Functional noise floor adjustment of signal measurement device

Patent metadata

Field	Value
Publication number	US-11137429-B2
Application number	US-201916367494-A
Country	US
Kind code	B2
Filing date	Mar 28, 2019
Priority date	Mar 28, 2019
Publication date	Oct 5, 2021
Grant date	Oct 5, 2021

Abstract

A signal measurement device and method are provided for receiving an RF input signal using frequency sweeping. The method includes determining RMS power levels of a noise floor of the signal measurement device at respective frequencies from a start frequency to a stop frequency of a swept frequency range; determining values of resolution bandwidths corresponding to the frequencies, the values of the resolution bandwidths being inversely proportional to the RMS power levels of the noise floor at the respective frequencies; performing frequency sweeping from the start frequency to the stop frequency to receive the RF input signal at the signal measurement device; and implementing the determined values of the resolution bandwidths corresponding to the frequencies while performing the frequency sweeping. Implementing the determined values of the resolution bandwidths results in functional sensitivity of the signal measurement device being substantially constant over the swept frequency range, and provides faster sweep times.

First claim

The invention claimed is:

1. A method of receiving a radio frequency (RF) input signal by a signal measurement device using frequency sweeping, the method comprising:
determining root mean square (RMS) power levels of a noise floor of the signal measurement device at respective frequencies from a start frequency to a stop frequency of a swept frequency range;
determining values of resolution bandwidths corresponding to the frequencies, the values of the resolution bandwidths being inversely proportional to the RMS power levels of the noise floor at the respective frequencies;
performing frequency sweeping from the start frequency to the stop frequency to receive the RF signal at the signal measurement device; and
implementing the values of the resolution bandwidths corresponding to the frequencies while performing 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.

2. The method of claim 1 , wherein determining the RMS power levels of the noise floor of the signal measurement device comprises accessing previously stored noise floor RMS power levels corresponding to the respective frequencies.

3. The method of claim 1 , wherein determining the RMS power levels of the noise floor of the signal measurement device comprises selecting a test resolution bandwidth, performing an internal sweep over the swept frequency range using the selected test resolution bandwidth, and identifying the RMS power levels of the noise floor corresponding to the respective frequencies at the selected test resolution bandwidth.

4. The method of claim 1 , wherein the values of the resolution bandwidths corresponding to the frequencies are determined in steps at discrete frequencies separated by predetermined gaps.

5. The method of claim 1 , wherein the values of the resolution bandwidths corresponding to the frequencies are determined substantially continuously over the swept frequency range.

6. The method of claim 1 , wherein implementing the values of the resolution bandwidths comprises automatically adjusting a local oscillator (LO) frequency of an LO in the signal measurement device while performing the frequency sweeping.

7. The method of claim 1 , wherein implementing the values of the resolution bandwidths provides at least one resolution bandwidth greater than a resolution bandwidth corresponding to a frequency in a portion of the swept frequency range having a highest RMS power level of the noise floor, enabling an increased sweep speed over the swept frequency range.

8. The method of claim 1 , wherein implementing the values of the resolution bandwidths ensures that the RF input signal is above the noise floor of the signal measurement device at the respective frequencies of the swept frequency range.

9. The method of claim 1 , wherein a maximum allowable sweep speed is approximately proportional to the square of value of each of the resolution bandwidths, respectively.

10. 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.

11. The device of claim 10 , wherein computing the tuning speed of the LO comprises determining intervals for stepping the LO frequencies, and wherein segments of the spectrum at each LO step are catenated to provide the spectrum.

12. The device of claim 10 , further comprising:
a user interface configured to enable a user to manually select a fast sweep mode, corresponding to implementing the values of the resolution bandwidths corresponding to the frequencies for the frequency sweeping, and a normal sweep mode, corresponding to implementing a fixed resolution bandwidth.

13. The device of claim 10 , wherein the determined power levels comprise root mean square (RMS) power levels of the noise floor of the signal measurement device.

14. The device of claim 13 , wherein the RMS power levels of the noise floor are determined by accessing noise floor RMS power levels corresponding to the respective frequencies previously stored in memory.

15. The device of claim 13 , wherein the RMS power levels of the noise floor are determined by selecting a test resolution bandwidth, performing an internal sweep over the swept frequency range using the selected test resolution bandwidth, and identifying the RMS power levels of the noise floor corresponding to the respective frequencies at the selected test resolution bandwidth.

16. The device of claim 10 , wherein the values of the resolution bandwidths corresponding to the respective frequencies are determined in steps at discrete frequencies separated by predetermined gaps.

17. The device of claim 10 , wherein the values of the resolution bandwidths corresponding to the respective frequencies are determined substantially continuously over the swept frequency range.

18. 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.

19. The computer-readable storage medium of claim 18 storing instructions, which when executed by

Assignees

• Keysight Technologies Inc

Inventors

• Erickson Bruce A
• Koch Keith

Classifications

• H04B17/318

  Received signal strength · CPC title

• G01R23/16

  Spectrum analysis; Fourier analysis · CPC title

• G01R29/26

  Measuring noise figure; Measuring signal-to-noise ratio · CPC title

• G01R23/173 Primary

  Wobbulating devices similar to swept panoramic receivers · CPC title