JPH06268695A - Data transmitter - Google Patents

Abstract

PURPOSE:To provide a data transmitter which can delete the leakage of a carrier wave signal in the case of quadrature modulation using a digital modulating system. CONSTITUTION:Input data (a) are encoded by an encoding part 1, I and Q components are generated by digital signal processing, the bands of transmitting signals are limited by transmission filter parts 2 and 3, and the I and Q component signals are quadrature modulated by means of digital signal processing by an quadrature modulation part 4 and converted to analog signals by a D/A conversion part 5. Afterwards, an unnecessary frequency component caused by D/A conversion is removed by a filter part 6, an unnecessary frequency component caused by quadrature modulation is removed by an SSB modulation part 7 and converted to a radio frequency by a frequency conversion part 8, and an unnecessary signal caused by frequency conversion is removed by a filter part 9. Therefore, since the quadrature modulation is performed by digital signal processing by the quadrature modulation part 4, the leakage of waves to be modulated is eliminated and communication quality is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carrier leak elimination in a transmitter of a communication device using a digital modulation method.

[0002]

2. Description of the Related Art In recent years, a digital modulation method has been adopted in the field of communication, particularly in land mobile communication, to effectively use frequencies.

FIG. 8 is a block diagram showing the structure of a conventional data transmission device using a digital modulation method. Figure 8
In the figure, 101 is an encoding unit that encodes input data according to a signal point arrangement of a modulation method and generates I and Q components by digital signal processing, and 102 and 103 are transmission filters that limit the band of a transmission signal by digital signal processing. Section, 104,
105 is a D / which converts a digital signal into an analog signal
A section, 106 and 107 are filter sections that pass only the low frequency band, 108 is a quadrature modulation section that quadrature modulates the I and Q component signals that have become analog signals, and 109 is a frequency conversion section that converts the frequencies to the frequencies actually used for communication. Reference numeral 110 is a filter unit that deletes frequency components that are not related to communication generated during frequency conversion, 111 is a power amplification unit that amplifies transmission power, and 112 is a transmission antenna unit that radiates radio waves into space.

Next, the operation of the above conventional example will be described. First, the encoding unit 101 encodes the input data by digital signal processing according to the signal point arrangement of the modulation method, generates the I component signal A and the Q component signal B, and outputs them to the transmission filter units 102 and 103, respectively. The transmission filter units 102 and 103 limit the band of the I component signal A and the Q component signal B by digital signal processing, and output them to the D / A conversion units 104 and 105. D / A converters 104, 1
Reference numeral 05 is an analog conversion of the I component signal and the Q component signal that are band-limited and input as a digital signal,
It outputs to 6,107. The filter units 106 and 107 are
Unwanted frequency band signal components generated by digital signal processing are removed and output to the quadrature modulation unit 108. The quadrature modulation unit 108 performs quadrature modulation on the input I component signal and Q component signal according to the first local and outputs an IF signal. The frequency conversion unit 109 converts the IF signal into a radio frequency signal actually used for communication according to the second local and outputs the radio frequency signal to the filter unit 110. The filter unit 110 removes an unnecessary signal generated during frequency conversion in the frequency conversion unit 109 from the radio frequency signal, and outputs the radio frequency signal to the power amplification unit 111. The power amplification unit 111 power-amplifies the input signal and outputs it to the transmission antenna unit 112. Transmission antenna section 1
12 radiates the output of the power amplification unit 111 into space.

[0005]

However, in the data transmission apparatus using the digital modulation method according to the above-mentioned conventional example, the quadrature modulator performs quadrature modulation using the analog element, so that the output of the quadrature modulator has a modulated signal component. Not only that, the carrier signal component used for quadrature modulation leaks in. This leaked carrier signal component appears as a DC offset component when it is decoded on the receiving side, and there is a problem that the communication quality deteriorates.

The present invention solves the above problems,
It is an object of the present invention to provide a data transmission device capable of improving communication quality by eliminating leakage of a carrier signal component at the time of quadrature modulation by processing up to quadrature modulation using digital signal processing.

[0007]

In order to solve the above problems, the present invention provides a coding means for coding input data according to the signal point arrangement of a modulation system and generating I and Q components by digital signal processing. , Band limiting means for transmitting signals by digital signal processing, quadrature modulating means for quadrature modulating I and Q component signals by digital signal processing, D / A converting means for converting digital signals into analog signals, and D / A converting Filter means for removing unnecessary frequency components due to SSB modulation means for removing unnecessary frequency components due to quadrature modulation,
A frequency conversion means for converting to a radio frequency actually used, a filter means for removing unnecessary signals generated by the frequency conversion, a power amplification means for amplifying transmission power, and a radio wave radiation means for radiating radio waves into space. Be prepared.

[0008]

Since the present invention uses the method of quadrature-modulating the I and Q component signals by digital signal processing with the above-described configuration, there is no leakage of carrier waves in the quadrature-modulated output as in the conventional example, and communication quality can be improved. Has the effect.

[0009]

1 is a block diagram showing the configuration of a data transmission apparatus of the present invention. In FIG. 1, reference numeral 1 denotes an encoding unit (encoding means) that encodes input data according to a signal point arrangement of a modulation method and generates I component and Q component by digital signal processing,
Reference numerals 2 and 3 denote a transmission filter unit (band limiting unit) that limits the band of a transmission signal by digital signal processing, 4 denotes a quadrature modulation unit (quadrature modulation unit) that performs quadrature modulation of I and Q component signals by digital signal processing, A D / A section (D / A conversion means) for converting a digital signal into an analog signal, 6 is a filter section (filter means) for removing unnecessary frequency components generated during D / A conversion, and 7 is generated by quadrature modulation. SSB (single sideband) modulator (SSB modulator) that removes negative frequency components, 8 is a frequency converter (frequency converter) that converts the frequency to a frequency actually used for communication, and 9 is communication that occurs during frequency conversion. A filter unit (filter unit) for deleting frequency components unrelated to the above, 10 is a power amplification unit (power amplification unit) for amplifying transmission power, and 11 is a transmission antenna unit (radio wave emission unit) for radiating radio waves into space. It is.

Next, the operation of the above embodiment will be described. First, the encoding unit 1 encodes the input data by digital signal processing in accordance with the signal point arrangement of the modulation method, and I
The component signals A and Q component signals B are generated and output to the transmission filter units 2 and 3, respectively. The transmission filter units 2 and 3 perform the I-component signals A and Q by digital signal processing using a sampling frequency that is at least twice the required frequency band.
The band of the component signal B is limited, and the I component signal C and the Q component signal D are output to the quadrature modulator 4. FIG. 2 shows spectra of the I component signal C and the Q component signal D. In FIG.
It can be seen that the spectrum is repeated at frequency intervals half the sampling frequency S according to the sampling theorem. The quadrature modulator 4 performs digital signal processing on the input I component signal C and Q component signal D so that the spectrum directly used for data transmission enters a positive frequency region as shown in FIG. Quadrature modulation is performed so that the spectrum does not exist in one-half or more of the band, and D
And outputs to the / A conversion unit 5.

The D / A converter 5 converts the digital quadrature modulated signal E into an analog signal and outputs the analog quadrature modulated signal F to the filter unit 6. FIG. 3 shows an analog quadrature modulation signal F
Shows the spectrum of. The filter unit 6 removes unnecessary frequency band signal components generated by digital signal processing, and S
Output to the SB modulator 7. FIG. 4 shows the spectrum of the analog quadrature modulation signal G. The SSB modulator 7 considers the analog quadrature modulated signal G as a baseband signal, performs SSB modulation, generates an IF signal H, and outputs the IF signal H to the frequency converter 8. FIG. 5 shows the spectrum of the IF signal H. Here, n is an intermediate frequency (modulation frequency).

The frequency converter 8 converts the IF signal H so that the center of the spectrum used directly for data transmission in accordance with the local coincides with the radio frequency actually used for communication.
Output to the filter unit 9. FIG. 6 shows the spectrum of the radio frequency signal I. Where m is the radio frequency. The filter unit 9 removes an unnecessary signal generated at the time of frequency conversion in the frequency conversion unit 8 from the radio frequency signal I and outputs it to the power amplification unit 10. FIG. 7 shows the spectrum of the radio frequency signal J. The power amplification unit 10 power-amplifies the input signal and outputs it to the transmission antenna unit 11. The transmission antenna unit 11 radiates the output of the power amplification unit 10 into space.

[0013]

As described above, according to the data transmitting apparatus of the present invention, the coding means for coding the input data according to the signal point arrangement of the modulation system and generating the I component and the Q component by the digital signal processing, Band limiting means for limiting the band of a transmission signal by digital signal processing, and I, Q by digital signal processing
Quadrature modulation means for quadrature modulating the component signal, D / A conversion means for converting the digital signal into an analog signal, and D / A
Filter means for removing unnecessary frequency components generated at the time of A conversion, SSB modulation means for removing negative frequency components caused by quadrature modulation, frequency conversion means for converting to a frequency actually used for communication, and frequency conversion Directly necessary for data transmission, the carrier signal component at the time of quadrature modulation is provided by the filter means that removes frequency components that are not related to communication that occur sometimes, the power amplification means that amplifies the transmission power, and the radio wave radiation means that radiates radio waves into space. There is an effect that it is possible to perform quadrature modulation without leaking to a frequency band considered to be, and to reduce deterioration of data decoding quality at the time of reception due to leakage of a carrier signal component.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a data transmission device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an output spectrum of a quadrature modulator 4 in FIG.

3 is a diagram showing an output spectrum of a D / A section 5 in FIG.

FIG. 4 is a diagram showing an output spectrum of a filter unit 6 in FIG.

5 is a diagram showing an output spectrum of the SSB modulator 7 in FIG.

6 is a diagram showing an output spectrum of the frequency conversion unit 8 in FIG.

FIG. 7 is a diagram showing an output spectrum of a filter section 9 in FIG.

FIG. 8 is a configuration block diagram of a conventional data transmission device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coding section 2 Transmission filter section 3 Transmission filter section 4 Quadrature modulation section 5 D / A section 6 Filter section 7 SSB modulation section 8 Frequency conversion section 9 Filter section 10 Power amplification section 11 Transmission antenna section 101 Coding section 102 Transmission filter Part 103 Transmission filter part 104 D / A part 105 D / A part 106 Filter part 107 Filter part 108 Quadrature modulation part 109 Frequency conversion part 110 Filter part 111 Power amplification part 112 Transmission antenna part

Claims (1)

[Claims] 1. A coding means for coding input data according to a signal point arrangement of a modulation system to generate orthogonal signal components I and Q components by digital signal processing, and a digital signal processing for an output of the coding means. Means for band limiting, means for quadrature modulating the I and Q component signals of the band limited output by digital signal processing, D / A converting means for converting the quadrature modulated signal output to an analog signal, and the D Filter means for removing unnecessary frequency components due to / A conversion,
SS for removing unnecessary frequency components due to the quadrature modulation
B modulation means, frequency conversion means for converting the SSB modulation output into an actually used radio frequency, filter means for removing unnecessary signals generated by the frequency conversion, and power amplification of the output of the filter means. A data transmission device comprising: means and means for radiating the power-amplified signal as a radio wave.