RF Frequency Converters Information
RF frequency converters are integrated component assemblies required for converting microwave signals into lower (or intermediate) or higher frequency ranges for further processing. They generally consist of an input filter, a local oscillator filter, an IF filter, a mixer, and frequently an LO frequency multiplier, plus one or more stages of IF amplification. RF frequency converters may also incorporate a local oscillator, GC/gain compensation components, and an RF preamplifier.
As a system, RF frequency converters function to alter incoming microwave signals into different frequency ranges to allow for a wide range of processing options that could follow. RF frequency converters are available in a number of configurations, defined by the type of frequency they output. Upconverters change microwave signals to a higher frequency range. Generally an upconverter is designed to produce an output signal frequency for a particular frequency band. By contrast, downconverters alter microwave signals in to an intermediate frequency (IF) range, again tuned to a particular frequency band. Some varieties of RF frequency converters are dual upconverters and downconverters, meaning that they can modulate the frequency either up or down, but again, only into a specific range on either side of the spectrum. A final type of converter is the variable converter, which can change the frequency of the input signal to any frequency within the operating range. They are not constrained to produce signals for a particular frequency band, as is the case with upconverters and downconverters.
RF frequency converters perform their waveform functions using either of two main technology types: synthesized or crystal controlled. Synthesized converters use a synthesizer circuit (normally a PLL) to produce the desired frequency, while crystal controlled devices converter use a crystal oscillator to produce the desired frequency. Generally crystal controlled converters are more accurate than synthesized converters.
When considering which of the available RF frequency converters would be best for the application at hand, there are a number of specifications to consider. Foremost among these is the style of form factor needed. These may be internal, in the form of IC chips or computer boards, or external devices that may be rack mounted, or stacked in a tower. Other important specifications include the input and output frequency ranges of the device, the associated conversion gain and return loss, noise figure, and power output.