microwave
Microwave is a kind of electromagnetic wave with very short wavelength. Its wavelength is between 1 m m and 1 m, and its corresponding frequency is between 300 GHz and 300 MHz.

Microwave Technology
It is a special technology to study the generation, modulation, demodulation, amplification, transmission, transmission and application of microwave signals.

Noise figure
Noise figure represents the deterioration of the amplified signal noise of a microwave device. The noise figure of any microwave device is defined as follows: Nf= (Sin/Nin)/(Sout/Nout) where (Sin/Nin) the signal-to-noise ratio of the input signal and (Sout/Nout) the signal-to-noise ratio of the output signal.

Power gain
There are many definitions of power gain, such as utility gain, actual gain, etc. For the practical amplifier, power gain means that the signal source and load are measured by network analyzer under the condition of 50_standard impedance, considering the input and output mismatch of the amplifier.

Gain flatness
The fluctuation of power gain in the specified frequency band is expressed by the decibel difference between the maximum gain and the minimum gain.

gain

• Gain is used to indicate the degree of concentrated radiation of the antenna. The gain of an antenna in one direction is defined as the ratio of the square of the electric field intensity (E2) generated by an antenna in one direction to the square of the electric field intensity (E02) generated by a lossless ideal point source antenna in the same direction and position, usually expressed in G, at the same input power. G = E2/E02 (same input power)

• Similarly, the gain can also be determined by the ratio of input power (Pino) to input power (Pin) of a lossless ideal point source antenna under the condition that the same electric field intensity is generated in a certain direction and a certain position, which is called the gain of the antenna in the point direction.

• G = Pino / Pin (same electric field strength)

• Usually the gain of the antenna in the maximum radiation direction is used as the gain of the antenna. Gains are usually expressed in decibels. That is: G = 101g Pino/Pin antenna gain calculation: G = 4Pi S/lambda 2 = _(pi/lambda) 2D2

• In the formula, S-antenna aperture area (square meters); lambda-working wavelength (meters); D-parabolic aperture (i.e. aperture diameter) (meters); _-antenna efficiency.

Directional pattern
If the intensity of the radiation strikes of the anti-antenna in all directions is expressed by the length of the vector starting from the origin, the envelope formed by connecting all the vector endpoints is the pattern of the antenna. It shows the relative radiation of antenna in different directions, which is called stereo pattern. The direction of the vector diameter represents the direction of radiation, and the length of the vector diameter represents the intensity of radiation shock. The pattern contains many lobes, in which the lobe containing the maximum radiation direction is called the main lobe. Others are called first sidelobe, second sidelobe, etc.

Main lobe width
It is defined as the width of the gain decreasing by 3 decibels relative to the maximum gain in the directional graph, in units of degree (radian).

Sidelobe level
The ratio of the maximum of the side lobe to the maximum of the main lobe is called the side lobe level, which is generally expressed in decibels and is defined as 101g (maximum power of the side lobe/maximum power of the main lobe).
For example, the ratio of the maximum power of the side lobe to the maximum power of the main lobe is 0.01, and the side lobe level is -20dB.

Polarization mode
The polarization forms of electromagnetic wave can be divided into linear polarization wave and circular polarization wave. Linear polarization wave can also be divided into horizontal polarization wave and vertical polarization wave. Circular polarization wave can be divided into left-handed and right-handed circular polarization wave according to the rotation direction of electric field.

VSWR
Voltage standing wave ratio (VSWR) is used to describe the matching performance of ports. The same performance can also be expressed by echo loss. These two indicators are defined as follows.

VSWR:
VSWR=(1+ | R |)/(1-| R |) r: For emission coefficient = ZL-Z0/ZL+Z0 ZL as input impedance, Z0 as ideal impedance

Echo loss:
RL = 10log (incident power / reflective power) 

dynamic range
Refers to the maximum and minimum power range allowed by the input signal. The lower limit is limited by the noise performance of the amplifier, and the upper limit depends on the non-linear index.