RF/Microwave Glossary of Terms
Click on the first letter of the desired topic to get definitions of RF & Microwave Terms.
A - G
Conversion Loss
The ratio in dB of the IF output of a mixer to the rf input power. All conversion loss measurements and specification are normally based on the mixer being terminated on all ports and a stated LO signal power level being applied.
Dynamic Range
The range, from the minimum, which is at a level 3 dB above the amplifier’s internally generated floor, to a maximum input signal level that a component can accept and amplify without distortion.
Dynamic Range = P1dB – PMDS
Where:
PMDS = Minimum detectable signal 3 dB above the noise floor.
Gain
Gain is the ratio of the power output to the power input of the amplifier in dB. The gain is specified in the linear operating range of the amplifier where a 1 dB increase in input power gives rise to a 1 dB increase in output power. Gain = 20*log(S21)
H - N
Insertion Loss
Insertion Loss (dB) is defined as the drop in power as a signal enters an RF component. This value not only includes the reflected inconming signal, but also the attenuation of the component.
Insertion Loss (dB) = 10 * LOG10(Output Power/Incident Power)
Isolation
The ratio (expressed in dB) of the power level at one port compared to the resulting power level of the output port.
Limiting Level
This is the input power level when the output power is goes into compression and no longer becomes linear.
Noise Figure / Noise Factor
The Noise Factor of a transducer at a specified input frequency is the ratio of (a/b) where “a and b” are:
- (a) the available Signal to Noise Ratio (SNR) at the signal generator terminals per unit bandwidth when the temperature of the input termination (generator or source) is 290°K and the bandwidth is limited by the transducer, to
- (b) the available SNR per unit bandwidth at the output terminals of the transducer.
Traditionally:
Noise Figure NF = 10 log(noise factor F)
Noise Temperature (Te) = To(F – 1)
Where:
Te is the noise temperature
To is standard temperature 290 K
F is noise factor
Noise Floor
This is defined as the lowest possible input to a chain or a component, that will produce a detectable output.
Noise Temperature
This is the amount of thermal noise in a chain or a component. Noise Factor and Noise Temperature (Te) are related as follows:
Noise Temperature (Te) = (F – 1)To
Where:
Te is the noise temperature
To is standard temperature 290 K
F is noise factor
For example, a noise figure of 2.0 dB is equivalent to a Noise Temperature of 170 K.
O - P
One dB Compression Point
The 1 dB compression point is the point on a Pout vs. Pin graph, where an increase power input causes the measured gain to decrease from the linear gain by one dB. Typically, if not explicitly stated, the 1 dB compression point refers to the output power (Pout) at that point.
Pushing
The change in frequency when the supply voltage changes, expressed in MHz/V.
Q - T
Return Loss
Return Loss (dB) is defined as a ratio of the incoming signal to the same reflected signal as it enters a component.
Return Loss (dB) = 10 * LOG10(Reflected Power/Incident Power)
Scattering Parameters
Better known as S-Parameters, these 4 values help define the performance of several variables at various frequencies.
S11 (Input Reflection Coefficient ) = b1/a1
S12 (Isolation) = b1/a2
S21 (Forward Transfer Coefficient or Gain /Loss) = b2/a1
S22 (Output Reflection Coefficient) = b2/a2
Spurious Free Dynamic Range
Spurious Free Dynamic Range = 2/3 (PTOI – Gain – PMDS)
Where:
P1dB = 1 dB Output Compression Point
PTOI = Third Order Intercept
PMDS = Minimum detectable signal 3 dB above the noise floor.
Third Order Intercept
The third order intercept is the intercept point formed by the intersection of the fundamental output and the two-tone third order distortion product, when plotted as a theoretical linear function of input power. The higher the Third Order Intercept, the lower the intermods for the incoming signals.
U - Z
VSWR
Voltage Standing Wave Ratio simply put is the ratio of the maximum to the minimum voltage of a standing wave (which is the instantaneous sum of incident and reflected waves). Ideal is a figure of 1:1 which means that 100% of the incoming signal passed through the component without any reflection. In that case, there would be no standing wave. A 2:1 VSWR (or mismatch) means that 12% of the incoming signal was reflected.