Simple harmonics generator for HF signal generators
to achieve higher coverage
by sv3ora
I wanted to make my Tektronix 190 and 191
constant amplitude sinewave generators usable up to the UHF and
microwave region, so I designed this simple harmonics generator.
Its basically a high speed clipper.
Harmonics are in the usable range of -20dB to -30dB or lower but the
actual level of each individual one, depends on the drive level out of
the generator. The circuit works fine to about 6-7Vpp of input, but do
not go more than that for extended time, as the diodes will be heated a
bit.
Once upon a time, cheap signal
generators, used harmonics to achieve a very wide range. Obviously
their fundamental waveform was very distorted. To make them clean one
had to use an LPF for each frequency, or band of frequencies. Given the complexity almost
everyone used them as is. In my case, I already had quality sinewave
generators and I wanted to intentionally distort them to produce
harmonics. The good thing, is that this harmonics generator is just an
external block and can be removed whenever a clean sinewave fundamental
is needed.Also, it can be used from any other signal generator. Note that, harmonics are propagated towards the 22pF but
also towards the 10nF. However, my constant amplitude signal
generators, do not seem to be affected by this, because the main source
of signal that defines tha ALC, is the fundamental, which has a much
greater level than the harmonics.
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