In most lab environment, the equipment such as analyzer of signal generator, spectrum is Chan Duanyi implement, those who be used at measuring high speed to differ minute of amplifier driver and converter is lack fidelity. Accordingly, the even number that measures amplifier driver rank lack fidelity (for example 2 harmonic are lack fidelity HD2, even rank even number rank makes shift lack fidelity or IMD2) the parts of an apparatus with additional need, wait like Ba Lun and attenuator, test the one part of the setting as whole, join with checking Chan Duan the instrument the difference of amplifier driver divides input and output. The article announced through matching the mathematical knowledge of signal phasic lopsided importance, say palpability is phasic lopsided how cause production of even number rank increase (become worse namely! ) . The function index that the article still will show the balance of a few kinds of different high-powered Ba Lun and attenuator how to affect the amplifier that be measured (namely HD2 and IMD2) .

The high speed parts of an apparatus that the test has the input that need branch (wait like modulus converter, amplifier, first detector, Ba Lun) when, extent and phasic lopsided the main character that is need understanding.

 

When the frequency that designs use 500 MHz and above when imitate signal catenary, must special caution, because of all parts of an apparatus (no matter active is passive still) there is some to plant inside frequency limits inherent lopsided. 500 MHz is not a wonderful frequency is nodded, just be based on experience, this is most parts of an apparatus begins deviate the place of phasic balance. Differ according to parts of an apparatus, this frequency may be so lower than this that this frequency get much or high much.

 

We will see the simple maths model below carefully:
 

Graph 1. Have the mathematical model that two signal input.

 

Consideration ADC, amplifier, Ba Lun wait or any change signal the component that it is difference from Chan Duan (or conversely) the input X(t) of parts of an apparatus. Signal is sine signal to X1(t) and X2(t) , because this differs cent to input signal to have following forms:
 

 

If not be such, with respect to the lopsided quantity because of these parts of an apparatus, the even number of ADC rank lack fidelity test may produce marked change inside working frequency limits as a result.
 

 

ADC or any active parts of an apparatus build a model OK and simply to be semmetry 3 rank transfer function:

 

So:

 

Do not have below good case lopsided, the transfer function of afore-mentioned simple systems can build a model to be as follows:
 

 

This is the common result of the circuit that need branch: Of ideal signal occasionally second harmonic is quits, and strange second harmonic did not offset.

 

 

If had turned round to compare formula 9 with formula 12, and assume trigonometry identity is applied correct, if make conclusions,can reach so: 2 times harmonic suffers phasic lopsided effect more lopsided than getting range effect is more serious. The reason is as follows: To phasic lopsided, 2 times the square of harmonic and K1 becomes direct ratio; See formula again 12, lopsided to extent, the smooth variance of 2 harmonic and K1 and K2 becomes direct ratio, or see formula 9. Because K1 and K2 are roughly equal, because of this this differentia different normally very small, if count its and square,undertake comparative especially!

 

Check high speed amplifier
 

Since we kept clear of obstacle, see an use case next, if pursue,2 are shown. This is a block diagram, lack fidelity test installs the commonly used HD2 in showing difference assigns amplifier test.
 

Graph 2. HD2 of high speed amplifier checks a setting

 

At first sight is quite simple, but the devil is concealed in detail. Graph 3 showed a group of HD2 check a result, its are amplifier of all parts of an apparatus in using this block diagram, poor cent, Ba Lun, attenuator get. These check a proof: Retroflexion with different kind merely what place of Ba Lun direction brings about is subtle and phasic do not match, can produce different result in HD2 sweep. There are two Ba Lun in this setting, because this passes conversed setting,a side or the join of two side can found 4 kinds of likely setting. If pursue,as a result 3 are shown.
 

Graph 3. 1A Ba Lun and direction of different Ba Lun check use supplier HD2 function

 

Graph amount of variation of lack fidelity curve proves the 3 HD2 that announce, need inspects Ba Lun’s property further, especially phasic with extent lopsided. What two graphs showed a few Ba Lun of different manufacturer under is phasic with extent lopsided. Use network analyzer will measure lopsided.

 

Graph 4 with the graph 5 medium gules curves are corresponding at the graph 3 useful at collecting HD2 the actual Ba Lun of fuzzy data. This Ba Lun of supplier 1A has highest bandwidth and good bandpass evenness to spend, but go up in calibration tape of same 10 GHz frequency, phasic lopsided want difference than other Ba Lun.
 

Graph 4. All sorts of of Ba Lun phasic lopsided

 

Graph 5. All sorts of Ba Lun’s extent are lopsided

 

Next two graphs delegate uses optimal Ba Lun the result of lack fidelity to HD2 new test, these Ba Lun comes from supplier 1B and supplier 2B respectively, have minimum phasic lopsided, if pursue 6 with the graph 7 are shown. Attention, if have better lopsided performance, criterion HD2 lack fidelity variance can be reduced accordingly, if pursue,7 are shown.
 

Graph 6. 1B Ba Lun and direction of different Ba Lun check use supplier afresh HD2 function.

 

Graph 7. 2B Ba Lun and direction of different Ba Lun check use supplier afresh HD2 function

 

For farther specification phasic lopsided how to affect even number rank directly lack fidelity function, graph the 8 HD3 that showed as same as graph of before one HD2 condition falls are lack fidelity. Ask an attention, 4 all curves are roughly identical, accord with anticipate. Accordingly, prove like the place of mathematical derivation give typical examples in front, HD3 is lack fidelity pair of signal catenary are medium lopsided not quite sensitive.
 

Graph 8. 2B Ba Lun and direction of different Ba Lun check use supplier HD3 function

 

So far, should assume input and output connective attenuator solder dish (if the graph is shown 2 times) it is dormant, and invariant during Ba Lun direction is measured. Next graphs represent the identical curve that the graph shows 7 times, check the Ba Lun performance of supplier 2B only, input and attenuator is exchanged between output. This produces another group (4) curve, if pursue,9 medium dotted line are shown. The result is we returned initial place, more change are shown in because this is checking,be being measured. This emphasized those who hold the post of a side differring minute of signal to be opposite further a few do not match to be affected below high frequency rate very big. Record test condition in detail without fail.
 

Graph 9. Use supplier 2B Ba Lun and direction of different Ba Lun and attenuation solder only dish function of commutative test HD2

 

Anyhow, in GHz area development complete difference divides signal catenary when, all things are very important, include attenuator solder dish, Ba Lun, cable, printed circuit board go up walk along a line to wait. We had gone up in maths and high speed is used to differred minute of amplifier to prove this as test platform in the lab. Accordingly, before beginning to blame parts of an apparatus or supplier, ask special during PCB layout and lab check caution.

 

Finally, you may ask oneself, how old and phasic lopsided can you tolerate? For example, a Ba Lun is phasic when X GHz lopsided spend for X, does it have He Ying to ring to specific parts of an apparatus or system? Whether can function of degree of linearity have the loss of certain level or DB attenuation?

 

This is the problem of a very difficult answer. In ideal world, if every thing in signal catenary is ideal,match, won’t have even number rank so lack fidelity need is afraid. Next, what if an experience law or formula come,tell us every X° is phasic the loss of degree of linearity that lopsided meeting brings X DB (HD2 function is reduced) , not beautiful. But, this is impossible. Why? Because of every parts of an apparatus, no matter active, passive or difference distribute form, what can have some kind of solid is phasic do not match. Make without method interiorly IC design achieves perfect balance at all, or the cable that cut gives length to agree absolutely. Accordingly, no matter these do not match have many small, the frequency that uses as the system is taller and taller, they can become more outstanding.