# RF Wireless World

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This tutorial section on radar basics covers following sub topics:

### Frequency

The term frequency refers to total no. of completed cycles per second. It is expressed in Hz.

### Phase

The term phase refers to phase of EM wave and it is fraction of a full wavelength. It is measured in radians or degrees.

### Bandwidth

The term bandwidth is the frequency difference between upper frequency and lower frequency on EM spectrum radiation. It is expressed in Hz.

### wavelength

The term Wavelength is basically distance from wavecrest to wavecrest along direction of travel of EM wave. The unit is centimeter.

### Pulse Width

The term Pulse Width is time interval between leading and trailing edge of a pulse at a point where their amplitudes are 50% of the max. values. The unit is microseconds.

### PRF

The term PRF refers to Pulse Repetition Frequency which is no. of peak power pulses transmitted per second.

### PRT

The radar term PRT refers to Pulse Repetition Time. It is the time interval between two peak pulses.

### Duty factor

The term Duty factor is the amount of time radar transmits compare to listening time. It is often expressed in percent. It is calculated by multiplying PRF and pulse width OR
by dividing pulse width with PRT

### beam width

Beam width is the angle between the 3dB half power points on the main lobe. This is with reference to peak effective radiated power used on main lobe. The unit is degree.

The unit dBZ is the logarithmic Scale for measuring Radar reflectivity factor.
dBZ = 10 log( Z mm6 / 1 m3)
This dBZ value calculated using above equation, is what usually we will see displayed on the radar screen or on imagery downloaded from the website.

As we know that some degree of transmitted power is likely to be returned to the radar antenna as a result of backscattering. hence feflectivity is basically a measure of how much power was scattered back to the radar from the target. Pls. note that stronger the targets will have higher levels of reflectivity and hence they return more energy. Hence stronger targets have higher reflectivity values; i.e. higher dBZ levels. dBZ is also related to the number of drops per unit volume and the sixth power of their diameter.

Bistatic radar has two antennas; one for transmission and the other for reception. These antennas either located side by side or they are located far away.

monostatic radar is a radar which uses common antenna for transmission as well as reception OR uses two adjacent antennas for the same. Doppler weather radars are of this type.