A list,
Short wave is defined by the International Radio Advisory Committee (CCIR, now ITU-R) as an electromagnetic wave with a wavelength of l00ml0m and a frequency of 3MHz30MHz. Radio communication using short wave is called short wave communication, also known as high frequency (HF) communication. In fact, in order to make full use of the advantages of short-wave communication, the frequency range of short-wave communication is 1.5MHz~30MHz.
Since 1921, when an accident occurs in Rome, Italy, has been found to realize long distance communication, short-wave shortwave communication rapid development, has become the world in the main measure, remote communication, is widely used in government, military, diplomatic, weather, business and other departments, to transmit telegraph, telephone, fax, low speed data and the information such as image, voice broadcast. Before the advent of satellite communication, shortwave played a unique and important role in international communication, flood control and disaster relief, maritime rescue and military communication.
Shortwave communication can be transmitted by ground wave, but mainly by sky wave.
The attenuation of ground wave propagation increases with the increase of working frequency. Under the same ground condition, the higher the frequency, the greater the attenuation. The use of ground wave is only applicable to short-range communication, and its working frequency is generally selected below 5MHz. Ground wave propagation is less affected by weather and relatively stable, and the channel parameters basically do not change with time, so the ground wave propagation channel can be regarded as a constant parameter channel.
Sky waves are the part of radio waves reflected back to the ground through the ionosphere. The propagation loss of sky wave is much smaller than that of ground wave. After many reflections (multi-hop propagation) between the ground and ionosphere, sky wave can reach a very far place. Therefore, sky wave can be used for global communication. Sky wave propagation is extremely unstable due to ionospheric variation and multipath propagation, and its channel parameters change rapidly with time, so it is called variable parameter channel. Sky wave can be used not only for long distance communication, but also for short distance communication.
In the area where the terrain is complicated and the short-wave ground wave or line-of-sight microwave is blocked, the sky wave projected by high elevation can be used to achieve communication. Compared with satellite communication, ground microwave, coaxial cable, optical cable and other means of communication, shortwave communication also has many significant advantages:
1) Shortwave communication can realize long-distance communication without establishing a relay station, so the construction and maintenance cost is low and the construction cycle is short;
2) The equipment is simple, can be fixed according to the use of requirements, fixed communication. It can also be carried or loaded into vehicles, ships and aircraft for mobile communication;
3) Easy circuit scheduling, convenient and rapid temporary networking, with great flexibility in use;
4) Strong resistance to natural disasters or wars. Communication equipment is small in size, easy to hide, easy to change the working frequency to avoid enemy interference and eavesdropping, easy to recover after damage.
These are the main reasons why shortwave communication has been preserved for a long time and is still widely used today. Shortwave communication also has some obvious disadvantages:
1) The available frequency band is narrow and the communication capacity is small. According to international regulations, each shortwave station occupies a frequency width of 3.7kHz, while the entire shortwave band is available in a frequency range of 28.5MHz. In order to avoid interference with each other, the world can only accommodate 7,700 channels of communication, so the communication space is very crowded. Moreover, the 3kHz communication bandwidth limits the communication capacity and data transmission rate to a large extent.
2) The short-wave sky wave channel is variable parameter channel, and the signal transmission stability is poor. Shortwave radio communication mainly relies on the ionosphere for long-distance signal transmission. The ionosphere as the signal reflection medium has a weakness of great variability in parameters. It is characterized by path loss, delayed walking, noise and interference, which are constantly changing with day and night, frequency and location.
On the one hand, the change of ionosphere causes the signal to decline, and the amplitude and frequency of the decline are constantly changing.
On the other hand, serious multipath effect exists in sky wave channel, which causes frequency selective fading and multipath delay. Selective fading leads to signal distortion, and multipath delay leads to time diffusion of received signals, which is the main limitation of data transmission in short wave link.
3) Serious interference from atmospheric and industrial radio noise. Along with the development of the industrial DianQiHua, short-wave radio spectrum of industrial radiation noise average intensity is high, coupled with atmospheric radio noise and radio interference, in the past, a few watts, a dozen watts transmitted power can achieve long-range shortwave radio communication, today, 10 times, several times in this power does not necessarily guarantee reliable communication. Atmospheric and industrial radio noise is mainly concentrated in the low end of the radio spectrum, and the intensity decreases with the increase of frequency. Although the noise interference in short wave band is lower than that in medium and long band, the intensity is still very high, which affects the reliability of short wave communication, especially the burst noise of pulse type, which often causes burst errors in data transmission and seriously affects the quality of communication.
These problems not only restrict the development of shortwave communication, but also can not well adapt to people’s increasing demand for data communication, especially for high-speed data communication service. When satellite communication rose in 1960s, short wave communication was seriously challenged due to its advantages of stable channel, high reliability, good communication quality and large communication capacity compared with short wave communication. Many important services of shortwave communication have been replaced by satellite communication. Investment in shortwave communication has been sharply reduced, and the status of shortwave communication has been greatly reduced. By the late 1970s, some even doubted the existence of shortwave communications.
However, practice has proved that the initial construction cost of satellite communication is high and flexibility is limited. Satellite communications, once envisioned as a possible replacement for shortwave communications, cannot meet the needs of users in all cases. In fact, not all customers need broadband lines.
In addition, in the war, satellite communications are vulnerable to enemy attack, channel is not easy to resist enemy electromagnetic interference. In contrast, shortwave communication is not only cheap and easy to implement, but also has a natural “relay system” – the ionosphere – that is not easy to “destroy”. The satellite relay system could fail or be destroyed, whereas the ionospheric relay system could only be disrupted by a high-altitude atomic explosion, which affected ionization density only for a limited period of time in the ionosphere.
In February 1980, a report by the DefenseNuclearAgency suggested that “the most promising solution for restoring communications to a nation after an atomic attack is inexpensive high-frequency communications systems that automatically find channels.”
In fact, from the late 1970s to the early 1980s, shortwave communications became a focus again. Many countries have accelerated the research and development of shortwave communication technology and introduced some new equipment and systems with excellent performance. In the comprehensive Tactical Communication plan revised in 1979, the US army highlighted the status of shortwave communication and listed it as one of the first command and control communication means. Beginning in the early 1980s, the U.S. Army implemented a series of shortwave communications improvement programs throughout the armed forces. In the Gulf War, shortwave communication was widely used by the American and French armies and achieved outstanding results. In recent years, the militaries of some other countries also regard shortwave communication as one of the important means of communication.
In addition, in some fields of civil communication, the application of shortwave communication also has a developing trend. Especially in recent years, due to a variety of the application of new technology, short-wave communication technology and equipment has made great progress, the short-wave communication the shortcoming of the original, has quite a few has been overcome, greatly improve the quality of the short-wave communication link, both telephone transmission and data transmission quality can be compared with satellite communication, the short-wave communication is back to glow the youth.
function varargout = SW(varargin)
% SW M-file for SW.fig
% SW, by itself, creates a new SW or raises the existing
% singleton*.
%
% H = SW returns the handle to a new SW or the handle to
% the existing singleton*.
%
% SW('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in SW.M with the given input arguments.
%
% SW('Property','Value',...) creates a new SW or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before SW_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to SW_OpeningFcn via varargin.
%
% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one
% instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES
% Edit the above text to modify the response to help SW
% Last Modified by GUIDE v2.5 26-Jul-2015 17:13:01
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @SW_OpeningFcn, ...
'gui_OutputFcn', @SW_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin && ischar(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT
% --- Executes just before SW is made visible.
function SW_OpeningFcn(hObject, eventdata, handles, varargin)
set(handles.run,'enable','off');
set(handles.sendsignal,'enable','off');
set(handles.receivesignal,'enable','off');
set(handles.axes1,'visible','off');
set(handles.axes2,'visible','off');
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to SW (see VARARGIN)
% Choose default command line output for SW
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes SW wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = SW_OutputFcn(hObject, eventdata, handles)
% varargout cell array for returning output args (see VARARGOUT);
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;
% --- Executes on button press in selectfile.
function selectfile_Callback(hObject, eventdata, handles)
%FilterSpec={'*.wav','*.wma'};
FilterSpec=('*.wav');
[fname,pname]=uigetfile(FilterSpec,'选择音频文件');
sourceFile=strcat(pname,fname);
set(handles.soucepath,'String',sourceFile);
[source,samplefs] = wavread(fname);
[m2,d2]=wavfinfo(fname);
%title('原始语音信号时域波形');?
%xlabel('时间轴');?
%ylabel('幅值?A');
handles.source = source;
handles.samplefs = samplefs;
guidata(hObject,handles);
set(handles.run,'enable','on','Backgroundcolor',[0 1 0]);
set(handles.sendsignal,'enable','on','Backgroundcolor',[0 1 0 ]);
set(handles.receivesignal,'enable','off');
set(handles.axes1,'visible','Off');
set(handles.axes2,'visible','Off');
% hObject handle to selectfile (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
function soucepath_Callback(hObject, eventdata, handles)
%cd (get(handles.soucepath,'string'));
%load_listbox(pwd,handles);
% hObject handle to soucepath (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of soucepath as text
% str2double(get(hObject,'String')) returns contents of soucepath as a double
% --- Executes during object creation, after setting all properties.
function soucepath_CreateFcn(hObject, eventdata, handles)
% hObject handle to soucepath (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
% --- Executes on selection change in modulationtype.
function modulationtype_Callback(hObject, eventdata, handles)
switch get(handles.modulationtype,'value')
case 1
set(handles.modparm_txt,'String','调制指数:','Visible','on');
set(handles.modparm,'Visible','on','String','0.2');
set(handles.text13,'Visible','on');
set(handles.demodmethod,'Style','popupmenu','string',{'相干解调 ','包络检波'});
case 2
set(handles.modparm_txt,'Visible','off');
set(handles.modparm,'Visible','off');
set(handles.text13,'Visible','off');
set(handles.demodmethod,'Style','edit','string','相干解调');
case 3
set(handles.modparm_txt,'String','最大频偏:','Visible','on');
set(handles.text13,'Visible','off');
set(handles.modparm,'Visible','on','String','80000');
set(handles.demodmethod,'Style','edit','string','相干解调');
end
% hObject handle to modulationtype (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: contents = get(hObject,'String') returns modulationtype contents as cell array
% contents{get(hObject,'Value')} returns selected item from modulationtype
% --- Executes during object creation, after setting all properties.
function modulationtype_CreateFcn(hObject, eventdata, handles)
% hObject handle to modulationtype (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: popupmenu controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function modparm_Callback(hObject, eventdata, handles)
modparm = str2double(get(handles.modparm,'String'));
if modparm>1
errordlg('调制指数不能超过1','错误');
return
end
% hObject handle to modparm (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of modparm as text
% str2double(get(hObject,'String')) returns contents of modparm as a double
% --- Executes during object creation, after setting all properties.
function modparm_CreateFcn(hObject, eventdata, handles)
% hObject handle to modparm (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function minfreq_Callback(hObject, eventdata, handles)
% hObject handle to minfreq (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of minfreq as text
% str2double(get(hObject,'String')) returns contents of minfreq as a double
% --- Executes during object creation, after setting all properties.
function minfreq_CreateFcn(hObject, eventdata, handles)
% hObject handle to minfreq (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function maxfreq_Callback(hObject, eventdata, handles)
% hObject handle to maxfreq (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of maxfreq as text
% str2double(get(hObject,'String')) returns contents of maxfreq as a double
% --- Executes during object creation, after setting all properties.
function maxfreq_CreateFcn(hObject, eventdata, handles)
% hObject handle to maxfreq (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function upsamplefactor_Callback(hObject, eventdata, handles)
% hObject handle to upsamplefactor (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of upsamplefactor as text
% str2double(get(hObject,'String')) returns contents of upsamplefactor as a double
% --- Executes during object creation, after setting all properties.
function upsamplefactor_CreateFcn(hObject, eventdata, handles)
% hObject handle to upsamplefactor (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function fc_Callback(hObject, eventdata, handles)
fc = str2double(get(handles.fc,'String'));
if fc<1.6||fc>30
errordlg('请将载波频率设置在1.6MHz至30MHz之间','错误');
return
end
% hObject handle to fc (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of fc as text
% str2double(get(hObject,'String')) returns contents of fc as a double
% --- Executes during object creation, after setting all properties.
function fc_CreateFcn(hObject, eventdata, handles)
% hObject handle to fc (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
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Ii. Source code
3. Operation results
Fourth, note
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