Atek HP 8753D, Руководство пользователя, Страница: 152 / 677

Conversion Compression Using the Frequency Oset Mode
Conversion compression is a measure of the maximum RF input signal level, where the mixer
provides linear operation. The conversion loss is the ratio of the IF output level to the RF input
level. This value remains constant over a specied input power range . When the input power
level exceeds a certain maximum, the constant ratio between IF and RF power levels will begin
to change . The point at which the ratio has decreased 1 dB is called the 1 dB compression
point. See Figure 3-19.
Figure 3-19.
Conversion Loss and Output P ower as a Function of Input P ower Level Example
Notice that the IF output power increases linearly with the increasing RF signal, until mixer
compression begins and the mixer saturates .
The following example uses a ratio of mixer output to input power and a marker search
function to locate a mixer's 1 dB compression point.
1. Set the LO source to the desired CW frequency and power level.
CW frequency = 600 MHz
P ower = 13 dBm
2. Initialize the analyzer by pressing 4 PRESET 5 .
3. T o set the desired CW frequency and power sweep range , press:
4 MENU 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
SWEEP TYPE MENU
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
POWER SWEEP
NNNNNNNNNNNNNNNNNNNN
RETURN
NNNNNNNNNNNNNNNNNNNNNNN
CW FREQ
4
800
5 4
M/
5
NNNNNNNNNNNNNNNNN
POWER
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
PWR RANGE MAN
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
POWER RANGES
NNNNNNNNNNNNNNNNNNNNNNN
RANGE 0
4
ST ART
5 4
010
5 4
x1
5
4
STOP
5 4
10
5 4
x1
5
4. Make the connections , as shown in Figure 3-20.
3-28 Making Mixer Measurements