| MIXING
Mixing is a wireless term that is used to refer to mixing two
different frequency signals together - in
order to obtain a third different frequency - and perhaps even more
frequency products. Mixing can sometimes be helpful - if it is
used to manufacture a third signal that a wireless product needs.
However, mixing can also be unintentional and can as such be called Intermodulation
or interference and potentially be
harmful to wireless products.
The Intermodulation reference may
also be helpful in understanding mixing - particularly for the unwanted
signals.
| For desired mixing, let us consider that a wireless device needs to
obtain a signal at 470 Mhz. Let us also suppose
that the wireless device does not have that frequency directly
available, but that it does have a 450 MHz signal and a 20 MHz
signal available. To obtain 470 MHz then, the wireless
device may decide to mix together the 450 MHz and 20 MHz signals
using a device such as a transistor to obtain linear and
non-linear mixing.
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Shows a good example of mixing - modulating in order to transmit
long distances using a high frequency carrier (FM
example) |
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What will be
the output will be not only the two original signals of 450 MHz and 20
MHz, but also more products - mostly of their sums and difference.
Those new products would be (among others) 470 MHz (which is 450 + 20),
430 Mhz (which is 450-20), and a number of others including 920 MHz (2
times 450 and then + 20) for example.
Wireless :"mixers" that create all of these products usually follow
these circuits with something called an electronic filter - that will
only allow the desired frequency of 470 MHz to pass through it.
Hence, "mixing" and a "mixer" was used to create a new frequency needed
for the product in this 470 MHz example.
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