Characterization of a
Transmitter-Receiver System
Report for Introductory Laboratory Course Physics, Part I
Felix Wedemann and Leon Bösche
felix.wedemann@uni-oldenburg.de ; leon.boesche@uni-oldenburg.de
Group 3
December 6, 2022
0.Table of Content
1. Introduction
2. Experiments
2.1 Set-Up of Transmitter and Receiver
2.1.1 Method
2.1.2 Result
2.2 Distance Dependence
2.2.1 Method
2.2.2 Result
2.2.3 Discussion
2.3 Directional Characteristics
2.3.1 Method
2.3.2 Result
1
1
2-3
2
3
3-5
3
3
5
5-8
5
6
2.4 Refraction
2.5 Polarization
2.5.1 Method
2.5.2 Result
2.5.3 Discussion
2.5.4 Question 1
2.6.3 Reflection
2.6.1 Method
2.6.2 Reflection at a Metal Plate and Wire Grid (Results)
2.6.3 Discussion
2.6.4 Question 2
3. Appendix
8-10
8
9
9
10
10-13
10
10
13
13
14
1
1. Introduction
In this set of Experiments we are introduced to the system and the Relation between
a transmitter and the receiver. Added to that we want to see how changes in different
ways take an influence on the relation between them. Therefore we change for e.g
the Distance, the angle or place a reflection plate between them. Furthermore we
want to see with those experiments how microwaves behave under different
circumstances. We also get to know the law of reflection and the index of reflection,
as well as how microwaves are polarized.
2. Experiments
Equipment:
Microwave transmitter (Type I with Gunn diode MICROSEMI MO86751A, P 10 mW, 28.5 mm; type
II with Gunn diode CL 8650 8927 (unknown manufacturer), P 15 mW,
27.5 mm), microwave
receiver (HEWLETT-PACKARD X424A), 2 triangular rails (lengths 1.5 m and 0.5 m), joint for
triangular rails with angle scale indicator, angle-sensor (TWK ELEKTRONIK PBA 12), 3 power
supplies (PHYWE (0 – 15 / 0 – 30) V), multimeter (AGILENT U1272A or U1251B), digital oscilloscope
TEKTRONIX TDS 1012 / 1012B / 2012C / TBS 1102B - EDU, PVC plate, metal plate, wire grid,
transition stage (length 100 mm) with motor and laser distance sensor (BAUMER OADM
12U6460/S35), 2 impedance converters, PC with DAQ device (NATIONAL INSTRUMENTS myDAQ)
and BNC-adapter box, metal measuring tape (length 1 m), stand material.
2
2.1
Set-Up of Transmitter and Receiver
2.1.1 Method
For this experiment we need to set it up like shown in Fig. 1 and we need to make
sure that we neatly set up the transmitter and the receiver.
Fig. 1 - Initial setup for measuring the intensity of a microwave
The transmitter and the receiver are assembled on a 1.5m long triangular rail and
they need to be adjusted at the same height and angle, but 5cm apart from each
other. The distance we have to consider is the one between the edges of both horns
from the transmitter and the receiver. The Transmitter has to be connected to a DC
power supply, with the output of 10V, which we have to check with our multimeter.
Fig. 2 - Showing the Connection, from the Receiver to the Oscilloscope and Function Generator to the
Transmitter
3
The receiver on the other hand is connected to an oscilloscope, so that we can
measure the intensity I, which is defined by the average energy of a wave per time
and area. We have to keep in mind that the Intensity will be put out in a negative
voltage from our receiver.
Fig. 3 - Sketch of the Set-up for our first Experiment [1]
2.1.2 Result
For the initial set-up of the experiment we measure a voltage of 10.02 V with our
multimeter.
2.2
Distance Dependence
2.2.1 Method
For this Experiment we use the same set-up as in 2.1 (Fig. 1). But in comparison we
now measure multiple times to get a relation between the distance d and the Voltage
U. For this we measure the Voltage for every step on the x axis so every
5,7cm(beach use we used Transmitter type 1). We need to measure a few times to
get a precise relation. Furthermore we have to measure until around 1m for the max
distance so 5cm<d<1m.
2.2.2 Result
The results are based on the distance d between the edges of the horns from our
transmitter and our receiver.
Distance
d in cm
(+/- 0.5)
0
5,7
11,4
17,1
22,8
28,5
39,9
51,3
85,5
102,6
Voltage U
in mV
-627
-543
-468
-392
-324
-272
-208
-152
-80
-56
Tab. 1 - Results of the Experiment Voltage U in mV depending on to Distance d in cm
4
We can observe that the voltage is rising the further we move the receiver apart from
the transmitter, so the negative value is getting smaller. This means that the Intensity
is decreasing.
Added to that, the measured voltage rises at a significant speed first. This increase
slows down the further away the receiver is from the transmitter.
Fig. 4 - | U | plotted over d in a semi-log plot
5
Fig. 5 - | U | plotted over d in a double logarithmic plot
2.2.3 Discussion
We can observe in our plotted graphs (Fig.X&X) that the progression of the curve
which shows U in mV is logarithmic and is decreasing. If we increase the distance
between transmitter and receiver the curve is even decreasing faster. In our case the
value is going closer to zero because we had negative value so the voltage is
actually increasing, when we increase the distance between transmitter and receiver.
2.3 Directional Characteristics
2.3.1 Method
In this experiment we try to find out how the directional characteristics are taking an
influence on the signal the transmitter provides to the receiver. Therefore we place
our Transmitter on top of the rotational axis and our receiver on the right side of the
track so that we have a distance of 40cm between them on the second trail (0,5m
length).
6
Fig. 6 - Set-up of Transmitter and Receiver with Angle Sensor
Moreover we connected our DAQ with the angle sensor and the Receiver, so that we
can visualize the measured data later on and calculate with them.
For our measurements we can read off the angle from the angular scale (180° when
it is aligned with the axis).
By rotation of the extend axis, we can measure the change of the voltage U while
increasing the angle from 150° to 210°
2.3.2 Result
We measured the voltage U in V for every step of 10° so that we can observe the
dependence of the angle on the voltage. The starting voltage of our angle sensor is
4.98 V. The measured voltages must be added onto that, to give us accurate results.
Angle α
in (°)
150
160
170
180
190
200
210
Voltage
U in V
0.296
0.491
0.711
0.917
1.129
1.339
1.587
Tab. 2 - Measurements for the Voltage U in mV in dependence to the Angle α in °
For our error we have to consider that the angle was read off the scalar on the angle
sensor by eye so it could differ by (+/- 1°). For the voltage we do not consider an
error from our Oscilloscope but the relation between U and α might change as a
result of the error for the angle
7
Fig. 7 - Measurements of the DAQ for the angle sensor (red) and receiver (black)
Now a linear regression can be calculated by using the voltage provided by the angle
sensor. V(150°) = 0.296 V and V(210°) = 1.587 V.
Therefore the calibration curve of the angle sensor is as follows:
α(V) = 46.476 ° * V + 136.243 °
Now the voltage values can be calculated into angles and plot into a polar diagram
(Fig. 8).
8
Fig. 8 - Voltage of the angle sensor plot into a polar diagram including theoretical values for spherical
wave and strongly restricted ray
In Fig. 8 we can see that the receiver acquires the highest values at an angle of 180°
and that the intensity declines quickly after increasing the angle above or below 184°
and 176° respectively.
Measuring the highest intensity at 180° was just as expected because the transmitter
and the receiver are perfectly aligned at that angle. What we did not expect was
such a fast dropoff at increasing angles.
2.5 Polarization
2.5.1 Method
For this experiment, the transmitter (S) and the receiver (E) are mounted at a
distance of around 5 cm (we decided to go for 5.1 cm since we measured the lowest
voltage at that specific distance) and the voltage U is measured. Then a wire grid is
placed either horizontally or vertically between the two devices and the resulting
voltage is measured.
9
We expect to see a significant decline in voltage | U | for one of the alignments and a
less significant reduction for the other alignment.
2.5.2 Results
We first measured the voltage for a distance of 5.1 cm between S and E without any
obstacle between them. Our initial voltage U0 therefore is -620 mV.
U0 = -620 mV
We then placed the wire grid horizontally between S and E without changing the
distance. For this alignment we measured a voltage Uh of -530 mV.
Uh = -530 mV
For the last measurement, the wire grid was placed vertically between S and E.
Again, without changing the distance. The measured voltage Uv comes down to -40
mV.
Uv = -40 mV.
2.5.3 Discussion
Initial voltage:
U0 = -620 mV
Horizontal alignment:
Uh = -530 mV
Vertical alignment:
Uv = -40 mV.
Our results are just as expected. The initial voltage without any obstacle is the
lowest. This means the signal is the strongest. With the wire grid placed horizontally
between S and E, the voltage rises to -530 mV which means that the signal is a bit
weaker. With the vertical alignment, the measured voltage amounts to -40 mV.
This is due to the electric field of the microwave beam, which only oscillates in one
direction. This direction is either horizontally or vertically. When an obstacle is now
placed in front of the wave, it can be affected in its intensity.
10
2.5.3 Question 1
In our case, the microwave beam of the transmitter is surely oscillating vertically
since the measured voltage with a wire grid placed vertically between S and E
reduces the measured voltage to an extreme extent. The wave therefore is linearly
polarized in a vertical direction.
2.6
Reflection
2.6.1 Method
For our last experiment, we measure the reflection of a microwave at a metal plate
and at a wire grid. To do that, S and E are mounted at a distance of about 20 cm
from the rotation axis. Then a metal plate (MP) or a wire grid (WG) is placed in the
middle onto the rotation axis D. Now the resulting voltage at the receiver is
measured for different angles between the transmitter and the metal plate / wire grid.
Fig. 9 - Set-up to measure the reflection at a metal plate [1]
2.6.2 Reflection at a Metal Plate and Wire Grid (Results)
The experiment is first set-up according to Fig. X and the voltages for different
angles are measured. This procedure is repeated with a set-up according to Fig. X.
11
Fig. 10 and 11 - Experimental setup to measure the reflection of a microwave at a metal plate and
wire grid
The resulting measurements can be seen in Tab. X. We decided to take an error of
+/- 0.1° for the angles since it was nearly impossible to perfectly read a value.
Angle γ
in °
35
38
41
44
47
50
53
56
Voltage
U in mV
(MP)
-159
-199
-202
-233
-224
-200
-170
-120
Voltage
U in mV
(WG)
-157
-200
-200
-200
-200
-197
-120
-80
Tab. 3 - Resulting voltages for different angles between MP and S
To further analyze a relation between | U | and γ, | U | is plotted over γ. The results
can be seen in Fig. X for the MP and X for the WG.
12
Fig. 12 - | U | plotted over γ (MP)
With the help of the generated function and data analysis of ORIGIN we can see that
the maximum is reached at about (44.39 +/- 0.07)°.
Therefore the highest measured voltage with the MP is reached at (44.39 +/- 0.07)°.
Fig. 13 - | U | plotted over γ (WG)
13
For the wire grid (Fig. X) the polynomial fit shows us a maximum voltage at an angle
of (43.16 +/- 0.06)°.
2.6.3 Discussion
Maximum voltage MP:
(44.39 +/- 0.07)°
Maximum voltage WG:
(43.16 +/- 0.06)°
Our measured maxima are fairly close to the expected maximum. Since we believe
in
the law of reflection, we would have guessed that the maximum voltage is
reached at an angle of around 45° resulting in an angle of incidence equal to the
angle of reflection. The measured voltage while using the WG seems a bit off since
the same voltage of 0.2 V was measured for an angle of 38° up to 47°. We repeated
our testing but were not able to measure anything different. These odd numbers
result in an angle for the maximum voltage that is quite a bit off from the expected
value but not to such an extent that it has to be deemed as significant.
2.6.4 Question 2
Since our calculated values of (43.16 +/- 0.06)° and (44.39 +/- 0.07)° are fairly close
to 45° we think it is still valid to say that the law of reflection is true.
14
3. Appendix
Reference
[1] Introductory Laboratory Course Physics. Carl von Ossietzky University
Oldenburg, Oktober 2019
Measurement Tables