ACTIVE ANTENNA SYSTEM AND METHODS OF DETERMINING INTERMODULATION DISTORTION PERFORMANCE

• US 20170176507A1
• Filed: 04/08/2015
• Published: 06/22/2017
• Est. Priority Date: 04/08/2014
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Analog Devices Global Unlimited Company (Analog Devices, Inc.)
• Inventors: O'Keeffe, Conor, Moore, Joe
• Granted Patent: US 10,067,171 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 29/10 Radiation diagrams of antennas
• CPC Class Codes: H01Q 1/00 Details of, or arrangements associated with, antennas arrangements for varying orientation of directional pattern H01Q3/00
• CPC Class Codes: H04B 1/0466 Fault detection or indication H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 17/102 Power radiated at antenna
• CPC Class Codes: H04B 17/104 of other parameters, e.g. DC offset, delay or propagation times
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/19 Self-testing arrangements

Abstract

An active antenna test system comprising an active antenna unit comprising: a test signal generator arranged to generate at least a first test signal and at least one second test signal; a plurality of transmitter modules operably coupled to the test signal generator wherein the plurality of transmitter modules are arranged to simultaneously process the first test signal and at least one second test signal to produce at least one radio frequency test signal therefrom; and at least one receiver module arranged to process one or more signals falling in at least one spectral band determined to be susceptible to intermodulation distortion products caused by the at least one radio frequency test signal being generated from the first test signal and at least one second test signal; and an intermodulation determination module operably coupled to the at least one receiver module and arranged to determine a first received intermodulation performance. A first transmitter module of the plurality of transmitter modules is operably uncoupled from the test signal generator and at least a first test signal and at least one second test signal re-applied to the remaining transmitter modules, such that the intermodulation determination module determines a second received intermodulation performance in order to determine an intermodulation distortion contribution of the first transmitter module therefrom.

Claims

1. An active antenna test system comprising:

an active antenna unit comprising;

a test signal generator arranged to generate at least a first test signal and at least one second test signal;

a plurality of transmitter circuits operably coupled to the test signal generator wherein the plurality of transmitter circuits are arranged to process the first test signal and at least one second test signal to produce at least one radio frequency test signal therefrom;

at least one receiver circuit arranged to process one or more signals falling in at least one spectral band determined to be susceptible to intermodulation distortion products caused by the at least one radio frequency test signal being generated from the first test signal and at least one second test signal; and

an intermodulation determination circuit operably coupled to the at least one receiver circuit and arranged to determine a first received intermodulation performance,

wherein a first transmitter circuit of the plurality of transmitter circuits is operably uncoupled from the test signal generator and at least a first test signal and at least one second test signal re-applied to the remaining transmitter circuits, such that the intermodulation determination circuit determines a second received intermodulation performance in order to determine an intermodulation distortion contribution of the first transmitter circuit therefrom.

2. The active antenna test system of claim 1 wherein, the first transmitter circuit of the plurality of transmitter circuits is re-coupled to the test signal generator and a second transmitter circuit of the plurality of transmitter circuits is operably uncoupled from the test signal generator and at least a third test signal and at least one fourth test signal applied to the remaining coupled transmitter circuits, such that the intermodulation determination circuit determines a further received intermodulation performance in order to determine an intermodulation distortion contribution of the second transmitter circuit therefrom.

3. The active antenna test system of claim 2 wherein at least one further transmitter circuit of the plurality of transmitter circuits is re-coupled to the test signal generator and the at least one further transmitter circuit is operably uncoupled from the test signal generator such that an intermodulation performance of the at least one further transmitter circuit is sequentially determined.

4. The active antenna test system of claim 2 wherein, at least one of the following applies:

the first test signal substantially equals the third test signal, the second test signal substantially equals the fourth test signal.

5. The active antenna test system of claim 1, wherein, the test signal generator is arranged to at least generate the first test signal and the at least one second test signal following at least one processor being arranged to disable normal traffic being routed through the active antenna unit.

6. The active antenna test system of claim 1, wherein, the active antenna unit comprises an inbuilt at least one test signal source arranged to perform one or more of the following:

generate at least one standardised test signal;

generate at least one test signal with at least one characteristic of the air interface being operated by the active antenna unit.

7. The active antenna test system of claim 1, wherein the intermodulation determination circuit comprises a Fast Fourier Transform circuit arranged to determine at least a magnitude of identified intermodulation components from the one or more signals falling in at least one spectral band determined to be susceptible to intermodulation distortion product artefacts caused by processing at least one radio frequency test signal being generated from the first test signal and at least one second test signal.

8. The active antenna test system of claim 7 wherein the intermodulation determination circuit is further arranged to measure a power level and frequency of intermodulation components of the processed at least one radio frequency test signal and determine therefrom a resultant impact on receiver performance for at least one order of intermodulation distortion.

9. The active antenna test system of claim 1, wherein the at least one receiver is tuned to select a predetermined frequency spectrum susceptible to at least one of the intermodulation components from an artefact of the at least one radio frequency test signal and the intermodulation determination circuit is arranged to determine whether the selected at least one intermodulation component exceeds an intermodulation distortion acceptable range or falls above or below a threshold value.

10. The active antenna test system of claim 2, wherein at least one processor is arranged to rank a plurality of transmitter circuits in response to their respective determined intermodulation performance.

11. The active antenna test system of claim 1, wherein at least one processor is arranged to adjust a parameter of at least one of:

the at least one transmitter circuit, the at least one receiver circuit in response to the determined intermodulation performance thereby reducing an intermodulation level of signals processed by the active antenna unit.

12. The active antenna test system of claim 11 wherein the at least one processor is arranged to adjust a parameter by applying at least one of:

an attenuation factor, a gain factor, a beamform weight adjustment, a filter adjustment, a digital predistortion adjustment, a frequency plan of used frequencies applied to at least one live air interface traffic signal processed by the active antenna unit.

13. The active antenna test system of claim 12 wherein the at least one processor is arranged to offset an effect of the applied attenuation or gain factor by applying at least one beam weight compensation value to another transmit circuit or receiver circuit.

14. The active antenna test system of claim 1, wherein an interface is operably coupled to the test signal generator such that the test signal generator and intermodulation determination circuit are remotely controllable via the interface.

15. The active antenna test system of claim 14 wherein the test signal generator and intermodulation determination circuit are remotely controllable via the interface by a software program located in the cloud.

16. A method of determining intermodulation performance in an active antenna test system comprising an active antenna unit having a plurality of transmitter circuits, the method comprising:

generating by a test signal generator at least a first test signal and at least one second test signal;

applying the first test signal and the at least one second test signal to the plurality of transmitter circuits;

processing the first test signal and the at least one second test signal to output from the plurality of transmitter circuits to produce at least one radio frequency test signal therefrom;

processing by an intermodulation determination circuit one or more signals falling in at least one spectral band determined to be susceptible to intermodulation distortion products caused by the at least one radio frequency test signal being generated from the first test signal and at least one second test signal in at least one receiver circuit;

determining a first received intermodulation performance of the processed one or more signals;

uncoupling a first transmitter circuit of the plurality of transmitter circuits from the test signal generator;

re-applying the first test signal and the at least one second test signal to the remaining transmitter circuits;

determining a second received intermodulation performance for the remaining transmitter circuits; and

determining an intermodulation distortion contribution of the first transmitter circuit therefrom.

17. The method of determining intermodulation performance of claim 16 further comprising repeating the steps of uncoupling a further transmitter module, re-coupling the first transmitter module, re-applying, determining and determining an intermodulation distortion contribution for the further transmitter module of the active antenna unit.

18. The method of determining intermodulation performance of claim 16 further comprising adjusting a parameter of at least one of:

the at least one transmitter circuit, the at least one receiver circuit in response to the determined intermodulation performance of the processed transmit frequency signal, thereby reducing an intermodulation level of signals processed by the active antenna unit.

19. The method of determining intermodulation performance of claim 18 further comprising:

determining an intermodulation performance of at least one of;

the plurality of transmitter circuits, the plurality of receiver circuits following adjusting the parameter of at least one of;

the at least one transmitter circuit and the at least one receiver circuit; and

performing a further adjustment of a parameter in response thereto.

20. A non-transitory computer program product comprising executable program code for determining intermodulation performance, the executable program code comprising instructions that, when executed at an active antenna unit, cause the active antenna unit to:

generate at least a first test signal and at least one second test signal;

apply the first test signal and the at least one second test signal to the plurality of transmitter circuits;

process the first test signal and the at least one second test signal to output from the plurality of transmitter circuits to produce at least one radio frequency test signal therefrom;

process one or more signals falling in at least one spectral band determined to be susceptible to intermodulation distortion products caused by the at least one radio frequency test signal being generated from the first test signal and at least one second test signal in at least one receiver circuit;

determine a first received intermodulation performance of the processed one or more signals;

uncouple a first transmitter circuit of the plurality of transmitter circuits from the test signal generator;

re-apply the first test signal and the at least one second test signal to the remaining transmitter circuits;

determine a second received intermodulation performance for the remaining transmitter circuits; and

determine an intermodulation distortion contribution of the first transmitter circuit therefrom.