Anritsu BTS Master, Руководство пользователя

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2-12 Field Strength Spectrum Analyzer
2-16 PN: 10580-00349 Rev. M Spectrum Analyzer MG
4. Press the
Freq
main menu key, press the
Center Freq
submenu key, and enter the
center frequency.
5. Press the
Span
main menu key. Set the span wide enough to include the primary
channel bandwidth and upper and lower channel bandwidths. At least a portion of the
span has to include a frequency within the antenna’s specified range.
6. Press the
BW
main menu key and verify that
Auto RBW
and
Auto VBW
are
On
.
7. To change the units of measurement, press the
Amplitude
main menu key, then press
the
Units
submenu key and press
dBm/m
2
,
dBV/m
,
dBmV/m
,
dBµV/m
,
Volt/m
,
Watt/m
2
,
dBW/m
2
,
A/m
,
dBA/m
, or
Watt/cm
2
. The instrument automatically adjusts the
measurement by the antenna factors selected. Marker values will be displayed in the
same units as selected for amplitude.
Antenna Calculations
The following is a list of various antenna calculations should you find it necessary to convert
from one parameter to another:
Conversion of signal levels from watts to volts in a 50 ohm system:
P = V
2
/R
where:
P = power in Watts
V = voltage level in Volts
R = resistance in ohms
Note that 1mW = 10
–3
W and 1µV = 10
–6
V.
For power in dBm, and voltage in dB (µV):
V
dB(µV)
= P
(dBm)
+ 107 dB
Power density to field strength:
An alternate measure of field strength is power density:
P
d
= E
2
/ 120

where:
E = field strength in V/m
P
d
= Power density in W/m
2
Power density at a point:
P
d
= P
t
G
t
/ (4

r
2
)
where:
P
d
= power density in W/m
P
t
= power transmitted in Watts
G
t
= gain of transmitting antenna
r = distance from the antenna in meters
This equation is only valid in the far field, where electric and magnetic fields are related by
the characteristic impedance of free space.