Antenna design method and apparatus

1. An antenna design method executed by a computer, the antenna design method comprising:

creating an antenna model including an antenna which includes a plurality of antenna elements and matching circuits which are respectively connected to the plurality of antenna elements and which includes a matching element including a parasitic reactance and a loss resistance;

obtaining a characteristic of the antenna and a characteristic of the matching element;

calculating a total efficiency of the antenna model using the obtained characteristic of the antenna and the obtained characteristic of the matching element, the total efficiency of the antenna model being a ratio of a total input power from a wave source to a radiation power from the antenna;

judging whether or not the calculated total efficiency of the antenna model satisfies a desired total efficiency of the antenna; and

displaying result of the judgment.

2. The antenna design method according to claim 1 , wherein

the characteristic of the antenna includes an S parameter of the antenna, the characteristic of the matching element includes an impedance of the matching element, and the characteristic of the antenna includes an S parameter of the antenna model, and

the computer calculates an F parameter of the antenna using the S parameter of the antenna, calculates an F parameter of the matching circuit using the impedance of the matching element, and calculates the S parameter of the antenna model using the calculated F parameter of the antenna and the F parameter of the matching circuit.

3. The antenna design method according to claim 2 , wherein

the computer calculates the total efficiency of the antenna model by assuming that a ratio of a sum of a radiation efficiency of the antenna and a loss in the antenna to the radiation efficiency is equal between a model of the antenna alone and the antenna model.

4. The antenna design method according to claim 1 , wherein

when the matching element is mounted in parallel to the antenna, the computer calculates an inductance of a via connected to the matching element, and calculates the total efficiency of the antenna model using the calculated inductance of the via.

5. The antenna design method according to claim 1 , wherein

the computer selects the matching element comprised in the matching circuit by referring to a matching element data file including data about a usage condition of the matching element.

6. The antenna design method according to claim 1 , wherein

when the computer judges that the total efficiency of the antenna model does not satisfy the desired total efficiency of the antenna, the computer displays a power consumption of the matching element.

7. The antenna design method according to claim 1 , wherein

the computer

creates an antenna model including lines respectively connected to the plurality of antenna elements in addition to the antenna and the matching circuit;

obtains characteristics of the lines; and

calculates the total efficiency of the antenna model using the obtained characteristics of the lines in addition to the obtained characteristic of the antenna and the obtained characteristic of the matching element.

8. The antenna design method according to claim 1 , wherein

when it is judged that the calculated total efficiency does not satisfy the desired total efficiency of the antenna, the computer:

replaces one of the plurality of matching elements included in the antenna with another matching element, an element value of each of the another matching element and the one of the plurality of matching elements being the same and a loss resistance of the another matching element being smaller than the one of the plurality of matching elements; and

performs the creating, the obtaining, the calculating, the judging and the displaying again.

9. An antenna design apparatus comprising:

a processor which performs a process including:

creating an antenna model including an antenna which includes a plurality of antenna elements and matching circuits which are respectively connected to the plurality of antenna elements and which includes a matching element including a parasitic reactance and a loss resistance;

obtaining a characteristic of the antenna and a characteristic of the matching element;

calculating a total efficiency of the antenna model using the obtained characteristic of the antenna and the obtained characteristic of the matching element, the total efficiency of the antenna model being a ratio of a total input power from a wave source to a radiation power from the antenna; and

judging whether or not the calculated total efficiency of the antenna model satisfies a desired total efficiency of the antenna, and

a display which displays result of the judgment by the processor.

10. The antenna design apparatus according to claim 9 , wherein

when it is judged that the calculated total efficiency does not satisfy the desired total efficiency of the antenna, the processor:

replaces one of the plurality of matching elements included in the antenna with another matching element, an element value of each of the another matching element and the one of the plurality of matching elements being the same and a loss resistance of the another matching element being smaller than the one of the plurality of matching elements; and

performs the creating, the obtaining, the calculating, and the judging again, and

the display displays result of a retry of the judgement by the processor.

11. A non-transitory computer-readable recording medium having stored therein an antenna design program for causing a computer to execute processes comprising:

creating an antenna model including an antenna which includes a plurality of antenna elements and matching circuits which are respectively connected to the plurality of antenna elements and which includes a matching element including a parasitic reactance and a loss resistance;

obtaining a characteristic of the antenna and a characteristic of the matching element;

calculating a total efficiency of the antenna model using the obtained characteristic of the antenna and the obtained characteristic of the matching element, the total efficiency of the antenna model being a ratio of a total input power from a wave source to a radiation power from the antenna;

judging whether or not the calculated total efficiency of the antenna model satisfies a desired total efficiency of the antenna; and

displaying result of the judgment.

12. The non-transitory computer-readable recording medium according to claim 11 , wherein

when it is judged that the calculated total efficiency does not satisfy the desired total efficiency of the antenna, the antenna design program causes the computer to execute processes including:

replacing one of the plurality of matching elements included in the antenna with another matching element, an element value of each of the another matching element and the one of the plurality of matching elements being the same and a loss resistance of the another matching element being smaller than the one of the plurality of matching elements; and

performing the creating, the obtaining, the calculating, the judging and the displaying again.