七宗罪

如果 任由 嫉妒 贪婪 懒惰 愤怒 色欲 暴食 傲慢
这所谓的人类的七宗罪 放肆 的侵蚀 自己
不加批判 不加苛责 不加赞扬 也不加阻止
那么这个人将会变成什么样了 我很好奇

最温柔的无情

或许 孩子 最大的敌人 是 父母
反过来亦是
因为 彼此互相束缚着
夺走了自由的 同时 却不能呐喊
只因这是最温柔的无情--爱

动力

我没有什么大梦想要追求。
也没有什么大目标要达成。
但是，看着美丽的世界，偶尔还是会有小小的憧憬，还是会悸动于大家完成梦想的那一刻。
热血啊~~gambateh min nasann~~

最近喜欢得紧的一部作品

《钢之炼金术师--Fullmetal Alchemist》

栋笃笑

终于等到黄子华的栋笃笑，就在2013年1月5号。不幸的是，这次的时间是在考试周，必须做出妥善的时间安排才行了，愿这不是取舍的问题^^
之后要安排住宿与交通，希望一切顺顺利利，嘻嘻~~

               哇，很期待哦~~haah~~

选择与承担

每一个选择，都是你自己的事。
你要求自由，于是你得承担后果。
要多大的自由，则需要有承担多大责任的勇气。
要多大的成果，于是需要有承担多大努力的觉悟。
而你准备好了吗？

太迟

别嫌太迟 别怕愚蠢
或许 只不过是头脑的陷阱 为了阻止你知道

发泄

我其实 不过想搞懂一个题目
但是 要搞
就需要有背后的理论支撑
而我最缺的是这个
于是 去翻书 结果到最后 我却忘了自己要搞懂的到底是什么
饶了一大圈，真想尖叫！

FYP: example

Example:

Solution:

Cos2 θ= 0.707
θ= cos-1 surd 0.707
  =32.7º≈33º

HPBW=2θ=66º

 reference: antenna for all application  3rd edition : (John D. Kraus & Ronald J. Marhefka)

FYP: Transmitting and Receiving Antenna

Transmitting and Receiving Antenna

a) Radio or wireless communication link with transmitting antenna

b) Receiving antenna. The receiving antenna is remote远程 from the transmitting antenna so that the spherical wave radiated by the transmitting antenna arrives as an essentially本来 plane wave at the receiving antenna.

Schematic representation of region of space at temperature T linked via a virtual transmission line to an antenna.

It’s to be noted that the radiation resistance, the antenna T, and the radiation pattern are functions of the frequency. In general, the patterns are also functions of the distance at which they are measured, but at distances which are large compared to the size of the antenna and large compared to the wavelength, the pattern is independent of distance. Usually the patterns of interest are for this far-field condition.

reference: Antenna for all application third edition (John D.Kraus & Ronald J. Marhefka)

FYP2: basic antenna parameter

Antenna basic

Aperture family: effective and scattering

Lobe family: main, side, back, grating刺耳

Beam width: directivity, gain

Antennas are three-dimensional and live in world of beam area, steradians, square degrees, and solid angle. Antennas have impedance (self and mutual). They couple to all of space and have a T measured in K. Antennas have polarization: linear, elliptical, and circular.

Basic Antenna Parameters

Radio antenna: structure associated with the region of the transition between a guided wave and free space wave, or vice versa. Antenna converted electrons to photons or vs.

(Photon = quantum unit of EM energy equal to hf, where h=Planck’s constant=6.63x10-34 Js, f=frequency, hz)

All antenna type involve same basic principle that radiation us produced by accelerated (or decelerated) charge.

Basic eq:

dIL= Qdv

I=time charging current, , L=length of current element, m
Q=charge,C,   v=acceleration of the charges, ms-2

Thus, time changing current radiates and accelerated charge radiates. For steady state harmonic variation, we usually focus on current. For transient or pulses, we focus on charge. The radiation is perpendicular to the acceleration, and the radiated power is proportional to the square of dIL or Qdv.

An antenna is a transition device, or transducer传感器，between a guided wave and a free space wave, or vs.

From the circuit point of view从电路的角度来看, the antenna appear to the transmission lines as resistance,Rr , called the radiation resistance. It’s not related to any resistance in the antenna itself but is a resistance coupled from space to the antenna terminals.

In the transmitting case, the radiated power is absorbed by objects at a distance: trees, buildings, the ground, the sky and other antennas. In the receiving case, passive radiation from distant objects or active radiation from other antennas raises the apparent表面上 temperature of Rr.

For lossless antennas, this temperature has nothing to do with the physical temperature of the antenna itself but is related to the temperature of distant objects that the antenna “looking at”. In this sense, a receiving antenna (and its associated receiver) may be regarded as a remote-sensing远程传感temperature measuring device.

 Pattern

Rr and T are simple scalar quantities. The radiation pattern, on the other hand, are three dimensional quantities involving the variation of field or power (proportional to field squared) as a function of the spherical coordinates θ and phi.

The completely specify the radiation pattern with the respect to field intensity and polarization requires three patterns:

1) the θ component of the electric field as a function of the angles θ and phi (vm-1)

2) the phi component of the electric field as a function of the angles θ and the phi (vm-1)

3) the phases of these fields as a function of the angles θ and phi (rad or deg)

Three-dimensional field pattern of a directional antenna with maximum radiation in z-direction at θ=0º. Most of the radiation is contained in a main beam (lobe) accompanied by radiation also in minor lobes (side and back). Between the lobes are nulls where the field goes to zero. The radiation in any direction is specified by the angles θ and phi. The direction of the point P is at the angles θ=30° and phi=85º.

Any field pattern can be presented in three-dimensional spherical coordinates, as in Fig.2-3, or by plane cuts through the main lobes. Two such cuts at right angles, called the principal plane patterns (as in the xz and yz planes on Fig.2-3) may be required but if the pattern is symmetrical around the z axis, one cut is sufficient.

Figures 2-4a and 2-4b are principal plane field and power patterns in polar coordinates. The same pattern is presented in Fig.2-44c in rectangular coordinates on a logarithmic, or decibel, scale which gives the minor lobe levels in more detail.

The angular beam width at the half-power level or half-power beam width (HPBW) (or -3dB) and the beam width between first nulls (FNBM) as shown in Fig.2-4, are important pattern parameters.

Normalized field pattern and Power Pattern

NFP: E(θ,phi)n= E(θ,phi)/E(θ,phi)max (dimensionless)

The half-power level occurs at those angles θ and phi for which E(θ,phi)n = 1/surd 2= 0.707.

Pattern may also be expressed in terms of the power per unit area. Normalizing this power with respect to its maximum value yields a normalized power pattern as a function of angle which is a dimensionless number with a maximum value of unity.

NPP: P(θ,phi)= S(θ,phi)/S(θ,phi)max

Where

S(θ,phi) = Poynting vector

The decibel level is given by

dB = (10 log Pn (θ,phi)

Two dimensional field, power and decibel plots of the 3-D antenna pattern of Fig.2-3/ taking a slice薄片through the middle of the 3-dimensional pattern of Fig.2-3 results in the 2-dimensional pattern at (a). It is a field pattern (proportional to the electric field E in V/m) with normalized relative En (θ) =1 at θ=0º. The half power beam width (HPBW) = 40º measured at the E=0.707 level.

The pattern at (b) is power slot of (a) (proportional to E2) with relative power Pn=1 at θ=0º and with HPBW =40º as before and measured at the Pn=0.5 level.

A decibel (dB) plot of (a) is shown at (c) with HPBW = 40º as before and measured at the -3dB level. The first lobes are shown at the -9dB and second side lobes at -13dB. Decibel plots are useful for showing minor lobe levels.

reference: antenna for all application third edition (John D. Kraus & Ronald J. Marhefka)

FYP 1: history of antenna

First of all, some introduction to the antenna is great need since I don't really have the basic. I think my lecturer  was lounging at me every time when I asked some related questions even though he did not express out. However, this is really not our fault. We have only learned antenna through the laboratory, not the proper lecture. Hence, it's not surprising that I am so noob.

Well, let start my FYP project.

History of the antenna: Hertz and Marconi invented. Antenna seem to have a bewildering 使人困惑 的, but all operate according to same basic principle of EM.

Antennas are our eye and ear on the world. They are links with space. They are essential基本的, integral part of our civilization. Antenna has been around for long time, millions of years, as the organ for touch or feeling of animals, birds, and insects. Last 100 years, acquired a new significance as the connecting link between a radio system and the outside world.

1^st   antenna built by Heinrich Hertz. In 1886, he assembles apparatus we would now describe as a complete radio system operating at meter wavelengths with an end-loaded dipole as the transmitting antenna and a resonant square-loop antenna as receiver.

Receiver: resonant square-loop antenna; transmitting: end-loaded dipole.

His invention remained a laboratory curiosity until 20 years old Guglielmo Marconi went to add tuning circuits, big antenna and ground systems for longer wavelengths, and was able to signal over long distances. In mid –December 1901, he startled the world by receiving signals at St.Johmx, Newfoundland from a transmitting station he had constructed at Poldhu in Cornwall, England. A year later, he began regular transatlantic message service in spite of a suit诉求 by the Cable Company for infringing侵害 on its monopoly of transatlantic messaging.

With the advent of the radar after World War II, centimeter wavelength became popular and the entire radio spectrum opened to wide usage. Our probes 探查with their array一系列 of antennas have visited the planets of the solar system and beyond, responding to our commands and sending back photographer and data at centimeter wavelengths even though it may take over 5 hours for the signal to travel one way. And our radio telescope antenna operate at millimeter to kilometer wavelengths receive signal from object to distant that it has taken more than 10 billion years for the signal to arrive.

After Heinrich Hertz 1^st demonstrated radiation from antenna, it was called wireless. And wireless it was until broadcasting began about 1920 and the word radio was introduced. Now wireless s back to describe the many systems that operate without wires as distinguished from radio, which to most persons now implies AM or FM.

Dimensions规格 and Unit

Dimension defines some physical characteristic such as length, mass, time, velocity and force.

Fundamental 6 dimension: length, time, mass, luminous intensity, electric current, temperature.

Secondary dimension: other dimension

Unit: standard/ reference by which the dimension can expressed numerical. For eg, the length (dimension) of a steel rod might be 2 meters, and its mass (dimension) 5 kilograms.

Fundamental and Secondary Unit

Fundamental/base unit: Unit for fundamental dimension. SI unit (International System of units, SI unit are used. The six fundamental units are meter, second, kilograms, candela, ampere, Kelvin

The unit for other dimensions are called secondary or derived units and based on these fundamental units.

   

Reference: Antenna for All Aplications third edition (John D.Kraus & Ronald J. Marhefka)

韩文（三）

韩文的母音很奇怪，还有double的。
以下就是double vowel
ㅐ ae（嘴形长一点）
ㅔ e  （发音是a,但是短的发音：edisi）
ㅒ ye（发音：ye）  
ㅖ ye（发音：ye）
ㅘ wa
ㅝ wo
ㅙ wae（发音：where 第二声，上喉发音）
ㅞ we（发音：where 第二声，较短，下喉发音）
ㅟ wi（发音：wi）
ㅢ eui（发音：很快的eu+i）
ㅚ we（发音：也是where）


目前，还是背不到double vowel。
而母音有double,子音当然也有double。
ㄲ      kak（没有吐气）
ㅃ      ba（第四声） 
ㅉ      ja （第四声）
ㄸ      da（第四声）  
ㅆ      sa（第四声）

之前也提过了，韩文字是由vowel + consonant 组成的。因此double vowel的韩文字是：
애（ae）、에（e）、얘（ye）、예（ye）……

那么，学了double vowel 和double consonant 后，就来学写自己的名字吧。需要注意的是，韩文字是依据发音拼写的，因此可能会和英文字母有出入。

例子：
kajang（카장）或（까 장）都行。
lim man chew（림먼주lim man jeo）

我的名字：
lim man shi （림먼리）

话说，在课堂上写自己的名字时，闹了笑话，被老师笑说自创了文字。
原因是我的名字里，shi "h"在韩文里是没有发音的（下次解释为何没发音），但是我不知道，结果把名字写成（ㄹ히），让老师特地在前面跟大家说。

练习其他人的名字
其他人的名字：
lim man ping （림먼펭）
lim man ching（림먼칭）
lai jin hui （라이진후이）

挺好玩的。

韩文比较麻烦的地方是它的读音，需根剧规则来发音。因此，之前认为只要懂得读音就会写韩文不太正确，因为不同的字读音可能相同，但是文字却不同。
另外，还有变音字（当子音碰上母音）或省略音（如上面提 的h），下回再谈了。

自由

你口中所追求的自由
到底建立在什么之上？