RF transformer is to achieve the main transformation, coupling and impedance matching of signals in the RF (Radio Frequency) circuit. The following are the main functions of RF transformer.

1. Transformation effect: RF transformers can be used to transform the voltage or current level of signals. By adjusting the ratio of turns on different windings of the transformer, the signal can be stepped up or down to adapt to different RF circuit requirements.

2. Coupling effect: RF transformers can be used to achieve signal coupling and transmission. It can transmit signals from one circuit to another, realizing energy transfer and information transfer between different circuits.

3. Impedance matching: RF transformers can be used to achieve impedance matching to ensure maximum power transfer of signals between circuits. By adjusting the transformer's turn ratio and winding design, impedance matching between the signal source and load can be achieved to minimize signal reflections and losses.

4. Filtering and frequency selection: RF transformers can be used to implement frequency selection and filtering functions. Through the specific design and parameter selection of the transformer, selective transmission and filtering of signals within a specific frequency range can be achieved to meet the frequency selection requirements of the radio frequency circuit.

In general, RF transformers play an important role in RF circuits and are mainly used for functions such as voltage transformation, coupling, impedance matching, and filtering. They are one of the key components for realizing radio frequency signal transmission, conversion and processing, and are widely used in radio frequency applications such as communication systems, radio equipment, broadcasting, radar, and antenna systems.