The Elements of RF Downcoverter Design

As computers become more and more prevalent in our daily lives, being able to record an analog signal, be it someone’s voice or through a telegraph, and convert it into a digital format to be edited, manipulated, and stored. In the world of digital signal processing, advanced technologies are needed to manipulate signals and change them from analog to digital. An RF downconverter is one such technology that allows a processor to convert digital signals.

To the uninitiated, digital signal processing can be extremely confusing. To put it in its most basic terms, a signal is simply a function that conveys some information. This can include audio or video, images, speech, text, geophysical coordinates, sonar and radar waves, and even musical tones. These different ‘signals’ often come in pairs or groups.

When this happens, a mixer is used to manipulate and convert those signals. In mixing any two input signals, the possibilities for output are the sum of the signals, the difference of the signals, and the two separate signals themselves. Typically the difference of the two signals, also known as the base banded signal, is the most useful in terms of transmission. A DDC or digital down converter is the device used to shift the two input signals into a zero frequency difference signal.

It is important to remember that all signals, even video signals, travel in waves similar to those you may have learned about in your high school trigonometry class. Remember sine and cosine? When two signals have different frequencies, it takes a large amount of bandwidth in order to transmit and receive both of the waves of each signal.

Rather than transmitting two separate signal waves, a down converter finds a pattern where these two waves meet up on a fixed interval. The points on this interval where the waves meet are known as sampling points. These sampling points are then used to create a completely new wave that describes their pattern. This new signal is the down converted difference signal that is much easier to transmit and requires far less bandwidth and power.

For instance, you may want to send a video message to your friend. This includes a signal for the audio, and a signal for the video, both with very different frequencies. A down converter takes these two signals, finds their difference pattern using an advanced calculus formula, and stream lines the two signals into a new, more efficient signal. An RF converter makes sure that these two signals are converted so they can be transmitted with maximum efficiency, speed, and fidelity.

While it may sound complicated, in truth, an RF type converter is actually a very simple circuit that can be built at home with minimal electronic knowledge or soldering experience. In fact, the device requires only three components that can be bought off the shelf at most electronics and parts stores. Converters are comprised of a coaxial mixer, a low noise amplifier and a power regulator.

To find out more about what a RF downconverter can do or to buy one for your own home project, go to aventasinc.com today!

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For a more technical discussion on RF designs, we recommend these books from Amazon:
RF Circuit Design, Second Edition

An Introduction To RF Circuit Design For Communication Systems

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