Method for measuring characteristics of a transmitter unit of a device under test, test system and radio frequency device

Patent metadata

Field	Value
Publication number	US-10003416-B1
Application number	US-201615381812-A
Country	US
Kind code	B1
Filing date	Dec 16, 2016
Priority date	Dec 16, 2016
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A method for measuring characteristics of a transmitter unit of a device under test is described. A signal generator is provided that comprises a baseband processing unit having at least a digital pre-distortion sub-unit. A device under test is provided that has a transmitter unit. A measuring unit is provided. Said signal generator and said device under test are connected with each other via an interface. At least one input signal is generated by using said signal generator, said input signal is forwarded to said device under test. An output signal of said device under test is measured by using said measuring unit. A first pre-distortion parameter for an increasing input amplitude is determined by using said digital pre-distortion sub-unit. A second pre-distortion parameter for a decreasing input amplitude is determined by using said digital pre-distortion sub-unit. Said first and second pre-distortion parameters are determined such that said output signal has a high fidelity. Further, a test system and a radio frequency device are described.

First claim

The invention claimed is:

1. A method for measuring characteristics of a transmitter unit of a device under test, comprising:
providing a signal generator comprising a baseband processing unit having at least a digital pre-distortion sub-unit;
providing a device under test having a transmitter unit;
providing a measuring unit;
connecting said signal generator and said device under test with each other via an interface;
generating at least one input signal by using said signal generator, said input signal is forwarded to said device under test;
measuring an output signal of said device under test by using said measuring unit;
determining a first pre-distortion parameter for an increasing input amplitude by using said digital pre-distortion sub-unit; and
determining a second pre-distortion parameter different from the first pre-distortion parameter for a decreasing input amplitude by using said digital pre-distortion sub-unit, said first and second pre-distortion parameters being determined such that said output signal has a high fidelity, wherein said baseband processing unit divides a composition of said output signal into two parts, a first part relating to the increasing input amplitude for said first pre-distortion parameter, and a second part relating to the decreasing input amplitude for said second pre-distortion parameter.

2. The method according to claim 1 , wherein said first and second pre-distortion parameters are stored in an emulation unit, said emulation unit being part of said transmitter unit to set said transmitter unit.

3. The method according to claim 1 , wherein said measuring unit is at least connected to said signal generator.

4. The method according to claim 1 , wherein said baseband processing unit compares said output signal with an expected signal for determining said first and second pre-distortion parameters.

5. The method according to claim 1 , wherein said baseband processing unit creates a model of said transmitter unit using said two parts.

6. The method according to claim 1 , wherein said parts are weighted differently.

7. The method according to claim 1 , wherein said first pre-distortion parameter and said second pre-distortion parameter are determined separately for at least a first signal level such that both pre-distortion parameters do not influence each other.

8. The method according to claim 1 , wherein said first pre-distortion parameter and said second pre-distortion parameter are determined dependently for at least a second signal level such that both pre-distortion parameters correlate with each other.

9. The method according to claim 1 , wherein said first pre-distortion parameter and said second pre-distortion parameter are derived from at least one look-up table and/or at least one memoryless linearization polynomial.

10. A test system comprising:
a device under test including a transmitter unit;
a measuring unit; and
a signal generator including a baseband processing unit having a digital pre-distortion sub-unit, said processing unit being connected to said device under test via an interface, said digital pre-distortion sub-unit being configured to determine a first pre-distortion parameter for an increasing input amplitude and a second pre-distortion parameter different from the first pre-distortion parameter for a decreasing input amplitude, said pre-distortion parameters being determined to increase a fidelity of an output signal of said device under test, wherein said baseband processing unit divides a composition of said output signal into two parts, a first part relating to the increasing input amplitude for said first pre-distortion parameter, and a second part relating to the decreasing input amplitude for said second pre-distortion parameter.

11. The test system according to claim 10 , wherein said measuring unit is integrated in said signal generator, in particular wherein said measuring unit is assigned to a feedback line of said signal generator.

12. The test system according to claim 10 , wherein said measuring unit is a measuring device being formed separately with respect to said signal generator, in particular a radio frequency receiver or a multimeter.

13. The test system according to claim 10 , wherein said signal generator comprises a first signal generator unit and a second signal generator unit.

14. The test system according to claim 13 , wherein said first signal generator unit is configured to generate a radio frequency input signal and/or said second signal generator unit is configured to generate an envelope tracking signal.

15. The test system according to claim 10 , wherein said interface comprises a radio frequency forward interface and a backward interface.

16. The test system according to claim 10 , wherein said transmitter unit comprises an amplifier unit.

17. The test system according to claim 10 , wherein said test system is configured to:
generate at least one input signal by using said signal generator and forward said input signal to said device under test;
measure an output signal of said device under test by using said measuring unit;
determine said first pre-distortion parameter for said increasing input amplitude by using said digital pre-distortion sub-unit; and
determine said second pre-distortion parameter different from said first pre-distortion parameter for said decreasing input amplitude by using said digital pre-distortion sub-unit.

18. A radio frequency device comprising a transmitter unit with an emulation unit, said emulation unit implementing a first pre-distortion parameter for an increasing input amplitude and a second pre-distortion parameter different from the first pre-distortion parameter for a decreasing input amplitude, wherein said transmitter unit is set by a method comprising:
providing a signal generator comprising a baseband processing unit having at least a digital pre-distortion sub-unit;
providing a device under test having a transmitter unit;
providing a measuring unit;
connecting said signal generator and said device under test with each other via an interface;
generating at least one input signal by using said signal generator, said input signal is forwarded to said device under test;
measuring an output signal of said device under test by using said measuring unit;
determining the first pre-distortion parameter for the increasing input amplitude by using said digital pre-distortion sub-unit;
determining the second pre-distortion parameter for the decreasing input amplitude by using said digital pre-distortion sub-unit, wherein said baseband processing unit divides a composition of said output signal into two parts, a first part relating to the increasing input amplitude for said first pre-distortion parameter, and a second part relating to the decreasing input amplitude for said second pre-distortion parameter; and
storing the first and second pre-distortion parameters in the emulation unit.

Assignees

• Rohde & Schwarz

Inventors

• Lloyd Paul Gareth

Classifications

• G06F30/36

  Circuit design at the analogue level · CPC title

• H04B2001/0425

  with linearisation using predistortion · CPC title

• H04B17/13

  of power amplifiers, e.g. gain or non-linearity · CPC title

• H04B17/0085 Primary

  using test signal generators · CPC title

• H03F1/32

  Modifications of amplifiers to reduce non-linear distortion (by negative feedback H03F1/34) · CPC title