Agilent Technologies Comprehensive Guide to Reflection Calibration and VSWR Conversion for Agilent Models

Making Complex Measurements

Making a Reflection Calibration Measurement

Converting Return Loss to VSWR

Return loss can be expressed as a voltage standing wave ratio (VSWR) value using the following table or formula:

Table 2-1			Power to VSWR Conversion
	Return	VSWR		Return		VSWR		Return	VSWR	Return	VSWR	Return	VSWR
	Loss			Loss				Loss		Loss		Loss
	(dB)			(dB)				(dB)		(dB)		(dB)
	4.0	4.42		14.0		1.50		18.0	1.29	28.0	1.08	38.0	1.03
	6.0	3.01		14.2		1.48		18.5	1.27	28.5	1.08	38.5	1.02
	8.0	2.32		14.4		1.47		19.0	1.25	29.0	1.07	39.0	1.02
	10.0	1.92		14.6		1.46		19.5	1.24	29.5	1.07	39.5	1.02
	10.5	1.85		14.8		1.44		20.0	1.22	30.0	1.07	40.0	1.02
	11.0	1.78		15.0		1.43		20.5	1.21	30.5	1.06	40.5	1.02
	11.2	1.76		15.2		1.42		21.0	1.20	31.0	1.06	41.0	1.02
	11.4	1.74		15.4		1.41		21.5	1.18	31.5	1.05	41.5	1.02
	11.6	1.71		15.6		1.40		22.0	1.17	32.0	1.05	42.0	1.02
	11.8	1.69		15.8		1.39		22.5	1.16	32.5	1.05	42.5	1.02
	12.0	1.67		16.0		1.38		23.0	1.15	33.0	1.05	43.0	1.01
	12.2	1.65		16.2		1.37		23.5	1.14	33.5	1.04	43.5	1.01
	12.4	1.63		16.4		1.36		24.0	1.13	34.0	1.04	44.0	1.01
	12.6	1.61		16.6		1.35		24.5	1.13	34.5	1.04	44.5	1.01
	12.8	1.59		16.8		1.34		25.0	1.12	35.0	1.04	45.0	1.01
	13.0	1.58		17.0		1.33		25.5	1.11	35.5	1.03	45.5	1.01
	13.2	1.56		17.2		1.32		26.0	1.11	36.0	1.03	46.0	1.01
	13.4	1.54		17.4		1.31		26.5	1.10	36.5	1.03	46.5	1.01
	13.6	1.53		17.6		1.30		27.0	1.09	37.0	1.03	47.0	1.01
	13.8	1.51		17.8		1.30		27.5	1.09	37.5	1.03	47.5	1.01
							–RL
							----------
				VSWR	1 + 10		20
					= -----------------------
							–RL
							----------
						1 – 10 20

Where: RL is the measured return loss value.

VSWR is sometimes stated as a ratio. For example: 1.2:1 “one point two to one” VSWR. The first number is the VSWR value taken from the table or calculated using the formula. The second number is always 1.

Chapter 2 87