JP2005229467A - Radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a radio receiver which is suitable for a wireless camera system and is capable of changing the frequency band or frequency of a radio transmission signal by a radio transmitter and performing flexible operability. <P>SOLUTION: The radio receiver has band pass filters (band separating circuits) 122<SB>-1</SB>to 122<SB>-N</SB>for each separating a received radio transmission signal into a plurality sub-channel signals having different frequency bands, frequency converting circuits 123<SB>-1</SB>to 123<SB>-N</SB>for performing frequency conversion for each sub-channel signal, a plurality of demodulation processing circuits 125<SB>-1</SB>to 125<SB>-N</SB>for each applying quadrature demodulation to the sub-channel signal after frequency conversion, and a multiplexing circuit (compositing circuit) 127 for synthesizing information code sequences after the quadrature demodulation as necessary to restore one transport stream. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radio reception apparatus that receives a signal modulated by a multi-carrier modulation scheme that disperses information on a plurality of subcarriers (subcarriers) having different frequencies and performs orthogonal modulation.

There is known a wireless transmission system that wirelessly transmits a flow of information (stream) that integrates moving images and audio and can be reproduced synchronously. A typical wireless transmission method has already been realized as a program distribution method via a wireless camera or wireless LAN that captures the actual situation of sports, events, etc., and transmits it wirelessly to the receiver of the base station.
Wireless cameras are cordless and highly mobile, making them suitable as sub-cameras or news gathering devices that move around a large venue. In response to the recent digitization of broadcasting, a conventional system employing analog modulation as a transmission method from a wireless camera to a base station is shifting to a new system employing digital modulation. Such digitalization of wireless transmission systems in recent years makes it possible to employ error correction technology, and to diversify multimedia information sources that have robust tolerance against errors in transmission lines and stable transmission quality. It contributes greatly.

  As a standard television system, a so-called SDTV (Standard Definition Television) system having 525 scanning lines in Japan and North America and 625 scanning lines in Europe is still widely used. However, with the recent digitalization of broadcasting, there is a demand for high-quality and large-screen video information display, and there is a demand for high definition television (HDTV) support for programs. Therefore, a transmission / reception system using a wireless camera is also expected to support HDTV.

The inventor has proposed a data transmission system capable of transmitting high-density information such as HDTV specifications through a wireless transmission path in a narrow frequency band without reducing the bit rate (see Patent Document 1).
The transmission apparatus of the data transmission system described in Patent Document 1 divides an information code sequence (TS: transport stream) compliant with, for example, MPEG (Moving Picture Experts Group) 2-TS standard in units of TS packets, and A divided transport stream is formed. Then, each divided transport stream is time-expanded, modulated by OFDM (Orthogonal Frequency Division Multiplexing), and then sent simultaneously to different wireless transmission paths via different transmission units (high-frequency amplifier and transmission antenna). To do. Correspondingly, a large number of receiving units (high-frequency amplifiers and frequency conversion circuits) are prepared on the receiving device side, and information sent via different wireless transmission paths (divided transport streams) Are received individually. Then, the received signal data is OFDM demodulated in each reception channel, and the original high bit rate transport stream is reproduced by performing time compression and multiplexing while maintaining packet synchronization.

By the way, it is important to make the most effective use of a limited frequency bandwidth among the frequency bandwidths that are permitted to be used in the field such as the current live broadcast or news coverage.
Here is a specific example of operation. For example, in the live broadcast of sports or events or large-scale news sites, if the number of required wireless cameras is determined, all of them can be used for HDTV, and the usable frequency band Therefore, the frequency bandwidth allocated to each wireless camera is narrowed, so that the amount of signal information transmitted from each wireless camera is reduced and the image quality is lowered. Conversely, if the image quality is to be maintained, the number of wireless cameras that can be used within a limited frequency band decreases, and video and audio necessary for program production cannot be collected.
Therefore, about one or two HDTV cameras are allocated to the main camera where a relatively long broadcast time is taken from several wireless cameras, and the broadcast time is expected to be sporadic and short or broadcast on a small screen. Since images taken at special angles and places often have low priority as broadcast images, it is conceivable to allocate SDTV cameras for shooting with low priority. For example, in sports broadcasting, the priority of sports live video is high, but the priority of video showing the state of an announcer, commentator, or audience is low. However, in live broadcasts and interviews, for example, when a spare SDTV camera is substituted due to a failure of an HDTV camera, or where the SDTV camera has been placed as the main video generation location up to now due to sudden situations May occur. Further, there is a case where it is desired to switch between the HDTV camera and the SDTV camera in accordance with a program organization request.

  In such a case, the conventional HDTV camera and SDTV camera each have a fixed frequency band, and can flexibly respond to changes in the transmission rate according to the change in the situation during operation. There wasn't. For this reason, it is difficult to broadcast SDTV standard rough video for a long time even though it is HDTV broadcasting, or conversely, HDTV standard high-definition video is used for small screen display. There was a high possibility of nonconformity.

When the transmission technique disclosed in Patent Document 1 described above is applied to a wireless camera, a wideband signal output from an HDTV camera or the like can be divided into narrowband channels similar to those of an SDTV camera and transmitted. Therefore, there is an advantage that a high-quality image with a high bit rate can be transmitted even in a relatively narrow frequency band. However, since the number of wireless transmission paths (transmission channels) increases, it remains the same that a wide frequency bandwidth is required as a whole.
In addition, although the transmission device described in Patent Document 1 is assumed to transmit a signal with a high transmission rate such as an HDTV signal, the reception device outputs a signal with a relatively low transmission rate such as an SDTV signal. I don't assume that. Therefore, even though the transmission device disclosed in Patent Document 1 can be used as a wireless transmission device dedicated to HDTV, for example, it cannot be used as a reception device of the wireless transmission / reception system capable of flexible operation.

As described above, the conventional wireless receiver is a dedicated wireless camera for each image standard such as an HDTV camera and an SDTV camera. In particular, the HDTV camera is compatible with a conventional SDTV compatible system from the viewpoint of effective use of a frequency band. Therefore, there is a problem in that it cannot be adapted to an actual operation site where a plurality of types of transmission devices having different frequency bands of transmission signals are used.
JP 2002-344965 A

  The problem to be solved is to assign wireless transmission channels of signals with different transmission rates within a predetermined frequency bandwidth according to the transmission rate (transmission bit rate per unit time) of the signal to be transmitted without waste. There is no receiving apparatus suitable for realizing a wireless transmission / reception system capable of performing the above.

  A radio receiving apparatus according to the present invention is a radio receiving apparatus that receives a radio transmission signal, demodulates the radio transmission signal, and extracts an information code sequence. The received radio transmission signal includes a plurality of subchannels having different frequency bands. Band-separation circuit that divides the signal, multiple frequency conversion circuits that perform frequency conversion for each sub-channel signal to align it with the baseband or a fixed frequency band, and orthogonally demodulate the frequency-converted sub-channel signal, respectively And a synthesizing circuit that generates one information code sequence by synthesizing the plurality of information code sequences when there are a plurality of information code sequences after orthogonal demodulation.

In the radio reception apparatus of the present invention, preferably, each of the carrier wave of the radio transmission signal and the carrier wave of the subchannel signal after the division is a plurality of unit subcarriers having a constant frequency interval f0 adapted to the OFDM modulation scheme. It is composed of a unit subcarrier group that is a set,
When the band separation circuit performs the division, the radio transmission signal is divided in different frequency bands having a constant width of f0 × K (K: a fixed number).

In this case, it preferably has a local oscillation circuit that generates a plurality of local oscillation signals of different frequencies in units of f0 × K and outputs the signals to the plurality of frequency conversion circuits, and the local oscillation circuit is input It is configured to be able to perform output control for stopping the output of the local oscillation signal output to the frequency conversion circuit specified in accordance with the control signal.
More preferably, it has a plurality of reception processing units including the band separation circuit, the plurality of frequency conversion circuits, the plurality of demodulation processing circuits, and the synthesis circuit, all the frequency conversion circuits of the plurality of reception processing units, In accordance with the input control signal, control is performed so as not to frequency-convert subchannel signals in the same frequency band.

When receiving the wireless transmission signal, the wireless reception device having such a configuration inputs the wireless transmission signal to the band separation circuit. The band separation circuit divides the wireless transmission signal into a plurality of subchannel signals having different frequency bands. The divided sub-channel signals are respectively input to the frequency conversion circuit. Each frequency conversion circuit performs frequency conversion for each subchannel signal, and arranges a plurality of subchannel signals into a baseband or a fixed frequency band. The subchannel signals after frequency conversion are each orthogonally demodulated by a demodulation processing circuit and converted into an information code sequence. When there are a plurality of outputs (information code sequences after orthogonal demodulation) from a plurality of demodulation processing circuits, one information code sequence is generated by combining the plurality of information code sequences by the combining circuit.
When a plurality of radio transmission signals are one OFDM transmission signal, the received radio transmission signals are band-separated in different frequency bands having constant widths K (K: a fixed number) times f0 of the unit subcarrier interval. . In the frequency conversion, a plurality of local oscillation signals having different frequencies of f0 × K are output from the local oscillation circuit. At this time, the stop of the plurality of local oscillation signals is controlled by the input control signal. For this reason, in each reception processing circuit, only the frequency band specified by the control signal is subjected to frequency conversion, a plurality of subchannel signals become baseband signals or low frequency signals, and these are combined to restore the information code sequence. . At this time, since the frequency conversion band is defined by the control signal, an information code sequence (transport stream) defined by the control signal is output from each reception processing unit. When the control signal is switched, the combination of local oscillation signals that are controlled to stop by the local oscillation circuit changes accordingly, and as a result, wireless transmission used when generating a transport stream output from the output channel of the reception processing circuit The signal frequency band and transmission frequency are switched.

  The radio reception apparatus of the present invention can arbitrarily change the frequency band and the center frequency to be divided from the received radio transmission signal according to control information from the outside. As long as the wireless bands do not overlap, even if a plurality of wireless transmission signals are received simultaneously, the frequency bands and the center frequencies of the transmitted wireless transmission signals are based on the control signal from the outside. This is because it can be determined. Accordingly, different types of signals such as HDTV signals and SDTV signals input at the same time can be separated and demodulated and output from different output channels. Further, since the control signal is changed when the radio transmission signal organization is changed, each reception processing unit can be operated in conformity with the change of the radio transmission signal organization.

  Hereinafter, an embodiment of the present invention will be described with reference to a wireless camera (transmission device) that processes a series of information code sequences (streams) obtained by integrating images and audio into N (for example, 4) radio subchannels. A wireless transmission / reception apparatus having a base station (reception apparatus) will be described as an example with reference to the drawings. This wireless transmission / reception apparatus adopts the transport stream (TS) standard defined as a multiplexing method of MPEG2 Systems as a radio transmission signal from a wireless camera to a base station, and further employs OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method. ) The modulation method is adopted. By using a digital transport stream as described above, it is possible to transmit high-quality images and sound with a small reduction in S / N ratio compared to the case where video material is transmitted in an analog manner. Become. In addition, the OFDM modulation scheme is unlikely to deteriorate in image quality due to fluctuations in electric field strength accompanying mobile reception, and is less affected by multipath interference. Therefore, by adopting the OFDM modulation method, it is possible to transmit high-quality images and sounds.

FIG. 1 shows a configuration of a wireless camera 1 as a receiving device.
The wireless camera 1 broadly categorizes and generates an information acquisition unit 2 including an image pickup device (Camera) 2A and a microphone (Mic.) 2B, and a continuous information code sequence (transport stream) that integrates image data and audio data. A transmission processing unit 3 that performs processing such as modulation, a transmission / reception unit 4 having a function of “transmission unit” or “reception unit”, a reception processing unit 5 that receives a control signal input from the transmission / reception unit 4, various clocks, and A circuit unit (TIMING & CLK) 6 that generates a timing control signal and a control unit (Controller) 7 that controls these units are included.

The transmission processing unit 3 includes a video processing circuit (Video) 31, a video encoding circuit (Video Coder) 32, an audio processing circuit (Audio) 33, an audio encoding circuit (Audio Coder) 34, a multiplexing circuit (MUX) 35, Demultiplexer circuit (DMUX) 36 as “divider circuit”, time expander circuits 37 _{−1 to} 37 _−N having the same number as the maximum division number N of the division circuit 36, and the same number as the maximum division number N It has a modulation processing circuit (Mod.) 38 _{−1 to} 38 _−N , a band integration circuit 39, a transmission local oscillation circuit 40, and a transmission high-frequency circuit (TXRF) 41 as a “high-frequency circuit” of the present invention.

The video processing circuit 31 is a circuit that performs various characteristic corrections and conversions (including AD conversion) on the image pickup signal sent from the image pickup device 2A. The video encoding circuit 32 is a circuit that performs high-efficiency compression encoding (so-called information source encoding) processing specified by the MPEG2-TS standard on the digital video signal from the video processing circuit 31.
Similarly, the audio processing circuit 33 is a circuit that performs predetermined audio processing on the audio signal collected by the microphone 2B, and the audio encoding circuit 34 applies the high-efficiency compression encoding processing to the digital signal after the audio processing. It is the circuit which applies.
The multiplexing circuit 35 is referred to as a so-called transport stream by time-division multiplexing the encoded video encoded signal and audio encoded signal by a method defined in the MPEG2-TS standard. This is a circuit for converting into an integrated information code sequence TS0 capable of synchronous reproduction processing.

The dividing circuit 36 is a demultiplexing circuit that receives the transport stream TS0, sequentially divides the transport stream TS0 in units of TS packets (that is, in time division), and distributes it to N output channels. Each of the time expansion circuits 37 _{-1 to} 37 _-N provided in each of the output channels of the dividing circuit 36 inputs one of the divided transport streams TS _{-1 to} TS _-N , and has a maximum N equal to the number of divisions. This is a circuit for performing double time expansion processing.
In the following description, it is assumed that the transport stream TS0 is divided into the maximum number N unless otherwise specified.

FIG. 2 is a time chart showing an information code sequence in units of TS packets in order to explain division and time expansion when the number N of output channels of the division circuit 36 is four.
From the multiplexing circuit 35, the video encoded signal and the audio encoded signal are multiplexed, and a transport stream TS0 composed of TS packets P0, P1, P2,. FIG. 2A shows the transport stream TS0 output from the multiplexing circuit 35.
When the transport stream TS0 is input to the dividing circuit 36, the dividing circuit 36 divides the transport stream TS0 in units of TS packets, and sequentially distributes and outputs the divided TS packets to four channels. Although details will be described later, the number of packet divisions and channel distributions can be arbitrarily changed as long as the maximum number is N or less.
The time expansion circuits 37 _-1 ,..., 37 _-N perform time expansion processing on the TS packets divided and transmitted to each channel. At this time, it is desirable that the time expansion magnification is equal to the division number N. In this example, since the division number N is 4, the TS packet output from the multiplexing circuit 35 is expanded by four times. As a result, TS packets that are discrete after division are connected to each other to form a transport stream that is a continuous information code sequence. 2 (B) to 2 (E) show transport streams TS _{-1 to} TS _-4 of each channel formed by time expansion after division. Such processing can be easily realized by mounting a memory for one packet in the time expansion circuits 37 _-1 ,..., 37 _-N . This memory is a memory in which writing and reading can be performed asynchronously, and time expansion can be performed by slowly performing the reading speed four times the writing speed.

Time decompression processing transport stream TS _-1 ~TS _-N subjected in parallel are input to the corresponding modulation processing circuit 38 _-1 to 38 DEG _-N, where necessary channel coding including OFDM modulation Various processes are performed. The individual circuit configurations of the modulation processing circuits 38 _{-1 to} 38 _-N are common.

FIG. 3 shows the configuration of the modulation processing circuit 38 _-I (I = 1 to N).
The modulation processing circuit 38 _-I includes an error correction coding circuit (FEC Encoder) 381 that performs error correction processing (FEC), a signal point arrangement circuit (Mapping) 382, and an inverse fast Fourier transform (IFFT). Transform circuit 383, guard interval addition circuit (GI) 384, and quadrature modulation circuit (Quad. Modulator) 385 as an “orthogonal modulation unit”. The configuration of the quadrature modulation circuit 385 is shown in FIG.

An operation clock CLK0 is supplied to the circuits 381 to 385 from a circuit unit (TIMING & CLK) 6 that generates various clocks shown in FIG. Here, the signal point arrangement circuit 382, the IFFT circuit 383, and the guard interval addition circuit 384 are particularly referred to as “symbol generation unit” in the present invention. Of the symbol generators, especially the IFFT circuit 383 and the guard interval adding circuit 384 are supplied with a necessary synchronization signal SYNC from a circuit unit (TIMING & CLK) 6 that generates various clocks and the like. Therefore, the N IFFT circuits 383 in the N modulation processing circuits 38 _{-1 to} 38 _-N can execute the fast inverse Fourier transform synchronously, and the N guard interval addition circuits 384 have the same length. A guard interval is added at the same timing. As a result, it is possible to generate OFDM symbols with the same timing in the _N modulation processing circuits 38 _{-1 to} 38 _-N .

The operation of the modulation processing circuit 38- _I will be described. The configuration and operation of the reception system circuit (reception processing unit 5) will be described later.

  First, error correction coding circuit 381 performs error correction processing and interleaving processing as transmission path coding processing. Here, as channel coding, error correction coding is usually performed by using a concatenated code of a Reed-Solomon (RS) code and a convolutional code. In convolutional coding, convolutional coding is performed at a coding rate ½ that is resistant to burst errors, and coding rates 3/4 and 2/3 are generated in accordance with standard option specifications. Various interleaving processes are performed on the convolutionally encoded signal in the symbols as necessary. The information code sequence after transmission path coding is sent to a signal point mapping circuit (Mapping) 382.

  The signal point arrangement circuit (Mapping) 382 divides each TS packet data of the input information code sequence into predetermined bit units, and the divided unit data is orthogonal coordinates according to a predetermined carrier modulation method (for example, 16QAM modulation). A process of assigning to the upper arrangement point (a modulation symbol having phase and amplitude information) is executed. Thereby, a modulation symbol depending on the carrier modulation scheme of the OFDM carrier is generated.

  The modulation symbol generated at this time is a signal in the frequency domain. Next, a fast inverse Fourier transform is performed by the IFFT circuit 383 to convert it into a signal in the time domain. The output from the IFFT circuit 383 is a complex time signal. The real part data Re is output from the real part output of the IFFT circuit 383, and the imaginary part data Im is output from the imaginary part output.

  A guard interval adding circuit (GI) 384 adds a guard interval in units of the predetermined bits to an information code sequence composed of real part data Re and imaginary part data Im. The guard interval is obtained by copying a back porch of a predetermined unit of the information code sequence and inserting it on the front side, and executes this processing by delay addition using a memory. By adding the guard interval, an OFDM symbol that is a unit information code sequence of OFDM modulation is formed.

  The orthogonal modulation circuit 385 is a circuit that performs so-called OFDM modulation. The quadrature modulation circuit 385 quadrature modulates the real part data Re and the imaginary number data Im generated by the IFFT circuit 383 and added with the guard interval by the guard interval addition circuit 384.

  As a configuration for this, the quadrature modulation circuit 385 includes two multiplication circuits 3851 and 3852, an addition circuit 3853, and a local oscillation circuit 3854 as shown in FIG. The real time signal output (real part data) Re and the imaginary time signal output (imaginary part data) Im generated by the IFFT circuit 383 are supplied to the multiplier circuits 3852 and 3851 through the guard interval addition circuit 384, respectively. The local oscillation circuit 3854 oscillates at a fixed frequency and supplies two oscillation outputs of 0 ° and 90 ° phases to the two multiplication circuits 3852 and 3851, respectively. The outputs from these two multiplier circuits 3852 and 3851 are combined by an adder circuit 3853 and output as a quadrature modulation signal.

The band integration circuit 39 shown in FIG. 1 integrates the frequency bands of orthogonal modulation signals (each of K unit subcarrier groups) sent from _N modulation processing circuits 38 _{-1 to} 38 _-N , This is a circuit for generating an OFDM modulated signal S39 in one frequency band equivalent to the original information code sequence, that is, a signal obtained by modulating K × N OFDM carriers with the transport stream TS0 from the multiplexing circuit 35. As a configuration for integrating the frequency bands, the band integration circuit 39 includes N transmissions including a mixer in which one input is connected to any one of the corresponding outputs of the modulation processing circuits 38 _{-1 to} 38 _-N. Frequency conversion circuits 391 _{-1 to} 391 _-N and a synthesis circuit 392 including an adder that synthesizes outputs of these transmission frequency conversion circuits 391 _{-1 to} 391 _-N are provided. The transmission local oscillation circuit 40 is configured to be able to supply N transmission oscillation signals having different frequencies at predetermined intervals to inputs on the other side of the _N transmission frequency conversion circuits 391 _{-1 to} 391 _-N . Hereinafter, the frequency of the transmission oscillation signal supplied to the first transmission frequency conversion circuit 391 _-1 is f11, and the frequency of the transmission oscillation signal supplied to the second transmission frequency conversion circuit 391 _-2 (not shown) is f12, ..., the frequency of the transmission oscillation signal supplied to the Nth transmission frequency conversion circuit 391- _N is expressed as f1N.

  The OFDM modulated signal S39 after the integration of the frequency bands is amplified by a transmission high-frequency circuit (TXRF) 41 in the next stage, where unnecessary noise such as harmonics is removed by a built-in low-pass filter as necessary. Thereafter, it is converted into a predetermined high-frequency signal. This high-frequency signal is transmitted as a transmission signal # 0 having one frequency band from an antenna (ant.) 4A through a diplexer (Dip.) 4B of the transmission / reception unit 4.

FIG. 5 is a schematic diagram showing integration of frequency bands, and FIG. 6 is a diagram showing transmission signal # 0 after integration of frequency bands.
5A to 5D, the output signals # 1, # 2, # 3, and # 4 of the modulation processing circuits 38 _-1 , 38 _-2 , 38 _-3 , and 38 _-4 are plotted on the horizontal axis. Is schematically shown as a frequency. Each of the output signals # 1, # 2, # 3, and # 4 has an intermediate frequency band that is modulated into a signal composed of a predetermined number K of unit subcarriers whose frequency interval is constant at f0 and adjacent waves maintain an orthogonal relationship with each other. It is an OFDM signal. As a condition for generating such an OFDM signal, the modulation processing circuits 38 _-1 , 38 _-2 , 38 _-3 , and 38 _-4 have the same transmission path coding parameters, that is, N error correction coding circuits 381. Need to have the same coding rate, and the N interleave circuits must have the same interleave parameters. In addition, N IFFT circuits 383 operate in synchronization, and N guard interval addition circuits 384 operate so as to add a fixed-length guard interval at the same timing within the symbol, and further, a plurality of modulation processes It is necessary that the time lengths and output timings of the symbols generated by the symbol generators of the circuits 38 _{-1 to} 38 _-N are the same.

FIG. 5 (E) shows a transmission signal # formed by integrating the frequency bands of these intermediate frequency band OFDM signals # 1 to # 4, and further shifted to a transmission frequency band by high frequency conversion. 0 is shown schematically.
Integration of the frequency band, the transmission frequency converting circuit 391 _-1 ~391 _-N described above is, modulation processing circuit 38 _-1, ..., the oscillation of the OFDM modulated signal in the intermediate frequency band from 38 _-4 to local oscillator 40 This is executed by mixing with the signal to convert to a predetermined frequency band and combining (adding) the converted signals. Here, the oscillation frequencies f11 to f14 (see FIG. 1) for determining a predetermined frequency band are different frequencies for the respective transmission frequency conversion circuits 391 _{-1 to} 391 _-4 . As shown in FIG. 5, when the highest frequency a frequency f14 of the oscillation signal supplied to the fourth transmission frequency converting circuit 391 _-4 of the oscillation signal supplied to the third transmission frequency converting circuit 391 _-3 The frequency f13 is f13 = f14−K · f0, the frequency f12 of the oscillation signal supplied to the second transmission frequency conversion circuit 391 _-2 is f12 = f14−2K · f0, and the first transmission frequency conversion circuit 391 _−. The frequency f11 of the oscillation signal supplied to ₄ is preferably set to f11 = f14−3K · f0. In this case, the signals # 1 to # ₄ from the respective transmission frequency conversion circuits 391 _{-1 to} 391 _-4 are arranged so as to be adjacent to each other, and the frequency bands are integrated. Is formed. Hereinafter, this high frequency converted OFDM modulated signal (N unit subcarrier groups) # 0 is a "radio channel signal", its transmission frequency band is "radio channel", and each unit subcarrier group constituting the radio channel signal is The OFDM modulated signals # 1 to # 4 are referred to herein as “radio subchannel signals”, and the transmission frequency band thereof is referred to as “radio subchannel”.

FIG. 6B schematically shows an integrated radio channel signal # 0 made up of N radio subchannel signals # 1, # 2, # 3,..., #N, with the horizontal axis being the frequency f. A part thereof is shown in an enlarged manner in FIG. Here, the above conditions indicated by the oscillation frequencies f11 to f14 are applied to N oscillation frequencies. FIG. 6A shows a radio channel signal # 0 having a guard band between radio channels.
When there are a plurality of radio channels, if the orthogonality between the radio channel signals is not ensured, the carrier interference interference between the radio channel signals generally increases. The radio channel signal # 0 shown in FIG. 6A has a guard band having a constant frequency width fgd between the radio subchannel signals # 1 and # 2 and between # 2 and # 3 to prevent carrier interference. , ... are provided. However, in the present invention, since the frequency width fgd is defined as a multiple of the unit subcarrier f0, the interference wave does not affect each radio channel signal.

On the other hand, in the radio channel signal # 0 shown in FIG. 6 (C), the unit subcarrier SCk having the highest frequency among the OFDM unit subcarriers constituting the radio subchannel signal # 1 having the lowest frequency band and adjacent thereto. The interval between the OFDM unit subcarriers constituting the radio subchannel signal # 2 and the unit subcarrier SCk + 1 having the lowest frequency is the interval between the OFDM unit subcarriers constituting the radio subchannel signals # 1 to # 4. It is set equal to f0. This setting is the same between the other radio subchannel signals # 2 and # 3, between # 3 and # 4, and so on.
Thus, by making the radio subchannel interval equal to the unit subcarrier interval f0, it is possible to arrange the radio subchannels seamlessly and to effectively use the band. Further, orthogonality is ensured between the radio subchannel signals. Therefore, orthogonality is ensured in the entire signal of the integrated radio channel signal # 0, and it becomes possible to eliminate carrier interference between radio subchannel signals. As described above, the high-frequency radio channel signal # 0 in which the frequency bands are integrated ensures the orthogonality between the subcarriers, and can be handled as one OFDM modulated signal thereafter.
Note that the radio channel signal # 0 shown in FIG. 6A is also a kind of OFDM modulated signal because orthogonality is provided between unit subcarriers.
In order to properly arrange the radio subchannel signals # 1 to # 4 by forming the radio channel signal # 0 integrated into one, the adjacent frequency intervals of the local oscillation frequencies f11 to f1N supplied from the local oscillation circuit 40 are set. It is necessary to make K · f0 exactly. Such frequency control can be realized by configuring the local oscillation circuit 40 with a frequency synthesizer that operates using a signal synchronized with the clock from the circuit 6 that performs clock generation or the like as a reference.

  In the example described here, the wireless camera side uses a diplexer to transmit control signals between the wireless camera and the base station using the same antenna. However, even if the antenna (transmission path) is separated. I do not care.

  Next, the configuration and operation of the receiving apparatus will be described.

FIG. 7 shows the configuration of the wireless receiver.
The radio reception apparatus 10 includes a reception antenna (reception antenna: Ant.) 11A, a plurality of N reception processing units 12 ₋₁ , 12 ₋₂ ,..., 12 _−N , and N decoding circuits (dec.) 13 ₋₁ . , 13 _-2 ,..., 13 _-N , and a control circuit (Controller) 14 that controls each of these circuits and the entire receiving apparatus. Here, the number of divisions on the transmission side is the maximum number N, and the radio reception apparatus 10 is configured so as to cope with it. However, the number M (≦ N) of the parallel processing circuit portions actually used is arbitrarily changed in conjunction with the operation on the transmission side. Hereinafter, the case of using the maximum number N of parallel processing circuit portions will be exemplified.

Each of the reception processing units 12 ₋₁ , 12 ₋₂ ,..., 12 _−N includes a reception high frequency circuit (RXRF) 121 and N band pass filter circuits (BPF) 122 ₋₁ ,. (. Demod) 122 _-N, N pieces of the frequency conversion circuit 123 _-1, ..., 123 _-N, local oscillator circuit 124, N pieces of OFDM demodulation circuit as "demodulation processor" 125 _-1, ..., 125 _{- N 1} , N time compressors 126 ₋₁ ,..., 126 _−N , and a multiplexing circuit (MUX) 127 as a “combining circuit” for synthesizing signals (information code sequences) after time compression. .

FIG. 8 shows the configuration of the demodulation processing circuit 125 _-I (I = 1 to N).
The demodulation processing circuit 125 _-I includes a quadrature demodulation circuit (Quad. Demodulator) 1251, a fast Fourier transform (FFT) circuit 1252, an equalization circuit (Equalizer) 1253, and an error correction process (FEC: Forward Error Correction). And an error correction decoding circuit (FEC Decoder) 1254 for decoding the received information code sequence.

Next, the basic operation of the receiving apparatus will be described.
The radio channel signal received by the reception antenna 11A is input to the reception high-frequency circuit 121 and is subjected to predetermined signal amplification and channel selection processing and converted to a predetermined intermediate frequency.
The output of the reception high-frequency circuit 121 is branched into N systems and input to the band separation circuits 122 _{−1 ,.} Each of the band separation circuits 122 ₋₁ ,..., 122 _-N performs a predetermined band pass filtering process on the input wireless transmission signal. The pass band of the signals of each of the band separation circuits 122 _-1 ,..., 122 _-N is set to K · f 0. Here, the constant K is the number of unit subcarriers constituting one radio subchannel defined on the transmission side, and the frequency f0 is the frequency interval of the unit subcarriers. Further, the passbands of the signals of the respective band separation circuits 122 _-1 ,..., 122 _-N are set to be sequentially different at intervals in units of the width K · f0 of the passbands. Here, for example, the pass band of the band-separating circuit 122 _-1 is lowest on the frequency axis, then the passband of the band-separating circuit 122 _-2 low, the pass band of the band separation circuit 122 _-N is on the frequency axis highest. The band separation circuits 122 _-1 ,..., 122 _-N output a plurality of signals (hereinafter referred to as subchannel signals) having a constant bandwidth K · f 0 at predetermined frequencies different from each other.

Each subchannel signal that has been subjected to passband filtering to have a predetermined bandwidth is input to one of the frequency conversion circuits 123 _-1 ,..., 123 _-N connected to the respective output channels of the band separation circuit. To be supplied. Frequency conversion circuit 123 _-1, ..., to the other side input of 123 _-N, respectively f11, f12, ..., a local oscillation signal having a frequency of f1N is supplied from the local oscillation circuit 124. The frequencies f11, f12,..., F1N of the N local oscillation signals are set to be the same as the frequency of the local oscillation signal used when integrating the frequency bands on the transmission side (see FIGS. 1 and 5). . Each subchannel signal is frequency-mixed with these local oscillation signals and converted to a predetermined frequency.

Note that the local oscillation circuit 124 can be configured to perform control to stop unnecessary local oscillation signals f11 to f1N under the control of the control circuit unit 14. Thereby, it is possible to prevent unnecessary signals and noise from being subjected to frequency conversion.
In particular, in the present invention, since a plurality of N radio transmission signals of different frequency bands can be received simultaneously, in order to prevent interference in that case, all frequency conversions of the reception processing units 12 _{-1 to} 12 _-N are performed. The circuits 123 _{-1 to} 123 _-N are controlled so as not to frequency-convert subchannel signals in the same frequency band redundantly according to a control signal input from the control circuit unit 14. This control is executed when the control circuit unit 14 instructs each reception processing unit to stop a specific local oscillation signal to the local oscillation circuit 124. A high-frequency signal is output from the frequency conversion circuit in which the frequency conversion has been stopped, but this unnecessary signal is removed by a low-pass filter in the subsequent stage (not shown).

  The above bandpass filtering process and frequency band conversion will be described in more detail with reference to FIG. FIG. 9 is a schematic diagram showing passband separation and conversion operations with the horizontal axis as frequency f.

FIG. 9A shows a radio channel signal # 0 converted to an intermediate frequency by the reception high-frequency circuit 121. The intermediate frequency radio channel signal # 0 is output from the transmission apparatus 1 described above, and integrates the frequency bands of a plurality of N radio subchannel signals # 1, # 2,. Has been generated. As described above, K unit subcarrier intervals in each radio subchannel signal # 1, # 2,..., #N and two adjacent radio subchannel signals # 1 and # 2, # 2 and # 3, The frequency interval of... Is f0, and the radio channel signal # 0 is an OFDM modulated signal composed of K × N unit subcarriers as a whole.
The configuration shown in FIG. 9A is the case where the maximum frequency band is provided, and the radio receiving apparatus 10 is a radio composed of an arbitrary number M (≦ N) of radio subchannels of N or less and 1 or more. Channel signals can be received simultaneously. However, in the case of simultaneous reception, it is a condition that none of the N radio subchannel signals # 1, # 2,..., #N are used in common by a plurality of reception signals received simultaneously. Details of such simultaneous reception and channel usage change will be described later.

9 (B) to 9 (D) show subchannel signals # 1, # 2,..., #N after frequency conversion.
In order to align the frequencies of such subchannel signals # 1, # 2,..., #N, it is necessary to first perform frequency band separation by band separation circuits (bandpass filter circuits) 122 _{−1 ,.} There is. At this time, the aliasing distortion caused by the sampling clock in the image of N subchannels and the subsequent digital processing is suppressed simultaneously with the frequency band separation. However, the subchannel signals # 1, # 2,..., #N are adjacent at the OFDM unit subcarrier interval f0, and it is difficult to sharply block the OFDM subcarriers of the adjacent subchannels by the passband filter circuit. It is. Therefore, some adjacent channel carrier wave components remain in the subchannel signals # 1, # 2,.

Next, the frequency conversion circuits 123 ₋₁ ,..., 123 _-N perform processing for aligning the frequencies of the separated _subchannel signals # 1, # 2,. At this time, N local oscillation signals (frequency: f11, f12,..., F1N) having a frequency difference of K · f0 that is a product of the number K of unit subcarriers of the OFDM subchannel signal and the unit subcarrier interval f0 are used. . For example, if the local oscillation frequency at the time of frequency conversion of the sub-channel signal # 1 on the lowest side is f11, the local oscillation frequency of f12 = f11 + K · f0 is set to the second sub-channel signal # 2 having the next lowest frequency. Using a local oscillation frequency of f13 = f11 + 2K · f0 for the third subchannel signal # 3,..., F1N = f11 + (N−1) K · for the highest subchannel signal #N A local oscillation frequency of f0 is used.

9B to 9D, each unit subcarrier is indicated by a solid arrow, and a unit subcarrier of an adjacent subchannel that remains without being removed by the bandpass filter during separation is indicated by a dashed arrow. When subchannel signals # 1, # 2,..., #N are each converted to a predetermined frequency, the remaining unit subcarriers are also converted at a predetermined frequency, and remain as shown in the figure, for example. Specifically, in the lowest channel side sub-channel signal # 1, there are several residual waves with a period of f0 from the high-frequency side end, and on the contrary, the highest channel side sub-channel signal # 1. In N, there are several residual waves in the f0 period from the lower end. In addition, in the subchannel signals # 2 to # N-1 in the meantime, several residual waves exist at both f0 periods on both the high frequency side and the low frequency side.
However, as described in the frequency band integration of the transmitting apparatus, the integrated subchannel signals # 1 to #N are adjacent to each other across the boundary of the adjacent subchannel signals and belong to two different subchannels. The unit subcarriers are orthogonal in phase. Therefore, even if one of the two unit subcarriers is a residual wave, this does not affect the other unit subcarrier. For this reason, the radio receiving apparatus 10 can use band-pass filters for the band separation circuits 122 ₋₁ ,..., 122 _-N , so that there is an advantage that frequency band separation can be easily performed with a simple configuration. .

In this way, the frequencies of the sub-unit carrier waves of the N sub-channel signals are made uniform, or the sub-channel signals are converted into baseband signals. Each of the sub-channel signals whose frequency bands are aligned at a certain low level is output to any of the corresponding demodulation processing circuits 125 _-1 ,..., 125 _-N .

Each demodulation processing circuit 125 ₋₁ ,..., 125 _-N performs predetermined demodulation processing on the input _subchannel signal.
As shown in FIG. 8, first, the quadrature demodulation circuit 1251 performs quadrature demodulation of the subchannel signal and converts it into a baseband signal having a real part and an imaginary part. Although not specifically shown, the quadrature demodulation circuit 1251 is operated by a clock from a circuit unit (not shown) that generates an operation clock or the like, generates two oscillation signals whose phases are different by 90 degrees, and changes the phase difference between the two. The sub-channel signal is quadrature-modulated while being subtracted. This configuration is common to the N orthogonal demodulation circuits 1251, and therefore, the orthogonal demodulation parameters are also common.

  After the real part and imaginary part time signals are AD-converted, they are supplied to the real part input and the imaginary part input of the FFT circuit 1252. The FFT circuit 1252 converts the input real and imaginary part time signals from time domain signals to frequency domain signals. At this time, the unit subcarrier of the adjacent subchannel remains in the subchannel signal. However, as described above, the residual carrier of the adjacent subchannel is orthogonal to the subchannel to be demodulated, so There is no interference.

  The sub-channel signal converted into the frequency domain by the FFT circuit 1252 is supplied to the equalization circuit 1253 and the transmission path characteristics are equalized. This equalization circuit 1253 is a circuit for correcting frequency characteristics due to multipath, which is inevitable particularly in terrestrial transmission, and estimates transmission characteristics by referring to a known pilot signal inserted in the transmission signal. It has a function to compensate.

The output of the equalization circuit 1253 is supplied to the error correction decoding circuit 1254, where various error correction processes are performed, and the error-corrected subchannel information code sequence is output from the demodulation processing circuit 125- _I , as shown in FIG. Input to the time compression circuits 126 ₋₁ ,..., 126 _-N .

The time compression circuits 126 ₋₁ ,..., 126 _{−N perform} N times time compression processing equal to the number of subchannels (number of divisions) N on the input _subchannel information code sequence. The information code sequence after time compression becomes a continuous encoded sequence (transport stream), which is input to the next-stage synthesis circuit 127, where the synthesis process is executed. Hereinafter, the time compression circuit 126 _-1, ..., the transport stream of the sub-channels output from the 126 _-N TS _-1, ..., denoted as TS _-N, denoted a transport stream is restored after synthesis and TS0 To do.

FIG. 10A to FIG. 10C are time charts showing transport streams TS ₋₁ ,..., TS _−N before time compression in units of TS packets. FIG. 10D is a time chart showing the transport stream TS0 formed by combining the transport streams TS ₋₁ ,..., TS _-N after time compression, in units of TS packets.
The synthesizing circuit 127 multiplexes the TS packets of the transport streams TS ₋₁ ,..., TS _−N supplied synchronously from N inputs in the order of input, and sends them to the outputs in a fixed order. It is. For example, N TS packets that are synchronously input at a certain point in time are divided in the order of transport streams TS ₋₁ ,..., TS _-N , and N packet sequences are arranged in series in the order of division and transmitted. When this synchronization operation is repeated sequentially, one time-series transport stream TS0 is reproduced and output from the synthesis circuit 127.

However, there is a possibility that an error occurs in the order of arranging the TS packets of the subchannel information code sequence when arranging them in series in time. The detection and correction (rearrangement) of the erroneous TS packet order will be described below.
A TS packet after OFDM modulation is composed of 188 bytes, and the first 4 bytes of the TS packet are an area called a header, and various packet control information is described in this header. More specifically, the header consists of an 8 bit “sync byte”, 1 bit “transport error indication”, 1 bit “payload unit start indication”, 1 bit “transport priority”, 13 bit It consists of “packet ID”, 2-bit “transport scramble control”, 2-bit “adaptation field control”, and 4-bit “continuity counter”.

The 184 bytes excluding the header is an adaptation field that is an extension of packet control information or a payload that is actual transmission information.
TS packets include
(1) Packet composed of header and payload (when adaptation field control information is “01”),
(2) A packet composed of a header and an adaptation field (when the adaptation field control information is “10”),
(3) Packet composed of header, adaptation field, and payload (when adaptation field control information is “11”)
There are three ways.
The TS packet having the structure (1) to (3) can be identified by the 2-bit “adaptation field control information” as described above.

In the case of packets including payload, that is, (1) and (3), the continuity counter value that is a 4-bit cyclic counter existing in the header is sequentially increased. Therefore, by monitoring the adaptation field control information and the continuity counter value in the header, it is possible to control the packet order when reconstructing a plurality of TS packets transmitted on the secondary channel. That is, when the TS packet is reconstructed, the packet structure is recognized by the adaptation field control information of the TS packet to be output next, and if the TS packet has the structure of (1) or (3), the current continuity If a TS packet having a continuity counter value larger than the counter value is selected and the TS packet has the structure of (2), a packet having a value equal to the current continuity counter value is selected and the packet is selected. Try to rebuild.
The numbers in the TS packet shown in FIG. 10 represent the continuity counter value. Although detailed explanation is omitted here, time-axis compression in units of packets is detected from each subchannel information code sequence by detecting a synchronization byte (8-bit synchronization unique word) described at the beginning of the packet header. Thus, packet synchronization can be established and time compression processing can be easily performed using a memory.

The transport stream TS0 synthesized in this way and reconstructed as necessary according to TS packets is sent from the respective demodulation processing circuits 125 _-1 ,..., 125 _-N to the corresponding decoding circuits 13 _{-1 to} 13. _The high-efficiency-encoded code sequence (transport stream TS0) that is output to _-N and transmitted from the plurality of transmission devices 1 is reproduced as a video signal and an audio signal, respectively. Information of the reproduced video signal and audio signal is displayed or output as an image or audio from the monitors 1000 _{-1 to} 1000 _-N , respectively.

When transport streams are output from all reception processing units 12 ₋₁ , 12 ₋₂ ,..., 12 _-N , the number N of subchannels constituting each transport stream is 1, and N subchannels are included. Since this is limited to the case where channel signals # 1 to #N are wirelessly transmitted and received and processed without division, such a case is rather rare. Since the frequency band of the subchannel signals # 1 to #N is a unit for sending the minimum information, a radio transmission signal such as a high-resolution screen is usually composed of a plurality of subchannel signals. Note that in that case there is no need to connect a monitor to some playback channels.

The wireless transmission / reception apparatus according to the present embodiment includes several wireless transmission apparatuses (wireless cameras) 1 having the basic configuration described above, and one (or a plurality) of wireless reception apparatuses 10 on the base station side described above. The
The wireless transmitter / receiver is characterized in that the number of transmission channels and the configuration of transmission channels to be used can be flexibly changed. Hereinafter, the configuration and operation for change control of the transmission device 1 and the wireless reception device 10 and an operation example will be described in this regard.

As shown in FIG. 7, the radio receiving apparatus 10 on the base station side has a transmission function for transmitting control information such as changes in addition to the reception function described above, that is, a transmission processing unit 15 and a transmission antenna (transmission antenna: Ant). .) With 11B.
The transmission processing unit 15 includes a modulation circuit (Mod.) 151, a transmission frequency conversion circuit 152, a local oscillation circuit 153, and a transmission high frequency circuit (TRRF) 154. The control information after modulation is output from the transmission high-frequency circuit 154 and transmitted to the wireless camera 1 by radio from the transmission antenna 11B.

  On the other hand, on the wireless camera 1 side, the reception processing unit 5 shown in FIG. 1 includes a reception high-frequency circuit (RXRF) 51, a reception frequency conversion circuit 52, a local oscillation circuit 53, and a demodulation circuit (Demod.) 54. The demodulated control information is output from the demodulation circuit 54 and input to the control circuit 7.

At the time of use, an operator in the base station selects video and audio with high priority to be actually transmitted as a broadcast wave while watching the monitors 1000 _{-1 to} 1000 _-M . When it is necessary to change the system due to this selection, when the control circuit 14 detects the operation of the operator, the control circuit 14 controls the transmission bandwidth and the transmission frequency for each wireless camera in association with this operation. Set the information. The control information S14 for each wireless camera generated by the control circuit 14 is modulated by the modulation circuit 151, and further transmitted through the transmission frequency conversion circuit 152 and the transmission high-frequency circuit 154 for frequency conversion using the oscillation signal from the transmission local oscillation circuit 153. Sent to each wireless camera.

  The transmitted control signal is captured by the antenna 4A shown in FIG. 1, amplified to an appropriate level by the reception high-frequency circuit 51 via the diplexer 4B, and further frequency-converted by the oscillation signal from the reception local oscillation circuit 53. After conversion to an appropriate intermediate frequency by the conversion circuit 52, the control signal is demodulated by the demodulation circuit 54, and the control signal from the base station is input to the control circuit 7. The control circuit 7 extracts only the control signal related to its own control from the control signal, controls the encoding speed for the video encoding circuit 32 and the audio encoding circuit 34, and also the dividing circuit 36 and the transmission local oscillation circuit 40 to control the bandwidth. Further, the transmission high frequency circuit 41 may be controlled to control the transmission frequency.

  FIG. 11 shows an example of the arrangement of frequencies and bandwidths in the case of operating five wireless cameras 1 (hereinafter referred to as # C1, # C2, # C3, # C4, # C5). . 11A shows a normal operation, and FIG. 11B shows a modified example. FIG. 12 shows frequency band allocation of transmission channels during normal operation.

As shown in FIGS. 11A and 12, in this operation example, two wideband transmission channels Ch1 and Ch2 and three narrowband transmission channels Ch3 to Ch5 are regularly assigned. Here, in FIG. 12, the symbol f _BW is the frequency bandwidth of one _subchannel composed of K unit subcarriers. Therefore, the frequency band division number N on the wireless camera 1 side and the wireless reception device 10 side is N = 9. The reception processing circuits 12 _-1 and 12 _-2 of the wireless reception apparatus 10 are set to three frequency bands, and the other reception processing circuits 12 _{-3 to} 12 _-5 are settings without frequency division. Wireless cameras # C1 and # C2 are set to divide the high transmission rate information code sequence for HDTV into three, and other wireless cameras # C3 to # C5 do not divide the low transmission rate information code sequence for SDTV. This is the setting.
Here, all wireless cameras have the same configuration, and the wireless cameras # C3 to # C5 are configured to be changeable from the current SDTV to HDTV.

  The base station can monitor all video and audio signals sent from the five wireless cameras # C1, # C2, # C3, # C4, and # C5, so the operator gives priority to the signal from which wireless camera in the program structure. You can decide what to do. FIG. 11A shows the case where the operator determines that the signals from the wireless cameras # C1 and # C2 are given priority in program production, and assigns the broadband channels Ch1 and Ch2 to the priority wireless cameras # C1 and # C2, respectively. ing. Therefore, any of the images captured by the wireless cameras # C1 and # C2 can be transmitted from the receiving device to the key station with high quality as a transmitted image to the program.

FIG. 11B shows that the operator needs to give priority to the signals from the wireless cameras # C2 and # C3 in program production, and the wireless cameras # C2 and # C3 are assigned wide channels Ch2 and Ch1, respectively. The case where the priority wireless camera is changed by switching from the state of FIG. 11 (A) to the state of FIG. 11 (B) is shown. Since wireless camera # C2 is a priority wireless camera, there is no need to change the channel. Therefore, for example, when the signal of the wireless camera # C1 is actually transmitted on-air among the priority wireless cameras # C1 and # C2 in FIG. 11A, and then the signal of the wireless camera # C2 is transmitted on-air, the operator immediately You can switch between wireless cameras. However, in FIG. 11A, in the case of FIG. 11B in which the wideband channel is switched to the wireless camera # C3, # C4 or # C5 that uses the narrowband channel instead of the priority wireless camera, the signal quality after switching In order to achieve high quality, once the wireless camera to be switched next is assigned Ch2 as a broadband channel in place of the wireless camera # C1, and a certain switching time is required until the signal from the desired wireless camera is stably received. It will not be.
However, in the present embodiment, it is not always necessary to temporarily allocate the broadband channel from the wireless camera in use to another wireless camera. In the present embodiment, when there is a restriction that the wideband channel uses a continuous frequency region, the switching operation as described above is necessary. Since an arbitrary frequency band can be selected due to the configuration of the wireless camera, it is also possible to transmit one wideband image using a plurality of remote frequency bands. In that case, there is no necessity to temporarily free a channel for switching, and there is an advantage that it is easier to operate.

The switching control method between the wireless camera and the receiving device is a configuration using a plurality of N wireless transmission paths as in Patent Document 1 for which the transmitting device and the receiving device have been applied earlier, that is, N transmitting antennas, N The present invention can also be applied to a configuration having N transmitting units, N receiving antennas, and N receiving units. In this case, the receiving apparatus has a function and a configuration for arbitrarily integrating N received signals individually so that transmission channel allocation (association between a wideband or narrowband channel and a radio transmission channel) can be arbitrarily made. Add to. In addition, a function of dividing the information source into packets and transmitting it to a plurality of wireless transmission paths (which can be arbitrarily selected and changed) while maintaining orthogonality, and a function and configuration for changing the transmission rate are added to the transmission apparatus. In this case, if the original information source is the same, even if information is sent as individual radio transmission signals by dividing into a plurality of frequency bands while maintaining orthogonality on the transmission side, the received signal and the information source Is known as control information, it is possible to demodulate and integrate the original information source on the receiving side while maintaining orthogonality. For this purpose, a function and a configuration for transmitting control information for assigning the transmission channel and changing the transmission rate to the transmitting device are added to the receiving device, and the control information is received and received. A control function capable of changing the information source division destination and the selection of a plurality of wireless transmission paths based on the control information, and a configuration therefor are added to the transmission apparatus.
In addition, the operation frequency, its bandwidth, and the operation method are not limited to the above examples.

  The present embodiment has the following many advantages.

Regarding the wireless transmission device 1, first, the control circuit 7 changes the transmission rate of the information code sequence (transport stream TS 0), for example, the coding rate, according to the input control signal, and the transport is made accordingly. The division number M of the stream TS0 can be arbitrarily changed within the range of the maximum division number N or less. At this time, the control circuit 7 controls the frequencies f11 to f1N of the local oscillation signal output from the transmission local oscillation circuit 40 to form an integrated OFDM modulation signal # 0. Therefore, wireless communication in a frequency band suitable for the amount of information of the transport stream to be transmitted becomes possible.
Second, the control circuit 7 can change the frequency of the radio channel signal # 0 in accordance with the input control signal. As a result, in particular, a plurality of received signals can be received, and radio channel signals for each received signal can be properly arranged within a limited frequency bandwidth.
Third, since the transmission signal in which the frequency bands are integrated is an OFDM modulation signal in which a wideband signal is distributed and transmitted to subcarriers of a relatively low frequency, the multipath resistance is high, and the transmission unit is single. An OFDM transmitter with a simple configuration can be realized. The conditions for making a transmission signal one OFDM modulation signal are defined as follows: (1) N error correction coding circuits 381 have the same coding rate, and (2) N interleaving circuits have the same interleaving parameters. (3) N IFFT circuits 383 operate in synchronism, and (4) N guard interval addition circuits 384 operate so as to add a fixed-length guard interval at the same timing within a symbol. (5) It is necessary to set the same symbol length, and (6) modulation processing, in particular, orthogonal modulation is performed with the same clock, and symbols are generated with the same clock. When the six conditions (1) to (6) are satisfied, one radio channel signal becomes one complete OFDM modulated signal. It should be noted that even if some of these conditions are missing, it can be regarded as an OFDM modulated signal, and therefore it is not an essential requirement that the above six conditions be met.
Fourthly, when there are a plurality of transmission apparatuses, there is an advantage that orthogonality is maintained between a plurality of OFDM modulation signals whose frequency bands are adjacent to each other and they do not interfere with each other.

Next, advantages related to the wireless receiver 10 will be described.
First, when the band separation circuits 122 _{-1 to} 122 _-N separate the frequency band of the received signal for each frequency bandwidth of f 0, the received signal is an OFDM modulation signal. Even if a harmonic having a subcarrier interval as a unit is generated as a noise component, there is no influence on the received signal because the harmonic serving as the noise component and the adjacent unit subharmonic of the separated received signal are orthogonal to each other. This noise component can be effectively removed by a low-pass filter in the subsequent stage.
Second, a plurality of reception processing units 12 _{-1 to} 12 _-N are provided, each configured to be able to extract signals in different frequency bands. More specifically, when a plurality of OFDM modulated signals, each of which is an individual radio channel signal, are received, the plurality of signals may be received and input to the plurality of reception processing units 12 _{-1 to} 12 _-N. Each reception processing unit can select only the separated signals corresponding to the preset channels and synthesize them after demodulation. In order to perform selection of the signals, a total of N local oscillation circuits 124 provided in each reception processing unit are frequency conversion circuits 123 _{-1 to} 123 _-N specified according to the input control signal. The output control for stopping the output of the local oscillation signals f11 to f1N to be output in accordance with the frequency band used by a preset channel is configured. In the control of this time is controlled so as not to frequency convert the signal of the same frequency band overlap all of the frequency conversion circuit 123 _-1 ~123 _-N of N reception processing unit 12 _-1 to 12 _-N . Since the frequency-converted signals are arranged as baseband signals or IF signals in a low frequency band, these signals can be demodulated and integrated in the same frequency band. A control circuit 14 that performs these controls is included.
Thirdly, it is possible to arbitrarily set and change the frequency bandwidth according to the information amount of a plurality of channels and the frequency band to be used. More specifically, the control circuit 14 includes a transmission processing unit 15 and a transmission antenna 11B as a configuration for transmitting control information S14 instructing channel organization to the wireless transmission device 1, and according to the newly set channel organization. Generation of a transmission signal can be instructed to the plurality of wireless transmission devices 1 side. The control circuit 14 gives control information of a combination of a signal to be stopped and a signal to be output among the local oscillation signals f11 to f1N to each of the local oscillation circuits 124 of each reception processing circuit according to the new channel organization. Therefore, even when a plurality of signals are received from a plurality of radio transmission apparatuses 1, it is possible to select the divided signals corresponding to the new channel organization for each received signal. After that, when receiving a plurality of transmission signals of a new channel organization generated and sent in response to the transmission of the control signal described above, the signals after division are selected corresponding to the new channel organization, Integrated after modulation.
_Fourthly , each of the _N reception processing units 12 _{-1 to} 12 _-N is further provided with a transmission path complex parameter and a demodulation parameter of _N demodulation processing circuits 125 _{-1 to} 125 _-N , respectively. Since N demodulation processing circuits are set to be the same, uniform and stable processing can be performed.
Fifth, even if the order of TS packets is changed for some reason, it can be repaired by referring to the adaptation field control information and continuity counter value of the TS packets.

The wireless transmission / reception apparatus according to the present embodiment uses a plurality of wireless cameras as the wireless transmission apparatus 1 and receives each wireless transmission signal from the plurality of wireless cameras. Each reception processing unit of the base station as the wireless reception apparatus 10 The organization and combination of the wideband channel signal and the narrowband channel signal output from each of the output channels 12 _{−1 to} 12 _−N can be arbitrarily changed. Thereby, the wireless camera system which can be operated flexibly can be constructed.

It is a block diagram which shows the structure of the wireless camera as a receiver concerning embodiment. (A) to (E) are time charts showing information code sequences in units of TS packets in order to explain division and time expansion when the number of output channels N of the division circuit is four. It is a block diagram which shows the structure of the modulation processing circuit concerning embodiment. It is a block diagram which shows the structure of the orthogonal modulation part in the modulation processing circuit concerning embodiment. (A)-(E) are schematic diagrams which show integration of a frequency band. (A)-(C) are figures which show the transmission signal after integration of a frequency band. It is a block diagram which shows the structure of the receiver concerning Embodiment. It is a block diagram which shows the structure of the demodulation processing circuit concerning embodiment. (A)-(D) are figures which show frequency band separation and frequency conversion typically. (A) to (C) are time charts showing the transport stream before time compression in units of TS packets, and (D) is a time chart showing the transport stream TS0 synthesized and formed after time compression in units of TS packets. is there. (A) And (B) is a figure which shows the example of arrangement | positioning of the frequency and a bandwidth in the case of operating the five wireless cameras in the wireless transmitter / receiver of embodiment. It is a figure which shows the frequency band allocation of the transmission channel at the time of normal operation (FIG. 11 (A)).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless camera (wireless transmission apparatus), 4 ... Transmission / reception part (transmission part), 5 ... Reception processing part, 10 ... Wireless reception apparatus, 12 < _-1 > _-12 <_-N> Reception processing circuit, 14 ... Control circuit, 15 ... Transmission processing unit 36 ... division circuit, 37 _{-1 to} 37 _-N ... time expansion circuit, 38 _{-1 to} 38 _-N ... modulation processing circuit, 39 _{-1 to} 39 _-N ... band integration circuit, 40 ... local oscillation circuit , 122 _{-1 to} 122 _-N ... band separation circuit, 123 _{-1 to} 123 _-N ... frequency conversion circuit, 124 ... local oscillation circuit, 125 _{-1 to} 125 _-N ... demodulation processing circuit, 126 _{-1 to} 126 _-N ... time compression circuit, 127 ... synthesis circuit, 381 ... error correction coding circuit, 383 ... inverse fast Fourier transform (IFFT) circuit, 384 ... guard band addition circuit, 385 ... quadrature modulation unit, 3851, 3852 ... transpiration circuit, 3853 ... adder circuit, 3854 ... local departure Oscillation circuit, 391 _{-1 to} 391 _-N ... frequency conversion circuit, 1251 ... orthogonal demodulation circuit, 1252 ... fast Fourier transform (FFT) circuit, TS0 ... transport stream (formed information code sequence), TS _{-1 to} TS _-N : divided transport stream, S39: integrated transport stream, S14: control signal

Claims (9)

A radio receiving apparatus that receives a radio transmission signal, demodulates the radio transmission signal, and extracts an information code sequence,
A band separation circuit that divides the received wireless transmission signal into a plurality of subchannel signals having different frequency bands;
A plurality of frequency conversion circuits that perform frequency conversion for each sub-channel signal and align it to a baseband or a fixed frequency band;
A plurality of demodulation processing circuits for orthogonally demodulating the subchannel signals after frequency conversion and converting them into information code sequences;
A combining circuit that generates one information code sequence by combining the plurality of information code sequences when there are a plurality of information code sequences after the orthogonal demodulation;
A wireless receiver. Each of the carrier wave of the wireless transmission signal and the carrier wave of the divided subchannel signal is composed of a unit subcarrier group which is a set of a plurality of unit subcarriers having a constant frequency interval f0 adapted to the OFDM modulation scheme,
The radio reception apparatus according to claim 1, wherein when the band separation circuit performs division, the radio transmission signal is divided in different frequency bands having a constant width of f 0 × K (K: a fixed number). A local oscillation circuit that generates a plurality of local oscillation signals having different frequencies in units of the f0 × K and outputs the local oscillation signals to the plurality of frequency conversion circuits;
The local oscillation circuit is configured to be capable of performing output control for stopping output of the local oscillation signal output to a frequency conversion circuit specified in accordance with an input control signal. Wireless receiver. A plurality of reception processing units including the band separation circuit, the plurality of frequency conversion circuits, the plurality of demodulation processing circuits, and the combining circuit;
The radio reception apparatus according to claim 3, wherein all of the frequency conversion circuits of the plurality of reception processing units are controlled so as not to frequency-convert subchannel signals in the same frequency band in accordance with an input control signal. . The radio reception apparatus according to claim 1, wherein each of the plurality of demodulation processing circuits has a common demodulation processing parameter. The radio reception apparatus according to claim 5, wherein each of the plurality of demodulation processing circuits has the same error correction decoding circuit and the same deinterleave circuit. The synthesizing circuit inputs a plurality of information code sequences constituting a transport stream (TS) defined in the MPEG-2 standard, and inputs the plurality of information code sequences into a TS packet defined in the MPEG-2 standard. The wireless receiver according to claim 1, wherein the wireless receiver is combined as a unit. The radio reception apparatus according to claim 1, further comprising a time compression circuit for increasing the transmission rate of the information code sequence demodulated from the subchannel signal after division according to the number of divisions, for each output channel of the band separation circuit. . 8. The radio according to claim 7, wherein when combining the plurality of information code sequences in units of TS packets, the order of combining is controlled with reference to adaptation field control information and a continuity counter value of a header constituting the TS packet. Receiver device.

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