Hello,
I am doing FSK modulation with TRF370417, but the output amplitude is fluctuating with respect to the input.
input(Oscilloscope)
output(Signal Analyzers)
Is there any way to reduce fluctuations?
Kang-san,
The spectrum of the LOP-pin input signal is as follows. The frequency is 143.98125 MHz and the power is 7 dBm.
The spectrum of the RF_OUT-pin is as follows. The fundamental power is 2 dBm.
Hello,
have you ensure the peak of I signal and peak of Q signal are not overlapping. If there are overlap, there will be a net gain of the RF output signal per the basis of the quadrature modulation equation in the datasheet
see point #1 and #2 above.
Kang-san,
These are the I and Q signals; when the I signal is at its peak, the Q signal is at an intermediate voltage, and vice versa.
Both I and Q signals are approximately 250 mVrms.
Common-Mode Voltage is
BBIP:1.744V
BBIN:1.756V
BBQP:1.744V
BBQN:1.756V
I and Q signals in XY plot produces a circular shape.
The XY plot on the signal analyzer is this image.
Hi Okada-san,
It is possible that the TRF370417 added additional impairments such as image and local oscillator feedthrough. This is the reason that you do not have a perfect phase/dc offset at the TRF370417 output as the I/Q signal have additional imbalance from the analog artifacts. You will need to use quadrature modulator correction technique from your signal generator to correct the I/Q imbalance. The default DC offset and I/Q imbalance specifications are listed in the datasheet.
