Upvote:2
There's no such thing as a "new 180-day period" -- every sequence of 180 consecutive days counts. In order to stay 90 days in a row, you need to have been outside the Schengen area for all the 90 days immediately before you enter -- this is necessary to follow the rule for the 180-day period that has your 90-day stay as its last half, and periods earlier than that will then automatically follow the rule too.
You can use the official Schengen calculator to verify this.