Device for electric and magnetic measurements
Device for electric and magnetic measurements. In some embodiments, an electrical probe can be configured to include an unshielded inner conductor at an end of a coaxial assembly to allow an electrical field to induce differential-mode currents in the coaxial assembly. In some embodiments, a magnetic probe can be configured to include a loop connected to inner and outer conductors of a coaxial assembly to induce a common mode current by a change in magnetic field flux through the loop. In some implementations, such probes can be utilized to obtain near-field measurements to facilitate applications such as electromagnetic (EM) shielding designs.
1. A probe for sensing an electromagnetic (EM) field proximate to a radio-frequency (RF) device, the probe comprising:
a coaxial assembly having a proximal end and a distal end, the coaxial assembly including an inner conductor and an outer conductive shield between the proximal and distal ends; and
a sensing element implemented at the distal end of the coaxial assembly, the sensing element configured to sense an electrical component of a field strength of the EM field when the sensing element is configured to generate opposite differential-mode currents flowing in the inner conductor and the outer conductive shield when an electric field acts on at least a portion of the sensing element, and the sensing element configured to sense a magnetic component of the field strength of the EM field when the sensing element is configured to detect a common mode current from a change in magnetic field flux through at least a portion of the sensing element.
2. The probe of claim 1 further comprising a coaxial connector implemented at the proximal end of the coaxial assembly.
3. The probe of claim 1 wherein the outer conductive shield is connected to a ground during measurements.
4. The probe of claim 1 wherein the sensing element includes a loop having a first end connected to a distal end of the inner conductor and a second end connected to a distal end of the outer conductive shield, the loop configured so that a change in magnetic field flux through the loop induces a detectable common mode current.
5. The probe of claim 4 wherein the loop has a circular shape.
6. The probe of claim 5 wherein the circular loop has a diameter that is 1 mm or less.
7. The probe of claim 1 wherein the coaxial assembly has a characteristic impedance of approximately 50 ohms.
8. The probe of claim 1 wherein the field strength includes a near-field strength associated with the EM field strength present at a separation distance from a surface of the RF device.
9. The probe of claim 8 wherein the separation distance is approximately 1 mm or less.
10. A method for testing a radio-frequency (RF) device, the method comprising:
operating the RF device to generate an electromagnetic (EM) emission;
positioning a coaxial assembly having a sensing element relative to the RF device to allow a measurement of the EM emission, the coaxial assembly having a proximal end and a distal end, the coaxial assembly including an inner conductor and an outer conductive shield between the proximal and distal ends, the sensing element configured to sense an electrical component of a field strength of the EM emission when the sensing element is configured to generate opposite differential-mode currents flowing in the inner conductor and the outer conductive shield when an electric field acts on at least a portion of the sensing element, and the sensing element configured to sense a magnetic component of the field strength of the EM emission when the sensing element is configured to detect a common mode current from a change in magnetic field flux through at least a portion of the sensing element; and
measuring the field strength of the electrical component or the magnetic component through the positioned sensing element.
11. The method of claim 10 wherein the RF device is a power amplifier module.
12. The method of claim 10 wherein the measured field strength is representative of a field distribution over a selected area that is smaller than an overall lateral area of the RF device, the selected area being less than the overall lateral area by a factor of at least 10.
13. The method of claim 10 wherein the measured field strength is representative of a field distribution over a selected area that is smaller than an overall lateral area of the RF device, the selected area being less than or equal to approximately 1 mm 2 .
14. The method of claim 10 wherein the measured field strength includes a near-field strength associated with the EM field strength present at a separation distance from a surface of the RF device, the separation distance being approximately 1 mm or less.
15. A system for testing a radio-frequency (RF) device, the system comprising:
a control system configured to allow operation of the RF device;
a signal generator configured to provide an RF signal to the RF device so that the operating RF device generates an electromagnetic (EM) emission; and
a measurement system that includes a probe configured to measure a field strength representative of a field distribution, the probe including a sensing element and a coaxial assembly having a proximal end and a distal end, the coaxial assembly including an inner conductor and an outer conductive shield between the proximal and distal ends, the sensing element configured to sense an electrical component of a field strength of the EM field when the sensing element is configured to generate opposite differential-mode currents flowing in the inner conductor and the outer conductive shield when an electric field acts on at least a portion of the sensing element, and the sensing element configured to sense a magnetic component of the field strength of the EM field when the sensing element is configured to detect a common mode current from a change in magnetic field flux through at least a portion of the sensing element.
16. The system of claim 15 wherein the RF device is a power amplifier module.
17. The system of claim 15 wherein the measured field strength is representative of a field distribution over a selected area that is smaller than an overall lateral area of the RF device, the selected area being less than the overall lateral area by a factor of at least 10.
18. The system of claim 15 wherein the measured field strength is representative of a field distribution over a selected area that is smaller than an overall lateral area of the RF device, the selected area being less than or equal to approximately 1 mm 2 .
19. The system of claim 15 wherein the measured field strength includes a near-field strength associated with the EM field strength present at a separation distance from a surface of the RF device, the separation distance being approximately 1 mm or less.
20. The system of claim 15 wherein the probe comprises a coaxial connector implemented at the proximal end of the coaxial assembly.