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4
EXT_VCO Modulator Linearity Validation
To test the external VCO / LO, turn off the LO section and apply LO signal at the EXT_VCO SMA
connector. As an example, consider a frequency of 1986.56 MHz:
1. Use the GUI settings as shown in
2. Since LO_DIV_SEL is Div2, apply a 3973.12-MHz signal at the EXT_VCO_IN SMA connector.
3. Use a DAC or an arbitrary waveform generator to generate two tone I/Q baseband input signals. As an
example, consider 4.5 MHz and 5.5 MHz.
4. A typical setup using Agilent's E4438C ESG vector signal generator to provide I/Q signals is as
follows:
(a) Press Preset.
(b) Press Mode → More (1of 2) → Multitone
(c) Press Initialize Table → Number of Tones → 12 → Enter.
(d) Press Freq Spacing → 1 → MHz.
(e) Press Done.
(f) Highlight each of the first 10 rows and press 'Toggle State' to turn OFF the first 10 frequencies and
only keep the last two rows with the BB frequency 4.5 MHz and 5.5 MHz ON.
(g) Press Multitone Off/On to ON to generate the multitone waveform.
(h) Adjust the differential I or Q voltage level by pressing Mode → I/Q → I/Q Output Control → I/Q
Output Atten → Enter 9 → Press dB.
(i) Set the common mode voltage to 0.25 V by pressing Mode → I/Q → I/Q Output Control →
Common Mode I/Q Offset → 250 → mV. Use a DC voltage meter to monitor the DC common
voltage at the inputs of I and Q and fine-tune the common mode voltage setting until it measures
250 mV.
SLOU385 – May 2014
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Figure 10
and
Figure
Copyright © 2014, Texas Instruments Incorporated
EXT_VCO Modulator Linearity Validation
11.
TRF3722 EVM User's Guide
9
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