What Is a Down Converter?
A down converter is a device that converts a higher frequency signal to a lower frequency.
For example, microwaves can be converted to millimeter waves so that conventional millimeter wave measurement equipment can be used. Or, a down converter is also used to convert high-resolution video to low-resolution video.
A down converter can be used to display a 4K-resolution broadcast on a conventional terrestrial digital broadcasting receiver.
Uses of Down Converters
Down converters are used extensively in many technical fields.
1. Satellite Communications
Down converters are most commonly used in satellite communications. Satellite signals are transmitted at very high frequencies and cannot be handled by many devices without modification.
Down converters convert these high-frequency signals to lower-frequency signals that are easier to handle.
2. Television and Radio Broadcasting
Down converters also play an important role in television and radio broadcasting. Signals sent by broadcasters are typically transmitted at high frequencies and converted through down converters to lower frequencies so that they become video or audio on the viewer’s or listener’s device.
3. Mobile Communications
Down converters are also essential in mobile communications. The radio waves used in cell phones are high frequency and must be converted to a lower frequency so that they can be understood by cell phones. This enables mobile communication services such as voice calls, text messages, and Internet access.
4. Radar and Radio Positioning Systems
In radar and radio positioning systems, down converters convert the transmitted high-frequency signal into a low-frequency signal that can be analyzed. This enables accurate acquisition of a variety of data, including aircraft position, speed, and weather information.
5. Compatibility Between New and Previous Generations
Down converters enable the continued use of conventional monitors that become unusable due to high resolution when TV sets are changed from analog to digital broadcasting.
As described above, down converters play an essential role in signal processing in all situations, from daily life to professional industries.
Principles of Down Converters
A down converter is basically an electronic device, also called a “mixer” or “mixer,” that converts high-frequency signals to lower frequencies that are easier to handle.
1. Role of the Mixer
The mixer is the central part of a down converter and receives two input signals. One is the received signal (high frequency) and the other is the signal from the local oscillator (LO).
The local oscillator is designed to oscillate at a constant frequency, and this oscillation is “mixed” with the received signal in the mixer to produce a signal at a new frequency.
2. Signal Conversion
When mixed in the mixer, a “difference” is created between the original high-frequency signal and the signal from the local oscillator. Specifically, the frequencies of the two signals cancel each other to produce a new signal.
This new signal, called the “difference frequency” or “intermediate frequency: IF,” is much lower in frequency than the original high frequency.
3. Signal Filtering
The signal converted to the intermediate frequency (IF) is then sent to a filter. This filter removes unwanted components and noise from the newly generated signal, leaving only the necessary information.
This allows the new signal to retain the original information, but in a more manageable and stable form. Thus, the role of a down converter is to convert a high-frequency signal into an easy-to-handle form and process the signal efficiently while maintaining the information.
Types of Down Converters
The types of down converters are as follows
1. RF Down Converter
The RF down converter is the most common type and converts high-frequency RF signals to low-frequency signals. It is widely used in telecommunications, broadcasting, and radar systems.
Its function is basically to convert a high-frequency signal into an intermediate frequency that is easier to handle and can be handled by subsequent signal processing systems.
2. Block Down Converter
Block downconverters are primarily used in satellite communication systems. They convert very high frequency signals sent from satellites to more manageable frequencies.
Block downconverters are usually mounted near parabolic antennas and are responsible for frequency conversion in the initial stage of the downlink signal.
3. Downscan Converter
A downscan converter is a device that converts a high-resolution video signal to a lower-resolution video signal.