What happen to yield to maturity on bonds in the marketplace, if inflation increase?
YTM on a bond priced at par is simply the coupon.
The calculation of YTM takes into account the current market price, par value, coupon interest rate and time to maturity.(1)
Higher inflation usually results in increased fed funds rates, which in turn drive up coupons on bonds that will be issued, making bonds already out will be less valuable (off-the-run as well as lower coupons and lower prices as demand lowers), so their YTM increases as their market price drops will drop.