JP2011130475A - Digital transmission system corresponding to cross-polarization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attenuate a crosstalk portion of horizontal polarization and vertical polarization for a transmission system with a digital modulation section and a digital demodulation section. <P>SOLUTION: The MPEG TS with different information for the vertical polarization and horizontal polarization is entered, and Null insertion processing is provided for each system of the horizontal polarization and vertical polarization to equalize the TS rate, and a clock and a preamble period timing pulse are made common and are temporally synchronized. A reference signal is transmitted in the form wherein the horizontal polarization is only present for the first half of a preamble period, while the vertical polarization is only present for the latter half. The equalization processing of reception is performed in the first half for the horizontal polarization, while in the latter half for the vertical polarization. A crosstalk portion from the horizontal polarization to the vertical polarization is detected in the first half, while a crosstalk portion from the vertical polarization to the horizontal polarization is detected in the latter half. After calculation of a crosstalk portion from the decoding result and subtraction of a crosstalk portion from a peer's pre-decoding signal, demodulation and error correction are performed for decoding to output the TS. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission system that performs digital modulation and demodulation in which video and data are converted into digital signals and transmitted.

  Video and audio signals were transmitted wirelessly by analog FM methods several years ago, but in recent years, digital transmission methods such as QAM (Quadrature Amplitude Modulation) methods have been used. Yes.

  Broadcasting television broadcasts broadcast materials received at receiving bases (mostly equipped with a transmitting station) at the top of a mountain or in a high building to the headquarters using microwaves. A transmission device that connects video and audio from the transmitter to the studio is referred to as TSL. This TSL device is an important line for transmission to a general home, and includes a control unit that performs modulation, a high-frequency unit that converts to microwaves, a power source, and the like.

  In recent years, there has been a growing demand for transmitting different materials at the same frequency from the standpoint of effective use of radio resources. A typical example is a method of transmitting material 1 with horizontal polarization and material 2 with vertical polarization.

  FIG. 9 is a block diagram showing the overall configuration of a TSL device using horizontal (H) and vertical (V) polarized waves in a conventional video transmission system. The video is input to the transmission control unit (TC) as digital data in MPEG TS (Transport Stream) format. The TC performs single 64QAM modulation and outputs a 130 MHz IF signal. The IF signal is sent to the transmission high-frequency units (TH) 2a and 2b, converted into a microwave band signal, amplified in power, and output from the antenna 6 in horizontal polarization and vertical polarization, respectively. The single QAM signal that has become a microwave reaches the receiving antenna 7 in the studio located several kilometers to several tens of kilometers away. From the signal from the antenna 7, the H component and the V component are respectively extracted and input to the reception high frequency units (RH) 9a and 9b. The RHs 9a and 9b convert the received single QAM signal into an IF signal of 130 MHz and pass it to the reception control units (RC) 8a and 8b. The video data TS demodulated by the RCs 8a and 8b is output.

  FIG. 10 is a block diagram showing a TC configuration of a conventional digital TSL device using horizontal and vertical polarization. The TS input data is added with a parity signal by the outer encoder 12. A phase-locked voltage controlled oscillator (PLLVCO) 19 receives a system clock (sys-ck) and sends a clock (CK) having a predetermined frequency to each unit. The control unit (CONT) 15 receives CK and passes a control signal that becomes H during the preamble period to the preamble pattern generator 14 and the selection unit (SEL) 16. The TS input data to which the parity signal is added is time-compressed through the memory 13 during a period excluding the preamble period, the preamble is inserted by the SEL 16, and single 64 QAM modulation is performed by the MOD 17 and converted into a 130 MHz IF signal.

  The transmission high-frequency units 2a and 2b basically have the same configuration, but the time delay and the like are slightly different due to differences in detailed characteristics such as a filter in a microwave band. The role of the preamble is used on the receiving side to determine the sample timing of the subsequent data symbol and to correct waveform distortion caused by transmission.

  FIG. 11 is a block diagram showing the RC configuration of a conventional TSL device using horizontal and vertical polarization, and FIG. 12 is a detailed configuration of the RC demodulator (DEM) of the conventional TSL device using horizontal and vertical polarization. FIG. 13 is a transmission / reception time chart showing a signal form of a conventional TSL.

Japanese Patent Laid-Open No. 10-17579 JP 2004-201154 A

  In the conventional configuration described above, the horizontal polarization and the vertical polarization usually cause crosstalk of 15 dB to 25 dB or less. In addition, when the radio wave propagation state fluctuates, there may be a case where the amount of crosstalk increases. In this case, since it is a different material, the transmitted contents are different and affect each other as noise.

  The present invention eliminates these drawbacks and aims to realize a transmission system capable of attenuating the crosstalk of horizontal polarization and vertical polarization in a system that transmits different materials using horizontal polarization and vertical polarization. And

  In order to solve the above problems, the present invention provides a digital transmission method for transmitting information using horizontal polarization and vertical polarization. In the digital transmission method, each system of horizontal polarization and vertical polarization is synchronized in time. The reference signal transmits a transmission signal having a signal configuration in which one of the preamble periods is divided and only the horizontal polarization is divided into one and the other is divided into the vertical polarizations.

  In the digital transmission method described above, the reception equalization processing is performed while the horizontally polarized wave is divided into the preamble periods, while the vertically polarized wave is executed on the other side divided into the preamble periods. Detect crosstalk from wave to vertical polarization, detect crosstalk from vertical polarization to horizontal polarization on the other side of the preamble period, calculate crosstalk from decoding results, and decode partner Subtract the crosstalk from the previous signal.

  Specifically, it has digital modulation units and digital demodulation units of multiple systems of horizontal polarization and vertical polarization, and each system of horizontal polarization and vertical polarization transmits in synchronization with the reference signal. Transmits in the first half of the preamble period with only horizontal polarization and the second half with only vertical polarization.Reception equalization is performed in the first half for horizontal polarization and in the second half for vertical polarization. The crosstalk from the horizontal polarization to the vertical polarization is detected in the second half, the crosstalk from the vertical polarization to the horizontal polarization is detected in the second half, and the crosstalk is calculated from the decoding result. The crosstalk is subtracted from the signal, then demodulated, error corrected, and decoded. Alternatively, the reference signal is transmitted in such a way that the first half is only vertical polarization and the second half is only horizontal polarization, and reception equalization processing is executed in the first half for vertical polarization and in the second half for horizontal polarization. Detects the crosstalk from vertical polarization to horizontal polarization at, detects the crosstalk from horizontal polarization to vertical polarization in the second half, calculates the crosstalk from the decoding result, and decodes the other party After subtraction is subtracted from the previous signal, it is demodulated, error corrected, and decoded.

  Further, in the above transmission method, different information is sent for the horizontal polarization and the vertical polarization, and the transmission side uses a common clock and preamble period pulse for each of the horizontal polarization and the vertical polarization.

  In the above transmission method, digital data in MPEG TS (Transport Stream) format is transmitted, a null insertion process is provided on the transmission side, and the TS rate is the same for horizontal polarization and vertical polarization.

  As described above, according to the present invention, the clock and the preamble period timing pulse are made common, the TS rate is made the same by inserting Null, and the time is synchronized, so that it is stably stabilized from horizontal polarization in the first half of the preamble period. Crosstalk from vertical polarization can be detected, and crosstalk from vertical polarization to horizontal polarization can be detected in the second half of the preamble period. As a result, it is possible to stably transmit another material at the same frequency while suppressing signal deterioration together with error correction.

The block diagram which shows the whole structure of the video transmission system of this invention Transmission side time chart showing signal form of the present invention Reception side time chart showing signal form of the present invention Schematic diagram showing the receiving side processing of the present invention The block diagram which shows the transmission control part (TC) of one Example of this invention. The block diagram which shows the stuffing part of TC of one Example of this invention The block diagram which shows the reception control part (RC) of one Example of this invention The block diagram which shows the demodulation part (DEM) of RC of one Example of this invention Block diagram showing the overall configuration of a conventional video transmission system Block diagram showing a conventional transmission control unit (TC) Block diagram showing a conventional reception control unit (RC) Block diagram showing a conventional RC demodulator (DEM) Transmission / reception time chart showing conventional signal form

  The configuration and basic operation of an embodiment according to the present invention will be described with reference to FIGS. 1, 2, 3, 4, 5, 6, 6, 7 and 8. FIG.

  FIG. 1 is a block diagram showing the overall configuration of a video transmission system according to the present invention. The main difference between the block diagram showing the entire configuration of the conventional video transmission system in FIG. 9 and FIG. 1 is that, on the transmission side, the control unit 3C sends a common clock t-ck and a transmission preamble period t pulse to the transmission control unit. (TC) is supplied to perform synchronization processing by stuffing and alternate pause of the reference signal. On the receiving side, the crosstalk coefficient s is returned from the reception control unit (RC) to the control unit 4C. When the crosstalk coefficient s is larger than a certain amount, the control unit 4C controls ON / OFF for subtraction of the counterpart crosstalk component, and instructs the RC to perform subtraction processing by subtraction control FC.

  In FIG. 1 of the block diagram showing the overall configuration of the video transmission system of the present invention, 1a and 1b are transmission control units (TC), 2a and 2b are transmission high frequency units (TH), 3c and 4c are control units (CONT), Reference numerals 6 and 7 denote antennas, 9a and 9b denote reception high-frequency units (RH), and 10a and 10b denote reception control units (RC).

  FIG. 5 is a block diagram showing a transmission control unit (TC) of one embodiment of the present invention, and FIG. 6 is a block diagram showing details of the stuffing unit 11 of the TC of one embodiment of the present invention. Even when different information is transmitted for horizontal polarization and vertical polarization, in FIG. 5 and FIG. 6, the TS input is the memory 33 and is read according to the common clock t-ck. Over / short is output as a full / empty signal. If an empty has occurred in the null insertion unit 35, a null is inserted. If a full has occurred, the null is deleted, and the uniformed TS is made to match the read rate. To do. A parity signal is added to the uniformized TS by the outer encoder 12. The control unit (CONT) 15 receives the common clock t-ck, and passes a control signal that becomes H during the preamble period to the preamble pattern generator 14 and the selection unit (SEL) 16. The TS input data to which the parity signal is added is time-compressed through the memory 13 in a period excluding the preamble period, the preamble is inserted by the SEL 16, and a single 64QAM modulation is performed by the modulation unit (MOD) 17 to form a 130 MHz IF signal. Converted.

  2 is a transmission side time chart of the present invention, FIG. 3 is a reception side time chart of the present invention, and the difference from FIG. 13 of the transmission / reception time chart showing the conventional signal form is that the preamble of the IF signal The reference signal has a pause period alternately in the first half and the second half of the period. Using this pause period, the first half detects (V component) crosstalk from horizontal polarization to vertical polarization, and the second half detects (H component) crosstalk from vertical polarization to horizontal polarization. To detect.

  FIG. 4 is a schematic diagram showing processing on the receiving side of the present invention, FIG. 7 is a block diagram showing a reception control unit (RC) of one embodiment of the present invention, and FIG. 8 is an RC diagram of one embodiment of the present invention. It is a block diagram which shows the demodulation part (DEM) of. 4, 7, and 8, the horizontal polarization (H) data Dc <b> 1 generated by demodulating IFr <b> 1 is remodulated to generate a horizontal polarization modulation waveform (Hm). A polarization crosstalk waveform (Hs) is generated. Similarly, vertical polarization (V) data (Dc2) generated by demodulating IF2r is remodulated to generate a vertical polarization (V) modulation waveform (Vm), and vertical polarization is generated by crosstalk generation processing. (V) A crosstalk waveform (Vs) is generated. Then, Vs is subtracted from IFr1 and then equalized and demodulated to obtain H data Dc1, and further, the error is corrected outside to reproduce the horizontally polarized wave (H) TS, and Hs is subtracted from IFr2 and then equalized and demodulated. The V data Dc2 is further corrected for errors and the vertically polarized (V) TS is reproduced.

  In the block diagram of FIG. 8 showing the RC demodulator (DEM) of one embodiment of the present invention, 21a and 21b are remodulators, 22a and 22b are coefficient multipliers, 23a and 23b are gate on / off, 24a, Reference numeral 24b denotes a subtraction unit, 25a and 25b denote equalization units, 26a and 26b denote demodulation units, 27a and 27b denote preamble extraction units, 28a and 28b denote equalization calculation units, and 29a and 29b denote crosstalk detection units. In FIG. 8, the V data Dc2 becomes a V modulation waveform Vm by the remodulator 21a, Vm is multiplied by the crosstalk coefficient s1 by the coefficient multiplier 22a, controlled by the subtraction control FC1 by the gate on / off 23a, and V cross The talk waveform Vs. The preamble extraction unit 27a generates Pr-puls and a holding instruction pulse from IFr1 and the equalization calculation unit 28a and the crosstalk detection unit 29a generate a crosstalk coefficient s1. Similarly, a crosstalk coefficient s2 is generated from IFr2.

  In the above description, the reference signal has been described using a method in which only the first half of the preamble period is horizontal polarization and the second half is only vertical polarization. Similarly, if the first half of the reference signal is transmitted only in the vertical polarization and the second half is transmitted only in the horizontal polarization, the reception equalization processing is executed in the first half for the vertical polarization and in the second half for the horizontal polarization. The crosstalk from the vertical polarization to the horizontal polarization is detected in the second half, the crosstalk from the horizontal polarization to the vertical polarization is detected in the second half, and the crosstalk is calculated from the decoding result. It is possible to subtract the crosstalk from the signal, equalize, demodulate, correct and decode the error, and output a TS. Further generalized, even if the reference signal is transmitted by dividing the preamble period arbitrarily with only horizontal polarization, and the other divided division period with only vertical polarization, the reception equalization process is performed in the same way. Polarization is performed by arbitrarily dividing the preamble period, while vertical polarization is performed by the other divided preamble period, and the crosstalk from horizontal polarization to vertical polarization is detected by arbitrarily dividing the preamble period. Then, on the other side of the preamble period, the crosstalk from vertical polarization to horizontal polarization is detected, the crosstalk is calculated from the decoding result, the crosstalk is subtracted from the signal before decoding, etc. It is possible to demodulate, demodulate, decode, and output TS.

  In the above description, a case has been described in which different information is transmitted for horizontal polarization and vertical polarization. Further, even in the case of diversity in which the same information is transmitted for horizontal polarization and vertical polarization, similarly, crosstalk is detected, the crosstalk is calculated from the decoding result, and the crosstalk is calculated from the signal before decoding of the other party. Subtraction, equalization, demodulation, error correction, decoding, and output of TS can be performed, and it is possible to strengthen against degradation of the transmission path state.

1a, 1b, 5a, 5b: transmission control unit (TC),
2a, 2b: Transmission high-frequency part (TH),
3c, 4c, 15, 30a, 30b: control unit (CONT),
6, 7: Antenna, 9a, 9b: Reception high frequency part (RH),
8a, 8b, 10a, 10b: reception control unit (RC),
11: Stuffing section, 12: Outer encoding section, 13, 33: Memory,
14: Preamble pattern generator,
16: Selection unit (SEL), 17: Modulation unit (MOD),
18a, 18b: Demodulator (DEM)
19a, 19b: Phase-locked voltage control oscillator (PLLVCO),
20a, 20b: outer correction unit, 21a, 21b: remodulation unit,
22a, 22b: coefficient multiplication unit, 23a, 23b: gate on / off,
24a, 24b: subtraction unit, 25a, 25b: equalization unit,
26a, 26b: demodulator, 27a, 27b: preamble extractor,
28a, 28b: equalization calculation unit, 29a, 29b: crosstalk detection unit,
34: NULL generation unit, 35: NULL insertion unit,
t-puls: Transmitted preamble period pulse, t-ck: Common clock,
sys-ck: System clock, Pr-puls: Receive preamble period pulse,
H: horizontal polarization, V: vertical polarization, Fc1, Fc2: subtraction control,
Dc1: Horizontal polarization (H) data, Dc2: Vertical polarization (V) data,
Hm: horizontal polarization modulation waveform, Hs: horizontal polarization crosstalk waveform,
Vm: vertical polarization modulation waveform, Vs: vertical polarization crosstalk waveform.

Claims (4)

In a digital transmission system composed of a transmission device and a reception device and transmitting a signal having a preamble period and a data period using horizontal polarization and vertical polarization, respectively,
The transmitting apparatus inserts a reference signal only in a horizontally polarized signal in one period obtained by dividing the preamble period, and makes a reference only in a vertically polarized signal in the other period obtained by dividing the preamble period. Configured to insert signals,
The receiving device is:
Crosstalk from horizontal polarization to vertical polarization is detected in one period obtained by dividing the preamble period, and crosstalk from vertical polarization to horizontal polarization is detected in the other period obtained by dividing the preamble period. And a crosstalk detector for obtaining a crosstalk coefficient,
A remodulation unit that remodulates the horizontal polarization data and the vertical polarization data generated by the demodulation process to generate a horizontal polarization modulation waveform and a vertical polarization modulation waveform;
A coefficient multiplier for generating a crosstalk waveform by multiplying the horizontal polarization modulation waveform and the vertical polarization modulation waveform by the crosstalk coefficient obtained by the crosstalk detector;
A subtractor for subtracting the crosstalk waveform from the horizontally polarized signal and the vertically polarized signal before demodulation,
A digital transmission system comprising: a demodulator that demodulates the horizontally polarized signal and the vertically polarized signal that have undergone the subtraction process. In the digital transmission system according to claim 1,
The transmission apparatus further includes a stuffing unit that inserts or deletes a Null signal, and makes the transport stream rate the same for the horizontally polarized signal and the vertically polarized signal. . In the digital transmission system according to claim 1,
The reception apparatus further includes an equalization unit that performs equalization processing of a horizontally polarized signal and a vertically polarized signal, respectively, using the reference signal inserted in the preamble period. Digital transmission system. In the digital transmission system according to claim 1,
The digital transmission system according to claim 1, wherein the transmission apparatus shares a clock and a preamble period timing pulse in a horizontally polarized signal system and a vertically polarized signal system.

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