JPH04349740A - Transmission system for composite modulation wave - Google Patents

Abstract

PURPOSE:To bring the adverse effect of composite modulation onto a carrier lock time to endlessly zero when the synchronization detection system is adopted for an orthogonal phase detection means of a composite modulation wave and to establish the synchronization system between a main data signal and a sub data signal. CONSTITUTION:A sub data transmission signal is sent in a frame form consisting of a preamble signal SP giving sub data control information with phase modulation alpha=0, of a unique word signal UW to synchronize a sub data signal and a main data signal, and of the sub data, and a demodulator side establishes the frame synchronization of the sub data when the unique word signal UW included in the sub data series is detected to eliminate a phase ambiguity of the main data signal and the sub data signal, and the phase of the carrier is synchronized quickly in the case of the preamble signal SP and in the case of the undetected unique word signal UW.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for performing composite transmission by phase modulating a sub data signal on a main data line using orthogonal amplitude modulation, and main data signal system processing and sub data signal system processing in a composite modulation/demodulation device. Regarding the synchronization method.

0002

2. Description of the Related Art Recently, it has become common practice to transmit a main data signal and a sub data signal in a composite manner. Such a composite transmission system is explained in detail in, for example, "Demodulator" (February 4, 1988, Patent Application No. 5218000). The outline will be explained below with reference to FIGS. 3 to 5.

FIG. 3 is a signal arrangement diagram of a composite modulated wave obtained by phase-modulating a 16-value orthogonal amplitude modulated wave with a sub data signal, and shows 16 signal points Cij (i, j are 1 to 1) corresponding to the main data signal. 4) is converted into a signal point Aij or a signal point Bij by phase modulation of ±α radians using a sub data signal. Here, α radian is the angular displacement amount excluding 0,
P and Q are coordinate axes.

FIG. 4 is an explanatory diagram of a sub-data transmission system for forming such a composite modulated wave. Referring to this figure, the sub data is transmitted at the same time as the sub data is turned ON, and the OF
The transmission is stopped at the same time as F. That is, the sub data transmission signal transmits only sub data.

FIG. 5 shows a 16QAM-2PSK system for reproducing main data signals and sub data signals from composite modulated waves.
FIG. 1 is a block diagram of a composite modulation and demodulation system.

In the figure, 1 is an intermediate frequency amplifier that amplifies the input signal IN, 2 is a voltage controlled oscillator (VCO), 3 is a quadrature phase detector that outputs two demodulated signals PO and QO, and 4 is a quadrature phase detector that outputs two demodulated signals PO and QO.
, 5 is a baseband amplifier that amplifies each demodulated signal PO , QO , and 6 and 7 are A/7 that converts the output of each baseband amplifier 4 and 5 into digital demodulated data Dp and Dq, respectively.
It is a D converter. Further, 8 is a sub data signal reproducing circuit that inputs the demodulated data Dp, Dq and performs a logical operation to reproduce the sub data signal S, and 9 is a sub data signal reproducing circuit that removes the phase modulation component by the sub data signal S from the demodulated data Dp, Dq ( This is a main data signal reproducing circuit that reproduces main data signals X1, X2, Y1, Y2 and data signals X3, Y3 by performing ±α inverse phase conversion). Each of the signal reproducing circuits 8 and 9 includes a logic section and a digital calculation section.

The main data signals X1 and X2 are signals that determine the position of the signal point Cij in the P-axis direction, and the main data signals Y1 and
Y2 is a signal that determines the position of the signal point Cij in the Q-axis direction (X1 and Y1 determine the quadrant). In addition, the data signal
, Y3 are signals representing deviations of the input signals of the A/D converters 6 and 7 from normal values.

A low-pass filter (LPF) 10 controls the output DC level of the baseband amplifiers 4 and 5 with signals obtained by low-pass filtering the data signals X3 and Y3, respectively. This compensates for the drift of the DC component of the input signals of the A/D converters 6 and 7. Regarding the operation of drift compensation,
It is described in detail in "Demodulator" (Japanese Patent Laid-Open No. 101449/1983).

Logic circuits 11 and 12 receive main data signals X1 and Y1 and data signals X3 and Y3, respectively. One logic circuit 11 controls the gains of the intermediate frequency amplifier 1 and the baseband amplifier 5 to control the A/D
The amplitudes of the input signals to the converters 6 and 7 are maintained at normal values. Its configuration and operation are known as "automatic gain control circuit" (Japanese Patent Laid-Open No. 59-1
No. 69256). Further, the other logic circuit 12 has V
Control CO2 to form a phase-locked loop. Its configuration is "carrier regeneration circuit" (Japanese Patent Application Laid-Open No. 57-131151)
by. Since the main data signal and the sub data signal are synchronized by the LPF 10 and the logic circuits 11 and 12, it is not always necessary to synchronize the main data signal and the sub data signal during transmission.

By the way, in a complex modulated wave transmission system, the identification margin for the sub data signal is usually smaller than the identification margin for the main data signal, so if the code transmission speeds of both data signals are the same, code errors in the sub data signal will occur. The rate characteristics deteriorate, and the reproduction error rate of the main data signal also increases accordingly. Therefore, the code transmission rate of the sub data signal is modulated by limiting it to 1/m (integer) of the code transmission rate of the main data signal, and when demodulating, the sub data signal reproducing circuit 8 performs addition m times to encode the code. Regenerates sub data signals with low error rate. ing. 1
In the case of 6 values, the value of m can be suppressed to about 8.

Further, as the value of α increases, the bit error rate of the sub data signal improves, but on the other hand, the bit error rate characteristic of the main data signal worsens, so there is a limit to its value. 1
In the case of 6 values, it is about 0.16 radian, and in this case it varies depending on the signal point, but at the best point it is about 6 radians for the main data.
The amount of C/N deterioration is about dB.

[0012] By using the above-described composite transmission system and demodulation device, the bit error rate characteristics of the sub data signal S reproduced by the sub data signal reproducing circuit 8 can be sufficiently improved by appropriately selecting the values of α and m. Can be done. Further, the main data signal reproducing circuit 9 removes the phase modulation component caused by the sub data signal S from the demodulated data Dp, Dq, and generates the main data signals X1, Dq.
Since X2, Y1, and Y2 are reproduced, the bit error rate characteristics are not degraded due to phase modulation by the sub data signal S.

[0013]

SUMMARY OF THE INVENTION As described above, although the conventional complex modulated wave transmission system has the excellent effect of being able to perform transmission without reducing the bit error rate, the following problems remain.

That is, if a synchronous detection method is used for orthogonal phase detection of a complex modulated wave, the carrier wave pull-in time becomes long, and in the worst case, the pull-in itself becomes impossible.

[0015] Furthermore, in the modulation/demodulation device, a synchronization method for the main data signals X1, Sometimes, it was not possible to quickly synchronize the phases of the two as soon as the received signal was restored.

The present invention has been made to solve the above problems, and its purpose is to solve the problem even when a synchronous detection method is used as the orthogonal phase detection means for complex modulated waves.
It is an object of the present invention to provide a transmission system for a complex modulated wave, which can reduce or eliminate the adverse effect of complex modulation on the pull-in time of a carrier wave, and establish a synchronization system between a main data signal and a sub data signal.

[0017]

[Means for Solving the Problems] The configuration of the present invention to achieve the above object is to transmit a quadrature amplitude modulated wave that has been phase-modulated with a main data signal, further phase-modulated with a sub-data signal, and to transmit these waves. A sub data signal reproducing means inputs a complex modulated wave formed by complex phase modulation, performs quadrature phase detection, and reproduces a sub data signal based on the detected output signal, and a detection output signal and a sub data signal reproducing means output. In the composite modulated wave transmission method, the orthogonal amplitude modulated wave is modulated with a phase of 0 radian and transmitted when the sub data is OFF, and when the sub data is ON. , a preamble signal giving sub data control information of 0 radian, and ±α for removing phase ambiguity between the main data signal and the sub data signal.
Transmitting a composite modulated wave phase-modulated with a sub data signal frame consisting of a unique word signal having a phase modulation degree of radians (predetermined phase shift amount other than 0) and sub data having a phase modulation degree of ±α radians; , on the demodulation side,
When a unique word signal is detected by the sub data signal reproducing means, sub data signal frame synchronization is established to remove the phase ambiguity between the main data signal and the sub data signal. In this case, a sub data signal frame synchronization circuit is provided which synchronizes the phase of the carrier wave assuming that there is no phase modulation by the sub data signal, and the output of this data signal frame synchronization circuit is guided to the main data signal reproducing means, thereby performing composite modulation. The present invention is characterized in that the pull-in time of the carrier wave is brought as close to zero as possible, and furthermore, the main data signal and the sub data signal are quickly synchronized.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a complex modulated wave transmission system according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the sub data transmission method used in this embodiment.

The present invention is similar to the conventional method in that 16-value orthogonal amplitude modulation is used as the modulation method for the main data signal, and the code transmission rate of the sub data signal is set to 1/m of the code transmission rate of the main data signal. In this embodiment, the sub data signal is transmitted using a frame as shown in FIG.

That is, when the sub data is OFF, the 16-value orthogonal amplitude modulated wave is subjected to 0 radian phase modulation (α
=0). On the other hand, when the sub data is ON, the phase modulation degree α
The sub data is transmitted based on a frame consisting of a preamble signal Sp giving sub data control information of =0 radian, a unique word signal UW for synchronizing the main data signal and the sub data signal, and sub data.

[0022] The preamble signal Sp is used for the purpose of high-speed phase synchronization of the carrier wave in the demodulator of the synchronous detection method, and in order to set the signal point of the 16-value orthogonal amplitude modulated wave at the normal position.
The value orthogonal amplitude modulated wave is modulated with a phase of 0 radian using the sub data signal S.

The unique word signal UW performs ±α radian phase modulation of the 16-value orthogonal amplitude modulated wave with the sub data signal S based on the unique word signal for removing phase ambiguity between the main data signal and the sub data signal.

As for the sub data, the 16-value orthogonal amplitude modulated wave is subjected to ±α radian phase modulation with the sub data signal S. Here, α radian is a predetermined phase shift amount excluding 0.

FIG. 2 is a block diagram of a demodulator using the complex modulated wave transmission system of this embodiment. Since this demodulator is a partially modified version of the conventional demodulator, components that are the same as those of the conventional demodulator will be given the same reference numerals and explanations will be omitted, and the explanation will focus on the different parts.

In FIG. 2, the input signal IN is the main data signal
The 16-value orthogonal amplitude modulation wave modulated by 1, The signal points are Aij, Bij, and Cij in FIG. 3.

This input signal IN is amplified to a predetermined amplitude by an intermediate frequency amplifier 1, and quadrature phase detected by a quadrature phase detector 3 using the output of the VCO 2 as a reference phase. At this time, the phase synchronization of the carrier wave is performed reliably and quickly by the preamble signal despite the complex modulated wave. Therefore, when the synchronous detection method is used as the quadrature phase detection means, the carrier wave pull-in time can be significantly shortened compared to the conventional method.

The demodulated outputs PO and QO are amplified by baseband amplifiers 4 and 5, and then sent to A/D converters 6 and 7 to obtain at least 2 more bits than the minimum number of bits required for determining the main data signal.
Multi-value identification is performed with identification resolution of a large number of bits, and the data is converted into demodulated data Dp and Dq. This demodulated data Dp,
The greater the number of bits for Dq, the better the accuracy of subsequent signal processing, but in the case of 16 values, about 8 bits is sufficient.

The sub data signal reproducing circuit 8 reproduces the sub data frame and outputs it to the sub data signal frame synchronization circuit 13.

When the sub data frame synchronization circuit 13 detects a unique word signal from the reproduced sub data frame, it establishes sub data frame synchronization and removes the phase ambiguity between the main data signal and the sub data signal. A sub data signal S is output.

The logic circuit of the main data signal reproducing circuit 9 outputs coefficient data in response to the output signal of the sub data signal frame synchronization circuit 13, but only when the sub data signal S is a preamble or when a unique word is not detected. is processed on the assumption that there is no phase modulation caused by the sub data. In other words, it outputs three-state coefficient data. The digital arithmetic circuit digitally calculates the coefficient data and the demodulated data Dp, Dq to generate the sub data signal S from the demodulated data Dp, Dq.
removes the phase modulation component caused by The most significant bit and second-order bit of the two data thus obtained are main data X1, Y1 and X2, Y2, and the third-order bit is X3, Y3.

As in the conventional case, X1, X3, Y1, and Y3 are inputted to the LPF 10 and the logic circuits 11 and 12, and guided to the baseband amplifiers 4 and 5, the intermediate frequency amplifier 1, and the VCO 2, respectively.

[0033] In such a demodulator, by reproducing the preamble signal and performing phase synchronization of the carrier wave reliably and quickly, the adverse effect on the carrier wave pull-in time due to composite modulation can be reduced to zero. Furthermore, as an effect of the unique word signal, even in the event of a line failure such as a loss of the received signal, the received signal can be recovered and the phases of the sub data signal and the main data signal can be quickly synchronized.

[0034]

As described in detail above, in the present invention, the sub data signal is synchronized with the preamble signal that provides sub data control information with a phase modulation degree α=0 radian, and the sub data signal and the main data signal. The demodulating side detects the unique word included in the sub data sequence, establishes frame synchronization of the sub data, and transmits the main data in a frame format consisting of a unique word signal and sub data. Since the phase ambiguity between the signal and the sub-data signal is removed, when a synchronous detection method is used as the orthogonal phase detection means for the complex modulated wave, the negative effect on the carrier wave pull-in time due to complex modulation can be reduced to zero. Furthermore, it is possible to provide a complex modulated wave transmission system that can establish a synchronization system between the main data signal and the sub data signal.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a sub data transmission method used in an embodiment of the present invention.

FIG. 2 is a configuration diagram of a demodulating device for a composite modulated wave according to an embodiment of the present invention.

FIG. 3 is a signal arrangement diagram of a composite modulated wave obtained by phase-modulating a 16-value orthogonal amplitude modulated wave with a sub data signal.

FIG. 4 is an explanatory diagram of a conventional sub data transmission method.

FIG. 5 is a configuration diagram of a conventional demodulating device for composite modulated waves.

[Explanation of symbols]

1...Intermediate frequency amplifier, 2...Voltage controlled oscillator (VCO),
3... Quadrature phase detector, 4, 5... Baseband amplifier,
6, 7... A/D converter, 8... Sub data signal regeneration circuit,
9...Main data signal regeneration circuit, 10...Low pass filter (LPF)
), 11, 12...Logic circuit, 13...Sub data signal frame synchronization circuit, Sp...Preamble signal, UW...Unique word signal.

Claims (2)

[Claims] 1. A composite modulated wave transmission method in which a quadrature amplitude modulated wave phase-modulated with a main data signal is further phase-modulated with a sub-data signal and transmitted, wherein the transmission speed of the sub-data signal is set to the main data signal. At the same time, when the sub data is OFF, the orthogonal amplitude modulated wave is transmitted with 0 radian phase modulation, while the sub data O
At time N, a preamble signal giving sub data control information of 0 radian and a phase modulation degree of ±α radian (a predetermined angular shift amount excluding 0) to remove phase ambiguity between the main data signal and the sub data signal. 1. A composite modulated wave transmission method, characterized in that a composite modulated wave whose phase is modulated with a sub data signal frame consisting of a unique word signal having a unique word signal having a phase modulation factor of ±α radians and sub data having a phase modulation degree of ±α radians is transmitted. Claim 2: A quadrature amplitude modulated wave phase-modulated with a main data signal is further phase-modulated with a sub-data signal and transmitted, and at the demodulation side, a composite modulated wave formed by these composite phase modulations is input. sub data signal reproducing means for performing quadrature phase detection and reproducing a sub data signal based on the detected output signal; and main data signal reproducing means for reproducing the main data signal based on the detection output signal and the output of the sub data signal reproducing means. In the composite modulated wave transmission method, the orthogonal amplitude modulated wave is transmitted with 0 radian phase modulation when the sub data is OFF, and a preamble signal that provides 0 radian sub data control information when the sub data is ON. ,
A unique word signal having a phase modulation degree of ±α radians (a predetermined phase shift amount excluding 0) for removing phase ambiguity between the main data signal and the sub data signal, and a phase modulation degree of ±α radians. When a unique word signal is detected by the sub data signal reproducing means, sub data signal frame synchronization is established and the main signal is transmitted to the demodulation side. A sub data signal frame synchronization circuit that removes the phase ambiguity between the data signal and the sub data signal, and synchronizes the phase of the carrier wave in the case of a preamble signal or when a unique word signal is not detected, assuming that there is no phase modulation by the sub data signal. By introducing the output of this data signal frame synchronization circuit to the main data signal reproducing means, the time taken to pull in the carrier wave by complex modulation can be brought as close to zero as possible, and furthermore, the main data signal and the sub data signal can be quickly combined. A complex modulated wave transmission method characterized by being synchronized with.