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It is best however to have an average constant signal at the R.F. Each of the secondary’s could be used to supply ¼ of the RF signal to a separate mixer, thus 4 four mixers then adding to the final output I.F. There could be four different secondary coils to the one primary coil of the RF transformer. If the step down voltage is ¼ of the input, then an extra 6dBm in dynamic range would be found. input, attenuators could be used, or otherwise voltage step down transformers could be used. To handle high input RF signal on the R.F. In this regard, the intermodulated signal products at the output would not be so prevalent, and the 1dBm compression point would not be then reached or breached.
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The multiplying effect of the active device is all that is required to provide the signal mixing action, thus so the local oscillator drive must also not drive the mixer into a non-linear region of the circuit transfer characteristics. In any event, the input signal source must not drive the input into a cut-off voltage level, or the pinch off voltage level, or the input signal would be distorted at the mixers or amplifiers output. Using higher voltages for the active circuit power supply, say 28volts, has been used in the pass for active circuit mixers. Similarly if the active circuit is driven into a non-linear function, the intermodulated products would be produced in greater quantities that would otherwise be perhaps the case with a diode ring. This in effected also goes to add to the intermodulated products and perhaps reduce the intercept points of the mixers performance.Īn active mixer of transistors, bi-polar, Jfet or even VMOS, has the added advantage of a linear region within the transfer characteristics of the mixer, where as a diode ring circuit is a mixer through brut force. Although the diode characteristics are also multiplying the signals, the switching effect does however produce harmonics of both the 2 nd and 3 rd harmonic levels. The diode ring uses the switching characteristics of the rectifier diode, that is to say the diode is driven to switch on and off by the high local oscillator drive signal input. Much has been said about diode ring mixers, but although these are simple to use, they do otherwise has a limited signal handling capability as does any mixer.