DSP BASED DIGITAL FM DEMODULATION FOR GMSK SIGNALS PDF

This is the traditional discrete signal FM demodulation method, and it is based on copyrighted material from “Understanding Digital Signal. this with digital signal processing. In an earlier semester project, four FM demodulation algo- are are implemented on the DSP (TMSCDSK). radio provider organizations are planning to replace their traditional analog FM-based. the demodulation of signals that follow the AM-FM model. Traditional such as CPM, CPFSK, FSK, MSK, GMSK and other forms of digital modulation, can be reformulated as digital FM mod- ulation and component AM-FM signal demodulation. The ESA and . threshold around Yo = dB the MESA-based demodu-.

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Idgital base-band in phase and base-band quadrature signals B I and B Q are separately squared in squaring functions and In function block 22, the samples are subjected to matched filtering with a matched filter. Feedback of previous bit decisions to the computation of correlations provides several advantages.

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GMSK in-phase and phase quadrature signals embedded in an FM signal are first generated from an IF frequency and frequency shifted down to baseband. Year of fee payment: The method of claim 16 including the step of temporally delaying said first and second signals before producing detected in-phase and quadrature components.

This type of receiver usually includes two parts; a first portion that extracts the bit clock and phase of the signalling tones, and a detector that uses the extracted signal phase.

US USA en The signal from antenna 10 is amplified in amplifier 11 and then subject to down conversion in down converter 12 to recover signal z k. And, p t is a pulse shaping function described as EQU2 For the demodulator design according to the present invention, the second interpretation is used.

The signals output from low pass filters and being the sine and cosine representations of a reference angle, are passed to an arc tangent calculator in the correction signal unit The method of demodulating recited in claim 19 wherein the step of computing a correlation output further comprises computing a second correlation for at least one bit pattern combination, said second correlation derived from a multiplication of the output of the matched filter and said at least one bit pattern combination.

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If the baseband signals are raised to the fourth power, the correction signal unit 40 will have to divide the output of the arctangent calculator by four.

USA – DSP-based GMSK coherent detector – Google Patents

In one embodiment the delay provided by the delay circuits and equal the propagation delay through the coherent carrier recovery unit 20 and the correction signal unit The device of claim 12, wherein said correlator further computes a second correlation for at least one bit pattern combination, said second correlation derived from a multiplication of the output of the matched filter and said at least one bit pattern combination.

The method of claim 24 including the step of dividing said correction angle signal by a factor of two demoduoation a second correction angle signal. US USA en Parallel correlator architecture for synchronizing direct sequence spread-spectrum signals. The outputs of these two multipliers baser are combined in a summer which yields the in-phase signal I, Method and apparatus for combined frequency offset and timing offset estimation. A detector for detecting in-phase and quadrature components of an information signal comprising: An improved method and apparatus for demodulators for MSK signals.

The base-band in-phase signals as well as the base-band phase quadrature signals B I and B Q are also multiplied together in a multiplier to produce a signal that is the magnitude of the imaginary component of the GMSK signal, This is a realization of equation 4 where the digital filter performs EQU6 where EQU7 Note that match filtering is done over a 2-bit time period.

CA CAC en A digital signal processor is preferably used.

The outputs of the multipliers andwhich are passed through low pass filters andyield two signals equal to the sine and cosine respectively of the angle between the base-band in-phase and the base-band phase quadrature components.

The foregoing and other objects, aspects and advantages will be better understood from the following derailed description of a preferred embodiment of the invention with reference to the drawings, in which:. The DSP 50 produces a data signal and a clock signal which is the desired demodulated information.

The method of claim 26 including the step of multiplying said first signal by a first correction signal providing a first product signal and multiplying said second signal by a second correction signal providing a second product signal. The divider circuit is required because the squaring functions performed in the coherent carrier recovering unit 20 generates a frequency twice that of the desired signal. Theta in the correction signal unit 40 fo its cosine and sine calculated by cosine and sine circuits and to yield two dihital signals, cosine theta and sine theta and ssp.

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Element is a substractor and functionally calculates the difference between the two signals squared by squaring functions and The method of demodulating recited in claim 9 further comprising the steps of differentially decoding and bit mapping d k to generate a demodulated bit stream.

Method for signal transmission using spectrally efficient orthogonal modulation. First, it improves the performance of the demodulator.

Method and system for demodulating GMSK signals in a cellular digital packet data system. Second, it reduces demodulagion computational loads, especially if the observation interval increases.

Multi-level quadrature amplitude modulator system with fading compensation means. For digital matched filter implementations, z t should be appropriately sampled; i. The device of claim 11, wherein said correlator computes a first correlation by summing a sequence of multiplications of the output of the matched filter with a first correlation function based on at least one previously selected bit.

US5131008A – DSP-based GMSK coherent detector – Google Patents

The detector of claim hmsk wherein said first and second signals are baseband signals. The method of claim 22 further including the step of calculating the arctanagent of the sine signal divided by the cosine signal producing a first correction angle signal.

Digital signal processors DSPs are also known in the art, and provide a number of significant advantages in radio design.

The method of demodulating recited in claim 6 wherein said matched filter filters the sampled received signal according to EQU17 where EQU The base-band in-phase and base-band quadrature signals, B I and B Q are received at the coherent carrier recovery unit 20 as shown. The device recited in claim 11 further comprising logic for performing differential decoding and bit mapping on said selected bit.

The method of claim 23 including the step of calculating the cosine and sine of said correction angle producing first and second correction signals respectively. The demodulator recited in claim 2 wherein said non-coherent correlator computes EQU