What should I do with my cat who pees on the couch?

I have had my male cat for 15 years and he is peeing on the couch. He has been for about a month now and I am at my wits end. I won't give him away as my pets are my family, but I CANNOT have him peeing on the couch any more. Luckily I have found a great way 2 clean it, but it's a pain in the a**. I'm a long time cat owner and he doesn't have any type of infection of the bladder,kidneys or stones or what have you. His litter box is clean. It may have to do with jealousy of the dog as in the past he has peed on her blankets. Question is not how to stop him from doing this because I no longer think there is a way. uestion is: how do I deal with it? I have thought of putting a diaper on him and then taking it off a couple times of day and putting him and the litter in the bathroom. If is does not take the opportunity to use the litter box at the times his diaper is off, I have to hope that eventually he will have to as he won't be able to hold it. Can anyone think of other solutions?