Intangible Assets

In connection with our acquisitions of Silicon Image, Inc. in March 2015 and SiliconBlue Technologies, Inc. in December 2011, we recorded identifiable intangible assets related to developed technology, customer relationships, licensed technology, patents, and in-process research and development based on guidance for determining fair value under the provisions of ASC 820, "Fair Value Measurements." Additionally, during fiscal years 2015, 2017, and 2018, we licensed additional third-party technology. We do not believe there is any significant residual value associated with these intangible assets. We are amortizing the intangible assets using the straight-line method over their estimated useful lives.

During the first quarter of fiscal 2017, we sold a portfolio of patents that had been acquired in our acquisition of Silicon Image for $18.0 million. This amount was received in two installments over the first and second quarters of fiscal 2017, and was recognized as Licensing and services revenue in our Consolidated Statements of Operations during the respective periods in which the installment payments were received. As a result of this transaction, Intangible assets, net was reduced by approximately $3.5 million on our Consolidated Balance Sheets.

We monitor the carrying value of our intangible assets for potential impairment and test the recoverability of such assets annually during the fourth quarter and whenever triggering events or changes in circumstances indicate that their carrying amounts may not be recoverable. The results of our assessments are summarized below and more fully detailed in "Note 10 - Impairment of Acquired Intangible Assets."

During the third quarter of fiscal 2018, we concluded that a certain product line had limited future revenue potential due to a decline in customer demand for that product, and we recorded an impairment charge of $0.6 million to the intangible asset associated with that product. In the second quarter of 2018, we made the strategic decision to discontinue our millimeter wave business, which included certain wireless technology intangible assets, and we recorded an impairment charge of $11.9 million to the intangible assets associated with this business. During the fourth quarter of fiscal 2017, we finalized our impairment assessment procedures related to certain of the developed technology intangible assets acquired in our acquisition of Silicon Image, resulting in a $3.8 million reduction to the preliminary impairment charge of $36.2 million recorded in the third quarter of fiscal 2017, for a net impairment charge of $32.4 million in fiscal 2017. During the third quarter of fiscal 2016, we recorded a $7.9 million impairment charge to the intangible assets associated with future HDMI adopter fees.

The following tables summarize the details of our Intangible assets, net as of December 29, 2018 and December 30, 2017:



	December 29, 2018
(In thousands)	Weighted Average Amortization Period (in years)	Gross		Impairment			Accumulated Amortization			Intangible assets, net
Developed technology	5.0	$	112,269	$	(12,486	)	$	(83,185	)	$	16,598
Customer relationships	5.8	22,934		—			(19,048		)	3,886
Licensed technology	5.0	1,195		—			(354		)	841
Total identified intangible assets		$	136,398	$	(12,486	)	$	(102,587	)	$	21,325



	December 30, 2017
(In thousands)	Weighted Average Amortization Period (in years)	Gross		Impairment			Accumulated Amortization			Intangible assets, net
Developed technology	4.7	$	158,700	$	(32,431	)	$	(81,847	)	$	44,422
Customer relationships	5.7	22,934		—			(16,696		)	6,238
Licensed technology	3.5	2,392		—			(1,744		)	648
Total identified intangible assets		$	184,026	$	(32,431	)	$	(100,287	)	$	51,308

We recorded amortization expense related to intangible assets on the Consolidated Statements of Operations as presented in the following table:



	Year Ended
(In thousands)	December 29, 2018		December 30, 2017		December 31, 2016
Research and development	$	277	$	569	$	745
Amortization of acquired intangible assets	17,690		31,340		33,575
	$	17,967	$	31,909	$	34,320

The annual expected amortization expense of acquired intangible assets is as follows:



(In thousands)	Amount
2019	13,613
2020	4,499
2021	2,239
2022	238
Thereafter	736
Total	$	21,325