US 6,320,912 B1 · Digital modulator

Abstract

There is disclosed a digital modulator whose modulation parameter can be controlled and in which modulation data or modulated signals are prevented from generating interference signals with adjoining circuits through control when power supply is turned on or system is changed. The digital modulator has a device for detecting that the power supply is turned on, and the transmission data is modulated with fixed data in response to an output of the detecting device for a time required for completing a required system constitution setting. The digital modulator also has a device for detecting the presence of the control for changing the system after the power supply is turned on. In response to an output of the detecting device, modulation is performed with the fixed data for a time from the start till the completion of the setting with a predetermined time added thereto.

Claims21

Dependent claims

A digital modulator for modulating transmission data in a required band, comprising:

means for outside control of a modulation parameter;
and
switching means for modulation with fixed data instead of said transmission data only for a predetermined time when turning on of a power supply of said digital modulator is detected or when a signal for said outside control is detected.

A digital modulator for modulating transmission data in a required band, comprising:

means for outside control of a modulation parameter;
a digital signal processor for converting an input data signal to two orthogonal strings of parallel data;
a switching circuit for inputting said parallel data and fixed data for each of said strings and switching in such a manner that said fixed data is outputted instead of said parallel data only for a predetermined time when a power supply of said digital modulator is turned on or when a signal for said outside control is detected;
a waveform shaping filter for shaping a waveform of each output of said switching circuit;
a D/A converter for receiving each output of said waveform shaping filter for digital-analog conversion;
a low-pass filter for receiving each output of said D/A converter and removing a high-frequency noise;
an orthogonal modulator for orthogonally modulating each output of said low-pass filter on a carrier frequency;
and
an amplifier for amplifying an output of said orthogonal modulator to a predetermined output.

6 more elements

Dependencies are inferred from the claim text.

Digital modulator

Life of this patent

Digital modulator

Life of this patent

Abstract

Claims21