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1dB压缩点与三阶交调点的关系
2008-03-01
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记得上学期做LNA仿真的时候，发现1dB压缩点和三阶交调点之间有10dB左右的关系。当时没有仔细考虑两者之间的关系，以为没有关系。今天看到某书上写到：1dB压缩点对应的输入功率比三阶教条点对应的输入功率低9.64dB。既然精确到x.xx，那么肯定有一些情况了。于是花了一些时间来推导繁琐的三角函数，果然，两者之间是有9.64dB的差值。不过，这个结论一定是建立在如下这个基本假定：PA的非线性是三阶幂级数近似。实际上，大多数PA用三阶幂级数近似已经可以获得相当精确的模拟。一般情况下，实际PA的1dB压缩点对应输入功率小于三阶交调点对应输入功率10~15dB。这里是一个文档《1dB压缩点与IIP3的关系》，其中有详细的推导过程。放在这里，希望对大家有用。
http://richard.blogbus.com/files/12060241620.pdf
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早上献血。本来是我和詹师兄两个人，可是医生说只能上一人，我让给詹师兄。没想到詹师兄瘦骨嶙峋却是个“三高”人物，所以只好让我这个替补上了。400ml献血，换来一对食品和1k人民币--无偿献血？验血的空闲，拿起献血读本看到：献血前两餐不要吃肥肉，并且要保证足够睡眠，否则可能导致转氨酶偏高，血样不合格。想：坏了，昨晚和老猪出去吃了一堆羊肉串，半夜1点半才睡，不会有问题吧？呵呵，结果证明我实在是太强悍了，照样合格。整天除了感觉针口还有点疼之外，根本没有发现什么不适。鉴于我无比强壮的身体，大拙同学建议我献400ml XX，然后去申请吉尼斯。考虑一下，嘿嘿。
***
阿丁和小汪都顺利拿到了美国大学offer。阿丁去的是佛罗里达州立大学，和大拙同学再度成为校友；小汪去的则是德州农工。小汪一心想成为汪因斯坦，所以还是申请物理专业--想起来，德州农工的模拟电路比较强。祝福大家都有好的前途，包括我。
***
“蒹葭苍苍，白露为霜，所谓伊人，在水一方 。”
......
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单车减肥 PA导通角波形分析
2008-02-28
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晚上又去骑单车，满身大汗，真是酣畅淋漓。找到了单车是减肥好办法的证明：
Did you know you burn the most calories when you exercise your legs? That’s because they’re home to your body’s biggest muscle groups; the larger the muscles, the more energy it takes to move them. Any time you lift, bend or otherwise use your legs, you’re burning calories.
来自美国著名生活健康网站。每次骑完单车下来，地上都是一大滩汗水，很爽。洗完澡之后就更爽了。
***
这几天看Steve C. Cripps 《RF Power Amplifiers for Wireless Communications》2nd Edition。第二版比第一版有了很多丰富和改进，包括了更多的内容。对Cripps佩服得五体投地了，从前对于PA的很多模糊了解，现在越来越清晰了。基本上想做PA，只看这一本就足够了，真的很经典。清华大学池保勇写的那本《CMOS射频集成电路分析与设计》中PA一章，几乎是完全翻译抄袭Cripps这本书，不过翻译得很不错。Cripps还有另外一本经典的书，《Advanced Techniques in RF Power Amplifier Design》，还没有来得及拜读。读书的时候，做了一些简单的笔记，等读完了放上来与大家共享一下。这里共享一个小的总结《功率放大器导通角波形分析》，基本上也是抄袭Cripps著作，只不过变成中文，与大伙分享，希望有用：
http://richard.blogbus.com/files/12042104410.pdf
***
早上洗脸的时候，光顾着和阿东说话，结果拿牙膏当洗面奶用了。知道感觉脸上很凉才发觉，糗事又一桩。
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牛牛涨价了，原来10块的盖饭，过年之后就变成了15块、16块。
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明天献血。想起在USTC的时候，和赖凯屁颠屁颠跑到四牌楼献血，然后每人拿着两盒牛奶屁颠屁颠逛街，瞅美女......刚才在宿舍翻箱倒柜找到了我的献血证，我的血呀。
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中国的银行
2008-02-27
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柜员机取出假钱--->银行无责
网上银行被盗--->储户责任
柜员机出现故障少给钱--->用户负责
柜员机出现故障多给钱--->用户盗窃，被判无期
银行多给了钱--->储户义务归还
银行少给了钱--->离开柜台概不负责
广东开平银行行长贪污4亿--->判12年
广东老百姓多取ATM机17万--->判无期____________________________________________________
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I will survive
2008-02-25
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I Will Survive
At first I was afraid I was petrified
Kept thinkin' I could never live without you by my side;
But then I spent so many nights
Thinkin' how you did me wrong
And I grew strong
And I learn how to get along
And so you're back from outer space
I just walked in to find you here with that sad look upon your face
I should have changed that stupid lock
I should have made you leave your key
If I'd've known for just one second you'd back to bother me
Go on now, go walk out the door
Just turn around now
('cause) you're not welcome anymore
Weren't you the one who tried to hurt me with goodbye
Did I crumble
Did you think I'd lay down and die?
Oh no, not.I. I will survive
Oh as long as I know how to love I know I'll stay alive;
I've got all my life to live,
I've got all my love to give and I'll survive,
I will survive.It took all the strength I had not to fall apart
Kept trying' hard to mend the pieces of my broken heart,
And I spent oh so many nights
Just feeling sorry for myself. I used to cry
But now I hold my head up high
And you see me somebody new
I'm not that chained up little person still in love with you,
And so you feel like droppin' in
And just expect me to be free,
Now I'm savin' all my lovin' for someone who's lovin' me
Go on now, go walk out the door
Just turn around now
('cause) you're not welcome anymore
Weren't you the one who tried to hurt me with goodbye
Did I crumble
Did you think I'd lay down and die?
Oh no, not.I. I will survive
Oh as long as I know how to love I know I'll stay alive;
I've got all my life to live,
I've got all my love to give and I'll survive,
I will survive.
Go on now, go walk out the door
Just turn around now
('cause) you're not welcome anymore
Weren't you the one who tried to hurt me with goodbye
Did I crumble
Did you think I'd lay down and die?
Oh no, not.I. I will survive
Oh as long as I know how to love I know I'll stay alive;
I've got all my life to live,
I've got all my love to give and I'll survive,
I will survive.
I will survive.It took all the strength I had not to fall apart
Kept trying' hard to mend the pieces of my broken heart,
And I spent oh so many nights
Just feeling sorry for myself. I used to cry
But now I hold my head up high
And you see me somebody new
I'm not that chained up little person still in love with you,
And so you feel like droppin' in
And just expect me to be free,
Now I'm savin' all my lovin' for someone who's lovin' me
Go on now, go walk out the door
Just turn around now
('cause) you're not welcome anymore
Weren't you the one who tried to hurt me with goodbye
Did I crumble
Did you think I'd lay down and die?
Oh no, not.I. I will survive
Oh as long as I know how to love I know I'll stay alive;
I've got all my life to live,
I've got all my love to give and I'll survive,
I will survive.
I will survive.***
晚上在浩沙骑单车，又听到这首振奋人心的歌。之前就好几次听到这首歌，但是不知道名字，今天仔细听了一下，听清楚了“I will survive”。刚才Google之，呵呵，终于给我找到了。差不多七分钟长，节奏感很强，踩着鼓点骑车，正好照顾到了各个片段。尤其是后来的“啦...啦...啦...”，很让人有打架或者奔跑的欲望--呵呵，我是暴力狂。今年第一次踩单车，出了很多汗，然后美美得洗了一个热水澡。我最喜欢做的事情，就包括出汗和洗澡。我还和婷说，如果浩沙有一个很安静、干净又舒适的空间供大家出汗、洗澡之后睡觉就完美了。被批。
***
管管同学收到了耶鲁大学和欧洲微电子中心(IMEC)的offer，刘亮师兄收到了瑞士的offer，江哥签了14所。管管同学是很让人敬佩的，已开始就很认真地准备了GRE和TOEFL，各门功课也很用功，平均分超过了90分，科研上也非常出色，发表了几篇高质量的paper。婷儿一语道破天机：有目标的人真好！是啊，那么，我的目标是什么呢？脸红。
***
“浩浩愁，茫茫劫，短歌终，明月缺。郁郁佳城，中有碧血。碧亦有时尽，血亦有时灭，一缕香魂无断绝！是耶非耶？化为蝴蝶。”
陈家洛。香香公主。
......
***
大家不妨听一下右边照片下的歌，《纯恋歌》，虽然是鬼子所唱，但是很好听。
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Life -- copied
2008-02-24
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How do you think of life? Life is easier than you think. All you have to do is: accept the impossible, do without the indispensable, bear the intolerable and be able to smile at anything.
Life is just life. No easier or tougher. Make impossible possible, smile at happiness, cry at despair, age with time, die with nothing in hand but memory in mind.
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最后的疯狂
2008-02-21
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天还没有暗，北京这座古老的都城就开始了沸腾。只因为今天是元宵佳节，明天开始，北京城又将恢复一年的沉寂--没有烟花爆竹。连绵不绝的鞭炮声充斥耳畔，窗外也不断可以看到闪闪的亮光。不由得想起了从前在家里过年放鞭炮的情景。农村孩子没有什么好玩的烟花，只是到处扔一些散鞭。那时候，大年初一早上吃过早饭就把一大把散鞭揣在口袋里，点上一支香，和大伙一起在不大的村子里到处转悠，不住地放鞭。呵呵，已经很多年没有放鞭炮了，而且发现现在的小孩过年也不怎么放了，大家都有了高级的玩意，譬如手机、闭路电视和网络，还有谁去理那些劈劈啪啪的东西呢？不过在这个大都市里，鞭炮确实很新鲜的玩意。大街小巷里的烟花店铺生意着实不错，到今天更加大打促销牌，婷儿晚上说下班的路上看到很多烟花店都在打五折，有很多市民哄抢。晚上在办公室，外面的鞭炮声不绝于耳。但是，急促的火警声和救护车警报也响了好几遍。疯狂的人们，总是会给这个节日添上一些冷冷的色彩。Anyway，一年又过去，一年又来到，爆竹声声带给我们更加崭新的世界。祝愿一切都好。
***
今天和宗楠两个人骑着车把大半个北城都转了一边，从所里出发，到了小西天，然后去了阜成门，西直门，绕到皂君庙，再到小西天，去了马甸的中国茶城，最后在折腾回来。复印了两本书，买了一双鞋，宗楠买了一包铁观音。在福建茶商的铺子里，主人为我们泡了正宗的安溪铁观音，我也人模狗样地学着人家高雅了一番。铁观音味道很是不错，可惜我是个粗人，不懂个中滋味。不禁想起那时在海螺沟和我们一路同行的三位福建老驴，他们三个无论到哪里都随声带着茶具和铁观音，少有空暇就给大家表演茶艺，请大家尝他们的铁观音。他们都是福建的茶商，都在泉州开有挺大的铺子，只是他们天性爱玩，一年之中倒有大半年在玩，其余时间则在玩的路上，真正打点铺子的时间很少。我觉得他们最有趣的一件事情就是，每到收茶的季节，就相约了，开着越野，带着帐篷直接住到深山老林的茶农家里收茶。即使工作，也是兴趣，这种事业谁不喜欢？不由又叹息世人诸般无奈。
***
“十万军声半夜潮。”
“情深不寿，强极则辱，谦谦君子，温润如玉。”
“以水佐功者明，以火佐攻者强。”
......
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肥肥辞世。
陈冠希宣布永久退出香港娱乐圈，并向世人道歉。这件事情，也许该告一段落了？老猪搜罗来了所有艳照--那是相当艳，各位女星平时优雅庄重，但是私房之中......不好措辞了，总之这些照片与AV女优所作之事无二般。可能大部分网友都没有看到这些露骨的照片，我看了也是完全震惊，说不出话来。整件事情，陈冠希也是受害之人，真正的罪魁祸首是那个揭露隐私之人。明星，衣着光鲜，那么他们的背后是什么？众人都有猎奇之心。有人说：其实明星们的私人生活真的尤比常人不堪，君不见，xxx吸毒，xxx同性恋，xxx...也许吧，或也许只是被无聊大众拿显微镜检视的结果。
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采用碳纳米管互连的首颗1GHz芯片面世
2008-02-21
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From: EETimes.com
PORTLAND, Ore. — Copper interconnections on CMOS could become a bottleneck as future chips get faster. One solution could be harnessing carbon nanotubes, which have much higher electron mobility. Until now, however, researchers have been unable to perfect a method for coaxing the nanoscale carbon tubes into the correct positions on chips.
Now, one group thinks they have the answer.
The world's first CMOS circuit using nanotubes as an interconnect was recently designed at Stanford University, in cooperation with Toshiba Corp. I t was fabricated by Taiwan Semiconductor Manufacturing Co. Ltd. (TSMC). The 256 ring oscillators on the 11,000- transistor chip ran at 1 GHz, rivaling the speed of other advanced CMOS chips (the iPhone's processor runs at 700 MHz).
"A lot of research labs are working toward using nanotubes to interconnect chips since they have higher electron mobility than copper, and can be grown much smaller. But ours is the first working digital chip to run at commercial speeds of 1 gigahertz," said electrical engineering professor Philip Wong, a professor of electrical engineering at Stanford.
' The chip was designed as a array of ring oscillators with one missing connection. By adding a nanotube to complete the circuit, the chip demonstrated the viability of nanotubes as a substitute for copper wiring. The nanotubes used were multiwalled types measuring five microns in length and from 50 to 100 nanometers in diameter (about the same size as copper wires). Future versions could use single-walled nanotube wires as small as 1 nm in diameter. The chip measured one hundredth of a square inch.
To simplify fabrication and testing of the ring oscillator array, multiplexing circuitry was provided on the chip so that individual ring oscillators could be separately addressed. The nanotubes were placed in the gap to complete the circuit of a ring oscillator using a novel method that floated a solution over the chip suspending thousands of free-floating nanotubes.
Then an alternating current was supplied to the ring oscillators, which attracted the floating nanotubes to precisely the correct gaps in the circuitry. Once a nanotube snapped into place to bridge a particular gap, the AC signal was turned off for that ring oscillator. The solution was then removed and the chip allowed to dry off.
The work was performed with the help of Stanford University electrical engineering doctoral candidate Gael Close, Toshiba engineers Shinichi Yasuda and Shinobu Fujita along with engineeer Bipul Paul of Toshiba America Research (San Jose, Calif.).
The research was funded by Toshiba, the Interconnect Focus Center, Semiconductor Research Corp. and Close's Intel Graduate Fellowship.
中文版： http://www.eetchina.com/ART_8800505684_480201_NT_fabb7d6f.HTM
* 什么是碳纳米管？
1991年日本NEC公司的饭岛纯雄(Sumio Iijima)首次利用电子显微镜观察到中空的碳纤维，直径一般在几纳米到几十个纳米之间，长度为数微米，甚至毫米，称为“碳纳米管”。理论分析和实验观察认为它是一种由六角网状的石墨烯片卷成的具有螺旋周期管状结构。正是由于饭岛的发现才真正引发了碳纳米管研究的热潮和近十年来碳纳米管科学和技术的飞速发展。 按照石墨烯片的层数，可分为： 1) 单壁碳纳米管（Single-walled nanotubes, SWNTs）：由一层石墨烯片组成。单壁管典型的直径和长度分别为0.75～3nm和1～50μm。又称富勒管(Fullerenes tubes)。 2) 多壁碳纳米管（Multi-walled nanotubes, MWNTs）：含有多层石墨烯片。形状象个同轴电缆。其层数从2～50不等，层间距为0.34±0.01nm，与石墨层间距(0.34nm)相当。多壁管的典型直径和长度分别为2～30nm和0.1～50μm。____________________________________________________
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Power Amplifier Controllability
2008-02-19
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Mona M. Hella 《RF CMOS Popwer Amplifiers: Theory, Design and Implementation》
Implementing power amplifiers in CMOS technology is considered a major step towards the realization of a complete transceiver on-chip. Modern transceivers require means for adjusting the transmitted power over a finite range to further reduce power consumption and improve channel capacity. A low performance, short-range wireless standard such as the Bluetooth radio requires a high level of integration, and low cost that can onle be achieved using CMOS technology, together with means of controlling the output power up to 20dBm. In addition, power amplifiers are tyupically backed-off relative to their peak power and PAE points in order to meet the Linearity requirement of the system. The degree of back-off varies depending on the modulation scheme employed -- 0dB fro Gaussian-filtered minimum shift keying (GMSK) (GSM and DECT), 7dB for Pi/4DQPSK (IS-54 and PHS), 10dB for QPSK (IS-95) and 12dB for 16QAM are typical. Thus, adding efficient techniques for adjusting the output power level is considered a challenging issue to integrated power amplifiers.
Linear power amplifiers can have their power adjusted by the variation of biasing or dynamic variation of the load seen by the output stage (Doherty amplifier). The output power can be also be controlled through the variation in the input signal amplitude; this can be realized by having a variable gain amplifier (VGA) as a preceding stage. However a large dynamic range of output power requires a linear wide dynamic range variable gain amplifier which is usually power consuming and hard to achieve. Also this configuration suffers from a large reduction in efficiency at lower power transmission because the standing bias current at the output stage does not scale with the output power. This technique requires a very linear power amplifier for any kind of signal shaping at the input.
In non-linear power amplifiers, the input to the amplifier provides only timing information. Thus, the output power cannot be controlled through the variation in input signal amplitude as is done in linear or weakly nonlinear amplifiers. Instead, output power control can be realized effectively through a variable supply, implemented for example by a dc-dc converter. The losses in the DC-DC converter might casuse the effieciency to drop to reach that of a linear power amplifier's case. A new methodology based on switching a combination of power amplifiers in parallel is presented in some articales and represents an extension to the idea of Doherty amplifier to non-linear power amplifiers.
Richard: 关于PA的功率控制没有什么经验。我想具体做法可以采用两种办法：调制，反馈控制。调制包括对PA的供电电源控制，和对PA的输入信号功率进行控制，殊途同归达到控制输出功率的目的。反馈控制，其实他的实现也要借助于调制--检测输出功率水平，反馈到调制电路进行控制。以前做过一个输出功率检测电路，就是为了做输出功率控制--对检测线性度要求较高，譬如输出功率每增加3dB，检测电路输出电平增加0.1V。很多PA被设计成Lamination的结构，其中集成了几个die，如GaAs HBT的PA die，GaAs HEMT的RF Switch die，CMOS的Control Circuit die，针对不同的功能采用不同的工艺，然后封装在一起。现在RFMD，Skyworks，Anadigics，TriQuint都有了BiFET的工艺，那么，在不久的将来，也许Lamination即将消失，取而代之的是全集成的解决方案了。另外，这里再列一下PA线性化技术：
1. Feedforward;
2. Feedback;
3. Predistortion;
4. Envelope Elimination and restoration (EER);
5. Linearization using nonlinear components (LINC);
6. Bias adaption;
7. Doherty amplifiers.
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Power Amplifier Stability Issues
2008-02-19
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Mona M. Hella 《RF CMOS Popwer Amplifiers: Theory, Design and Implementation》
RF PA oscillation problems can be broadly categorized into two kinds; Bias oscillations, and RF oscillations. Bias oscillations occur at low frequencies, in the magahertz to VHF range, and are caused by inappropriate and unintentional terminations at those frequencies by the bias insertion circuitry, such as the addition of a large-value decoupling capacitors. The oscillations have little to do with the detail of the RF matching circuitry, where the RF blocking and decoupling capacitors become open circuit terminations at lower frequencies. RF oscillations, on the other hand, typically occur either in band or commonly out of band but still quite close to the desired bandwidth from the low frequency side. These latter kinds of oscillations are too common in single ended multi-stage designs, and their elimination will require modifications to the RF matching network topology and element values. Both kinds of instability can be analyzed effectively using the k-factor analysis. Although k-factor analysis assumes a linear two-port device, it is usually a satisfactory assuption to assume that RF oscillations in power amplifiers will more likely occur when the amplifier is backed off into its linear region, where the k-factor analysis is valid. In the case of deep class AB or B operation, it is necesary to increase the quiescent current to perform the stability analysis with a representative amount of gain. A simple way to test stability of the PA, is to run the entire circuit on a linear simulator, sweeping the frequency all the way down to dc.
Higher frequency instability will show up in a k-factor analysis of individual stages. Any single-ended design must show a k-factor greater than unity over the widest frequency sweep, extending from the low-frequency bias circuit range all the way up to the frequency at which the gain rolls off to lower than unity. Designing or midifying a circuit to obtain such a response for the k-factor typically will involve some sarifices in the in-band RF performance through the use of resistive elements, which will affect the efficiency of the PA.
Richard: 振荡的问题，在射频/微波功率放大器设计中司空见惯。往往，设计好的振荡器不振荡，设计好的PA却是很好的振荡器。这个问题，几乎每个射频工程师都曾遇到过，也感到非常头疼。最大的问题是，对于振荡的机理和解决方案，一直没有非常明确的认识。湖哥、江哥和泰哥他们，当然还有我，都被这个问题折磨过。湖哥曾经深层研究过振荡的问题，可惜当时我太懵懂，他的成果没有继承过来，遗憾万分！这里作者将振荡分为两种：Bias Osc. 和RF Osc. ，这也是业界普遍的认识。两者的表现主要是振荡频率的高低上，作者说得很明白，但是对于如何解决却没有说明。结合经验，我认为，低频振荡（可以说就是Bias Osc.）更好解决一些，办法当然focus on偏置电路，如在FET功放中，栅极串联电阻（就是作者说的through use of resistive elements），偏置线加磁环等等，实验证明非常有效。对于RF Osc.，我认为主要是射频接地不良导致寄生正反馈，其次还有匹配不良导致反射严重也会引起RF Osc.。解决办法，当然就是显而易见了。另外，在高频的功放模块设计中，腔体效应和空间耦合也会导致振荡产生，具体机理我完全无知。可以借助HFSS仿真模拟，解决办法则相对直接：结构设计上的挡板、独立Room设计，调试过程中吸波材料的应用等等。上次和RFMD的牛人聊天的时候说到振荡问题，我说了以上这些我的见解，可惜没有能得到指点，遗憾。
Instability occurs when some of the output energy is fed back to the input port in the proper phase so as to mack negative resistance appear at the output or input of the amplifier. Coupling from output to input occurs through capacitances within the active device and through external elements. Because the reactance of the feedback capacitance decreases with increasing frequency, the likelihood of unwanted oscillations is higher in RF amplifiers.
Class E: The usual k-factor stability definition does not actually have a meaning in the case of Class E amplifiers since the transistors in this case are acting as swtiches, while the definition of the k-factor is based on small signal analysis. The practical way to test stability in this case is to perform transient analysis using a step input located at various nodes and check that the output settles down to a fixed level within a short period of time.
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Dwight Howard -- Superman
2008-02-18
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今年全明星周末的扣篮王，德怀特-霍华德。这个家伙，是继奥尼尔之后的又一个具有娱乐天赋的大个子。身高臂长，弹跳惊人，再加上富有创意的动作，全明星的扣篮王是当之无愧。看看上面这幅图片，真的如飞天超人一般。
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Complex Precision.
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