ask_help_begin
DDEMOD M-ary amplitude shift keying (ASK) demodulation.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M), METHOD = 'ask', demodulates a ASK
       modulated signal with carrier frequency Fc (Hz), digital message sample
       frequency Fd (Hz), and simulation sample frequency Fs (Hz). This
       function requires that Fs > Fd and Fs/Fd be a positive integers. When
       Fd is a two element vector, the second element is the offset value for
       the decision point. The offset should be an integer. The offset timing
       is Fd(2)/Fs. The default offset is zero. The M-ary number for the
       ASK is M. The demodulated digital messages are in range [0, M-1]. A
       default lowpass filter [NUM, DEN]=BUTTER(5,Fc*2/Fs) is used as
       demodulation lowpass filter.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, NUM, DEN), METHOD = 'ask',
       specifies the numerator (NUM) and denominator (DEN) of a lowpass
       filter in the demodulation. The sample time for the filter is 1/Fs.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, ...), METHOD = 'ask/costas',
       specifies the Costas loop in the demodulation.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, ...), METHOD = 'ask/eye', plots 
       eye-pattern diagram before demapping.

       The constellation of the ASK can be plotted by using DMOD('ask', M).
ask_help_end

psk_help_begin
DDEMOD M-ary phase shift keying (PSK) demodulation.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M), METHOD = 'psk', demodulates a PSK
       modulated signal with carrier frequency Fc (Hz), digital message sample
       frequency Fd (Hz), and simulation sample frequency Fs (Hz). This
       function requires that Fs > Fd and Fs/Fd be positive integers.
       When Fd is a two element vector, the second element is the offset value
       for the decision point. The offset should be an integer. The offset
       timing is Fd(2)/Fs. The default offset is zero. The M-ary number
       for the PSK is M. The demodulated digital messages are in range 
       [0, M-1]. A default lowpass filter [NUM, DEN]=BUTTER(5,Fc*2/Fs) is used
       as demodulation lowpass filter.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, NUM, DEN), METHOD = 'psk', 
       specifies the numerator (NUM) and denominator (DEN) of a lowpass filter
       in the demodulation. The sample time for the filter is 1/Fs.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, ...), METHOD = 'psk/eye', plots 
       eye-pattern diagram before demapping.

       The constellation of the PSK can be plotted by using DMOD('psk', M).
psk_help_end

qask_help_begin
DDEMOD M-ary quadrature amplitude shift keying demodulation.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M), METHOD = 'qask', demodulates a
       QASK modulated signal with carrier frequency Fc (Hz), digital message
       sample frequency Fd (Hz) and simulation sample frequency Fs (Hz). This
       function requires that Fs > Fd and Fs/Fd be positive integers. When
       Fd is a two element vector, the second element is the offset value for
       the decision point. The offset should be an integer. The offset timing
       is Fd(2)/Fs. The default offset is zero. The M-ary number for the
       square form QASK is M. The demodulated digital messages are in range
       [0, M-1]. A default lowpass filter [NUM, DEN]=BUTTER(5,Fc*2/Fs) is used
       as demodulation lowpass filter. The output of this function is a matrix
       with the odd number column being the in-phase component of the 
       demodulated message signal and the even number column being the 
       quadrature component of the demodulated signal.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, NUM, DEN), METHOD = 'qask',
       specifies the numerator (NUM) and denominator (DEN) of a lowpass
       filter in the demodulation. The sample time for the filter is 1/Fs.
       The constellation of the PSK can be plotted by using DMOD('qask', M).

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, In_Phase, Quad), METHOD = 'qask/arb'
       demodulates the modulated signal Y using the QASK method with arbitrary
       constellation. The arbitrary constellation is defined in the variables
       In_Phase and Quad. The constellation point for message I is defined by
       In_Phase(I+1) and Quad(I+1), which specify the in-phase and
       quadrature component respectively.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, In_Phase, Quad, NUM, DEN), 
       METHOD='qask/arb', specifies the numerator (NUM) and denominator (DEN)
       of a lowpass filter in the demodulation. The sample time for the filter
       is 1/Fs. The constellation of the PSK can be plotted by using
       DMOD('qask/arb', In_phase, Quad).

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, NIC, AIC, PIC), METHOD = 'qask/cir'
       demodulates the modulated signal Y using the QASK method with circle
       form constellation. The number in circle, amplitude in circle, and a
       signature phase in circle are defined in NIC, AIC, and PIC
       respectively. The three vectors NIC, AIC and PIC have the same length.
       The constellation in each circle is evenly distributed in each ring
       with one of the points having its phase as the signature phase.
       When PIC is not given, PIC is assumed to be an all zero vector. When
       AIC is not given, the default value AIC = [1:length(NIC)] is used.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, NIC, AIC, PIC, NUM, DEN),
       METHOD = 'qask/cir', specifies the numerator (NUM) and denominator
       (DEN) of the lowpass filter in the demodulation. The sample time for
       the filter is 1/Fs. The constellation of the PSK can be plotted by
       using DMOD('qask/cir', NIC, AIC, PIC).
       
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, ...), METHOD = [METHOD, '/eye'],
       plots eye-pattern diagram before demapping.
qask_help_end

fsk_help_begin
DDEMOD M-ary frequency shift keying demodulation.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M), METHOD = 'fsk', demodulates a FSK
       modulated signal with carrier frequency Fc (Hz), digital message sample
       frequency Fd (Hz) and simulation sample frequency Fs (Hz). This
       function requires that Fs > Fd and Fs/Fd be positive integers. When
       Fd is a two element vector, the second element is the offset value for
       the decision point. The offset should be an integer. The offset timing
       is Fd(2)/Fs. The default offset is zero. The M-ary number for the
       FSK is M. The demodulated digital messages are in range [0, M-1]. A
       default tone space value TONE = 2 * Fd / M is used. For a correct
       solution, Fs/Fd must be greater than M. 

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, TONE), METHOD = 'fsk', specifies
       the tone space of the fsk in TONE.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, TONE), METHOD = 'fsk/eye', plots 
       eye-pattern diagram before demapping. Different from other eye-pattern
       diagrams, the eye-pattern diagram for FSK demodulation is the
       correlation value of the input signal to each possible digital signal.
       It is very expensive to plot FSK correlation eye-patterns both in
       computation time and memory space.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, Tone), METHOD = 'fsk/noncoherent'
       computes the demodulation using noncoherent method.

       The constellation of the FSK can be plotted by using 
       DMOD('fsk', M, Tone).
fsk_help_end

msk_help_begin
DDEMOD Minimum shift keying demodulation.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD), METHOD = 'msk', demodulates a MSK
       modulated signal with carrier frequency Fc (Hz), digital message sample
       frequency Fd(Hz) and simulation sample frequency Fs (Hz). This function
       requires that Fs > Fd and Fs/Fd be positive integers. When Fd is a
       two element vector, the second element is the offset value for the 
       decision point. The offset should be an integer. The offset timing is
       Fd(2)/Fs. The default offset is zero. The M-ary number for the MSK
       is 2. The demodulated digital messages are binary numbers. A default
       tone space value TONE = Fd is used. For correct solution, Fs /Fd
       must be greater than 2.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, TONE), METHOD = 'msk/eye', plots 
       eye-pattern diagram before demapping. The eye-pattern diagram for
       MSK demodulation is the correlation value of the input signal to both
       '0' and '1' decision. It is very expensive to plot MSK correlation
       eye-pattern both in computation time and memory space.

       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD, M, TONE), METHOD = 'msk/noncoherent'
       computes the demodulation using noncoherent method.
msk_help_end

sam_help_begin
DDEMOD Down sample a signal Y from sample frequency Fs to sample frequency Fd.
       Z = DDEMOD(Y, Fc, Fd, Fs, METHOD), METHOD = 'sample', takes the input
       signal Y with sample frequency Fs (Hz) and outputs signal Z with sample
       frequency Fd (Hz). When Y is a matrix, the function takes each column
       as individual signal. The output Z will have the same number of column 
       number as Y. Fs must be larger than Fd and Fs/Fd should be an integer.
       When Fd is a two element vector, the second element should be an
       integer which means the offset timing is Fd(2)/Fs. The default
       offset is zero. Fc is not used.
sam_help_end

eye_help_begin
DDEMOD Eye-pattern plot.
       DDEMOD(Y, Fc, Fd, Fs, METHOD), METHOD = 'eye', plots each column
       element in Y by eye-pattern diagram. When Y is a multi-column matrix,
       the colors for the columns are in the order of yellow, magenta, cyan,
       red, green, and blue. The time interval between two successive rows is
       1/Fs. The plot time window is 1/Fd. It is required that Fs > Fd, and
       Fs/Fd be an integer. When Fd is a two element vector, the second element
       is an integer which means the offset timing is Fd(2)/Fs. The default
       offset is zero. Fc is not used.
eye_help_end

sca_help_begin
DDEMOD Scatter plot.
       DDEMOD(Y, Fc, Fd, Fs, METHOD), METHOD = 'scat', produces scatter plot
       for the input signal Y. The time interval between two successive
       rows in Y is 1/Fs. The function takes a point to plot at sample
       frequency Fd. It is required that Fs > Fd, and Fs/Fd be an integer.
       When Fd is a two element vector, the second element is an integer
       which specifies that the offset for the plotting point is Fd(2)/Fs.
       The default offset is zero. When Y is a multi-column matrix, the colors
       for the columns are in the order of yellow, magenta, cyan, red, green,
       and blue. Fc is not used. When Y is a two column matrix, the scatter
       plot is a two-dimensional plot.        

       DDEMOD(Y, Fc, Fd, Fs, METHOD, SYMBOL) selects the plot symbol. SYMBOL
       can be one of the following characters: '.', '*', '+', 'x', 'o'.
sca_help_end

Wes Wang 10/3/95