Characterizing radio frequency sources based on data from a vapor cell sensor system
In a general aspect, data from a vapor cell sensor system is used to characterize radio frequency sources. In some aspects, a vapor cell sensor system generates output signals by operating one or more vapor cells at an array of locations in a radiating near-field region of an RF field produced by an RF source. Based on the output signals, a signal processing system generates measurement data that represents measured intensities of the RF field in the radiating near-field region. Based on the measurement data, the signal processing system generates a model of the RF field produced by the RF source. The model includes modeled intensities of the RF field in the radiating near-field region and a far-field region of the RF field.
1 . A signal processing system, comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations that comprise:
receiving output signals from a vapor cell sensor system that comprises one or more vapor cells, the output signals generated by operating the one or more vapor cells at an array of locations in a radiating near-field region of an RF field produced by an RF source;
generating, based on the output signals, measurement data representing measured intensities of the RF field in the near-field region; and
generating, based on the measurement data, a model of the RF field produced by the RF source, the model comprising modeled intensities of the RF field in the radiating near-field region and a far-field region of the RF field.
2 . The signal processing system of claim 1 ,
wherein the array of locations corresponds to first and second measurement domains in a Fresnel region of the RF field, the Fresnel region being part of the radiating near-field region; and
wherein the measurement data represent measured intensities of the RF field on the first and second measurement domains.
3 . The signal processing system of claim 2 ,
wherein the first measurement domain corresponds to a first surface, and the second measurement domain corresponds to a second surface; and
wherein the first and second surfaces are separated by a distance greater than or equal to a wavelength of the RF field.
4 . The signal processing system of claim 3 , wherein the first and second surfaces are planar surfaces.
5 . The signal processing system of claim 3 , wherein the first and second surfaces are planar surfaces that are parallel to each other.
6 . The signal processing system of claim 3 ,
wherein generating the model comprises projecting the measured intensities to a third surface in a Fraunhofer region of the RF field, the Fraunhofer region being part of the far-field region; and
wherein the model comprises modeled intensities of the RF field at a plurality of locations on the third surface.
7 . The signal processing system of claim 3 ,
wherein the model comprises modeled phases of the RF field on the first and second surfaces; and
wherein generating the model comprises using a phase retrieval algorithm to generate the modeled phases based on the measurement data.
8 . The signal processing system of claim 7 , wherein generating the model comprises:
selecting boundary data comprising the measured intensities and the modeled phases of the RF field on at least one of the first and second surfaces; and
using an RF diffraction model to generate the modeled intensities of the RF field in one or both of the radiating near-field region and the far-field region based on the boundary data.
9 . The signal processing system of claim 1 , wherein the model comprises modeled intensities of the RF field at a plurality of points that represent an emission pattern of the RF source.
10 . The signal processing system of claim 1 ,
wherein the one or more vapor cells is a first vapor cell;
wherein the vapor cell sensor system comprises an actuator system that is configured to move the first vapor cell; and
wherein the operations comprise transmitting a control signal to the actuator system to move the first vapor cell to each location in the array of locations.
11 . The signal processing system of claim 1 , wherein the one or more vapor cells is a plurality of vapor cells, and the vapor cell sensor system comprises a mount that is configured to hold the plurality of vapor cells at respective locations of at least a portion of the array of locations.
12 . The signal processing system of claim 1 , wherein the output signals are received from an optical detector of the vapor cell sensor system.
13 . The signal processing system of claim 1 , comprising one or more field programmable gate array (FPGAs), one or more graphics processing units (GPUs), or a combination of one or more FPGAs and GPUs.
14 . A signal processing method, comprising:
receiving output signals from a vapor cell sensor system that comprises one or more vapor cells, the output signals generated based on operating the one or more vapor cells at an array of locations in a radiating near-field region of an RF field produced by an RF source;
generating, based on the output signals, measurement data representing measured intensities of the RF field in the radiating near-field region; and
generating, based on the measurement data, a model of the RF field produced by the RF source, the model comprising modeled intensities of the RF field in the radiating near-field region and a far-field region of the RF field.
15 . The signal processing method of claim 14 ,
wherein the array of locations corresponds to first and second measurement domains in a Fresnel region of the RF field, the Fresnel region being part of the radiating near-field region; and
wherein the measurement data represent measured intensities of the RF field on the first and second measurement domains.
16 . The signal processing method of claim 15 ,
wherein the first measurement domain corresponds to a first surface, and the second measurement domain corresponds to a second surface; and
wherein the first and second surfaces are separated by a distance greater than or equal to a wavelength of the RF field.
17 . The signal processing method of claim 16 , wherein the first and second surfaces are planar surfaces.
18 . The signal processing method of claim 16 , wherein the first and second surfaces are planar surfaces that are parallel to each other.
19 . The signal processing method of claim 16 ,
wherein generating the model comprises projecting the measured intensities to a third surface in a Fraunhofer region of the RF field, the Fraunhofer region being part of the far-field region; and
wherein the model comprises modeled intensities of the RF field at a plurality of locations on the third surface.
20 . The signal processing method of claim 16 ,
wherein the model comprises modeled phases of the RF field on the first and second surfaces; and
wherein generating the model comprises using a phase retrieval algorithm to generate the modeled phases based on the measurement data.
21 . The signal processing method of claim 20 , wherein generating the model comprises:
selecting boundary data comprising the measured intensities and the modeled phases of the RF field on at least one of the first and second surfaces; and
using an RF diffraction model to generate the modeled intensities of the RF field in one or both of the radiating near-field region and the far-field region based on the boundary data.
22 . The signal processing method of claim 14 , wherein the model comprises modeled intensities of the RF field at a plurality of points that represent an emission pattern of the RF source.
23 . The signal processing method of claim 14 ,
wherein the one or more vapor cells is a first vapor cell;
wherein the vapor cell sensor system comprises an actuator system that is configured to move the first vapor cell; and
wherein the signal processing method comprises transmitting a control signal to the actuator system to move the first vapor cell to each location in the array of locations.
24 . The signal processing method of claim 14 , wherein the one or more vapor cells is a plurality of vapor cells, and the vapor cell sensor system comprises a mount that is configured to hold the plurality of vapor cells at respective locations of at least a portion of the array of locations.
25 . The signal processing method of claim 14 , wherein receiving the output signals comprises receiving the output signals from an optical detector of the vapor cell sensor system.