Frequency modulator using a waveform generator

A technology of waveform generator and frequency modulation, which is applied in the direction of modulation, angle modulation, and modulated carrier system, etc. It can solve the problems of increasing system cost and adding lookup tables, etc.

Inactive Publication Date: 2003-10-22
FREESCALE SEMICON INC
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

If the reference clock has to be modified, for each reference clock, the number of look-up tables must be increased, which results in increased system cost

Method used

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  • Frequency modulator using a waveform generator
  • Frequency modulator using a waveform generator
  • Frequency modulator using a waveform generator

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Embodiment Construction

[0017] FIG. 1 shows one embodiment of multi-mode loop FM modulation 10 . In one embodiment of the present invention, the FM waveform generator 12 raw frequency offset 43 is used to provide the raw frequency offset value. FM waveform generator 12 also utilizes input data port 40 to receive input data. Select span 45 , oversample select 42 , decimate select 44 and pulse shaping coefficient input 46 are used to provide control and select information to FM waveform generator 12 . The FM waveform generator 12 is used to generate the high port frequency offset signal 54 which is used to provide a zero frequency input to the first input of the multiplexer 14 as a second input to the multiplexer 14 Signal. A mode select signal 48 is provided to select which input of the multiplexer 14 is provided to the programmable delay circuit 16 . The programming mechanism of the programmable delay circuit can be software or hardware (not shown). The output of the programmable delay circuit 16...

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Abstract

A Multi-mode Loop Frequency modulator (10) for modulating a carrier signal according to various modulation pulse shapings and data signal to provide a modulated output signal (VCOout), comprises a waveform generator (12) and two multiplexors (14, 38) to perform various pulse shaping filtering and or predistord the pulse shaping filter impulse response for either a dual port modulation or for a single port modulation. The waveform generator (12) can also provide interpolation to input frequency deviation and also provide scaling for various reference frequency clock provided by the crystal (30) and the reference divider (28). The low pass filter (22) is used for providing the PLL loop filtering and also as the smoothing filter for the high port DAC (18).

Description

technical field [0001] The present invention relates to a frequency modulator, and more particularly, to a frequency modulator using a waveform generator. Background technique [0002] Many digital wireless communication systems such as cellular, cordless and data transmission systems use FSK, GFSK (Gaussian Frequency Shift Keying) or GMSK (Gaussian Mean Keying) modulation techniques. In effect, these modulation techniques are simple frequency modulation (FM) encapsulated with a constant radio frequency (RF) signal. [0003] Since no amplitude modulation (AM) is involved in these modulation techniques, the voltage controlled oscillator (VCO) frequency can be modulated directly with the baseband signal, as in conventional analog FM transmitters, such as in analog cellular systems. Modulating the VCO frequency directly can significantly reduce costs. This configuration is especially desirable in digital applications where low cost is a key factor. For example, the overall c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03C3/09H03L7/107H03L7/18H04L27/12H04L27/20
CPCH03C3/095H03C3/0925H04L27/2017H03C3/0941H03L7/00
Inventor 纳迪姆·赫拉特
Owner FREESCALE SEMICON INC
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