IF Channel Sampling

An IF channel sampling system sweeps the RF downconverter local oscillator frequency from and samples spectrum at the IF output.

Simplified setup for IF channel sampling mode

FBS setup

Such systems are slower than the bandpass sampling systems, but have wider spectrum range and are much more flexible. Scanning spectrum range limits depend on the RF downconverter capabilities. Scanning speed strongly depends on the IF channel bandwidth and frequency range of interest.

Usage

Radiospectroscopy, radio monitoring, communication control, illegal transmissions and eavesdropping equipment detection.

Devices

A common receiver might be used as an RF downconverter, having 10.7 MHz IF channel and IF bandwidth up to 8 MHz. With such receiver it is possible to implement a quite fast system for frequency ranges up to 300 MHz. For wider ranges scanning speed decreases. To keep the scanning speed high, custom designed RF downconverters with wide intermediate channels should be used.

A digitzer could be selected according to the IF channel bandwidth. For a 10.7 MHz IF channel an ordinary digital 40 MHz oscilloscope can be employed.

The digitizer vertical resolution should be selected with respect to RF downconverter dynamic range. In general receivers have spurious and image rejection ratio up to 50..60 dB. A digitizer with ENOB higher than 11.0 might be a good choice. For example - ADQ114 from SP Devices is suitable candidate for such implementation.

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