System for Field Testing Wireless Devices With Reduced Multipath Interference

• US 20120139571A1
• Filed: 12/02/2010
• Published: 06/07/2012
• Est. Priority Date: 12/02/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Nickel, Joshua G., Hakim, Joseph, Mayor, Robert W., MacGougan, Glenn D., Noellert, William J.
• Granted Patent: US 9,213,053 B2
• Time in Patent Office: Days
• US Class Current: 324/750.26
• CPC Class Codes: G01R 29/0821 rooms and test sites therefor, e.g. anechoic chambers, open field sites or TEM cells for testing antennas G01R29/105
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

A portable test chamber with an open top may serve as a field testing apparatus for wireless testing of electronic devices. A wireless device under test may be mounted within a cavity in the test chamber. The cavity may be surrounded by a dielectric lining of anechoic material. A layer of electromagnetic shielding such as metal foil may cover the outer surfaces of the dielectric lining. The chamber may have a box shape with a rectangular opening at its top. Satellite navigation system signals or other wireless signals may be received through the opening at the top of the test chamber during testing. The electromagnetic shielding may reduce the effects of multipath interference during field tests.

Claims

1. Field test apparatus within which a wireless device under test is tested outdoors, comprising:

a dielectric layer that surrounds a cavity in which the device under test is located; and

an electromagnetic shielding layer that covers the dielectric layer, wherein the electromagnetic shielding layer and the dielectric layer have an opening through radio-frequency signals pass to reach the device under test during field testing.

2. The field test apparatus defined in claim 1 wherein the dielectric layer comprises anechoic material.

3. The field test apparatus defined in claim 1 wherein the dielectric material comprises a polymer with voids and wherein the dielectric layer comprises protrusions selected from the group consisting of:

pyramidal protrusions and conical protrusions.

4. The field test apparatus defined in claim 1 wherein the dielectric layer has a thickness of at least two cm.

5. The field test apparatus defined in claim 1 wherein the opening comprises an opening selected from the group consisting of:

a rectangular opening, a circular opening, and an elliptical opening.

6. The field test apparatus defined in claim 1 wherein the electromagnetic shielding layer comprises metal.

7. The field test apparatus defined in claim 1 wherein the electromagnetic shielding layer comprises metal foil.

8. The field test apparatus defined in claim 1 further comprising a dielectric support structure mounted within the chamber, wherein the dielectric support structure is configured to support the wireless device under test above a rear wall surface of the cavity.

9. The field test apparatus defined in claim 1 wherein the device under test comprises Global Positioning System receiver circuitry that receives Global Positioning System signals through the opening, the field test apparatus further comprising a moving vehicle that moves the electromagnetic shielding layer and the dielectric layer during testing.

10. The field test apparatus defined in claim 1 wherein the dielectric layer forms an opened-top box and wherein the electromagnetic shielding layer is located on exterior portions of the open-topped box.

11. The field test apparatus defined in claim 10 wherein the electromagnetic shielding layer comprises metal foil.

12. The field test apparatus defined in claim 1 wherein the dielectric layer forms a box shape that at least partly surrounds the cavity and wherein the device under test comprises one of a plurality of devices under test within the cavity.

13. The field test apparatus defined in claim 1 further comprising a control unit that is configured to obtain multiple-input-multiple output test data from the device under test that the device under test acquired while the device under test was within the cavity.

14. The field test apparatus defined in claim 1 further comprising:

a control unit;

movable structures that are moved to adjust a field test apparatus parameter selected from the group consisting of;

angle of acceptance for radio-frequency signals passing through the opening to the device under test, size of the opening, and position of the device under test within the cavity; and

at least one actuator that moves the movable structures under control by the control unit to adjust the field test apparatus parameter.

15. The field test apparatus defined in claim 1 wherein the opening contains a radio-transparent and visibly opaque planar dielectric structure through which the radio-frequency signals pass.

16. A method of field testing a device under test outdoors to determine whether the device under test can satisfactorily receive satellite navigation signals, comprising:

placing the device under test within an open-topped field test apparatus that has electromagnetic shielding; and

while the device under test is within the open-topped field test apparatus and is outdoors, gathering test data by receiving the satellite navigation signals.

17. The method defined in claim 16 wherein the field test apparatus comprises a lining of dielectric with an opening and wherein gathering the test data comprises gathering the test data through the opening.

18. The method defined in claim 17 wherein the field test apparatus comprises a lining of radio-frequency signal absorbing material having a thickness of 2 to 20 cm, wherein the electromagnetic shielding comprises metal foil, wherein the lining and the metal foil are configured to form an opening, and wherein gathering the test data comprises gathering the test data through the opening.

19. The method defined in claim 17 wherein the satellite navigation signals comprise Global Positioning System signals and wherein gathering the test data comprises receiving the Global Positioning System signals through the opening.

20. A portable test chamber with an open top, comprising:

a dielectric material that is configured to surround a cavity, wherein a wireless device under test is located within the cavity; and

an electromagnetic shielding layer that covers at least some of the dielectric material, wherein the dielectric material and the electromagnetic shielding layer have an opening through which satellite signals are received by the wireless device under test during testing.

21. The portable test chamber defined in claim 20 wherein the dielectric material comprises polymer.

22. The portable test chamber defined in claim 21 wherein the polymer contains voids and wherein the electromagnetic shielding layer comprises metal foil.

23. The portable test chamber defined in claim 20 wherein the dielectric material comprises a bottom layer and four sidewall layers that surround the cavity and wherein the electromagnetic shielding layer comprises metal foil that covers an exterior surface of the bottom layer and exterior surfaces of the four sidewall layers.

24. The portable test chamber defined in claim 23 wherein the dielectric material comprises a layer of dielectric having a thickness of 2 to 20 cm.