Method and apparatus for measuring characteristics of a communication signal modulated with a composite video signal without synchronizing to the signal

An apparatus for measuring a characteristic of a communication signal modulated by a composite video signal, comprising:

• (a) a receiver that receives the communication signal and generates an intermediate signal comprising direct current (DC) levels representative of the power spectrum of the communication signal at different instants of time;
• (b) an analog-to-digital converter (ADC) coupled to the receiver for sampling the intermediate signal at a sample rate and generating digital words representing samples of the intermediate signal;
• (c) a memory connected to the ADC that stores the digital words generated by the ADC;
• (d) a processor coupled to the ADC and to the memory, wherein the processor:
• (i) tunes the receiver to a frequency associated with the communication signal;
• (ii) controls the sample rate of the ADC for a period of time that exceeds one frame of the video signal to obtain a plurality of samples of the intermediate signal for storage in the memory;
• (iii) examines the plurality of samples to identify a predetermined feature of the communication signal;
• and
• (iv) measures a characteristic of the predetermined feature of the communication signal;
• wherein the processor tunes the receiver to a frequency corresponding to a visual carrier frequency of the communication signal, examines the plurality of samples to identify a sample having a maximum value among the plurality of sample values, the maximum value sample corresponding in time to a vertical synchronization pulse of the composite video signal and representing a power level at the visual carrier frequency of the communication signal, and measures a power level at the visual carrier frequency of the communication signal based on the level of the maximum value sample.

A computer-readable memory medium storing instructions which are executable by a processor for performing a process of measuring a characteristic of a communication signal in the presence of modulation, comprising steps of:

• (a) tuning a receiver to a frequency to receive the communication signal;
• (b) controlling the receiver to generate an intermediate signal comprising direct current (DC) levels representative of the power spectrum of the communication signal at different instants of time;
• (c) sampling the intermediate signal at a sample rate for a period of time that exceeds one frame of the composite video signal to obtain a plurality of digital samples of the intermediate signal;
• (d) examining the plurality of digital samples to identify a predetermined feature of the communication signal;
• and
• (e) measuring a characteristic of the predetermined feature of the communication signal;
• wherein the instructions stored on the memory medium for tuning comprise instructions for tuning to a visual carrier frequency of the communication signal;
• wherein the instructions for examining comprise instructions for identifying a sample that has a maximum value among the plurality of digital samples, the maximum value sample corresponding in time to a vertical synchronization pulse of the composite video signal and representing a power level at the visual carrier frequency of the communication signal;
• and
• wherein the instructions for measuring comprise instructions for measuring a power level at the visual carrier frequency of the communication signal based on the level of the maximum value sample.