JP2001103102A - Transmitter and data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter-receiver where no AGC circuit of a voice wireless unit is malfunctioned and no error is caused in transmission information even when data are transmitted by the modulation system including amplitude modulation through the use of the voice wireless unit and to provide a transmission system employing the transmitter-receiver. SOLUTION: A level detector 7 detects a level of an output SB of a modulation circuit 1 and an LPF 8 extracts its low frequency component. Then a level inverting circuit 9 inverts its level. This signal SG is used to apply amplitude modulation to a carrier C from a carrier circuit 10 to generate a modulation wave SC whose frequency band is not overlapped with that of the modulation wave SB and whose amplitude is in proportion to an amplitude change of the modulation wave SB. The modulation wave SB to which the modulation wave SC is added is transmitted. A filter 11 eliminates the modulation wave SC from an output of a receiver 3 and the resulting signal is demodulated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method for performing data communication using a voice transceiver, and a transceiver for the same.

[0002]

2. Description of the Related Art Portable radios such as cellular phones and PHSs
Although the transmitting / receiving means for voice communication is used, data transmission is also performed by adding a modem or the like to the transmitting / receiving means for voice communication. FIG. 7 shows a functional configuration of a transceiver when performing such data transmission. Data is converted by a modulation circuit 1 into a modulated wave SB obtained by amplitude-modulating a carrier in a voice band. And transmitted as a radio modulated wave SR. On the receiving side, the sound wave 3 is converted into a modulated wave SB in the sound band by the sound receiver 3 and is demodulated into a data signal by the demodulation circuit 4. Each of the audio transmitter 2 and the audio receiver 3 is provided with an AGC circuit for keeping the output signal level within a predetermined range.

[0003]

FIG. 8 shows an example of the waveform of a modulated wave SB obtained by amplitude-modulating a carrier in a voice band by input data. A portion where the amplitude of the carrier exceeds ± Lo is represented by data “ 1 and within ± L correspond to data “0”. Even if there is such a fluctuation in the amplitude of the modulated wave SB, if the fluctuation is within the frequency band of the audio signal, the AGC of the transceiver 2/3 hardly works, and the fluctuation is input to the demodulation circuit 4 as it is, The data is demodulated. However, data "0" or "1" may continue for a long time in some cases. For example, “0” continues during the time T in FIG. 8, and if this is a long time exceeding the time constant of AGC, the AGC of the transmitter / receiver operates, and the output signal of the audio receiver 3 becomes as shown in FIG. To change. Then, in the section T1 of FIG. 9, even if the data is “0”, the amplitude thereof exceeds the threshold Lo, and there is a problem that the demodulation circuit 4 determines that the data is “1”. Such a problem can occur when data modulation is accompanied by amplitude modulation. For example, it occurs when data transmission is performed using a voice communication line using a simple amplitude modulation or a modulation method such as 16QAM.

An object of the present invention is to provide a transmission method and a transceiver for delaying data accurately without being affected by an AGC circuit even when data is transmitted by amplitude modulation using a voice radio. To provide.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a transmitter / receiver having a transmitter and a receiver having an AGC function for voice communication, wherein a carrier in a voice band is modulated by a data signal by a method involving amplitude modulation. A modulation circuit for generating a modulated wave, a level detection circuit for detecting an amplitude level of the modulated wave output from the circuit, and a first circuit for extracting only a low-frequency component from an output of the circuit. A low-pass filter having a frequency as a cutoff frequency, a level inverting circuit for inverting the level of the output of the low-pass filter, a sub-carrier generating circuit for outputting a sub-carrier having a second frequency, A sub-modulation circuit for amplitude-modulating a sub-carrier by the level inversion circuit output to generate a sub-modulation wave, and adding the output of the modulation circuit and the output of the sub-modulation circuit An addition circuit for inputting to the transmitter, a reception filter for removing the sub-modulated wave from the output of the receiver, and a demodulation circuit for demodulating the output of the filter to extract a data signal, and The first frequency and the second frequency are set such that the frequency band of the modulated wave and the frequency band of the sub-modulated wave do not overlap, and the frequency band of the sub-modulated wave is within the pass band of the transmitter and the receiver. Disclosed is a transceiver characterized by the certain definition.

Further, the present invention relates to a data transmission method using a transmitter and a receiver having an AGC function for voice communication, wherein the amplitude level of a modulated wave modulated by a method involving amplitude modulation by a data signal is provided. A signal obtained by detecting and extracting the low-frequency component, amplitude-modulating a sub-carrier with a signal obtained by inverting the level of the low-frequency component to generate a sub-modulation wave, and adding the sub-modulation wave to the modulation wave Is transmitted by the transmitter, and on the receiving side, after receiving the transmission signal, removing the sub-modulation wave with a filter and demodulating the data signal, the frequency bands of the modulation wave and the sub-modulation wave do not overlap and A data transmission method is disclosed, wherein a frequency band of the sub-modulated wave is within a pass band of the transmitter and the receiver.

Further, according to the present invention, the amplitude of the sub-modulation wave is
3. The transmission method according to claim 2, wherein when added to the modulated wave, the amplitude change of the modulated wave is determined to be canceled.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a transceiver according to the present invention. In FIG. 1, the same reference numerals are used for those which are the same as those in the conventional transceiver shown in FIG. 7, and overlapping descriptions are omitted.

On the transmitting side, the output terminal of the modulation circuit 1 is connected to one input terminal of an addition circuit 5, the other input terminal is connected to the output terminal of a multiplication circuit 6, and the output terminal of the addition circuit 5 The terminal is connected to the audio transmitter 2.
A level detector 7 is connected to an output terminal of the modulation circuit 1. An LPF (Low Pass Filter) is provided between the level detector 7 and one input terminal of the multiplication circuit 6.
r: low-pass filter) 8 and a level inverting circuit 9 are connected in series. The other input terminal of the multiplication circuit 6 is connected to a carrier generation circuit 10. On the receiving side, a filter 11 is inserted between the audio receiver 3 and the demodulation circuit 4.

FIG. 2 shows general frequency characteristics of a voice communication line. The usable frequency band is the frequency FL1 to FH1.
Communication band 20, whereas the modulation wave band 21
(Frequencies FL2 to FH2) are often set with a margin. Therefore, on both sides of the modulated wave band 21, there are end use bands 22a (frequency FL1 to FL2) and 22b (frequency FH2 to FH1). Therefore, in the present invention, the amplitude correction information is transmitted using the last use band 22a or 22b, and the above-mentioned amplitude component is complemented to eliminate the bias of the amplitude component so that the AGC circuit does not malfunction. For this purpose, the level detector 7 detects the level (amplitude) L of the modulation wave SB output from the modulation circuit having a waveform as shown in FIG. The detected level signal SL has an amplitude L proportional to the amplitude of the modulated wave SB as shown in FIG. This signal SL is input to the LPF 8, and its cut-off frequency is (FL2-FL1) / 2 or (FH2-FH).
1) / 2 is set. The output signal SF of the LPF 8 is input to the level inversion circuit 9, and the signal is inverted in magnitude. As shown in FIG. 4, the level inversion circuit 9 outputs a signal SG having a voltage characteristic such that the output value decreases when the level of the modulation signal is high. In this case, when the modulation wave is output from the modulation circuit 1 with the maximum amplitude, the level inversion circuit 9
Is set so that the level (voltage) output from the terminal becomes zero.

The carrier generation circuit 10 includes an unused band 22.
A carrier wave C having the center frequencies of a and 22b is generated and applied to the multiplication circuit 6. The frequency of the carrier C is (FL1 + FL2) / 2 or (FH1 + FH) / 2 when the unused band 22a or 22b in FIG. 2 is used. The multiplying circuit 6 modulates the amplitude of the carrier C with the output signal SG from the level inverting circuit 9 and sends the modulated wave SC to the adding circuit 5. The frequency band of this modulated wave SC is
From the frequency of the carrier C and the cutoff frequency of the LPF 8,
As shown in FIG. 5, just the unused band 22a or 22b
Inside. Therefore, even if this is added to the data modulation wave SB by the adding circuit 5, the frequency is separated and the characteristics of data transmission do not deteriorate. On the other hand, considering the waveform on the time axis of each signal, the result is as shown in FIG. That is, the modulated wave SB as shown in FIG.
, The modulated wave SC outputted from the multiplication circuit 6 has the output level L of the modulated wave SB as shown in FIG.
The smaller the is, the larger the amplitude. If the amplitude of the modulated wave SC is appropriately adjusted, the output signal S
S can be made to have a substantially constant amplitude as shown in FIG. For this reason, the AGC of the transmitter 2 and the receiver 3 often changes the gain particularly, considering that the input is almost constant.

On the receiving side that has received the signal transmitted from the audio transmitter 2 as described above, the signal from the audio receiver 3 is input to the filter 11, where the modulated wave SC is removed. The filter 11 for this purpose includes an unused band 22a.
Is a high-pass filter using FL2 as a cutoff frequency when using the frequency band, and a low-pass filter using the frequency FH2 as a cutoff frequency when using the unused band 22b. The signal input to the demodulation circuit 4 after the removal of the modulated wave SC component has the waveform shown in FIG. 6A, and even when digital data transmission is performed by a modulation method involving amplitude modulation using a voice radio. An error does not occur in transmission information due to AGC.

[0013]

As described above, according to the present invention, when amplitude-modulated data is transmitted using a voice transceiver, the fluctuation of the amplitude component in the AGC is complemented simultaneously with the modulated wave of the data. Data transmission using a wireless transceiver (transmitter / receiver) for voice communication without the need for a wireless transceiver dedicated to data or a wireless transceiver having a data mode. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a transceiver according to the present invention.

FIG. 2 is a frequency characteristic diagram showing a frequency band of a general modulated wave.

FIG. 3 is a characteristic diagram of an output signal of the level detector of FIG.

FIG. 4 is a characteristic diagram of an output signal of the level inversion circuit of FIG. 1;

FIG. 5 is a diagram illustrating a spectrum of an output signal of the multiplication circuit of FIG. 1;

FIG. 6 is a waveform chart of each part showing the operation of the transceiver of FIG. 1;

FIG. 7 is a block diagram showing a conventional transceiver.

FIG. 8 is a modulation signal waveform diagram when a data signal is amplitude-modulated by a voice radio device.

FIG. 9 is a diagram illustrating an example of a signal waveform after the modulation signal of FIG. 8 has passed through an AGC circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Modulation circuit 2 Audio transmitter 3 Audio receiver 4 Demodulation circuit 5 Addition circuit 6 Multiplication circuit 7 Level detector 8 LPF 9 Level inversion circuit 10 Carrier generation circuit 11 Filter

Claims (3)

[Claims] A transmitter and receiver having an AGC function for voice communication and a receiver having an AGC function for generating a modulated wave by modulating a carrier in a voice band by a method involving amplitude modulation by a data signal. A modulation circuit; a level detection circuit for detecting an amplitude level of a modulated wave output from the circuit; and a first detection circuit for extracting only low-frequency components from an output of the circuit.
A low-pass filter having a cut-off frequency as a cut-off frequency; a level inverting circuit for inverting the level of the output of the low-pass filter; a sub-carrier generating circuit for outputting a sub-carrier having a second frequency; A sub-modulation circuit for amplitude-modulating the sub-carrier by the level inversion circuit output to generate a sub-modulation wave, and adding the output of the modulation circuit and the output of the sub-modulation circuit to input to the transmitter. An adding circuit, a receiving filter for removing the sub-modulated wave from the output of the receiver, and a demodulating circuit for demodulating the output of the filter to extract a data signal; and providing the first frequency and the second The frequency of the modulated wave and the frequency band of the sub-modulated wave do not overlap, and the frequency band of the sub-modulated wave is the pass band of the transmitter and the receiver. Transceiver characterized in that defined as in. 2. A data transmission method for performing transmission using a transmitter and a receiver having an AGC function for voice communication, comprising detecting an amplitude level of a modulated wave modulated by a method involving amplitude modulation by a data signal. The low-frequency component is taken out, the sub-carrier is amplitude-modulated with a signal obtained by inverting the level of the low-frequency component to generate a sub-modulation wave, and a signal obtained by adding the sub-modulation wave to the modulation wave is transmitted. After receiving this transmission signal, the receiving side removes the sub-modulated wave with a filter and demodulates the data signal. The frequency band of the modulated wave and the sub-modulated wave do not overlap and the sub-modulation is performed. A data transmission method, wherein a frequency band of a wave is within a pass band of the transmitter and the receiver. 3. The transmission method according to claim 2, wherein when the amplitude of the sub-modulation wave is added to the modulation wave, a change in the amplitude of the modulation wave is canceled.