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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The output of the arc tangent calculator is coupled to a divider circuit which divides the angle rendered diital the arc tangent circuit by two. A doubly differential detector for digital transmission with continuous phase modulation. For example, the incoming baseband signals might be raised to the fourth power in the coherent carrier recovery unit Multi-level quadrature amplitude modulator system with fading compensation means.
The output of these two squaring functions are combined in a subtracter to yield a signal representative demodulatuon the magnitude of the real components of the GMSK signal Referring now to FIG. Note that these bzsed are performed per bit interval. 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.
Method and apparatus for quadrature multi-pulse modulation of data for spectrally efficient communication. 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. Parallel correlator architecture for synchronizing direct sequence spread-spectrum signals.
This signal is first passed though matched filter 13 before being supplied to non-coherent correlator The detector of claim 1 wherein the correction signal means includes means for multiplying said second signal by a first correction signal providing a third product signal and means for multiplying said second signal by a second correction signal providing a fourth product signal.
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. Method and apparatus for combined frequency offset and timing offset estimation.
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 ror. Referring now to the drawings, and more particularly to FIG. There are several demodulation structures for GMSK such as a Frequency Modulation FM discriminator, coherent demodulation and differential demodulation.
US5131008A – DSP-based GMSK coherent detector – Google Patents
Even though coherent demodulation is generally considered the best demodulation for GMSK modulated signals, the performance is not guaranteed under fading channel gm. The correction signal unit 40 receives the bbased and imaginary coherent carrier signal components, and and produces a correction factor signal, theta. 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 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.
Digital receiver fast frequency and time acquisition system using a single synchronization word and method of using same.
Method of rapidly controlling the frequency of a bmsk radio receiver and apparatus for carrying out the method. While the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.
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 eigital correlation derived from a multiplication of the output of the matched filter and said at least one bit pattern combination. 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.
First, it improves the performance of the demodulator. Method and apparatus for real-time demodulation of a GMSK signal by a non-coherent receiver. An improved method and apparatus for demodulators for MSK signals. Method and circuitry for determining symbol timing for time division multiple access radio systems.
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 outputs of these two multipliers and are combined in a summer which yields the in-phase signal I, The DSP 50 also provides an AFC control back to the superheterodyne receiver front-end required to permit the radio to stay on frequency.
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 ddemodulation bit pattern combination.
The detector of claim 7 wherein the correction signal means includes means for calculating the arctangent of the sine signal divided by the cosine signal producing a first correction angle signal.
USA – DSP-based GMSK coherent detector – Google Patents
The detector of claim 1 including a delay means coupled between said first and second signals and said correction means for temporally delaying said first and second signals to said correction means. The method of claim 16 including the step of temporally delaying said first and second signals before producing detected in-phase and quadrature components.
Ditital baseband in-phase and phase quadrature signal components are digitized and coupled to a digital signal processor, DSP where the clock and data signals are recovered.
Method and apparatus for symbol clock recovery from signal having wide frequency possibilities. 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. The detector of claim 1 wherein the correction signal means includes means for multiplying said in-phase coherent and quadrature coherent signals by said clock signal producing, respectively, an in-phase demovulation carrier component and a quadrature coherent carrier component.
The method of claim 16 further including the step of multiplying said in-phase coherent and quadrature coherent signals by said clock signal producing, respectively, an in-phase coherent carrier component and a quadrature coherent carrier component. Method for signal transmission using spectrally efficient orthogonal modulation. Method of demodulation in digital communication systems with multipath propagation. A base-band phase quadrature signal is produced by multiplying the IF by a ninety degree shifted signal from the local oscillator 5.
The method of claim 29 including the step of summing said third and fourth product signals providing the quadrature corrected data signal.