Despite reporting a 123% jump in second-quarter profit and higher sales, shares of Qualcomm (QCOM) tumbled 6% late Wednesday on a forecast for the current quarter that was short of expectations. 

The San Diego-based designer of digital wireless telecom systems reported net income of $2.23 billion, or $1.28 a share, compared with a year-earlier $3.6 billion, or $2.10.

Excluding one-time costs, the company earned $1.01 a share, ahead of average analyst estimates of 97 cents in a Thomson Reuters poll.  

Revenue for the three months ended March 25 was up 28% to $4.94 billion from $3.8 billion a year ago, trumping the Street’s view of $4.84 billion.

Qualcomm CEO Paul Jacobs said he was pleased with the growth in demand for 3G- and 4G-enabled devices across both developed and emerging regions. The company makes much of its profit on licensing patents related to its 3G technology.  

The company even lifted its full-year forecast, now expecting non-GAAP 2012 earnings in the range of $3.61 to $3.76 a share with revenue between $18.7 billion and $19.7 billion. Analysts are looking for slightly higher profit of $3.77 a share on sales of $19.39 billion.

But for the third quarter, Qualcomm said it expects a per-share profit of just 83 cents to 89 cents on sales of $4.45 billion to $4.85 billion. Analysts are looking for a profit of 90 cents on revenue of $4.8 billion.

Follow Jennifer Booton on Twitter at @Jbooton