JP2007142713A - Radio receiver and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio receiver capable of receiving a hybrid broadcast carrier of the IBOC system in a way of being not susceptive to crosstalk and reception disturbance. <P>SOLUTION: The radio receiver (1) including; filters (44, 45) for filtering the hybrid broadcast carrier and outputting the filtered carrier to a demodulation means; a C/N ratio detection section (47) for detecting a first C/N ratio corresponding to a first digital broadcast carrier and detecting a second C/N ratio corresponding to a second digital broadcast carrier; and a control section (60) for controlling the characteristic of the filters in response to the first and second C/N ratios and a receiving method of the radio receiver above are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio receiver and a reception method, and more particularly to an HD (High Definition) radio receiver compatible with an IBOC (In Band on Channel) type hybrid broadcast carrier and a reception method in such a radio receiver. .

  When the IBOC hybrid broadcast carrier is adopted, the digital broadcast carrier can be added to the analog broadcast carrier. Therefore, the HD radio corresponding to the digital broadcast carrier can improve the sound quality by using the digital broadcast carrier. Become. Note that the digital broadcast carrier in such an IBOC hybrid broadcast carrier is disposed on both sides adjacent to the analog broadcast carrier in the frequency band (see, for example, Patent Document 1).

  However, since all broadcast stations do not always broadcast IBOC hybrid broadcast carriers simultaneously, IBOC hybrid broadcast carriers and analog broadcast carriers may be mixed. Since the frequency band of the IBOC hybrid broadcast carrier is wider than the frequency band of the analog broadcast carrier, using a filter that covers the frequency band of the IBOC hybrid broadcast carrier causes interference when there is a strong broadcast wave in the adjacent channel. And noise may occur due to reception interference.

  FIG. 7 is a diagram for explaining the occurrence of interference / reception interference of an IBOC hybrid broadcast carrier wave.

  701 to 705 shown in FIG. 7 are assigned frequencies arranged every 200 kHz in FM broadcasting. Here, a case is shown in which an IBOC FM hybrid broadcast carrier wave 710 whose center frequency is an assigned frequency of 703 and an FM analog broadcast carrier wave 720 whose center frequency is an assigned frequency of 704 are arranged in adjacent channels. Yes. Since the frequency bandwidth of the IBOC FM hybrid broadcast carrier 710 is about 400 kHz, using a wideband filter 730 for digital reception that covers all of the frequency band overlaps with a part of the FM analog broadcast carrier 720, Noise is generated due to reception interference.

Japanese Patent Laid-Open No. 2000-4174 (FIG. 5, page 3)

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radio receiver that can receive an IBOC hybrid broadcast carrier wave without interference or reception interference.

  In order to achieve the above object, a radio receiver according to the present invention includes a filter for filtering a hybrid broadcast carrier wave and outputting it to a demodulation means, a first C / N ratio value corresponding to the first digital broadcast carrier wave, and a first C / N ratio value. A C / N ratio value detection unit that detects a second C / N ratio value corresponding to two digital broadcast carriers, and a control unit that controls filter characteristics according to the first and second C / N ratio values. Features.

  Furthermore, in the radio receiver according to the present invention, the filter includes a first filter corresponding to the first digital broadcast carrier and a second filter corresponding to the second digital broadcast carrier, and the control unit includes the first and second filters. It is preferable that the pass characteristic and the non-pass characteristic of the first and second digital broadcast carriers are controlled using.

  Furthermore, in the radio receiver according to the present invention, the C / N ratio detection unit further detects and controls a third C / N ratio value corresponding to the analog broadcast carrier when filtering corresponding to the analog broadcast carrier is performed. The unit preferably controls the characteristics of the filter according to the first, second, and third C / N ratio values. The configuration is such that optimum filter characteristics are controlled according to three C / N ratio values corresponding to three broadcast carriers.

  Furthermore, the radio receiver according to the present invention further includes a wideband filter provided in the first IF signal path and a narrowband filter provided in the second IF signal path, and the first filter has passed through the wideband filter. Preferably, the first digital broadcast carrier is filtered, the second filter filters the second digital broadcast carrier passed through the wideband filter, and the third filter filters the analog broadcast carrier passed through the narrowband filter. Three filters were constructed corresponding to the profile of the IBOC hybrid broadcast carrier wave.

  Furthermore, in the radio receiver according to the present invention, the control unit preferably performs switching control between the first IF signal path and the second IF signal path in accordance with the first, second, or third C / N ratio value. Two IF signal paths are provided.

  Furthermore, in the radio receiver according to the present invention, an RF amplifier circuit that amplifies an RF signal corresponding to the input hybrid broadcast carrier wave, converts the RF signal into an IF signal, and supplies the IF signal path to the first IF signal path and the second IF signal path A frequency conversion circuit that detects a signal level in the first IF signal path, a first signal level detector that outputs a first AGC signal for feeding back to the RF amplifier circuit, and a signal level in the second IF signal path And a second signal level detection unit that outputs a second AGC signal for applying feedback to the RF amplifier circuit, and the control unit detects the first AGC signal in response to switching between the first IF signal path and the second IF signal path. It is preferable to perform switching control between the AGC signal and the second AGC signal. The AGC signal is switched according to the switching of the two signal paths.

  Furthermore, the radio receiver according to the present invention further includes an RF signal level detection unit that detects an RF signal level of the RF signal, and the control unit includes the RF signal level, the first, second, and third C / N ratio values. It is preferable to control the filter characteristics according to the above. In addition to the three C / N ratio values, the signal intensity depending on the signal level is taken into account, and the configuration can be controlled to the optimum filter characteristics.

  Furthermore, the radio receiver according to the present invention further includes an RF signal level detection unit that detects an RF signal level of the RF signal, and the control unit sets the RF signal level, the first, second, and third C / N ratio values. Accordingly, it is preferable to perform switching control between the first IF signal path and the second IF signal path. In addition to the C / N ratio values corresponding to the three filters, the signal intensity depending on the signal level is also taken into account, so that the optimum IF signal path can be switched.

  Furthermore, the radio receiver according to the present invention further includes an adjacent channel RF signal level detection unit that detects an adjacent channel RF signal level of an adjacent channel RF signal, and the control unit includes an adjacent channel RF signal level, It is preferable to control the filter characteristics according to the first, second and third C / N ratio values. In consideration of the signal intensity of the adjacent channel, the filter characteristics can be controlled to be optimum.

  In order to achieve the above object, a receiving method according to the present invention detects a first C / N ratio value corresponding to a first digital broadcast carrier when filtering corresponding to the first digital broadcast carrier is performed, The second C / N ratio value corresponding to the second digital broadcast carrier when filtering corresponding to the digital broadcast carrier is detected, and the hybrid broadcast carrier is filtered and demodulated according to the first and second C / N ratio values And a step of controlling a characteristic of the filter for outputting to the means.

  To achieve the above object, a radio receiver according to the present invention includes a digital wave filter corresponding to a digital broadcast carrier, an analog wave filter corresponding to an analog broadcast carrier, and a digital broadcast that has passed through the digital wave filter. A digital wave C / N ratio value corresponding to the carrier wave and a C / N ratio value detection unit for detecting the analog wave C / N ratio value corresponding to the analog broadcast carrier wave that has passed through the analog wave filter; It has a control part which performs switching control of a digital wave filter and an analog wave filter according to / N ratio value and analog wave C / N ratio value.

  Further, in the radio receiver according to the present invention, the digital wave filter is provided in the digital wave IF signal path, the analog wave filter is provided in the analog wave IF signal path, and the control unit is a digital wave C signal. It is preferable to perform switching control between the digital wave IF signal path and the analog wave IF signal path in accordance with the / N ratio value and the analog wave C / N ratio value. Two IF signal paths are provided.

  Furthermore, in the radio receiver according to the present invention, an RF amplifier circuit for amplifying an RF signal corresponding to the input hybrid broadcast carrier wave, an RF signal converted into an IF signal, an IF signal path for digital waves, and an IF for analog waves A frequency conversion circuit to be supplied to the signal path, a digital wave signal level detection unit for detecting a signal level in the digital wave IF signal path and outputting a digital AGC signal for applying feedback to the RF amplifier circuit, and an analog An analog wave signal level detection unit for detecting an analog wave AGC signal for detecting a signal level in the wave IF signal path and feeding back to the RF amplifier circuit, and the control unit is a digital wave IF signal The digital wave AGC signal and the analog wave AGC signal are switched according to the switching between the path and the analog wave IF signal path. It is preferable to perform the switching control between. The AGC signal is switched according to the switching of the two signal paths.

  Furthermore, the radio receiver according to the present invention further includes an RF signal level detection unit for detecting the RF signal level of the RF signal, and the control unit has the RF signal level, the digital wave C / N ratio value, and the analog wave C. It is preferable to perform switching control between the digital wave filter and the analog wave filter in accordance with the / N ratio value. In addition to the C / N ratio value corresponding to the two filters, the signal intensity depending on the signal level is taken into account, and the filter is switched to the optimum filter.

  Furthermore, the radio receiver according to the present invention further includes an RF signal level detection unit for detecting the RF signal level of the RF signal, and the control unit has the RF signal level, the digital wave C / N ratio value, and the analog wave C. It is preferable to perform switching control between the digital wave IF signal path and the analog wave IF signal path in accordance with the / N ratio value. In addition to the C / N ratio values corresponding to the two filters, the signal intensity depending on the signal level is also taken into account, and the optimum IF signal path can be switched.

  Furthermore, the radio receiver according to the present invention further includes an adjacent channel RF signal level detection unit for detecting an adjacent channel RF signal level of an adjacent channel RF signal, and the control unit is configured to detect the RF signal level and the digital wave C signal. It is preferable to perform switching control between the digital wave filter and the analog wave filter in accordance with the / N ratio value and the analog wave C / N ratio value. In consideration of the signal strength of the adjacent channel, the filter can be switched to the optimum filter.

  Furthermore, in the radio receiver according to the present invention, the control unit preferably performs switching control between the digital wave IF signal path and the analog wave IF signal path with hysteresis setting. For example, a configuration is adopted in which hysteresis is set such that the reception time of a digital broadcast carrier wave is further increased while preventing sound interruption due to switching.

  According to the radio receiver of the present invention, the filter characteristics can be controlled so as to avoid a strong broadcast wave that has an influence on the IBOC hybrid broadcast carrier wave. In addition, an IBOC hybrid broadcast carrier wave can be received.

  A radio receiver according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an outline of an example of a radio receiver (for FM broadcasting) according to the present invention.

  The radio receiver 1 includes a tuner unit 20, a narrowband analog wave filter 30, an IF (Intermediate Frequency) signal processing unit 40, an IBOC processing unit 50, a control unit 60 including a CPU, a memory 70, an operation unit 72, The AM demodulator 80, the FM demodulator 82, the switching unit 84, the D / A converter 86, and the like are connected to the antenna 10 and the speaker 90.

  The tuner unit 20 includes an electronic tuning type tuning circuit 21 that receives an RF signal from the antenna 10, a mixing circuit 22, a PLL circuit 23, and a digital reception wideband filter (hereinafter referred to as “W filter”) 24 having a bandwidth of about 400 kHz. The amplifier circuit 25 and the like are controlled by the control unit 60. The RF reception signal received by the tuning circuit 21 is mixed with the local oscillation signal from the PLL circuit 23 by the mixing circuit 22, converted into an intermediate frequency (IF) signal, and input to the W filter 24. The intermediate frequency signal that has passed through the W filter 24 is gain-adjusted by the amplifier circuit 25 and input to the narrowband analog wave filter (hereinafter referred to as “N filter”) 30 and the IF signal processing circuit 40. The gain adjustment in the amplifier circuit 25 is performed by the first AGC signal from the first AGC circuit 41 in the subsequent stage or the second AGC signal from the second AGC circuit 42. The tuning circuit 21 outputs an S level signal indicating the received signal strength.

  The IF signal processing unit 30 includes a first AGC circuit 41 based on the intermediate frequency that has passed through the W filter 24, a second AGC circuit 42 that is based on the intermediate frequency that has passed through the N filter 30, and a first AGC signal and a second AGC circuit from the first AGC circuit 41. A first switching circuit 43 that switches between the second AGC signal from 42, a downstream filter (hereinafter referred to as “L filter”) 44 having a bandwidth of about 70 kHz, and an upstream filter (hereinafter referred to as “H filter”) having a bandwidth of about 70 kHz. ) 45, a central filter (hereinafter referred to as “M filter”) 46 having a bandwidth of about 180 kHz, a C / N value comparison circuit 47, a second for switching between the digital wave IF signal path 100 and the analog wave IF signal path 110. A switching circuit 48, a digital filter 49 for outputting an IBOC-AM signal, and a switch for switching between IBOC-AM and IBOC-FM. Includes a switching circuit 50, etc., it is controlled by the control unit 60.

  The IBOC decoder 52 has a function of demodulating an OFDM (orthogonal frequency division modulation) subcarrier included in the digital broadcast carrier of the IBOC-FM or IBOC-AM carrier, and is controlled by the control unit 60. If the demodulated signal is an audio signal, the IBOC decoder 52 generates an audio signal and outputs it to the switching unit 84. When the demodulated signal includes SIS data (text data or video data), text data or video data is generated by a dedicated decoder (not shown) and stored in the memory 70. The stored text data and video data are displayed on a display unit (not shown) at a predetermined timing. When text data or video data is generated, it can be determined that the currently demodulated broadcast wave is a digital broadcast carrier wave.

  The AM demodulator 80 and the FM demodulator 82 demodulate the analog AM signal and the analog FM signal from the IBOC-FM signal, respectively, and output them to the switching unit 84. Therefore, the switching unit 84 receives the digital FM or digital AM signal output from the IBOC decoder 52 and the analog AM signal and analog FM signal output from the AM demodulation unit 80 and the FM demodulation unit 82. Become. The control unit 60 controls the switching unit 84 to output a desired signal to the speaker 90 via the D / A conversion circuit 86.

  The operation unit 72 includes various buttons and knobs for tuning, volume setting, and seek operation start instruction.

  In FIG. 1, the W filter 24 is provided. However, instead of the W filter 24, an all-band pass filter (for example, a non-attenuating conductor line) may be provided as a broadband filter. This is because desired filtering can be substantially performed by the L filter 44, the H filter 45, and the M filter 46 in the subsequent stage.

  FIG. 2 is a diagram showing a profile of an IBOC hybrid broadcast carrier wave. FIG. 2A shows an example of an FM wave, and FIG. 2B shows an example of an AM wave.

  As shown in FIG. 2A, the digital broadcast carrier 202 on the downstream side (lower frequency side) and the upstream side are adjacent to the upper band and the lower band on the frequency band of the analog broadcast carrier wave (FM analog signal) 201. A digital broadcast carrier 203 (on the higher frequency side) is arranged. The digital broadcast carriers 202 and 203 are composed of, for example, a plurality of OFDM-modulated subcarriers, and occupy a spectrum separated by 130 kHz to 199 kHz and −130 kHz to −199 kHz from the center frequency of the FM analog signal as shown in the figure. ing. Further, the peak values of the digital broadcast carriers 202 and 203 are set to −25 dB / kHz with respect to the peak value of the FM analog signal. The digital broadcast carriers 202 and 203 contain the same data.

  FIG. 2A also shows an arrangement example of an IBOC hybrid broadcast carrier wave, an L filter, an H filter, and an M filter. The M filter (MF) is arranged such that the center frequency (assigned frequency) of the IBOC hybrid broadcast carrier wave is the center frequency, and the bandwidth is set to about 180 kHz. The L filter (LF) is arranged such that a frequency lower by 165 kHz than the center frequency (allocated frequency) of the IBOC hybrid broadcast carrier wave is the center frequency, and the bandwidth is about 70 kHz. The H filter (HF) is arranged such that a frequency higher by 165 kHz than the center frequency (allocated frequency) of the IBOC hybrid broadcast carrier wave is the center frequency, and the bandwidth is about 70 kHz.

  As described above, the M filter (MF) corresponds to the analog broadcast carrier 201 of the IBOC hybrid broadcast carrier, the L filter (LF) corresponds to the downstream digital broadcast carrier 202 of the IBOC hybrid broadcast carrier, and the H filter. (HF) corresponds to the digital broadcast carrier 203 on the upstream side of the IBOC hybrid broadcast carrier.

  As shown in FIG. 2B, the first digital broadcast carrier 212 on the downstream side (lower frequency side) is adjacent to the upper band and the lower band on the frequency band of the analog broadcast carrier wave (AM analog signal) 211, respectively. The first digital carrier wave 213 on the upstream side (high frequency side) is arranged. The digital broadcast carriers 212 and 213 are composed of, for example, a plurality of OFDM-modulated subcarriers, and occupy a spectrum 5 to 15 kHz and −15 kHz to −15 kHz away from the center frequency of the AM analog signal, as shown in the figure. ing. Further, the peak values of the IBOC digital broadcast carriers 212 and 213 are set to −25 dB / kHz with respect to the peak value of the AM analog signal. Furthermore, a downstream second digital broadcast carrier 214 and an upstream second digital carrier 215 are disposed between the analog broadcast carrier 211 and the first digital broadcast carriers 212 and 213, respectively. In addition, the first digital broadcast carriers 212 and 213 include data having the same contents, and the second digital broadcast carriers 214 and 215 also include data having the same contents.

  FIG. 3 is a diagram illustrating an example of a control flow of the filter characteristics according to the present invention.

  The flow shown in FIG. 3 is mainly executed by the control unit 60 jointly with each component in accordance with a program stored in advance in the control unit 60 of the radio receiver 1 shown in FIG. Also, assume that the radio receiver 1 is powered on at the time when the flow shown in FIG. 3 is executed, and that each component is maintained in an operable state. Further, the flow shown in FIG. 3 relates to the control flow of the filter characteristics at the time of FM broadcast reception, but can be changed and applied at the time of AM broadcast reception.

  This flow is repeatedly executed at predetermined time intervals (which may be constant or variable) when receiving FM broadcasts (S300). The control unit 60 tunes the tuning circuit 21 to the assigned frequency of the selected broadcast station, and acquires the S level signal from the tuning circuit 21 (S301). The control unit 60 determines the signal strength of the received signal based on the acquired S level signal.

  Next, the control unit 60 obtains the value of the C / N ratio (Carrier to Noise Ratio) of the L filter 44 from the CN comparison circuit 47 (S302), and obtains the value of the C / N ratio of the H filter 45 from the CN comparison circuit. 47 (S303), and the value of the C / N ratio of the M filter 47 is acquired from the CN comparison circuit 47 (S304).

  Next, the control unit 60 determines an optimal filter based on the data acquired in S301 to 304, and the system of the digital wave IF signal path 100 and the analog wave IF signal path 110 according to the determination of the filter. Switching (S305) and switching of filters to be used (control of filter characteristics) are performed (S306). The filter switching is determined based on conditions as shown in FIG. Switching of the system is performed by the control unit 60 controlling the second switching circuit 48. The route that is input from the W filter 24 to the L filter 44 and the / H filter 45 through the amplifier circuit 25 and the like is the digital wave IF signal path 100, and from the W filter 24 to the amplifier circuit 25 and the N filter 30. The analog wave IF signal path 110 is a route that is input to the M filter 46 through the like.

  Next, the control unit 60 performs switching control of the AGC signal according to the switched IF signal path (S307), and ends the series of controls. That is, when the control unit 60 is switched to the digital wave IF signal path 100, it feeds back to the amplifier circuit 25 using the first AGC signal from the first AGC circuit 41 and switches to the analog wave IF signal path 110. In such a case, control is performed so that feedback is applied to the amplifier circuit 25 using the second AGC signal from the second AGC circuit 42. Since the filter bandwidth differs depending on the IF signal path, the signal level was controlled to be substantially constant regardless of the IF signal path.

  FIG. 4 is a diagram illustrating an example of a filter characteristic control pattern.

  The control unit 60 selects a filter to be switched based on the signal strength, the C / N ratio value of the L filter 44, the C / N ratio value of the H filter 45, and the C / N ratio value of the M filter 46 in FIG. Determine as shown.

  In FIG. 4, the signal intensity becomes “◯” when the S level signal acquired from the tuning circuit 21 is larger than a predetermined threshold value, and the C / N ratio value of each filter becomes “◯”. Is a case where the value of each C / N ratio acquired from the C / N comparison circuit 47 is larger than a predetermined threshold value (for example, 56 dB equivalent). Further, “both” indicates that both the L filter 44 and the H filter 45 are used.

  FIG. 5 is a diagram illustrating the relationship between the reception state and the filter to be used.

  Each figure in FIG. 5 shows a state where a hybrid broadcast carrier having an analog broadcast carrier 201, a downstream digital broadcast carrier 202, and an upstream digital broadcast carrier 203 is arranged at an assigned frequency (center frequency of a desired channel) 521. Yes. In the figure, reference numerals 520 and 522 indicate adjacent allocation frequencies (center frequencies of adjacent channels).

  FIG. 5A shows a case where there is no strong broadcast wave that affects adjacent channels. In this case, the signal intensity, the C / N ratio value of LF44, the C / N ratio value of HF45, and the C / N ratio value of MF46 are as indicated by 401 in FIG. The filters are switched so as to use both of them, and the second switching circuit 48 is controlled so that the digital wave IF signal path 100 is used. In this case, since the information included in the downstream digital broadcast carrier 202 and the upstream digital broadcast carrier 203 is the same, a better audio signal can be reproduced by synthesizing the signals from the LF 44 and the HF 45. It becomes possible.

  FIG. 5B shows a case where there is a strong broadcast wave 500 that affects only the channel 522 adjacent on the upstream side. In this case, the signal intensity, the C / N ratio value of LF44, the C / N ratio value of HF45, and the C / N ratio value of MF46 are as shown in 402 of FIG. Thus, the filter is switched, and the second switching circuit 48 is controlled so that the digital wave IF signal path 100 is used. In this case, since the audio signal is reproduced based only on the downstream digital broadcast carrier wave 202 while avoiding the strong broadcast wave 500 that affects reception, problems such as interference and reception interference can be eliminated.

  FIG. 5C shows a case where there is a strong broadcast wave 510 that affects only the channel 520 adjacent to the downstream side. In this case, the signal strength, the C / N ratio value of LF44, the C / N ratio value of HF45, and the C / N ratio value of MF46 are as shown at 403 in FIG. Thus, the filter is switched, and the second switching circuit 48 is controlled so that the digital wave IF signal path 100 is used. In this case, since the audio signal is reproduced based only on the upstream digital broadcast carrier 203 while avoiding the strong broadcast wave 510 that affects reception, problems such as interference and reception interference can be eliminated.

  FIG. 5D shows a case where there is a strong broadcast wave 510 that affects the adjacent channel 520 on the downstream side and a strong broadcast wave 500 that affects the adjacent channel 522 on the upstream side. In this case, the signal intensity, the C / N ratio value of LF44, the C / N ratio value of HF45, and the C / N ratio value of MF46 are as shown in 404 of FIG. The filter is switched so that the second switching circuit 48 is controlled to use the analog wave IF signal path 110. In this case, sound reproduction based on an analog broadcast carrier wave with inferior sound quality is performed. However, since strong broadcast waves 500 and 510 that affect reception are avoided, problems such as interference and reception interference can be eliminated. It becomes.

  In the above embodiment, the filter switching and the IF signal path switching are performed based on the signal strength, the LF 44 C / N ratio value, the HF 45 C / N ratio value, and the MF 46 C / N ratio value. However, it is also possible to control the switching of the filter and the switching of the IF signal path based on only the C / N ratio value of the LF 44, the C / N ratio value of the HF 45, and the C / N ratio value of the MF 46. Further, the switching of the filter and the switching of the IF signal path can be performed based only on the C / N ratio value of the LF 44 and the C / N ratio value of the HF 45.

  In the above embodiment, based on the signal strength of the RF signal corresponding to the desired channel, the C / N ratio value of the LF 44, the C / N ratio value of the HF 45, and the C / N ratio value of the MF 46, the filter switching and IF The signal path was switched. However, when switching the filter and the IF signal path, the signal strength of the RF signal corresponding to the adjacent channel may be used instead of the signal strength of the RF signal corresponding to the desired channel. For example, in the case of FIG. 5B, which filter is switched to using the signal strength of the RF signal corresponding to the upstream adjacent channel 522 and the signal strength of the RF signal corresponding to the downstream adjacent channel 520. Judgment can be made.

  As described above, according to the radio receiver and the receiving method of the present invention, the filter switching and / or the IF signal path switching is performed so as to avoid a strong broadcast wave that always affects reception. It becomes possible to eliminate such a problem.

  FIG. 6 is a diagram for explaining switching (blending operation) between a digital system and an analog system.

  When the radio receiver 1 according to the present invention is mounted on a vehicle or the like, the reception situation changes as the vehicle moves, and a filter or IF signal path needs to be switched in accordance with the change in the reception situation. To do. Hereinafter, switching (blending operation) between a digital system and an analog system according to a change in reception status will be described.

  FIG. 6A shows the switching timing between the digital system and the analog system based on the signal strength and the C / N ratio value. In FIG. 6A, the H level signal corresponds to the digital system, and the L level signal corresponds to the analog system. FIG. 6B shows an example of an actual audio output blending operation. FIG. 6B shows an audio output signal 602 based on an analog system and an audio output signal 603 based on a digital system.

  FIG. 6 shows a state in which audio output based on the analog system is being performed at time t1 (state in FIG. 5D). That is, in this state, switching to the MF 46 and the analog wave IF signal path 110 is performed, and audio output corresponding to the analog broadcast carrier wave is performed.

  In FIG. 6, at time t2, the reception state has improved (for example, the state shown in FIG. 5C). However, immediately, without switching from the analog system to the digital system, the audio output based on both systems is blended, and control is performed so that the audio output is gradually based on the digital system. For example, in the blend period 620, control is performed such that the audio output of the analog system is decreased by 10% per 30 ms, and conversely, the audio output of the digital system is increased by 10% per 30 ms.

  Therefore, at time t3, the sound output is completely switched to the digital system. That is, in this state, for example, switching to the FH 45 and the digital wave IF signal path 100 is performed, and audio output corresponding to the upstream digital broadcast carrier wave is performed.

  In FIG. 6, at time t4, a state where the reception state deteriorates again is shown (for example, the state of FIG. 5D). However, control is performed so that switching from the analog system to the digital system is not performed immediately, and the switching to the analog system is started after waiting for the hysteresis setting period 610. This is to increase the sound output of the digital system with good sound quality as much as possible while preventing frequent switching of systems and sound interruption. The hysteresis setting period 610 can be set to 300 ms, for example.

  After the hysteresis setting period 610, switching from the time t5 to the analog system is performed. For example, in the blend period 630, control is performed such that the digital system audio output is decreased by 10% per 30 ms, and the analog system audio output is increased by 10% per 30 ms. Therefore, at time t6, the MF 46 and the analog wave IF signal path 110 are switched to output audio corresponding to the analog broadcast carrier wave.

  As shown in FIG. 6, by switching between the digital system and the analog system, it is possible to maintain a good audio output regardless of the change in the reception state accompanying the movement of the vehicle. The blending period and hysteresis setting described above are merely examples, and can be modified according to the situation.

It is a block diagram which shows schematic structure of the radio receiver which concerns on this invention. It is a figure which shows the hybrid broadcast carrier wave of an IBOC system. It is a control flowchart which shows the reception method which concerns on this invention. It is a figure which shows an example of control of a filter characteristic. It is a figure which shows the relationship between a reception state and filter switching. It is a figure for demonstrating blend operation. It is a figure for demonstrating generation | occurrence | production of interference and reception interference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio receiver 10 Antenna 20 Tuner part 40 IF signal processing part 44 L filter 45 H filter 46 M filter 52 IBOC decoder 60 Control part 70 Memory 72 Operation part 90 Speaker 100 Digital signal IF signal path 110 Analog wave IF signal path

Claims (10)

A radio receiver for receiving a hybrid broadcast carrier having a first digital broadcast carrier, a second digital broadcast carrier, and an analog broadcast carrier,
A filter for filtering the hybrid broadcast carrier wave and outputting it to the demodulation means;
A C / N ratio detection unit for detecting a first C / N ratio value corresponding to the first digital broadcast carrier and a second C / N ratio value corresponding to the second digital broadcast carrier;
A control unit for controlling characteristics of the filter in accordance with the first and second C / N ratio values;
A radio receiver comprising: The filter includes a first filter corresponding to the first digital broadcast carrier wave and a second filter corresponding to the second digital broadcast carrier wave,
The radio receiver according to claim 1, wherein the control unit controls pass characteristics and non-pass characteristics of the first and second digital broadcast carriers using the first and second filters. The C / N ratio detection unit further detects a third C / N ratio value corresponding to the analog broadcast carrier when filtering corresponding to the analog broadcast carrier is performed,
The radio receiver according to claim 2, wherein the control unit controls characteristics of the filter according to the first, second, and third C / N ratio values. A broadband filter provided in the first IF signal path;
A narrowband filter provided in the second IF signal path;
The first filter filters the first digital broadcast carrier wave that has passed through the wideband filter;
The second filter filters the second digital broadcast carrier wave that has passed through the broadband filter;
The radio receiver according to claim 3, wherein the third filter filters the analog broadcast carrier that has passed through the narrowband filter.   The radio receiver according to claim 4, wherein the control unit performs switching control between the first IF signal path and the second IF signal path according to the first, second, or third C / N ratio value. An RF amplification circuit for amplifying an RF signal corresponding to the input hybrid broadcast carrier wave;
A frequency conversion circuit that converts an RF signal into an IF signal and supplies the converted signal to the first IF signal path and the second IF signal path;
A first signal level detector for detecting a signal level in the first IF signal path and outputting a first AGC signal for applying feedback to the RF amplifier circuit;
A second signal level detector for detecting a signal level in the second IF signal path and outputting a second AGC signal for applying feedback to the RF amplifier circuit;
The radio receiver according to claim 5, wherein the control unit performs switching control between the first AGC signal and the second AGC signal according to switching between the first IF signal path and the second IF signal path. An RF signal level detector for detecting the RF signal level of the RF signal;
The radio receiver according to claim 1, wherein the control unit controls the filter characteristic according to the RF signal level and the first, second, and third C / N ratio values. An RF signal level detector for detecting the RF signal level of the RF signal;
The said control part performs switching control of the said 1st IF signal path | route and the said 2nd IF signal path | route according to the said RF signal level and the said 1st, 2nd, and 3rd C / N ratio value. Radio receiver. An RF signal level detector for the adjacent channel that detects the RF signal level for the adjacent channel of the RF signal of the adjacent channel;
2. The radio receiver according to claim 1, wherein the control unit controls the filter characteristic according to the RF signal level for the adjacent channel and the first, second, and third C / N ratio values. A receiving method for receiving a hybrid broadcast carrier having a first digital broadcast carrier, a second digital broadcast carrier and an analog broadcast carrier,
Detecting a first C / N ratio value corresponding to the first digital broadcast carrier when filtering corresponding to the first digital broadcast carrier is performed;
Detecting a second C / N ratio value corresponding to the second digital broadcast carrier when filtering corresponding to the second digital broadcast carrier is performed;
According to the first and second C / N ratio values, control the characteristics of a filter for filtering the hybrid broadcast carrier wave and outputting it to a demodulator.
A radio receiver comprising:
A receiving method comprising: steps.

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