The Bees go to Suffolk, before hosting Fulham and then traveling to Wolves for the final game of the Premier League campaign.
With his team chasing European qualification, Frank said: "I see the next game as potentially the most difficult of the three.
“That’s with big respect to Ipswich.
“They have been competitive in every game. I haven't seen them dropping in intensity, performances or willingness to work hard and run hard.
“They’re playing at home and it’s their last three Premier League games so they need to enjoy and make the most of it. We need to be absolutely up for it but I also expect us to be.”
Frank admits he's been impressed by the work of Kieran McKenna at Portman Road.
“I think Kieran is a very good manager and coach,” he added. “I think he’s proven that with what he, his coaching staff and the club have done together - going from League One to the Championship to the Premier League is remarkable.
“For whatever reason, they couldn’t stay up and there are always many factors. Kieran is a very clever coach and person, and I’m convinced that he will learn from this, reflect and come back stronger.”
Chance for Thiago
Meanwhile, Frank is eager to see Igor Thiago get a run of end of season games after missing much of the season due to injury.
He added, “Everyone who was ready for Man United is available again.We got Igor Thiago in the squad against Man United, and also on the pitch, so we were very pleased with that.
“Igor is over the worst part and getting into training. Now it’s just about giving him the right load like with any player, whether it’s a joint infection, hamstring or an ankle.
“Now he just needs to be fit enough to compete. We pushed him a bit hard to be available for the squad because we needed him. He will not start, but he had a good week of training this week, another good week next week, and we will go from there.”