"Taking into account our new expectations for smartphone demand, we take down our March quarter, June quarter and full year estimates for wireless companies under coverage."

On Tuesday "our research colleagues in Asia reduced their estimates for EMS [electronics manufacturing service] builds for Apple iPhones for the March and June quarters of 2018," analyst Bill Peterson wrote in a note to clients Wednesday entitled "Trimming Estimates on Smartphone Demand Weakness."

J.P. Morgan is seeing more evidence Apple iPhone demand is deteriorating, predicting weaker than expected sales results for the smartphone maker's suppliers this year.

Peterson noted the firm's Asian supply chain analysts lowered their iPhone production forecasts to 55 million from 60 million for the March quarter and to 45 million from 50 million for the June quarter.

The suppliers' "non-mobile business fundamentals remain strong, but not enough to overcome weakening Apple demand," he wrote.

As a result, the analyst reduced his 2018 sales forecast for Skyworks Solutions to $4.11 billion from $4.24 billion. The Wall Street consensus is $4.13 billion.

He also lowered his 2018 sales forecast for Knowles to $772 million from $779 million compared to the Street's expectation of $798 million.

Peterson reaffirmed his neutral ratings for Skyworks and Knowles.

Skyworks manufactures radio frequency semiconductors, which enable smartphones to communicate with wireless networks. Apple represented nearly 40 percent of the company's fiscal 2016 sales, according to the analyst.

Knowles makes audio microphones for smartphones and other consumer electronics products.

Skyworks shares traded roughly even Wednesday, while Knowles stock dropped 1.5 percent.