JP4606345B2 - Reception device and in-vehicle communication system - Google Patents

Description

  The present invention relates to a receiving apparatus and an in-vehicle communication system including the receiving apparatus, and more particularly to a receiving apparatus and an in-vehicle communication system that multiplex and process signals received by a plurality of antennas.

In recent years, various devices using wireless communication technology have been used. For example, as wireless communication devices used in vehicles, there are various types such as ETC (Electronic Toll Collection), GPS (Global Positioning System), VICS (Vehicle Information and Communication System), wireless LAN, AM / FM radio, television, and cellular phone. There is something. Also, various communication methods are used in each device. For example, various systems such as IEEE802.11a, b, and g are used in a wireless LAN, and wireless systems having different frequency bands, modulation systems, access systems, and the like are also used in mobile phones.

In general wireless devices, radio waves received from an antenna are transmitted at an intermediate frequency (IF: Intermediate).
Frequency) and using a band-pass filter having an excellent cutoff characteristic, reception sensitivity and selectivity are increased. When digital signal processing is performed, the received analog signal is converted into a digital signal, and digital signal processing is performed by a DSP (Digital Signal Processor).

  Here, since there are various radio systems as described above, the use of a radio apparatus equipped with a dedicated antenna, frequency converter, filter, and A / D converter for each radio system increases the size of the apparatus. This causes problems such as an increase in cost and an increase in power consumption. Therefore, Patent Document 1 discloses a configuration in which an A / D converter and a DSP are combined into one by multiplexing and processing IF signals from a plurality of front ends. FIG. 5 is a diagram showing a configuration of a wireless communication apparatus according to the conventional example. In this wireless communication device, the frequency converter 52 converts the signal received by the antenna 51 into an intermediate frequency at each front end. The IF signal output from each front end is multiplexed by the multiplexer 54, the multiplexed IF signal is converted into a digital signal by one A / D converter 55, and the IF signal converted into the digital signal is converted into a digital signal. A configuration for digital signal processing by the DSP 56 is disclosed.

As a wireless device having a plurality of front ends, a receiver using a spatial diversity method is known. The spatial diversity method is a method of receiving signals of the same frequency by two antennas that are distant from each other, and eliminates the influence of multipath fading by using a received signal with higher sensitivity. Patent Document 2 discloses a technique for controlling the presence / absence of an amplitude attenuation function for each antenna input in a spatial diversity wireless reception system.
JP 2002-335177 A JP-A-7-154316

  However, when the configuration is simplified by sharing the A / D converter as in the technique described in Patent Document 1, it is conceivable that the reception performance deteriorates. That is, since the IF signal is multiplexed, when attention is paid to a signal of a specific frequency, the other signal corresponds to noise, and the communication quality may deteriorate.

  Further, since the level of each IF signal is fixedly assigned at the time of IF signal synthesis, adaptive control cannot be performed according to the communication state and function priority.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for improving the communication quality of a wireless receiver that multiplexes and processes IF signals.

  In order to achieve the above object, in the present invention, wireless communication is received by the following means or processing. A first aspect of the present invention is a receiving apparatus that multiplexes and processes signals received by a plurality of antennas. The receiving apparatus according to the present invention is a receiving apparatus having a plurality of front ends, level adjusting means, combining means, A / D conversion means, signal processing means, and level control means.

  Each front end includes an antenna, frequency conversion means, and a filter. The frequency conversion means converts the frequency of the signal received from the antenna to a predetermined frequency (intermediate frequency: IF) lower than that. The filter passes only a signal in a predetermined frequency range (reception band) from the signal converted to the intermediate frequency (IF signal). Here, since the received signal is lowered to the intermediate frequency, it is possible to use a filter having excellent cutoff characteristics, and the receiving sensitivity and selectivity of the receiving device are improved.

  The level adjusting means adjusts the level of the IF signal output from each front end. That is, the level adjusting means performs processing for amplifying or attenuating the IF signal.

  The synthesizing unit synthesizes the IF signals that are output from the plurality of front ends described above and subjected to level adjustment. Note that the intermediate frequency at each front end is set to a different frequency and adjusted so as not to cause interference during multiplexing. The A / D conversion means converts the IF signal multiplexed by the synthesis means from an analog signal to a digital signal. Then, the signal processing means performs digital processing on the signal obtained by the A / D conversion means. As described above, the A / D conversion means and the signal processing means can be shared by multiplexing the IF signals, and the apparatus can be reduced in size and the manufacturing cost can be reduced.

  The level control unit controls interference between the multiplexed IF signals by controlling the level adjustment amount performed by the level adjustment unit. Specifically, it is preferable to determine the level adjustment amount of the signal output from each front end based on the demodulation information of the signal processing means. For example, when a high quality (high signal-to-noise ratio) signal is required for proper reception, it is preferable to increase the level adjustment amount of this signal. Thus, the level control means determines the level adjustment amount at the time of signal multiplexing based on the demodulation information of the combined IF signal, so that the communication quality can be optimized adaptively. It is also preferable that the level control means determines the level adjustment amount so that the level of the signal during carrier sense is lower than the level of the signal during communication. Signal strength when detecting whether another wireless device is communicating using a certain frequency band or detecting whether another wireless device is transmitting a signal to its own device (during carrier sense) However, it is preferable that the level of the signal during communication is high. Thus, suitable communication quality can be ensured by adjusting the signal level in accordance with carrier sense or communication.

  Further, the level control means may determine the level adjustment amount according to the priority determined for each radio system corresponding to each front end. By adopting such a configuration, it is possible to ensure communication quality of a wireless system that is preferentially required. Here, the priority for each wireless method does not need to be determined in advance, and may be determined based on demodulation information of the signal processing means.

  The second aspect of the present invention is an in-vehicle communication system including the receiving device according to the first aspect. In this aspect, vehicle state acquisition means for acquiring the vehicle state is further provided, and the level control means of the receiving device determines an adjustment amount for level adjustment of the IF signal output from each front end in accordance with the vehicle state. Examples of the vehicle state include the position of the vehicle, whether the vehicle is traveling or stopped, the traveling speed, the time since the engine was started, the presence or absence of collision prediction, the presence or absence of theft detection, and the like. Corresponding to these, examples of vehicle state acquisition means include GPS, shift lever (gear), vehicle speed sensor, key switch, impact sensor, and anti-theft device.

  The level control means determines the level adjustment amount so as to increase the level of the ETC signal if, for example, it is known by GPS that the position of the vehicle is near the toll gate. Further, for example, immediately after the engine is started, the level adjustment amount of the signal related to the VICS is increased so that the traffic information can be acquired quickly because the traffic jam information is not accumulated. As described above, by increasing the communication level adjustment amount that is preferentially required according to the vehicle state, it is possible to ensure the quality for the communication method having a high priority.

  A third aspect of the present invention is a vehicle including the on-vehicle communication system according to the second aspect.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to improve the communication quality of the radio | wireless receiver which multiplexes and processes IF signal.

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

(First embodiment)
The first embodiment of the present invention is a wireless communication apparatus capable of communicating with three types of communication systems. The three types of communication systems are wireless LAN, terrestrial digital television broadcasting, and mobile phone (cellular phone). The wireless communication apparatus according to the present embodiment receives radio waves transmitted from each of these systems with an antenna corresponding to each system, multiplexes the received radio waves, and performs digital processing.

  FIG. 1 is a diagram illustrating a configuration of a wireless communication apparatus according to the present embodiment. In addition, since this radio | wireless communication apparatus has the characteristic in a reception function, only a reception function is demonstrated and description about a transmission function is abbreviate | omitted.

  The wireless communication apparatus includes three RF front ends 1a, 1b, and 1c in order to receive wireless communication of three different systems. The RF front end 1a includes an antenna 10a, a frequency converter 13a including a local oscillator 11a and a mixer 12a, and an IF filter 14a. The frequency conversion unit 13a down-converts the received signal to a predetermined intermediate frequency (IF) by combining the frequency of the signal received by the antenna with the signal transmitted from the local oscillator 11a by the mixer 12a. The IF filter 14a is a band-pass filter that passes only a signal in a predetermined frequency domain (reception domain) among the down-converted IF signal.

  Since each of the RF front ends 1b and 1c is the same as the RF front end 1a, a description thereof will be omitted. However, the intermediate frequencies used in the RF front ends 1a, 1b, and 1c need to be different with a predetermined interval so that multiplexed signals do not interfere with each other.

The amplification attenuators 2a, 2b, and 2c adjust the level of the IF signal output from the RF front ends 1a, 1b, and 1c. This adjustment is performed based on an instruction from the level control unit 6 described later. Details of the level adjustment will be described later together with the description of the level control unit 6. The amplification attenuators 2a, 2b, and 2c correspond to the level adjusting means of the present invention, and the level control unit 6 corresponds to the level control means.

  The mixer 3 multiplexes IF signals output from the RF front ends 1a, 1b, and 1c. The A / D converter 4 converts the multiplexed IF signal into a digital signal, and the DSP 5 performs digital signal processing such as channel separation and modulation / demodulation on the multiplexed signal.

  In this way, radio waves of different wireless systems such as a wireless LAN, terrestrial digital TV, and mobile phone can be received simultaneously. For example, while watching a terrestrial digital TV, calling with a mobile phone and downloading data from the Internet at the same time. become able to. In this wireless communication apparatus, since the A / D converter 4 and the DSP 5 are shared, the apparatus can be reduced in size and weight, the manufacturing cost can be reduced, and the power consumption can be reduced.

  The level control unit 6 controls the amount of level adjustment in the amplification attenuators 2a, 2b, and 2c of each RF front end based on the demodulation information of the DSP 5. As the control method performed by the level control unit 6, the following methods are conceivable. For example, during carrier sense to check whether there is a radio wave addressed to its own terminal or to check whether the communication path is free prior to transmission, the IF signal to be output is higher than when actually communicating. It is preferable to control the level to be low. When the terrestrial digital television broadcast is being received and the wireless LAN and the cellular phone are not communicating, the IF signal levels of the wireless LAN and the cellular phone are lowered as shown in FIG. Since the required signal level is low during carrier sense, the level of the IF signal of the wireless LAN and mobile phone can be lowered, thereby reducing the noise of the IF signal of digital terrestrial television broadcasting and improving the communication quality of the entire communication device. .

  In addition, when a plurality of wireless systems are communicating simultaneously, it is also preferable to adjust the level of the IF signal in accordance with a predetermined priority for each wireless system. For example, when communication is being performed in all three types of wireless systems, the highest priority is set for the mobile phone, and the priority is decreased in the order of terrestrial digital television and wireless LAN. When the IF signal level is adjusted according to such priorities, when communication is being performed in all three systems, as shown in FIG. 3, the cellular phone, the digital terrestrial television, and the wireless LAN are prioritized in this order. The level of the IF signal is adjusted so as to ensure communication quality. Note that the above priority setting is merely an example and may be set in any manner.

  Further, when the IF signal input to the DSP 5 has a lot of noise and a high error rate, it is also preferable to perform level adjustment to increase the level of the IF signal and / or level adjustment to decrease the level of another IF signal. . By performing such adjustment, it is possible to adaptively adjust the level of each IF signal in accordance with the reception sensitivity of the received signal to obtain the optimum communication quality.

  Thus, when multiplexing IF signals of a plurality of methods, it is possible to ensure optimum communication quality as the whole wireless communication apparatus by adjusting the level of each IF signal. Further, the communication quality of communication necessary for the user can be ensured by largely adjusting the level of the IF signal having a high priority. In addition, since the noise applied to other IF signals is reduced by adjusting the level of the IF signal, the frequency interval between the IF signals can be reduced, and the occupied band of the IF signal can be reduced. Alternatively, since the influence on other IF signals is small, even if a filter with low filter performance is used as the IF filter (bandpass filter) 14, a certain communication quality can be ensured, and the manufacturing cost can be suppressed.

  In the above description, three examples of signals to be received are wireless LAN, digital terrestrial television broadcasting, and mobile phone. However, even if there are three or more types, RF front ends are provided for the number of types of received signals. If the frequency is converted to a predetermined IF frequency and multiplexed, these three or more types of received signals can be processed simultaneously. The received signal system is not limited, and any received signal in a different frequency band, a different modulation system, a different access system, or a combination thereof may be received.

The DSP 5 and the level control unit 6 are assumed to be configured using dedicated hardware. At this time, an FPGA (Field Programmable Gate Array), a reconfigurable chip (Reconfigurable Chip), or the like is used. It is preferable to use a reconfigurable device. Since the reconfigurable device can change the wiring circuit by software, the contents of processing can be changed by changing only the software without changing the hardware.

(Second Embodiment)
The second embodiment of the present invention is an in-vehicle wireless communication system including the wireless communication device according to the first embodiment. The wireless communication apparatus in this embodiment can also communicate with three types of communication systems. The three types of communication systems are an automatic toll collection system (ETC), a road traffic information providing system (VICS), and a mobile phone (cellular phone). As in the first embodiment, the wireless communication apparatus according to the present embodiment receives radio waves of these multiple methods and multiplexes and processes the received signals. Since the configuration and operation of the second embodiment are basically the same, the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 4 is a diagram illustrating a configuration of the in-vehicle wireless communication system according to the present embodiment. The wireless communication system is mounted on a vehicle, and the vehicle state acquisition unit 7 acquires the vehicle state. More specifically, the vehicle state acquisition unit 7 uses the vehicle control information acquisition means such as the GPS 71, the key switch 72, the vehicle speed sensor 73, and the airbag 74 to determine the position of the vehicle, whether it is running or stopped, Detects vehicle conditions such as travel speed and collisions. The vehicle state acquisition unit 7 refers to the vehicle state definition table 8 in which the relationship between the information obtained from these sensors and the vehicle state is stored in advance, and determines the vehicle state. That is, the in-vehicle wireless communication apparatus according to the present embodiment uses a vehicle control information acquisition unit that acquires vehicle control information, and a vehicle state definition table that stores in advance the association between the vehicle control information and the vehicle state. Get the status.

  As in the first embodiment, the level control unit 6 in the present embodiment is based on the communication state (communication or carrier sense) of each wireless method, the priority of each function, and the communication quality of each IF signal. The level of the IF signal can be adjusted. Furthermore, the level control unit 6 in the present embodiment can adjust the level of the IF signal based on the vehicle state acquired by the vehicle state acquisition unit 7.

  For example, when it is detected from the GPS 71 that the position of the vehicle is near the toll gate on the toll road, the ETC communication can be performed satisfactorily by adjusting the level of the ETC IF signal. Become. If it is detected from the key switch 72 that the engine has been started, it is preferable to make an adjustment to increase the level of the IF signal of the VICS. This is because traffic information is not acquired immediately after the engine is started, and it is desired to acquire traffic information as soon as possible. Further, when a collision is detected by the airbag 74 (starting up), priority is given to the function of the mobile phone, which is a means for communicating with the outside, by increasing the level of the IF signal of the mobile phone. In addition to this, the level of the IF signal is adjusted by appropriately setting the priority of the communication function according to the state of traveling or stopping.

As described above, the in-vehicle wireless communication system according to the present embodiment multiplexes IF signals so that A
By sharing the / D converter and the DSP, the same effects as those of the first embodiment such as reduction in size and weight of the device and cost reduction can be obtained. The in-vehicle wireless communication device has a great merit of miniaturization because the installation area is particularly limited. Further, when multiplexing IF signals of a plurality of systems, communication quality can be improved by adjusting the level of each IF signal. Furthermore, priority of each communication method can be determined according to the vehicle state, and communication quality with high priority can be ensured.

It is a figure which shows the structure of the radio | wireless communication apparatus which concerns on 1st Embodiment. It is a figure explaining the level adjustment process at the time of IF signal multiplexing. It is a figure explaining the level adjustment process at the time of IF signal multiplexing. It is a figure which shows the structure of the vehicle-mounted radio | wireless communications system which concerns on 2nd Embodiment. It is a figure which shows the structure of the conventional radio | wireless communication apparatus.

Explanation of symbols

1a, 1b, 1c RF front end 10a, 10b, 10c Antenna 11a, 11b, 11c Local oscillator 12a, 12b, 12c Mixer
13a, 13b, 13c Frequency conversion unit 14a, 14b, 14c IF filter 2a, 2b, 2c Amplification attenuator 3 Mixer (multiplexer)
4 A / D converter 5 DSP
6 Level Control Unit 7 Vehicle State Acquisition Unit 71 GPS Device 72 Key Switch 73 Vehicle Speed Sensor 74 Airbag 8 Vehicle State Definition Table 100 Vehicle

Claims (4)

A receiving device that multiplexes and processes signals received by a plurality of antennas,
A plurality of front ends comprising an antenna, frequency conversion means for converting the frequency of a signal received by the antenna, and a filter that passes a signal in a predetermined frequency range from the frequency-converted signal;
Level adjusting means for adjusting the level of a signal output from each of the plurality of front ends;
Synthesizing means for synthesizing signals output from the plurality of front ends and level-adjusted;
A / D conversion means for digitally converting the signal synthesized by the synthesis means;
Signal processing means for digitally processing the signal obtained by the A / D conversion means;
Level control means for controlling the amount of level adjustment performed by the level adjustment means to suppress signal interference between multiplexed signals;
A receiving device comprising :
The level control means determines the level adjustment amount so that the level of the signal during carrier sense is lower than the level of the signal during communication.
A receiving apparatus. The receiving apparatus according to claim 1, wherein the level control unit determines an amount of level adjustment performed by the level adjustment unit based on demodulation information of the signal processing unit. The receiving device according to claim 1 or 2 ,
Vehicle state acquisition means for acquiring the vehicle state;
With
The in-vehicle communication system characterized in that the level control means determines an amount of level adjustment performed by the level adjustment means according to a vehicle state. A vehicle comprising the in-vehicle communication system according to claim 3 .

Images