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Radio frequency radio terminology knowledge

Source: unknown Editor: admin Time: 16:42, May 14, 2019

Radio frequency

Used to define a class of high-frequency electronic signals that will be radiated into radio waves. It is usually used to describe frequency ranges less than 1GHz.

 

Saturation

The behavior of all amplifiers when the input power exceeds a certain value. The amplifier is no longer amplified and the output is relatively constant. When the amplifier is in the saturation region, it is nonlinear and it will cause distortion of the RF signal.

 

Octave

Describes a bandwidth in which the upper side frequency is twice the lower side frequency.

 

Surface acoustic wave

An electrical signal converted into sound waves. In surface acoustic equipment, sound waves travel along the surface of the device rather than inside the device.

 

Wavelength

Measurement of RF signal length. The higher the signal frequency, the shorter the wavelength.

 

Waveguide

A tube with rectangular cross sections for transmitting RF signals from one point to another. Inside it, RF signals move in the form of waves, and waveguides are used to guide and control their movement.

 

Beamwidth

The width of RF energy radiated by antenna is described by circular angle. It is also used to measure the width of the antenna azimuth pattern

 

Insertion loss

The reduction of output signal of passive equipment relative to input signal, in decibels.

 

Constant attenuator (PAD)

Fixed attenuator, its insertion loss is constant.

 

Bandwidth

Measure the available frequency range of a device or application. It is equal to the difference between the up and down frequencies, expressed in Hertz or percentage.

 

Simplex

A radio frequency system that can only transmit in one direction at a time.

 

Monopole

A linear (omnidirectional) antenna with a quarter wavelength.

 

Capacitor

A small passive device used to form electrical signals.

 

Resistor

Small passive devices for reducing electronic signals.

 

Inductor

A small passive device for forming electrical signals is made of spiral coils.

 

Transmitter

One of the two main function blocks in wireless system. It takes the signal out of the modulator, increases the frequency and power of the signal, and then radiates it from the antenna.

 

Receiver

One of the two main function blocks of a wireless system is responsible for receiving RF energy from the antenna and reducing the signal frequency to a level acceptable to the demodulator.

 

T / R switch

Single pole, double throw switch, located between transmitter, receiver and antenna.

 

 

Reflection

It is used to describe the behavior of RF signal when encountering impedance mismatch or solid object. Due to the impedance mismatch, some (or all) of the RF energy is reflected back in the direction it goes. When encountering a solid object, RF energy is reflected back at the same angle as it encounters the object.

 

Amplifier

Active RF device for increasing RF signal power. There are three kinds of amplifiers: high power amplifier, low noise amplifier and other types of amplifiers (including gain variable amplifier and limiting amplifier).

 

 

Decibel

A mathematical transformation in which wallpaper is logarithmically converted, often the unit of measurement for RF signals. It is mainly used to describe the (power) gain and (insertion) loss of RF devices.

 

Dividers

A passive RF device that equally divides an RF signal into two or more RF signals.

 

Amplitude modulation

A form of modulation in which information is superimposed on an RF carrier by changing the amplitude of a continuous sinusoidal carrier.

 

Radiation

Used to describe the process of radio frequency signal becoming radio wave.

 

Interference

It is not the influence of the signal the receiver wants to receive on the receiver side.

 

Power density

A measure of radio frequency energy in the air passing through an area in watts per square meter.

 

Broadcasting

An RF system that uses a single transmitter and multiple geographically dispersed receivers to communicate.

 

Baseband

The lowest frequency signal in the transmitter or receiver. It is the modulated RF signal after the complete down conversion in the receiver or the modulated RF signal before the up conversion in the transmitter.

 

Polarization

When the RF sine wave propagates in the air, it has spatial orientation. There are three types of polarization: horizontal, vertical and circular.

 

Demodulation

The process of separating RF carriers from information signals in modulated signals.

 

Demodulator

An RF device used to demodulate. This kind of equipment is very complex, including active and passive equipment, the main components are mixer.

 

Spread spectrum

A digital modulation scheme that increases the carrying capacity of a signal over a given bandwidth. It is realized by allowing multiple signals to occupy the same frequency and using a unique "address" to distinguish signals.

 

Broadband

Describes the characteristics of RF devices or wireless applications with "wide" bandwidth. Any bandwidth over 50% is considered broadband.

 

Narrowband

Used to describe the characteristics of RF devices or wireless applications with very narrow bandwidth. Generally, any bandwidth less than 50% is considered as narrow band.

 

Filter

There are four types of passive RF devices, which can make a certain frequency signal pass or obstruct, including band-pass filter, high pass filter, low-pass filter and band stop filter.

 

Code division multiple access

An air interface technology that increases the signal capacity for a given bandwidth. At a given bandwidth, it allows many signals to occupy the same frequency at the same time and assigns a unique "address" to each receiver. It is also used to describe direct sequence extensions.

 

Chips

It is used to expand the spread spectrum signal directly.

 

Chip rate

Chip frequency used in direct sequence spread spectrum.

 

Frequency division multiple access

An air interface that divides a given frequency band into smaller frequencies to increase system capacity.

 

Frequency division multiplexing

In order to transmit multiple signals, a frequency range is divided into many small frequency ranges.

 

Frequency division duplex

A frequency range is divided into two different frequency ranges, which is suitable for duplex communication. One frequency range realizes information transmission in one direction.

 

Spectrum analyzer

A tool used by RF engineers to observe RF energy over a certain frequency range. The horizontal axis of the coordinate system is the unit of frequency and the vertical axis is the unit of power.

 

Skin effect

A description of the behavior of radio frequency signals as they propagate over a wire. Because of their high frequency, the RF signal does not penetrate the solid conductor, but exists on the external surface.

 

Time division multiple access

A type of air interface, which describes the technology of increasing signal carrying capacity by dividing each frequency into multiple time slots and allocating a special time slot for each signal.

 

Time division multiplexing

A single communication channel is divided into multiple time slots to provide two-way communication. The variable connection time slot is used to change the direction.

 

Attenuation

Describes the value of RF signal energy reduction from one point to another. It can be replaced by the term insertion loss in decibels.

 

Attenuator

An RF device that reduces the RF signal energy by a predetermined value in decibels. There are fixed and variable attenuators. Variable attenuators include voltage variable attenuator and digital attenuator.

 

Transceiver

Combination of transmitter and receiver in separate package.

 

Duplex

RF system that can send and receive at the same time.

 

Duplexer

Passive RF equipment, which contains two different bandpass filters.

 

Bi directional

It is used to describe that any RF device can work properly in both directions. Also known as dual direction, most antennas are bi-directional, but amplifiers are definitely not bi-directional.

 

Phase locked loop

An ideal wave will come in to include a sinusoidal oscillator. A PLL can be used as part of a complex oscillator (Synthesizer).

 

Antenna

An RF device used to convert an RF signal transmitted over a wire into a wave propagating in the air, or a wave propagating in the air into an RF signal transmitted over a wire. The size of the active antenna must be the same as that of the active device, and it must be the same as that of the active device.

 

Modulation

The information signal is superimposed on the RF carrier by changing some parameters of the carrier. There are amplitude modulation and phase modulation. Phase modulation includes frequency modulation.

 

Modulator

A device that superimposes information signals onto an RF carrier. It has two inputs (carrier and information signal) and one output (modulated signal).

 

Frequency hopping spread spectrum

A spread spectrum technique in which the RF carrier frequency is continuously changed so that only the target receiver can identify it.

 

Passband

The frequency range of the band-pass filter. The bandpass filter has low insertion loss and allows the signal to pass through. The passband is defined by determining its upper and lower sidebands.

 

Carrier

RF signals (ideally perfect sinusoidal signals) carry information through modulation and travel through the air.

 

Gain

Through the amplifier, the increase degree of the output signal relative to the input signal, in decibels.

 

Direct sequence spread spectrum

A form of spread spectrum in which pseudo-random codes are used to extend the frequency of a signal.

 

Impedance

Measure the "size" of RF device input and output in Ω. In RF systems, the standard "size" of all devices is 50 Ω.

 

Impedance matching

The operation of converting the output resistance of RF equipment to realize the effective connection between one device and other devices.