PIN DIODE

 

 WHAT  IS PIN DIODE?

                                           

                                                       

                                                      FIG. PIN DIODE

             

 

DEFINITION OF PIN DIODE:

  

It consists of a  layer of  N & P-type semiconductor material. In between them lightly dopped intrinsic layer is present, so it is called PIN diode.

SYMBOL OF PIN DIODE:

                             

PIN DIODE BASICS:

 

It is made up of a 3-layer P-type layer, I-type layer, N-type layer.

P-layer having holes as a majority carrier layer N-layer having electrons as majority carrier & I is an intrinsic layer means pure semiconductor layer.

because of additional I-intrinsic layer added in the PIN diode  offer high resistance.

It has a lower capacitance due to an intrinsic layer between the P & N-type layer.

P & N-type semiconductor material consists of either silicon or gallium arsenic material.

When adding I-layer then distance increase & capacitance decrease  

PIN diode act as a low-frequency rectifier.

PIN  DIODE CHARACTERISTICS:

1.LOW  CAPACITANCE:

By adding an Intrinsic layer in between P-N type layer then the distance between two layers are increase & capacitance decrease. Hence, lower capacitance.

2.HIGH BREAKDOWN VOLTAGE:

Due to an additional intrinsic layer in between P & N. Hence, reverse breakdown voltage increase.

3.CARRIER STORAGE:

Because of the  intrinsic layer in between P & N. Charge carrier which are due to P & N-type material that can be stored in the intrinsic layer.

Under zero & reverse-biased  PIN diode  has a very high impedance at uwave frequency & low impedance for small forward current.

At higher frequency PIN diode act as a variable resistance.

FIG.(d) CONSTRUCTION OF PIN DIODE      

 

OPERATION:

 

1. ZERO BIAS:  

                     

                                     FIG. ZERO BIAS

In zero bias Battery is not connected to the PIN diode.

The depletion region is present in between Intrinsic layer & N-type layer. electrons & holes charge carrier in intrinsic layer is store in between P & N-type layer.

 2. FORWARD BIAS:

In forward bias condition of  PIN diode  +ve  terminal of the battery is connected to anode &  -ve terminal of the battery is connected to cathode then depletion region in between intrinsic layer & N-type layer start to decrease the depletion region.

After cancelling the depletion region start the flow of current.

In forward bias PIN diode work as a variable resistance.

The depletion region decreases then resistance decrease.

Small resistance in the range 1 ohm to 10 ohm

so, PIN diode act as an ON state in the other word, the switch is ON

RADAR DISPLAY A, B, F-SCOPE DISPLAY

 A   SCOPE  DISPLAY

 

 

 

 

 

                                     FIG. A SCOPE DISPLAY

It is a popular display.

A-scope Display is the deflection modulation type display system.

It identifies the range of the target. A scope display operation is similar to that of an ordinary CRO.

Linear sawtooth voltage is applied to the horizontal deflection plates in synchronism with the transmitted pulse. Hence, the beam is produced to scan the CRT screen horizontally.

The demodulated echo signal is obtained from the receiver & the demodulated echo signal is applied to the vertical deflection plate to cause vertical deflection from the horizontal line.

If the echo signal is absent then Display is a simple horizontal line.

1st blips due to transmitted pulse.

In addition to this blips are corresponding to:

1. GROUND CLUTTER:

Echos signal from a various fixed object near Transmitter & from the ground.

1. Grass noise.

Constant Amplitude & continuous receiver noise.

3. Actual  target

The distance of the blips from the reference blip gives the range of the corresponding target. 

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ADVANTAGE

1. Gain control for vertical deflection can be provided, which allow sensitivity to be increase for weak signal & reducing for strong ones. In the case of a strong echos signal, reducing the Amplitude of grass noise.

LIMITATION & APPLICATION

1.Distance of the target can determine & not it's direction as an antenna direction can be determined 

 

 B SCOPE DISPLAY

 

 

 FIG. B - SCOPE DISPLAY

 It is a modulated Display.

The horizontal axis represents the azimuth angle & the vertical axis represents display.

If two targets are at a constant cross range, they become visible at different separations at different ranges.

F - SCOPE DISPLAY

                                                

                                                      

                                     FIG. F- SCOPE DISPLAY 

 It is a rectangular display.

The vertical axis represents the elevation angle & the axis represents the azimuth angle. The target becomes visible as a centralized blip when the antenna looks at the target.

RADAR. what is RADAR? Basic principle of Radar system. Advantages & disadvantages of Radar system. Application of Radar system. Monostatic Radar. Bistatic Radar

 WHAT IS RADAR?

 

RADAR stands for Radio Detection & Ranging

It is basically a system used to detect the reflecting object such as aircraft, ships, spacecraft, vehicles, people  & the natural environment.

BASIC PRINCIPLE  OF RADAR SYSTEM

 

                                            FIG. BASIC PRINCIPLE OF RADAR

RADAR is an object.

The transmitter in RADAR generates electromagnetic waves to determine the range, Angle, Distance & Velocity of the target.

The transmitter generates an electromagnetic wave & radiated through the antenna toward the target through free space. These electromagnetic waves reflected again from the target in a form of an echo signal.

These echo signals are received through an antenna. Based on the echo signal, RADAR can measure Range, Distance, Velocity & Angle of Target.

The doppler frequency shift is widely used in radar for separating the moving target from the fixed target.

Echo signal receives from the fixed target such as Land, Sea, Rain is called Clutter. Clutter is the unwanted signal.  

ADVANTAGES OF   RADAR

1. RADAR can identify unknown objects through Darkness, Rain, Fog, Snow.

2. RADAR can identify the Range, Distance, Angle, Position & Velocity of the target based on the             Echo signal.  

LIMITATION

1.RADAR can not be used for short distances.

2.RADAR  can not identify the colour of the target.

 

APPLICATION

It is used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather terminology.   

 

 BISTATIC  RADAR

 

                                 FIG. BISTATIC RADAR

 

The RADAR system consists of a transmitting antenna which is connected to the transmitter  & an antenna is connected to the receiver. such a RADAR system is called a BISTATIC  RADAR.

 The transmitter radiates an electromagnetic wave generated by the oscillator. A portion of the wave reflected back from the target in a form of an Echo signal in all directed toward the receiver.

The receiver antenna collects the returned Echo signal & deliver it to the receiver. The receiver detects the target & its relative velocity. which respect to the Radar station. If the target is moving.

MONOSTATIC  RADAR

 

 

                                           FIG. MONOSTATIC  RADAR

 

A single antenna is used for both transmitting & Receiving signals in a  RADAR is called a Monostatic RADAR. 

RADAR consists of a transmitter, a receiver, a display & an antenna.

The function of the Duplexer is:

1.To separate the transmitter & receiver during transmission & reception.

2.To protect the receiver from high power transmitter.

3.It uses a single transmitter/receiver antenna.

It is possible to detect the height, speed & direction of the target & time taken for the Echo to come back after reflection from the target.

The display screen indicates the target data.

FACTORS  AFFECTING  THE   MAXIMUM  RANGE  OF  RADAR:

(A)   TRANSMITTER  POWER:

In case the Radar range is to be doubled, we have to increase the transmitter power  16 times.

If   Rmax↑=2Rmax

   Then  Pt↑=16 Pt

since  Rmax ∝ Pt  to the power¼ 

(B) FREQUENCY :

 The increase in frequency increase in Range

Rmax ∝  √for  Rmax ∝ 1\√λ

 then   √f  =  1\√λ

 

GYRATOR BASICs, WORKING, STRUCTURE

 

 

 

                                                            fig. GYRATOR

 

It is a two-port microwave device that is used to introduce a  degree or 0-degree phase shift of electromagnetic wave propagation in forward direction or reverse direction.

Electromagnetic wave propagation in forward transmission from port 1 to port 2& 0-degree phase shift in reverse transmission from port2 to port1.

It consists rectangular waveguide at the receiving & transmitting end with a 90-degree twist which is connected to a circular waveguide. 

In the middle section of a  waveguide having ferrite rod. over the ferrite rod permanent magnet is placed.

According to faraday's rotation principle, an electromagnetic wave propagating from port1 to port2 in forward transmission, it passes through the twist, it introduces a 90-degree phase shift in a counter-clockwise direction & another 90-degree phase shift introduce by ferrite rod in a counter-clockwise rotation. so, the total angle of rotation is a 180-degree phase shift.

An electromagnetic wave propagating a 0-degree phase shift in reverse transmission from port 2 to port 1 then it introduces a 90-degree phase shift  by an in clockwise rotation & another 90-degree phase shift by ferrite rod rotation. Hence, two rotations cancel out each other. Hence, the 0-degree phase shift is introduced.😎