Posts by tag 'rf-engineering'

What Is the Noise Floor? Thermal Noise, SNR and Receiver Sensitivity Explained

The noise floor is the faint thermal noise present in every receiver, the level a wanted signal has to rise above to be decoded. At room temperature it starts at −174 dBm per hertz, then climbs with bandwidth and the receiver noise figure. Add the signal to noise ratio your modulation needs and you have the receiver sensitivity. Here is where −174 dBm/Hz comes from, the noise floor formula with a reference table, how noise figure and SNR fit in, and a worked example that turns into a sensitivity figure.

RF Engineering

How to Calculate an RF Link Budget: A Step by Step Guide with a Worked Example

A link budget adds every gain and subtracts every loss between a transmitter and a receiver to predict the received power, then compares it against the receiver sensitivity to see whether the link will work. Here is the formula, an at a glance budget table, a worked example for a 5.8 GHz point to point link, and the engineering considerations, fade margin, propagation and noise, that decide whether the design survives in service.

RF Engineering

dBm to Watts, dBi vs dBd and dBc: Every RF Decibel Explained (with Conversion Tables)

0 dBm is 1 mW and +30 dBm is 1 watt, so every 10 dB is a tenfold change in power and every 3 dB roughly doubles or halves it. Here is what dB, dBm, dBW, dBi, dBd and dBc each mean, how to convert dBm to watts in both directions, a full conversion table, the dBi to dBd offset, EIRP, and the mistakes that trip people up.

RF Engineering

What Is a Good VSWR? VSWR, Return Loss and Reflected Power Explained

A good VSWR is usually 1.5:1 or better, and 2:1 is the common acceptance limit. Here is what VSWR actually measures, how it converts to return loss, reflection coefficient and reflected power, a conversion table, target values by application, and the real reasons a high VSWR matters.

Compliance

How Far Do You Need to Stay From a Transmitting Antenna? RF Exposure Safe Distances Explained (ARPANSA RPS S-1 / ICNIRP)

The safe distance from a transmitting antenna depends on its radiated power, its frequency, and whether the person is a worker or the public. Here is the ARPANSA RPS S-1 and ICNIRP formula, a 900 MHz worked example, a compliance distance chart, and the reasons a single distance is rarely the full answer.

RF Engineering

How to Specify a Coaxial Cable for the Job

A coaxial cable is not a single part number, it is a specification: impedance, loss at frequency, shielding, power, environment, and a connector chosen independently for each end. Here is how to get it right.