2. Resources
  3. RF design guide
  4. Radio transmission terminology

RF Technical Resources

  • RF design guide
  • Modem evaluation
  • Calculation tools
  • Radio technology
  • Technical literature
  • Modem evaluation
Telecontrol Telecontrol means "remote control". This involves the use of radio waves for radio control of devices or machinery at a remote location. This is used principally for remote control of cranes, concrete pumping machinery, and the industrial equipment used for engineering work, construction, forestry and the like.
Telemetry Telemetry is the transmission of remote measurement data, and this involves the transmission of measurement results from a measuring device or the like at a remote location using radio waves. In general with telemetry a host sends an enquiry to equipment that has a measuring sensor (water level, temperature, humidity, voltage, current, rate of flow and so on) asking if it has data to transmit, and if there is data, it receives it, often gathering information from several devices.
Preamble In order to establish synchronization of the frames required for the transmission of data between transmitter and receiver, this signal is added to the front of the frame, and may consist of a bit stream of alternately repeated 0s and 1s.
Receive sensitivity The unit for receive sensitivity is dBm, and it is expressed as 0 dBm of relative power when received power is 1 mW. It is also sometimes shown as a voltage uV. The method of stipulating receive sensitivity varies according to the manufacturer, and may be stipulated as SINAD or error rate or the like.
Spurious emissions These are unwanted emissions that fall outside the radio wave of interest. If there are many spurious emissions, they will have adverse effects on other communications.
Deviation This is the degree of frequency shift in the frequency modulation system.
RSSI (Received Signal Strength Indicator) Used with carrier sensing, this signal indicates the intensity of the received signal. It is output by the receiving equipment.
VCO An oscillator that can change an oscillating frequency using a signal voltage added to the input. It is used with FM modulation and FSK modulation.
Carrier A signal that is suited to the transmission path whose parameters are manipulated in order to convey the information of the base band data.
Carrier sensing This denotes the checking of a channel to see if it is free before transmitting equipment transmits radio waves. If the checked channel is being used, the equipment switches channels, and if the channel is free, it begins emitting radio waves.
Base band data Information that has been changed into an electric signal.
Base band transmission system A system for transmitting information that has been changed into an electric signal.
Carrier transmission system This is a system by which the carrier is modulated by the base band signal, and transmits on the frequency band of the carrier frequency.
Modulation The parameters of a carrier that is suited to the transmission path is shifted proportionally by the base band signal. In radio transmissions, this denotes the manipulation by shifting of a base band waveband to a high frequency waveband.
BER (Bit Error Rate) BER = Number of error bits / Number of transmitted bits
S/N (Signal to Noise Ratio) The voltage ratio for the output level (noise) when nothing is input in an amplifier or the like, and the output level when a reference signal is input can be found with the following equation. S/N = 20 log 10 (signal voltage / noise voltage) It is necessary to consider the following 2 points as reasons for why S/N can become a problem with radio equipment. 1) The receiving antenna receives RF noise from space. 2) There is noise generated by components of the receiver circuit themselves.
C/N (Carrier to Noise Ratio) The ratio of the power of the carrier to the power of noise output.
Noise figure The components used in amplifiers necessarily generate noise, and amplifying a signal decreases S/N. Noise figure denotes the ratio of the input SN rate and the output SN rate, and if this value is smaller, better amplifier performance is indicated.
SINAD (Signal + Noise + Distortion to Noise + Distortion Ratio) This refers to the method of taking the ratio of the demodulated output level of the received signal level when modulation is applied, and of the aggregate level of noise and distortion of the demodulated output with only the signal component removed. A ratio of 12 dB for the received signal level may be taken as a reference for sensitivity.
ISM band (Industrial, Scientific, and Medical band) This is a waveband reserved for the industrial, scientific and medical sectors, and is used in every country. Specifically, the 2.4 GHz band is common to all countries, and the devices using wireless LAN, Bluetooth, Home RF and so on are in competition with this band. This equipment uses the spread spectrum communication system required for wide band.
Japan 2.4 GHz band
North America 0.9 GHz, 2.4 GHz, 5.7 GHz bands
Europe, Hong Kong, Singapore, Australia 2.4 GHz, 5.7 GHz band
Spread Spectrum Communication The communication method used for wireless LAN and Bluetooth. There are two types, direct sequence spread spectrum (DSSS) used by wireless LAN, and frequency hopping spread spectrum used by Bluetooth. By spreading the signal spectrum over a wide band, multi-access, good resistance to noise, and good security can be achieved.
Burst error Consecutive data errors that occur suddenly. If errors spanning several bytes occur, complete decoding at the receiving end is not possible even if error correction is applied. As a measure against burst errors, methods such as interleaving are used.
FEC (Forward Error Correction) In order to carry out error correction at the receiving equipment end, the transmitting equipment includes an error correction function in the sent data. Reed-Solomon code, trellis code and the like are used, and although they increase the data amount, they allow more reliable transmission.
Interleaving A technique for handling burst errors in the transmission path. In order to prevent the loss of data through burst errors, with this method data streams containing error correction functions are dispersed, so that even if burst errors occur, the error correction function can be used effectively for decoding at the receiving equipment end. The operation performed at the receiving end to return the signal to its original state is called deinterleaving.


back to the TOP of this page