5-4 :Format Subsystem VNA Commands
5-42 PN: 10580-00319 Rev. N S412E PM
Converting REAL,32 Example:
The instrument returns the following values in REAL,32 format:
00 31 2a 47 [real], 00 e8 6a c6 [imag]
1. Convert from little endian to big endian:
47 2a 31 00 [real], c6 6a e8 00 [imag]
2. The binary representation of the real portion, 47 2a 31 00 is:
01000111 00101010 01110001 00000000
3. Binary is in IEEE format:
• 1st bit is sign bit
• next 8 bits are exponent
• next 23 bits are normalized value
4. Convert binary to decimal:
0, the MSb is the sign bit
10001110, exponent. The actual exponent value is this value minus 127. So, it is
142 – 127 = 15.
0101010 01110001 00000000 (as normalized value) and adding 1 and multiplying
by 2^exponent results in 1+(0/2+1/4+0/8+1/16+0/32+1/64+...) * 2^15 = 43520
(approx.)
5. Repeat steps 2 through 4 for the imaginary portion.
c6 6a e8 00 in binary is 11000110 01101010 11101000 00000000
The MSb is the sign bit
The next 8 bits is the exponent, which is 10001100. The actual value is 140 – 127
= 13
Converting the remaining bits and multiplying by exponent and accounting for
sign, results in –(1+(1/2+1/4+0/8+1/16+0/32+1/64...) * 2^13) = –14976 (approx).
6. Take out the 1e6 scale factor from both parts:
.043520 [real], –.014976 [imag]
7. Finally, convert the values to dB:
10*log((.043520)^2 + (-.014976)^2) = –26.7401848 dB
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