Engee documentation

FM Modulator Baseband

Modulates data using the FM method.

fm modulator baseband

Description

The FM Modulator Baseband unit modulates a real input signal using the FM method and returns a complex output signal.

Ports

Input

# IN_1 — input signal
scalar | vector | matrix

Details

An input signal specified as a real scalar, vector or matrix.

Data types

Float64.
Complex numbers support

No

Output

# OUT_1 — output FM modulated signal
scalar | vector | matrix

Details

Output signal as a complex scalar, vector or matrix. The data on this port is of the same type and size as the input signal.

Data types

Float64.
Complex numbers support

Yes

Parameters

Main

# Frequency deviation (Hz) — modulator frequency deviation
Real number

Details

The deviation of the modulator frequency, in Hz, given as a positive scalar. The system bandwidth is equal to twice the sum of the frequency deviation and the signal bandwidth.

Default value

75e3
Program usage name

FrequencyDeviation
Tunable

No
Evaluatable

Yes

Extras

*Algorithms.

The frequency modulated bandwidth signal, , is specified as:

where

  • - carrier amplitude;

  • - carrier frequency;

  • - baseband input signal;

  • - frequency deviation in Hz.

Frequency deviation is the maximum shift from in one direction, given that τ .

The baseband FM signal may be derived from a bandwidth representation by downsampling the bandwidth signal at such that:

Removing the component at from leaves a representation of the baseband signal, which is given as

The expression for can be rewritten as , where .

The expression ] thus means that the input signal is a scaled version of the phase derivative, .

To recover the input signal from , use a basic delay demodulator as shown in this figure.

fm modulator baseband 1

See also

  1. FM Demodulator Baseband

References

  1. Hatai, I., and I. Chakrabarti. "A New High-Performance Digital FM Modulator and Demodulator for Software-Defined Radio and Its FPGA Implementation." International Journal of Reconfigurable Computing (December 25, 2011): 1-10.

  2. Taub, H., and D. Schilling. "Principles of Communication Systems." McGraw-Hill Series in Electrical Engineering, 142-55. New York: McGraw-Hill, 1971.