ECE 402

Microwave Engineering

Laboratory Manual

School of Electronics Engineering (SENSE)

VIT University-Chennai Campus

Chennai, Tamil Nadu

Microwave lab Experiment List

B.Tech (ECE), SENSE

a) Hardware

1. V-I Characteristic of Gunn diode.

2. a) Measurement of VSWR and Determination of the Guide wave length .

b)To measure unknown impedance using Smith chart.

3. Study of Power divider, Waveguide TEE and Circulator characteristics.

4. To study the gain and radiation pattern of horn antenna (E-Sector and H-Sector

and Pyramidal)

5. Study of circulator and determination of the S-matrix.

6. Study of Reflex Kystron Characteristics.

B) Software experiment

1. Design and modulation of Microstrip line and modulation using AWR.

2. Design and modulation of power divider using AWR.

3. Design and modulation of Microstrip antenna. (Using AWR simulator, VNA)

4. Design and simulation Branch line coupler using AWR.

5. Design and simulation single-stage microwave FET amplifier using ADS tool.

6. Design and optimization of Resonator using AWR.

Faculties:

1. Dr. Usha Kiran K.

2. Prof. Chandrasekaren

2. Prof. Niraj Kumar

3. Prof. Sailaj V

4. Prof. Ravi Prakash Dwivedi

1. V-I characteristic of Gunn diode

Aim : To study the V-I characteristics of Gunn diode.

Components and equipments:

Gunn power, Gunn oscillator, PIN modular, Isolator, Frequency meter, variable

attenuator, slotted line, detector mount and VSWR meter.

Theory:

The Gunn oscillator is based on negative differential conductivity effect in

bulk semi-conductors which has two conduction bands minimum separated by an

energy gap (greater than thermal agitation energies). When applied the supply a

high field region is which travels towards anode. When this high field domain

reaches the anode, it disappears and another domain is formed at the cathode and

starts moving towards anode and soon. The time required for domain to travel from

cathode to anode (transit time) gives oscillation frequency.

In Gunn oscillator, the Gunn diode is placed in resonant cavity. In this case

the oscillation frequency is determined by cavity dimension rather than by diode

itself. Although Gunn oscillator can be amplitude-modulated with the bias voltage,

a separate PIN modulator through PIN diode for square wave modulation is used.

The ideal I-V charactertics of the Gunn diode is as shown in Fig. 2

Fig. 1: Set-up for study of GUNN oscillator.

Fig. 2: V-I characteristics of the GUNN oscillator.

Procedure:

1. Set the components and equipments as shown in Fig.1.

2. Initially set the variable attenuator for minimum attenuation.

3.Keep the control knobs of Gunn power supply as below

VSWR Meter switch OFF

Gunn bias knob Fully anti clock wise

PIN bias knob Fully anti clock wise

PIN mode frequency any position

4.Set the micrometer of Gunn oscillator for required frequency of

operation.

5.Switch ON the Gunn power s upp ly.

6.Measure the Gunn diode current to corresponding to the various Gunn

bias voltage through the digital panel meter and meter switch. Do not exceed the

bias voltage above 10 volts.

7. Plot the voltage and current readings on the graph.8.Measure the threshold

voltage which corresponding to max current.

8. Measure the Threshold Vothage (V th) at maximum amplitude of

current.

Note: Do not keep Gunn bias knob position at threshold position for more

than 10-15 sec. readings should be obtained as fast as possible. Otherwise due to

excessive heating Gunn diode burns.

Observation:

Results: V-I characteristics of the Gunn diode is measured.

Inferences: The threshold voltage is measured is 3.5 V and threshold

current is 510 mA.

2. MEASUREMENT VSWR, FREQUENCY AND

GUIDE WAVELENGHT AND UNKOWN

IMPEDANCE

AIM: a) To measure VSWR, Reflection coefficient, Return loss using slotted

section.

b) To measure frequency and guide wavelength.

c) Measurement of unknown impedance

Components:

Gunn power supply, Gunn oscillator, PIN modular, Isolator, Frequency

meter, Variable attenuator, Slotted section waveguide, Tunable probe, VSWR

meter, Waveguide stand, Movable short/matched termination.

Theory:

i) VSWR, Reflection coefficient, Return loss

Any mismatch in the transmission line and the load minimum

results in standing wave along the length of the line. The ratio of the

maximum voltage to the minimum voltage of the standing wave is called

VSWR.

Where |EI| and |ER| are respectively the amplitudes of the incident and

reflected electric field strengths. Further, the ratio of the reflected to the

incident electric field intensities is defined as reflection coefficient, i.e.,

Where ZL is the load impedance and Z0 is the characteristic impedance.

The return loss is given by = -20 log ()

Fig. 1: VSWR measurement set-up.

ii) Frequency and guide wave length:

For dominant TE10 mode in rectangular waveguide o, g, and c are

related as below:

where

o is free space wavelength, g is guide wavelength and c is cutoff wavelength For TE10 mode,

c = 2a where a is broad dimension of waveguide.

Procedure:

1. MEASUREMENT OF LOW AND MEDIUM VSWR (VSWR

2.

3.

4.

2. MEASUREMENT OF FREQUENCY AND GUIDE WAVELENGTH :

1. Set up the components and equipments as shown in Fig. 1.

2. Set the variable attenuator at maximum position.

3. Switch ON the Gunn power supply, VSWR Meter and cooling fan.

4. Keep the Gunn voltage above the threshold voltage.

5. Tune the probe for maximum deflection in VSWR meter.

6. Tune the frequency meter knob to get a dip on the VSWR scale and note down

the frequency directly from frequency meter.

7. Replace the termination with movable short, and detune the frequency meter.

8. Move probe along with the slotted line, the deflection in VSWR meter will

vary. Move the probe to a minimum deflection position, to get accurate

reading; it is necessary to increase the VSWR meter range db switch to higher

position. Note and record the probe position (d1-first minima position).

9. Move the probe to next minimum position and record the probe position again

(d2-second minima position).

10. Calculate the guide wavelength as twice the distance between two successive

minimum position obtained as above. (g = 2 (d2-d1)

11. Measure the waveguide inner broad dimension a which will be around

2.286cm for X-band.

12. Calculate the frequency by following equation:

where c = 3 108 meter/sec. i.e. velocity of light.

13. Verify with frequency obtained by frequency meter.

24. Above experiment can be verified at different frequencies.

15. Record the experimental results in a tabulated form as per format given in

Table 2:

Table 2: Measurement of frequency and guide wave length

Conclusions: The VSWR, frequency and guide wavelength is measured

Inference: The direct frequency reading is matching with the measured

frequency.

Sl

No.

Direct

Frequency

(GHz)

d1

(cm)

d2

(cm)

g = 2 (d2-d1)

(cm)

Frequency

(GHz)

2. c) Measurement of Unknown impedance using smith Chart

Block Diagram:

Theory:

The impedance at any point on a transmission line can be written in the form

R+jX. For comparison SWR can be calculated as

The unknown device is connected to the slotted line and the

position of one minima is de te rmined. The unknown device is

rep laced by s hort to the s lo t ted l ine . Two successive minima portions

are noted. The twice of the difference between minima position will be guide wave

length. One of the minima is used as reference for impedance measurement. Find

the difference of reference minima and minima position obtained from unknown

load. Let it be d. Take a smith chart, taking 1 as centre, draw a circle of radius

equal to S. Mark a point on circumference of smith chart towards load side at a

distance equal to d/g. Join the center with this point. Find the point where

it cut the drawn circle. The co-ordinates of this point will show the normalized

impedance of load.

PROCEDURE:

1. Find the distance minima for short as load at Vmin (do).

2. Next find minima position for matched load (dx).

3. From the above 2 steps calculate d = d1~d2

4 . W i t h t h e s a m e s e t u p a s i n s t e p 2 b u t w i t h f e w n u m b e r s o f

t u r n s ( 2 o r 3 ) . C a l c u l a t e VSWR.

5 . Draw a VSWR c irc le on a s mith char t .

6. Draw a line from center of circle to impedance value (d/g) from which

calculate admittance and Reactance (Z = R+jX)

Reading:

1. Minima with short do = ---------------- cm

2. Minimum with unkown load dx = ..cm

3. Shift in minima d = dx-do =-------------------cm

4. The shift in terms of wavelength = l = d/g = ---------------.

5. With matched load:

Frequency

First

minima

d1

Second

minima

d2

d= d2-d1

g= 2 d

VSWR

Measurement for unknown impedance:

Frequency Shift in minima

(cm)

l

Results: The unknown impedance is measured.

4. DIRECTIONAL COUPLER AND MAGIC TEE

Aim: a) To determine the coupling factor(C), Insertion loss (L), isolation (i) and

directivity coupler.

b) Study the characteristics of waveguide TEE.

Components: Gunn power supply, Gunn oscillator, PIN modular, Isolator,

Frequency meter, Variable attenuator, Slotted section waveguide, Tunable probe,

VSWR meter, Waveguide stand, detector mount direction coupler and magic TEE.

1. Directional Coupler :

Theory:

Fig.1: Measurement set-Up of the directional coupler

A directional coupler is a device with which it is possible to

measure the incident and reflected wave separately. It consist of two

transmission lines the main arm and auxiliary arm, electromagnetically

coupled to each other Refer to the Fig.1. The power entering, in the

main-ar m gets d ivided between po rt 2 and 3, and a lmos t no power

comes out in por t (4 ) Power entering at port 2 is divided between port 1 and

port 4.

The coupling factor is defined as Coupling (db) = 10 log [P1/P3] where

port 2 is terminated,

Isolation (dB) = 10 log [P2/P3] where P1 is matched.

With built-in termination and power entering at Port 1. The

directivity of the coupler is a measure of separation between incident

wave and the reflected wave. Directivity is measured indirectly as follows:

Hence Directivity D (db) = I-C = 10 log [P2/P1]

Main line insertion loss is the attenuation introduced in the

transmission line by insertion of coupler, it is defined as:

Insertion Loss (dB) = 10 log [P1/P2].

Produce:

1. Set the experiment as shown in the Fig. 1.

2. Connect the detector to the O/P of the variable attenuator and adjust

attenuator and VSWR meter gain control to get a convenient reference

full scale deflection of 0 dB on say 30 dB scale. Record the reference

power level as P1.

3. Connect the directional coupler in forward direction and terminate port

P2 with the matched load and connect the detector to port2 and measure

port 3 power level in dB. Record this as P3.

4. Next interchange the terminal at port 3 and measure power level at port 2

as P2.

5. Change the direction of the directional coupler.

6. Apply microwave signal to port 2 and measure power at Port 1 in dB.

(matched load port 3). Calculate for directivity.

7. Interchange the terminations and measure power at Port 3. Calculate for

isolation.

Tabular Column:

1. Forward direction:

Frequency Input

power

P1 (db)

P2

(dB)

P3

(dB)

Coupling

Co-efficient

C = P3-P1

(dB)

Insertion

Loss

L = P1-P2

(dB)

2. Reverse direction:

Frequency Input

power

P2 (db)

P1

(dB)

P3

(dB)

Directivity

D = P2-P1

(dB)

Isolation

I = P2-P3

(dB)

ii Magic Tee:

Theory:

\

The device Magic Tee is a combination of E and H plane Tee. Arm 3 is the

H-arm and arm 4 is the E-arm. If the power is fed, into arm 3 (H-arm) the

electric field divides equally betweenarm1 and 2 with the same phase and no

electric field exists in the arm 4. If power is fed in arm 4 (E-arm) it divides

equally into arm 1 and 2 but out of phase with no power to arm 3,

further, if the power is fed in arm 1 and 2 simultaneously it is added in arm 3 (H-

arm) and it is subtracted in E-arm i.e., arm 4.

Isolation: The Isolation between E and H arm is defined as the ratio

of the power supplied by thegenerator connected to the E-arm (port 4) to the

power detected at H-arm (port 3) when side arm1 and 2 terminated in matched

load.

Isolation (dB) = 10 log10 [P4/P3]

Similarly, Isolation between other ports may be defined.

Coupling Factor: It is defined as Cij = 10 /20

Where is attenuation / isolation in dB when i' is input arm and j is

output arm. Thus, = 10 log10 [j/i] Where P3 is the power delivered to arm i and

P4 is power detected at j arm.

Fig.2: Wave guide Tee Measuring set-up

Procedure: (Magic Tee)

1. Setup the components and equipments as shown in figure. 2.

2. Energize the microwave source for particular frequency of

operation and tune the detector mount for maximum output (Pin) .

3. With the help of variable frequency of operation and tune the

detector mount for maximum output at P3 a, set any reference as input

power.

4. Without disturbing the position of the variable attenuator, carefully place the

Magic Tee after the s lot ted l ine , keep ing H -a r m to s lo t ted l ine ,

de tec to r mount to E -a rm and ma tched termination to Port-1 and

Port-2.

5. Note down the power at E-arm i.e P4.

6. Determine the Isolation between Port-3 and Port-4 as I = P3-P4

7. Determine the coupling co-efficient from the equation given in

theory part.

8. The same experiment may be repeated for other Ports also.

Tabular column:

Sl. No: Input arm

(db)

Output arm

(dB)

Coupling

Coefficient

P1= P2=

P3=

P4=

C12=

C13=

C14=

P2 = P1=

P3=

P4=

P3= P1=

P2=

P4=

Results: The Isolation, coupling co-efficient, insertion loss and

directivity of the direction coupler is measured.

The isolation and the coupling co-efficient of the Magic Tee

is measured.

5. Radiation pattern and gain of the Horn antenna

Aim: To measure the gain of the Horn antenna and plot the radiation pattern.

Components: Gunn power supply, Gunn oscillator, PIN modular, Isolator,

Frequency meter, Variable attenuator, Slotted section waveguide, Tunable probe,

VSWR meter, Waveguide stand, detector mount, horn antenna, turn table.

Theory:

Many microwave communications, the transmission and reception of

microwave power to/from space is done through an antenna. The basic

characteristics of the antenna are bandwidth, gain and radiation pattern. A

transmission line shall act as an antenna if its output end is well matched to space.

Such an antenna because of having shapes like horns are known as horn antenna.

Radiation pattern:

The radiation pattern of an antenna is a diagram of the field strength in the

respective direction (degrees). The radiation pattern is measured in far flied at a

distance R = 2D2/o, Where D is the broader dimensions of the wave guide and o

is the free space wave length.

Gain of the antenna:

The gain of the antenna is given by

Where Pr receiving power

Pt Transmitting power

R- is the distance between the transmitting and receiving antennas.

The gain G(dB) = 10 log 10 (4r/o)+[(1/2) 10 log10 Pr]+[(1/2) 10 log10 Pt]

Beam width:

It is the angle between the two points of the main lobe at which radiated

power density is half of the total received power. Generally gain is highest when

beam width is less or narrow.

Fig. 1: Radiation pattern set up for horn antenna.

t

r

P

P

o

RG

4

Procedure:

1. Measured the transmitted power (Pt) by keeping the detector

mount at the attenuator near the transmitting end.

2. Next place the horn antennas at the transmitting and receiving ends

as shown Fig. 1. The distance between the antennas should be

more than R = 2D2/o

3. Align the antennas at 0 degree. Note that the antenna is of same

polarization.

4. Record the receiving power (Pr) at the 0 degree near receiving

end.

5. Calculate gain G dB

G(dB) = 10 log 10 (4r/o)+[(1/2) 10 log10 Pr]+[(1/2) 10 log10 Pt]

6. Rotate the turntable at the receiving end from 0 to 180 degree in

steps of 5 degree and note the respective powers from power

meter.

7. Take the normalized values of the received power and plot a graph.

8. Measure the beam width form the graph at the half power (3 dB)

points.

Tabular column: radiation pattern

The input power Pt = ---------dB

Angle in Degrees Received power (Pr)

(dB)

Normalized power

(dB)

Results: The horn antenna gain is measured and the radiation pattern is plotted.

Inference: The gain of the horn antenna is .dB

The beam width is

7. SCATTERING PARAMETERS OF THE CIRCULATOR

Aim: To Study the scattering parameters of the Circulator

i) Insertion loss of circulator ii) Isolation of circulator.

Components: X-band source, Isolator, Frequency meter, Variable attenuator,

Slotted section waveguide, Tunable probe, VSWR meter, Waveguide stand,

detector mount and circulator.

Theory:

1. ISOLATOR: The isolator have very small insertion loss in forward

direction and large in reverse direction.

2. CIRCULATOR: The circulator is a multi-port device which allows flow of

the signal in certain direction as shown in Fig. 1. A wave incident in Port1 is

coupled to port2 only, wave incident at port2 is coupled to port3 only and

So. The following are the basic parameters of isolator and circulator for

study.

3. ISOLATION: It is the ratio of power fed into input arm to the power

detected at uncoupled port with other port terminated in the matched load.

4. INPUT VSWR: The input VSWR of an isolator or circular is the ratio of

the voltage maximum to voltage minimum of the standing wave exiting on

the line when one port is terminated to the line and others have matched

loads.

Fig. 2: The Measurement of VSWR

Fig. 3: The measurement of insertion loss and isolation of the circulator.

Observation: Frequency VSWR Power at

P1 (dB)

Power at

P2 (dB)

Power at

P3 (dB)

Isolation

(P3-P1)

Insertion

loss (P2-P1)

Result: Insertion loss and isolation of the circulator is measured.

Inference: Insertion loss is less and isolation is more.

6. REFLEX KLYSTRON CHARACTERISTICS

Aim: To verify the characteristics of Reflex Klystron tube and to determine the

electronic tuning range.

Apparatus: Klystron Power Supply Klystron Tube, with Klystron, Isolator ,

Frequency Meter , Variable Attenuator , Detector Mount, Wave Guide Stand ,

VSWR Meter, Oscilloscope, BNC Cable.

Theory:

The Reflex Klystron makes the use of velocity modulation to transform continuous

electron beam energy into microwave power. Electrons emitted from the cathode

are accelerated and passed through the positive resonator towards negative

reflector, which retards and, finally, reflects the electrons and the electron turn

back through the resonator. Suppose an RF- Field exists between the resonator, the

electrons traveling forward will be accelerated or retarded, as the voltage at the

resonator changes in amplitude. The accelerated electrons leave the resonator at an

increased velocity and the retarded electrons leave at the reduced velocity. The

electrons leaving the resonator will need different time to return, due to change in

velocities. As a result, returning electrons group together in bunches. As the

electron bunches pass through resonator, they interact with voltage at the resonator

grids. If the bunches passes the grid at such time that the electrons are slowed

down by the voltage then energy will be delivered to the resonator and the

Klystron will oscillate. Fig. 2 & 3 shows the relationship between output power,

frequency and reflector voltages. The frequency is primarily determined by the

dimensions of the resonant cavity. Hence, by changing the volume of resonator,

mechanical tuning of Klystron is possible. Also, a small frequency change can be

obtained by adjusting the reflector voltage. This is called electronic tuning.

Procedure:

A) Carrier Wave Operation

1. Connect the components and equipment as shown in Fig.1.

2. Set the variable attenuator at the minimum position.

3. Set the Mod-switch of Klystron Power Supply at CW position, beam voltage

control knob to fully anticlockwise and reflector voltage control knob to fully

clock wise and the meter Switch to OFF position.

4. Rotate the knob of frequency meter at one side fully.

5. Connect the DC Microampere meter with detector.

6. Switch ON the Klystron Power Supply, VSWR Meter and Cooling Fan for the

Klystron Tube.

7. Put on beam voltage switch and rotate the beam voltage knob clockwise slowly

up to 300V meter reading and observe beam current position, the beam current

should not increase more than 30mA.

8. Change the reflector voltage slowly and watch current meter. Set the voltage for

maximum deflection in the meter.

9. Tune the plunger of klystron mount for the maximum output.

10. Rotate the knob of frequency meter slowly and stop at the position, where there

is lowest output current on multimeter. Read directly the frequency meter

between two horizontal line and vertical marker. If micrometer type frequency

meter is used, read the micrometer reading and use the frequency chart.

11. Change the reflector voltage and read the current and frequency for each

reflector voltage.

B) Square Wave Operation

1. Connect the equipment and components as shown in figure1.

2. Set micrometer of variable attenuator around some position.

3. Set the range switch of VSWR meter at 40dB position, input selector switch to

crystal impedance.

4. Set Mod-Selector switch to AM-MOD position, beam voltage control knob to

fully anticlockwise position.

5. Switch ON the klystron power supply, VSWR meter, cooling fan.

6. Switch ON the beam voltage switch and rotate the beam voltage knob clockwise

up to 300V deflection in meter.

7. Keep the AM-MOD amplitude knob and AM-FRE knob at mid position.

8. Rotate the reflector voltage knob to get deflection in VSWR meter.

9. Rotate the AM-MOD amplitude knob to get maximum output in VSWR meter.

10. Maximize the deflection with frequency knob to get maximum output in

VSWR meter.

11. If necessary, change the range switch of VSWR meter from 30dB to 50dB if

the deflection in VSWR meter is out of scale or less than normal scale

respectively.

Further the output can be also reduced by variable attenuator for setting the output

for any particular position. Find the oscillator frequency by frequency meter as

described in the earlier set up.

C) Mode Study on Oscilloscope

1. Setup the components and equipments as shown in figure1.

2. Keep the position of variable attenuator at minimum attenuation position.

3. Set the mode selector switch to FM-MOD position, FM amplitude and FM

frequency knob at mid position, keep beam voltage knob fully anticlockwise and

reflector voltage knob to fully clockwise position and beam switch to OFF

position.

4. Keep the time/division scale of oscilloscope around 100Hz frequency

measurement and Volt/div to lower scale.

5. Switch on the Klystron Power Supply and Oscilloscope.

6. Switch ON beam voltage switch and set beam voltage to 300V by beam

voltage control knob.

7. Keep amplitude knob of FM Modulator to maximum position and rotate

the reflector voltage anticlockwise to get modes as shown in figure2. on the

Oscilloscope. The horizontal axis represents reflector voltage and vertical axis

represents output power.

8. By changing the reflector voltage and amplitude of FM modulation, any

mode of Klystron Tube can be seen on Oscilloscope.

Fig. 1 Set up for Klystron Oscillator

Fig. 2 Modes of Klystron Oscillator

Tabular Form:

S.No Repeller

Voltage

Frequency PowerMeter

reading(dBm)

Result: The characteristics of Reflex Klystron has been studied and modes have been found.

Software Experiments

Objective: To study the performance of different two port networks by

determining their scattering parameters.

Equipment required : AWR Microwave Office software

Specifications : Characteristic impedance Z0 =

Operating frequency f =

Substrate thickness H =

Metal thickness T =

Dielectric constant r =

Loss tangent L =

Theory :

Microstrip lines: The simple microstrip line uses a single strip conductor on the

dielectric that rests on a single ground plane. Generally the ground plane made up

of with good conductor like silver or copper and the material used for the dielectric

is Teflon or Aluminum or Silicon, etc.. It is possible to use several independent

strips with the same ground planes and dielectric. Microstrip lines use quasi TEM

mode of propagation. The ground plane of the microstrip line must be wide

compared with the top conductor, so it appears like a nearly infinite wide ground

plane with only very small electric field fringes at its edges. The characteristic

impedance of a microstrip line depends on the strip line width, thickness, the

distance between microstrip line and ground plane and the dielectric constant of

the dielectric material.

Figure 1

Design Equations: The effective dielectric constant is calculated by:

W

H

rre

1212

1

2

1

2

0

0

0

8

244 2

12 0.611 ln(2 1 ln( 1) 0.39

2

1 1 0.110.23

60 2 1

377

2

2

A

a

r

r

r r

r r

r r

r

g

e

eWforZ narrowstrip

HB B B

ZA

B forwidestripZ

l l

2

gl

W= Width of the microstrip line, l = Length of transmission line, H = Thickness of

the substrate, A,B constants, = Phase shift, g=Guide wavelength.

Sample Observations: The behaviour of a two port network when matched with

50 ohm at both input and output ports for a typical microstrip line with the

following specifications is shown below.

Z0 = 50 , f = 3 GHz , H = 1.6 mm, T = 0.036 mm, r = 4.4 , L = 0.001

Model graph:

1 2 3 4 5 6

Frequency (GHz)

Graph 1

-150

-100

-50

0

DB(|S(1,1)|)TWO PORT NETWORK

DB(|S(2,1)|)TWO PORT NETWORK

Practical Observations:

Frequency S11 S12 S21 S22

Conclusions:

2. MICROSTRIP POWER DIVIDER

Aim: 1. To design and simulation of a Wilkinson power divider for equal and

unequal power divisions.

2. To determine the scattering parameters of Wilkinson power divider.

Equipment required: AWR Microwave Office software

Specifications: Characteristic impedance Z0 =

Operating frequency f =

Substrate thickness H =

Metal thickness T =

Dielectric constant r =

Loss tangent L =

Figure (1)

Theory: The Wilkinson power divider is generally designed using microstrip lines

as shown in figure 2 and can be made with any number of ports with equal or

unequal power divisions. Wilkinson power divider has many advantages over

other power dividers and has the following properties

1. Matched at all ports.

2. Large isolation between output ports

3. Reciprocal

4. Lossless when output ports are matched

The S-matrix of a 3-port Wilkinson power divider is given by

Figure (2)

Design Equations:

02 2

[ ] 0 02

0 02

j j

jS

j

KZR

KZR

KKZR

kKZKZZ

K

KZZ

P

PKionRatioPowerdivis

/

)1

(

)1(

1

03

02

0

2

0

2

0302

3

2

003

2

32

Sample Observations: For equal power division, sample results of a Wilkinson

power divider shown below

Z0 = 50 , f = 3 GHz , H = 1.6 mm, T = 0.036 mm, r = 4.4 , L = 0.001

Model graph:

Practical Observations:

Frequency S11 S21 S31 S32

Conclusions:

1 2 3 4 5 6

Frequency (GHz)

S parameters

-80

-60

-40

-20

0

DB(|S(1,1)|)Wilknson divider

DB(|S(2,1)|)Wilknson divider

DB(|S(3,1)|)Wilknson divider

DB(|S(3,2)|)Wilknson divider

3. DESIGN AND SIMULATION BRANCH LINE COUPLER

Aim: To Design and simulate branch line coupler using AWR software

Components : AWR Software

Theory:

A branch-line coupler outputs from the coupled port 3 a fraction of the

power presented at the input (pin 1). The remainder of the power is passed

through to the output port (pin 2). At the center frequency the phase difference

between the outputs is 90 degrees, with the coupled port representing the

quadrature (Q) output and the output port representing the in-phase (I) output.

The coupling coefficient specifies the ratio of the input power to the coupled

power (P1/P3). Pin 4 represents the isolated port, and it is typically well isolated

from the input port near the center frequency. The coupling coefficient must be

positive and greater than 3 dB. Best results are obtained for tight couplings of 6

dB or better (C < 6 dB). Choosing the coupling parameter larger than 6 dB often

causes width constraint violations to occur on the MTEE components, resulting

inwarning messages during design and simulation. A coupling coefficient of 3

dB provides an equal power split between the two outputs.

Fig. 1 Branch line coupler

PROCEDURE:

Step1: Open the AWR software.

Step2: Create a new project from the file menu

Step3: Open the Axiem window of AWR.

Step4: Define material and thickness

Step5: Draw branch line coupler in AWR by selecting the co-ordinates.

Step 6: Connect the ports for all the branches as shown below:

Fig. 2: Branch line coupler in AWR

Step 7: Specify the desired frequency range for simulation and press simulation

ICON

Result:

The obtained characteristics of the simulated results of Branch line coupler

is as shown in the Fig. 2. The results graph show that the branch line coupler is

well matched and resonates at 2.59 GHz. The isolation and return loss

characteristics are below 20 dB. The coupled power of 3db is obtained in the

port 3.

Fig. 9 : S-parameters of Branch line coupler.

Conclusion: Branch line is designed, developed and simulated using AWR.

4. DESIGN AND SIMULATION OF MICROSTRIP ANTENNA. (USING AWR SIMULATOR)

Aim: To Design and simulate Microstrip antenna using AWR Software..

Components: AWR Software

Theory:

Microstrip antenna consists of patch on one side of the substrate and a

ground plane on the other side. The length of the microstrip patch antenna consists

of lambda/2 patch which acts as a open circuited transmission line. The Microstrip

antenna radiates from the edges open ended circuited line. The design formulas

are as follows:

Procedure :

Step1: Open the AWR software.

Step2: Create a new project from the file menu

Step3: Open the Axiem window of AWR.

Step4: Define material and thickness of the substrate used.

Step5: Draw rectangular patch in AWR by selecting the co-ordinates as shown in

below figure.

Fig. 1: Design of Microstrip antenna

Step 6 : Appropriate 50 ohm Microstrip feed to the antenna.

Step 7: Connect the ports for the antenna and terminate the port to the ground.

Step 8: Specify the desired frequency range for simulation and press simulation

ICON

Results: The simulated results are as shown in the below Fig. 2. For the figure it is

seen that the antenna resonates at 900 MHz. Good Returns loss of -25 dB is

obtained.

Fig. 2: S11 characteristics of MSA

Conclusion: Microstrip antenna is design and develop in AWR. the antenna resonates at 900 MHz. Good Returns loss of -25 dB is obtained

5. SINGLE STAGE FET AMPLIFIER USING IMPEDANCE

MATCHING NETWORKS

Aim: Study of Single stage FET amplifier using impedance matching networks for maximum gain.

Components: HFSS designer

Theory: To realize maximum gain, the input and output matching

networks are simultaneously conjugate matched to the transistor from

the following Fig.1

Fig.1: The general transistor amplifier circuit

1. Stability of amplifier. First the amplifier as to satisfy the stability criteria:

2. Reflection co-efficient calculation:

Where

3. Gains of the amplifier:

Procedure:

1. The matching network used here is open stub.

2. Using smith chart we should find the stub length as shown in the figure.

Procedure for finding stub length:

1. Start by marking magnitude and phase of s in the smith cart. Find the zl at that point. We usually find stub length interms of admittance.

2. Compute yl on the smith chart. 3. Draw a circle with radius is equal to zl. Note the point where the circle

cuts the unit admittance circle and mark as y2.

4. For line length l1 move from yl to y2 and measure the distance. 5. For open stub toward y2 from y=0 in clockwise direction. 6. Likewise repeat for L.

3. After finding stub length using HFSS Cad software tool we simulate transistor as the softer ware as follows:

Results:

From the graph the gain can be calculated using S21 parameter and the S11 gives return loss

Results: The transistor has resonated at 4.8 GHz with return loss S11 = -22dB. The transducer gain of the transistor is S21= -3.3dB at 4

GHz.

Inferences: The transistor is matched using open stub impendence and

transistor is a narrow bandwidth amplifier.