JPWO2018207499A1 - Wireless communication device and wireless communication method - Google Patents

Abstract

A wireless communication device according to an embodiment of the present technology includes a communication unit, a conversion unit, a generation unit, and a supply unit. The communication unit is capable of transmitting and receiving radio waves for short-range communication. The conversion unit converts a received signal generated in response to reception of the radio wave for narrow-area communication to an intermediate frequency based on a first reference signal. The generation unit generates a transmission signal used for transmitting the radio waves for the short-range communication based on a second reference signal having a different frequency from the first reference signal. The supply unit can switch supply of the first reference signal to the conversion unit and supply of the second reference signal to the generation unit.

Description

  The present technology relates to a wireless communication device and a wireless communication method used for short-range communication.

  Patent Literature 1 discloses an in-vehicle wireless communication device using a Dedicated Short Range Communications (DSRC) system. The in-vehicle wireless communication device receives a high-frequency signal transmitted from a base station installed on the roadside. The received high-frequency signal is converted into an intermediate frequency based on a mixing frequency oscillated by a local oscillator (LO: Local Oscillator), and digital data and the like are read. (Patent Document 1 [0002] [0003] [0017] [0019] FIG. 1 etc.).

JP 2009-5279A

  Various systems using such short-range communication have been developed, and a technology for realizing miniaturization of a wireless communication device is required.

  In view of the circumstances described above, an object of the present technology is to provide a wireless communication device for short-range communication and a wireless communication method capable of realizing miniaturization of the device.

In order to achieve the above object, a wireless communication device according to an embodiment of the present technology includes a communication unit, a conversion unit, a generation unit, and a supply unit.
The communication unit is capable of transmitting and receiving radio waves for short-range communication.
The conversion unit converts a received signal generated in response to reception of the radio wave for narrow-area communication to an intermediate frequency based on a first reference signal.
The generation unit generates a transmission signal used for transmitting the radio waves for the short-range communication based on a second reference signal having a different frequency from the first reference signal.
The supply unit can switch supply of the first reference signal to the conversion unit and supply of the second reference signal to the generation unit.

  In this wireless communication device, the first and second reference signals having mutually different frequencies are appropriately switched and supplied to the conversion unit and the generation unit. As a result, for example, the intermediate frequency can be controlled, and data can be received without using an external filter or the like. As a result, it is possible to reduce the size of the wireless communication device.

The conversion unit may convert the received signal to the intermediate frequency by mixing the first reference signal and the received signal. In this case, the supply unit may control the frequency of the first reference signal so that the intermediate frequency is smaller than the frequency difference between the reception signal and the transmission signal.
Filtering is facilitated by reducing the value of the intermediate frequency. This eliminates the need for an external filter or the like, and makes it possible to reduce the size of the device.

The conversion unit may include a first internal filter that passes a frequency component of a first band including the intermediate frequency and regulates a frequency component not included in the first band.
Thereby, for example, filtering by a band pass filter configured in the integrated circuit becomes possible. As a result, it is possible to sufficiently reduce the size of the device.

The intermediate frequency may have an absolute value of 2.2 MHz or more and 2.8 MHz or less.
This makes it possible to suppress signals in channels of the short-range communication other than the target channel from becoming interference waves, and to improve communication accuracy.

The intermediate frequency may have an absolute value of about 2.5 MHz.
As a result, it is possible to sufficiently cut unnecessary signals such as interference waves, and it is possible to sufficiently improve communication accuracy.

The supply unit may control the frequency of the first reference signal so that the intermediate frequency becomes substantially zero.
This makes it possible to directly demodulate, for example, data included in the first high-frequency signal. As a result, the device configuration is simplified, and the device can be downsized.

The conversion unit may include a second internal filter that passes a frequency component of a second band including the intermediate frequency and regulates a frequency component higher than an upper limit frequency of the second band.
Thereby, for example, filtering by a low-pass filter configured in the integrated circuit becomes possible. As a result, it is possible to sufficiently reduce the size of the device.

The supply unit may include a phase locked loop circuit that can switch between the first and second reference signals and oscillate.
Thus, the first and second reference signals can be generated with high accuracy, and the operation accuracy can be improved.

The supply unit may include a frequency divider that divides the frequency of the second reference signal by a predetermined ratio to generate a frequency-divided signal. In this case, the generation unit may generate the transmission signal by performing mixing of the frequency-divided signal with a baseband signal and mixing of the second reference signal.
Thus, the frequency of the transmitted second high-frequency signal and the frequency of the second reference signal have different values. As a result, problems due to frequency coupling can be suppressed.

The predetermined ratio may be one of １ ／, ４, and ６.
For example, the frequency can be easily divided using a frequency divider or the like. This makes it possible to provide a device having a simple configuration and having resistance to coupling and the like.

The wireless communication device may further include a signal generation unit that generates a data signal based on the intermediate frequency signal.
This makes it possible to generate a data signal in accordance with, for example, a circuit at a later stage for performing data processing and the like, and high versatility is exhibited.

The data signal may include at least one of a QPSK signal, an ASK signal, and a carrier strength signal.
This makes it possible to support various communication systems used in narrow-area communication.

The signal generation unit may include a digital filter unit that digitizes and filters the intermediate frequency signal, and a mixer unit that converts an output of the digital filter unit into a frequency for demodulation.
As a result, it is possible to demodulate the data signal based on the signal filtered in the digital domain, and it is possible to greatly improve the communication accuracy.

The digital filter unit and the mixer unit may operate based on a reference clock signal.
By using the reference clock signal, for example, a dedicated clock circuit or the like is not required, and the device can be downsized.

The reception signal may be a signal having a lower frequency than the transmission signal.
This makes it possible to provide a wireless communication device that functions as a mobile station that performs communication while moving.

The wireless communication device may be configured as a vehicle-mounted device.
This makes it possible to provide a small-sized vehicle-mounted device capable of performing short-range communication.

A wireless communication method according to an embodiment of the present technology includes transmitting and receiving radio waves for short-range communication.
Based on the first reference signal, a reception signal generated in response to reception of the radio wave for narrow-area communication is converted to an intermediate frequency.
A transmission signal used for transmitting the radio waves for the short-range communication is generated based on a second reference signal having a frequency different from that of the first reference signal.
The supply of the first reference signal and the supply of the second reference signal are switched.

  As described above, according to the present technology, it is possible to reduce the size of a wireless communication device for short-range communication. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

1 is a schematic diagram illustrating a configuration example of a wireless communication device according to a first embodiment of the present technology. It is a figure which shows typically the relationship of the channel used for communication of DSRC system. FIG. 3 is a schematic diagram illustrating a frequency relationship of channels. FIG. 5 is a schematic diagram illustrating an example of conversion to an intermediate frequency by a quadrature mixer. FIG. 5 is a schematic diagram illustrating another configuration example of the wireless communication device according to the first embodiment. FIG. 9 is a schematic diagram illustrating a configuration example of a wireless communication device as a comparative example. FIG. 9 is a schematic diagram illustrating a configuration example of a wireless communication device according to a second embodiment. FIG. 11 is a schematic diagram illustrating a configuration example of a wireless communication device according to a third embodiment.

  Hereinafter, embodiments according to the present technology will be described with reference to the drawings.

<First embodiment>
[Configuration of Wireless Communication Device]
FIG. 1 is a schematic diagram illustrating a configuration example of a wireless communication device according to the first embodiment of the present technology. The wireless communication device 100 is configured as an in-vehicle device capable of performing communication in a short range communication system (DSRC system), and is used for communication with a base station or the like installed on a roadside or the like.

  By mounting the wireless communication device 100 on a vehicle such as an automobile, it is possible to pay a toll using an ETC (Electronic Toll Collection System) (registered trademark) service, obtain congestion information using an ETC 2.0 service, and the like. Becomes

  As illustrated in FIG. 1, the wireless communication device 100 includes a communication unit 10, a reception unit 20, a transmission unit 30, and a local oscillator (LO: Local Oscillator) 40. Further, the wireless communication device 100 has a controller (not shown).

  The communication unit 10 includes an antenna 11, a band pass filter (BPF) 12, and a switch element 13.

  The antenna 11 can transmit and receive radio waves in a frequency band (5.8 GHz band) used in the DSRC system. The antenna 11 outputs an electric signal having the same frequency as the received electric wave, and emits an electric wave having the same frequency as the inputted electric signal. For example, as the antenna 11, a pattern antenna formed on a substrate, a chip antenna mountable on a substrate, or the like is used. In addition, the specific configuration of the antenna 11 is not limited, and an arbitrary antenna may be used.

  The band-pass filter 12 allows a frequency component of a frequency band used in the DSRC system among the frequency components of the electric signal input to the band-pass filter 12 to pass. Further, the band-pass filter 12 regulates a frequency component in another band different from the frequency band used in the DSRC system. The specific configuration of the bandpass filter 12 is not limited, and an arbitrary filter may be used.

  The switch element 13 switches an output destination of an input electric signal based on a control signal output from the controller. The specific configuration of the switch element 13 is not limited. For example, an arbitrary element that can be connected by switching circuits may be used.

  When communication (downlink communication) from the base station or the like to the vehicle-mounted device is performed, the antenna 11 receives a radio wave having the first frequency corresponding to the DSRC system transmitted from the base station or the like. An electric signal corresponding to the received radio wave is output to the band-pass filter 12 and filtered. As a result, the first high-frequency signal 51 having the first frequency is output to the switch element 13. The first high-frequency signal 51 is output to the receiving unit 20 via the switch device 13.

  When communication (uplink communication) from the vehicle-mounted device to the base station or the like is performed, as described later, the transmitting unit 30 generates the second high-frequency signal 52 having the second frequency corresponding to the DSRC method. The second high-frequency signal 52 is output to the band-pass filter 12 via the switch device 13. A radio wave having a second frequency is transmitted from the antenna 11 based on the second high-frequency signal 52 filtered by the band-pass filter 12.

  By using the switch element 13, transmission and reception can be switched and executed using one antenna 11. As a result, the number of parts can be reduced, and the cost of the apparatus can be reduced. The specific configuration of the switch element 13 is not limited. For example, an arbitrary element that can be connected by switching circuits may be used.

  In the DSRC scheme, radio waves having different frequencies are used for downlink communication and uplink communication. The radio wave used for downlink communication is a radio wave whose frequency is lower than the radio wave used for uplink communication. In the DSRC system, a frequency difference of 40 MHz is defined for each radio wave used in downlink communication and uplink communication.

  Therefore, the first and second frequencies corresponding to the DSRC scheme are different from each other. The first high-frequency signal 51 has a lower frequency than the second high-frequency signal 52, and the frequency difference between the first high-frequency signal 51 and the second high-frequency signal 52 is 40 MHz. In the present embodiment, the first high-frequency signal 51 corresponds to a reception signal generated in response to reception of a radio wave for short-range communication, and the second high-frequency signal 52 is used for transmission of radio waves for short-range communication. This corresponds to the transmission signal used.

  The receiving unit 20 includes a receiving amplifier 21, a quadrature mixer 22, and a band-pass filter (BPF) 23.

  The receiving amplifier 21 amplifies the first high-frequency signal 51 output via the switch element 13. Generally, an electric signal converted from a communication radio wave by the antenna 11 has a small intensity and is weak. The receiving amplifier 21 functions as a low noise amplifier (LNA) that amplifies such a weak electric signal to an intensity used for signal processing or the like. The amplified electric signal (first high-frequency signal 51) is output to quadrature mixer 22.

  For example, an amplifier using a CMOS (Complementary Metal Oxide Semiconductor) circuit or the like is used as the receiving amplifier 21. In addition, a low-noise amplifier using, for example, gallium arsenide (GaAs) or silicon germanium (SiGe) may be used. Further, the gain, noise figure, and the like of the receiving amplifier 21 may be appropriately set according to the receiving sensitivity and the like of the antenna 11.

  The quadrature mixer 22 converts the first high-frequency signal 51 amplified by the receiving amplifier 21 into an intermediate frequency. For conversion into the intermediate frequency, a first reference signal 41 oscillated by a local oscillator 40 described later is used. The quadrature mixer 22 converts the first high-frequency signal 51 into an intermediate frequency by mixing the first reference signal 41 and the first high-frequency signal 51.

  Generally, when two signals having frequencies f1 and f2 are mixed, a signal obtained by integrating the respective signals is output. The integrated signal includes a frequency component having a frequency similar to the difference (f1-f2) between the frequencies of the two signals. Further, the integrated signal includes a frequency component having the same frequency as the sum (f1 + f2) of the frequencies of the two signals.

  The quadrature mixer 22 mixes the first reference signal 41 and the first high-frequency signal 51 to generate a frequency component corresponding to the difference and sum of the frequencies of the first reference signal 41 and the first high-frequency signal 51. Is generated. In the present embodiment, the difference between the frequencies of the first reference signal 41 and the first high-frequency signal 51 is the intermediate frequency. Therefore, for example, by appropriately setting the frequency of the first reference signal 41, the intermediate frequency can be controlled to an arbitrary value.

  As shown in FIG. 1, the I signal 53 and the Q signal 54 are output from the quadrature mixer 22 as intermediate frequency signals. The I signal 53 and the Q signal 54 are signals including data modulated by a quadrature phase shift keying (QPSK) method.

  For example, the quadrature mixer 22 outputs a reference I signal having the same phase (Inter-Phase) as the first reference signal 41 and a reference Q signal having a quadrature phase (Quadrature-Phase) having a phase shifted by 90 ° from the reference I signal. Generate. The reference I signal is generated by directly using the first reference signal output from the local oscillator 40. The reference Q signal is generated by shifting the phase of the first reference signal 41 using a π / 2 phase shifter that shifts the phase by 90 °.

  The first high-frequency signal 51 and the reference I signal are mixed, and an I signal 53 is generated. Further, the first high-frequency signal 51 and the reference Q signal are mixed to generate a Q signal 54. For mixing the signals, a mixer or the like that integrates and outputs the two signals is used. Thereby, the first high-frequency signal 51 is converted into an I signal 53 and a Q signal 54 including a frequency component of the intermediate frequency. The I signal 53 and the Q signal 54 are output to the band pass filter 23.

  The quadrature mixer 22 is configured by a circuit including two mixers and the like that output an I signal 53 and a Q signal 54, for example. The specific configuration of the quadrature mixer 22 is not limited. For example, a circuit that can output the I signal 53 and the Q signal 54 may be appropriately used. Hereinafter, the I signal 53 and the Q signal 54 may be referred to as a first I / Q signal 55 in some cases.

  The bandpass filter 23 passes frequency components in a first band including the intermediate frequency, and regulates frequency components not included in the first band. That is, the band-pass filter 23 extracts the frequency component of the intermediate frequency included in the first I / Q signal 55 output from the quadrature mixer 22. In the present embodiment, the bandpass filter 23 corresponds to a first internal filter.

  The first band is set based on, for example, the occupied bandwidth (4.4 MHz) of each channel used in the DSRC scheme. For example, a band having a bandwidth of 4.4 MHz centered on the intermediate frequency is set as the first band. Thus, for example, a frequency component corresponding to the sum of the frequencies of the first reference signal 41 and the first high-frequency signal 51 and other noise components can be sufficiently reduced. The present invention is not limited to this. For example, an arbitrary band in which a frequency component of the intermediate frequency can be extracted may be set as the first band.

  The band-pass filter 23 is an internal filter configured in the integrated circuit, and includes, for example, a resistor, a capacitor, a transistor, and the like on a chip. In addition, the specific configuration of the bandpass filter 23 is not limited. For example, a filter that can extract a frequency component of the intermediate frequency may be used as appropriate.

  The first I / Q signal 55 filtered by the bandpass filter 23 is output to a subsequent circuit and demodulated by the QPSK method. In the DSRC system, an amplitude shift keying (ASK) system is used in addition to the QPSK system. For example, by detecting the signal strength of the I signal 53 and the Q signal 54 (the first I / Q signal 55), it is possible to perform demodulation by the ASK method.

  In the present embodiment, the receiving unit 20 corresponds to a converting unit that converts a received signal generated in response to reception of a radio wave for short-range communication into an intermediate frequency based on the first reference signal.

  The transmission unit 30 includes a modulation unit 31 and a transmission amplifier 32.

  The modulator 31 modulates the baseband signal generated by the controller based on the second reference signal 42 supplied from the local oscillator 40 to generate a second high-frequency signal. The second reference signal 42 is a signal having a different frequency from the first reference signal 41. In the present embodiment, the frequency of the second reference signal 42 is set to the second frequency used in uplink communication. The modulation unit 31 generates a second high-frequency signal 52 having a second frequency by mixing the second reference signal 42 with the baseband signal.

  As shown in FIG. 1, a baseband signal corresponding to the QPSK system or the ASK system is input to the modulation unit 31. In FIG. 1, the baseband signal is illustrated as an I signal 56 and a Q signal 57 (second I / Q signal 58).

  In the modulation section 31, a reference I signal having the same phase as the second reference signal 42 and a reference Q signal having a quadrature phase shifted from the reference I signal by 90 ° are generated. Modulation section 31 mixes reference I signal and I signal 56 and mixes reference Q signal and Q signal 57. The mixed I signal 56 and the mixed Q signal 57 are added and output using an adding circuit or the like. Thereby, the second high-frequency signal 52 having the second frequency including the information of the I signal 56 and the Q signal 57 is generated.

  The transmission amplifier 32 amplifies the second high-frequency signal 52 generated by the modulation unit 31. Generally, the intensity of the radio wave transmitted from the antenna 11 has a value corresponding to the intensity of the electric signal input to the antenna 11. The transmission amplifier 32 functions as a power amplifier (PA) that amplifies the second high-frequency signal so that the radio wave is transmitted from the antenna 11 with an appropriate intensity. The amplified second high-frequency signal is output to the communication unit 10.

  As the transmission amplifier 32, for example, an amplifier using a CMOS circuit or the like is used. Further, the gain, noise figure, and the like of the transmission amplifier 32 may be appropriately set according to the reception sensitivity of the antenna 11 and the like.

  In the present embodiment, the transmission unit 30 corresponds to a generation unit that generates a transmission signal used for transmitting radio waves for narrow-area communication based on a second reference signal having a different frequency from the first reference signal. .

  The local oscillator 40 switches between supplying the first reference signal 41 to the receiving unit 20 and supplying the second reference signal 42 to the transmitting unit 30 according to the transmission and reception of the DSRC radio wave. That is, when the radio wave of the first frequency is received, the first reference signal 41 is supplied to the receiving unit 20, and when the radio wave of the second frequency is transmitted, the second reference signal 42 is transmitted. Is supplied to the transmission unit. In the present embodiment, the local oscillator 40 corresponds to a supply unit.

  For example, when wireless communication apparatus 100 is in a state of performing reception / transmission, a controller outputs a control signal indicating the reception state / transmission state. The local oscillator 40 oscillates a first reference signal 41 in a reception state and oscillates a second reference signal 42 in a transmission state based on the communication state signal. This makes it possible to switch the supply of the first and second reference signals 41 and 42. The method of switching the supply of the first and second reference signals 41 and 42 is not limited, and an arbitrary method may be used.

  As the local oscillator 40, a phase lock (PLL: Phase lock loop) circuit that can oscillate by switching the first and second reference signals 41 and 42 is used. As shown in FIG. 1, the LO reference clock signal 43 is input to the PLL circuit. The LO reference clock signal 43 is a clock signal with high frequency stability generated using a quartz oscillator or the like.

  In the PLL circuit, feedback control is performed, and a periodic signal based on the LO reference clock signal 43 is generated. The frequency of the generated signal can be changed by appropriately operating the signal and the like used for the feedback control.

  For example, by changing the signal used for the feedback control according to the communication state of the wireless communication device 100, the first and second reference signals 41 and 42 having different frequencies can be switched and generated. . Note that the specific configuration of the local oscillator 40 is not limited, and an arbitrary oscillation circuit or the like that can switch and supply the first and second reference signals 41 and 42 may be used.

  The controller has hardware necessary for the configuration of the computer, such as a CPU, a ROM, a RAM, and an HDD. The wireless communication method according to the present technology is executed when the CPU loads a program recorded in advance in the ROM or the like into the RAM and executes the program. The specific configuration of the controller is not limited. For example, a device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

  The program is installed in the wireless communication device 100 via various recording media, for example. Alternatively, the installation of the program may be executed via the Internet or the like.

  The controller controls the operation of the entire wireless communication device 100. The controller generates a control signal indicating a reception state and a transmission state according to, for example, a communication state. The operations of the switch element 13, the local oscillator 40, and the like are controlled based on the generated control signal.

  The controller processes communication data transmitted and received by the DSRC method. For example, transmission data is generated based on the received data. The data for transmission is output to the transmission unit 30 as a baseband signal (second I / Q signal 58).

  FIG. 2 is a diagram schematically illustrating the relationship between channels used for DSRC communication. In the DSRC scheme, a channel is set for each communication frequency, and downlink communication and uplink communication are performed using a pair of channels having a frequency difference of 40 MHz. Also, the occupied bandwidth of each frequency channel is defined to be 4.4 MHz.

  In the DSRC scheme, seven channels of 5775 MHz, 5780 MHz,..., 5805 MHz at intervals of 5 MHz are defined for downlink communication. Also, channels for every 5 MHz of 5815 MHz, 5820 MHz,..., 5845 MHz are defined for uplink communication. Of these channels, the channels for downlink communication and uplink communication with a frequency difference of 40 MHz form a pair.

  Therefore, as shown in FIG. 2, in the DSRC scheme, seven pairs A to G of channels for downlink communication and uplink communication are prepared. Communication between the base station or the like and the wireless communication device 100 is performed using one of the pairs. For example, in pair A, a channel for downstream communication of 5775 MHz and a channel for upstream communication of 5815 MHz are used. The base station performs communication while fixing the channel, and the wireless communication device 100 performs communication according to the channel used by the base station.

  For example, it is assumed that a vehicle equipped with the wireless communication device 100 passes near a roadside where a base station is installed. First, the channel (channel for downlink communication) used by the base station is unknown, and the wireless communication device 100 executes a search for a channel. When a downlink communication channel is selected, wireless communication apparatus 100 sets the selected channel as a reception channel, and sets a channel that is paired with the reception channel as a transmission channel.

  It is assumed that, for example, 5790 MHz and 5830 MHz (pair D) are set as the reception and transmission channels. When the wireless communication device 100 is in the transmission state, the local oscillator 40 oscillates a signal having a frequency of 5830 MHz as the second reference signal and supplies the signal to the transmission unit 30. In the transmission section 30, the modulation section 31 mixes the 5830 MHz second reference signal and the baseband signal to generate a 5830 MHz second high frequency signal 52. The generated second high-frequency signal is output to the communication unit 10.

  The communication section 10 transmits a 5830 MHz radio wave based on the second high frequency signal 52. When the radio wave is transmitted, the wireless communication device 100 shifts to a reception state for receiving a response from the base station. For example, the switch element 13 switches the connection destination of the communication unit 10 from the transmission unit 30 to the reception unit 20. The local oscillator 40 switches the oscillation frequency from the second reference signal 42 to the first reference signal 41.

  A radio wave of 5790 MHz is transmitted from the base station to the wireless communication device 100 as a response. The communication unit 10 receives the radio wave of 5775 MHz, and generates the first high-frequency signal 51 of 5790 MHz. The generated first high-frequency signal 51 is input to the receiving unit 20.

  In the receiving unit 20, the first reference signal 41 and the first high-frequency signal 51 are mixed by the quadrature mixer 22, and the first high-frequency signal 51 is converted into a first I / Q signal 55 having an intermediate frequency. Is done. The first I / Q signal 55 is demodulated by a subsequent circuit, and the response content from the base station is output to the controller. As described above, in the wireless communication device 100, communication with the base station is performed using the pair of the channels of the downlink communication and the uplink communication. Although the channel of pair D has been described above as an example, other pairs of channels may be used.

  FIG. 3 is a schematic diagram illustrating a frequency relationship of channels. FIG. 3 schematically illustrates a reception channel 60 (downlink communication channel) used by the wireless communication device 100 for reception, and the next adjacent channels 61a and 61b. The horizontal axis in the figure is frequency, and the scale is set so that the center frequency of the reception channel 60 is 0 Hz.

  The next adjacent channels 61a and 61b are the second closest channels on the low frequency side and the high frequency side of the reception channel 60. For example, if the receiving channel 60 is the 5790 MHz channel of the pair D shown in FIG. 2, the next adjacent channels 61a and 61b are the 5780 MHz and 5800 MHz channels. That is, the next adjacent channels 61a and 61b are channels separated from the receiving channel 60 by 10 MHz on the low frequency side and the high frequency side.

  In the DSRC system, use of the two closest channels is restricted in order to avoid or reduce interference between the closest channels and communication errors due to leakage power. Therefore, it is rare that the two nearest channels are received at the same time. Therefore, for the receiving channel 60, there is a high possibility that the communication and the like performed on the next adjacent channels 61a and 61b which are the second closest will be the main interference waves.

  For example, in addition to the radio wave of the receiving channel 60, it is conceivable that an interfering wave of the next adjacent channels 61a and 61b is received. In this case, the communication unit 10 outputs a signal including the frequency component of the reception channel 60 and the frequency components of the next adjacent channels 61a and 61b. Accordingly, the communication unit 10 outputs a signal including the first high-frequency signal 51 (the frequency component of the reception channel 60) and the interference signal 62 (the frequency components of the next adjacent channels 61a and 61b).

  The first high-frequency signal 51 is mixed with the first reference signal 41 by the quadrature mixer 22, and the frequency components of the reception channel 60 and the next adjacent channels 61a and 61b are respectively frequency-converted. As a result, the center of the receiving channel 60 shifts to the intermediate frequency, and the center of each of the next adjacent channels 61a and 61b shifts to the low frequency side and the high frequency side to a frequency separated by 10 MHz from the intermediate frequency. That is, the frequency component of each channel is uniformly shifted to the lower frequency side by the frequency of the first reference signal 41.

  The frequency component of each channel shifted to the low frequency side is input to the band-pass filter 23 of the receiving unit 20. The first band of the band-pass filter 23 is set so as to extract the frequency components of the reception channel 60 and regulate the frequency components of the next adjacent channels 61a and 61b. That is, the band-pass filter 23 is configured to remove the interfering signal 62 (frequency components of the next adjacent channels 61a and 61b) separated by 10 MHz from the intermediate frequency.

  Generally, when the width of the pass band of a filter is constant, the filter can be easily configured as the frequency at which the pass band is set is lower. For example, when extracting a pass band of 10 MHz in a frequency range of several tens of MHz, it may be necessary to provide an external filter or the like having a steep band pass characteristic. On the other hand, when extracting a pass band of 10 MHz in a frequency region of several MHz, it is possible to remove an interfering signal by using an internal filter or the like configured in the integrated circuit.

  As described above, in the present embodiment, it is possible to control the intermediate frequency. Therefore, by setting the frequency of the intermediate frequency to a low frequency region, the pass band (first band) of the band-pass filter 23 can be set to a low frequency region. Thereby, the configuration of the bandpass filter 23 can be simplified. As a result, for example, an external filter or the like becomes unnecessary, and the device can be downsized.

  In the present embodiment, the frequency of the first reference signal is controlled by the local oscillator 40 so that the intermediate frequency is smaller than the frequency difference between the first high-frequency signal 51 and the second high-frequency signal. Specifically, the first reference signal 41 is set such that the intermediate frequency is a value smaller than 40 MHz.

  Since the value of the intermediate frequency is set to be small, the first band, which is the pass band of the band-pass filter 23, is also set to a low frequency region. That is, the center frequency of the first band is set to a frequency smaller than 40 MHz. Thus, for example, the bandpass filter 23 can be configured as an internal filter, and the device can be sufficiently reduced in size.

  The frequency difference between the frequency component of the reception channel 60 output from the quadrature mixer 22 and each frequency component of the next adjacent channels 61a and 61b remains at 10 MHz regardless of the value of the intermediate frequency. For this reason, even when the value of the intermediate frequency is reduced, the width of the pass band (first band) of the band-pass filter 23 is hardly changed. Therefore, the smaller the value of the intermediate frequency is, the lower the frequency at which the pass band is set is, and the frequency component of the reception channel 60 can be easily extracted.

  FIG. 4 is a schematic diagram showing an example of conversion to an intermediate frequency by the orthogonal mixer 22. 4A to 4C schematically show the reception channel 60 and the next adjacent channels 61a and 61b whose frequencies are shifted by the quadrature mixer 22.

  As the value of the intermediate frequency is reduced, a frequency component having a negative frequency is generated. The negative frequency is, for example, a frequency generated by frequency subtraction in the mixer (orthogonal mixer 22). For example, when a signal having a frequency f1 and a signal having a frequency f2 higher than f1 are mixed, the frequency difference (f1-f2) between the two signals is apparently minus. In this case, the mixer outputs the frequency component of the absolute value | f1−f2 | of the frequency difference between the two signals. This frequency component can be regarded as a component folded on the basis of 0 Hz, and causes image disturbance and the like.

  As shown in FIG. 4A, for example, when the intermediate frequency is set to 10 MHz, the center frequency of the next adjacent channel 61a on the low frequency side is 0 Hz. In this case, the negative frequency component of the next adjacent channel 61a is looped around 0 Hz and detected as a positive frequency. Therefore, the interference signal 62 corresponding to the next adjacent channel 61a is a signal having a frequency component from 0 Hz to 2.2 MHz.

  As described above, when the value of the intermediate frequency is reduced, the interference signal 62 and the like of the next adjacent channel 61a are turned back at 0 Hz. Depending on the value of the intermediate frequency, the folded interference signal 62 may overlap the reception channel 60. In this case, it is difficult to remove the interfering signal 62 using the band pass filter 23 or the like at the subsequent stage, and a communication error may occur.

  In the present embodiment, the absolute value of the intermediate frequency is set to be approximately 2.2 MHz to 2.8 MHz. That is, assuming that the intermediate frequency is Fi, the intermediate frequency Fi is set so as to satisfy −2.8 MHz ≦ Fi ≦ −2.2 MHz or 2.2 MHz ≦ Fi ≦ 2.8 MHz.

  For example, when the intermediate frequency is set to 2.2 MHz, the band of the reception channel 60 is 0 Hz to 4.4 MHz. The next adjacent channel 61a on the low frequency side is folded at 0 Hz, and its band does not overlap with the reception channel 60. As a result, the intermediate frequency can be reduced to the minimum frequency at which no aliasing occurs in the reception channel 60.

  Further, for example, when the intermediate frequency is set to 2.8 MHz, the upper limit frequency of the band of the reception channel 60 is 5 MHz. Further, the next adjacent channel 61a on the low frequency side is folded at 0 Hz, and the lower limit frequency of the band is 5 MHz. Therefore, the receiving channel 60 and the next adjacent channel 61a are in contact with each other at 5 MHz. Even in this case, the bands of the channels do not overlap.

  When the intermediate frequency is in the range from 2.2 MHz to 2.8 MHz, the next adjacent channel 61 a on the low frequency side does not overlap the reception channel 60. This makes it possible to sufficiently reduce the value of the intermediate frequency while avoiding the effects of image disturbance and the like. As a result, the configuration of the bandpass filter 23 can be greatly simplified, and the device can be sufficiently reduced in size.

  If the intermediate frequency is negative, the receiving channel 60 is turned around at 0 Hz. In this case, by setting the intermediate frequency to be -2.8 MHz or more and -2.2 MHz or less, the receiving channel 60 can be folded back so as not to overlap with the next adjacent channel 61b on the high frequency side. Thus, the configuration of the bandpass filter 23 can be greatly simplified.

  In the present embodiment, the absolute value of the intermediate frequency is set to approximately 2.5 MHz. That is, the first reference signal is set in accordance with the frequency of the reception channel 60 so that the value of the intermediate frequency is +2.5 MHz or -2.5 MHz. FIGS. 4B and 4C show the frequency relationship of each channel when the intermediate frequencies are +2.5 MHz and -2.5 MHz.

  For example, assume that the reception channel 60 is 5790 MHz. In this case, by setting the frequency of the first reference signal 41 to 5787.5 MHz, the intermediate frequency becomes 2.5 MHz. By setting the frequency of the first reference signal 41 to 5792.5 MHz, the intermediate frequency becomes -2.5 MHz. When another reception channel 60 is selected, the first reference signal 41 is appropriately set according to the frequency of the selected reception channel 60 so that the absolute value of the intermediate frequency is approximately 2.5 MHz. .

  As shown in FIG. 4B, when the reception channel 60 is converted to +2.5 MHz, the next adjacent channel 61a on the low frequency side is converted to -7.5 MHz. Accordingly, the next adjacent channel 61a on the low frequency side is turned back to a channel having a center frequency of +7.5 MHz. Accordingly, the orthogonal mixer 22 outputs a signal in which the frequency components of the receiving channel 60, the next adjacent channel 61a on the low frequency side, and the next adjacent channel 61b on the high frequency side are arranged in this order at an interval of 5 MHz.

  As shown in FIG. 4C, when the receiving channel 60 is converted to -2.5 MHz, the receiving channel 60 is folded back to a channel having a center frequency of 2.5 MHz. The next adjacent channel 61a on the low frequency side is looped back from -12.5 MHz to +12.5 MHz. Accordingly, the orthogonal mixer 22 outputs a signal in which the frequency components of the reception channel 60, the next adjacent channel 61b on the high frequency side, and the next adjacent channel 61a on the low frequency side are arranged in this order at an interval of 5 MHz.

  The first reference signal 41 for setting the absolute value of the intermediate frequency to approximately 2.5 MHz can be easily generated using, for example, a circuit for searching for a reception channel. As described above, the interval between channels for downlink communication is 5 MHz, and the circuit for searching for a reception channel changes the frequency in 5 MHz steps. For example, it is possible to easily change the step of the frequency to 2.5 MHz by using a dividing period or the like that divides the frequency by half, and it is possible to easily generate the first reference signal 41. It is.

  Thus, when the absolute value of the intermediate frequency is set to approximately 2.5 MHz, the first reference signal can be easily supplied. This makes it possible to easily realize a sufficiently low intermediate frequency while avoiding the effects of image disturbance and the like. As a result, it is possible to provide a small device with a small number of components.

  In the above, the intermediate frequency (IF) is set to a value smaller than the frequency difference between the first high-frequency signal 51 and the second high-frequency signal (frequency difference between the reception channel and the transmission channel). In the Low-IF method in which the intermediate frequency is set to a low value, for example, the number of frequency conversions up to demodulation can be reduced, and the number of components can be reduced.

  The present technology can be applied not only to the Low-IF system but also to the Zero-IF system. In the zero-IF method, an intermediate frequency is set to be substantially zero, and a direct conversion for directly demodulating a baseband signal from the first high-frequency signal 51 is executed. As shown in FIG. 5, by providing a low-pass filter (LPF: Low Pass Filter) 24 after the quadrature mixer 22, it is possible to execute communication in the zero-IF system.

  In the zero-IF method, the local oscillator 40 controls the frequency of the first reference signal 41 so that the intermediate frequency becomes substantially zero. For example, by setting the first reference signal 41 to a frequency substantially the same as that of the reception channel 60, it is possible to make the intermediate frequency substantially zero. When the wireless communication device 200 is in the reception state, the local oscillator 40 oscillates the first reference signal 41 having the same frequency as that of the reception channel 60. The oscillated first reference signal 41 is supplied to the quadrature mixer 22.

  The quadrature mixer 22 mixes the first high-frequency signal 51 with the first reference signal 41 having a frequency similar to that of the reception channel 60. As a result, the quadrature mixer 22 generates a signal including a frequency component corresponding to the difference and the sum of the same frequency (the frequency of the reception channel 60).

  The frequency difference between the first high-frequency signal 51 and the first reference signal 41 is approximately 0 Hz, and the frequency component corresponds to the component of the baseband signal. The sum of the frequencies is approximately twice the frequency of the receiving channel 60, and the frequency component becomes a high-frequency noise component. From the quadrature mixer 22, a signal including a baseband signal component and a high-frequency noise component is output to the low-pass filter 24.

  In the quadrature mixer 22, the baseband signal is demodulated by dividing it into an I signal 53 and a Q signal 54. As described above, the I signal 53 and the Q signal 54 are demodulated based on the reference I signal and the reference Q signal whose phases are orthogonal to each other. For this reason, it is possible to realize the demodulation of the baseband signal while avoiding the influence of the image disturbance or the like due to the return of the frequency. Thus, it can be said that the quadrature mixer 22 functions as an I / Q demodulator for demodulating an I / Q signal.

  The low-pass filter 24 is configured in an integrated circuit as an internal filter. The low-pass filter 24 passes frequency components in the second band including the intermediate frequency, and regulates frequency components higher than the upper limit frequency of the second band. The second band is, for example, a band from 0 Hz to an upper limit frequency. In the present embodiment, the low-pass filter 24 corresponds to a second internal filter.

  The upper limit frequency of the second band is set based on, for example, the frequency of a channel used in the DSRC scheme. For example, as described with reference to FIG. 2, in the DSRC system, the downlink communication channel of the pair A (5775 MHz) is the lowest frequency channel. For example, a frequency lower than the frequency of the downlink communication channel of pair A is set as the upper limit frequency.

  By setting the upper limit frequency lower than that of the lowest frequency channel of the DSRC system, it becomes possible to sufficiently attenuate the frequency components of each channel, noise signals having twice the frequency of each channel, and the like. This makes it possible to extract the baseband signal output from the quadrature mixer 22 with high accuracy. The method of setting the upper limit frequency and the like are not limited, and the upper limit frequency may be appropriately set according to, for example, a circuit configuration at the subsequent stage.

  The extracted baseband signal is directly converted into a digital signal, for example, and output to the controller. As described above, in the zero-IF method, by directly demodulating the baseband signal, it is possible to greatly reduce the number of components and the like used for frequency conversion and the like. This makes it possible to sufficiently reduce the size of the device.

  As described above, in the wireless communication device 100 according to the present embodiment, the first and second reference signals 41 and 42 having mutually different frequencies are appropriately switched and supplied to the receiving unit 20 and the transmitting unit 30. As a result, for example, the intermediate frequency can be controlled, and data can be received without using an external filter or the like. As a result, the size of the wireless communication device 100 can be reduced.

  FIG. 6 is a schematic diagram illustrating a configuration example of a wireless communication device 300 as a comparative example. As a communication method in the DSRC system, a method of operating each circuit on the transmission side and the reception side based on an LO oscillation signal having the same frequency is considered. In this method, the signal of the reception channel is converted to an intermediate frequency using the frequency used to generate the signal of the transmission channel. In the DSRC scheme, the frequency difference between the transmission channel and the reception channel is specified to be 40 MHz, and the intermediate frequency is 40 MHz.

  In the wireless communication apparatus 300, the local oscillator 340 outputs the LO oscillation signal 341 having the same frequency to the circuit on the receiving side (the receiving unit 320) and the circuit on the transmitting side (the transmitting unit 330). As shown in FIG. 6, in the receiving section 320, the mixer (mixer) 322 mixes the signal of the receiving channel output from the receiving amplifier 321 with the LO oscillation signal 341 to generate an IF signal 355 having an intermediate frequency of 40 MHz. Is output.

  When the intermediate frequency is 40 MHz, a filter having a steep bandpass characteristic is required to secure sufficient selectivity for the next adjacent channel separated by 10 MHz. Therefore, an external SAW (Surface Acoustic Wave) filter 323 shown in FIG. 6 is indispensable. Since the SAW filter 323 is provided outside, it becomes difficult to house, for example, a circuit on the receiving side on a chip. In addition, there is a problem that the whole circuit becomes large due to external wiring and securing of an installation position.

  In the wireless communication device 100 according to this embodiment, the local oscillator 40 oscillates the first and second reference signals 41 and 42 having different frequencies from each other in accordance with the communication state of the wireless communication device 100. In the receiving state, the first reference signal 41 is supplied to the receiving unit 20, and in the transmitting state, the second reference signal 42 is supplied to the transmitting unit 30. As described above, since the first and second reference signals 41 and 42 can be switched according to the communication state, it is possible to set the intermediate frequency to a desired value.

  The frequency of the first reference signal 41 is controlled such that the intermediate frequency is smaller than 40 MHz, which is the frequency difference between the first and second high-frequency signals 51 and 52. By setting the intermediate frequency low, an external filter such as a SAW filter becomes unnecessary. For this reason, wiring and installation surfaces for providing a SAW filter and the like are not required, and the size of the apparatus can be reduced while suppressing costs.

  Further, it becomes possible to configure the band-pass filter 23 for filtering the signal of the intermediate frequency as an internal filter in the integrated circuit. As a result, the receiving unit 20 can be housed in the chip, and the device can be sufficiently reduced in size.

  In the present embodiment, the intermediate frequency is set to approximately 2.5 MHz. As a result, it is possible to sufficiently avoid image disturbance or the like caused by frequency components such as the next adjacent channel in the DSRC system. As a result, for example, even when the image rejection ratio of the wireless communication device 100 is small, communication can be performed with high accuracy.

<Second embodiment>
A wireless communication device according to a second embodiment of the present technology will be described. In the following description, a description of portions similar to those of the configuration and operation of the wireless communication device 400 described in the above embodiment will be omitted or simplified.

  FIG. 7 is a schematic diagram illustrating a configuration example of a wireless communication device 400 according to the second embodiment. The wireless communication device 400 includes a communication unit 410, a reception unit 420, a transmission unit 430, a local oscillator 440, and a frequency divider 460. The communication unit 410 has, for example, the same configuration as the communication unit 410 shown in FIG.

  The receiving section 420 includes a receiving amplifier 421, a first mixer 422, a quadrature mixer 423, and a filter section 424. The receiving amplifier 421 has, for example, the same configuration as the receiving amplifier 21 of the receiving unit 20 shown in FIG. The receiving amplifier 421 functions as an LNA that amplifies the first high-frequency signal 451 including the frequency component of the receiving channel.

  The first mixer 422 mixes the first high-frequency signal 451 amplified by the receiving amplifier 421 with the first reference signal 441 supplied from the local oscillator 440. The quadrature mixer 423 mixes the signal output from the first mixer 422 and the first frequency-divided signal 461 supplied from the frequency divider 460. Thus, the first high-frequency signal 451 is frequency-converted in two stages by the first mixer 422 and the quadrature mixer 423.

  By the two frequency conversions, the frequency of the first high-frequency signal 451 is converted into four different frequencies. For example, if the frequencies of the first high-frequency signal 451 (reception channel), the first reference signal, and the first frequency-divided signal are fr, fs1, and fd1, respectively, the quadrature mixer 423 outputs fr + fs1 + fd1, and fr + fs1- Frequency components respectively corresponding to four frequencies of fd1, fr-fs1 + fd1, and fr-fs1-fd1 are output.

  Of these four frequencies, the lowest frequency (fr-fs1-fd1) is the intermediate frequency. As described above, in the present embodiment, the first mixer 422 and the quadrature mixer 423 convert the first high-frequency signal 451 into an intermediate frequency.

  The filter unit 424 extracts a frequency component of the intermediate frequency from the signal output from the quadrature mixer 423. The filter unit 424 is configured as, for example, a band-pass filter (BPF) in the Low-IF system, and is configured as a low-pass filter (LPF) in the Zero-IF system. The configuration and the like of the filter unit 424 are not limited, and may be appropriately configured using, for example, the band-pass filter 23 illustrated in FIG. 1 or the low-pass filter 24 illustrated in FIG.

  The transmission section 430 includes a modulation section 431, a second mixer 432, a band stop filter 433, and a transmission amplifier 434.

  The modulation section 431 mixes the baseband signal 458 with the second frequency-divided signal 462 supplied from the frequency divider 460. As a result, the baseband signal 458 is modulated into a signal having the same frequency as the second frequency-divided signal 462. The second mixer 432 mixes the signal output from the modulation unit 431 and the second reference signal 442 supplied from the local oscillator 440. As described above, the baseband signal 458 is frequency-converted in two stages by the modulator 431 and the second mixer 432.

  From the second mixer 432, a signal including a frequency component corresponding to the difference and sum of the frequency fd2 of the second frequency-divided signal 462 and the frequency fs2 of the second reference signal 442 is output. In the present embodiment, the sum (fd2 + fs2) of the frequencies of the second frequency-divided signal 462 and the second reference signal 442 becomes the frequency ft of the second high-frequency signal 452 (transmission channel). As described above, in the present embodiment, the modulation section 431 and the second mixer 432 perform the mixing of the second frequency-divided signal 462 with the baseband signal and the mixing of the second reference signal 442, and the second A high frequency signal 452 is generated.

  The band stop filter 433 regulates frequency components in the third band, and passes frequency components not included in the third band. The third band regulates a frequency component corresponding to a difference between the frequencies of the second frequency-divided signal 462 and the second reference signal 442 in the signal output from the second mixer 432, for example. It is set to pass the frequency component corresponding to the sum. Therefore, the frequency component of the second high-frequency signal 452 (transmission channel) passes through the band stop filter 433.

  The transmission amplifier 434 amplifies the second high-frequency signal 452 that has passed through the band stop filter 433. The transmission amplifier 434 has, for example, the same configuration as the transmission amplifier 32 of the transmission unit 30 shown in FIG. The transmission amplifier 434 functions as a PA that amplifies the second high-frequency signal 452 including the frequency component of the transmission channel.

  The local oscillator 440 oscillates by switching between the first reference signal 441 and the second reference signal 442 having a frequency different from that of the first reference signal 441 according to transmission and reception of radio waves of the DSRC method. The first and second reference signals 441 and 442 are supplied to first and second mixers 422 and 432, respectively. Further, the first and second reference signals 441 and 442 are branched at the branch point 445 and input to the frequency divider 460. As the local oscillator 440, a PLL circuit or the like that can switch between the first and second reference signals 441 and 442 and oscillate is used as appropriate.

  The frequency divider 460 divides the frequency of the signal (first and second reference signals 441 and 442) oscillated by the local oscillator 440 at a predetermined ratio. For example, the frequency divider 460 generates a first frequency-divided signal 461 by dividing the frequency of the first reference signal 441 at a predetermined rate. The frequency divider 460 divides the frequency of the second reference signal 442 at a predetermined ratio to generate a second frequency-divided signal 462. In the present embodiment, the frequency divider 460 corresponds to a frequency divider, and the second frequency-divided signal 462 corresponds to a frequency-divided signal. In the present embodiment, a supply unit is configured by the local oscillator 440 and the frequency divider 460.

  The predetermined ratio (frequency division ratio) for dividing the frequency is set to be one of ２, ４, and ６. By using such a simple frequency division ratio, the frequency divider 460 can be easily configured. In the example shown in FIG. 7, a frequency divider 460 having a frequency division ratio of 1/4 is used. For example, when a 5800 MHz signal is input to the frequency divider 460, a signal having a frequency of 5800/4 = 1450 MHz is output from the frequency divider 460.

  It is assumed that a reception channel and a transmission channel are set, and communication between wireless communication apparatus 400 and a base station is performed. Hereinafter, the operation of wireless communication apparatus 400 in uplink communication (transmission state) and downlink communication (reception state) will be described.

  In the transmission state, the second reference signal 442 is oscillated by the local oscillator 440. In FIG. 7, the frequency fs2 of the second reference signal 442 is set to be 4/5 of the frequency ft of the transmission channel. The frequency divider 460 divides the frequency fs2 of the second reference signal 442 input via the branch point 445 by １ ／, and generates the second divided signal 462. The frequency fd2 of the second frequency-divided signal 462 is fd2 = (fs2) / 4 = (ft × 4/5) / 4 = ft / 5.

  The modulator 431 mixes the baseband signal and the second frequency-divided signal 462. A baseband signal modulated to a frequency of ft / 5 is output from the modulator 431 and input to the second mixer 432. The second mixer 432 mixes the signal output from the modulation unit 431 and the second reference signal 442 input via the branch point 445. In the second mixer 432, the frequency of each signal is added (ft / 5 + ft × 4/5 = ft) and subtracted (| ft / 5−ft × 4/5 | = ft × 3/5).

  Therefore, the second mixer 432 outputs a second high-frequency signal 452 having the same frequency ft as the transmission channel and a signal having a frequency of ft × 3/5. The band-stop filter 433 extracts the second high-frequency signal 452 from the output of the second mixer 432. Then, the second high-frequency signal 452 is amplified by the transmission amplifier 434 and transmitted to the communication unit 410.

  As described above, radio communication apparatus 400 shown in FIG. 7 sets the frequency of second reference signal 442 to ／ of the frequency of the transmission channel so that the baseband signal is modulated to the frequency of the transmission channel. Is configured. That is, in the wireless communication device 400, the ratio between the oscillation frequency (LO frequency) of the local oscillator 440 and the frequency of the transmission channel (transmission frequency) is 4: 5.

  Since the transmission frequency is different from the LO oscillation frequency, it is possible to sufficiently reduce the influence of local pulling and the like on the local oscillator 440 from the transmission amplifier 434, which is a power amplifier, for example. As a result, the local oscillator 440 can be operated stably, and communication errors, device failures, and the like can be suppressed to a sufficient extent.

  Since the transmission channels are at intervals of 5 MHz, when changing the channel, the frequency of the second reference signal 442 may be changed in steps of 5 MHz × 4/5 = 4 MHz. This makes it possible to simplify the circuit configuration and the like for generating the second reference signal 442. As a result, it is possible to reduce the number of parts, to reduce the cost of parts, and to realize a small and highly reliable device.

  In the receiving state, the first reference signal 441 is oscillated by the local oscillator 440. The frequency fs1 of the first reference signal 441 is set in accordance with the frequency fr of the reception channel (the first high-frequency signal 451) such that the intermediate frequency fi has a predetermined value. The first reference signal 441 and the first frequency-divided signal 461 generated by dividing the frequency of the first reference signal 441 are supplied to the receiving unit 420, and the first high-frequency signal 451 is converted into the intermediate frequency fi. .

  In FIG. 7, the frequency fd1 of the first frequency-divided signal 461 is １ ／ of the frequency fs1 of the first reference signal 441. As described above, the intermediate frequency fi is expressed as fr-fs1-fd1. Therefore, the intermediate frequency fi is fi = fr-fs1-fs1 / 4 = fr-fs1 * 5/4.

  For example, in the zero-IF method, the frequency fs1 of the first reference signal 441 is set so that the intermediate frequency fi ≒ 0 Hz. In this case, by setting the frequency fs1 of the first reference signal 441 to 4/5 of the frequency fr of the reception channel, it is possible to make the intermediate frequency fi approximately zero. To change the channel, the first reference signal may be changed in steps of 4 MHz.

  Further, for example, in the Low-IF system, the first reference signal 441 can be set so that the intermediate frequency becomes fi と 2.5 MHz. In this case, by setting fs1 = fr × 4 / 5-2 MHz, the intermediate frequency fi can be set to approximately 2.5 MHz. That is, by creating a frequency shifted by 2 MHz from the frequency of the zero-IF method, it is possible to easily realize the Low-IF method with the intermediate frequency of 2.5 MHz.

  As described above, the signals (the first and second reference signals 441 and 442) oscillated by the local oscillator 440 and the signals obtained by dividing the signals (the first and second divided signals 461 and 462) are used. Thus, the frequency conversion can be performed in two stages. By using such a sliding IF method for performing a plurality of frequency conversions, it is possible to easily realize a circuit configuration in which the influence of, for example, local pulling is sufficiently reduced.

  Note that, even when the frequency division ratio set in the frequency divider 460 is set to 1/2 or 1/6, the frequency of the first and second reference signals 441 and 442 can be appropriately set. It is possible to configure the wireless communication device 400. Of course, the frequency division ratio set in the frequency divider 460 is not used, and for example, any frequency division ratio other than 1/2, 1/4, and 1/6 may be used. In addition, the present technology is not limited to performing two-stage frequency conversion, but is also applicable to performing three-stage or four-stage frequency conversion. In this case, by performing frequency conversion a plurality of times, it is possible to sufficiently suppress the influence of frequency coupling (local coupling) on the local oscillator 440.

<Third embodiment>
FIG. 8 is a schematic diagram illustrating a configuration example of a wireless communication device 500 according to the third embodiment. The wireless communication device 500 includes a communication unit 510, a signal generator 570, and a system clock generator 580. The communication unit 510 has substantially the same configuration as each wireless communication device described in the above embodiment. FIG. 8 shows the configuration shown in FIG. 1, but the configurations shown in FIGS. 5 and 7 may be used.

  The signal generation unit 570 is a circuit provided at a subsequent stage of the reception unit 520 of the communication unit 510, and generates the data signal 550 based on the intermediate frequency signal. As illustrated in FIG. 8, the signal generation unit 570 includes a digital conversion unit 571, a digital signal processing unit 572, an analog conversion unit 573, and a quadrature mixer 574.

  The digital conversion unit 571 converts the I / Q signal 555, which is an intermediate frequency signal output from the reception unit 520, into a digital signal. As shown in FIG. 8, the I / Q signal 555 is a signal including the I signal 553 and the Q signal 554. The digital conversion unit 571 converts each of the I signal 553 and the Q signal 554 into a digital signal. Hereinafter, processing performed on each of the I signal 553 and the Q signal 554 may be described as processing on the I / Q signal 555.

  As the digital converter 571, for example, an ADC (Analog-to-Digital Converter) or the like is used. The specific configuration of the digital conversion unit 571 is not limited. For example, an arbitrary digital conversion circuit or the like that can digitally sample a baseband signal may be appropriately used.

  The digital signal processing unit 572 processes the I / Q signal 555 in the digital domain. As shown in FIG. 8, the digital signal processing unit 572 includes a channel selection filter 575, a level detection unit 576, and a frequency conversion unit 577.

  The channel selection filter 575 filters the I / Q signal 555 converted into a digital signal. The channel selection filter 575 removes noise components and the like that could not be completely removed by, for example, an analog filter (BPF or LPF) of the reception unit 520. Thereby, it is possible to extract the frequency component included in the reception channel converted into the intermediate frequency with high accuracy, and it is possible to remove the components of other channels with high accuracy.

  Level detection section 576 detects the amplitude intensity of I / Q signal 555 output from channel selection filter 575. For example, by detecting a time change of the amplitude of the I / Q signal 555, it is possible to detect a signal modulated by the ASK method. For example, the level detection unit 576 converts the amplitude intensity of the I / Q signal 555 into bits and outputs the bits as an ASK detection output 556. In the present embodiment, the ASK detection output 556 corresponds to an ASK signal.

  Further, for example, it is possible to determine whether or not a carrier exists at a target frequency (channel) based on the amplitude intensity of the I / Q signal 555. For example, when the amplitude intensity is smaller than a predetermined threshold, it is determined that no carrier exists, and when it is larger than the predetermined threshold, it is determined that a carrier exists. The determination result is output as a carrier detection output 557, and is used for selecting a reception channel. In the present embodiment, the carrier detection output 557 corresponds to a carrier intensity signal.

  The frequency conversion unit 577 converts the frequency of the I / Q signal 555 output from the channel selection filter 575 to approximately 0 Hz by performing frequency conversion in the digital domain. This can be said that the I / Q signal is converted to a baseband signal in the digital domain. This makes it possible to correct, for example, a deviation of the LO reference clock signal between the base station and the wireless communication device 500. The I / Q signal 555 frequency-converted to approximately 0 Hz is output to the analog conversion unit 573.

  As described above, the digital signal processing unit 572 performs various digital processes on the I / Q signal 555. As the digital signal processing unit, for example, a DSP (Digital Signal Processor) in which digital signal filtering processing or the like is programmed is used. In addition, the specific configuration of the digital signal processing unit 572 is not limited. Further, the channel selection filter 575, the level detection unit 576, and the frequency conversion unit 577 may be configured by individual elements.

  The analog converter 573 converts the I / Q signal 555 output from the frequency converter 577 into an analog signal. As the analog conversion unit 573, for example, a DAC (Digital-to-Analog Converter) or the like is used. The specific configuration of the analog conversion unit 573 is not limited.

  In the present embodiment, the digital conversion unit 571, the digital signal processing unit 572, and the analog conversion unit 573 constitute a digital filter unit that digitizes and filters an intermediate frequency signal.

  The quadrature mixer 574 mixes the I / Q signal 555 converted into an analog signal with the reference signal 581 having a demodulation frequency output from the system clock generator 580. As the demodulation frequency, a frequency (8.192 MHz) based on a system reference clock signal 582 used in a subsequent signal processing circuit (controller or the like) is set.

  The quadrature mixer 574 converts the I signal 553 and the Q signal 554 (I / Q signal 555) into demodulation frequencies, respectively. The converted I signal 553 and Q signal 554 are added using an adder circuit or the like, and output as an output 558 for QPSK. In the present embodiment, the quadrature mixer 574 corresponds to a mixer that converts the output of the digital filter into a frequency for demodulation. In the present embodiment, the output 558 for QPSK corresponds to a QPSK signal.

  The system clock generator 580 generates a system clock signal 583 input to a signal processing circuit or the like and a demodulation reference signal 581 based on the system reference clock signal 582. Note that the frequencies of the system clock signal 583 and the reference signal 581 may be the same or different from each other. As the system clock generation unit 580, for example, a PLL circuit prepared for signal processing is used.

  As shown in FIG. 8, the system clock signal 583 is output to a signal processing circuit such as a digital conversion unit 571, a digital signal processing unit 572, an analog conversion unit 573, and a subsequent controller. The demodulation reference signal 581 is output to the quadrature mixer 574. Thus, each unit included in signal generation unit 570 operates based on system reference clock signal 582. In the present embodiment, the system reference clock signal 582 corresponds to a reference clock signal.

  For example, it is assumed that the wireless communication device 500 is searching for a reception channel. In this case, the I / Q signals 555 corresponding to, for example, seven downlink communication channels (see FIG. 2) are sequentially output from the receiving unit 520. The signal generation unit 570 performs digital domain filtering on each I / Q signal 555, and outputs a carrier detection output 557 based on the amplitude intensity of the I / Q signal 555. This makes it possible to select a channel (reception channel) used by the base station for transmission from the seven channels.

  Further, for example, when wireless communication apparatus 500 is in a receiving state, receiving section 520 outputs an I / Q signal 555 corresponding to the receiving channel. The signal generation unit 570 performs digital domain filtering on the I / Q signal 555 of the reception channel, and outputs an ASK detection output 556 based on the amplitude intensity of the I / Q signal 555. In addition, the signal generation unit 570 performs frequency conversion in the digital domain and the analog domain on the filtered I / Q signal 555, and outputs the result as a QPSK output 558.

  As described above, the signal generator 570 generates the data signal 550 including the QPSK output 558, the ASK detection output 556, and the carrier detection output 557 based on the intermediate frequency signal. This makes it possible to generate a data signal in accordance with, for example, a subsequent circuit (controller) that performs data processing and the like, and high versatility is exhibited.

  For example, in the wireless communication device 300 listed as a comparative example in FIG. 6, a QPSK output 358, an ASK detection output 356, and a carrier detection output 357 are generated based on a signal converted to an intermediate frequency of 40 MHz. In radio communication apparatus 300 shown in FIG. 6, in order to generate QPSK output 358, a dedicated reference signal 381 for performing frequency conversion from 40 MHz to 8.192 MHz is required. Therefore, in FIG. 6, a dedicated oscillation circuit 384 including a crystal oscillator 382 and a PLL circuit 383 is required.

  In the wireless communication apparatus 500 according to the present embodiment, the reference signal 581 for converting to a demodulation frequency (8.192 MHz) is generated by a system clock generation unit 580 that oscillates a system clock used by a controller or the like. . Therefore, a dedicated oscillation circuit or the like for converting the I / Q signal 555 to a frequency for demodulation is not required, and the number of components can be reduced. This makes it possible to sufficiently reduce the size of the device.

  The wireless communication device 500 can output the same data signal 550 as the wireless communication device 300 illustrated in FIG. From another viewpoint, a signal processing circuit (controller or the like) used in a subsequent stage of the wireless communication device 300 shown in FIG. 6 can be used as a subsequent stage of the wireless communication device 500 according to the present embodiment. It can also be said. As described above, by applying the present technology, it is possible to provide the wireless communication device 500 having a small device size and high versatility.

  In the present embodiment, the I / Q signal 555 is filtered in the digital domain by the signal generator 570. Therefore, in the wireless communication device 500, the I / Q signal 555 is filtered in two stages by the analog filter (LPF or BPF) of the receiving unit 20 and the digital filter of the signal generating unit. This makes it possible to generate the data signal 550 such as the QPSK output 558 and the ASK detection output 556 with high accuracy, and it is possible to greatly improve the communication accuracy.

<Other embodiments>
The present technology is not limited to the embodiments described above, and can realize other various embodiments.

  In radio communication apparatus 500 shown in FIG. 8, an I / Q signal having an intermediate frequency is converted into a demodulation frequency in order to execute QPSK demodulation. For example, an I / Q signal having a frequency for demodulation may be directly generated by the quadrature mixer of the receiving unit. That is, the intermediate frequency may be set to 8.192 MHz. In this case, the frequency conversion required until the demodulation process is performed once, and the number of components and the like can be reduced. The present invention is not limited to this, and the value of the intermediate frequency may be appropriately set according to the processing in the subsequent stage.

  In the above embodiment, the wireless communication devices 100, 200, 400, and 500 are configured as on-vehicle devices that are mobile stations. The present technology is not limited to this, and the present technology is applicable even when the wireless communication device is configured as a base station.

  For example, the value of the intermediate frequency can be controlled by appropriately switching the oscillation frequency of the local oscillator according to the transmission state and the reception state of the base station. As a result, the device can be configured without using an external filter or the like, and the size of the device can be reduced. In addition, the wireless communication device according to the present technology is not limited to a vehicle-mounted device mounted on a vehicle or the like, and may be configured as a device such as a mobile device or a wearable device.

  Among the characteristic parts according to the present technology described above, it is also possible to combine at least two characteristic parts. That is, various features described in each embodiment may be arbitrarily combined without distinction of each embodiment. Further, the various effects described above are only examples and are not limited, and other effects may be exhibited.

Note that the present technology can also adopt the following configurations.
(1) a communication unit capable of transmitting and receiving radio waves for short-range communication;
A conversion unit configured to convert a reception signal generated in response to reception of the radio wave for short-range communication to an intermediate frequency based on a first reference signal;
A generating unit configured to generate a transmission signal used for transmitting the radio waves for the short-range communication based on a second reference signal having a frequency different from the first reference signal;
A supply unit configured to switch between supply of the first reference signal to the conversion unit and supply of the second reference signal to the generation unit.
(2) The wireless communication device according to (1),
The conversion unit converts the received signal to the intermediate frequency by mixing the first reference signal and the received signal,
The wireless communication device, wherein the supply unit controls a frequency of the first reference signal such that the intermediate frequency is smaller than a frequency difference between the reception signal and the transmission signal.
(3) The wireless communication device according to (1) or (2),
The wireless communication device includes a first internal filter that passes a frequency component of a first band including the intermediate frequency and regulates a frequency component not included in the first band.
(4) The wireless communication device according to any one of (1) to (3),
The wireless communication device, wherein the intermediate frequency has an absolute value of 2.2 MHz or more and 2.8 MHz or less.
(5) The wireless communication device according to any one of (1) to (4),
The wireless communication device, wherein the intermediate frequency has an absolute value of approximately 2.5 MHz.
(6) The wireless communication device according to (1) or (2),
The wireless communication device, wherein the supply unit controls a frequency of the first reference signal so that the intermediate frequency becomes substantially zero.
(7) The wireless communication device according to (6),
The wireless communication device includes a second internal filter configured to pass a frequency component of a second band including the intermediate frequency and to regulate a frequency component higher than an upper limit frequency of the second band.
(8) The wireless communication device according to any one of (1) to (7),
The wireless communication device includes a phase synchronization circuit that switches between the first and second reference signals and oscillates.
(9) The wireless communication device according to any one of (1) to (8),
The supply unit has a frequency divider that divides the frequency of the second reference signal at a predetermined rate to generate a frequency-divided signal,
The wireless communication device that generates the transmission signal by performing mixing of the frequency-divided signal with a baseband signal and mixing of a second reference signal.
(10) The wireless communication device according to (9),
The wireless communication device, wherein the predetermined ratio is one of 、, ４, and ６.
(11) The wireless communication device according to any one of (1) to (10), further comprising:
A wireless communication device comprising: a signal generation unit that generates a data signal based on the intermediate frequency signal.
(12) The wireless communication device according to (11),
The wireless communication device, wherein the data signal includes at least one of a QPSK signal, an ASK signal, and a carrier intensity signal.
(13) The wireless communication device according to (11) or (12),
The wireless communication device includes a digital filter unit that digitizes and filters the signal of the intermediate frequency, and a mixer unit that converts an output of the digital filter to a frequency for demodulation.
(14) The wireless communication device according to (13),
The wireless communication device, wherein the digital filter unit and the mixer unit operate based on a reference clock signal.
(15) The wireless communication device according to any one of (1) to (14),
The wireless communication device, wherein the reception signal is a signal having a lower frequency than the transmission signal.
(16) The wireless communication device according to (15),
A wireless communication device configured as an onboard device.

fi: Intermediate frequency 10: Communication unit 100, 200, 400, 500: Wireless communication device 20, 420, 520: Receiving unit 22, 423: Quadrature mixer 23: Bandpass filter 24: Low-pass filter 30, 430: Transmitting unit 31, 431: Modulating unit 40, 440: Local oscillator 41, 441: First reference signal 42, 442: Second reference signal 51, 451: First high-frequency signal 52, 452: Second high-frequency signal 458: Baseband Signal 462: second frequency-divided signal 550: data signal 556: ASK detection output 557: carrier detection output 558: output for QPSK 570: signal generator 574: quadrature mixer 582: system reference clock signal

Claims (17)

A communication unit capable of transmitting and receiving radio waves for short-range communication,
A conversion unit configured to convert a reception signal generated in response to reception of the radio wave for short-range communication to an intermediate frequency based on a first reference signal;
A generating unit configured to generate a transmission signal used for transmitting the radio waves for the short-range communication based on a second reference signal having a frequency different from the first reference signal;
A supply unit configured to switch between supply of the first reference signal to the conversion unit and supply of the second reference signal to the generation unit. The wireless communication device according to claim 1,
The conversion unit converts the received signal to the intermediate frequency by mixing the first reference signal and the received signal,
The wireless communication device, wherein the supply unit controls a frequency of the first reference signal such that the intermediate frequency is smaller than a frequency difference between the reception signal and the transmission signal. The wireless communication device according to claim 1,
The wireless communication device includes a first internal filter that passes a frequency component of a first band including the intermediate frequency and regulates a frequency component not included in the first band. The wireless communication device according to claim 1,
The wireless communication device, wherein the intermediate frequency has an absolute value of 2.2 MHz or more and 2.8 MHz or less. The wireless communication device according to claim 1,
The wireless communication device, wherein the intermediate frequency has an absolute value of approximately 2.5 MHz. The wireless communication device according to claim 1,
The wireless communication device, wherein the supply unit controls a frequency of the first reference signal so that the intermediate frequency becomes substantially zero. The wireless communication device according to claim 6,
The wireless communication device includes a second internal filter configured to pass a frequency component of a second band including the intermediate frequency and to regulate a frequency component higher than an upper limit frequency of the second band. The wireless communication device according to claim 1,
The wireless communication device includes a phase synchronization circuit that switches between the first and second reference signals and oscillates. The wireless communication device according to claim 1,
The supply unit has a frequency divider that divides the frequency of the second reference signal at a predetermined rate to generate a frequency-divided signal,
The wireless communication device that generates the transmission signal by performing mixing of the frequency-divided signal with a baseband signal and mixing of a second reference signal. The wireless communication device according to claim 9,
The wireless communication device, wherein the predetermined ratio is one of 、, ４, and ６. The wireless communication device according to claim 1, further comprising:
A wireless communication device comprising: a signal generation unit that generates a data signal based on the intermediate frequency signal. The wireless communication device according to claim 11,
The wireless communication device, wherein the data signal includes at least one of a QPSK signal, an ASK signal, and a carrier intensity signal. The wireless communication device according to claim 11,
The wireless communication device includes a digital filter unit that digitizes and filters the signal of the intermediate frequency, and a mixer unit that converts an output of the digital filter to a frequency for demodulation. The wireless communication device according to claim 13,
The wireless communication device, wherein the digital filter unit and the mixer unit operate based on a reference clock signal. The wireless communication device according to claim 1,
The wireless communication device, wherein the reception signal is a signal having a lower frequency than the transmission signal. The wireless communication device according to claim 15, wherein
A wireless communication device configured as an onboard device. Sends and receives radio waves for short-range communication,
Converting a reception signal generated in response to reception of the radio wave for the short-range communication into an intermediate frequency based on the first reference signal;
Based on a second reference signal having a different frequency from the first reference signal, generating a transmission signal used for transmitting the radio wave for the short-range communication,
A wireless communication method for switching between supply of the first reference signal and supply of the second reference signal.

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