Methods for modeling tunable radio-frequency elements

• US 8,947,113 B2
• Filed: 05/07/2012
• Issued: 02/03/2015
• Est. Priority Date: 05/07/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Han, Liang, Nath, Jayesh, Mow, Matthew A., Bevelacqua, Peter, Nickel, Joshua G., Pascolini, Mattia, Schlub, Robert W., Caballero, Ruben
• Primary Examiner(s): Nguyen, Vincent Q
• Application Number:
  US13/466,017
• Publication Number:
  US 20130293249A1
• Time in Patent Office: 1,002 Days
• Field of Search: 324/601, 324/750.01, 324/650
• US Class Current: 324/750.02
• CPC Class Codes: G01R 1/045 Sockets or component fixtures for RF or HF testing
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A test system for characterizing an antenna tuning element is provided. The test system may include a test host, a radio-frequency tester, and a test fixture. The test system may calibrate the radio-frequency tester using known coaxial standards. The test system may then calibrate transmission line effects associated with the test fixture using a THRU-REFLECT-LINE calibration algorithm. The antenna tuning element may be mounted on a test socket that is part of the test fixture. While the antenna tuning element is mounted on the test socket, scattering parameter measurements may be obtained using the radio-frequency tester. An equivalent circuit model for the test socket can be obtained based on the measured scattering parameters and known characteristics of the antenna tuning element. Once the test socket has been characterized, an equivalent circuit model for the antenna tuning element can be obtained by extracting suitable modeling parameters from the measured scattering parameters.

Claims

1. A method for using a test system to test a device under test, wherein the test system includes a test fixture to which the device under test is attached during testing, the method comprising:

calibrating the test fixture to remove systematic effects associated with the test fixture;

when the systematic effects associated with the test fixture have been removed, characterizing the device under test, wherein the device under test comprises an antenna tuning element, wherein characterizing the device under test comprises characterizing the antenna tuning element, wherein the test system further includes a radio-frequency tester;

while the device under test is attached to the test fixture, obtaining radio-frequency measurements from the device under test with the radio-frequency tester, wherein obtaining the radio-frequency measurements from the device under test comprises gathering scattering parameter data from the device under test.

2. The method defined in claim 1, wherein the radio-frequency tester comprises a vector network analyzer, and wherein obtaining the radio-frequency measurements comprises obtaining the radio-frequency measurements from the device under test with the vector network analyzer.

3. The method defined in claim 1, further comprising:

calibrating the radio-frequency tester using a coaxial standard.

4. A method for using a test system to test a device under test, wherein the test system includes a test fixture to which the device under test is attached during testing, the method comprising:

calibrating the test fixture to remove systematic effects associated with the test fixture;

when the systematic effects associated with the test fixture have been removed, characterizing the device under test, wherein the device under test comprises an antenna tuning element, wherein characterizing the device under test comprises characterizing the antenna tuning element, wherein the test system further includes a radio-frequency tester;

while the device under test is attached to the test fixture, obtaining radio-frequency measurements from the device under test with the radio-frequency tester, wherein the test fixture includes a substrate having at least one transmission line path configured to convey radio-frequency test signals between the radio-frequency tester and the device under test, and wherein calibrating the test fixture comprises calibrating transmission line path characteristics associated with the substrate using a THRU-REFLECT-LINE (TRL) method.

5. A method for using a test system to test a device under test, wherein the test system includes a test fixture to which the device under test is attached during testing, the method comprising:

calibrating the test fixture to remove systematic effects associated with the test fixture;

when the systematic effects associated with the test fixture have been removed, characterizing the device under test, wherein the device under test comprises an antenna tuning element, wherein characterizing the device under test comprises characterizing the antenna tuning element, wherein the test fixture includes a substrate and a test socket that is attached to the substrate, wherein the test socket is configured to receive the device under test during testing, wherein calibrating the test fixture comprises calibrating the test fixture to remove systematic effects associated with the substrate and the test socket, and wherein the test system further includes a test host and a radio-frequency tester;

while the device under test is attached to the test fixture, obtaining radio-frequency measurements from the device under test with the radio-frequency tester; and

with the test host, obtaining an equivalent circuit model for the test socket based on the obtained radio-frequency measurements and known frequency response characteristics associated with the device under test.

6. The method defined in claim 5, wherein characterizing the device under test comprises obtaining an equivalent circuit model for the device under test using the obtained radio-frequency measurements while taking into account systematic effects associated with the test fixture and the radio-frequency tester.