JP2009055551A - Radio signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for simultaneously demodulating a plurality of channel signals by one tuner. <P>SOLUTION: The radio signal receiver includes a broadband RF front end 101 and a digital baseband 102. A broadband RF front end 101 includes an amplifier 201, a frequency converter 202 and an A-D converter 203. The digital baseband 102 includes a frequency selecting portion 204 and a demodulating portion 205. The broadband RF front end 101 receives analog signals having a plurality of frequency band signals and converts the analog signals into the digital signals to be outputted. In the digital baseband, the frequency selecting portion 204 selects a predetermined frequency band from the digital signals outputted from the A-D converter 203, and the demodulating portion 205 demodulates signals of the selected frequency band. A predetermined frequency band is one of a plurality of the predetermined frequency bands and switched to be selected by allowing the frequency selecting portion 204 to be multiplexed by time division. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio signal receiver that receives and demodulates a radio signal.

  In recent years, traffic information on vehicles, time required to a predetermined location, accident / malfunction vehicle / construction information, speed regulation / lane regulation information, parking location information, parking / service / parking area full / empty information The road traffic information communication system (VICS) that informs of the situation has spread (hereinafter, information provided by the VICS is referred to as VICS information).

  VICS sends road traffic information collected, processed, and edited by the Road Traffic Information and Communication System Center (VICS Center) via communication / broadcast media and displayed as text and graphics (such as maps) on in-vehicle devices such as car navigation systems. It is a system to let you.

  The VICS information is provided by a technique using radio wave beacon, optical beacon, FM multiplex broadcasting, or the like. These methods have different uses (roles). The radio beacon is mainly installed on a highway, and provides highway information from the installation position to about 200 km ahead of the vehicle located within a range of about 70 m from the installation position of the beacon. Optical beacons are mainly installed on main trunk roads, and provide general road information about 10 to 30 km ahead from the installation position to vehicles in the range of about 3.5 m from the installation position of the beacon. To do. FM multiplex broadcasting uses a frequency band of 76 to 90 MHz (depending on the region), and for vehicles within the range of one prefecture from the installation position of the broadcasting station (compared to radio and optical beacons). (The transmission range is very wide), providing information covering highways and ordinary roads.

  VICS information using FM multiplex broadcasting is provided by being multiplexed with NHK-FM broadcast waves, and VICS information cannot be received when the vehicle (the driver) is listening to a channel other than NHK. There is a problem.

  Such a problem can be solved if two FM radio tuners are installed in the vehicle (in fact, some high-end vehicles have two tuners installed in the vehicle. Apart from existing tuners, some car navigation devices have tuners). However, a vehicle equipped with two tuners is extremely rare, and a car navigation device that is originally attached to the vehicle does not often include a tuner. In addition, it is not preferable to provide two tuners in the vehicle because it increases costs. Therefore, a technique for simultaneously demodulating signals of a plurality of channels without increasing the number of tuners (with one tuner) is desired.

As conventional techniques related to reception / demodulation of such wireless signals, there are Patent Documents 1 to 3.
JP-A-7-79176 JP 11-88220 A JP 2002-198837 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for simultaneously demodulating signals of a plurality of channels with a single tuner.

  In order to achieve the above object, the present invention adopts the following configuration.

  A radio signal receiver according to the present invention is a radio signal receiver including a wideband RF front end unit and a digital baseband unit, and the wideband RF front end unit receives an analog signal including signals in a plurality of frequency bands. The analog base signal is converted into a digital signal for output, and the digital baseband unit selects a predetermined frequency band from the digital signal, and the signal in the selected frequency band. Demodulation means for demodulating the frequency, wherein the frequency selection means switches the frequency band to be selected by performing a multiplexing operation in a time division manner.

  In the radio signal receiver according to the present invention, a plurality of frequency bands (channels) can be demodulated by a single tuner by switching a plurality of frequency bands and selecting and demodulating signals in the respective frequency bands. . Furthermore, by performing the switching in a time-division multiplexed manner, signals of a plurality of channels can be demodulated simultaneously. That is, the user can acquire VICS information even when listening to a channel other than NHK.

  The wideband RF front end unit includes a filter that lowers a level of a signal in a predetermined frequency band in the received analog signal, and an AD converter that converts the analog signal processed by the filter into a digital signal. preferable. Thereby, the signals of all channels can be demodulated regardless of the positional relationship between the receiving station and the broadcasting station.

  For example, when it is desired to receive a signal from a distant broadcast station Y in the vicinity of the broadcast station X, a large level difference occurs between the received signal strengths of the signal transmitted from the broadcast station X and the signal transmitted from the broadcast station Y. When this level difference exceeds the dynamic range of the AD converter, the signal of a distant broadcasting station cannot be detected after AD conversion, and only the signal of a nearby broadcasting station can be demodulated (by using an AD converter with a wide dynamic range). This problem is solved, but the apparatus becomes large and the cost increases.) Therefore, by reducing the level of the signal that causes the dynamic range to be exceeded and reducing the level difference between the channels, it is possible to demodulate the signals of all the channels without increasing the cost.

  The wideband RF front end unit further includes a converter that converts the frequency of the received analog signal, and the converter has a frequency band of a signal showing the strongest level in the analog signal that matches the frequency band of the filter. So that the frequency of the analog signal is converted, the filter performs a filtering process on the converted analog signal, and the frequency selection means selects according to the amount of frequency conversion by the converter Preferably, the frequency band to be shifted is shifted to the low frequency side or the high frequency side. In the received analog signal, if the level difference between the strongest signal and the weakest signal is within the dynamic range, the problem of exceeding the dynamic range is solved. Therefore, the frequency band of the strongest level signal is matched with the frequency band of the filter. As a result, the level of the signal that causes the dynamic range to be exceeded can be lowered, so that the signals of all channels can be demodulated.

  The broadband RF front end unit preferably further includes a plurality of filters having different frequency bands to be reduced, and a filter selection unit that selects a filter to be used for filter processing from the plurality of filters. Thereby, even when a broadcasting station in the vicinity of the receiving station transmits signals in a plurality of frequency bands (for example, Tokyo Tower transmits signals in six frequency bands out of a frequency band of 76 to 90 MHz. By reducing the signals of these multiple frequency bands, the signals of all channels can be demodulated.

  The radio signal receiver according to the present invention can simultaneously demodulate signals of a plurality of channels with one tuner.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

<Device configuration>
FIG. 1 is a block diagram showing a functional configuration of a radio signal receiver according to an embodiment of the present invention. This radio signal receiver is a device that receives and demodulates a radio signal, and can simultaneously demodulate signals of a plurality of frequency bands (channels) with one tuner. In the present embodiment, as an example, a case will be described in which a radio signal in the frequency band of FM radio broadcasting (76 to 90 MHz in Japan) is received.

  The wireless signal receiver includes a broadband RF front end unit 101 and a digital baseband unit 102 (see FIG. 1). Each function and configuration will be described below.

<Broadband RF front end>
The broadband RF front end unit 101 has a function of receiving an analog signal including signals of a plurality of channels, converting the analog signal into a digital signal, and outputting the digital signal. In the present embodiment, the broadband RF front end unit 101 includes the amplifier 201, the frequency converter 202, and the AD converter 203 shown in FIG.

  The amplifier 201 has a function of amplifying the received analog signal. As the amplifier 201, an existing technology such as a high frequency amplifier may be applied.

  The frequency converter 202 has a function of converting the frequency of the analog signal amplified by the amplifier 201 to a lower frequency. The frequency converter 202 is configured by combining a local oscillator 301 and a mixer 302, for example. The analog signal is shifted to the low frequency side by the local frequency of the local oscillator 301.

  The AD converter 203 has a function of converting the analog signal converted by the frequency converter 202 into a digital signal. An existing AD converter may be applied as the AD converter.

<Digital baseband part>
The digital baseband unit 102 has a function of simultaneously demodulating signals of a plurality of channels from a digital signal output from the broadband RF front end unit 101 (specifically, the AD converter 203). The digital baseband unit 102 includes a frequency selection unit 204 and a demodulation unit 205 shown in FIG. Note that the processing in the digital baseband unit 102 is digital processing, and for example, most of the processing can be realized by software.

  The frequency selection unit 204 has a function of selecting a predetermined channel from the digital signal output from the broadband RF front end unit 101. The predetermined channel is any one of a plurality of predetermined channels, and the frequency selection unit 204 switches the channel to be selected by performing a multiplexing operation in a time division manner. The predetermined plurality of channels are, for example, channels of signals transmitted from broadcasting stations in the area.

  The frequency selection processing in the frequency selection unit 204 corresponds to an existing filter circuit such as a band pass filter (BPF) in an analog manner. FIG. 2 is an analog representation of the switching process of the frequency selection unit 204. As shown in FIG. 2, the switching process is performed by switching on / off the switches 406 to 410 connected to the bandpass filters 401 to 405 in a time division manner. The band-pass filters 401 to 405 correspond to different channels, respectively, and in the example of FIG. 2, correspond to the channels CH1 to CH5 of signals transmitted in the area.

  The demodulator 205 has a function of demodulating the signal of the channel selected by the frequency selector 204.

<Radio signal reception / demodulation function>
The function and processing flow of the radio signal receiver will be described below. In the present embodiment, the case where the vehicle is equipped with only the radio signal receiver according to the present invention as a radio signal receiver, and receives an analog signal A1 including FM radio channels CH1 to CH5 and a VICS signal will be described. To do. However, the frequency band of VICS is assumed to be equal to channel CH3. The signals of channels CH1 to CH5 included in analog signal A1 are signals SA1 to SA5, respectively. The VICS signal is included in the signal SA3 of channel CH3.

  When the user turns on the radio signal receiver, the amplifier 201 amplifies the analog signal received, and the frequency converter 202 shifts the frequency of the amplified analog signal to the low frequency side. Then, the AD converter 203 converts the analog signal shifted to the low frequency side into a digital signal. As described above, the analog signal A1 is received in this embodiment. The analog signal A1 is amplified and converted to a low frequency, and then converted to a digital signal D1. The signals of channels CH1 to CH5 included in the digital signal D1 are signals SD1 to SD5, respectively.

  Next, the frequency selection unit 204 selects a predetermined channel from the digital signal output from the AD converter 203. In the present embodiment, any one of the channels CH1 to CH5 is selected.

  Then, the demodulator 205 demodulates the signal of the selected channel.

  While the wireless signal receiver is turned on, the frequency selection unit 204 continues to switch the channel to be selected (channels CH1 to CH5). Since the switching process is performed in a time division manner, the user can feel that the signals of the channels CH1 to CH5 are demodulated simultaneously.

  As described above, in this embodiment, by switching the channels selected by the frequency selection unit 204 in a time division manner, signals from a plurality of channels can be demodulated simultaneously by one tuner. This makes it possible to receive VICS information regardless of which channel the user is listening to.

<Modification 1>
Next, a case where the vehicle is located near a certain broadcasting station will be described.

When the distance between the vehicle (receiving station) and the plurality of broadcasting stations is greatly different, a large difference in received signal strength (level) occurs. In the example of FIG. 3, the distance between the vehicle 501 and the broadcast station 502 is very close (distance L1), and the distance between the vehicle 501 and the broadcast station 503 and the broadcast station 504 (distance L2 and distance L3) is the distance L1. Very large compared. Since the level is inversely proportional to the square of the distance, if the distance between the vehicle and multiple broadcast stations is some distance away, even if there is a slight difference in the distance between the vehicle and each broadcast station, the level of the received signal Although there is no great difference, in the vicinity of the broadcasting station, only a slight difference in the distance between the vehicle and each broadcasting station causes a large difference in the level of the received signal.

  As a result, as shown in FIG. 4A, the level of the signal A502 transmitted from the broadcast station 502 in the analog signal A2 received by the vehicle 501 is very strong, and is transmitted from the broadcast station 503 and the broadcast station 504. The levels of the signal A503 and the signal A504 are very weak compared to the signal A502. When the level difference D1 between the signal A502 indicating the strongest level and the signal A504 indicating the second strongest level exceeds the dynamic range of the AD converter 203, only the signal from the broadcast station 502 can be detected after AD conversion. . This problem can be solved by using an AD converter with a wide dynamic range as the AD converter 203, but the apparatus becomes large and the cost increases.

  In the first modification, a configuration in which the broadband RF front end unit 101 further includes a filter 601 as illustrated in the block diagram of FIG. The same functions as those shown in the block diagram of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The filter 601 has a function of reducing the level of a predetermined channel signal in the received analog signal. As the filter 601, an existing filter circuit such as a notch filter may be applied. Specifically, the filter 601 reduces the level of a signal in a frequency band (about 100 kHz) for one channel around a predetermined frequency. The predetermined frequency (blocking frequency) may be set in any way.

  If the frequency band of the filter 601 matches the channel of the signal A502 (FIG. 4 (a)), the level of the signal A502 can be lowered, and the analog signal A2 is converted to the analog signal A3 shown in FIG. 4 (b). Can be converted as follows. Thereby, since all the received signals can be stored within the dynamic range, all the signals can be demodulated without increasing the cost.

  The function and processing flow of the radio signal receiver according to the first modification will be described below. In the first modification as well, the case where the vehicle receives the analog signal A1 of the channels CH1 to CH5 of the FM radio will be described as in the above description.

  When the user turns on the radio signal receiver, the amplifier 201 amplifies the analog signal received, and the frequency converter 202 shifts the frequency of the amplified analog signal to the low frequency side. However, in this embodiment, the local frequency of the local oscillator 301 in the initial state is 70 MHz. That is, the analog signal A1 of 76 to 90 MHz is converted into an analog signal of 6 to 20 MHz ((76-70) to (90-70) MHz) by the frequency converter 202.

  Next, the filter 601 reduces the level of the signal of a predetermined channel in the analog signal subjected to frequency conversion. In the present embodiment, the blocking frequency is 21 MHz. Therefore, the level is not lowered at this stage.

  Then, the AD converter 203 converts the analog signal after the filter processing into a digital signal.

  Next, the frequency selection unit 204 selects a predetermined channel from the digital signal output from the AD converter 203, and the demodulation unit 205 demodulates the signal of the selected channel.

  Then, while the radio signal receiver is turned on, the frequency selection unit 204 continues to switch the channel to be selected (channels CH1 to CH5) in a time division manner.

  At this time, if there is a channel without a signal, it means that the level difference between signals exceeds the dynamic range of the AD converter 203. In that case, the channel of the signal showing the strongest level among all channels is matched with the frequency band of the filter 601. Specifically, by changing the local frequency of the local oscillator 301, the frequency of the signal showing the strongest level is matched with the blocking frequency of the filter 601. At the same time as changing the local frequency, the frequency of the channel set in the frequency selection unit 204 is also changed. For example, when +3 MHz is changed to the local frequency in the initial state, +3 MHz is also changed to the channel set in the frequency selection unit 204.

  FIG. 6 is a graph showing the signals of the channels CH1 to CH5 in the analog signal subjected to frequency conversion and the blocking frequency of the filter, with the horizontal axis representing frequency and the vertical axis representing level (for simplicity, The signal is represented by a bar graph). In the example of FIG. 6, the signal of channel CH5 shows the strongest level at 18 MHz. Therefore, the local frequency of the local oscillator 301 is set to 67 MHz. As a result, the 18 MHz signal is converted into a 21 MHz signal, and the level of the signal can be lowered. As a result, all signals can be AD converted without exceeding the dynamic range of the AD converter 203.

  As described above, in the first modification, the filter 601 is further provided in the broadband RF front end unit 101, so that the level of the signal that causes the dynamic range to be exceeded can be reduced. Thereby, the disappearance of the signal due to AD conversion can be reduced.

<Modification 2>
Next, a case where a signal of a plurality of channels is transmitted from a broadcasting station near the vehicle will be described. For example, because Tokyo Tower transmits 6 channels of signals in the frequency band of 76 to 90 MHz, Tokyo Tower can demodulate signals of channels transmitted from distant broadcasting stations near Tokyo Tower. It is necessary to lower the signal levels of the six channels transmitted from the.

  Therefore, in the second modification, a configuration in which the broadband RF front end unit 101 further includes a plurality of filters 1001 and a filter selection unit 1002 as illustrated in the block diagram of FIG. In addition, the same code | symbol is attached | subjected about the same function as the function shown in the block diagram of FIG. 1 or 7, and the description is abbreviate | omitted.

  The plurality of filters 1001 have the same function as the filter 601. Each of the frequency bands of the plurality of filters 1001 corresponds to the channel of the received signal.

  The filter selection unit 1002 has a function of selecting a filter used for filter processing from a plurality of filters 1001. As the filter selection unit 1002, an existing switch circuit may be applied.

FIG. 8 is a diagram illustrating an example of a plurality of filters 1001 and a filter selection unit 1002. In the example of FIG. 8, one changeover switch is connected to one filter. The changeover switch plays a role of selecting whether or not to use the filter for the filter processing. When the switch is connected to the filter side, the filter is used for filtering. This switch is switched for each filter. That is, the switch is switched so that only the filter corresponding to the channel causing the excess of the dynamic range of the AD converter is subjected to the filtering process. As a result, all signals can be demodulated even if there are a plurality of nearby broadcasting stations.

  The function and processing flow of the radio signal receiver according to the second modification will be described below. In the second modification as well, the case where the vehicle receives the analog signal A1 of the channels CH1 to CH5 of the FM radio will be described as in the above description.

  When the user turns on the radio signal receiver, the amplifier 201 amplifies the analog signal received, and the frequency converter 202 shifts the frequency of the amplified analog signal to the low frequency side.

  FIG. 9A is a graph showing an analog signal shifted to the low frequency side, with the horizontal axis representing frequency and the vertical axis representing level (for simplicity, each signal is represented by a bar graph). . In the example of FIG. 9, the levels of the signals of the channels CH3 and CH5 are very strong compared to the levels of other signals (channels CH1, CH2, and CH4 signals), leading to an excess of the dynamic range. In the present embodiment, the signal levels of the channels CH3 and CH5 are lowered in the subsequent processing.

  Next, the filter selected by the filter selection unit 1001 reduces the signal level of a predetermined channel of the analog signal subjected to frequency conversion. In this embodiment, the state in which all the switches shown in FIG. 8 do not select a filter is set as the initial state of the filter selection unit. Therefore, there is no filter selected at this stage, and the level is not lowered.

  Then, the AD converter 203 converts the analog signal after the filter processing into a digital signal.

  Next, the frequency selection unit 204 selects a predetermined channel from the digital signal output from the AD converter 203, and the demodulation unit 205 demodulates the signal of the selected channel.

  Then, while the radio signal receiver is turned on, the frequency selection unit 204 continues to switch the channel to be selected (channels CH1 to CH5) in a time division manner.

  At this time, if there is a channel with no signal, the switch of the filter corresponding to the channel showing the strongest level among all channels is switched. When there are a plurality of channels showing the strongest level, the corresponding switches are switched. By repeating this switching, even if there are a plurality of signals that cause the dynamic range to be exceeded, those signals can be reduced.

  In the example of FIG. 9A, since the signal level of the channel CH5 is the strongest, the switch corresponding to the channel CH5 is switched. As a result, the signal level of the channel CH5 is lowered (FIG. 9B). However, since the signal level of the channel CH3 remains strong, there is a channel without a signal. Therefore, the switch corresponding to the channel CH3 is switched, and the signal level of the channel CH3 is lowered (FIG. 9C). As a result, all signals can be accommodated within the dynamic range.

As described above, in the second modification, the broadband RF front end unit 101 further includes a plurality of filters 1001 and a filter selection unit 1002, so that even if there are a plurality of signals that cause the dynamic range excess, The signal level can be reduced. Thereby, the signals of all the channels can be demodulated.

  In the present embodiment, the case where the present invention is applied to an FM radio broadcast receiver has been described. However, the present invention is not limited to FM radio broadcast, and any radio signal receiver using a plurality of channels having different frequency bands can be used. The present invention may be applied to anything such as terrestrial digital television broadcasting or FDMA communication.

FIG. 1 is a block diagram showing a functional configuration of a radio signal receiver. FIG. 2 is a diagram illustrating the switching process of the frequency selection unit in an analog manner. FIG. 3 is a diagram illustrating the relationship between the distance between the receiving station and the broadcasting station and the received signal strength. FIG. 4 is a diagram illustrating an example of filter processing according to the first modification. FIG. 5 is a block diagram illustrating a functional configuration of the wireless signal receiver according to the first modification. FIG. 6 is a diagram illustrating a method for controlling the local frequency of the local oscillator. FIG. 7 is a block diagram illustrating a functional configuration of a wireless signal receiver according to the second modification. FIG. 8 is a diagram illustrating an example of a plurality of filters and a filter selection unit. FIG. 9 is a diagram illustrating an example of the filter selection process and the filter process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Broadband RF front end part 102 Digital baseband part 201 Amplifier 202 Frequency converter 203 AD converter 204 Frequency selection part 205 Demodulation part 301 Local oscillator 302 Mixer 401-405 Band pass filter 406-410 Switch 501 Vehicle 502-504 Transmission station 601 , 1001 filter 1002 filter selection unit

Claims (4)

A wireless signal receiver comprising a broadband RF front end unit and a digital baseband unit,
The broadband RF front-end unit receives an analog signal including signals in a plurality of frequency bands, converts the analog signal into a digital signal, and outputs the digital signal.
The digital baseband unit is
Frequency selection means for selecting a predetermined frequency band from the digital signal;
Demodulation means for demodulating the signal in the selected frequency band;
With
The radio signal receiver, wherein the frequency selection means switches a frequency band to be selected by performing a multiplexing operation in a time division manner. The broadband RF front end section is
A filter for reducing the level of a signal in a predetermined frequency band in the received analog signal;
An AD converter that converts an analog signal after processing by the filter into a digital signal;
The wireless signal receiver according to claim 1, further comprising: The broadband RF front end unit further includes a converter for converting the frequency of the received analog signal,
The converter converts the frequency of the analog signal so that the frequency band of the signal showing the strongest level in the analog signal matches the frequency band of the filter;
The filter performs a filtering process on the converted analog signal,
The radio signal receiver according to claim 2, wherein the frequency selection unit shifts a frequency band to be selected to a low frequency or a high frequency side in accordance with a frequency conversion amount by the converter. The broadband RF front end section is
A plurality of filters each having a different frequency band to be reduced;
Filter selection means for selecting a filter to be used for filter processing from the plurality of filters;
The wireless signal receiver according to claim 2, further comprising:

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