RF Micro Devices

(RFMD)

warned after the close that it will post a loss considerably worse than expected because its customers have been buying relatively low-margin products.

RF Micro, which sells semiconductors to the communications industry -- cell-phone giant

Nokia

(NOK) - Get Report

is its largest customer -- closed regular trading up 5 cents, or 0.8%, to $6.05. After the close, shares slipped 36 cents, or 6%, to $5.69.

In a statement, the company said demand was weaker for higher-end CDMA devices used in cell phones, with the demand shifted to lower-cost GSM components.

For the March quarter, the company now expects to post a loss of 5 cents to 7 cents per share, compared to its January outlook for break-even to a penny loss.

Sales are running slightly ahead of guidance, with an expected $138 million compared to RFMD's earlier forecast of $135 million.

Analysts had been expecting the company to break even on revenue of $135 million, according to First Call/Thomson Financial.