Graph 1 showed use at measuring to wait for measure parts of an apparatus (the addition of DUT) is phasic the device of noise. Ask an attention, used two DUT; Every DUT all receives public power source and input clock repeatedly. The phasic noise that these public noise sources produce is outputted in every DUT be in relevant couplet. Through building phasic detector simply the model to become one has the imitate multiplier with gain KPD, can reach output phasic noise:

 

 

Among them the DUT1 that E1 is course enlarge outputs signal, e2 is the DUT2 output signal that passes enlarge and defer, EC1 and EC2 are signal power, θM1 and θM2 are the amplitude of phasic noise, ωC is carrier wave frequency, ωM is to slant place frequency. Apply overlay, because this should consider to come from when the phasic noise of exterior source, the phasic noise with inherent DUT is negligible not plan. If DUT1 and DUT2 are had,exceed an amount identically phasic transfer a function, the θM1 part that produces by clock source and power source is equal to the θM2 part that produces by public clock source and power source. This kind of phenomenon calls power source drawing, pass the following equational description OK and simply:

 

 

Such, the extent of phasic modulation the product of the voltage noise that can go up by power source and KP – gain of power source drawing (radian / V) reach. If DUT1 and DUT2 are had equivalent gain of power source drawing, theoretic these noise sources that can cancel phasic detector to lose source, leave two DUT only thereby have nothing to do noise is measured with undertaking.

 

Immanent DUT noise can undertake deciding through a few additional hypothesis. Because the Rms of generation of noise of parts of an apparatus is phasic the error is general and dinky, accordingly we can use small angle approximation to will output the expression instead of carrier wave:

 

 

The output of phasic detector already demodulation, because this can call ” of signal of “ base band. Once define phasic detector gain and input signal power, can calculate an actual phasic noise (the phasic noise that hypothesis amplifier produces is negligible not plan) . The noise with every inherent DUT is irrelvant, the noise that so they produce is identical, the output that and Rms adds up to measures is phasic noise. For this, the phasic noise that we measure from spectrum analyzer (unit: DBc/Hz) in the noise that subtractive 3 DB produces with deciding every DUT. This expresses relative to the phasic noise power at signal power:

 

 

When undertaking very sensitive phasic noise is measured, the noise that amplifier produces may be remarkable. The leftover and phasic noise of amplifier passes the following method to measure: Demolish DUT1 and DUT2 from inside circuit, apply power alloter to output directly to amplifier next. Power of amplifier input signal must be mixed in extent pressure place rate respect and actual DUT to output signal likeness. Use afore-mentioned measure, the DUT that connects associate to be measured subtracts in phasic noise measures amplifier is phasic noise, can get accurate DUT phasic noise. Same, the key is to should ensure each other are close to the gain of amplifier and noise index as far as possible.

 

Ask an attention, the DUT that needs clock to input signal has setup the front amplifier of certain noise. Accordingly, because amplifier inputs the threshold value uncertainty of place, have low pressure to place the clock source of rate to may increase the phasic noise that DUT produces inadvertently. When source of use sine clock, use please the biggest permission amplitude comes the biggest change pressure place rate.

 

Graph 1. Measurement unit of leftover and phasic noise.

 

Check the basic details of device

 

Use graph 1 in shows test plant, two DUT that have same part number are timed by source of clock of individual 1 GHz. Parts of an apparatus is by the setting divide clock frequency with the 4 output with producing 250 MHz. In addition, two output signal undertakes opposite phase shift moves 90° (orthogonality) with the smallest change those who appear in dc place to issue changeover signal n. DUT signal by low noise amplifier (LNA) enlarge, the dynamic range that measures a system in order to increase (the phasic noise that amplifier produces is OK small to ignor) . Amplifier output is sent balanced first detector (phasic detector) . Phasic detector mixes two signal, in its output part arises and accumulate reach difference to accumulate. And indigestion by low connect filter filter to divide. The rest difference is accumulated form next changeover to be dc (phasic noise) 250 MHz outputs signal. LNA offers enough gain to be restricted in order to overcome the background noise of spectrum analyzer.

 

Public clock source is phasic the elimination of noise

 

Graph 2 showed two clock cause (have extremely different phasic noise character) sound measurement of absolutely and phasic a confusion of voices. From theoretic tell, the DUT addition that clock source all won’t affect either to be measured by device of leftover and phasic noise is phasic noise. Graph 3 confirmed this one theory. Its scale sound measurement of two alone leftover and phasic a confusion of voices, every clock source has curve of a contrail. Two contrail curve overlaps almost, proved noise of public clock source already was eliminated by device of leftover and phasic noise. In device of absolutely and phasic noise, this noise will not be eliminated. In fact, if DUT is ideal (without addition phasic noise) , criterion its are absolutely and phasic noise curve will with the graph 2 medium curves match (but change as a result of the frequency of 1/4, its meeting low 12 DB) . Clock source 2 come in normalization after 250-MHz carrier wave, the phasic noise that shows a –92 DBc/Hz (1 KHz slants when buy) , and measure with clock source 2 relevant DUT phasic noise are –135 DBc/Hz (when 1 KHz) . Accordingly, leftover and phasic measure restrained about the input clock of 40 DB is phasic noise.

 

Graph 2. The measured value of absolutely and phasic noise of source of two different clock.

 

Graph 3. Clock source does not have an influence to measured value of leftover and phasic noise almost.

 

The elimination of noise of public power source

 

Graph 3 in used with the graph 1 same public power source joins. Graph 4 showed the influence that uses alone noise power source for every DUT. Noise of irrelvant power source can cause close carrier wave phasic noise increases considerably.

 

Graph 4. Sound measurement of leftover and phasic a confusion of voices shows public the influence with sole power source.

 

Graph 5 displayed the sound measurement of absolutely and phasic a confusion of voices when using low noise power source. The absolutely and phasic noise that has low noise power supply and the leftover and phasic noise that have power supply of alone low noise are shown gave good consistency. Already eliminated power source in sound measurement of leftover and phasic a confusion of voices phasic noise, but did not eliminate power source in sound measurement of absolutely and phasic a confusion of voices phasic noise.

 

Graph 5. Phasic noise got close carrier wave because of low noise power source improve

 

Leftover and phasic noise measures a way is a very useful technology, the phasic noise that the discrete component place that it uses at identifying to design one part as the system produces. Use this kind of method, exterior noise source (input clock and power source for example) relevant couplet is in in the output of every DUT, eliminate effectively accordingly. In addition, the bumper that it shows possibly still to be used in sound measurement of DUT leftover a confusion of voices or the phasic noise that amplifier place produces, the method is to these component undertakes additional sound measurement of leftover and phasic a confusion of voices. Combining use remains and absolutely and phasic noise to measure a way is a of main noise source very effective method in identifying a system to design. In scale down implement go up acquisition measurement the idea that data showed leftover and phasic noise to measure a way and effectiveness, and quantified the effect of bell and power source when noise is inputted. This evaluates have the aid of method, systematic stylist is OK according to actual measurement data reachs the norms of the Zhong Yuan when the input and power source.