What Is Intermediate Frequency?

When dividing by frequency, MF (Medium Frequency) refers to the frequency from 300KHz to 3000KHz, most of which are AM radio stations. When divided according to its position and role in the circuit: IF intermediate frequency (Intermediate Frequency) refers to a signal obtained by frequency conversion of high-frequency signals.

Chinese name: IF

Foreign name: Medium Frequency / Intermediate Frequency

- IF IF-IF

IF has two meanings:

First, when dividing by frequency. MF (Medium Frequency) refers to the frequency from 300KHz to 3000KHz, most of which are AM radio stations. The propagation distance is short in the daytime, and it can be used for long-distance propagation because it can use the ionosphere to reflect signals at night. However, it is more susceptible to interference from other radio waves.

The pitch of most natural instruments falls in the mid-range. The most concentrated place for human vocal energy is 500-1000 Hz. The overtones of many natural instruments also fall mainly in the mid-band, such as guitars, and the overtones fall mainly at 2000-5000 Hz. The same is true for viola and cello. ^[1]

Second, when dividing according to its position and function in the circuit: IF Intermediate Frequency ^[2] refers to a signal obtained by frequency conversion of a high-frequency signal. In order to make the amplifier work stably and reduce interference, the general receiver must change the high frequency signal into the intermediate frequency signal.

The TV's image IF signal is 38MHZ.

The IF signal of the audio is 6.5MHZ.

The IF signal of the MW radio is 465KHz

The IF of the FM radio is 10.7MHZ

Radio frequency refers to the transmission frequency, because some signals may not be suitable for direct transmission (the frequency is illegal, or the conditions of the signal itself do not allow it). So to modulate the signal, the modulator itself needs a suitable oscillating signal, and the original signal is added on top. This oscillating signal is called a carrier, and the modulated carrier is included.

IF Zero IF Receive Technology

Schematic diagram of zero-IF reception technology Zero-IF reception technology, that is, the RF signal does not need to be converted to the IF, but is directly converted to the analog baseband I / Q signal at one time, and then demodulated. In recent years, software radio, as an emerging technology, has revolutionized the traditional radio technology field. Zero-IF has become very practical. GNU Radio is an open source software development tool suite. It provides signal operation and processing modules that can be used to implement software-defined radios on easy-to-manufacture, low-cost radio frequency (RF) hardware and general-purpose microprocessors. This kit is widely used by amateurs, academic institutions and commercial institutions to research and build wireless communication systems. GNU Radio applications are mainly written in the Python programming language. But its core signal processing module is C ++ built on a microprocessor with floating point arithmetic. Therefore, developers can simply and quickly build a real-time, high-capacity wireless communication system. Although its main function is not an emulator, GNU Radio supports the study of algorithms for signal processing of pre-stored and (signal generator) generated data without RF RF hardware components.

IF and IF induction heating

Induction heating is mostly used in industrial metal parts surface quenching, metal smelting, bar heat penetration and other fields. It is used to generate a certain induction current on the surface of the workpiece, quickly heat the surface of the part, and achieve rapid surface heating, or even heat penetration and melting.

IF working principle

The principle of induction heating: The workpiece is placed in the inductor. The inductor is generally a hollow copper tube that is fed with intermediate frequency or high frequency AC power (300-300000Hz or higher). The generation of an alternating magnetic field produces an induced current of the same frequency in the workpiece. This induced current is unevenly distributed on the workpiece, strong on the surface, but weak on the inside, and close to 0 to the heart. Use this skin effect , Can make the surface of the workpiece heat quickly, the surface temperature rises to 800-1000 & ordm; C within a few seconds, and the temperature of the heart rises very little.

The intermediate frequency furnace uses 200-2500Hz intermediate frequency power for induction heating and smelting insulation. It is mainly used for smelting carbon steel, alloy steel, special steel, and also for smelting and heating of non-ferrous metals such as copper and aluminum. The equipment is small in size and light in weight. High efficiency, low power consumption, fast melting and heating, easy control of furnace temperature and high production efficiency.

Working principle of intermediate frequency induction hot water stove

The power supply method is different from the power frequency electric boiler. The 380V power frequency AC power is input into the IF power cabinet (the IF power cabinet has overvoltage protection and overcurrent protection. If there is overvoltage or overcurrent, it will automatically stop and alarm). In the IF power cabinet, rectify the power frequency AC power to single-phase DC, and then convert it to single-phase AC IF voltage and current (the single-phase AC IF voltage and current are safe), and input the single-phase AC IF voltage and current. The heater generates induction electricity to inductively heat the water in the boiler. Therefore, the water and electricity are separated during the heating process of the boiler, which is safe and reliable. ^[3]