Intermediate Frequency (IF) Calculator and Formula

This page provides an Intermediate Frequency (IF) calculator and explains the IF formula. It also defines Intermediate Frequency and describes its benefits.

What is Intermediate Frequency?

The term “Intermediate Frequency” (IF) is commonly used in electronic and communication engineering, especially in up-conversion and down-conversion stages within heterodyne architectures.

Essentially, it’s a frequency to which a carrier wave is shifted as an intermediate step during transmission and reception.

• The IF is generated by mixing two frequencies: an Input frequency (F_in1 or F_in2) and a Local Oscillator frequency (F_LO1 or F_LO2).
• F_in1 and F_LO1 are fed into an RF Mixer to generate F_IF1, which is the sum of these two frequencies during the up-conversion process (see Figure 2 below).
• F_in2 and F_LO2 are fed into an RF Mixer to generate F_IF2, which is the difference between these two frequencies during the down-conversion process.

The intermediate frequency concept is widely used in RF transceivers for various wireless systems. To better understand RF up-conversion and down-conversion, refer to resources on Upconverter vs. Downconverter and RF Transceiver design.

Typical intermediate frequencies are 455 kHz for AM receivers and 10.7 MHz for FM receivers.

Benefits of Using Intermediate Frequency

Here are some advantages of using an intermediate frequency:

• Signal processing is simpler at lower frequencies.
• Designing filters is easier at lower frequencies.
• Lower-frequency transistors tend to provide higher gain.
• The overall system cost is reduced due to the availability of less expensive components at lower frequencies.

Intermediate Frequency Calculator

Up-Converter

EXAMPLE #1:

• INPUTS: F_in1 = 70 MHz, F_LO1 = 1112.5 MHz
• OUTPUT: F_IF1 = 1182.5 MHz

Down-Converter

EXAMPLE #2:

• INPUTS: F_in2 = 3700 MHz, F_LO2 = 4680 MHz
• OUTPUT: F_IF2 = 980 MHz

Note: This down-conversion example uses a local oscillator frequency that’s higher than the RF (Radio Frequency).

Intermediate Frequency Formula

The following formulas are used in the Intermediate Frequency calculator: