Town are unbeaten in seven on their home turf with four straight, clean sheets at Highbury.
But now Joey Barton’s side are preparing to host the team with the best away record in the division.
Kenny Jackett’s side have lost just once on their travels this term, but after Town overcame promotion hopefuls Doncaster Rovers 3-0 on Boxing Day Madden says they are full of confidence.
The 12-goal forward said: “It is a great game to be involved in.
“Portsmouth have shown in the first half of the season that they deserve to be up there.
“It is up to us to spoil their party. We will go into that full of confidence.
“We’ve had four clean sheets in a row at home and some convincing wins in there.
“We are full of confidence at home and we are looking for another three points.”
Madden netted twice against Doncaster, with Ash Hunter’s goal sandwiching the Irishman’s brace
And the striker says the first goal is key in this division as Rovers became the first team Town have done the double over this season, following their 4-0 win at the Keepmoat in October.
He added: “A lot of character was shown from the boys.
“Donny are a good side, so to beat them convincingly again is a great confidence- booster.
“In the first half we were not at our best but the gaffer had a few words with us at half-time, got us going and we were at our best in the second half.
“The shape and structure were better in the second half and we looked to get them on the counter-attack.
“It was a bit like when we played them away from home.
“They are a possession- based team and they have a good squad.
“But we managed to get the first goal and that dampens their spirits, then we go on from there.”
Ched Evans was eligible to play after his red card at Bristol Rovers was overturned on appeal.
And Madden says the removal of loanee Evans’ potential three- game ban was a massive boost for the squad and he dubbed his strike partner a focal point of this Town side.
Asked about the importance of Evans’ reprieve, Madden said: “It’s massive. He is such a big player for us, a focal point.
“He pins defenders and that is his strength, which gives me the licence to run off him.
“That is probably why we work so well because we have different styles. It is a big bonus for the squad to have him back.”