Table 4.

Relation between the minimum radiated power (P_min) and reading range (RR) of the investigated UHF RFID reader used with tags of different sensitivity.

Reading Range (RR), cm	Minimum Power Radiated from the UHF RFID Reader to Energize Particular Tags (Pmin), W
	The Sensitivity of Used Tags, Expressed by the Minimum Strength of the Electric Field Required to Energize Them (Etag), V/m
	0.6	0.8	1.0	1.3	1.6	2.0
50	0.002	0.004	0.005	0.009	0.014	0.022
100	0.008	0.014	0.022	0.037	0.055	0.087
150	0.018	0.031	0.049	0.082	0.13	0.20
200	0.031	0.055	0.087	0.15	0.22	0.35
300	0.070	0.12	0.20	0.33	0.50	0.78
400	0.13	0.22	0.35	0.59	0.89	1.2
500	0.20	0.35	0.54	0.91	1.4	2.2
600	0.28	0.50	0.78	1.3	2.0	3.1
700	0.38	0.68	1.1	1.8	2.7	4.2
800	0.50	0.89	1.4	2.3	3.5	5.5
1000	0.78	1.4	2.2	3.7	5.5	8.7
1500	1.8	3.1	4.9	8.2	12	19

Note: analyzed UHF RFID GUN antenna—microstrip patch antenna with a patch of 99.6 × 122.5 mm placed on substrate and a ground of 131.5 × 138.3 mm, operated at a frequency of 865 MHz; values in bold—the level of emission which needs in Europe administrative permission for use in RFID systems.