... various
services such as voice mail, email, video, messaging, data, and computer on-line
services. The direct link between satellites and personal communication systems can
provide voice, video, ... Chapter 2 reviews some fundamental
principles of transmission lines and electromagnetic waves. Chapter 3 gives a brief
overview of how antennas and antenna arrays work. Chapter 4 provides a discussion
FIGURE ... (DBS) systems have offered an
alternative to cable television, and the end of the Cold War has made many military
technologies available to civilian applications. The global positioning systems
(GPSs),...
... axis.
The Smith chart can be used to ®nd (1) G
L
from Z
L
and vice-versa; (2)
Z
in
from
Z
L
and vice-versa; (3) Z from Y and vice-versa; (4) the VSWR; and (5) d
min
and
d
max
. The Smith ... normalized values.
2. Moving away from the load (i.e., toward the generator) corresponds to
moving in a clockwise direction.
3. A complete revolution around the chart is made by moving a distance
l ... degree of
accuracy, by dividing P
2
by P
1
, ®nding the logarithm of the result, and multiplying it
by 10.
FIGURE 2.11 Transmission line connected to an open load.
28
REVIEW OF WAVES AND TRANSMISSION...
... or microwave power.
It is a reciprocal device, and the same antenna can serve as a receiving or
transmitting device. Antennas are structures that provide transitions between
guided and free-space ... the HPBW
and SLLs. Also shown is FNBW, the first-null beamwidth.
3.5.5 Directivity, Gain, and Efficiency
The directivity D
max
is defined as the value of the directive gain in the direction of its
maximum ... Þ¼
1
2
Re½
~
EE Â
~
HH*.
The directivity of an isotropic antenna equals to 1 by definition, and that of other
antennas will be greater than 1. Thus, the directivity serves as a figure of merit
relating...
... capacitances. Active filters can be built
by using active devices such as MESFETs in microwave frequencies and CMOS in
RF. The active devices provide negative resistance and compensate for the losses ... biasing field.
Ferrite control devices are heavy, slow, and expensive. Solid-state control devices, on
the other hand, are small, fast, and inexpensive. The ferrite devices do have some
advantages ... the
comparison between ferrite and p
i n diode control devices [1]. It should be
mentioned that the use of FETs or transistors as control devices could provide gain
instead of loss.
Switches are widely...
... dBm
FIGURE 5.13 Third-order intermodulation.
164
RECEIVER SYSTEM PARAMETERS
2. Selectivity. Receiver selectivity is the ability to reject unwanted signals on
adjacent channel frequencies. This ... sensitivity of the receiver. In order for a signal to be detected, it should have
a strength much greater than the noise floor of the system. Noise sources in
thermionic and solid-state devices ... the equivalent noise
temperature in kelvin, (d) the minimum detectable signal (MDS) in dBm at
input port, and (e) the input IP3 power level in dBm. The individual
component system parameters are...
... the reference frequency can also be divided before it is connected to the
phase detector. This scheme is shown in Fig. 6.20. A fixed frequency divider with
division ratio of N
2
is introduced between ... to
heating of a solid-state device.
Some of these characteristics can be found in an example given in Table 6.1.
6.2 TRANSMITTER NOISE
Since the oscillator is a nonlinear device, the noise voltages ... high-Q
circuits to build the oscillators (examples are waveguide cavities, dielectric resona-
tors, or superconducting resonators=cavities); (2) temperature compensation circuits;
or (3) phase-locked...
... receiving. A duplexer
is used to separate the transmitting and receiving signals. A circulator is shown in
Fig. 7.2 as a duplexer. A switch can also be used, since transmitting and receiving ... f
d
ð7:34Þ
FIGURE 7.17 Waveform for a moving target: (a) stationary target waveform for compar-
ison; (b) waveform for a target moving toward radar; (c) beat signal from a target moving
toward radar.
7.7 FREQUENCY-MODULATED ... introduction and overview of radar systems are given.
7.2 RADAR EQUATION
The radar equation gives the range in terms of the characteristics of the transmitter,
receiver, antenna, target, and environment...
... À1dB
Space loss
dB
Atmospheric loss À2dB
Polarization loss À1dB
Receiving feed loss À2dB
Receiving antenna gain 35 dB
Receiving antenna pointing error
þÞ À1dB
REFERENCES
1. E. A. Wolff and R. ... picture of this vision [8]. The
WLAN is for wireless indoor radio communication services or high-data-rate
communications. The system employs a central microcell hub (base station) that
services cordless ... À1dB
Space loss
dB
Atmospheric loss À2dB
Polarization loss À0:5dB
Receiving feed loss À1dB
Receiving antenna gain 20 dB
Receiving antenna pointing error
þÞ À1dB
8.8 A microwave link is set up to...
... time-sharing transmission is called time division
multiplexing.
3. The message is represented by a coded group of digital pulses. The effects of
random noise can be virtually eliminated.
TABLE 9.1 Modulation ... Japanese
digital cellular time division multiple access (TDMA) radio standard; it has high
power efficiency and spectral efficiency. In power-efficient, nonlinearly amplified
(NLA) environments, where fully ... 2pf
m
tÞtð9:7Þ
The maximum frequency swing occurs when sin 2pf
m
t ¼Æ1. Here Df is the
frequency deviation, which is the maximum change in frequency the modulated
signal undergoes. The amplitude...
... wireless
communications are frequency division multiple access (FDMA), time division
multiple access (TDMA), and code division multiple access (CDMA). Frequency
division multiple access and TDMA are ... caused by intermodulation and sideband
distortion.
10.3 TIME DIVISION MULTIPLE ACCESS AND TIME DIVISION
MULTIPLEXING
A TDMA or time division multiplexing (TDM) system uses a single frequency band
to ... transmitter; (b) TDM of two signals; (c) data
slot allocation for N signals.
10.3 TIME DIVISION MULTIPLE ACCESS AND TIME DIVISION MULTIPLEXING 297
3. Time hopping
4. Chirp
Figure 10.5a shows an example...
... applications: for example, mapping road networks, land and
aviation scenarios, analyzing urban growth, and improving aviation and
marine services.
4. Military applications: for example, surveillance, ... typical
radio navigation systems are shown in Table 11.1 for comparison. The Omega
FIGURE 11.1 Active radio navigation system.
FIGURE 11.2 Passive radio navigation system.
11.1 RADIO NAVIGATION AND ... divided into three major activities: electro-
nic support measure (ESM), electronic countermeasures (ECMs), and electronic
counter-countermeasures (ECCMs). Figure 11.14 summarizes these activities...
... bằng lòvisóng thôi cũng không tốt, vìsóng viba
của lòvisóng tác động đến các tế bào chất của thực phẩm, làm biến chất
thực phẩm và lâu dài gây tác hại cho người ăn thực phẩm đó.
Không ... phá hủy chất dinh dưỡng hay do lòvisóng làm cho
thực thẩm mất an toàn là khôngcócơ sở. Mặc dù lòvisóng - cũng như mọi
Vi c đun nấu sẽ làm giảm bớt hàm lượng vitamin trong thực phẩm ở một ... cũng không ít người lo
ngại về tác dụng của lòvisóng đối với thực phẩm. Tuy nhiên, TS Kristin
Hendrickson, ngành hóa sinh, Đại học Bang Arizona (Mỹ) cho rằng, lo ngại
về vi c sóng viba có...
...
Còn nếu không thích thì măm măm luôn thôi!
Đã có cách làm brownie bằng lòvisóng rồi đây!
Một loại bánh với hương thơm thật quyến rũ của chocolate… và chỉ mất 6’ cho vi c
nướng bánh...
... Nếu chiếc lòvisóng nhà bạn chỉ để hâm nóng thức ăn thì có lẽ bạn đã
hơi xem thường “năng lực” của “anh bạn” bếp núc này rồi. Có ti tỉ cách
chế biến món ăn với chiếc lò giản dị này, ... cho lòvisóng (thêm chút
muối nếu muốn). Bật lò ở mức cao
nhất, nấu trong 15-18 phút cho đến
khi cơm dẻo đều. Ảnh: Real Simple.
Bắp nguyên trái lột sạch vỏ, đặt
trong đĩa viba. Bật lò ... đĩa
chuyên dụng cho lòvi sóng. Lò bật
ở mức cao nhất, nấu chín trong 4-5
phút đến khi thịt chín kỹ hoàn toàn.
Ảnh: Real Simple.
Đun chảy sô-cô-la trong 30 giây, lò
bật ở mức cao. Ảnh:...