Sliding discrete Fourier transform-based mono-component amplitude modulation–frequency modulation signal decomposition

• Published in: IET communications Vol. 9; no. 9; pp. 1221 - 1229
• Main Authors: Sumathi, Parasuraman, Singh, Ksh Milan
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 11.06.2015
• Subjects: adaptive sampling frequency control; amplitude error; amplitude modulation; amplitude modulation signal retrieval; Amplitudes; Bessel functions; Bessel function‐based analysis; carrier signal tracking; centre carrier frequency; Decomposition; discrete Fourier transforms; error signal; field programmable gate array; Fourier analysis; frequency modulation; frequency modulation signal retreival; input signal frequency; Locking; locking condition; message signal extraction; message signal retrieval; Messages; Modulation; monocomponent amplitude modulation‐frequency modulation signals; monocomponent AM‐FM signal decomposition; numerically‐controlled oscillator; phase error; PLL capability; Retrieval; sampling pulses; SDFT bin‐0; SDFT bin‐1; SDFT‐PLL scheme; signal sampling; sinusoidal message signals; Sliding; sliding DFT filter; sliding discrete Fourier transform‐based phase locking scheme; unwanted spectral component removal; windowing effect; sliding DFT filter; message signal extraction; Bessel function-based analysis; SDFT-PLL scheme; input signal frequency; phase error; error signal; sampling pulses; windowing effect; field programmable gate array; signal sampling; monocomponent amplitude modulation-frequency modulation signals; adaptive sampling frequency control; frequency modulation; carrier signal tracking; amplitude modulation signal retrieval; discrete Fourier transforms; SDFT bin-0; SDFT bin-1; frequency modulation signal retreival; Bessel functions; message signal retrieval; monocomponent AM-FM signal decomposition; amplitude modulation; sliding discrete Fourier transform-based phase locking scheme; locking condition; amplitude error; PLL capability; centre carrier frequency; numerically-controlled oscillator; sinusoidal message signals; unwanted spectral component removal
• ISSN: 1751-8628; 1751-8636
• DOI: 10.1049/iet-com.2014.0643

The sliding discrete Fourier transform-based phase locking scheme (SDFT-PLL) has been adapted for the extraction of message signals from mono-component amplitude modulation–frequency modulation (AM–FM) signals. In the proposed scheme, the SDFT-PLL is designed to track a carrier signal, which has been modulated by sinusoidal message signals both in amplitude and frequency. The sliding DFT filter is prone to windowing effect if input signal frequency drifts from centre carrier frequency. The amplitude and phase errors caused by this effect have been utilised to achieve locking condition by adaptive sampling frequency control. The SDFT-PLL is modified in such a way that the numerically controlled oscillator produces sampling pulses suitable for SDFTbin-1 and SDFT bin-0 for the retrieval of frequency and amplitude modulation signals, respectively. Hence, the frequency and amplitude variation of monocomponent AM–FM could be retrieved simultaneously. Furthermore, Bessel function-based analysis provides an insight to the removal of unwanted spectral components present in error signal. Simulation results prove the capability of PLL in message signal retrieval for large variation in frequency and amplitude. The proposed scheme is implemented in field programmable gate array to validate the performance of SDFT-PLL in decomposition of the mono-component AM–FM signal.