It is actually a switching mixer (not non-linear), but instead of diodes it used the multiplexer switches.This is not a real mixer. A tricky way has been used but not worth.
If you wanna use a real Mixer, look at NXP SA/NE series mixers/modulators or equivalents.
Hm...Depends on modulation signal characteristics. Due to AC coupling, the given circuit gives only correct output if the modulation is DC-free.
Thanks a lot.You are apparently confusing balanced mixer with quadrature mixer.
For SSB modulation/demodulation, RF and LO must be 90 degree phase shifted.
The output spectrum is much cleaner with the gilbert cell mixer!This Mux/Demux CMOS chip will produce a suppressed carrier ( maybe 30~40 dB) but the MUX has a digital input threshold so it is not a linear LO. Thus your square wave might give similar results to a biased sine wave. The differential RF is needed to suppress the carrier should have low inverter latency or use 20MHz /2. e.g. https://tinyurl.com/276uvbfg in my simulation.
But isn't SSB a linear signal? So a linear mixer is needed such as Gilbert mixers and other linear mixer types.
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Gilbert cell ( discrete version ) Due to limitations of Falstad's autoplot of spectrum, I used 300 kHz to show the suppressed carrier for your 3kHz LO
It is balanced 10MHz from the D-FF divide by 2 and symmetrical complementary outputs.
So in order for this NE602 chip to work as a balanced mixer (and thus suppressing the input signal at its output) the input signal at the pins 1 and 2 must be of equal amplitude on each pin (1 and 2) and at 180 degrees difference between them.Balanced complementary RF inputs on pins 1&2 means both matching of amplitudes and matching opposite phase which determines the dB of carrier suppression and imbalance of USB and LSB.
So E looks to be the best of these types..
So it does NOT require a balanced input at pins 1 and 2 in order to be used as a balanced mixer? Right?I said it wrong. It's just using the differential amplifier suppresses common mode noise such as signals sharing noise from the supply or ground.
Thank you.Due to the simple SA 602 input configuration, RF suppresion will be probably better with true differential input.
To get the advantage of a linear mixer, 3 kHz LO signal must be sine rather than square wave. Otherwise there's no adavantage over CMOS switch solution.
The answer to your first question is: this is a single-balanced mixer, not a double balanced mixer.Is this switching mixer considered a double balanced mixer?
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