Functional noise floor adjustment of signal measurement device

A signal measurement device for measuring a spectrum of a radio frequency (RF) input signal using frequency sweeping over a swept frequency range, the signal measurement device comprising:

• a tunable local oscillator (LO) configured to generate an LO signal at different LO frequencies;
• a mixer configured to mix the RF input signal and the generated LO signal at the different LO frequencies to provide an intermediate frequency (IF) signal;
• an analog to digital converter (ADC) configured to digitize the IF signal at periodic intervals;
• and
• at least one processing unit programmed to:
• determine power levels of a noise floor of the signal measurement device at respective frequencies from a start frequency to a stop frequency of the swept frequency range;
• determine values of resolution bandwidths corresponding to the respective frequencies, the values of the resolution bandwidths being inversely proportional to the power levels of the noise floor at the respective frequencies;
• compute a tuning speed of the LO, implemented by an LO controller, to control the frequency sweeping from the start frequency to the stop frequency;
• and
• implement the values of the resolution bandwidths corresponding to the frequencies for the frequency sweeping,
• wherein implementing the values of the resolution bandwidths results in functional sensitivity of the signal measurement device being substantially constant over the swept frequency range.

A non-transitory computer-readable storage medium that stores instructions for measuring a received radio frequency (RF) input signal, which when executed by at least one processor, cause the at least one processor to perform a method comprising:

• determining root mean square (RMS) power levels of a noise floor of a spectrum analyzer at respective frequencies for frequency sweeping from a start frequency to a stop frequency of a swept frequency range, the spectrum analyzer comprising a local oscillator (LO) for generating an LO signal at different LO frequencies and a mixer for mixing the LO signal and the RF input signal;
• determining values of resolution bandwidths corresponding to the respective frequencies, the values of the resolution bandwidths being inversely proportional to the RMS power levels of the noise floor at the respective frequencies;
• computing a tuning speed of the LO to control the frequency sweeping from the start frequency to the stop frequency;
• and
• implementing the values of the resolution bandwidths corresponding to the frequencies for the frequency sweeping in order to provide functional sensitivity of the spectrum analyzer that is substantially constant over the swept frequency range.