fskmod

Frequency shift keying modulation

Syntax

y = fskmod(x,M,freq_sep,nsamp)

y = fskmod(x,M,freq_sep,nsamp,Fs)

y = fskmod(x,M,freq_sep,nsamp,Fs,phase_cont)

y = fskmod(x,M,freq_sep,nsamp,Fs,phase_cont,symorder)

Description

y = fskmod(x,M,freq_sep,nsamp) outputs the complex envelope y of the modulation of the message signal x using frequency shift keying modulation.

y = fskmod(x,M,freq_sep,nsamp,Fs) specifies the sampling rate of y.

y = fskmod(x,M,freq_sep,nsamp,Fs,phase_cont) specifies the phase continuity.

y = fskmod(x,M,freq_sep,nsamp,Fs,phase_cont,symorder) specifies how the function assigns binary words to corresponding integers.

Examples

Plot FSK Signal Spectrum

Generate an FSK modulated signal and display its spectral characteristics.

Set the function parameters.

M = 4;       % Modulation order
freqsep = 8; % Frequency separation (Hz)
nsamp = 8;   % Number of samples per symbol
Fs = 32;     % Sample rate (Hz)

Generate random M-ary symbols.

x = randi([0 M-1],1000,1);

Apply FSK modulation.

y = fskmod(x,M,freqsep,nsamp,Fs);

Create a spectrum analyzer System object™ and call it to display a plot of the signal spectrum.

specAnal = spectrumAnalyzer(SampleRate=Fs);
specAnal(y)

Input Arguments

x — Input signal

vector | matrix

Input signal, specified as a vector or matrix of positive integers. The elements of x must have values in the range of [0, M – 1]. If x is a matrix, fskmod processes the columns independently.

Example: randi([0 3],100,1)

Data Types: double

M — Modulation order

integer power of two

Modulation order, specified as an integer power of two.

Example: 2 | 4 | 16

Data Types: double

symorder — Symbol order

'bin' (default) | 'gray'

Symbol order, specified as 'bin' or 'gray'. This argument specifies how the function assigns binary vectors to corresponding integers.

• If symorder is 'bin', the function uses a natural binary-coded ordering.

• If symorder is 'gray', the function uses a Gray-coded ordering.

Data Types: char

freq_sep — Desired separation between frequencies

positive scalar

Desired separation between frequencies, specified in Hz. By the Nyquist sampling theorem, freq_sep and M must satisfy (M-1)*freq_sep <= 1.

Data Types: double

nsamp — Number of samples per output symbol

positive scalar greater than 1

Number of samples per output symbol, specified as a positive scalar greater than 1.

Data Types: double

Fs — Sample rate

1 Hz (default) | positive scalar

Sample rate, specified as a positive scalar.

Data Types: double

phase_cont — Phase continuity

'cont' (default) | 'discont'

Phase continuity, specified as either 'cont' or 'discont'. Set phase_cont to 'cont' to force phase continuity across symbol boundaries in y, or 'discont' to avoid forcing phase continuity.

Data Types: char

Output Arguments

y — FSK-modulated output signal

vector | matrix

Complex baseband representation of a FSK-modulated signal, returned as vector or matrix of complex values. The columns of y represent independent channels.

Data Types: double | single
Complex Number Support: Yes

References

[1] Sklar, Bernard. Digital Communications: Fundamentals and Applications. Upper Saddle River, NJ: Prentice-Hall, 2001.

Version History

Introduced before R2006a