JPH1155168A - Antenna diversity method for receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of reception characteristics at the time of antenna switching. SOLUTION: During reception through an antenna 1, based on the transmission frame signal of DAB outputted from a demodulator 5, a channel decoder 6 separates a subchannel related to the program desired by a user and outputs DAB audio frame data through time deinterleave, error detection/correction, and descramble. A system controller 7A checks received electric field intensity (E) detected by a received electric field intensity detection circuit 15. When the E is higher than a fixed value, the antenna is not switched based on the satisfactory reception state of the antenna 1. However, when E becomes lower than the fixed value, it is determines that the reception state of the antenna 1 under reception at present has become worse. In this case, based on an effective symbol period signal inputted from the demodulator 5, an antenna selector 3 is controlled for switching to the side of an antenna 2, immediately after the end of an effective symbol period in the next transmission frame, so that the reception state can be kept satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an antenna for a receiver.
The present invention relates to a diversity method, in particular, an OFDM system in which a transmission symbol is composed of a guard interval and an effective symbol.
The present invention relates to an antenna diversity method for a receiver that receives a modulated wave.

[0002]

2. Description of the Related Art In Europe, DAB (Digital Audio Broadcasting) is used.
dcasting) has been put to practical use. In this DAB, OFDM (Orthogonal Frequency Division Multiplexing Modulation;
A modulation method called thogonal frequency division multiplexing is used, and a transmission symbol is composed of a guard interval and an effective symbol, thereby enabling ghost-resistant reception. Each DAB carrier is DQPS
It is K-modulated.

FIG. 5 shows a format of a transmission frame signal in transmission mode 1 of DAB. First, a NULL symbol of 1.297 ms and a phase reference symbol (Phas
ereference symbol), followed by 75 OFDM symbols of 1.246 ms each. Other than NULL symbols are transmission symbols,
The first 0.246 ms is the guard interval, and the rest is the effective symbol. The n = 1st transmission symbol is a phase reference symbol, and the n = 2 to 4th transmission symbols are FIC (high-speed information) for transmitting information necessary for the receiver to select a desired program and auxiliary information for the program. Channel: Fast I
nformatiom Channel), and n = 5 to 76th transmission symbols are MSCs (Main Service Channels) for multiplexing and transmitting voice and data sub-channels (Sub Channels). One sub-channel corresponds to one program, and the FIC includes structural information indicating how the sub-channels are multiplexed in the MSC. Can be extracted.

FIG. 6 shows an antenna diversity DAB.
It is a block diagram of a receiver. One of the received signals selected by the antenna selector 3 among the antennas 1 and 2 is sent to the front end 4, where the DAB broadcast signal desired by the user is amplified and converted into an intermediate frequency signal. The intermediate frequency signal is subjected to demodulation of the I and Q signals by the demodulator 5 to reproduce the transmission frame signal shown in FIG. 5, and further to the detection of synchronization and generation of various timing signals, and the FIC and MSC portions in FIG. Output as a demodulated signal. The timing signal output from the demodulator 5 includes the synchronization detection signal SD and the effective symbol period signal ES of each transmission symbol shown in FIG. The demodulated output of the demodulator 5 is input to the channel decoder 6 together with the synchronization detection signal SD and the effective symbol period signal ES.
The IC and the MSC are decoded.

More specifically, in the case of the transmission mode 1, the channel decoder 6 first performs frequency deinterleaving, DQPSK symbol demapping, guard interval removal, and FIC / MSC separation, and the three effective symbols of the FIC are three. After being divided into four equal parts in total, it is processed through error detection / correction (Viterbi decoding) and descrambling to obtain 1
Two FIBs (Fast Information B)
lock), and Fig (Fast Infor
The data is output to the system controller 7 of the microcomputer in the form of packet data called a “mation group”. on the other hand,
The MSC effective symbol is divided into 18 symbols and reconstructed into four CIFs (Common Interleaved Frames). Each CIF has a plurality of Sub Channels
And one sub-channel corresponds to one program. When the user selects a desired program with the key operation unit 8, the system controller 7 refers to the information of the FIC and outputs the designation information of the sub-channel corresponding to the desired program, and the channel decoder 6 selects the system controller from the four CIFs. After separating the sub-channel specified by 7,
DAB by performing time deinterleaving, error detection / correction (Viterbi decoding), error counting, and descrambling
The audio frame data is decoded, the error count value M of the sub-channel corresponding to the desired program is output to the system controller 7, and the decoded DAB audio frame data is output to the audio decoder 9.

An audio decoder 9 decodes DAB audio frame data and outputs audio data for two channels. This audio data is D /
The A / D converter 10 performs D / A conversion, and the power is amplified by the power amplifiers 11 and 12 for each channel.
The sound is output from 4.

The front end 4 has a built-in reception electric field strength detection circuit 15.
Is received by the system controller 7
Is output to The system controller 7 uses the received field strength signal and the error count value M input from the channel decoder 6 to find an antenna with a good reception state,
The antenna selector 3 is switched. The first specific switching method will be described. When the reception state of the antenna currently used for reception deteriorates below a certain level, the antenna is switched to another antenna. The reception electric field intensity E indicated by the reception electric field intensity signal input from the reception electric field intensity detection circuit 15 and the error count value M in the error detection / correction of the sub-channel of the desired program input from the channel decoder 6 are periodically monitored. When E becomes equal to or less than a certain value or M becomes equal to or more than a certain value, it is determined that the reception state of the antenna currently used for reception has deteriorated, and the antenna selector 3 is set in the opposite direction. Switch to the antenna side to keep good reception.

The second specific switching method is to periodically detect and compare the reception state of each antenna and switch to the antenna having a better reception state. For example, the reception electric field intensity Ea indicated by the reception electric field intensity signal input from the reception electric field intensity detection circuit 15 while the desired program is being received while being switched to the antenna 1, and the desired electric field intensity input from the channel decoder 6. An error count value Ma due to error detection / correction of a program sub-channel is stored. Next, the antenna selector 3 was temporarily switched to the antenna 2 whose reception state was previously set to the best, and was input from the reception field strength detection circuit 15 while receiving a desired program. The received electric field intensity Eb indicated by the received electric field intensity signal and the error count value Mb for error detection / correction of the sub-channel of the desired program input from the channel decoder 6 are stored.

If Ea> Eb + e (e is a positive fixed value), it is determined that the antenna 1 has a better reception state, and the antenna selector 3 is returned to the antenna 1 side. If Eb> Ea + e, it is determined that the reception state of the antenna 2 is better, and the antenna selector 3 is kept at the antenna 2 side. When Ea> Eb + e is not satisfied and Eb> Ea + e is not satisfied, if Ma <Mb, the antenna 1 is considered to have a better reception state, and the antenna selector 3 is returned to the antenna 1 side. <Ma
If so, it is determined that the antenna 2 has a better reception state, and the antenna selector 3 is kept at the antenna 2 side to maintain a good reception state.

[0010]

However, in the above-described conventional antenna diversity, when the first switching method is used, it is uncertain when the antenna is switched.
For example, the switching may be performed in the middle of an effective symbol related to a desired program of the MSC in the transmission frame in FIG. 5 or in the middle of an effective symbol of the FIC. At this time, since the received waveform becomes discontinuous before and after the switching, the error rate increases for a desired sub-channel, and the sound is cut off.
The error rate increases for each FIC,
There has been a problem that the receiving characteristics are deteriorated, for example, the SC structure information cannot be obtained.

Also, in the second switching method, when the reception state is detected by switching to an antenna other than the antenna determined to be good last time, and when the reception state at the antenna is considerably poor, the transmission frame of the transmission frame is detected. The reception waveform of the effective symbol related to the desired program of the MSC or the effective symbol of the FIC deteriorates, and the error rate increases for the desired sub-channel.
The sound cuts out and the error rate increases per FIC,
There has been a problem that reception characteristics are deteriorated, for example, the supplementary information of the program and the structure information of the MSC cannot be obtained. The present invention has been made in view of the above-described problems of the related art, and has as its object to provide an antenna diversity method for a receiver that does not deteriorate reception characteristics.

[0012]

According to the antenna diversity method of the receiver according to the first aspect of the present invention, antenna diversity can be performed by switching antennas, and OFDM modulation in which transmission symbols are composed of guard intervals and effective symbols. In a receiver for receiving a wave, antenna switching is performed in an unnecessary section of the OFDM modulated wave. This avoids a discontinuous reception waveform in a section necessary for reception in a transmission frame such as an effective symbol relating to a desired program, so that reception characteristics do not deteriorate with antenna switching, and It is possible to always keep good reception by making the most of diversity.

In the antenna diversity method for a receiver according to the second aspect of the present invention, the reception diversity of each antenna is detected and compared while switching a plurality of antennas, and the antenna diversity to be received by switching to the best antenna is obtained. Possible, in a receiver that receives an OFDM modulated wave whose transmission symbol is composed of a guard interval and an effective symbol, it is not necessary to detect the reception state of the antenna other than the previously determined best one among the OFDM modulated waves. It is characterized in that it is performed in a suitable section. As a result, it is possible to prevent a section necessary for reception in a transmission frame, such as an effective symbol relating to a desired program, from being received by an antenna having a poor reception state as much as possible, and to avoid deterioration of reception characteristics due to detection of the reception state of the antenna. It is possible to always keep the best reception state by making the most of antenna diversity.

In the antenna diversity method for a receiver according to the third aspect of the present invention, the antenna diversity detecting and comparing the reception state of each antenna while switching a plurality of antennas, and switching to the best antenna for reception. In a receiver that receives an OFDM modulated wave whose transmission symbol is composed of a guard interval and an effective symbol, antenna switching and detection of the reception state of an antenna that is not currently being used can be performed by receiving an OFDM modulated wave. In an unnecessary section. By this, while avoiding receiving the necessary section in the transmission frame, such as an effective symbol related to the desired program, with an antenna having a poor reception state as much as possible,
It is also possible to prevent the antenna switching in this section, to prevent the reception characteristics from being deteriorated due to the detection of the antenna reception state and the antenna switching, and to always keep the best reception state by making the most of the antenna diversity. it can.

In the first to third aspects, the section unnecessary for reception in the OFDM modulated wave may be, for example, a NULL symbol section in a transmission frame or a guard interval section. Further, the phase reference symbol in the synchronizing signal, the transmission symbol relating to the FIC, and the transmission symbol relating to the desired program in the MSC are defined as a section required for reception, and one or a plurality of other consecutive transmission symbol sections or the transmission symbol It may be one of the effective symbol sections in the middle.

[0016]

Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an antenna diversity DAB receiver according to the present invention, and the same components as those in FIG. 6 are denoted by the same reference numerals. The system controller 7A having a microcomputer configuration receives a reception field strength signal from the reception field strength detection circuit 15 of the front end 4, inputs FIC packet data and an error count value M of a designated sub-channel from the channel decoder 6, and demodulates. The synchronization detection signal SD and the effective symbol period signal ES are input from the device 5. The system controller 7A outputs designation information of a sub-channel corresponding to the desired program to the channel decoder 6 with reference to the FIC for the desired program selected by the key operation unit 8,
The sub-channel of the desired program is separated from the four CIFs reconstructed from the MSC, time-deinterleaved, error-detected / corrected, error-counted, and descrambled to decode the DAB audio frame data and output to the audio decoder 9.

Further, the system controller 7A receives, for each transmission frame, a reception field strength signal input from the reception field strength detection circuit 15 and an error count value in error detection / correction of a sub-channel related to a desired program input from the channel decoder 6. Using M, it is determined whether the reception condition of the antenna currently used for receiving the desired program is deteriorating. If not, the antenna switching is not performed. The antenna selector 3 is switched to the other in a NULL symbol section or a guard interval section in the synchronization signal, which is a section unnecessary for receiving the signal (see FIG. 2), and the reception state is kept good. The other components of the antenna diversity DAB receiver are configured exactly the same as in FIG.

Next, the operation of the above embodiment will be briefly described with reference to FIG. Note that the front end 4
Is tuned to a desired DAB broadcast (transmission mode 1), and the data of the desired program selected by the key operation unit 8 is included in transmission symbols of n = 5 to 7 in the transmission frame. Shall be. Further, it is assumed that the antenna selector 3 has been switched to the side of the antenna 1 where the reception state was good.

The received signal of the antenna 1 is sent to the front end 4 via the antenna selector 3 and the D signal desired by the user is transmitted.
The high-frequency amplification and conversion of the AB broadcast signal into an intermediate frequency signal are performed. The intermediate frequency signal is subjected to demodulation of the I and Q signals by the demodulator 5 to reproduce the transmission frame signal shown in FIG. 2, and further to the detection of synchronization and generation of various timing signals, and the FI signal shown in FIG.
The C and MSC portions are output as demodulated signals. The timing signal output from the demodulator 5 includes a synchronization detection signal SD,
An effective symbol period signal ES of each transmission symbol is included. The demodulated output of the demodulator 5 is input to the channel decoder 6 together with the synchronization detection signal SD and the effective symbol period signal ES, and FIC and MSC are decoded.

The system controller 7A transmits a desired program selected by the key operation unit 8 to the channel decoder 6
The sub-channel designation information corresponding to the desired program is output to the channel decoder 6 by referring to the FIC input from the MSC, the desired sub-channel is separated from the four CIFs reconstructed from the MSC, and time deinterleaving,
The DAB audio frame data is decoded by performing error detection / correction, error counting, and descrambling, and output to the audio decoder 9. Audio decoder 9
Decodes DAB audio frame data and outputs audio data for two channels. This is D
D / A conversion by the A / A converter 10 and the power amplifiers 11 and 1
After the power is amplified by 2, the sound is output from the speakers 13 and 14.

As described above, while the desired program is being received by the antenna 1, the system controller 7A outputs, for each transmission frame, the reception electric field intensity signal input from the reception electric field intensity detection circuit 15 at an appropriate timing in one transmission frame. The received electric field intensity E indicated by the received electric field intensity signal is stored (see t _{1 in} FIG. 2), and an error count value in error detection / correction for a sub-channel of a desired program output from the channel decoder 6 is input. and stored by entering the M (see t ₂ in FIG. 2), followed by the E there is more than a predetermined constant value, and when M is equal to or less than a predetermined constant value, the reception condition of the antenna 1 is good, Do not switch antennas.

On the other hand, if E is less than a certain value,
Alternatively, when M becomes a certain value or more, it is determined that the reception state of the antenna 1 currently used for reception has deteriorated. In this case, the effective symbol period signal E input from the demodulator 5
Based on S, then immediately after the effective symbol period in the transmission frame has been completed, let switched to the side of the antenna 2 and controls the antenna selector 3, (see t ₃ in FIG. 2) to keep the good reception state.

After switching to the antenna 2, the system controller 7A again returns to the reception electric field strength detection circuit 15 at an appropriate timing in one transmission frame for each transmission frame.
The received electric field intensity signal input from the CPU 1 is input, the received electric field intensity E indicated by the received electric field intensity signal is stored (see t _{1 in} FIG. 2), and an error relating to the sub-channel of the desired program output from the channel decoder 6 is output. type and stores the count value M (see t ₂ in FIG. 2), followed by, E there is more than a predetermined constant value, and when M is equal to or less than a predetermined constant value, the reception condition of the antenna 2 is better The antenna is not switched. On the other hand, if E falls below a certain value,
Alternatively, when M becomes a certain value or more, it is determined that the reception state of the antenna 2 currently used for reception has deteriorated. In this case, the effective symbol period signal E input from the demodulator 5
Based on S, then immediately after the effective symbol period in the transmission frame has been completed, let switched to the side of the antenna 1 by controlling the antenna selector 3, (see t ₃ in FIG. 2) to keep the good reception state.

As described above, according to the above-described embodiment, antenna switching is always performed in N frames in the transmission frame.
Since it is performed in the UL symbol section or the guard interval section, the effective symbol in the phase reference symbol and F
For both the effective symbol in the IC and the effective symbol related to the desired program in the MSC, the reception waveform is prevented from being discontinuous due to the antenna switching, and the reception characteristics do not deteriorate with the antenna switching. -It is possible to always keep good reception by making the most of diversity.

As a modification of the above-described embodiment, the antenna switching may be performed during an effective symbol related to a program other than the desired program in the MSC of the transmission frame. That is, when it is determined that the reception state of the antenna currently being received has deteriorated at a certain time, the effective symbol position N in the MSC of the transmission frame corresponding to an arbitrary program other than the desired program is obtained by referring to the FIC. . Then, in the effective symbol period signal ES, the rising edge is counted from the next of the synchronization detection signal SD, and when the count value becomes N-1, antenna switching may be performed (for example,
If N = 11, reference t ₄ in FIG. 2). Even in this case, the received waveform of each of the effective symbol in the phase reference symbol in the transmission frame, the effective symbol in the FIC, and the effective symbol related to the desired program in the MSC becomes discontinuous due to the antenna switching. Is avoided, and the reception characteristics do not deteriorate with antenna switching.
It is possible to always keep good reception by making the most of diversity.

The determination as to whether or not the reception state of the currently receiving antenna has deteriorated can be made based on any one of the reception electric field strength E and the error count value M in the error detection / correction of the sub-channel related to the desired program. The reception field strength E can be detected at any time, but the error count value M is output by the channel decoder 6 after the channel decoder 6 has completed error detection / correction for the sub-channel of the desired program. If it is determined that the reception state is deteriorating only by the reception electric field strength E, the antenna switching can be performed promptly when the reception state is deteriorating).

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of an antenna diversity DAB receiver according to the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. The system controller 7B of the microcomputer configuration includes the front end 4
, The FIC packet data and the error count value M for error detection / correction of the designated sub-channel from the channel decoder 6B, and the synchronization detection signal from the demodulator 5. SD and an effective symbol period signal ES are input.

The system controller 7B has a FIC
In the guard interval before the first valid symbol in the MSC corresponding to the desired program selected by the key operation unit 8 is started, the antenna selector 3 switches the antenna of the antenna whose reception state was previously determined to be the best. Side, and for the desired program selected by the key operation unit 8,
By referring to the FIC, the sub-channel designation information corresponding to the desired program and the output ON command of the DAB audio frame data relating to the sub-channel of the desired program are output to the channel decoder 6B, and the four Cs reconstructed from the MSC are output.
A desired sub-channel is separated from the IF, time deinterleaving, error detection / correction, error counting, and descrambling are performed to decode a DAB audio frame and output to the audio decoder 9. Then, while the antenna selector 3 was previously switched to the side of the antenna for which the reception state was determined to be the best, the reception field strength signal was input from the reception field strength detection circuit 15 and the reception field strength indicated by the reception field strength signal was indicated. Ea is stored, and an error count value M in sub-channel error detection / correction for a desired program output from the channel decoder 6 is input and stored as Ma.

Further, the system controller 7B
C, any one of the programs other than the desired program selected by the key operation unit 8 and located at a position slightly distant from the desired program when viewed on the transmission frame is used as a reception state detection back program (hereinafter, referred to as “ The abbreviated program for detection is abbreviated), the effective symbol position in the MSC corresponding to the program for detection is determined in advance, and the position before the first effective symbol in the MSC corresponding to the program for the detection is started. During the guard interval, the antenna selector 3 is switched to the side opposite to the antenna whose reception state was previously determined to be the best, and F
Referring to the IC, the designation information of the sub-channel corresponding to the counter-program for detection and the D
The output off command of the AB audio frame data is output to the channel decoder 6B, and the sub-channel of the program for detection specified by the system controller 7B is separated from the four CIFs reconstructed from the MSC, thereby performing time deinterleaving, error detection / Correction, error counting, descrambling, and output of the error count value (at this time, the channel decoder 6B turns off the output based on the output off command, and sends the DAB audio frame data corresponding to the counter program for detection to the audio decoder 9). Is not output). Then, while the antenna selector 3 was previously switched to the side opposite to the antenna whose reception state was determined to be the best, the reception field strength signal was input from the reception field strength detection circuit 15 and the reception field indicated by the reception field strength signal was received. Electric field strength E
b, and the error count value M in the error detection / correction of the sub-channel relating to the counter-program for detection output from the channel decoder 6 is input and stored as Mb.

The system controller 7B sets the antenna selector 3 once in the guard interval section after the end of the last valid symbol corresponding to the MSC detection program in the transmission frame, and once determines the antenna which has previously determined the reception state to be the best. Back to the side. First, the magnitude relationship between the received electric field strengths Ea and Eb is checked, and Ea> Eb + e
(E is a certain positive fixed value), and if YES, the same antenna as the one for which the previous reception state was determined to be the best is assumed to be in the good reception state again, and the antenna selector 3 is set to the previous reception state. Is maintained on the side of the antenna which is determined to be the best, and conversely, if Eb> Ea + e, it is determined that the reception state is better for the antenna opposite to the one for which the reception state was previously determined to be the best, and the antenna selector 3 Is switched to the side opposite to the last time that the reception state was determined to be the best, thereby maintaining a good reception state.

If Ea> Eb + e and not Eb> E
If it is not a + e, after inputting Mb, the magnitude relationship between the error count values Ma and Mb is checked. If Ma <Mb, the same antenna that was previously determined to be in the best reception state is now in the reception state. Is good, the antenna selector 3 is kept on the side of the antenna for which the reception state was previously determined to be the best, and conversely, if Mb <Ma, the antenna of the opposite antenna to the one for which the previous reception state was determined to be the best was determined. Assuming that the receiving state is better, the antenna receiving unit 3 switches the antenna selector 3 to the opposite side from the last time that the receiving state was determined to be the best, thereby maintaining the good receiving state. Antenna diversity DA
The other components of the B receiver are configured exactly the same as in FIG.

Next, the operation of the above embodiment will be briefly described with reference to FIG. Note that the front end 4
Is tuned to a desired DAB broadcast (transmission mode 1), and the data of the desired program selected by the key operation unit 8 is included in n = 8 to 10 transmission symbols in the transmission frame. Shall be. It is also assumed that the antenna selector 3 has been switched to the side (position a) of the antenna 1 at the start of a certain transmission frame, the reception state of which was determined to be the best in the previous detection and comparison of the reception state.

The signal received by the antenna 1 is transmitted to the front end 4
The DAB broadcast signal desired by the user is amplified and converted into an intermediate frequency signal. The intermediate frequency signal is subjected to demodulation of the I and Q signals by the demodulator 5 to reproduce the transmission frame signal shown in FIG. 4, and further to the detection of synchronization and generation of various timing signals, and the FIC and MSC portions in FIG. Output as a demodulated signal. The timing signal output from the demodulator 5 includes a synchronization detection signal SD and an effective symbol period signal ES of each transmission symbol. The demodulated output of the demodulator 5 is input to the channel decoder 6 together with the synchronization detection signal SD and the effective symbol period signal ES, and FIC and MSC are decoded.

The system controller 7B determines transmission symbol positions k _{1 to} k _i in the MSC corresponding to the desired program selected by the key operation unit 8 with reference to the FIC.
A certain program having a transmission symbol in the MSC at a position apart from the desired program as viewed on the transmission frame other than the desired program is set as a counter program for detection, and the transmission in the MSC corresponding to the counter program for detection is performed. previously obtained the symbol position h ₁ ~h _j.
Here, k _{1 to} k _i are n = 8 to 10, and h ₁ to h _j are n
= 15-17.

Since the desired program exists first on the transmission frame, the effective symbol period signal falls (k _1-2 ) times after the synchronization detection signal SD (t _{5 in} FIG. 4).
Reference), referring to the FIC, outputs the designation information of the sub-channel corresponding to the desired program and the output ON command of the DAB audio frame data related to the sub-channel of the desired program to the channel decoder 6B, and reconstructs from the MSC 4 The sub-channels of the desired program are separated from the two CIFs, time deinterleaving, error detection / correction, error counting, and descrambling are performed to decode the DAB audio frame data corresponding to the desired program, and output to the audio decoder 9. The audio decoder 9 decodes the DAB audio frame data,
Output audio data for the channel. this is,
D / A conversion is performed by the D / A converter 10, and the power amplifier 11,
After the power is amplified at 12, the sound is output from the speakers 13 and 14.

Then, while the antenna selector 3 was previously switched to the side of the antenna 1 for which the reception state was determined to be the best, the reception field strength signal was inputted and stored as the reception field strength Ea (for example, FIG. see the timing of t _6),
Then, enter the error count value M in the error detection / correction of subchannels according to the desired program is output from the channel decoder 6B, stored as Ma (see t ₇ in FIG. 4).

Next, after the synchronization detection signal SD, the system controller 7B changes the effective symbol period signal ES to (h
₁ -2) once fallen in the timing (see t ₈ of the detecting off-screen program begins first valid symbol in MSC corresponding to the immediately preceding guard interval in the interval. 4), the antenna selector 3 previous reception state Is switched to the side (b position) of the antenna 2 opposite to the antenna determined to be the best, and by referring to the FIC, the designation information of the sub-channel corresponding to the counter-program for detection and the DAB related to the sub-channel of the counter-program for detection Outputs an audio frame output off command to the channel decoder 6B, separates the sub-channel of the back program for detection specified this time from the four CIFs of the MSC, and performs time deinterleaving, error detection / correction, error counting, and descrambling. , Output an error count value related to the sub-channel of the counter program for detection (at this time, the channel The decoder 6B turns off the output based on the output off command, and does not output the DAB audio frame data corresponding to the counter program for detection to the audio decoder 9). Then, while the antenna selector 3 is switched to the antenna 2, the received electric field intensity signal is input and stored as the received electric field intensity Eb (for example, t _{9 in} FIG. 4).
Timing).

After the synchronization detection signal SD, the system controller 7B changes the effective symbol period signal ES to (h _j −
In fallen timing 2) times (see t ₁₀ of the detection counterprogram finished last valid symbol in MSC corresponding to after the guard interval within the interval. 4), the antenna selector 3, once the previous, The receiving state is returned to the side (a position) of the antenna 1 determined to be the best. Then, first, the magnitude relationship between the reception electric field strengths Ea and Eb is checked, and it is determined whether Ea> Eb + e (e is a certain positive fixed value). If YES, it is determined that the previous reception state was determined to be the best. Assuming that the reception state of the same antenna 1 is good this time, the antenna selector 3 is kept at the side (position a) of the antenna 1 for which the reception state was previously determined to be the best. On the other hand, if Eb> Ea + e, it is determined that the receiving state of the antenna 2 opposite to the one for which the previous receiving state was determined to be the best is better, and the next time the effective symbol period signal ES falls (the next In the guard interval section of FIG.
Reference t _11), is as the previous reception condition of the antenna selector 3 determines the best by switching to the opposite side (b position), maintain good reception.

If Ea> Eb + e and not Eb> E
When not a a + e is then stored as Mb enter the error count value M in the error detection / correction of subchannels according to the detection counterprogram output from the channel decoder 6B (t ₁₂ see FIG. 4 ), The magnitude relationship between the error count values Ma and Mb is checked, and if Ma <Mb, the antenna 1 which is the same as the antenna 1 whose reception state was previously determined to be the best is determined to have the better reception state this time, and the antenna selector 3 is maintained at the side (a position) of the antenna 1 for which the reception state was previously determined to be the best, and conversely, Mb <M
If it is a, it is determined that the receiving state of the antenna 2 opposite to the one for which the receiving state was determined to be the last time is better, and at the next timing when the effective symbol period signal ES falls (in the next guard interval section) . see t ₁₃ in FIG. 4),
By switching the antenna selector 3 to the opposite side (b position) from the last time that the reception state was determined to be the best, a good reception state is maintained.

As described above, according to the above-described embodiment, the effective symbol of the phase reference symbol or the FI
It is possible to prevent a section required for reception in a transmission frame, such as an effective symbol of C or an effective symbol in an MSC relating to a desired program, from being received by an antenna having a poor reception condition as much as possible, and to prevent antenna switching in the section. In addition, it is possible to avoid the deterioration of the reception characteristics due to the detection of the reception state of the antenna and the switching of the antenna, and it is possible to always keep the best reception state by making the most of the antenna diversity.

[0041] As a modification of the embodiment of the embodiment described above, the last, the switching from the antenna which is the best to another antenna, instead of at the timing t ₈ in FIG. 4,
In the transmission symbol relating to the unnecessary program between the desired program and the counter program for detection in the MSC of the transmission frame (n = 11 to 11 in FIG. 4)
14 (which may be either a guard interval section or an effective symbol section). Also,
As a result of comparing the reception states of the antennas, the timing of switching from the antenna which was determined to be the best the previous time to another antenna is not changed at the timing of t ₁₁ (t ₁₃ ) in FIG. It is performed during a transmission symbol after t ₁₁ (t ₁₃ ) (either a guard interval period or an effective symbol period), or performed during a NULL symbol period of a first synchronization signal of a next transmission frame, Further, in the next transmission frame, it is performed in the guard interval section in the phase reference symbol or FIC, or in the MSC of the next transmission frame until the first effective symbol of the desired program starts. (Either the guard interval section or the effective symbol section may be used).

The detection and comparison of the reception state of the antenna may be performed based only on the received electric field strength, or may be performed based only on the error count value. In the case of performing only the reception electric field intensity, the detection of the reception electric field intensity can be performed in a relatively short time. Therefore, when the reception electric field intensity of the antenna other than the antenna determined to be the best is detected last time, for example, the detection of the desired program is performed. During any one effective symbol period in the MSC except for the effective symbol period in the MSC, switching from the previously determined best antenna to another antenna, detection of the reception electric field strength at the other antenna, The comparison with the reception electric field strength of the antenna determined to be the best, and the switching of the antenna to the best side based on the result of the comparison may all be performed. Further, in one or a plurality of consecutive transmission symbol sections in the MSC other than the transmission symbol related to the desired program in the MSC, switching from the antenna determined to be the best last time to another antenna is performed. Of the received electric field strength of the antenna which was previously determined to be the best, detection of the received electric field strength of the antenna which was previously determined to be the best, comparison with the received electric field strength of the antenna previously determined to be the best, and switching the antenna to the best side based on the comparison result All of the above may be performed.

Although the above embodiments and modifications have been described with reference to DAB broadcasting carried out in Europe, the present invention is not limited to this, and digital terrestrial TV broadcasting is not limited to this. The present invention can be similarly applied to broadcasting, communication, and the like for other uses such as digital satellite broadcasting.

[0044]

According to the present invention, a section necessary for reception in a transmission frame, such as an effective symbol relating to a desired program, is prevented from being received by an antenna having a poor reception state as much as possible.
Alternatively, it is possible not to switch the antenna in the section,
Deterioration of the reception characteristics due to detection of the reception state of the antenna or switching of the antenna can be avoided, and the optimum reception state can be always maintained by making the most of the antenna diversity.

[Brief description of the drawings]

FIG. 1 is a block diagram of an antenna diversity DAB receiver according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the operation of FIG.

FIG. 3 is a block diagram of an antenna diversity DAB receiver according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the operation of FIG. 3;

FIG. 5 is an explanatory diagram showing a format of a DAB transmission frame signal.

FIG. 6 is a block diagram of a conventional antenna diversity DAB receiver.

[Explanation of symbols]

1, 2 Antenna 3 Antenna Selector 4 Front End 5 Demodulator 6, 6B Channel Decoder 7A, 7B System Controller 8 Key Operation Unit 9 Audio Decoder 10 D / A Converter 11, 12 Power Amplifier 13, 14 Speaker 15 Received Electric Field Strength Detection circuit

Claims (3)

[Claims] 1. A receiver capable of antenna diversity by switching antennas and receiving an OFDM modulated wave whose transmission symbol is composed of a guard interval and an effective symbol does not require antenna switching for reception among OFDM modulated waves. The antenna diversity method of the receiver, characterized in that the method is performed in a specific section. 2. It is possible to detect and compare a reception state while switching a plurality of antennas, to perform antenna diversity for receiving by switching to the best antenna, and to realize O diversity in which a transmission symbol is composed of a guard interval and an effective symbol.
A receiver for receiving an FDM modulated wave, wherein the detection of the reception state of the antenna other than the previously determined best is performed in an unnecessary section of the OFDM modulated wave. Antenna diversity method. 3. A method for detecting and comparing the reception state of each antenna while switching a plurality of antennas, enabling antenna diversity for receiving by switching to the best antenna, and a transmission symbol comprising a guard interval and an effective symbol. In a receiver that receives the OFDM modulated wave, the antenna switching and the detection of the reception state of the antenna other than the previously determined best are performed in the section of the OFDM modulated wave that is unnecessary for reception, An antenna diversity method for a receiver.