[試題] 103-2 吳宗霖 微波系統導論 期中考
課程名稱︰微波系統導論
課程性質︰選修(含複選必修)
課程教師︰吳宗霖
開課學院：電機資訊學院
開課系所︰電機工程學系
考試日期（年月日）︰104.4.21
考試時限（分鐘）：130分鐘
試題 :
Microwave and RF Design of Wireless System - Midterm
There are 6 problems, with 20 points for each, total 120 points.
---------
Problem 1
---------
A lossless transmission line with characteristic impedance Z_0 and propagation
delay T can be modeled as a lumped element circuit in term of π-model as shown
in Fig.1.
(1)Please derive the transmission (ABCD) matrix for the transmission line.[8%]
(2)Please derive the transmission (ABCD) matrix for the equivalent circuit.[8%]
(3)Please apply Taylor series and compare your answer for (1) and (2). Then
express the equivalent L and C in terms of Z_0 and T.[4%]
http://i.imgur.com/30aFX9f.jpg
---------
Problem 2
---------
(1)For the two-element cascaded circuit shown in Fig.2, prove that the overall
noise factor F = F_1 + (F_2－1)/G_1.[10%]
http://i.imgur.com/1EnDqfv.jpg
(2)Calculate the overall noise figure and gain in decibels for the system (at
room temperature,290K) shown in Fig.3. The Boltzmann coefficient k = 1.38 x
10^-23.[10%]
http://i.imgur.com/USSFAV1.jpg
---------
Problem 3
---------
Fig.4 describes the relationship between input power and output power of signal
with radius frequency ω_1 and 2ω_1－ω_2, respectively, for an amplifier.
(1)Please write down the definition of "1dB compression point (P_1dB)" and mark
it in Fig.4.[4%]
(2)Please write down the definition of "third-order intercept point (P_3)" and
mark it in Fig.4.[4%]
(3)Please write down the definition of "linear dynamic range (DR_l)" and mark
it in Fig.4.[4%]
(4)Please write down the definition of "spurious-free dynamic range (DR_f)" and
mark it in Fig.4.[4%]
(5)Please derive the formula of DR_f in terms of P_3 and noise level N_0.[4%]
http://i.imgur.com/LWnYIe4.jpg
---------
Problem 4
---------
(1)Please derive the Friis equation that describe the relationship between
transmitting power P_t and receiving power P_r for a wireless transmission
system. Assume that the transmitting and receiving antenna are with gain of
G_t, G_r, respectively, and are placed in a distance R. The wavelength of
the transmitted signal is λ.[10%]
(2)A satellite orbitting 50,000 km above the earth has an antenna with gain of
40 dB and left-hand circular polarization (LHCP). If the receiving station
on earth has an antenna with radiation efficiency of 0.8, far-zone electic
field pattern of F=(cosθ)^2, polarization factor of 0.8e_R + 0.6e_L, where
e_R is the unit vector for right-hand circular polarization (RHCP), and e_L
is the unit vector for LHCP. Find the minimum required transmitted power if
the received power should be larger than -120dBm. Assume that the main beams
of these two antennas are directed to one another, and that operating fre-
quency is 20 GHz. Ignore the propagation loss effect.[10%]
---------
Problem 5
---------
Consider the receiver system with an antenna shown in Fig.5. The radiated sig-
nal from θ= 0 degree at frequency of 1000 MHz is at such a power level S_i=
-150 dBm if received by an antenna on Earth whose gain is 0dB. Now the antenna
of this system has a gain G_A and background temperature T_B as shown below.
The amplifier has a gain G=10dB and noise figure F=3dB while the transmission
line has a loss L=6dB. The bandwidth of signal B is 1 kHz.
(1)Find the noise temperature T_A of the antenna.[10%]
(2)Find the carrier-to-noise ratio (C/N).[10%]
http://i.imgur.com/Q0o7j1X.jpg
---------
Problem 6
---------
In a RF system, mixer (shown in Fig.6) is a non-linear component to convert the
signal frequency. There are three ports in a mixer, IF, LO, and RF. The RF sig-
nal is the multiplication of IF and LO signals. For example, a 6 GHz IF signal
and a 32 GHz LO signal can lead to 26 GHz and 38 GHz RF signals. Conversion
loss is the power transfer efficiency from IF to RF. For example, if 38 GHz is
the desired signal, the conversion loss is the power ratio of 38 GHz RF signal
and 6 GHz IF signal in dB. LO-RF isolation is the power leakage from LO to RF
port measured in dB.
http://i.imgur.com/jgjf8yi.jpg
Fig.7 is a RF transmitting system. The IF signal is at 6 GHz and with a power
of -10 dBm. The LO frequency is 32 GHz and the desired RF frequency is 38 GHz.
The conversion loss of the mixer is 5 dB and LO-RF isolation is -20 dB.
http://i.imgur.com/NNliecC.jpg
We hope the output power is larger than +22 dBm and the undesired tones should
be at least 20 dB lower than the main signal (please referred to Fig.8). The
PA2 can offer 20 dB gain from 25 GHz to 40 GHz.
http://i.imgur.com/AhHZrkA.jpg
Please design a filter of this system by using Appendix and Fig.8. Assume the
system reference impedance is 50Ω.
(1)Specify which kind of filter should be used.(LPF,HPF,BPF,or BSF)[5%]
(2)Specify the minimum order of the filter and explain the reason.[5%]
(3)Draw the filter with all the parameters on it.[10%]
http://i.imgur.com/oT4f9n5.jpg
--
※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 114.43.174.221
※ 文章網址: https://www.ptt.cc/bbs/NTU-Exam/M.1431005190.A.7DA.html