Analog Devices ADAR1000-EVALZ, Руководство пользователя

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ADAR1000-EVALZ User Guide UG-1283
Rev. A | Page 9 of 24
Setting Transmit Bias Currents
To set the nominal bias currents for the transmit variable gain
amplifiers (VGAs), vector modulators, and drivers, take the
following steps:
1. Click the TX Registers tab (see Figure 9).
2. In the Bias Current section, set TX VGA BIAS to 2, set
TX VM BIAS to 6, and set TX DRV BIAS to 6.
3. Click Write Bias Values .
16
788
-20
9
Figure 9. Setting Transmit Bias Currents
SPI Control and Enabling Transmit Mode
To operate in transmit mode, take the following steps:
1. Click the T/R Control tab (see Figure 10).
2. Select the TX EN check box to enable transmit subcircuits
in SPI control. Note that the TX_EN bit is AND’ed together
with the transmit enable bits in Register 0x02F such that
the transmit paths and subcircuits do not enable until the
TX_EN bit is asserted high.
3. Select the TR SPI check box to place the device in transmit
mode.
4. Click
Write Switch
.
Note that leaving the TR SOURCE check box cleared places the
device in SPI control mode, which is the default mode.
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678
8-
2
10
Figure 10. SPI Control, Transmit Enable, and Transmit Mode
Transmit Gain Control
To set the transmit Channel 1 gain to maximum, take the following
steps:
1. Click the TX Registers tab (see Figure 11).
2. Select the CH1 TX ATTN check box to bypass the
attenuator on Channel 1.
3. Set the TX VGA CH1 value to 127 to set the VGA to
maximum gain on Channel 1.
4. Click Write Gain Values .
1
67
88-
2
1
1
Figure 11. Setting Transmit Channel 1 to Maximum Gain in Transmit Gain
Control with All Other Channels at Minimum Gain
Transmit Phase Control
To set transmit Channel 1 to 45° phase, take the following steps:
1. Click the TX Registers tab (see Figure 12).
2. Select the
I
and
Q
check boxes under
TX VM CH1 POL
to
set the polarity bits so that the vector is in the first quadrant.
3. Set the I and Q values under TX VM CH1 GAIN to 22 for
a resulting vector of 45° phase.
4. Click Write Phase Values .
1
678
8-
2
12
Figure 12. Setting Transmit Channel 1 to 45° in Transmit Phase Control with
All Other Channels at 0°