JPH11154986A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a digital modulator to be used for a communication system by simple circuit constitution or soft processing by controlling a sampling frequency by the center frequency of the desired channel of a received signal to convert the center frequency of the signal after sampling to a specific frequency which exists at the time of setting the sampling frequency to be a reference. SOLUTION: An A/D converter 21 converts an analog reception signal 19 into a digital reception signal 22 according to the timing of a reception sampling pulse oscillator 20. The oscillator 20 is controlled by a received frequency control signal 18 so that the center frequency of the signal 22 becomes 1/4 of a sampling frequency. In this case, processing for converting the frequency to a same phase and an orthogonal phase is executed by simple processing being alternate separation and code inversion of every other sample to unnecessitate a multiplier and also, the oscillator generating the sampling frequency is not required to generate a sine wave to remarkably reduce a circuit scale.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device for digital communication.

[0002]

2. Description of the Related Art At present, digitization is rapidly performed on a quadrature modulation / demodulation part of a communication system having a plurality of channels.

FIG. 4 shows a conventional digital demodulator. The analog reception signal 1 is sampled by the A / D converter 2 and converted into a digital reception signal. The sampling frequency is usually constant regardless of the frequency of the analog reception signal 1. Since the digital reception signal is converted to a different center frequency depending on the desired channel, in order to convert the digital reception signal into a baseband signal, a digital oscillator that generates a sine wave of a variable frequency controlled by the center frequency of the desired channel 3, and are converted into an in-phase baseband reception signal and a quadrature baseband reception signal by multipliers 4 and 5. Then, after appropriate filter processing is performed by the reception filter unit 6, the reception data 8 is reproduced by the data demodulation unit 7.

FIG. 5 shows a conventional digital modulator. The transmission data 9 is quadrature-modulated by the data modulator 10 and converted into an in-phase baseband transmission signal and a quadrature baseband transmission signal.
After that, the digital oscillator 12 generates a controlled variable frequency sine wave and the multipliers 13 and 14 so that the signal has the center frequency of the desired channel after the analog conversion. , D / A converter 1
At 5, an analog transmission signal 16 is obtained.

[0005]

However, in the conventional communication apparatus described above, a sine wave of a variable frequency must be generated as a digital oscillator, and a digital multiplier is required as a mixer. Or required complicated software processing.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a communication device which realizes a digital modulation / demodulation device used in a communication system with a simple circuit configuration or software processing.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention controls the sampling frequency according to the center frequency of a desired channel of a received signal, so that the center frequency of the sampled signal is based on the sampling frequency. If the specific frequency is exactly 1/4 of the sampling frequency, the processing required to convert the signal to the in-phase and quadrature signals is alternate separation and alternate sign inversion. It does not require a multiplier, and the oscillator that generates the sampling frequency does not need to generate a sine wave,
The circuit scale can be significantly reduced.

[0008]

According to the first aspect of the present invention, a center frequency of a desired channel reception signal after sampling an orthogonally modulated analog reception signal is a specific frequency based on a sampling frequency. A reception frequency control unit that generates a reception frequency control signal, a reception sampling pulse oscillator that generates a sampling pulse whose frequency is controlled by the reception frequency control signal, and an analog reception signal at the output timing of the reception sampling pulse oscillator. An A / D converter for converting to a digital reception signal; and alternately allocating the digital reception signal to an in-phase digital reception signal and a quadrature digital reception signal. By inverting, the in-phase baseband received signal A reception frequency conversion unit that converts the received signal into an interleaved baseband reception signal, and performs in-phase baseband filtered signal and quadrature baseband by filtering the in-phase baseband reception signal and the quadrature baseband reception signal for the purpose of thinning and waveform shaping A communication device comprising: a reception filter unit that generates a filtered signal; and a data demodulation unit that demodulates received data from the in-phase baseband reception filtered signal and the quadrature baseband reception filtered signal. By controlling the sampling frequency according to the center frequency of the desired channel of the received signal, the center frequency of the sampled signal is converted to a specific frequency when the sampling frequency is used as a reference, and the specific frequency is just the sampling frequency. In the case of 1/4, to convert to in-phase and quadrature signals Does not require a can be multipliers be essential processing is performed with a simple process of alternating separation and every other sample sign inversion. Also, the oscillator that generates the sampling frequency does not need to generate a sine wave. As a result, the circuit scale can be greatly reduced, and channel selection can be performed with a simple circuit configuration or software processing.

The invention according to claims 2, 3, 4, and 5 of the present invention detects the frequency error of the center frequency of the received signal, and controls the sampling frequency so as to cancel the frequency error, thereby obtaining the signal after sampling. The data is converted to a specific frequency when the sampling frequency is used as a reference, and the specific frequency is exactly 1/1 of the sampling frequency.
In the case of No. 4, processing required for conversion into in-phase and quadrature-phase signals can be performed by simple processing of alternate separation and sign inversion every other sample, and a multiplier is not required. Further, the oscillator that generates the sampling frequency does not need to generate a sine wave, and the circuit scale can be significantly reduced.

According to a sixth aspect of the present invention, there is provided a transmission frequency control section for generating a transmission frequency control signal for adjusting a center frequency of an analog transmission signal, and the frequency is controlled by the transmission frequency control signal. A transmission sampling pulse oscillator, a data modulation unit that performs quadrature modulation on transmission data to generate an in-phase baseband transmission signal and a quadrature baseband transmission signal, and performs interpolation and interpolation on the in-phase baseband transmission signal and the quadrature baseband transmission signal. A transmission filter unit that performs a filtering process for the purpose of waveform shaping to generate an in-phase baseband transmission filtered signal and a quadrature baseband transmission filtered signal, and the in-phase baseband transmission filtered signal and the quadrature baseband transmission filtered signal, respectively. A specific center frequency is obtained by inverting the sign every other sample and then arranging them alternately. And a D / A converter that converts a digital transmission signal into an analog transmission signal at the output timing of the transmission sampling pulse oscillator. According to the configuration, the sign inversion of every other sample is performed on the baseband signal obtained by modulating the transmission data, and then the data is converted into a specific frequency based on the sampling frequency by alternate mixing. Here, by controlling the sampling frequency according to the desired center frequency of the transmission signal, the center frequency of the signal after D / A conversion can be generated at the desired frequency, and a multiplier is not required for frequency conversion. The oscillator that generates the sampling frequency does not need to generate a sine wave, and the digital modulation can be realized with a simple circuit configuration or software processing that can greatly reduce the circuit scale.

An embodiment of a communication device according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a receiving / demodulating unit of a communication apparatus according to the present invention. In FIG. 1, 17 is a reception frequency control unit, 18 is a reception frequency control signal, 19 is an analog reception signal, 20 is a reception sampling pulse oscillator, 21 is an A / D converter, 22 is a digital reception signal,
Reference numeral 3 denotes a reception frequency conversion unit. 24 is an in-phase baseband reception signal, and 25 is a quadrature baseband reception signal. 2
Reference numeral 6 denotes a reception filter unit. 27 is an in-phase baseband reception filtered signal, and 28 is a quadrature baseband reception filtered signal. 29 is a data demodulation unit, and 30 is received data.

The operation of the demodulation device of the present invention configured as described above will be described below. The analog reception signal 19 is converted into a digital reception signal 22 by an A / D converter 21 in accordance with the timing of a reception sampling pulse oscillator 20.
Is converted to This digital reception signal 22 is x (n), the in-phase baseband reception signal 24 is i (n), and the quadrature baseband reception signal 25 is q (n). Assuming that the center frequency of the analog reception signal 19 is fr and the sampling frequency is fs, the in-phase baseband reception signal 24: i is obtained from x (n).
(n) and the conversion formula for converting the orthogonal baseband received signal 25 into q (n) are generally as shown in the following (Equation 1) and (Equation 2).

[0014]

(Equation 1)

[0015]

(Equation 2)

Fr varies with the desired receiving channel frequency or Doppler frequency. Here, the reception sampling pulse oscillator 20 is controlled by the reception frequency control signal 18 as shown in the following (Equation 3) so that the center frequency of the digital reception signal 22 becomes a specific frequency.

[0017]

(Equation 3)

The frequency fr is controlled as described above. At this time, the center frequency of the digital reception signal 22 is 1/1 of the sampling frequency determined by the sampling pulse oscillator 20.
The above (Equation 1) and (Equation 2) can be simplified as the following (Equation 4) and (Equation 5), respectively. ,

[0019]

(Equation 4)

[0020]

(Equation 5)

Both i (n) and q (n) do not change their characteristics even if 0 inserted every other sample is thinned out. Therefore, the finally obtained baseband reception signal is as shown in the following (Equation 6) and (Equation 7).

[0022]

(Equation 6)

[0023]

(Equation 7)

As a result, the digital reception signal 22 can be converted into a baseband signal only by thinning and code conversion.

As shown in FIG. 2, the digital reception signal 22 is converted into an in-phase baseband reception signal 24 and a quadrature baseband reception signal 25 by a reception frequency conversion unit 23 which performs the processing of (Equation 6) and (Equation 7). After being converted, the received signal is further filtered by the reception filter section 26 in-phase baseband reception filtered signal 27.
After being converted to the orthogonal baseband reception filtered signal 28, the reception data 30 is obtained by the data demodulation unit 29.

FIG. 3 is a block diagram of the modulation / transmission unit of the communication device according to the present invention. In FIG. 3, 31 is a transmission frequency control unit, and 32 is a transmission frequency control signal. 33 is transmission data. Numeral 34 denotes a data modulator for performing quadrature modulation on transmission data 33, from which an in-phase baseband transmission signal 35 and a quadrature baseband transmission signal 36 are output.

Reference numeral 37 denotes a transmission filter section for the purpose of interpolation and waveform shaping. The in-phase and quadrature baseband transmission signals are passed through the transmission filter section 37 to form an in-phase baseband transmission filtered signal 38 and a quadrature baseband signal. A transmission filtered signal 39 is obtained. 40 is a transmission frequency converter,
41 is a digital transmission signal, and 42 is a transmission sampling pulse oscillator. 43 is a D / A converter, and 44 is an analog transmission signal.

The transmission data 33 is quadrature-modulated by the data modulator 34 to generate an in-phase baseband transmission signal 35 and a quadrature baseband transmission signal 36. Thereafter, the filter processing for the purpose of interpolation and waveform shaping is performed by the transmission filter unit 3.
7 to generate an in-phase baseband transmit filtered signal 38 and a quadrature baseband transmit filtered signal 39. Let the in-phase baseband transmit filtered signal 38 be ii (n) and the quadrature baseband transmit filtered signal 39 be qq (n). Assuming that the digital transmission signal 41 is y (n), the conversion equations are as shown in the following (Equation 8) and (Equation 9).

[0029]

(Equation 8)

[0030]

(Equation 9)

As shown in (Equation 8) and (Equation 9), the transmission frequency conversion unit 40 performs a process of alternately arranging codes while inverting them every other sample. By performing such processing in the transmission frequency conversion unit 40, a digital transmission signal 41 having a center frequency of 1/4 of the sampling frequency is obtained. The digital transmission signal 41 is converted by the D / A converter 43 to obtain an analog transmission signal 44.

Here, the transmission sampling pulse oscillator 4
The transmission frequency 2 is controlled by the transmission frequency control signal 32 so that the center frequency of the analog transmission signal 44 becomes a predetermined frequency. In this way, the center frequency of the transmission signal occurs at the desired frequency.

As described above, according to the present invention, by controlling the sampling frequency in accordance with the center frequency of the received or transmitted signal, a digital sine wave oscillator and a digital multiplier are not required, so that the digital modulation / demodulation device can be simplified. It can be realized by a simple circuit configuration or software processing.

[0034]

As described above, according to the first aspect of the present invention, it is possible to realize a digital demodulator for performing channel selection with a simple circuit configuration or software processing.

As described above, claims 2, 3, 4,
According to 5, a digital demodulator that performs frequency compensation with a simple circuit configuration or software processing can be realized.

As described above, according to claim 6 of the present invention,
A digital modulation device can be realized with a simple circuit configuration or software processing.

As described above, according to claim 7 of the present invention,
With a simple circuit configuration or software processing, a digital modulation device that performs channel selection can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a reception / demodulation unit of a communication device according to the present invention.

FIG. 2 is an explanatory diagram illustrating processing of a reception frequency conversion unit of the communication device according to the present invention.

FIG. 3 is a configuration diagram showing a modulation / transmission unit of the communication device of the present invention.

FIG. 4 is a configuration diagram showing a conventional digital demodulation device.

FIG. 5 is a configuration diagram showing a conventional digital modulation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Analog reception signal 2 A / D converter 3 Digital oscillator 4 Multiplier 5 Multiplier 6 Reception filter part 7 Data demodulation part 8 Reception data 9 Transmission data 10 Data modulation part 11 Transmission filter part 12 Digital oscillator 13 Multiplier 14 Multiplier REFERENCE SIGNS LIST 15 D / A converter 16 analog transmission signal 17 reception frequency control unit 18 reception frequency control signal 19 analog reception signal 20 reception sampling pulse oscillator 21 A / D converter 22 digital reception signal 23 reception frequency conversion unit 24 in-phase baseband reception signal Reference Signs List 25 quadrature baseband reception signal 26 reception filter unit 27 in-phase baseband reception filtered signal 28 quadrature baseband reception filtered signal 29 data demodulation unit 30 reception data 31 transmission frequency control unit 32 transmission frequency control signal 33 transmission data 34 data modulation unit 35 Phase baseband transmission signal 36 Quadrature baseband transmission signal 37 Transmission filter unit 38 In-phase baseband transmission filtering signal 39 Quadrature baseband transmission filtering signal 40 Transmission frequency conversion unit 41 Digital transmission signal 42 Transmission sampling pulse oscillator 43 D / A conversion Instrument 44 Analog transmission signal

Claims (7)

[Claims] A reception frequency control unit for generating a reception frequency control signal such that a center frequency of a desired channel reception signal after sampling an orthogonally modulated analog reception signal is a specific frequency based on a sampling frequency; A reception sampling pulse oscillator that generates a sampling pulse whose frequency is controlled by the reception frequency control signal; and an A / D converter that converts the analog reception signal into a digital reception signal at an output timing of the reception sampling pulse oscillator. The digital received signal is alternately divided into an in-phase digital received signal and a quadrature digital received signal, and the in-phase digital received signal and the quadrature digital received signal are each set to 1
A reception frequency conversion unit that converts the in-phase baseband reception signal and the quadrature baseband reception signal by inverting the sign every sample, and thinning and waveform shaping for the in-phase baseband reception signal and the quadrature baseband reception signal. A receiving filter unit that performs a filtering process for generating an in-phase baseband filtered signal and a quadrature baseband filtered signal, and demodulates received data from the in-phase baseband received filtered signal and the quadrature baseband received filtered signal. A communication device comprising a data demodulation unit. 2. A reception frequency control unit detects a frequency error of a center frequency of an analog reception signal from an analog reception signal and reception data, and cancels the error to specify a center frequency of a desired reception signal based on a sampling frequency. The communication device according to claim 1, wherein the reception frequency control signal is generated such that the frequency becomes the frequency of the communication frequency. 3. A reception frequency control unit detects a frequency error of a center frequency of an analog reception signal from a digital reception signal and reception data, and cancels the error to specify a center frequency of a desired reception signal based on a sampling frequency. The communication device according to claim 1, wherein the reception frequency control signal is generated such that the frequency becomes the frequency of the communication frequency. 4. A reception frequency control unit detects a frequency error of a center frequency of an analog reception signal from an in-phase baseband signal, a quadrature baseband signal, and reception data, and cancels the error to thereby obtain a center frequency of a desired channel reception signal. 2. A reception frequency control signal is generated so as to have a specific frequency based on a sampling frequency.
The communication device as described. 5. A reception frequency control unit detects a frequency error of a center frequency of an analog reception signal from an in-phase baseband filtered signal, a quadrature baseband filtered signal, and received data, and cancels the error to thereby obtain a desired channel reception signal. 2. The communication apparatus according to claim 1, wherein the reception frequency control signal is generated such that the center frequency of the received signal becomes a specific frequency based on the sampling frequency. 6. A transmission frequency control section for generating a transmission frequency control signal for adjusting a center frequency of an analog transmission signal, a transmission sampling pulse oscillator whose frequency is controlled by the transmission frequency control signal, A data modulation unit that performs quadrature modulation to generate an in-phase baseband transmission signal and a quadrature baseband transmission signal; and performs a filtering process on the in-phase baseband transmission signal and the quadrature baseband transmission signal for the purpose of interpolation and waveform shaping. A transmission filter unit that generates an in-phase baseband transmission filtered signal and a quadrature baseband transmission filtered signal, and inverts a sign of the in-phase baseband transmission filtered signal and the quadrature baseband transmission filtered signal every other sample. Then, by alternately arranging, a digital transmission signal having a specific center frequency A transmission frequency converter for converting, at an output timing of the transmission sampling pulse oscillator, a communication apparatus characterized by comprising a D / A converter for converting the digital transmission signal to said analog transmission signal. 7. A transmission frequency control unit generates a transmission frequency control signal such that a center frequency of an analog transmission signal obtained by converting a digital transmission signal into an analog signal is converted into a predetermined channel frequency. The communication device according to claim 6.