JP2024002810A - signal processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a signal processing device used in a wireless terminal or the like to correctly detect a signal of each frequency from a communication signal including signals of a plurality of frequencies with a simple configuration.

SOLUTION: A signal processing device 44 includes: a first detection unit 4421 that detects a communication signal including signals of a plurality of frequencies; and a second detection unit 4422 that detects the communication signal from which a first signal of a first frequency has been removed with a polarity opposite to that of the first detection unit 4421. The signal processing device combines and outputs a detection output of the first detection unit 4421 and a detection output of the second detection unit 4422.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a wireless terminal mounted on, for example, a vehicle and its component parts.

For example, in V2X (Vehicle to Everything) services, the functionality of wireless terminals (antennas, communication devices, and their component parts) installed in vehicles is increasing. Among V2X services, services using the 5.9 GHz band are leading the way, but services using the 26 GHz band, 28 GHz band, and 60 GHz band are also being considered in the future.
As a prior art related to V2X services, there is a technology disclosed in Patent Document 1, for example. With this technology, a wireless communication base station performs provisioning for V2X services, that is, predicts the provision of resources such as networks and equipment at the required timing to vehicle-side wireless terminals using V2X services. , be prepared. That is, when the base station broadcasts V2X support information, the vehicle-side wireless terminal that receives it transmits V2X terminal information. Upon receiving the V2X terminal information, the base station allocates resources for the V2X service for the vehicle-side wireless terminal. Since the vehicle is moving, the vehicle-side wireless terminal needs to correctly receive the V2X support information and quickly transmit the V2X terminal information.

Japanese Patent Application Publication No. 2021-168495

2. Description of the Related Art Wireless terminals on mobile bodies such as vehicles usually have limited locations and spaces in which to install them. Therefore, wireless terminals often share one or more antennas with in-vehicle communication equipment that uses communication signals of multiple frequencies. Wireless terminals also make it possible to switch between transmitting and receiving communication signals, modulating multiple signals and superimposing them on the signal line when transmitting, and demultiplexing each modulated wave from the signal line when receiving. Detection of the signals is also being carried out. As for the communication method, a serial communication method is also adopted when it is necessary to avoid an increase in the number of circuit components. In recent years, digital signals are often used in in-vehicle communication equipment, and in this case, a wireless terminal connected to the in-vehicle communication equipment is provided with means for converting a detected signal into a digital signal upon reception.

One of the problems when a signal line is shared by multiple communication signals in a wireless terminal on the side of a mobile object such as a vehicle is that unexpected erroneous detection of the communication signal is likely to occur on the receiving side, and it is necessary to avoid this. Therefore, the circuit configuration cannot be simplified. For example, when multiple modulated waves received using a serial communication method are demultiplexed and each demultiplexed signal is directly detected, the waveform of the demultiplexed signal is disturbed and the original signal is likely to be erroneously detected (false detection). Erroneous detection of a demultiplexed signal (erroneous detection wave) causes malfunctions in in-vehicle communication equipment that uses the original signal.

In particular, in high frequency bands such as those used in V2X services, unintended signals including radiation noise at frequencies other than those designed for are likely to mix into the signal line. Therefore, it is difficult to share one signal line or electronic circuit for communication signals of multiple frequencies in high frequency bands such as those used in V2X services. In such high frequency bands, it is common to create circuit boards according to the number of communication signals to be used, and to install narrowband matching circuits, load fluctuation suppression circuits, etc. on the signal lines formed on each circuit board. It is. Therefore, not only the cost of circuit design increases, but also the circuit area cannot be reduced.

One of the objects of the present invention is to provide a component of a wireless terminal that can correctly detect signals of each frequency from a communication signal including signals of multiple frequencies with a simple configuration. Other objects of the present invention will become apparent from the description of this specification.

One aspect of the present invention includes a first detection unit that detects a communication signal including signals of multiple frequencies, and a first detection unit that detects the communication signal from which the first signal of the first frequency is removed, and detects the communication signal with a polarity opposite to that of the first detection unit. and a second detection section that performs wave detection, and is a signal processing device that combines and outputs the detection output of the first detection section and the detection output of the second detection section.
According to this signal processing device, a signal of each frequency, for example, a first signal of a first frequency, can be correctly detected from a communication signal including signals of multiple frequencies with a simple configuration.

FIG. 1 is a configuration diagram of a wireless terminal according to the present embodiment. FIG. 2 is a configuration diagram of a signal processing device included in a wireless terminal. FIG. 3 is a diagram showing an example of waveforms of a pulse signal in which a transient response occurs and a digital signal after A/D conversion. It is a figure showing the example of composition of a demultiplexing part. FIG. 3 is a diagram illustrating an example of a signal transmitted through the _f1 route. It is a figure showing the example of composition of a detection part. FIG. 6 is a diagram showing a difference in the signal level of a non-target signal depending on the presence or absence of a load resistor. FIG. 7 is a diagram showing a difference in polarity of an unintended signal depending on the presence or absence of a load resistor. It is a figure which shows the example of a waveform of _f1 detection signal. It is a figure which shows the example of a waveform of an _f2 detection signal. FIG. 1 is a configuration diagram showing an embodiment of the present invention.

Hereinafter, an embodiment in which the present invention is applied to a wireless terminal attached to a vehicle will be described. FIG. 1 is a configuration diagram of a wireless terminal 1 according to this embodiment. The wireless terminal 1 is a communication device that includes an ECU (Electronic Control Unit) 2 and a bidirectional amplifier 4 connected to an antenna 3. The ECU 2 is a control unit that controls the in-vehicle communication network and/or the drive control of the vehicle. The antenna 3 is an antenna that enables communication for performing V2X services (hereinafter referred to as "V2X communication") with an external communication system. Bidirectional amplifier 4 is housed in a separate housing from ECU 2 and antenna 3. The housing is provided with a unit terminal 11 for connecting to the ECU 2 and an antenna terminal 12 for connecting to the antenna 3. The ECU 2 and the unit terminal 11, and the antenna 3 and the antenna terminal 12 are each connected via an RF (Radio Frequency) cable, such as a coaxial cable.

The bidirectional amplifier 4 includes a FEM (Front End Module) 41, an MCU (Micro Controller Unit) 42, a power supply circuit (P.S.) 43, and a signal processing device 44. The FEM 41 is responsible for RF processing using various information exchanged between the antenna 3 and the ECU 2 through communication signals. The FEM 41 is configured by modularizing, for example, a tuner, a transmission/reception changeover switch, a duplexer, a power amplifier that functions during transmission, a low noise amplifier that functions during reception, and the like. The MCU 42 is one of the control means that controls the FEM 41 and the signal processing device 44 to perform predetermined operations. The MCU 42 transmits information addressed to the ECU 2 from the FEM 41 to the signal processing device 44. The MCU 42 also transmits information addressed to the FEM 41 from the ECU 2 to the signal processing device 44.

A signal line between the ECU 2, the unit terminal 11, the core wire of the RF cable, and the FEM 41 is referred to as a main signal line 401 in this specification. A cut capacitor C ₀ is inserted in the main signal line 401 to cut the DC component. A signal processing device 44 is also connected to the main signal line 401 . A power supply circuit (P.S.) 43 is also connected to the main signal line 401 via an RF cut inductor _L0 that cuts RF components. The power supply circuit (P.S.) 43 converts the power supplied from the ECU 2 into power for driving the bidirectional amplifier 4. Therefore, the power supplied from the ECU 2 and the RF communication signal are superimposed on the main signal line 401. Note that the power supply circuit (P.S.) 43 may be configured to directly supply power from the ECU 2 to the FEM 41, MCU 42, and signal processing device 44 without conversion.

The signal processing device 44 transmits the following three communication signals using a serial communication method.
・Tx/Rx signal from ECU2 to FEM41 ・CONTROL signal from ECU2 to FEM41 ・LOG signal from FEM41 to ECU2

The Tx/Rx signal is a single pulse signal used for switching control of uplink/downlink (transmission system/reception system) in V2X communication, Cal response of the MCU 42 (response for establishing a communication channel), and the like. The pulse width of this single pulse signal is several μSec to several mSec. Since the Tx/Rx signal has the above-mentioned role, it is an important signal that cannot be subjected to unnecessary delay or false detection. For the Tx/Rx signal, the ECU 2 modulates a subcarrier wave of a first frequency f ₁ lower than that of the RF signal using a predetermined modulation method, and transmits the modulated signal to the signal processing device 44 . The signal processing device 44 detects this modulated wave, demodulates the Tx/Rx signal, and transmits it to the MCU 42. The MCU 42 controls the FEM 41 using Tx/Rx signals.
In the following description, the modulated Tx/Rx signal may be referred to as an " _f1 modulated wave", and the signal obtained by detecting the _f1 modulated wave may be referred to as an " _f1 detected signal".

The CONTROL signal is a data string (pulse string representing information in a combination of pulses) signal for changing the settings of the FEM 41 through the MCU 42. This data string signal is carried by modulating a carrier wave of a second frequency _f2 using a predetermined modulation method. The CONTROL signal is output by the ECU 2. That is, the ECU 2 modulates the subcarrier wave of the second frequency f ₂ lower than the RF signal using a predetermined modulation method, and transmits the modulated subcarrier wave to the signal processing device 44 . The signal processing device 44 detects this modulated wave, demodulates the CONTROL signal, and transmits it to the MCU 42. The MCU 42 changes the settings of the FEM 41 using the CONTROL signal.
In the following description, the modulated CONTROL signal may be referred to as an " _f2 modulated wave", and the signal obtained by detecting the _f2 modulated wave may be referred to as an " _f2 detected signal".

The LOG signal is a data string signal representing feedback information such as transmission power, temperature, keep-alive response (periodic response to prevent communication connection disconnection), and the like. After receiving the CONTROL signal, MCU 42 transmits a LOG signal to signal processing device 44 . The signal processing device 44 modulates this LOG signal with a subcarrier wave having a third frequency _f3 lower than that of the RF signal using a predetermined modulation method, and transmits the modulated signal to the ECU 2. In this way, the CONTROL signal and LOG signal are separated in time and do not overlap.
In the following description, the modulated LOG signal may be referred to as an " _f3 modulated wave", and the signal obtained by detecting the _f3 modulated wave may be referred to as an " _f3 detected signal".

The first frequency _f1 needs to have a delay as small as possible in order to control the transmission/reception system switching at high speed using the Tx/Rx signal. Therefore, frequencies as high as possible are used. On the other hand, the second frequency _f2 and the third frequency _f3 are set to frequencies lower than the first frequency _f1 . The frequencies f ₁ , f ₂ , and f ₃ are typically three different frequencies, but may be two frequencies in which the second frequency f ₂ and the third frequency f ₃ are the same frequency. By using two frequencies, the circuit configuration can be simplified and costs can be reduced.
The frequency condition of the carrier wave of each signal is one of the following.
f ₂ < f ₃ < f ₁
f ₃ < f ₂ < f ₁
f ₂ = f ₃ < f ₁
In the following description, it is assumed that the RF signal is 5.9 GHz and the first frequency f ₁ is one of 64 to 128 MHz, for example 125 MHz. Further, it is assumed that the second frequency f ₂ and the third frequency f ₃ are any one of 4 MHz to 32 MHz, for example, 16 MHz. That is, in this embodiment, first, an example in which there are two frequencies will be described.

The Tx/Rx signal reaches the main signal line 401 of the bidirectional amplifier 4 from the ECU 2 as an f ₁ modulated wave, and the CONTROL signal as an f ₂ modulated wave. The LOG signal reaches the main signal line 401 as an f ₃ modulated wave modulated by the bidirectional amplifier 4 . The modulation method only needs to be common between the ECU 2 and the bidirectional amplifier 4, and any modulation method such as ASK (Amplitude Shift Keying), PWM (Pulse Width Modulation), etc. can be adopted.
In this embodiment, an example will be described in which ASK-OOK (on-off-keying) is adopted. ASK-OOK is a method that modulates by "signal output/no output" within ASK, and has the advantage that detection (demodulation) only requires the presence or absence of a signal, and can be realized with a simple circuit configuration.

The signal processing device 44 will be explained in detail. FIG. 2 is a diagram showing an example of the configuration of the signal processing device 44. The signal processing device 44 includes a demultiplexing section 441, a detection section 442, an A/D conversion section 443, and a modulation section 444. However, if the MCU 42 has a modulation function, the modulation section 444 becomes unnecessary.

The demultiplexer 441 demultiplexes the _f1 modulated wave, the _f2 modulated wave, and the _f3 modulated wave. If the demultiplexing is not sufficient, the waveform of the detected signal in the detection section 442 at the subsequent stage will be disturbed, and the output signal from the A/D conversion section 443 at the subsequent stage will become the source signal (Tx/Rx signal, CONTROL signal). The content may differ from the actual content. This will be explained with reference to FIG.

FIG. 3 is a diagram showing an example of waveforms of a pulse signal in which a transient response occurs and a digital signal after A/D conversion. In FIG. 3, the vertical axis is DC voltage (V), and the horizontal axis is time (T).
In the case of a pulse signal, since the signal level changes rapidly from a steady state, transient responses 301 and 302 such as ringback and steps are likely to occur. Assume that the waveform of the pulse signal demultiplexed by the demultiplexer 441 is directly detected by the detector 442 . At this time, if the baseline (threshold voltage for digital conversion, the same applies hereinafter) of the A/D converter 443 is near the amplitude center value of the transient responses 301 and 302 at the rise or fall of the pulse signal, the pulse signal may be erroneous. It will be detected. That is, one pulse signal (positive signal) 303 shown by a broken line in FIG. 3 is detected as an error signal 304 of a data string signal (signal crack) consisting of two pulses shown by a solid line in FIG. When this erroneous signal 404 is processed by the MCU 42, the FEM 41 will malfunction.

Erroneous signals may be caused not only by the transient responses 301 and 302 but also by the mixing of unintended signals. The demultiplexer 441 realizes suppression of the transient responses 301 and 302 and elimination of unintended signals with a simple configuration. In the following description, a signal line branched from the main signal line 401 and connected to the signal processing device 44 will be referred to as a common path 402.

A specific configuration example of the demultiplexer 441 is shown in FIG. The demultiplexer 441 includes an RF filter 4410, a first filter 4411, a second filter 4412, and a third filter 4413. In this embodiment, each filter has a passive configuration using only passive elements, rather than an active configuration using active elements. Therefore, it is possible to prevent the circuit configuration from becoming complicated due to the addition of control signals to the active elements.

The RF filter 4410 is an LC series circuit that includes an RF signal blocking inductor _L1 that has a high impedance with respect to the RF signal, and a DC component cutting capacitor _C1 that cuts a DC component, and is common to the main signal line 401. It is inserted between the connection part and the path 402. The inductance of the RF signal blocking inductor _L1 is, for example, 10 nH, and the capacitance of the DC component cutting capacitor _C1 is, for example, 1 μF.

The first filter 4411 is a filter that allows the communication signal of the first frequency f ₁ (including the f ₁ modulated wave) to pass through. In this example, the first filter 4411 is configured with an HPF (high pass filter) that passes communication signals having a frequency of approximately 80 MHz or higher. Specifically, one end of the capacitor C 11 is conductively connected to the connection point P ₁ with the common line 402 after passing through the RF filter 4410 when viewed from the main signal line 401, and the other end of the capacitor C ₁₁ is connected to the other end of the capacitor C ₁₁ . an inductor L ₁₁ connected to the inductor L 11 and whose other end is grounded, a capacitor C ₁₂ whose one end is connected to the other end of the capacitor C ₁₁ and one end of the inductor L ₁₁ , and whose one end is connected to the other end of the capacitor C ₁₂ . and the inductor _L12 whose other end is grounded constitute a CLCL type HPF. A connection point P ₃ between the other end of the capacitor C ₁₂ and one end of the inductor L ₁₂ is connected to the detection section 442 .

The second filter 4412 is a filter that passes the communication signal of the second frequency f ₂ (including the f ₂ modulated wave) and the communication signal of the third frequency f ₃ (including the f ₃ modulated wave). In this example, the second filter 4412 is configured with a BPF (band pass filter) that passes the second signal having a frequency of about 16 MHz. The third filter 4413 is a filter that passes the communication signal of the second frequency _f2 (including the _f2 modulated wave). In this example, the third filter 4413 is configured with an LPF (low pass filter) that passes signals with a frequency of approximately 70 MHz or less. The second filter 4412 and the third filter 4413 constitute a distribution filter in which a signal is distributed via the damping resistor R1.

The second filter 4412 connects, for example, a connection point P ₂ with the common line 402 located at a position passing through the RF filter 4410 when viewed from the main signal line 401 and a connection point P ₅ with the modulation section 444 or MCU 42. It is inserted into the signal line. Specifically, the second filter 4412 consists of a CL series circuit consisting of a capacitor C ₂₁ and an inductor L ₂₁ that are electrically connected to the connection point P ₂ , and a capacitor C ₂₂ and an inductor L ₂₂ that are electrically connected to the connection point P ₅ . It has an LC series circuit and an LC parallel circuit consisting of an inductor L ₂₃ and a capacitor C ₂₃ , one end of which is connected between the CL series circuit and the LC series circuit, and the other end of which is grounded.

A connection point A is a connection point between the CL series circuit, the LC series circuit, and one end of the LC parallel circuit. Connection point A is a location where the electrical length from connection point _P2 and the electrical length from connection point _P5 are approximately equal, or where the impedance looking at connection point _P2 and the impedance looking at connection point _P5 are approximately equal. It is desirable that the phase difference is equal, or the phase difference on the connection point _P2 side and the phase difference on the connection point _P5 side are almost equal.

One end of a damping resistor _R1 is connected to the connection point A. The other end of the damping resistor _R1 is connected to the third filter 4413. The third filter 4413 has one end connected to the other end of the damping resistor _R1 , and the other end connected to the connection point _P4 with the detection section 442. The third filter 4413 has two inductors L ₃₁ and L ₃₂ inserted between the other end of the damping resistor R ₁ and the connection point P ₄ , and one end connected between the two inductors L ₃₁ and L ₃₂ . and a capacitor C ₃₁ whose other end is grounded, and a capacitor C ₃₂ whose one end is connected between the inductor L ₃₂ and the connection point P ₄ and whose other end is grounded. Can be done.

The second filter 4412 may have a pass band of the second frequency f ₂ and the third frequency f ₃ . The amplitude characteristic is set to Butterworth characteristic. The Butterworth characteristic is a characteristic in which the pass band is flatter than that of a general BPF, and is also called a max flat characteristic. By setting the amplitude characteristic to the Butterworth characteristic, it is possible to suppress fluctuations in the signal level of the f ₂ modulated wave or the f ₃ modulated wave caused by load fluctuations (reactance fluctuations of passive elements due to termination conditions, etc.).

Note that the third filter 4413 may be an LPF or HPF with a passive configuration of other types. In addition, from the viewpoint of making the operation of the distributed filter more stable (operating as designed), the following points are required: between the connection point _P2 and the connection point _P4 , between the connection point _P2 and the connection point _P5 , and the connection point It is desirable to set the respective passbands between P ₄ and connection point P ₅ to be approximately the same.

Here, the damping resistor _R1 will be explained in detail. The damping resistor _R1 has the role of suppressing reflected waves between the third filter 4413 and the second filter 4412, and also adjusts the distribution level of the signal passing through the second filter 4412 and the signal passing through the third filter 4413. It has both roles.

Due to the above-described load fluctuation, the phase of the _f2 modulated wave or _f3 modulated wave changes, and the waveform of the _f2 modulated wave or _f3 modulated wave may not be as designed. In addition, transient responses such as ringback and steps may occur due to the reflected wave balance (deviation in signal level) between the branched signal lines, electrical path differences, coupling between filters, and the like. As shown in Figure 3, these phenomena cause disturbances in the signal waveform, but attempting to avoid these phenomena requires precise adjustment and matching for each modulated wave path, which increases time and cost. It takes.
In this embodiment, these phenomena are suppressed only by adjusting the signal level distribution using the damping resistor _R1 . The resistance value of the damping resistor _R1 is about 100Ω, but if it is in the range of 30Ω or more and 200Ω or less, disturbances in the signal waveform can be suppressed. The damping resistor _R1 may be a variable resistor, but may also be a fixed resistor if the range in which the above phenomenon can be suppressed is known.

The signal level split by the damping resistor R ₁ may be distributed as long as the signal level of the path from the connection point P ₂ to the connection point P ₄ <the signal level of the path from the connection point P ₂ to _{P 5} . Further, the signal level may be distributed so as to be equal between the path from the connection point P ₂ to the connection point P ₄ and the path from the connection point P ₄ to the connection point P ₅ . In this way, since the LC parallel circuit that reduces the signal level at a frequency other than the resonance frequency and the damping resistor _R1 are connected to the connection point A, the difference between the third filter 4413 and the second filter 4412 is reduced. The reflected wave balance can be adjusted, and the occurrence of unexpected phenomena can be suppressed.

Also, unlike T-type or π-type resistor distribution circuits, the signal level distribution at the same frequency (f ₂ = f ₃ ) is not affected by the terminal load, so the resistance value of the damping resistor R ₁ can be changed. You can easily adjust the signal distribution level by simply Therefore, it is possible to realize the demultiplexer 441 that is less susceptible to load fluctuations even in the high frequency band for V2X communication.

The above explanation is based on the premise that the second frequency f ₂ and the third frequency f ₃ are the same. When the second frequency f ₂ and the third frequency f ₃ are different frequencies, the resonant frequency of the second filter 4412 is set to approximately the third frequency f ₃ in the LC series circuit and approximately the second frequency f ₂ in the LC parallel circuit. do it. Note that the positions of the inductor and capacitor in the LC series circuit, CL series circuit, and LC parallel circuit may be interchanged.

In this manner, in the demultiplexer 441, there is no need to separately provide a complicated and precise matching/adjustment circuit for reflected waves, such as a transient response prevention circuit. Therefore, even in the high frequency band used in V2X communication, multiple frequencies can be correctly demultiplexed with a simple configuration. Moreover, not only two frequencies but also three frequencies can be handled without complicated circuit changes, so design and development costs can be suppressed.
In the following explanation, the signal line for the demultiplexed _f1 modulated wave will be referred to as the " _f1 path," the signal line for the _f2 modulated wave as the " _f2 path," and the signal line for the _f3 modulated wave as the " _f3 path." It is sometimes called.

An example of a signal transmitted through the _f1 path is shown in FIG. The vertical axis is DC voltage (V), and the horizontal axis is time (T). If the passive elements of the RF filter 4410 and the first filter 4411 are as designed, the signal transmitted through the _f1 path is only the _f1 modulated wave. However, in reality, due to variations in the passive elements constituting the first filter 4411 and unintended signals entering the _f1 path, unintended signals are present in the _f1 path, as illustrated in FIG. May be superimposed. Therefore, it is necessary to ensure sufficient isolation between the f ₁ path and the f ₂ path and between the f ₁ path and the f ₃ path. Note that in the example of FIG. 5, the signal level of the _f1 modulated wave is much higher than that of the unintended signal, but the signal level of the unintended signal may be closer to or higher than the signal level of the _f1 modulated wave. . The detection unit 442 reliably prevents erroneous detection of the _f1 modulated wave even in such a case.

A specific configuration example of the detection section 442 will be described with reference to FIG. 6. The detection section 442 includes a first detection section 4421, a second detection section 4422, and a third detection section 4423. The first detection section 4421 detects the first signal of the _f1 path output from the demultiplexing section 441. The second detection section 4422 detects a second signal obtained by removing the _f1 modulated wave from the first signal with a polarity opposite to that of the first detection section 4421. The detection section 442 combines and outputs the detection output of the first detection section 4421 and the detection output of the second detection section 4422. That is, the f ₁ detection signal (Tx/Rx signal) in which the two detection outputs are combined is output to the A/D converter 443 . The third detection unit 4423 detects the f ₂ modulated wave split by the distribution filter of the splitter 441 and outputs an f ₂ detection signal (CONTROL signal) to the A/D conversion unit 443 .

The first detection section 4421 includes a DC component cutting capacitor _C2 that is electrically connected to the connection point _P3 connected to the _f1 path of the splitter section 441, a load resistor _R2 whose other end is grounded, and a first detection section 4421. It has an element _D1 , a discharging resistor _R3 and a smoothing capacitor _C5 , each of which has its other end grounded. The discharging resistor _R3 and the smoothing capacitor _C5 are provided to improve the distortion of the detected waveform. The first signal is supplied to the anode of the first detection element _D1 via a DC component cutting capacitor _C2 and one end of a load resistor _R2 whose other end is grounded. The polarity of the signal passing through the first detection element _D1 is positive (high active).

The load resistor _R2 is set to a resistance value that causes the base line of A/D conversion to approach 0V by passing the DC component of the first signal and the DC component generated by detection to the ground (grounding line). In this example, the load resistance _R2 was set to 4.3 kΩ. Note that the load resistor _R2 can be replaced with a choke coil. Furthermore, a matching circuit may be inserted for matching.

The second detection unit 4422 includes a fourth filter 4424 whose one end is electrically connected to the connection point P ₃ connected to the f ₁ path of the demultiplexing unit 441, and a fourth filter 4424 which is connected with the opposite polarity to the first detection element D ₁ . It has two detection elements _D2 . The fourth filter 4424 is a resonant circuit having a high impedance with respect to the first frequency _f1 , for example, an LC parallel circuit consisting of an inductor _L41 and a capacitor _C42 , and the other end is the cathode of the second detection element _D2 . connected to. The anode of the second detection element _D2 is connected to the cathode of the first detection element _D1 , one end of the discharge resistor _R3, and one end of the smoothing capacitor _C5 .

The first detection element _D1 and the second detection element _D2 are diodes that can be used in a high frequency band, and desirably have the same characteristics. The values of the inductor L ₄₁ and capacitor C ₄₂ of the fourth filter 4424 of the second detection section 4422 are such that the phase difference between the cathode of the first detection element D ₁ and the anode of the second detection element D ₂ is The angle is set to a value of 90 degrees. However, the absolute value of this phase difference is in the range of more than 0 degrees and less than 90 degrees. This is because if the absolute value of the phase difference between them exceeds 90 degrees and approaches 180 degrees, the polarities of the first detection element D1 and the second detection element D2 may become the same. Note that a phase shifter (reactance element) may be separately inserted before and after the fourth filter 4424 in order to finely adjust the phase difference between the two. Furthermore, a matching circuit may be inserted between the second detection element D2 and the fourth filter 4424 for matching of unintended signals.

The third detection section 4423 includes a DC component cutting capacitor _C3 that is electrically connected to the connection point _P4 with the _f2 path of the splitter section 441, a load resistor _R4 whose other end is grounded, and a third detection element D. ₃ , a discharge resistor _R5 and a smoothing capacitor _C6 for improving the distortion of the detected waveform. The load resistor R ₄ is set to a resistance value that causes the base line of the A/D converter 443 to approach 0 V potential by flowing a DC component that exists in the f ₂ path or occurs during detection to the ground. The capacitance of the smoothing capacitor _C6 is, for example, 30 pF. As the third detection element _D3 , a diode having the same characteristics as the first detection element _D1 and the second detection element _D2 can be used.

As mentioned above, the signal passing through the first detection element _D1 is a first signal of multiple frequencies including the _f1 modulated wave and an unintended signal, and has a positive polarity with respect to the baseline of the A/D converter 443. be.
Focusing on the unintended signal, if the load resistor _R2 does not exist, the signal level (V) of the unintended signal will be a predetermined value as shown in the right diagram of Figure 7, but if the load resistor _R2 is present. As a result, the signal level (V) is suppressed as shown in the left diagram of FIG. On the other hand, the unintended signal passing through the second detection element _D2 is not only matched by the fourth filter 4421 but also has no load resistance, so the signal level (V) of the signal is equal to that of the first detection element D2. Greater than the unintended signal passing through element _D1 .

That is, the signal level of the communication signal detected by the first detection section 4421 is smaller than the signal level of the communication signal detected by the second detection section 4422. Therefore, if the load resistor _R2 is not provided, the signal level (V) of the unintended signal among the combined outputs of the first detection section 4421 and the second detection section 4422 will be as shown in the right diagram of FIG. Although it is smaller than the signal level (V) shown in the right figure, it remains positive. On the other hand, when the load resistance R ₂ exists as in this embodiment, the signal level (V) of the unintended signal among the combined outputs of the first detection section 4421 and the second detection section 4422 is as shown in FIG. As shown in the left diagram, the polarity is negative with respect to the base line of the A/D converter 443.

The A/D converter 443 includes an amplifier and a comparator (signal converter), which are not shown. A general-purpose operational amplifier can be used as the amplifier. The operational amplifier can be used as an active filter (a low-pass filter controlled by an active element) that removes harmonic components contained in the f ₁ detection signal and the f ₂ detection signal output from the detection section 442. The comparator compares them with an arbitrarily set threshold (baseline voltage value), converts the _f1 detection signal into a Tx/Rx signal, and converts the _f2 detection signal into a CONTROL signal, and inputs the signals to the MCU 42. In this example, since the original signal is a pulse signal, the main processing content of the signal conversion in the A/D converter 443 is envelope shaping of the signal exceeding the threshold value.

FIG. 9 is a diagram showing an example of the waveform of the _f1 detection signal input to the A/D converter 443. The _f1 detection signal includes a non-target signal in addition to the Tx/Rx signal. The detected waveform of the Tx/Rx signal has no waveform disturbance due to transient response, and the non-target signal has a polarity opposite to that of the Tx/Rx signal. Therefore, the base line of the A/D converter 443 can be brought close to 0V with respect to the Tx/Rx signal, and the range of A/D conversion can be widened. As a result, even if the signal level (V) of the unintended signal fluctuates or the signal level (V) of the Tx/Rx signal decreases, the Tx/Rx signal can be A/D converted correctly, resulting in high communication efficiency. Quality can be maintained. Further, it is not necessary to add a disturbance detection circuit or to perform complex detection processing such as signal separation processing and disturbance signal recognition processing, thereby making it possible to reduce costs.

FIG. 10 is a diagram showing an example of the waveform of the _f2 detection signal input to the A/D converter 443. In the _f2 detection signal, in addition to the CONTROL signal, only the LOG signal is mixed as a non-target signal. Furthermore, both signals have the same polarity. However, since the LOG signal and CONTROL signal are separated in time, no interference occurs.

As mentioned above, in the RF band, conventionally, circuit boards are created according to the number of communication signals to be used, and narrowband matching circuits, load fluctuation suppression circuits, etc. are installed on the signal lines formed on each circuit board. It is. However, in this embodiment, by employing a distribution type filter (third filter 4413 distributed from point A of second filter 4412) in the demultiplexer 441, it is possible to reduce the circuit area. Further, in the detection section 442, sufficient isolation of the _f1 modulated wave, the _f2 modulated wave, and the _f3 modulated wave can be achieved. Therefore, even if the circuit components of the filters 4411, 4412, 4413 of the demultiplexing section 441 and the detection section 442 are close to each other, sufficient isolation can now be ensured easily.

[Modified example]
In this embodiment, the first signal at the first frequency among the frequencies used in the V2X service includes a modulated wave of the Tx/Rx signal ( _f1 modulated wave), and the second signal at the second frequency includes the modulated wave of the CONTROL signal. Although an example has been described in which the _third signal at the third frequency includes a LOG signal modulated wave ( _f3 modulated wave), the frequency and type of signal used are not limited to these. . In the present embodiment, a configuration example of the bidirectional amplifier 4 of the wireless terminal 1 mounted on the vehicle, particularly the signal processing device 44, has been described. It can also be used in communication equipment, antenna devices, or mobile communication terminals.

[Example]
Next, an example of the signal processing device 44 will be described. FIG. 11 is a diagram showing an example of the signal processing device 44. As shown in FIG. In the signal processing device 44 of this embodiment, at least the demultiplexer 441 and the detector 442 can be implemented on one circuit board 100. The circuit board 100 is provided with one input/output terminal 101, two output terminals 102 and 103, and one input terminal 104. For convenience, the same reference numerals as those shown in FIGS. 4 and 6 are given to the electronic circuit elements.

The input/output terminal 101 is connected to a main signal line 401 . The output terminal 102 is connected to the Tx/Rx signal terminal of the A/D converter. The output terminal 103 is connected to the CONTROL signal terminal of the A/D converter. The input terminal 104 is connected to the output terminal of the modulation section 444 or the LOG signal terminal of the MCU 42. The electronic circuit connected to the input/output terminal 101, the output terminals 102, 103, and the input terminal 104 is composed of the circuit components and signal lines shown in FIGS. 4 and 6. The signal line is a distributed constant line, and the circuit components can be distributed constant components or lumped constant components. As the circuit board 100, for example, a high frequency printed circuit board of FR-4 standard can be used, but a high frequency printed circuit board with the same function may also be used.

According to this embodiment, when a signal line is shared by a plurality of communication signals, the load fluctuation of the signal line and the mixing of unintended signals, as well as the misdetection of each communication signal caused by these, can be prevented using only one circuit board 100. Since this can be avoided, a device equipped with this can be made smaller and lighter, and an increase in manufacturing costs can be suppressed. Note that the circuit board 100 may also have a configuration in which the AD conversion section 443 or the modulation section 444 is mounted.

The disclosure according to this embodiment and this example includes inventions of the following aspects.
[Aspect 1]
The invention according to aspect 1 includes a first detection section that detects a communication signal including signals of multiple frequencies, and a detection section that detects the communication signal from which the first signal of the first frequency is removed with a polarity opposite to that of the first detection section. and a second detection section, the signal processing device is configured to combine and output a detection output of the first detection section and a detection output of the second detection section.
According to the invention of aspect 1, the detection output of the second detection unit for the communication signal other than the first signal of the first frequency is combined with the detection output of the first detection unit with opposite polarity (cancelled), The influence of the unintended signal on the first signal can be reduced.

[Aspect 2]
In the invention according to aspect 2, in the invention according to aspect 1, the second detection section is arranged such that the phase difference between the communication signal from which the first signal has been removed and the communication signal detected by the first detection section is absolute. The signal processing device detects the communication signal from which the first signal is removed within a range of more than 0 degrees and less than 90 degrees.
According to the second aspect of the invention, it is possible to eliminate the possibility that the polarities of the detection output of the first detection section and the detection output of the second detection section become the same due to load fluctuation or the like.

[Aspect 3]
A third aspect of the invention is the signal processing device according to the first aspect, in which the signal level of the communication signal detected by the first detection section is smaller than the signal level of the communication signal detected by the second detection section. be.
According to the third aspect of the invention, the signal level of the detected output of the unintended signal having the opposite polarity is higher than the detected output of the unintended signal having the same polarity as the first signal (the detected output of the first detection unit). The signal level of the combined and output unintended signal always has the opposite polarity to the first signal. Therefore, the range of A/D conversion for the first signal is widened, and as a result, the communication sensitivity for the first signal can be increased. Additionally, since there is no need for a circuit to process unintended signals, design and development costs can be reduced.

[Aspect 4]
The invention according to aspect 4 is the invention according to aspect 3, in which the first detection section includes a first detection element in which the communication signal is input to an anode through one end of a resistor whose other end is grounded, The second detection unit includes a second detection element whose cathode receives the communication signal via a band rejection filter that blocks passage of the first signal, and connects the cathode of the first detection element and the second detection element. This is a signal processing device that is electrically connected to the anode of the element.
According to the invention of aspect 4, the effect of the unintended signal on the first signal is reduced, the reduction in the signal level of the first signal caused by the second detection section is reliably suppressed, and by the combination of inexpensive circuit components, This can be easily achieved.

[Aspect 5]
A fifth aspect of the invention is the signal processing device according to the fourth aspect, wherein the first detection element and the second detection element are diodes having the same characteristics.
According to the invention of aspect 5, the detection output of the first detection element and the detection output of the second detection element are consistent with the designed values, and it is possible to reduce the circuit design cost and stabilize the characteristics. can.

[Aspect 6]
In the invention of aspect 6, in the invention of aspect 1, the combined output of the detection output of the first detection section and the detection output of the second detection section is amplified by an amplifier that also serves as an active filter, and the combined output after the amplification is This is a signal processing device that includes an A/D conversion section that converts the signal into a digital signal using a predetermined threshold value.
According to the invention of aspect 6, harmonics can be removed from the first signal with a simple configuration, and the first signal can be converted into a first signal that is more faithful to the original signal waveform.

[Aspect 7]
Aspect 7 of the invention is, in any one of aspects 1 to 5, the first signal before detection, a second signal of a second frequency different from the first frequency, and a third frequency of the communication signal. and a third signal of 2 filter, and a third filter that passes only the third signal, and the communication signal including the third signal is distributed from a predetermined portion of the second filter through a predetermined load to the third filter. It is a signal processing device that is
According to the invention of aspect 7, since the second filter and the third filter constitute one distributed filter, it is possible to handle not only two frequencies but also three frequencies without complicated circuit changes. becomes possible. This makes it possible to reduce design and development costs.

[Aspect 8]
In the invention according to aspect 8, in the invention according to aspect 7, the second filter includes a first LC series circuit to which the first signal and the second signal before detection are input, and a second LC series circuit to which the third signal is input. a series circuit; and an LC parallel circuit, one end of which is electrically connected to a connection site between the output of the first LC series circuit and the output of the second LC series circuit, and the other end of which is grounded, and the third signal This is a signal processing device that distributes and inputs the communication signal containing the above from the connection portion to the three filters via the damping resistor.
According to the invention in aspect 8, the reflection balance can be easily adjusted by configuring one distribution filter with the second filter and the third filter using only general-purpose passive elements such as an LC circuit, that is, an inductor, a capacitor, and a resistor. This makes it possible to reduce circuit design costs.

[Aspect 9]
The invention according to aspect 9 is the invention according to aspect 8, wherein the second filter has an input/output terminal to which the communication signal is input/output, and an input terminal to which the third signal is input, and the second filter has an input terminal to which the third signal is input. The signal processing device is a signal processing device in which an electrical constant when looking at the input/output terminal (P2) and an electrical constant when looking at the input terminal from the connection portion are the same or substantially the same.
According to the invention of aspect 9, reflection balance between the second signal and the third signal can be easily achieved by configuring the distribution filter.

[Aspect 10]
The invention according to aspect 10 is the invention according to aspect 8, wherein the second filter has an input/output terminal to which the communication signal is input/output, and an input terminal to which the third signal is input, and the second filter has an input terminal to which the third signal is input. In the signal processing device, the signal level of the third signal reaching the input/output terminal and the signal level reaching the connection portion from the input terminal are the same or substantially the same.
According to the tenth aspect of the invention, it is possible to easily balance the reflections between the second signal and the third signal by configuring the distribution filter.

[Aspect 11]
An eleventh aspect of the invention is the signal processing device according to the eighth aspect, wherein the frequency-amplitude characteristic of the second filter is a Butterworth characteristic.
According to the invention of aspect 11, it is possible to suppress load fluctuations and reflected waves that are likely to occur due to the configuration of a distribution type filter, as well as fluctuations in signal level caused by such fluctuations.

1 Wireless terminal 44 Signal processing device 441 Demultiplexer 442 Detector 4421 First detector 4422 Second detector 4423 Third detector 443 A/D converter 4410 RF filter 4411 First filter 4412 Second filter 4413 Third filter 4424 Fourth filter D1 First detection element D2 Second detection element

Claims (11)

a first detection unit that detects a communication signal including signals of multiple frequencies;
a second detection unit that detects the communication signal from which the first signal of the first frequency has been removed, with a polarity opposite to that of the first detection unit;
combining and outputting a detection output of the first detection section and a detection output of the second detection section;
Signal processing device. The second detection section detects the communication signal from which the first signal has been removed, so that the phase difference between the communication signal and the communication signal detected by the first detection section is in the range of more than 0 degrees and less than 90 degrees in absolute value. , detecting the communication signal from which the first signal has been removed. The signal processing device according to claim 1, wherein the signal level of the communication signal detected by the first detection section is lower than the signal level of the communication signal detected by the second detection section. The first detection unit includes a first detection element in which the communication signal is input to an anode through one end of a resistor whose other end is grounded,
The second detection unit includes a second detection element to which the communication signal is input to the cathode via a band rejection filter that blocks passage of the first signal,
The signal processing device according to claim 3, wherein the cathode of the first detection element and the anode of the second detection element are electrically connected. the first detection element and the second detection element are diodes with the same characteristics;
The signal processing device according to claim 4. An A/R that amplifies a composite output of the detection output of the first detection section and the detection output of the second detection section with an amplifier that also serves as an active filter, and converts the amplified composite output into a digital signal at a predetermined threshold. The signal processing device according to claim 1, comprising a D conversion section. A demultiplexing unit that demultiplexes the first signal before detection among the communication signals, a second signal with a second frequency different from the first frequency, and a third signal with a third frequency,
The demultiplexer includes a first filter that passes the first signal before detection;
a second filter that passes the second signal and the third signal;
a third filter that passes only the third signal;
The communication signal including the third signal is distributed and input from a predetermined portion of the second filter to the third filter via a predetermined load.
A signal processing device according to any one of claims 1 to 5. The second filter includes a first LC series circuit to which the first signal and the second signal before detection are input, a second LC series circuit to which the third signal is input, and an output of the first LC series circuit. an LC parallel circuit, one end of which is electrically connected to the output of the second LC series circuit and the other end of which is grounded;
distributing and inputting the communication signal including the third signal from the connection portion to the third filter via a damping resistor;
The signal processing device according to claim 7. The second filter has an input/output terminal to which the communication signal is input/output, and an input terminal to which the third signal is input, and has an electrical constant when looking at the input/output terminal from the connection part and the connection part. 9. The signal processing device according to claim 8, wherein electrical constants viewed from the input terminal are the same or substantially the same. The second filter has an input/output terminal to which the communication signal is input/output, and an input terminal to which the third signal is input, and the third signal is transmitted from the connection portion to the input/output terminal. 9. The signal processing device according to claim 8, wherein the level and the signal level from the input terminal to the connection site are the same or substantially the same. the frequency-amplitude characteristic of the second filter is a Butterworth characteristic;
The signal processing device according to claim 8.

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