The title of the upcoming No Doubt album, ''Return of Saturn'' (due April 11), refers to the 29- year cycle that it takes the ringed planet to circle the sun. Astrology buffs believe this planetary boomerang helps explain why some folks become particularly self- analytical as their 30th birthday approaches. So you don't have to be Jeanne Dixon to figure out that singer Gwen Stefani recently turned the big three- oh.

''We ended up calling the album 'Return of Saturn' because on a personal level, from age 28 to now - - the time frame of the making of this album - - was really hard,'' Stefani tells EW Online. ''I was like, 'God, what's wrong with me, who am I?,' going through this whole evaluation of who I was in different stages of life and which one's real.''

Fans may feel like Saturn has been around the sun once or twice since the group's last album, ''Tragic Kingdom,'' came out. It's only been five years, but that's close enough to 29 when measured in ephemeral pop- music, fickle- fan years. ''I think there's a question that we may have lost some of the momentum we built up off the last record,'' admits bassist Tony Kanal, ''but all in all this is a much better way to approach it, cutting the right record and putting it out when it was ready. I'm glad we made that commitment to take our time and stuck to it.'' In fact, the first single, ''Ex- Girlfriend,'' which was just released to radio, was ''a last- minute addition to the record,'' Kanal explains. ''We needed one more up- tempo song to balance it out.''

The fact that the album has so many mid- tempo tunes indicates that there'll be no getting around the M- word this time: Matured. Stefani pines for a ''Simple Kind of Life'' in one song and begs someone to ''Marry Me'' in another. Is this the SoCal party band fans used to know and love? ''Being a party band is great,'' Kanal allows. ''Making people happy is the bottom line. But these are very real, intense, sincere lyrics. They're coming from Gwen's heart. I think people will latch onto that when they realize how real it is.''

Stefani agrees that her fans will probably follow her on her journey into lyrical adulthood: ''What I've learned is that I'm like a standard mold, because it seems just from touring and meeting people and having them respond to the music, for some reason they really respond to what I respond to. And maybe the same people that liked our last record are a few years older, like I am, you know what I mean? So hopefully they can grow with us.''

Musical growth was on the agenda too. ''We made sure we went through lots of painful avenues'' in the recording process, Stefani says, including trying out a couple of different producers before settling on Glen Ballard, of Alanis Morissette fame. But he didn't get quite as involved as he's famous for on other projects. ''We didn't really do any songwriting with him,'' Stefani says. ''This record was a chance for us to prove that we could get better as songwriters. It was weird to think that you could just kind of cheat and go, 'Hey, Glen, what would you write right here?' Because the guy is an amazing songwriter. But he pretty much was the team leader and helped us all get along with each other and'' - - perhaps most importantly - - ''made us finish.''

But don't expect too much on the old- fashioned ska front that first made the quartet famous. ''It's really hard to pigeonhole us now,'' says Kanal. ''In the past people have thrown us into the ska or new wave [camps], trying to put different labels on us. I understand how people feel the need to do that. But as far as I'm concerned, I think we're just a true American rock band.'' Hey, that has a... ring to it.