Table 1.

Time Domain Tag Comparison.

Tag Design	Year	Major Dimensions	Bits Encoded	Operating Frequency	Interrogation Signal	Reported Read Range	Reader Architecture	Advantages	Disadvantages
SAW	2002 [66]	n/a	64	2.44 GHz	Sinusoidal pulse	n/a	n/a	High Density	Tight manufacturing tolerances
	2004 [67]	n/a	<256	2.45 GHz	Sinusoidal pulse	n/a	n/a	High Density	Tight manufacturing tolerances
	2014 [12]	0.8 × 2.1 mm *	n/a	2–2.5 GHz	LFM Chirp	n/a	n/a	Very Compact	Requires UWB interrogation
	2004 [68]	1 cm length *	n/a	250 ± 50 MHz	Stepped Chirp	n/a	n/a	Robust in multi-sensor environment	Needs accurate reflector design
TFT	2013 [69]	3.9 × 1.5 mm *	16	n/a	Sinusoid	n/a	13.56 MHz RFID Reader	Compact	Uses 222 transistors
	2006 [61]	n/a	64	13.56 MHz	Sinusoid	n/a	13.56 MHz RFID Reader		Uses 1938 TFTs
	2011 [70]	7 × 10 mm	n/a	13.56 MHz	Sinusoid	90 mm	RFID Reader	Works at 13.56 MHz	Uses 1026 TFTs
	2015 [71]	54 cm2 *	4	13.56 MHz	Sinusoid	50 mm	RFID Reader	Works at 13.56 MHz	Uses 250 TFTs. Needs large supply voltage
	2017 [57]	6 × 8.3 mm	96	13.56 MHz	Sinusoid	NFC Design	NFC-Enabled Device	Compact	Unclear if it is capable of >1 m read range
	2018 [72]	3 × 9 mm *	n/a	Up to 20 MHz	Sinusoid	n/a	RFID Reader	Suitable for Roll-to-Roll fabrication and 20 MHz operation	Not a completed tag
	2013 [62]	34 mm2 *	8	n/a	Sinusoid	n/a	n/a	Compact. Printed with inkjet technology	Not fully integrated into RFID system
Basic Reflection Tag	2008 [41]	Length > 400 mm *	8	1–3 GHz	Sinusoidal pulse	n/a	TDR Module	Simplistic design	Very sensitive to interference
Basic Delay Line	2006 [40]	11.2 × 5.3 cm * (***)	4	915 MHz	Sinusoidal pulse	n/a (no wireless element)	RF Generator	Simplistic design	Bit-density is highly driven by pulse duration. Relatively large. Requires isolators
	2007 [73]	n/a	4	915 MHz	Sinusoidal pulse	25.4 cm	VNA (HP4396B)	Simplistic design	Requires isolators, circulators, etc. Scalability and robustness are questionable
UWB Delay Line	2011 [28]	57 × 70 mm ***	n/a (3 possible values)	3.1–10.6 GHz	UWB Impulse	1.5 m	IR-UWB Radar	No template response needed. Tested at long range	Dual planar, relatively large
	2008 [42]	23 × 31 mm	n/a (3 possible values)	3.1–10.6 GHz	UWB Impulse	0.8 m	n/a	Readily supports IR-UWB Radar interrogation	Dual Planar
CRLH Delay Line	2008 [45]	120 × 14 × 10 mm *	4	Between 2.2 GHz and 4 GHz	Sinusoidal pulse	n/a	n/a	CRLH TL Implemented	Tight tolerances, dispersion issues and high losses occur with CRLH transmission lines
	2009 [44]	Length = 26 cm *	6.2	2.2 GHz	Sinusoidal pulse	n/a	Described in Reference [74]	Implements QPSK
	2017 [49]	Approximate Length = 12 cm *	2	2.4 GHz	Sinusoidal pulse	14 cm	n/a	More Compact
Group Delay Tag	2010 [52]	Width > 37.5 mm *	3	2–4 GHz	Chirp or discrete frequencies	n/a	n/a	Fully printable design	Requires UWB interrogation. Odd Harmonics exist, limiting address space
	2013 [75]	10 × 8 cm (2 × 3 cm without antennas)	10 **	n/a	Chirp	30 cm	VNA (PNA N5222A)
MIW Tag	2012 [76]	Height > 20 mm *	2	2.45 GHz	Sinusoidal pulse	n/a	VNA (E8364B)	Fully Printable	Large losses and tight tolerances for Metamaterial Structures and MIW supporting structures
	2018 [77]	28 × 16 mm *	2	2.9 GHz	Sinusoidal pulse	>1 cm	VNA (N9918A FieldFox)

* Without Antenna, ** Used as sensor, *** The bit-density of this tag could be much higher if the pulse duration was lower.