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Infringement search: communication device patents

This example is about a Japanese prior art search to invalidate a target US patent about adjustment of time and frequency domain equalizers in a communications device, an infrigement litigation case.


Japanese documents published before 2004

Databases used:
NRI, Patolis, and JPO/IPDL combination

Patent infringement litigation case

In this project, we used full text, classification, cross-reference, and combination of these search approaches to cover a wide scope. These Japanese patent searches generated 589+ hits.
Search strings used and number of hits generated are summarized below for reference.

Search strings used:
(“equalizer” OR “equalization”) AND “frequency domain” AND “time domain” AND (H04B1/+ H03H7/+ H01Q21/+ H04Q7/+ H04B7/+ H04L12/)

After screening and reviewing full documents of these hits, we uncovered 7 Japanese documents that are considered to be relevant art. One of the patent found discloses a training method of a time domain equalizer and digital data transmission apparatus comprising a time domain equalizer and frequency domain equalizer. Tap-coefficient is updated so that an error between the tap coefficients and channel target characteristic becomes zero.

Searching Japan patents for wireless communication system

Full text and IPC were used. For infringement litigation case.