Can any one give me the difference between the delay line's technique and the 2 sources technique? And why the 2 sources method is more accurate near the carrier?
Please see the attached document on "Choosing a Phase Noise Measurement Technique"
Both techniques are useful and each has its draw backs. For an example that answers your other question, with the delay line technique the sensitivity of the system is proportional to 1/f^2 (see p. 30 of the attached document). This is why the delay line method is better suited for higher offset frequencies, making the 2 sources technique more accurate near the carrier.
Please see the attached document on "Choosing a Phase Noise Measurement Technique"
Both techniques are useful and each has its draw backs. For an example that answers your other question, with the delay line technique the sensitivity of the system is proportional to 1/f^2 (see p. 30 of the attached document). This is why the delay line method is better suited for higher offset frequencies, making the 2 sources technique more accurate near the carrier.
Best regards,