Brief glossary of technical terms. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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AGC

- Automatic Gain Control - a type of negative feedback that reduces the gain of the amplifier with a strong input signal and increases with a weak one. AGC usually consists of an amplitude detector и filter low frequencies. Thus, at its output there is an average output voltage, which usually drives a transistor that shunts the input circuit.

Harmonics

- frequency components of complex periodic oscillations, an integer number of times greater than the fundamental frequency of these oscillations. The harmonic number is given by the ratio of its frequency to the frequency of the main signal. That is, the second harmonic has a frequency twice the fundamental, the third - three times, etc. As the harmonic number increases, its amplitude decreases. Subharmonics - frequency components, an integer number of times smaller than the fundamental frequency, appear in the spectrum much less frequently.

Datasheet

- technical documentation file in *.pdf format, readable with Adobe Acrobat Reader

Deviation

- value showing the maximum deviation of the carrier frequency in the positive / negative direction during frequency modulation. For example, the carrier has a frequency of 74,250 MHz and the deviation is 75 kHz, i.e. 0,075 MHz. This means that the carrier can vary within 74,175 ... 74,325 MHz

Detector

(in electronics) - a device that allows you to select a modulating signal from a received modulated carrier, see. modulation. Depending on the type of modulation, there are amplitude, frequency, phase, etc. detectors.

Wavelength

- in the general case - the distance in meters between two identical points of oscillation of two adjacent periods. To put it simply - the distance between the "scallops" (maximums) of two adjacent waves (on the water). The same applies to all other types of waves that are on Earth and in its vicinity. The wavelength depends on the repetition rate of waves and on the speed of wave propagation in a given medium. The higher the frequency and the lower the propagation speed, the shorter the wave. For radio waves, the propagation speed is equal to the speed of light, C = 300 m/s. The formula is:

where is the wavelength in m, C is the speed of light in m/s, f is the oscillation frequency in Hz. For convenience, it is better to use another formula:

In this case, the wavelength will turn out, again, in meters.

Converter

- in the general case - the converter. In radio engineering - a device that allows you to receive a signal of one frequency range to a receiver with a different frequency range. For example, HF - range on the receiver DV (AM) - range. In digital technology - a device that converts a digital code from one encoding to another. For example, a binary code converter to a seven-segment indicator code.

Location

- determination of the location of the object by the signal emitted by it, or by the signal reflected from it. Depending on the type of signals, l. there is sound, optical, radar, etc.

microcontroller

- this is a single-crystal semiconductor IC, as a rule, having a processor, program memory (ROM), random access memory (RAM), input / output interface and other peripheral blocks (timers, analog comparators, etc.) inside. The microcontroller executes a program that is stored in ROM. Modern advanced microcontrollers have ROM "on board". The program for m / c is usually written on a computer, after which it is “filled” into ROM through a special device, for example, Byte Blaster, connected to the LPT port (printer port).

Modulation

(in radio engineering) - a change in any parameter of periodic high-frequency oscillations under the influence of a low-frequency signal. It happens amplitude (AM), frequency (FM, in bourgeois - FM), phase (FM, not to be confused with FM), pulse-width (PWM).

Amplitude modulation

- m., at which the amplitude of the modulated (HF) signal depends on the amplitude of the modulating (LF) signal.

Frequency modulation

- m., at which the frequency of the modulated signal depends on the amplitude of the modulating signal.

Pulse width modulation (PWM)

- m., at which the pulse width of the modulated signal depends on the amplitude of the modulating signal, while the frequency of the modulated signal remains constant.

Periodic fluctuations

- fluctuations that occur with a certain periodicity. Such oscillations are characterized by the following parameters: frequency f, period T. Depending on the shape, oscillations can be simple, harmonic - i.e. sinusoidal or complex those., inharmonious, consisting of pulses of a rectangular, triangular, sawtooth shape, etc. Complex oscillations are mathematically decomposed into the sum of harmonic oscillations of multiple frequencies, which are called the harmonics of a given signal.

Filter

- a device that allows you to select frequencies of a certain range from the spectrum by passing the frequencies of the desired range and suppressing all others.

Low pass filter (LPF)

- skips low frequencies (from 0 to calculated)

High Pass Filter (HPF)

- skips high frequencies (from calculated to infinity)

Band pass filter

- passes a frequency band limited to certain frequencies

Notch (trap) filter

- passes all frequencies, except for a band limited by certain frequencies

Sensitivity