Common RF Terms
3 dB rule: A 3 dB gain means twice (x2) the power. A 3 dB loss means half the power. For example, a system with 40 watts of input power and a 6 dB insertion loss will only have 10 watts of output power.
dB: Decibel, a logarithm (equal to 10 times) ratio of the difference between two values. The Site Master uses dB to measure the ratio of sent signal energy to reflected signal energy.
Common values of dB to ratios: 0 dB = 1:1, 10dB = 10:1, 20 dB = 100:1, 30 dB = 1,000:1, -30 dB = 0.001:1. or (1/1000):1.
dBm: An absolute measurement of power relative to 1 milliwatt.
0 dBm = 1.0 milliwatt, 10 dBm = 10 milliwatt, 30 dBm = (1 mW x 1,000) = 1 watt.
DTF (Distance to Fault): Measures the location and reflection size of impedance mismatches. This is typically a diagnostic measurement, not a pass/fail judgment measurement. DTF is used to identify and locate faults within an antenna system when the system is failing to meet the specified return loss/VSWR limits. DTF is also useful to verify the total length of a coaxial cable assembly.
Impedance: A measure of an RF components electrical resistance. Measured in ohms (Ω). In most cable and antenna systems the standard impedance is 50 Ω.
Insertion Loss (Cable Loss): Measures the total amount of signal energy absorbed (lost) by the cable assembly. Measured in dB. S21 is another name for this measurement. This is often a pass/fail measurement.
Return Loss: Measurement in dB of reflected energy caused by impedance mismatch. May also be referred to as S11. S11 values are expressed as negative numbers, but Return Loss values are expressed as positive numbers since by definition the “Loss” expression implies a negative sign. The higher the value, the better the impedance match (think of a large negative number being less than a smaller negative number). 40 dB is nearly ideal. Only 0.01% of the total transmitted power is reflected if the Return Loss measurement value is 40 dB. 0 dB would be a complete reflection, or stated another way, 100% of the transmitted power is reflected back. Return Loss is typically a pass/fail measurement.
RF (Radio Frequency): Frequency of radio sine waves. RF range is 3 kHz to 300 GHz.
VSWR (Voltage Standing Wave Ratio): Another method to measure reflected energy caused by impedance mismatch. Expressed as a ratio of X:1. VSWR measures the voltage peaks and valleys. 1:1 would be a perfect match. Atypical cable and antenna system would be around 1.43:1 or 15 dB Return Loss. The Site Master can measure either Return Loss or VSWR. Some carriers require that Return Loss is measured in VSWR. This is typically a pass/fail measurement.
Watt: Unit of measure for power.
FAQs
Basic Principles of Operations
- RF Transmission: An RF signal is created by upshifting a low bandwidth (DC-like) signal to radio frequency by a radio transmitter.
- RF reception: An RF signal is picked up by the antenna and downshifted to a low bandwidth (DC-like) signal by a radio receiver.
Cordless and cellphones, radio and television broadcast stations, Wi-Fi and Bluetooth, satellite communications systems and two-way radios all operate in the RF spectrum. In addition, other appliances outside of communications, including microwave ovens and garage door openers, operate at radio frequencies.
What does dB mean in RF? ›
This article discusses the basic unit of measurement used in radio signals: the decibel or dB. It is named after Alexander Graham Bell - that is why the “B” is capitalized. There are several variations of the dB used in radio.
How many types of RF are there? ›
RF frequency bands
| Band name | Abbreviation | Frequency |
|---|
| Medium frequency | MF | 300–3,000 kHz |
| High frequency | HF | 3–30 MHz |
| Very high frequency | VHF | 30–300 MHz |
| Ultra high frequency | UHF | 300–3,000 MHz |
8 more rowsBasically RF transistors are characterized by two types of parameters: DC and functional. The “DC” specs consist (by definition) of breakdown voltages, leakage currents, hFE (DC beta) and capacitances, while the functional specs cover gain, ruggedness, noise figure, Zin and Zout, S–parameters, distortion, etc.
How to start learning RF? ›
- Start with a bachelor's degree in electrical engineering or a related field. This forms the cornerstone of your RF engineering career.
- Consider enrolling in courses that specialize in RF fundamentals, transmission theory, and microwave engineering.
A simple technique is to look at the total width of the signal and find the mid-point in the signal. In general this will indicate the operating frequency. With this first piece of information we can now research frequency assignment tables to determine what type of radio service may be assigned to specific frequency.
Is RF analog or digital? ›
An RF circuit is a special type of analog circuit operating at the very high frequencies suitable for wireless transmission. One salient feature of an RF circuit is the use of inductive elements to tune the resonant circuit operation around a specific radio carrier frequency.
Is 5G an RF signal? ›
Like in previous mobile networks, 5G devices will communicate with base stations by transmitting and receiving radio waves, or radio frequency (RF) electromagnetic fields (EMF).
What is the 3 dB rule? ›
3 dB rule: A 3 dB gain means twice (x2) the power. A 3 dB loss means half the power. For example, a system with 40 watts of input power and a 6 dB insertion loss will only have 10 watts of output power. dB: Decibel, a logarithm (equal to 10 times) ratio of the difference between two values.
This question is asking you to recall the 3 db rule of sound intensity, which is this: If you increase the intensity of a sound by 3db it will double the audible noise, and if you reduce it by 3db it will halve the amount of audible noise.
What is a good signal strength for RF? ›
RF signal strength and wireless clients
Generally wireless client needs to be perceived at least −60 dBm or better in order to ensure the data rate of 11 Mbps and above. In fact, required signal strength varies with the modulation and channel bandwith.
What is the acronym RF? ›
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz.
What frequencies are RF? ›
The Very Basics. Radio frequency (RF) is a rate of oscillation in the range of around 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals.
What are RF types? ›
The Many Types of Radio Frequency Modulation. Amplitude Modulation in RF: Theory, Time Domain, Frequency Domain. Frequency Modulation: Theory, Time Domain, Frequency Domain. Phase Modulation: Theory, Time Domain, Frequency Domain. Digital Modulation: Amplitude and Frequency.
What is RF and how does it work? ›
RF is generated by a transmitter and detected by a receiver. The transmitter antenna turns electrical signals into radio waves, giving it the ability to travel long distances. The receiver antenna catches the radio waves and turns them back into electrical signals, which feed into a radio, television, telephone, etc.
What is RF technology and how it works? ›
RF Wireless Technology. A radio frequency (RF) signal refers to a wireless electromagnetic signal used as a form of communication, if one is discussing wireless electronics. Radio waves are a form of electromagnetic radiation with identified radio frequencies that range from 3kHz to 300 GHz.
What is the basic RF propagation? ›
Radio waves can propagate from transmitter to receiver in four ways: through ground waves, sky waves, free space waves, and open field waves. Ground waves exist only for vertical polarization, produced by vertical antennas, when the transmitting and receiving antennas are close to the surface of the earth.
What is the basic RF modulation? ›
RF modulation is achieved by multiplexing the baseband signal with the carrier signal. Let s denote the baseband signal, c=cos(2πfct+θ c = c o s ( 2 π f c t + θ denote the carrier signal, m=s⋅c m = s ⋅ c is the modulated signal at the carrier frequency.
