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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An improved method and apparatus for demodulators for MSK signals. The signals output from low pass filters and being gmsi sine and cosine representations of a reference angle, are passed to an arc tangent calculator in the correction signal unit The detector of claim 12 including means for summing said first product signal with said second product signal providing the in-phase corrected data signal.
USA – DSP-based GMSK coherent detector – Google Patents
The base-band in-phase signal B I is also multiplied by cosine theta in the multiplier The detector of claim 6 wherein the correction signal means includes means for low-pass filtering the in-phase csp carrier component producing siignals sine signal and means for low-pass filtering the quadrature coherent carrier component producing a cosine signal.
Note that these functions are performed per bit interval. A base-band phase quadrature signal is produced by multiplying the IF by a ninety degree shifted signal from the local oscillator 5. Method of rapidly controlling the frequency of a coherent radio receiver and apparatus for carrying out the method.
This invention relates generally to recovery of binary demodulagion signals, and particularly to recovery of coherent carrier signal information included therewith.
The IF 4 is coupled to two multipliers 7 and 8 which are used to produce an in-phase base-band signal and a phase-quadrature base-band signal. The detector of claim 1 wherein the correction signal means includes means for multiplying said digitall signal by a first correction signal providing a first product signal and means for multiplying said second signal by a second correction signal providing a second product signal.
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. The past bit decisions are fed back to the ML decision logic. The demodulator recited in claim 2 wherein said non-coherent correlator computes EQU Parallel correlator architecture for synchronizing direct sequence spread-spectrum signals.
In one embodiment, a delay element is incorporated to wignals for certain types of fading of the receive signal as the receiver travels through various geographic areas. Squaring the baseband signals in the coherent carrier recovery unit 20 necessitates dividing the output of the arctangent calculator by a factor of two to cancel-out the frequency doubling that results when sine or cosine functions are squared.
The correction signal 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. US USA en Year of fee payment: Having thus described our invention, what we claim as new and desire to secure by Letters Patent is as follows: The method of claim 16 further including the step of mathematically squaring said first and second signals and providing in-phase and quadrature portions of said first and demodulatino signals.
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These real and imaginary components and are coupled to demodulationn correction signal unit 40 as shown. Method and circuitry for determining symbol timing for time division multiple access radio systems.
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. A first stage in the demodulator is a coherent carrier recovery unit 20 which receives the digitized base-band in-phase component B I and the base-band quadrature component B Q and produces two new signals and which represent the magnitude of the real and which represent the magnitude of the real and imaginary components of the base-band in-phase and base-band quadrature carrier signals, B I and B Q respectively.
The coherent carrier recovery unit 20 in the preferred embodiment, as shown in FIG. The device recited in claim 11 further comprising logic for performing differential decoding and bit mapping on said selected bit.
US5131008A – DSP-based GMSK coherent detector – Google Patents
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. The detector of claim 1 wherein said first and second signals are IF signals. In function block 22, the samples are subjected to matched filtering with a matched filter.
Second, it reduces the computational loads, especially if the observation remodulation increases. The information bit stream is determined by the following differential decoding: The method of claim 24 including the step of dividing said correction angle signal by demodulagion factor of two producing a second correction angle signal.
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 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 for mathematically squaring said first and second signals and providing in-phase and quadrature portions of said first and second 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, 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.
Element is a substractor and functionally calculates the difference between the two signals squared by squaring functions and 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 method of claim 16 including the step of temporally delaying said first and second signals before producing detected in-phase and quadrature components. The sine theta and cosine theta correction signals are coupled to the correction unit 60 which takes the base-band in-phase and base-band phase quadrature signals B I and B Q and processes these signals together to yield the in-phase data signal I and the phase quadrature data signals, Q. The demodulator recited in claim 4 wherein said matched filter, said non-coherent correlator and said maximum likelihood decision logic are implemented with a digital signal processor.
Method and apparatus for obtaining initial carrier and symbol phase estimates for use in synchronizing transmitted data. The method of demodulating recited in claim 6 wherein said matched filter filters the sampled received signal according to EQU17 where EQU