RMDA20420 データシートの表示（PDF） - Fairchild Semiconductor
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RMDA20420 Datasheet PDF : 12 Pages
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Odd Harmonic Operation
Odd harmonics are generally associated with a square wave. The RMDA20420 is biased in such a way that causes the
clipping of the input sine wave to closely approximate a square wave provided a high input drive level is maintained. If biased
in a manner, which causes the input waveform to be clipped equally in the positive and negative cycles, then a symmetrical
square wave will be approximated which contains odd harmonics.
As an example, the RMDA20420 was biased as a tripler over the 20-40GHz band at selected frequencies. In this mode of
operation all the drains voltages (Vd1 and Vd2) were tied together and all the gate voltages were tied together as shown in
Figure 8.
Vd1
RF IN
Vd1 Vg2 alt Vd2
Vd3
Vd4
Vg1
Vg2
Vg3
Vg4
RF OUT
Vg1
Figure 8. RMDA20420 Configured as Tripler.
The test set up for this mode of operation is as shown in Figure 5.The biasing procedure requires the gate voltage Vg1 to
be initially set to –1.0V. Next the drain voltage Vd1 was set to +2.0V. The input frequency was selected to give the desired
tripled output and the input drive level was set to +14dBm. The output of the RDMA20420 was observed and the harmonics
of the input frequency were visible on the spectrum analyzer display. The gate voltage Vg1 was adjusted gradually to peak
the third harmonic. Lowering Vg1 resulted in peaking the third harmonic. Then the drain voltage Vd1 was adjusted to tweak
the power level of the third harmonic. Tweaking Vg1 and Vd1 at this point resulted in further optimization of the desired
harmonic or suppression of the unwanted harmonic as required. The range for Vg1 was between –0.1 to –0.6V and the
range for Vd1 was between +1.1 to +1.8V. The above procedure was repeated for each input frequency tested.
Figure 9 shows the tripled output for the RMDA20420 biased as described above. Input frequencies were selected to give
tripled frequencies falling in the 21 to 39GHz band. The graph shows tripled output powers greater than +10dBm up to
39GHz. The power levels of the first and second harmonics were also plotted to show the level of suppression of the
unwanted harmonics. The graph shows for a tripled frequency of 30GHz the output power was +14dBm, the fundamental
(10GHz) power level was –17dBm and the second harmonic (20GHz) power level was +3 dBm. The conversion gain for the
tripled output at 30GHz was 0dB. For tripled frequencies between 21 to 39GHz, the conversion gain was better than –4dB.
©2004 Fairchild Semiconductor Corporation
RMDA20420 Rev. D
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