System and methods for automatic deviation setting and control in radio transmitters

An automatic offset and control system technology, applied in radio transmission systems, automatic power control, transmission systems, etc., can solve the problem of reduced sensitivity of VCO control line modulation

Inactive Publication Date: 2000-09-06
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the time constant (α·R 0 )(C 0 / α) and R 0 C 0 same, so the resulting frequency response is flat, but the modulation sensitivity of the VCO control line is scaled down by α

Method used

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  • System and methods for automatic deviation setting and control in radio transmitters
  • System and methods for automatic deviation setting and control in radio transmitters
  • System and methods for automatic deviation setting and control in radio transmitters

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Embodiment Construction

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] The invention is described in more detail below with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. However, the present invention can also be implemented in many other forms, and it should not be considered limited to the embodiments described here. On the contrary, these embodiments are presented only in order to make this description more comprehensive and complete, and to fully describe the whole content of the present invention. presented to those skilled in the art. Like numbers refer to like parts throughout the drawings.

[0025]A fractional-N frequency synthesizer utilizing two-point modulation will be considered in describing the invention. In this way, common analog (audio frequency) frequency modulation can be realized, and digital data frequency modulation can be realized by using modulation methods such as Gaussian minimum frequency shift keying ...

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Abstract

A frequency modulation (FM) radio transmitter, such as a cellular telephone, includes an automatic deviation control system to automatically compensate for varying sensitivity of the FM transmitter. The FM transmitter includes a phase lock loop including a controlled oscillator that produces a frequency modulated input signal on an output channel frequency in response to a control input that is applied thereto. A scaler is responsive to the input signal and to at least one scaling content, to scale the input signal based upon the at least one scaling constant and to provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on the channel frequency. An automatic deviation control system measures the control signal that is applied to the controlled oscillator when tuned to one of the plurality of output channel frequencies and updates at least one of the scaling constants based upon the measured control input, to thereby provide automatic deviation control.

Description

field of invention [0001] The present invention relates generally to the field of radio communications, and more particularly to frequency modulation in radio transmitters. Background of the invention [0002] An FM transmitter can modulate a voice signal onto an RF signal by controlling a voltage-controlled oscillator operating at an output frequency with a voice-band voltage signal. With the help of a phase-locked loop or frequency synthesizer, the average frequency can be precisely controlled to the desired channel frequency relative to a precise crystal reference. The voiceband signal exhibits a momentary shift in frequency from the mean, which is synchronized with the microphone's speech waveform. [0003] In general, the relationship between the voice signal and the frequency offset should be controlled within tight tolerances. Too much frequency offset can cause the signal to temporarily drift into adjacent channels, creating "sideband clicks" interference. A frequ...

Claims

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Application Information

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IPC IPC(8): H03C3/00H03C3/09H03L7/183H03L7/189H03L7/197H04B1/04H04B7/01
CPCH03L7/197H03C3/0966H03C3/0925H03L7/189H03C3/0933H03C3/095H03C3/0941
Inventor P·W·登特
Owner TELEFON AB LM ERICSSON (PUBL)
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