Method and apparatus for measuring the input frequency response of a digital receiver

A frequency response measurement circuit, comprising:

• a generation circuit operative to generate an input signal having a voltage and programmable frequency characteristics, the frequency characteristics controlled by a frequency control signal, and a corresponding sampling clock signal having synchronous frequency characteristics to the input signal;
• a decision circuit operative to sample the input signal at intervals corresponding to the synchronous sampling clock signal, the decision circuit determining the amplitude characteristics of the input signal at leach application of the synchronous sampling clock signal;
• and
• control circuitry operative to determine the frequency response characteristics of the input signal across each application of the synchronous sampling clock signal and each phase of the input signal.

A frequency response measurement method comprising:

• receiving an input signal;
• sampling the voltage characteristics of the input signal relative to a threshold voltage value at a corresponding sampling frequency;
• adjusting the threshold voltage value at the corresponding sampling frequency;
• sampling the voltage characteristics of the input signal relative to the adjusted threshold voltage value at the corresponding sampling frequency;
• repeating the sampling and adjusting steps until the input signal voltage and the adjusted threshold voltage intersect;
• and
• maintain the intersect value relative to the corresponding sampling frequency.