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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Digital signal processors DSPs are also known in the art, and provide a number of significant advantages in radio design. Field of the Invention The present invention generally relates to demodulators for communication systems and, more particularly, to a new non-coherent demodulator for a digital communication system which exhibits superior performance in a fading channel.

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:.

US5131008A – DSP-based GMSK coherent detector – Google Patents

Method and apparatus for symbol clock recovery from signal having wide frequency possibilities. An improved method and apparatus for demodulators for MSK signals.

The detector of claim 1 wherein the correction signal means includes means for multiplying said in-phase coherent gnsk quadrature coherent signals by said clock signal producing, respectively, an in-phase coherent carrier component and a quadrature coherent carrier component. The correction dssp is used to demodulate the in-phase and quadrature signals at base-band to produce the data and clock signals which are thereafter digitally decoded.

A base-band phase quadrature signal is produced by multiplying the IF by a ninety degree shifted signal from the local oscillator 5.

The detector of claim 1 wherein said means for providing in-phase and quadrature coherent carrier signals by factoring the first and second signals includes means xemodulation mathematically squaring said first and second signals and providing signal and quadrature portions of said first and second signals.

First, it improves the performance of the demodulator. An incoming signal is received at an antenna 2 and processed in an superheterodyne receiver 3 which produces a first intermediate frequency IF 4. The device of claim 11, wherein said matched filter sums a sequence of multiplications between a conjugated sequence indicative of said samples of a GMSK signal and a sequence derived from a sinusoidal function. The method of claim 21 further including the step of low-pass filtering the in-phase coherent carrier component producing a sine signal and low-pass filtering the quadrature coherent carrier component producing a cosine signal.

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For example, the incoming baseband signals might be raised to the fourth digiital in the coherent carrier recovery unit The correction factor signal, theta from the correction signal unit 40 is used in a correction unit 60 to demodulate the base-band in-phase and base-band quadrature signals, B I and B Q to yield an in-phase coherent data signal and a demoduoation coherent data signal as shown.

Even though coherent demodulation is generally considered the best demodulation for GMSK modulated signals, the performance is not guaranteed under fading channel conditions.

Element is a substractor and functionally calculates the difference between the two signals squared by squaring functions and Year of fee payment: The DSP implements interpolation and phase eigital which can be considered as a part of down converter 12, the matched filter 13, the non-coherent correlator 14 and the ML decision logic The detector of claim 1 wherein the correction signal means includes means for multiplying said first signal by a first correction signal providing a demodulahion product signal and means for multiplying said second signal by a second eignals signal providing a second product signal.

Digital receiver fast frequency and time acquisition system using a single synchronization word and method of using same. In one embodiment, a delay element is incorporated to accommodate for certain types of fading of the receive signal as the receiver travels through various geographic areas. The output of multiplier and are both added in the summer which yields the phase quadrature signal component Q, as shown. Method and apparatus for symbol clock recovery from signal having wide frequency possibilities.

The method of demodulating recited in claim 18 wherein the step of computing a correlation output is performed by computing a first correlation by summing a sequence of multiplications of the output of the matched filter with a first correlation function based on past bit decisions.

USA – DSP-based GMSK coherent detector – Google Patents

US USA en 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 coherent carrier recovery unit 20 in the preferred embodiment, as shown in FIG. The detector of claim 14 including means for summing said third and fourth product signals providing the quadrature corrected data signal.

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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. 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.

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. Theta in the correction signal unit 40 has its cosine and sine calculated by cosine and sine circuits and to yield two correction signals, cosine theta and sine theta and respectively. The output d k is also fed to function block 27 where differential decoding and bit mapping are performed to derive output d kwhich is the demodulated information bit stream.

This invention relates generally to recovery of binary encoded signals, and particularly to recovery of coherent carrier signal information included therewith. 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. For the demodulator design according to the present invention, the second interpretation is used.

The bases signal is derived from the in-phase coherent carrier signal and the quadrature carrier signal to produce a correction signal representative of a correction angle required to demodulate the GMSK. Adaptive variable-gain phase and frequency locked loop for rapid carrier acquisition.

This signal is first passed though matched filter 13 before being supplied to non-coherent correlator And, p t is a pulse shaping function described as EQU2. The arc tangent calculator yields a signal which represents the angle between the base-band information signal and the reference axes used to demodulate GMSK.

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Note that these functions are performed per bit interval. Parallel correlator architecture for synchronizing direct sequence spread-spectrum signals. Year of dlgital payment: In the preferred embodiment, the coherent carrier recovery unit 20 squared the baseband in-phase and phase-quadrature signals B I and B Q to recover the phase coherent carrier and Method of demodulation in digital communication systems with multipath propagation.