There are three, and on many frequency mixer modules, they are labelled as such.: This method is preferred because creates fewer spurious signals and hence it provides higher linearity for the required output signals.įrequency mixers of RF mixers come in a variety of formats, but they all have the same basic connections.
The instantaneous output level is dependent upon the instantaneous level of signal A multiplied by the instantaneous level of signal B. The two signals can be considered as sine waves. This may be a diode, or active devices such as transistors or FETs that are suitably biased. As mentioned before the two signals are actually multiplied together, and this occurs as a result of a non-linear element in the circuit. To understand a little more about the RF mixing or multiplication process it is necessary to look at exactly how the mixing process occurs. Mixing two RF signals Why RF mixing or multiplication works To give an example if the two original signals are at frequencies of 1 MHz and 0.75 MHz, then the two resultant signals will appear at 1.75 MHz and 0.25 MHz. In other words if signals at frequencies of f1 and f2 enter the mixer, then additional signals at frequencies of (f1+f2) and (f1-f2) will also be seen at the output. These appear at frequencies equal to the sum and difference frequencies of the original signals. It is found that if two signals are passed through a non-linear circuit, then additional signals on new frequencies are formed. It enables signals to be changed from one frequency to another so that signal processing for example can be undertaken on a low frequency where it is easier to perform, but the signal can be changed to a from a higher frequency where the signal is to be transmitted or received. The process of RF or non-linear mixing or multiplication is used in virtually every radio set these days and also in many other circuits beside. Here signals are multiplied together and signals an new frequencies are generated.
Unlike an audio mixer where signals are simply added together, when a radio or RF engineer talks about mixing, he means a whole different process. One of the most useful RF or radio frequency processes is that of mixing. RF mixing basics Theory & math Specs & data Transistor mixer FET mixer Double balanced mixer Gilbert cell mixer Image reject mixer
RF Mixing / Multiplication: Frequency Mixers RF mixers or frequency mixers and the process of RF mixing or multiplication is key to many RF circuit enabling signal to be converted from one frequency to another as well as providing phase comparison.