It was suspected that the AD9851 DDS (Direct Digital Synthesizer) output voltage was not linear varying with the input DC control voltage, if so, that may contribute to the problem of the pulse distortion that was previously discussing, a test is done to verify this.
DC voltage is applied to the current reference input. The RSet pin is holding a 1.26V voltage, so when applying a 1.26V in DC input point, there would be no current flow in/out, that gives zero output. when DC input is 0V it's the maximum output, which is around 0dBm.
34 data points is recorded and the data is plot in DC control voltage VS RMS voltage of RF output of DDS. The conclusion is, well, the relationship IS linear.
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When bypassing the power amplifier stage, so that the DDS is feeding to the antenna directly, that gives the receiver a nice waveform, with almost no overshoot.
The overshoot problem is narrowed down to the power amplifier stage.
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