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How Do I design mixer-oscillator (one circuit) with one transistor?
Is there any source for practical mixer-oscillators (one circuit) with one transistor?
Almost all superhet receivers use single transistor oscillator/mixer stages to produce IF ready for filtering and amplification so just about every radio you have seen uses that principle!
The design in your diagram appears to be just a modulated oscillator, I'm guessing to run at around 800 - 1000 MHz. As it has no reasonable output point ("4" will have only a small signal on it) it doesn't appear to have any mixer function.
I have related question. Assuming we have FET oscillator (5GHz). DRO/microstrip/series/parallel/etc.. configuration.
If received RF is applied to LO(drain) output port of oscillator, can we expect IF mixing product on drain?
If received RF is applied to gate of oscillator's FET, similar question.
To clarify my question, here is setup configuration:
1) DRO 5000 MHz
2) FET coupled to DRO
3) receiving antenna connected drain (or gate) of FET
incoming 5001 MHz is applied to receiving antenna, and then applied to drain or gate of FET oscillator.
- Would we see any mixing? I mean IF= 1 MHz
- Would not frequency of oscillator be "pulled" to 5001 MHz. As i understand it is kind of injected signal, so in theory 5000 MHz oscillator's frequency could float to a new point F=5001MHz...
It would be hard to predict what would happen, particularly as the capacitance of the FET would itself pull the resonator to some degree. I doubt applying 1MHz would injection lock 5GHz to 5.001GHz though, it usually takes a frequency close to the fundamental (or an integer fraction of it) to do that. If you injected 5.001GHz it probably would lock.
Using it as a mixer might work but the resulting IF would be 5.001GHz with an image at 4.999GHz, only 2MHz away and at thse frequencies it would be very difficult to keep one and eliminate the other.
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