This document details a simple circuit test setup which measures low level second harmonic distortions from various passive circuit elements using a single carrier generator.
The purpose of this document is to establish the standard methodology to measure second harmonic distortion in a Cable Telecommunication System passive at high signal level conditions (50 – 60 dBmV). Due to the difficulty in acquiring multi-carrier signal generators with both 55 dBmV output and intermod beats at –120 dBc, the test procedure will use a single carrier source test method.
The area of concern for most cable telecommunication systems are the high power signals sent in the return path. Therefore, this document limits the testing to signals in the return path range.
Second harmonic: A waveform generated at twice the frequency as the original. Such distortion can occur when one or more carriers pass through a nonlinear device.
Second Harmonic Distortion (SHD) is defined as the ratio of the second harmonic signal level to the fundamental carrier signal level at the Device Under Test (DUT) output.
Please note that this procedure is a very unique procedure for measuring second harmonic distortion of passives using a single carrier source test method and distinguishes itself from other similar procedures in the following ways:
- Designed for Passives
- Two port measurement
- Inject return frequency into input and measure 2nd harmonic at output
- Used to test for distortion caused by core saturation. Designed to be consistent with the mechanisms that have caused problems in outside plant -- large reverse carriers causing distortion in channels 2 through 5.
This document describes a simple method for measuring the second order nonlinear properties of passive circuit elements. Because of tight channel spacing and demand for more channels increases, the effects of nonlinear distortion needs to be measured or otherwise the whole system performance may be susceptible to degradation.
The intended audiences for this test procedure are manufacturers, evaluation laboratories, and end user technician and engineers with the proper equipment to perform this testing.