Electronic mixer

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An electronic mixer is a device that combines two or more electrical or electronic signals into one or two composite output signals. There are two basic circuits that both use the term mixer, but they are very different types of circuits: mixer additives and multiplicative mixers.

Simple additive mixer uses Kirchhoff circuit law to add two or more signals together, and this terminology ("mixer") is only used in the field of audio electronics where audio mixers are used to add shared audio signals such as sound signals, musical signals, and sound effects.

Multiplicative mixers multiply together two input signals that vary instantly (instant-by-instant). If two input signals are both sinusoids of the specified frequency f ₁ and f ₂ , then the output of the mixer will contain two new sinsoids which have the number f ₁ f ₂ frequency and difference in absolute value of frequency | f ₁ - f ₂ |.

Note: Nonlinear electronic blocks powered by two signals with frequency f ₁ and f ₂ will produce intermodulation products. Multipliers (which are nonlinear devices) will generate ideally only the number and frequency difference, whereas random nonlinear blocks will produce also signals in eg. 2Ã, Â · f ₁ -3Ã, Â · f ₂ , etc. Therefore, a normal nonlinear amplifier or a single diode has been used as a mixer, not a more complex multiplier. Multipliers typically have rejection advantages - at least in part - undesirable high order intermodulations and larger conversion improvements.

Video Electronic mixer

Aditif mixer

Additive additives add two or more signals, providing a composite signal containing the frequency components of each source signal. The simplest additive mixer is a simple resistor network, and thus purely passive, while a more complex matrix mixer uses active components such as amplifier amplifiers for better impedance and isolation matching.

Maps Electronic mixer

Multiplicator multiplier

The ideal multiplicative mixer produces the same output signal as the product of two input signals. Multiplicative mixer is often used in conjunction with an oscillator in the communication field to modulate the signal frequency. Multiplicative multipliers can be combined with filters to up-convert or down-convert input signal frequencies, but they are more commonly used to down-convert to lower frequencies to allow for simpler filter design, as done on superheterodyne receivers. In many typical circuits, a single output signal actually contains several waveforms, that is, on the number and the difference of the two input frequencies and the harmonic waveform. The output signal can be obtained by removing the other signal components with the filter. ( see intermediate frequency)

Mathematical care

Sinyal yang diterima dapat direpresentasikan sebagai

${\ displaystyle E _ {\ mathrm {sig}} \ cos (\ omega _ {\ mathrm {sig}} t \ varphi) \,}  ÂÂ$

dan osilator lokal dapat diwakili sebagai

${\ displaystyle E _ {\ mathrm {LO}} \ cos (\ omega _ {\ mathrm {LO}} t). \,}  ÂÂ$

Output memiliki frekuensi tinggi ( ${\ displaystyle 2 \ omega _ {\ mathrm {sig}}}  ÂÂ$ , ${\ displaystyle 2 \ omega _ {\ mathrm {LO}}}  ÂÂ$ dan ${\ displaystyle \ omega _ {\ mathrm {sig}} \ omega _ {\ mathrm {LO}}}  ÂÂ$ ) dan komponen konstan. Dalam deteksi heterodyne, komponen frekuensi tinggi dan biasanya komponen konstan disaring, meninggalkan frekuensi antara (beat) pada ${\ displaystyle \ omega _ {\ mathrm {sig}} - \ omega _ {\ mathrm {LO}}}  ÂÂ$ . Amplitudo komponen terakhir ini sebanding dengan amplitudo dari radiasi sinyal. Dengan analisis sinyal yang tepat, fase sinyal dapat dipulihkan juga.

Jika ${\ displaystyle \ omega _ {\ mathrm {LO}}}  ÂÂ$ sama dengan ${\ displaystyle \ omega _ {\ mathrm {sig}}}  ÂÂ$ maka komponen ketukan adalah versi pemulihan dari sinyal asli, dengan amplitudo yang sama dengan produk ${\ displaystyle E _ {\ mathrm {sig}}}  ÂÂ$ dan ${\ displaystyle E _ {\ mathrm {LO}}}  ÂÂ$ ; yaitu, sinyal yang diterima diperkuat dengan mencampur dengan osilator lokal. Ini adalah dasar untuk penerima konversi langsung.

Implementations

Multiplicative mixers have been implemented in various ways. The most popular are Gilbert mixers, diode mixers, diode ring mixers (ring modulation) and switching mixers. The diode mixer utilizes the non-linearity of the diode device to produce the desired multiplication in quadratic terms. This is a very inefficient method because most of the power output is in other undesirable things that need to be filtered. The cheap AM radio still uses a diode mixer.

Electronic mixers are usually made with transistors and/or diodes arranged in balanced circuits or even dual circuits. This is easily made using either monolithic integrated circuit technology or hybrid integrated circuits. It's designed for a wide range of frequencies, and mass-produced for tight tolerance of up to hundreds of thousands, making it a relatively inexpensive component.

This double-balanced mixer is widely used in microwave communications systems, satellite communications systems, and ultrasonic frequency communications and transmitter and receiver (UHF), and in radar system transmitters and receivers.

Gilbert cell mixer is just a transistor arrangement that multiplies two signals. The switching mixer (below) skips more power and typically inserts less distortion.

switching mixer uses field effect field transistors or (in older times) vacuum tubes. It's used as an electronic switch, to allow signals to go in one direction, then another. They are controlled by the signal being mixed. They are very popular with digitally controlled radios.

Source of the article : Wikipedia