项指标满足要求，下面对其它指标进行优化。优化电路如图3所示：图3微波滤波器优化电路图 优化后的电路仿真结果如图4所示： 图4 优化后的仿真结果放大后的MS21和MS11如图5所示：图5放大后的MS21和MS11由图5可知，在1.64GHz到1.66GHz之间，MS11小于-15dB 满足要求。但MS21 为-3dB，小于要求的-0.2dB。4 结束语微波滤波器在微
11、波中继通讯、卫星通讯、雷达技术、电子对抗及微波测量仪器中都有广泛的应用。设计微波滤波器的传统方法大多是靠查图表和曲线来完成，不但工作量大，而且设计精度不高。用 Ansoft 公司的Serenade 8.7 进行优化设计，既减轻了设计者的劳动强度，缩短了设计周期，又提高了设计精度。本文结合实际的工程要求，利用计算机优化设计，制作了中心频率为1.648GHz的平行耦合带通滤波器，通过调试，达到了设计要求。参考文献1 Reinhold Ludwing，Pavel Bretchko 著，王子宇等译射频电路设计理论与应用电子工业出版社，2002：52 顾墨琳著微波固态电路设计机械电子工业部第十四研究所，
12、1989：1Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and throu
13、gh the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sk
14、y, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot
15、 tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of
16、 space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical strai
17、ght line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have th
18、at same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cl
19、eaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission cont
20、rol as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limite
21、d cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial a
22、irliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll
23、 back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like di
24、ving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the
25、more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) mai
26、n chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumga
27、rtner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
