Long Report3 RF

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RF AND MICROWAVE TECHNIQUES

BENT 4153 Page 1

TITLE:LOW PASS FILTER AND BAND PASS FILTER

1.0 Objective:

To investigate the operation of various type of microwave filters.

2.0Equipment:

ED-3300L, ED 3300M Module, RF cables, connectors

3.0Theory

The filter allows for passing a certain frequency and attenuates the others

out of various frequency components. It is one of the most frequently usedcircuits in the entire RF system, and can be formed in variety of types and

shape.

Before understanding the filter in various points of view, first take a look

at the filter by sing a representative RF characteristics graph, S parameter.

When the RF is applied to a common line, all the RF signals are obtained

as the output except for a little transmission line loss. S21 of 0dB in the S

parameter means that the ratio of the output to the input is unity. That is,

since 10*log1=0, the input power is transmitted to the output without loss. S 11

locating lower than S21 , indicates that the reflected amount is very small.

Such a case that S21, is maintained as about 0dB and S11 has a small value,

means that the input signal of the corresponding frequency is transmitted to

the output at its maximum and the reflected occurs at its minimum. That is, it

corresponding to the frequency pass band. Contrarily, when S 21 is small and

S11 is about 0 dB, it means the input signal of the corresponding frequency is

mostly reflected and not transmitted, which becomes the frequency stop band.

Passing a specific frequency to the output at its maximum without loss and

reflected the other frequencies are main roles of the filter.

i) Low pass Filter

This filter is basic type of the entire filter. The LPF (Low Pass Filter)

blocks the radio frequency signals and transmits only the necessary low


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frequency signal (within the block frequency). It is formed as the

simplest form, and other types of filters can be made by converting this

basic form in variety. This type of filter is fairy used in the various areas

such as removing the low frequency ripple, removing the radio frequency

spurious, suppressing the harmonic and various detections.

ii) High Pass Filter

The High Pass Filter (HPF) has a charistics that blocks the low frequency signal

and transmitts only the radio frequency signals higher than the necessary

bandwidth (higher then the lock frequency). The biggest problem if the filter is

that it cannot be formed using the distributed element.

iii) Band Pass Filter

The Band Pass Filter (BPF) transmits signals in the desirable bandwidth while it

blocks signals in the undesirale bandwidth. When the transmission terminal

receives or transmits the exectly necessary frequency out of many frequencies,

the BPF is used.

iv)` Band Stop Filter or Band Reject Filter

In contrast of the BPF, the BSF blocks signals in the desirable bandwidth, while

it passes signals in the other bandwidth. This filter is mainly used for blockinginflow of the specific frequency and is formed by arranging and combining the

serial and parallel resonances.

4.0Procedure:

1. Construct and connect the equipment at the below for the Low Pass Filter

and Band Pass Filter.


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BENT 4153 Page 3

Figure 1: LOW PASS FILTER CONNECTION

Figure 2: BAND PASS FILTER CONNECTION

2. Connect the Voltage Control Oscilloscope (VCO) to power supply and all

the calibration methods for the equipments was done with carefully

before start experiment such as setting to power supply, function

generator, and spectrum analyzer.

3. The power supply connected to Voltage Control Oscillator (VCO) and was set at

12V MAX in function generator. It is because the range of maximum voltage

supply for VCO is 16V.

4. The output from the VCO was connected to the circulator port 1(P1) using

connector cable.

5. The P2 of the circulator was connected to low pass filter and P3 was terminated

using a 50ohm load.

6. The output from the filter was connected to spectrum analyzer via a detector. All

the results were recorded in tables.

7. The channel 1 adjustable voltage tuned using start and stop frequency values

between 1.5 to 2GHz in the spectrum analyzer such that the output power can be

determined easily.

8. The channel 1 V tune voltage of the ED-3300A(VCO) was changed such that the

output voltages can have frequency values shown in table 1. Then with the


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BENT 4153 Page 4

detector the measurement was recorded in the input of table 1.

9. The low pass filter was replaced by band pass filter and results was

measured and recorded in table 2.

10.The calculations to find the reflection coefficient and the values of the

filter components were done and analysis of the response of the signal was

shown in graphs.

5.0 Results and observations:

Low Pass Filter

Frequenc

y (GHz)

Vtune(V

)

Port 1 Port 2 Insertio

n Loss

(dB)P1(mW

)

V1(mV

)

P1(dBm

)

P2(mW

)

V2(mV

)

P2(dBm

)

1.50 2.3 3.40 409.26 5.32 2.20 351.56 3.40 1.32

1.55 3.1 5.62 522.62 7.30 3.98 437.71 6.12 1.54

1.60 3.8 9.63 670.65 9.30 8.20 567.54 9.17 1.45

1.65 4.4 8.20 642.98 9.32 7.57 525.05 8.83 1.76

1.70 4.9 8.05 614.00 7.19 6.80 392.34 8.32 3.89

1.75 5.5 7.51 576.00 8.31 5.56 148.05 7.45 11.80

1.80 6.1 7.01 582.10 8.21 2.20 74.22 3.22 17.89

1.85 6.7 5.16 594.00 8.38 1.23 39.70 1.57 23.501.90 7.3 6.95 582.00 8.46 2.45 60.24 2.74 19.70

1.95 7.8 7.27 605.00 8.86 2.52 24.64 3.65 27.80

2.00 8.5 6.33 543.00 7.75 2.64 15.84 3.81 30.70

Sample Calculation

Insertion Loss (IL)

1

2

20log

409.26

20log 351.56

1.32

VIL

V

IL

IL dB


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BENT 4153 Page 5

Band pass Filter

Frequency

(GHz)

Vtune(V) Port 1 Port 2 Insertion

Loss

(dB)P1(mW) V1(mV) P1(dBm) P2(W) V2(mV) P2(dBm)

1.50 2.3 3.40 409.26 5.32 5.5 52.84 -12.5 17.78

1.55 3.1 5.62 522.62 7.30 7.5 20.50 -20.0 28.13

1.60 3.8 9.63 670.65 9.30 11 21.00 -20.0 30.09

1.65 4.4 8.20 642.98 9.32 11.5 23.00 -21.0 28.93

1.70 4.9 8.05 614.00 7.19 210 105.00 -6.6 15.341.75 5.5 7.51 576.00 8.31 5.3m 510.00 7.3 1.06

1.80 6.1 7.01 582.10 8.21 5m 500.00 7.1 1.32

1.85 6.7 5.16 594.00 8.38 5.3m 515.00 7.3 1.24

1.90 7.3 6.95 582.00 8.46 1m 220.00 -0.7 5.45

1.95 7.8 7.27 605.00 8.86 7 30.00 -15.0 26.09

2.00 8.5 6.33 543.00 7.75 6 21.00 -20.0 28.25

Sample Calculation

Insertion Loss (IL):

1

220log

409.2620log

52.84

17.78

V

IL V

IL

IL dB

0

5

10

15

20

2530

35

1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2

InsertionL

oss

Frequency (GHz)

Graph of Insertion Loss v/s Frequency For

Low Pass Filter


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2. Find the stop frequency of the filter from the measured values of two filters.

From the graph of frequency response, the stop frequencies for both filters are:

Low pass filter

fC= 1.7GHz

0

5

10

15

20

25

30

35

1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2

InsertionL

oss

Frequency (GHz)


Band Pass Filter

0

5

10

15

20

25

30

35

1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2

InsertionL

oss

Frequency (GHz)


Low Pass Filter


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BENT 4153 Page 7

Band pass Filter

FCL= 1.73 GHz and fCH= 1.87 GHz

3. Design a band pass filter using L and C.

With specification (Ripple = 0.5dB, Center Frequency = 1GHz Band Width = 10%, N = 3,

Impedance : 50

Designing a Bandpass Filter Using L and C

Specifications:

Ripple = 0.5dBCenter frequency = 1 GHz

Bandwitdth = 10%

N = 3

Impedance = 50

Low pass filter design

0

5

10

15

20

25

30

35

1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2

InsertionL

oss

Frequency (GHz)


Band Pass Filter


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BENT 4153 Page 8

g1= 1.5963g2= 1.0967

g3=1.5963

g4=1.000

L1 = 0.4985nH

C1 = 50.812pF

L2=87.27nH

C2= 0.29pF

L3=L1= 0.4985nH C3=C1= 50.812pF


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BENT 4153 Page 9

6.0 Discussion

1. The aim of this lab is to witness first-hand the effect of the Low-Pass Filter and

Band-Pass Filter utilizing the ED3300L and ED3300M module.

2. The Low-Pass Filter reflect/blocks the high frequency signal (above the threshold

set by the circuit). In the lab session, the amplitude of the output waveform of the

signal of the low frequency is slightly higher than the high-frequency.

3. The Band-Pass Filter blocks the signals that are out of the allowed frequency.

Only signal with the frequency between the specified range and let pass, hence

the name Band-Pass Filter. In the lab session, the results are quite obvious with

the ED3300M module. At frequency of 1.5GHz to 1.6GHz, the average dBm ~

-30 which make it a bit hard to distinguish the V-tune vale.

4. From the result, we can clearly see the insertion loss as the frequency increases

which means that the signals are reflected more and more as the following

increases. This goes along with the theoretical expectation of the Low Pass

Filter.

5. The result for the Band Pass Filter looks promising as well, at frequency 1.5GHz,

1.6GHz, 2.0GHz, the loss are high; showing that the signal are blocked. While at

1.7GHz to 1.9GHz, the loss are low indicating the signal are let thorough. The

result are as expected as the theoretical result where the filter only allow signal to

pass through at only certain frequency.


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7.0 Conclusion

At the end of the lab sessions, we are able to manage the investigate the

operation of various type of microwave filters; the Low Pass Filter and Band Pass

Filter.

8.0 Reference

[1] LAB SHEET OF RF AND MICROWAVE TECHNIQUE BENT 4153

Low Pass Filter and Band Pass Filter

[2] Band Pass Filter(n.d.). Retrieved from Princeton:

http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Band_Pass_Filter.html

[3] Giangrand, I. (n.d.). Conversions between Low-Pass Filter and Band-Pass Filter.

Retrieved from giangrandi.ch: http://www.giangrandi.ch/electronics/anttool/swr.html

[4] Bogatin, E. (2004). Signal Integrity - Simplified.New Jersey: Pearson Education Inc.

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