Ralph Bernard, DRDB chairman, said: "Ian indicated his intention to leave DRDB several months ago in order to give plenty of notice to us.
"His long planned and amazing round-the-world sailing trip with his wife begins in the autumn, when he will leave DRDB."
Dickens said: "I joined the DRDB after 20 years marketing experience in UK consumer electronics and I believe I have met the challenge the board set for me back in 2002.
"Today, radio has evolved, and I feel the next step in DAB's development requires someone with expertise and knowledge in new target areas."
News of his departure coincides with a DRDB announcement that more than five million DAB radios have been sold in the UK, according to GfK, the consumer electronics industry's research body.