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Oscillators for Communications Applications: Basic Operation and Available Types

Introduction

Oscillators lie at the heart of many electronic and communications systems that depend on accurate time measurement and coordination. They are used to stabilize time-frequency generators, which in turn provide carrier and pilot signals for electronic communication and navigation systems. Oscillators also provide the clock signals used by data processing equipment, as well as the reference signals for other special-purpose systems. The required accuracy and stability of oscillator output frequency depend on the application, ranging from about ±1000 PPM in the case of simple microprocessor clocks, to less than ±5 PPM for applications requiring very precise frequency control. In this article, we explore basic oscillator operation and oscillator types used in communications applications.

Basic Oscillator Operation

Fundamentally, oscillators consist of two sections: an amplifier section, and a feedback section containing a phase correction network.

Figure 1.0 - Basic Oscillator Configuration

For an oscillator to start and operate, two conditions must be met: (1), the gain around the circuit must be greater than unity; and (2), the signal leaving the phase correction network must be in phase with the signal applied to the amplifier network.

When the oscillator circuit is first energized, the only "signal" within the circuit is electrical noise. A component of this noise, at a frequency that satisfies the phase requirement for oscillation, propagates through the amplifier and feedback sections with increasing amplitude. This process is repeated until the gain of the phase-corrected signal is sufficient for steady-state oscillation. The exact frequency of oscillation depends on the phase condition, i.e., the phase must be equal to 2nwhere n=0,1,2,3.

The frequency of an oscillator changes from one moment to the next because of changes in the phase of the signal. Such changes may occur in any or all of the sections of the oscillator, and must be corrected to sustain a specific frequency. In theory, it is possible to incorporate some means of phase correction in all of the various systems within an oscillator circuit. Such an approach, however, would be costly and would increase the size of the oscillator package. The more common approach is to rely solely on the phase correction network. While there are several means by which the phase might be corrected, quartz crystals have proven superior. The reactance of a quartz crystal changes so dramatically with changes in phase that all other components in an oscillator circuit may be considered to be constant and invariable.

Types of Oscillators

The possibilities for oscillator type and design are nearly limitless; and in fact, crystal controlled oscillators are available in a multitude of types and sizes employing many different circuit designs. However, for the purposes of this article, crystal controlled oscillators can be grouped into four general categories:

Simple Packaged Crystal Oscillators (SPXOs) are commonly used as the clocking device for microprocessors. These are also common in automotive applications, where they are used to provide clock signals for the various computer controlled functions used in newer vehicles.

SPXOs are capable of providing frequency accuracy on the order of 10^-5 to 10^-4. They are generally available in standard frequencies from 1 MHz to 100 MHz, with frequency stability of ±100PPM. SPXOs do not incorporate any means to minimize the effects of temperature on the output frequency of the device. However, their low cost makes them an ideal choice for applications, including most computers, in which temperature variation is minimal or for which greater accuracy and stability are not required.

SPXOs are available with a wide range of output capabilities. They are available in both pin-through and SMD configurations; they range in size from 21mm x 14mm x 6mm to 5mm x 3.2mm x 1.5mm. Typically, pricing for SPXOs is in the range of $0.90 each, in quantities of 5000.

Voltage Controlled Crystal Oscillators (VCXOs) are often used in PLL (Phase Lock Loop) applications. They provide a means of controlling the output frequency over a narrow range, typically by using a varactor diode as a tuning capacitor. VCXOs come in packages sized 14mm x 10mm x 3mm and in through-hole and SMD configurations.

VCXOs offer frequency accuracies on the order of 10^-6 to 10^-5. Frequency range is generally from 1 MHz to 30 MHz. These are tight tolerance oscillators whose frequency stability is ±50 PPM and frequency pullability is ±100 PPM. VCXOs are available in HCMOS and TTL outputs, and their phase noise is usually -125 to -130 dBc/Hz. Pricing is typically around $4.00 each, in quantities of 5000.

Temperature Controlled Crystal Oscillators (TCXOs) are used in portable telephones, cellular phones, communications equipment, cellular radios, and in aerospace and two-way radio communications. Because they are available in low voltage (3.0 VDC format), TCXOs are ideal for use in hand held, battery powered communications devices. These oscillators correct the output frequency against the effects of temperature. Temperature compensation is usually effected by a temperature-sensing device that regulates a variable capacitor, with the result that at any temperature within the design range of the oscillator, the output frequency remains nearly constant. TCXOs are available with voltage control as well as temperature compensation; those incorporating both are known as VCTCXOs (Voltage Controlled Temperature Compensated Oscillator).

TCXOs are capable of frequency accuracies on the order of 10^-7 to 10^-6; available frequencies range from 1 MHz to 60 MHz. TCXOs usually have tight frequency stabilities, from ±1PPM to ±2.5PPM. They are available in through-hole or SMD configurations; package sizes range from 30mm x 30mm x 15mm to 11.4mm x 9.6mm x 3.9mm. Pricing for TCXOs usually starts at $4.00 each, in quantities of 5000.

Oven Controlled Crystal Oscillators (OCXOs) are often used in navigation systems as timing control devices, and also as precision frequency standards. These devices incorporate an oven that maintains the crystal at a constant temperature, or a temperature-regulated chamber that houses both the crystal and the oscillator circuitry. By maintaining the frequency-controlling element at a steady temperature, the effects of changes in the ambient temperature are eliminated. When used for frequency control in precision radio applications, OCXOs are superb; however, they are expensive, consume a lot of power, and may be quite large.

OCXOs are capable of producing frequency accuracies on the order of 10^-10 to 10^-8, and for some special applications, even tighter. They also provide the tightest frequency stability of all oscillator types. However, OCXOs are specialty items, not generally available from most frequency control product suppliers. Pricing for OCXOs is roughly $250 each, in quantities of 10.

In this article, we have introduced the four basic oscillator types used in communications and other electronic applications. While a number of configurations and modifications are possible for each of the basic designs, the rationale for selecting a specific oscillator type for a specific application is based on the general attributes discussed here.

Uses of Transistor

In 1956, the Nobel Prize in Physics went to three American Physicists, Walter Houser Brattain, John Bardeen, and William Bradford Shockley. These physicists designed the first transistor in 1947, opening the doors to transistor radios, space flight, hearing aids, amplifiers, switches and computers. According to the Nobel Prize website, today's transistors are smaller than a strand of human hair. There are many uses of transistors and some are likely top secret.

1. Amplification

   • Amplifiers use transistors to amplify sound. Microphones, guitars, keyboards and electronic drums use the transistors to send out electronic sound.

   Switching

   • Switches turn on and off with the use of transistors. Switches can be found on amplifiers, airplanes, automobiles, houses, lamps and radios.

   Computers

   • Many tiny transistors work within a computer to calculate and transmit binary codes to other transistors. The transistors work as a group called an integrated circuit.

   Hearing Aids

   • Tiny transistors help people with hearing loss hear. The tiny transistors amplify sound at an adjustable level to the hearing aid owner.

   Radios

   • Transistors helped bring personal radios to many people in the 1960s and helped improve communication.

   Space Exploration

   • The improvements and new uses for transistors helped the cause of space exploration. With its use in computers, communications and switches, the transistor made it possible to launch humankind to the moon, and set into the planet's orbit large telescopes to help with the study of the universe.

Beautiful childs

 

How Do I Know I'm in Love

Many men and women of all ages are postponing marriage because of their fears of choosing the wrong person and making a lifelong mistake. Since most important decisions in life are made with incomplete information, choosing the wrong partner is always a possibility. People can hide their worst behavior-from themselves as well as their partners. Here are some relationship tips and relationship and marriage advice about how to know you are in love and whether the person is right for you. But remember, this relationship advice is only a guide, and, although using it cannot guarantee happiness, it can increase your chances of choosing wisely.

1. You are both over 21. When one or both partners are under the age of 21, the chance of divorce or unhappiness increases. However, there are couples who met in high school or earlier and have long-term, mutually satisfying relationships!

2. Before you get married, you have dated for around two years. The brain's "love chemical" of oxytocin and the brain's dopamine levels are elevated when you feel you are in love. This elevation can last up to about two years. No wonder marriages fail frequently after two years! Wait until you are no longer in "brain la-la land" and see what your relationship is like.

3. You have been with your partner through good times and bad. See if he or she is still in love with you and needs and wants you during ups and downs. A person might cling to someone supportive during down times and then want a different kind of relationship when times improve-or vice a versa. Get to know your partner's coping skills-or lack of them!

4. Falling in love during "normal enough" life experiences is a "cleaner start." Ideally, you and your partner should know yourself, establish a career identity, have lived on your own and have a good relationship with family members-or have made inner peace with them. Falling in love during only rough times can increase poor choices of partners. For example, the death of a parent or other important caregiver can propel a person to hasten love and commitment-sometimes to the wrong person.

5. In general, the total number of years you have been dating before getting married is around 3-5 years. Of course, there are exceptions such as finishing school, living far apart, illness, mourning or armed forces commitments. However, during the course of "normal-enough" life events, the longer the dating or living together without commitment, the greater the chance of relationship unhappiness.

6. You feel good about yourself and how you act in the relationship, and you feel good about your partner. Marital research shows that partners who respect each other tend to have happier marriages. A good relationship should bring out the best in both of you.

7. Neither one of you frequently uses criticism, sarcasm, heated arguments, nagging or withholding love, affection and approval as main communications styles. Criticism and withholding positive relationship actions are often predictors of marital unhappiness, according to long-term research. Loving relationships bring out the best in each other, and partners want to help each other.

8. Neither one of you uses physical, verbal or sexual abuse. Do not tolerate physical violence or sexual abuse.

9. You both share key values and interests, passion and commitment to each other, sense of humor, have good problem-solving skills and "complete each other" through some complimentary characteristics. Studies in long-term marriages where both partners report happiness emphasize the importance of these aspects. You don't have to share all interests or all values, but you should know what's most important to you. For example, it's best to settle issues about religion, children and lifestyle before you get married.

10. Don't get married with problems, in the hopes of resolving them later. It's best to solve major issues before you get engaged.

chitika

The start to making more money on your webpage is finally here with the Chitika. If you plan on having double the profit on your website you need to know Chitika is one way to do it. The Chitika is one thing that provides you with pay per click ads that’s reliable and safe. There not a scam what so ever and provide the money profits like Google Adsense. If you plan on using Chitika you should know it’s easy to sign up for just like Google Adsense.

The ads you can put on your websites through the chitika can be related or non-related items that’s on your web pages. The next step is to make sure the websites going to be perfect for using Chitika. The best way to find out is the amount of traffic that’s found on the website. The high traffic will allow your ads to be clicked on and allow your other affiliated programs to be noticed. If you plan on finding out how to get your website to the top and high levels of traffic then you should know the first steps to SEO. The SEO can be easy done through article content. The chitika needs to be clicked on in order to have money accumulate.

When you first get the Chitika ads on your website you should know it’s the start to making a successful website. To those that make websites and sell them you should know it’s really easy to make sells when you tell the buying about chitika. The chitika can be found all over the internet through online reviews and also found on many forums as well. The importance of having a high traffic website is to make the profits you want. The profits you need in order to make more websites to sell.

The selling of websites is actually very profitable if you make the right ones. When you make one that uses Google Adsense and Chitika you know it’s making the money you want. Also before buying a website its important that’s its getting the traffic it needs. You plan on finding out how to make more traffic to your sight it’s important to hire a SEO writer that’s going to write some content for you. When you find out how the SEO works for your website you should know those following keywords will attach search engines attention. If you plan on having a SEO content make sure you don’t use to much key word density so you don’t get penalized.

The information that’s located in the blue link is a Chitika Review that will give you more information on Chitika.

How do they work?

- ads pay on a per click basis. The value of the clicks depends upon the product being featured.
- left in default mode – mini-malls are contextual ads (ie they look at your content and try to find ads that are relevant with it)
- ads can be set to be non contextual and to target specific keywords (this is helpful when it comes to running them in conjunction with Adsense – more information on this below).

How Profitable are they?

The terms of using eMiniMalls don’t allow me to share specific figures but I can share the following:

Overall – I’ve been beta testing mini-malls for 5 weeks now and am very happy with them. They don’t out perform Adsense for me yet – but my overall earnings with them for the month of September is more than a quarter and less than a half of my Adsense earnings for the month (regularly readers will be able to do some sums and come up with some approximate earnings there). Take into consideration that I don’t have them running on every blog I own and have not spent much time optimizing them yet and you’ll see that they have some real potential.

Cost per Click – Very good. The first day I added mini malls to and saw the amount that each click was paying I was quite surprised. They are considerably higher than my average click value on Adsense – some days they are 5 or 6 times higher. I’ve talked to a couple of other bloggers using them and they report similar click values. This is the definate strength of mini-malls.

Click Through Rate – The percentage of people clicking on eMiniMalls ads is considerably lower than what I get on Adsense. This is a bit disappointing and is probably for a number of reasons.

Let’s hope they can increase CTR in future.

Reports – I’ll emphasize that mini-malls are in beta at present so don’t expect too much in the reporting realm yet. At this stage they just update at the end of each day and give you some basic stats under the four headings of – Date, Impressions, Clicks and Revenue. These stats are what they call ‘unaudited’ – which means they haven’t taken anything off the total that they suspect to be click fraud or ‘dodgy’ clicks. They ‘audit’ you at this stage once per month (they have indicated that this will happen daily at some point in the future). I was only in the system for three days of last month but the auditing brought my ‘unaudited’ figures back by about 10% of what they were. Clicks are audited by some secret process that includes multiple or repeated clicks, traffic from bots and spiders as well as traffic coming from certain countries like China or Korea.

I’m not too impressed by the auditing feature. While I understand why its there I can see that this will be the cause of some tension between Chitika and Publishers. I’m sure Adsense has some sort of system in place that does something similar – but they are big enough to build it in as a real time feature so that publishers just don’t know what they lose. I’d rather not know the amount they take off for this than have it dangled before me to be taken away later.

I know from my conversations with Chitika staff that the reporting system will be undergoing significant improvements in the coming weeks and months.

Ad Formats – The currently offer 10 different size formats in some pretty standard sizes. I’ve recommended to them that they add a couple of new formats that I believe would be beneficial to bloggers but overall the options are pretty good. They also allow you to make some changes to the design of your ads by changing colors of borders, title and text to match your blog.

Payment – Payment is via Paypal in US Dollars at the start of every month – around 30 days after the end of the month you’re being paid for. You need to reach a minimum of $10 to get a payment.

Can Mini-Malls be used in conjunction with Adsense? – Most people I talk to about mini-malls asks this – it’s important as most bloggers want to use them in conjunction with one another.

I’ve talked to Google about this via email. The first email I got back from them said ‘no’ you can’t use them for two reasons:

1. They look too similar to Adsense Ads
2. They are contextual ads

I decided to follow the email up pointing out two things.

1. They actually don’t look like Adsense ads – they have a picture in them, tabs etc. I think the mistake Adsense made at first was in confusing mini-malls with Chitika’s other ads which do look very similar to Adsense ads.
2. You can actually disable the contextual element of the ads and plug in code that targets a specific product.

The email I received back said that they were sorry for making a mistake and that Chitika mini-mall ads can be used in conjunction with Adsense IF they are set to be non contextual.

I know of two others who have had this same conversation with Google with the same results.

English Sites only – at this point they are in beta test and only accepting Engine sites into the program. While this is sad for non English sites I guess they have to start somewhere. Hopefully they’ll widen it later at some point.

All in all – I’m pleased with Chitika’s mini-malls. They have loads of potential. I suspect (and until I get channels I won’t know for sure) that they will do best on product related blogs. They seem to serve very relevant ads to my gadget type blogs and struggle on some of my more ‘news’ related blogs.

Kids

How to kiss a lady

It ought to be enjoyable: studying to embrace the lady's strategy to girls kiss house. When you kiss nervous or when you only see it as a gateway to sexuality, is left behind. In reality, the supplement you're taking your time with kissing and really enjoy it, chances are extra enjoyable with physical intimacy with a girl. I am going to show you methods to kiss the most ladies - and relax!

For individuals who have never been kissed, the simplest thing you are able to do is guess. Not a big deal in case your first kiss mud! The ladies are very understanding, and cannot really laugh. I know many couples who joke about their first kiss. The primary kiss most individuals is a clumsy, if the women forgive her if she will not be good!

The following are taught to kiss the appropriate technique. This implies understanding how one can go to kiss him, to kiss the management of speed, kissing, affection and intimacy. There are various web sites out there, but I like to embrace this page is perfect for ladies on the appropriate path. You get the photographs and all components of what is proper and wrong.

I wish to kiss two areas specifically handle on this column love kissing and how to be a good kisser for intimacy. First we are going to talk about methods to be a good kisser for intimacy. Suppose you on a date and the necessity for questions concerning the subsequent level. Probably the greatest methods to speak about the way you wish to kiss her. As Craig guru, said: "Once we talk about intercourse, is a step in direction of it to be." Similarly, says the kiss is step one towards the kissing is real. You can rest the two, and when, said in a tone of relaxed, confident, not desperate, you cannot really drive a girl. Relating to kissing, kissing passionately common working! Use your arms, your physical appearance: Click on above, contact your face together with his arms and stroked her hair. All of those elements which are serious about privateness and the necessity, they're in the worst way.

when you shoot, you are good. Fort, only a gradual decline. Simply because she does so with the identical zeal, it does not imply they will. Many times the ladies do things somewhat slower to take than the boys. This is of high quality: the height of his pace. Kiss her neck, cheeks, anywhere. Finally, the heated. Than to enter it (groan, to move nearer to you, carry it back) will start to start to kiss her erogenous zones all over. Remember, not only a kiss on the lips! when you actually need intimate kiss on the neck - in the thighs, hips (very delicate!) And even in the feet. Not to point out the apparent areas. This ought to be a good evening of sex.

but don't kiss at the finish! Too many guys make that mistake. intercourse is only the start stage of kisses! How would you like, don't forget to kiss along her body, clearly in the neck and breasts. wish to be, passionate and intimate too - not only are you interested, act quickly. Kissing takes over this perform and may present a woman to do it again!

For love, studying how to be a good kisser is the best. Their are books and audio articles say that ladies like surprises, nothing that shows you have an interest in your girlfriend (or spouse) as a shock to kiss spontaneously from nothing! You will love and grace. As well as, you're rewarded for them to stay with you and treat you well. Good that his spouse, completely happy life! It is the identical together with his friends. don't be stunned if she begins to carry you breakfast in cooperation as a reward.

Hot Namitha