JP2007288529A - Receiver for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver for vehicle which can properly eliminate noise by adjacent interferences and intermodulation interferences. <P>SOLUTION: The receiver for vehicle mixes a local oscillation signal into a received high-frequency signal to convert the received high-frequency signal into an intermediate-frequency signal, and processes the intermediate-frequency signal by filters 112 and 114 having a predetermined first pass frequency band and a second pass frequency band narrower than the first one, and detects a signal after processing. In a memory device 206 of the receiver for vehicle, interference frequency determination information for determining the frequencies of the adjacent interference waves and intermodulation interference waves from the position of the vehicle is stored. From the actual position detected by a GPS receiver 204 and the interference frequency determination information stored in the memory device 206, the frequencies of the adjacent interference waves and the intermodulation interference waves are determined. When the determined frequencies of the adjacent interference waves and the intermodulation interference waves are within the first pass frequency band, a pass signal of the second intermediate-frequency filter 114 is selected in a selector 120. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle receiver, and more particularly, to a vehicle receiver that demodulates a received high-frequency signal after converting it to an intermediate frequency signal.

  The receiver includes a local oscillator that generates a local oscillation signal, and a mixer that mixes a high-frequency signal received by an antenna with a locally generated signal generated by the local oscillator and converts it to an intermediate frequency signal. A system in which a mixed intermediate frequency signal is amplified and then demodulated is widely used. This is a so-called super-heterodyne method. By converting the signal received by the antenna into an intermediate frequency signal, circuits that require a wide operating frequency range can be minimized, and stable operation can be achieved. It is also possible to improve the selection characteristics.

  The intermediate frequency signal output from the mixer is amplified and demodulated after passing through a filter of a predetermined pass frequency band, and has two or more pass frequency bands as this filter. There are known ones in which one pass frequency band is selected and used.

  For example, this is the FM radio receiver described in Patent Document 1 as the prior art. Patent Document 1 discloses, as a conventional technique, any of a first intermediate frequency filter having a predetermined pass frequency bandwidth, a second intermediate frequency filter having a pass frequency band narrower than the frequency band of the first intermediate frequency filter, and any filter. An FM radio receiver comprising a selector for selecting whether to use and a noise detector for detecting noise contained in an intermediate frequency signal mixed by the mixer is described. In this FM radio receiver, when noise is detected by the noise detector, the second intermediate frequency filter is selected by the selector.

In this way, when adjacent interference occurs, the second intermediate frequency filter having a narrower pass frequency band is selected, so that noise due to adjacent interference can be reduced.
JP 2005-175784 A

  When the cause of noise is adjacent interference, the noise can be reduced by narrowing the pass frequency band in the intermediate frequency filter. Even when the cause of noise is intermodulation interference, the noise can be reduced by narrowing the pass frequency band. This is because the adjacent interference and intermodulation interference are caused by a signal having a frequency different from the frequency of the carrier wave of the target broadcast station.

  However, if the cause of noise is other than adjacent interference and intermodulation interference, such as overmodulation and multipath, the noise cannot be reduced even if the pass frequency band is narrowed, and the pass frequency band is narrowed. Only the sound quality degradation due to

  In the prior art described in the above-mentioned Patent Document 1, all cases where noise is detected without distinguishing whether the cause of the noise is adjacent interference or intermodulation interference, or otherwise. A narrowband filter is selected. Therefore, when the cause of noise is other than adjacent interference and intermodulation interference, the noise is not reduced and only the sound quality is deteriorated.

  In particular, in the case of a receiver for a vehicle, the frequency of the adjacent interference wave and the frequency of the intermodulation interference wave change as the vehicle moves. It was difficult.

  The present invention has been made based on this situation, and an object of the present invention is to provide a vehicle receiver capable of appropriately removing noise caused by adjacent interference and intermodulation interference.

In order to achieve the object, the invention according to claim 1 is a mixer that mixes a local oscillation signal with a received high-frequency signal to convert it into an intermediate frequency signal, and a local oscillator that provides the mixer with the local oscillation signal. The pass frequency band can be a predetermined first pass frequency band and a second pass frequency band narrower than the first pass frequency band, and the band variable filter device for filtering the intermediate frequency signal, and the band A vehicle receiver comprising a detector for detecting a signal filtered by a variable filter device,
A position detection device that sequentially detects the current position of the vehicle, and a storage device that stores interference frequency determination information for determining the frequencies of the adjacent interference wave and the intermodulation interference wave at the position based on the current position of the vehicle; Interference frequency determination means for determining the frequencies of adjacent interference waves and intermodulation interference waves based on the actual current position of the vehicle detected by the position detection device and the interference frequency determination information stored in the storage device And the frequency of the adjacent interference wave and the intermodulation interference wave determined by the interference frequency determination means is within the first pass frequency band, and passes the second pass through the pass frequency band of the band variable filter device. Filter switching control means for making a frequency band.

  The frequency receivable at the current position of the vehicle can be determined from information unique to each broadcasting station, such as the position of the radio tower and transmission power. Further, the frequencies of the adjacent interference wave and the intermodulation interference wave can be calculated from frequencies that can be received at the positions. According to the first aspect of the present invention, interference frequency determination information for determining the frequencies of the adjacent interference wave and the intermodulation interference wave is stored in the storage device. Then, the interference frequency determining means determines the frequencies of the adjacent interference wave and the intermodulation interference wave at the current position from the current position detected by the position detection device and the interference frequency determination information stored in the storage device, Since the frequency is switched to the second pass frequency band that is narrower than the first pass frequency band based on the fact that the frequency is within the first pass frequency band, noise due to adjacent interference and intermodulation interference is appropriately removed. be able to.

  According to a second aspect of the present invention, in the vehicle receiver according to the first aspect, the position detecting device includes a GPS receiver, and the vehicle is based on a signal from a GPS artificial satellite received by the GPS receiver. The present position is sequentially detected.

  In this way, if the current position of the vehicle is detected using a GPS receiver, the current position of the vehicle can be detected with high accuracy, so that the current position is likely to cause at least one of adjacent interference and intermodulation interference. Whether or not can be determined accurately. Therefore, adjacent interference and intermodulation interference can be more appropriately removed.

  The invention according to claim 3 is the vehicle receiver according to claim 1 or 2, further comprising a noise detection circuit for detecting noise included in the intermediate frequency signal output from the mixer, and the noise. The filter switching control means is executed based on the fact that the noise detected by the detection circuit is not less than a predetermined value set in advance.

  As described above, the noise detection circuit cannot distinguish whether the detected noise is caused by the adjacent interference, the intermodulation interference, or the other. When the noise detected by the detection circuit is equal to or greater than a predetermined value set in advance, since the filter switching control means is executed, when the cause of the noise is a cause other than adjacent interference or intermodulation interference, Unnecessarily narrowing the pass frequency band is prevented.

  The band-variable filter device may include two analog filter circuits as described in claim 4, or may use a digital filter as described in claim 5.

  According to a fourth aspect of the present invention, in the vehicle receiver according to any one of the first to third aspects, the band-variable filter device includes a first analog filter circuit whose pass frequency band is the first pass frequency band. And whether the first analog filter circuit or the second analog filter circuit is used based on a signal from the second analog filter circuit whose pass frequency band is the second pass frequency band and the filter switching control means. And a selector for selecting.

  According to a fifth aspect of the present invention, in the vehicle receiver according to any one of the first to third aspects, the band-variable filter device includes an AD conversion circuit that converts the intermediate frequency signal into a digital signal, and First filter processing means for passing a signal in the first pass frequency band from the digital signal converted by the AD converter circuit, and a signal in the second pass frequency band from the digital signal converted by the AD converter circuit A second filter processing unit; and a selection unit that selects which of the first filter processing unit and the second filter processing unit to use based on a signal from the filter switching control unit. It is characterized by.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a vehicular FM radio receiver 10 to which the present invention is applied. The vehicle FM radio receiver 10 includes a demodulation unit 100 and a navigation unit 200 that functions as a control unit that controls the demodulation unit 100.

  In the demodulator 100, the radio wave received by the antenna 102 is amplified by the RF amplifier 104 and output to the mixer 106. The local oscillator 108 generates a local oscillation signal having a predetermined frequency, and this local oscillation signal is also output to the mixer 106. The frequency of the local oscillation signal generated and output by the local oscillator 108 is determined based on the tuning frequency, and a local oscillation signal having a frequency capable of converting the frequency received by the antenna 102 into a certain intermediate frequency is obtained. Generated and output.

  The mixer 106 mixes the signal from the RF amplifier 104 and the local oscillation signal from the local oscillator 108 to convert the signal from the RF amplifier 104 into an intermediate frequency signal having a preset predetermined frequency. The frequency of the intermediate frequency signal is an intermediate frequency between the frequency of the high frequency signal received by the antenna 102 and the frequency of a signal (voice) output from the detector 124 described later.

  The intermediate frequency signal generated by the mixer 106 is amplified by the first intermediate frequency amplifier 110 and supplied to the first to third intermediate frequency filters 112, 114, or 116 selected by the selector 120. . Also output to the intermediate frequency signal level detection circuit 118.

  The first to third intermediate frequency filters 112, 114, and 116 are all analog filter circuits. The first intermediate frequency filter 112 is set to a predetermined first pass frequency band. The first pass frequency band is set to a relatively wide bandwidth centering on the intermediate frequency so that good sound quality can be obtained. The pass frequency band of the second intermediate frequency filter 114 is set to the second pass frequency band. The upper and lower limits of the second pass frequency band are set closer to the intermediate frequency than the upper and lower limits of the first pass frequency band with the intermediate frequency as the center. The pass frequency band of the third intermediate frequency filter 116 is set to the third pass frequency band. In the third pass frequency band, the upper limit is set between the upper limit of the first pass frequency band and the upper limit of the second pass frequency band with the intermediate frequency as the center, and the lower limit is set to the lower limit of the first pass frequency band and the second It is set between the lower limit of the pass frequency band. Note that if the width of the first pass frequency band is a, the width of the second pass frequency band is b, and the width of the third pass frequency band is c, then b <c ≦ a.

  The signal band-limited by the first intermediate frequency filter 112, the second intermediate frequency filter 114, or the third intermediate frequency filter 116 is output to the selector 120.

  The selector 120 selects one of the signals supplied from the first to third intermediate filters 112, 114, or 116 in accordance with a switching signal from the CPU 202 of the navigation unit 202 and supplies the selected signal to the second intermediate frequency amplifier 122. Output. In the initial setting state in which the switching signal is not supplied, the signal from the first intermediate frequency filter 112 is selected. Therefore, in a state where no noise is detected, the signal from the first intermediate frequency filter 112 is selected. The first to third intermediate frequency filters 112, 114, 116 and the selector 120 constitute a band variable filter device 121.

  The second intermediate frequency amplifier 122 amplifies the supplied signal and outputs the amplified signal to the detector 124. The detector 124 demodulates the supplied signal and outputs it from an output terminal (not shown).

  The intermediate frequency signal level detection circuit 118 detects an increase in the signal level of the entire signal from the first intermediate frequency amplifier 110.

  The high pass filter 126 passes a signal having a predetermined frequency higher than the upper limit frequency of the predetermined band in the intermediate frequency signal level detection circuit 118 and outputs the signal to the noise detector 128. The intensity of the signal output from the high-pass filter 126 represents the level of noise included in the intermediate frequency signal.

  The noise detector 128 detects noise based on the magnitude of the signal from the high pass filter 126 being a predetermined level or higher. Then, the noise detection result is output to the CPU 202 of the navigation device 200.

  The navigation device 200 includes the CPU 202, a GPS receiver 204, and a storage device 206. In addition, although not shown, a device (for example, a display, various operation switches, a microphone, a speaker, a remote controller, a ROM, a RAM, etc.) generally provided in the navigation device is also provided.

  The GPS receiver 204 functions as a position detection device that sequentially detects the current position of the vehicle, receives position measurement GPS signals transmitted from GPS satellites (not shown) that are artificial satellites, and the vehicle is currently running. Detect the latitude, longitude, and altitude of the current location. Instead of the GPS receiver 204 or in addition to the GPS receiver 204, other devices such as a geomagnetic sensor, a gyroscope, and a distance sensor may be provided as a position detection device. In the case where a plurality of position detection devices are provided, the vehicle position detection accuracy can be improved by detecting the position of the vehicle while complementing those pieces of information.

  The storage device 206 includes, for example, a hard disk as a storage medium, and map data including road data, background data, character data, facility data, and the like is stored in the hard disk. Further, the storage device 206 stores the position of the radio tower of the broadcasting station, the transmission power therefrom, and the frequency to be transmitted.

  The position, transmission power, and transmission frequency of the radio tower of the broadcasting station are interference frequency determination information for determining the frequencies of adjacent interference waves and intermodulation interference waves. The CPU 202 determines the frequencies of the adjacent interference wave and the intermodulation interference wave based on the interference frequency determination information, and sends a switching signal to the selector 120 based on the determined frequencies of the adjacent interference wave and the intermodulation interference wave. Output.

  FIG. 2 is a flowchart showing processing executed by the CPU 202 to output the switching signal. The process shown in FIG. 2 is repeatedly executed at a predetermined cycle.

  First, in step S10, based on the signal from the noise detection circuit 128, it is determined whether or not noise of a predetermined value or more has been detected. When this determination is negative, this routine is terminated.

  On the other hand, when the determination in step S10 is affirmative, steps S20 to S30 corresponding to the disturbance frequency determining means are executed. In step S20, the current position of the host vehicle is determined based on the signal from the GPS receiver 204, and broadcast that can be received based on the interference frequency determination information stored in the storage device 206 and the current position of the host vehicle. Determine all stations. Specifically, the distance from the vehicle to the radio tower is calculated from the current position of the vehicle and the positions of the radio towers around the vehicle, and the radio tower is calculated based on the transmission power of the radio tower. Determine whether you can receive radio waves from. By making this determination for all the radio towers within a predetermined range around the vehicle, all the frequencies of the receivable broadcasting stations are determined.

  In subsequent step S30, the frequencies of the adjacent interference wave and the intermodulation interference wave are determined based on the frequency of the receivable broadcasting station determined in step S20. The frequency of the adjacent interfering wave corresponds to the frequency excluding the tuned frequency among all the frequencies determined in step S20. The frequency of the intermodulation interference wave can be obtained as a second-order term or a third-order term of the frequency of the adjacent interference wave.

  When the frequency of the intermodulation interference wave is the tuning frequency f0 (= 79.5 MHz) and the adjacent interference frequency is f1 (= 82.5 MHz), f2 (= 77.8 MHz), f3 (= 80.7 MHz) Will be described as an example. In this case, secondary terms include f1-f2 (= 4.7 MHz), f1 + f2 (= 160.3 MHz), f2 + f3 (= 158.5 MHz), and the like. Further, as the third order terms, there are 2f1-f2 (= 87.2 MHz), 2f2-f1 (= 73.1 MHz), f1 + f2-f3 (= 79.6 MHz), and the like.

  Subsequently, steps S40 to S60 corresponding to the filter switching control means are executed. In step S40, it is determined whether or not the frequency determined in step S30 is within the pass frequency band of the first intermediate frequency filter 112, that is, the first pass frequency band. For example, in the case of the above specific example, while the tuning frequency is 79.5 MHz, 79.6 MHz is determined as one of the intermodulation interference frequencies, so step S40 is affirmative. .

  If step S40 is affirmative, a switching instruction signal instructing switching to the second intermediate frequency filter 114 is output to the selector 120 in step S50. When this switching instruction signal is input to the selector 120, the selector 120 outputs a signal from the second intermediate frequency filter 114 having a narrower band than the first intermediate frequency filter 112 to the second intermediate frequency amplifier 122. To do.

  On the other hand, if step S40 is negative, the process proceeds to step S60. In this case, noise is detected, but the cause of the noise is neither adjacent interference nor intermodulation interference. Therefore, the second intermediate frequency is narrower than the first intermediate frequency filter 112. A switching instruction signal for switching to the third intermediate frequency filter 116 having a wider band than the filter 114 is output to the selector 120. As a result, it is possible to prevent the pass frequency band from being narrowed too much even if the cause of noise is not adjacent interference or intermodulation interference, and as a result, noise cannot be removed and only sound quality is deteriorated. it can.

  As described above, according to the present embodiment described above, the interference frequency determination information (position of the radio tower of the broadcasting station, transmission power, transmission frequency) for determining the frequencies of the adjacent interference wave and the intermodulation interference wave is stored in the storage device 206. I remember it. 2, from the current position detected by the GPS receiver 204 and the interference frequency determination information stored in the storage device 206, the adjacent interference wave and the intermodulation interference wave at the current position are detected. The frequency is determined. Further, when the frequencies of the adjacent interference wave and intermodulation interference wave are within the first pass frequency band, the second pass frequency band having a narrower band than the first pass frequency band is selected ( Step S50). Therefore, it is possible to appropriately remove noise due to adjacent interference and intermodulation interference.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also contained in the technical scope of this invention, and also the summary other than the following is also included. Various modifications can be made without departing from the scope.

  For example, in the above-described embodiment, the band-variable filter device 121 includes the first to third intermediate frequency filters 112, 114, and 116 that are analog filters. The intermediate frequency signal may be processed by. FIG. 3 is a block diagram illustrating a configuration of a vehicle FM receiver 300 including a band variable filter device 410 that processes an intermediate frequency signal by digital filter processing.

  The vehicle FM receiver 300 of FIG. 3 includes a demodulation unit 400 and a navigation unit 200 having the same configuration as that of the above-described embodiment. The demodulator 400 includes a DSP (Digital Signal Processor) 410 and the same antenna 102, RF amplifier 104, mixer 106, local oscillator 108, and first intermediate frequency amplifier 110 as those in the above-described embodiment.

  The DSP 410 includes an AD conversion circuit 411. The AD conversion circuit 411 converts an analog signal supplied from the first intermediate frequency amplifier 110 into a digital signal, and outputs an intermediate frequency signal level detection processing unit 412 and a band variable filter. Output to the unit 420.

  Further, in the DSP 410, the intermediate frequency signal level detection processing means 412, the high pass filter 413, the noise detection processing means 414, the second intermediate frequency processing means 415, and the detection processing means 416 are respectively the intermediate frequency signal level detection of the above-described embodiment. This corresponds to the circuit 118, the high-pass filter 126, the noise detection circuit 128, the second intermediate frequency amplifier 122, and the detector 124. These realize the same functions as the corresponding circuits by digital filter signal processing.

  The band variable filter unit 420 includes first to third filter processing units 421, 422, and 423, and a selection unit 424. The pass frequency bands of the first to third filter processing means 421, 422, and 423 are set to the first to third pass frequency bands of the above-described embodiment, respectively. The selection unit 424 has the same function as the selector 120 of the above-described embodiment. Therefore, the vehicle FM receiver 300 of FIG. 3 can obtain the same effects as those of the above-described embodiment.

  In the above-described embodiment, the three intermediate frequency filters 112, 114, and 116 are provided. However, only the first and second intermediate frequency filters 112 and 114 may be provided. Further, four or more intermediate frequency filters having different pass frequency bands may be provided.

It is a block diagram which shows the structure of FM radio receiver 10 for vehicles to which this invention was applied. 6 is a flowchart illustrating processing executed by the CPU 202 to output a switching signal. It is a block diagram which shows the structure of FM receiver 300 for vehicles provided with the band variable filter apparatus 410 which processes an intermediate frequency signal by a digital filter process.

Explanation of symbols

10: FM receiver for vehicle 106: Mixer 108: Local oscillator 112: First intermediate frequency filter (first analog filter circuit) 114: Second intermediate frequency filter (second analog filter circuit) 120: Selector, 121: Band-variable filter device, 122: Second intermediate frequency amplifier, 124: Detector, 204: GPS receiver (position detection device), 206: Storage device, 300: FM receiver for vehicle, 410: DSP 412: Intermediate frequency signal level detection processing means, 413: HPF, 414: Noise detection processing means, 415: Second intermediate frequency processing means, 416: Detection processing means, 417: DA conversion circuit, 420: Band variable filter device, 421: first filter processing means, 422: second filter processing means, 424: selection means, S20 to S30: interference frequency determination means, S40 to S60: filter switching control means

Claims (5)

A mixer for mixing the local oscillation signal with the received high-frequency signal and converting it to an intermediate frequency signal;
A local oscillator for providing the mixer with the local oscillation signal;
A band variable filter device that can set the pass frequency band to a predetermined first pass frequency band and a second pass frequency band that is narrower than the first pass frequency band, and filters the intermediate frequency signal;
A vehicle receiver comprising a detector for detecting a signal filtered by the band-variable filter device,
A position detection device for sequentially detecting the current position of the vehicle;
A storage device that stores interference frequency determination information for determining the frequency of the adjacent interference wave and the intermodulation interference wave at the position based on the current position of the vehicle;
Interference frequency determination means for determining the frequencies of adjacent interference waves and intermodulation interference waves based on the actual current position of the vehicle detected by the position detection device and the interference frequency determination information stored in the storage device When,
Based on the fact that the frequencies of the adjacent interference wave and the intermodulation interference wave determined by the interference frequency determining means are within the first pass frequency band, the pass frequency band of the band variable filter device is changed to the second pass frequency band. And a filter switching control means. 2. The position detection device includes a GPS receiver, and sequentially detects the current position of the vehicle based on a signal from a GPS artificial satellite received by the GPS receiver. Vehicle receiver. A noise detection circuit for detecting noise included in the intermediate frequency signal output from the mixer;
3. The filter switching control means is executed based on the fact that noise detected by the noise detection circuit is equal to or greater than a predetermined value set in advance. Vehicle receiver. The band variable filter device includes:
A first analog filter circuit whose pass frequency band is the first pass frequency band;
A second analog filter circuit whose pass frequency band is the second pass frequency band;
2. A selector for selecting which one of the first analog filter circuit and the second analog filter circuit to use based on a signal from the filter switching control means. The receiver for vehicles in any one of thru | or 3. The band variable filter device includes:
An AD conversion circuit for converting the intermediate frequency signal into a digital signal;
First filter processing means for passing a signal in the first pass frequency band from the digital signal converted by the AD conversion circuit;
Second filter processing means for passing a signal in the second pass frequency band from the digital signal converted by the AD conversion circuit;
2. A selection means for selecting which of the first filter processing means and the second filter processing means to use based on a signal from the filter switching control means. The receiver for vehicles in any one of thru | or 3.

Images