Linearity Evaluation Method Using Integrations Weighted by Probability Density Function, and Circuit simulator, Evaluation Device, Communication Circuit, andvProgram Using the Method

• US 20080019433A1
• Filed: 06/13/2005
• Published: 01/24/2008
• Est. Priority Date: 06/23/2004
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kunihiro, Kazuaki, Yamanouchi, Shingo
• Granted Patent: US 7,792,181 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3282 Acting on the phase and the amplitude of the input signal
• CPC Class Codes: H04B 17/3912 Simulation models, e.g. distribution of spectral power density or received signal strength indicator [RSSI] for a given geographic region
• CPC Class Codes: H04L 27/368 adaptive predistortion
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

An evaluation method for linearity evaluations neither performing calculations of error vectors at multiple sampling points nor using a demodulator corresponding to a desired modulation scheme. Measuring devices (164 and 165) measure the input signal and the output signal of an evaluation object (1), to which a predetermined evaluation signal has been inputted. An evaluation unit (166) uses the input signal and the output signal of the evaluation object (1), to determine at least one of an amplitude distortion or a phase distortion of the output signal. An integration unit (169) uses the distortions to perform the integrations weighted by the probability density function of the power-to-average ratio of a predetermined modulated signal. A linearity index calculation unit (170) calculates a linearity index from the results of processing by the integration unit (169).

Claims

1. A linearity evaluating method for evaluating a linear index in a system under test in an electric circuit, comprising the steps of:

inputting a predetermined evaluation signal to said system under test;

determining at least one of an amplitude distortion and a phase distortion of an output from said system under test to which said evaluation signal has been input;

performing an integrating process on said one of the amplitude distortion and the phase distortion weighted by a probability density function of a power/average power ratio of a predetermined modulated signal; and

calculating said linear index from the result of said integrating process.

2. A linearity evaluating method according to claim 1, wherein said phase distortion is not determined, but only said amplitude distortion is determined, and said integrating process is performed using said amplitude distortion.

3. A linearity evaluating method according to claim 1, wherein said amplitude distortion is not determined, but only said phase distortion is determined, and said integrating process is performed using said phase distortion.

4. A linearity evaluating method according to claim 1, further comprising the step of:

calculating an error vector magnitude when said modulated signal is used in said system under test, from the result of said integrating process.

5. A linearity evaluating method according to claim 4, further comprising the steps of:

determining a residual error vector magnitude of a circuit or a measuring system near said system under test; and

calculating a total error vector magnitude representing a combination of said error vector magnitude and said residual error vector magnitude.

6. A linearity evaluating method according to claim 1, wherein said evaluation signal comprises a signal including a component having a carrier frequency of said modulated signal or a frequency close to said carrier frequency.

7. A linearity evaluating method according to claim 6, wherein said evaluation signal comprises a sine-wave signal of said carrier frequency.

8. A circuit simulator for evaluating a linear index in a system under test in an electric circuit, comprising:

an evaluation signal generator for inputting a predetermined evaluation signal to a model of said system under test;

an evaluator for determining at least one of an amplitude distortion and a phase distortion of an output from said system under test to which said evaluation signal has been input;

an integration processor for performing an integrating process on said one of the amplitude distortion and the phase distortion weighted by a probability density function of a power/average power ratio of a predetermined modulated signal; and

a linear index calculator for calculating said linear index from the result of said integrating process performed by said integration processor.

9. An evaluating device for evaluating a linear index in a system under test in an electric circuit, comprising:

a measuring device for measuring an input signal input to and an output signal output from said system under test to which a predetermined evaluation signal has been input;

an evaluator for determining at least one of an amplitude distortion and a phase distortion of said output signal, using said input signal and said output signal;

an integrator for performing an integrating process on said one of the amplitude distortion and the phase distortion weighted by a probability density function of a power/average power ratio of a predetermined modulated signal; and

a linear index calculator for calculating said linear index from the result of said integrating process performed by said integrator.

10. A communication circuit including a system under test which is to be estimated for a linear index, comprising:

a signal generator for generating a predetermined evaluation signal and inputting the evaluation signal to said system under test;

an evaluating circuit for measuring an input signal input to and an output signal output from said system under test to which said evaluation signal has been input, and determining at least one of an amplitude distortion and a phase distortion of said output signal, using said input signal and said output signal; and

a calculator for performing an integrating process on said one of the amplitude distortion and the phase distortion weighted by a probability density function of a power/average power ratio of a predetermined modulated signal, and calculating said linear index from the result of said integrating process.

11. A communication circuit according to claim 10, further comprising:

a control circuit for applying said evaluation signal from said signal generator successively to a plurality of said systems under test according to different communication processes, and selecting one of said systems under test for communicating operation, based on said linear indexes calculated by said calculator respectively for said systems under test.

12. A communication circuit according to claim 10, further comprising:

a control circuit for controlling an average power level of said evaluation signal from said signal generator based on said linear index calculated by said calculator.

13. A communication circuit according to claim 10, further comprising:

a control circuit for controlling a biasing condition for said system under test depending on said linear index calculated by said calculator.

14. A communication circuit according to claim 10, further comprising:

a control circuit for controlling an impedance condition for said system under test depending on said linear index calculated by said calculator.

15. A communication circuit according to claim 10, further comprising:

a control circuit for controlling at least one of a phase and an amplitude of said input signal when said input signal is input to said system under test, depending on said linear index calculated by said calculator.

16. A program for evaluating a linear index in a system under test in an electric circuit, comprising the steps of:

inputting a predetermined evaluation signal to said system under test;

determining at least one of an amplitude distortion and a phase distortion of an output from said system under test to which said evaluation signal has been input;

performing an integrating process on said one of the amplitude distortion and the phase distortion weighted by a probability density function of a power/average power ratio of a predetermined modulated signal; and

calculating said linear index from the result of said integrating process.