BALANCE SHEET COMPONENTS

Accounts receivable include amounts that are unbilled at the end of the period that are expected to be billed and collected within a

-month period. Unbilled accounts receivable, included in accounts receivable, totaled

$22.7

million and

$22.2

million as of

September 30, 2018,

and

December 31, 2017,

respectively. Unbilled accounts receivable that are

not

expected to be billed and collected during the succeeding

-month period are recorded in other non-current assets and totaled

$6.4

million and

$8.6

million as of

September 30, 2018

and

December 31, 2017,

respectively.

Property and equipment, net consists of (in thousands):

	September 30,			December 31,
(Dollars in thousands)	2018			2017
Computer equipment	$	10,446		$	10,729
Software		4,121			3,348
Furniture, fixtures and equipment		4,420			3,676
Leasehold improvements		5,573			1,980
Test equipment		14,694			13,796
Construction-in-progress		17,928			12,527
		57,182			46,056
Less: accumulated depreciation and amortization		(23,062	)		(20,670	)
Total	$	34,120		$	25,386

Test equipment includes some DFI assets at customer sites that are contributing to DFI solution revenues. The construction-in-progress balance as of

September 30, 2018

and

December 31, 2017

was primarily related to construction of DFI assets. Leasehold improvements increased to

$5.6

million due to a recent move of the Company’s headquarters to a new office location. Depreciation and amortization expense was

$1.2

million and

$1.3

million for the

three

months ended

September 30, 2018

and

2017,

respectively. Depreciation and amortization expense was

$3.7

million and

$3.5

million for the

nine

months ended

September 30, 2018

and

2017,

respectively.

As of both

September 30, 2018,

and

December 31, 2017,

the carrying amount of goodwill was

$1.9

million.

Intangible assets balance was

$5.3

million and

$6.1

million as of

September 30, 2018,

and

December 31, 2017,

respectively. Intangible assets as of

September 30, 2018

and

December 31, 2017

consist of the following (in thousands):

				September 30, 2018							December 31, 2017
	Amortization			Gross					Net		Gross					Net
	Period			Carrying		Accumulated			Carrying		Carrying		Accumulated			Carrying
(Dollars in thousands)	(Years)			Amount		Amortization			Amount		Amount		Amortization			Amount
Customer relationships	1	-	9	$	6,740	$	(4,421	)	$	2,319	$	6,740	$	(4,145	)	$	2,595
Developed technology	4	-	6		15,820		(13,261	)		2,559		15,820		(12,829	)		2,991
Tradename	2	-	4		790		(641	)		149		790		(622	)		168
Patent	7	-	10		1800		(1,510	)		290		1,800		(1,480	)		320
Total				$	25,150	$	(19,833	)	$	5,317	$	25,150	$	(19,076	)	$	6,074

The weighted average remaining amortization period for acquired identifiable intangible assets was

6.1

years as of

September 30, 2018.

For the

three

and

nine

months ended

September 30, 2018,

total intangible asset amortization expense was

$0.3

million and

$0.8

million, respectively. For the

three

and

nine

months ended

September 30, 2017,

total intangible asset amortization expense was

$0.2

million and

$0.6

million, respectively. The Company expects annual amortization of acquired identifiable intangible assets to be as follows (in thousands):

Year ending December 31,	Amount
2018 (remaining three months)	$	253
2019		1,009
2020		1,009
2021		833
2022		626
2023 and thereafter		1,587
Total future amortization expense	$	5,317

Intangible assets are amortized over their useful lives unless these lives are determined to be indefinite. Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group

may

not

be recoverable. During the

three

and

nine

months ended

September 30, 2018,

there were

indicators of impairment related to the Company’s intangible assets.