VHDL編寫的4選一數據選擇器
entity mux41a is
port(a,b:in
std_logic;
s1,s2,s3,s4:in std_logic;
y:
out std_logic);
end entity mux41a;
architecture one of mux41a is
signal ab:std_logic_vector(1 downto 0);
Mobile communication devices like smart phones or tablet PCs enable us to
consume information at every location and at every time. The rapid development
of new applications and new services and the demand to access data in real time
create an increasing throughput demand. The data have to be transmitted reliably
to ensure the desired quality of service. Furthermore, an improved utilization of
the bandwidth is desired to reduce the cost of transmission.
This work titled A Digital Phase Locked Loop based Signal and Symbol Recovery
System for Wireless Channel is intended to serve as a document covering funda-
mental concepts and application details related to the design of digital phase locked
loop (DPLL) and its importance in wireless communication. It documents some
of the work done during the last few years covering rudimentary design issues,
complex implementations, and fixing configuration for a range of wireless propa-
gation conditions.
The design and manufacturing of wireless radio frequency (RF) transceivers has developed rapidly in recent ten
yeas due to rapid development of RF integrated circuits and the evolution of high-speed digital signal
processors (DSP). Such high speed signal processors, in conjunction with the development of high resolution
analog to digital converters and digital to analog converters, has made it possible for RF designers to digitize
higher intermediate frequencies, thus reducing the RF section and enhancing the overall performance of the RF
section.
The objective of this book is to allow the reader to predict the received
signal power produced by a particular radio transmitter. The first two
chapters examine propagation in free space for point-to-point and
point-to-area transmission, respectively. This is combined with a dis-
cussion regarding the characteristics of antennas for various purposes. In
chapter 3, the effect of obstacles, whether buildings or mountains, is
discussed and analytical methods, whereby the strength of a signal is the
shadow of an obstacle can be predicted, are presented.
OSCILLATORS are key building blocks in integrated transceivers. In wired and
wireless communication terminals, the receiver front-end selects, amplifies and
converts the desired high-frequency signal to baseband. At baseband the signal can
then be converted into the digital domain for further data processing and demodula-
tion. The transmitter front-end converts an analog baseband signal to a suitable high-
frequency signal that can be transmitted over the wired or wireless channel.
In order to improve the spectral efficiency in wireless communications, multiple
antennas are employed at both transmitter and receiver sides, where the resulting
system is referred to as the multiple-input multiple-output (MIMO) system. In
MIMO systems, it is usually requiredto detect signals jointly as multiple signals are
transmitted through multiple signal paths between the transmitter and the receiver.
This joint detection becomes the MIMO detection.
Nature is seldom kind. One of the most appealing uses for radio-
telephone systems—communication with people on the move—must over-
come radio transmission problems so difficult they challenge the imagina-
tion. A microwave radio signal transmitted between a fixed base station
and a moving vehicle in a typical urban environment exhibits extreme
variations in both amplitude and apparent frequency.
