You can survey Japanese patents by using Google Patent.
1) Navigate Google patent
First at all, you navigate Google Patent site.
2) Choose Advanced Search
You should pick Advanced Search on the bottom of the page.
3) Choose Japanese patent office
If you search Japanese patents, you should choose “JP”.
4) SEARCH TERMS
You can search patent by designating keywords.
If you want “Wireless” and “LAN” and (“Chip” or “Device”), you should input these words to “SEARCH TERMS”.
5) SEARCH FIELDS
You can limit these SEARCH TERMS formula in the SEARCH FIELDS.
For example,you can limit this formula by filing after January 1st, 2003.
6) Check title
You can see the details by clicking the title.
In bibliographic field data, you can check various dates and status about the patent.
In this example,
・2005224037 is an application number,
・2007040584 is a public number,
・4458486 is the registration number.
And you can confirm that it is registered and it is still active(alive) as a status.
8) Show details
You can check the details of the claims in English translation.
However, if you want to accurately grasp the contents, you need to analyse detail of the patent in Japanese.