about radio and tuner

hello every one
i want any information about how digital radio work "like cell phone radio" or about digital tuner i.e i want change radio channel using keyboard i search alot and not found any thing just IC do all radio job i don't need that that all.

welcome!
you can read few articles from elektor UK magazine , say from march 2004 and may2007
they published articles of USB based radio designs with full info like software etc. you need to register at ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement