JP2009260406A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver capable of entering a communication established state by receiving a radio signal sent from a transmitter normally even if a disturbing radio wave of high field intensity is generated in a radio communication environment. <P>SOLUTION: The RF receiver 7 is provided with a notch filter 14 capable of attenuating a received radio wave of specific narrow frequency band. Further, an IF processing circuit 19 which controls the RF receiver 7 is provided with a tuning circuit 21 which controls the attenuation band of the notch filter 14. The tuning circuit 21 finds a disturbing radio wave included in a current received radio wave among received radio waves, and specifies a disturbing radio wave generated in a radio communication environment. Then the tuning circuit 21 varies the attenuation band of the notch filter 14 according to the frequency of the disturbing radio wave, so that the disturbing radio wave is not superposed on received radio waves received during reception. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a receiver that can receive a transmitted radio wave transmitted from a transmitter by a weak radio wave.

  2. Description of the Related Art Conventionally, in a vehicle key system, an electronic key system that uses an electronic key that can wirelessly transmit a unique key code of the key as a vehicle key has been adopted in various vehicle types. As one type of this electronic key system, for example, there is a key operation free system in which an electronic key automatically transmits a key code wirelessly. In this key operation free system, a request communication area is formed by a LF band signal as a key code return request around the vehicle, and when the electronic key enters the communication area and receives the request, the electronic key receives the key code. Reply to vehicle with RF band signal. When the vehicle receives this key code, it performs key collation. If the key collation is established, the vehicle permits or executes door lock / unlock and engine start.

  By the way, in this kind of electronic key system, a weak radio wave, that is, a radio wave having a low electric field strength is used as a radio signal to be used. This is because this type of weak radio wave does not require frequency allocation in use, and thus any frequency radio signal can be used. However, although such weak radio waves can be used at frequencies in various bands, they are used in many devices and devices such as radios and radars. Today, radio signals with this level of electric field strength are in the atmosphere. Have been flying around. Therefore, when this type of weak radio wave is used in the electronic key system, it is assumed that the radio signal transmitted from the electronic key may be disturbed by other communication radio waves and not reach the normal state until the vehicle receiver. However, there is a problem that the electronic key system cannot establish communication under the situation where such interference radio waves (noise) are generated.

By the way, as a kind of wireless communication systems that are currently known, for example, a channel that is not affected by interference radio waves in a communication environment is selectively selected from a plurality of channels (frequency). There is a channel selection type in which wireless communication is performed using a wireless signal. If this wireless communication format is adopted in the electronic key system, wireless communication between the vehicle and the electronic key is performed with a wireless signal having a frequency that is not affected by the interference radio wave during wireless communication. Even if an interfering radio wave is generated in the wireless communication environment between the two, it is possible to establish communication between the two parties. This type of channel-selective communication system is disclosed in, for example, Patent Document 1 and the like.
JP 2007-142886 A

  By the way, some of the jamming radio waves have a stronger electric field strength than a radio signal transmitted from the electronic key to the vehicle (receiver). Here, if it is assumed that the electronic key system performs wireless communication in a communication situation where jamming waves with an intensity exceeding the maximum input of the receiver's amplifier or demodulation circuit are generated, the reception at this time Since the device is in a state where the output is saturated by the jamming radio wave, the receiver cannot normally receive the radio signal transmitted from the electronic key. Therefore, for example, even if the channel selection formula described above is adopted, the receiver cannot receive a radio signal in any channel under the situation where a strong electric field interference wave is generated in each channel. There was still a problem that wireless communication was not established under the occurrence of jamming radio waves.

  An object of the present invention is to provide a receiver that can normally receive a radio signal transmitted from a transmitter and establish a communication establishment state even when an interference radio wave having a strong electric field strength is generated in a wireless communication environment. There is.

  In order to solve the above problems, in the present invention, in a receiver capable of receiving a transmitted radio wave transmitted from a transmitter with a weak radio wave, a frequency in a specific band can be attenuated among received radio waves received from the transmitter. And a tunable notch filter whose attenuation band can be adjusted, a jamming radio wave identification means for identifying a jamming radio wave contained in the received radio wave from the received radio wave received, and the jamming radio wave specified by the jamming radio wave identification means The gist is provided with notch filter control means for adjusting the frequency to the tunable notch filter.

  According to this configuration, for example, when the receiver is in a standby state waiting for reception of a transmission signal transmitted from the transmitter, the receiver generates the attenuation band of the tunable notch filter in the communication environment at that time. Execute tuning operation to match the jamming signal. As this tuning operation, the interfering radio wave specifying means examines which interfering radio wave is received from the received radio waves accepted by the receiver at that time, and specifies the interfering radio wave generated in the communication environment. The notch filter control means adjusts the attenuation band of the notch filter to the jamming radio wave specified by the jamming radio wave specifying means. As a result, the attenuation band of the notch filter is sequentially set to the jamming wave generated in the communication environment at that time, so when the signal is received by the receiver, the jamming wave is removed from this signal. In this case, it becomes difficult for removal leakage to occur. Therefore, it is possible to improve the reception performance of the receiver.

  In the present invention, a programmable attenuator capable of attenuating the received radio wave and adjusting the attenuation amount in the process of receiving processing to process the received radio wave, and the interference radio wave specifying means, first, the attenuation value of the programmable attenuator Is set low, the first characteristic value of the processing signal generated when the received radio wave is received is processed, and then the attenuation value of the programmable attenuator is set higher than before. In this case, the second characteristic value of the processed signal at that time is obtained, the internally generated distortion included in the processed signal is determined based on these characteristic values, and the processed signal after the internally generated distortion is removed is used. The gist is to identify the jamming radio wave.

  According to this configuration, the characteristic value (first value) that each processing signal has before and after switching the attenuation amount of the programmable attenuator is internally generated distortion that rides on the processing signal generated in the receiver during reception processing. (Characteristic value, second characteristic value). Then, an internally generated distortion is removed from the processed signal to generate an ideal processed signal, and an interference radio wave included in the received radio wave at that time is specified using the ideal processed signal. Therefore, when identifying the jamming radio wave, it is possible to identify the jamming radio wave with higher accuracy if the jamming radio wave is identified using the ideal processing signal in this way. This contributes to improved reception performance.

  In the present invention, the first characteristic value and the second characteristic value are values of the electric field strength of the processing signal, and the jamming radio wave identification unit is configured to output the processing signal when the attenuation value of the programmable attenuator is low. The gist is to determine the internally generated strain based on the difference between the electric field strength possessed and the electric field strength possessed by the processed signal when the attenuation value of the programmable attenuator is high.

  According to this configuration, a simple process of taking the difference between the electric field intensity of the processing signal when the attenuation value of the programmable attenuator is lowered and the electric field intensity of the processing signal when the attenuation value of the programmable attenuator is increased, The generated distortion can be specified.

  In the present invention, the interfering radio wave specifying unit performs an operation of actually reading the received radio wave when specifying the interfering radio wave, and determines that a received radio wave having a frequency that matches a preamble in the radio wave is a regular radio wave. On the other hand, the gist of determining that the frequency of the preamble does not match is the interference radio wave.

  According to this configuration, when the receiver receives a received radio wave, it performs an operation of actually reading the radio wave content (data) of the received radio wave, and a radio wave having a frequency that matches the preamble in the radio wave. Is processed as a jamming radio wave. In this way, if it is determined that each type of received radio wave is a regular radio wave or an interfering radio wave by actually looking at the preamble in the received radio wave, for example, outgoing signals having different frequencies are accepted. However, it becomes possible for the receiver to accept these transmission signals without any delay. Therefore, it is possible for the receiver to receive not only one type of transmitted radio wave but also a plurality of types of transmitted radio waves.

  In the present invention, the notch filter control means sweeps the attenuation band with respect to the jamming radio wave specified by the jamming radio wave identification means, so that the electric field strength of the jamming radio wave can be minimized. The gist is to combine filters.

  According to this configuration, the attenuation band of the notch filter is swept with respect to the jamming radio wave specified by the jamming radio wave specifying means, and the tunable notch filter is tuned so that the electric field strength of the jamming radio wave is most reduced. . Therefore, it becomes possible to tune the tunable notch filter to a suitable position with the highest attenuation effect, which contributes to further improvement of the reception performance of the receiver.

  ADVANTAGE OF THE INVENTION According to this invention, even if the interference electric wave with a strong electric field intensity | strength has generate | occur | produced in the radio | wireless communication environment, the radio signal transmitted from the transmitter can be received normally and a communication establishment state can be taken.

Hereinafter, an embodiment of a receiver embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, an electronic key system 3 that uses a portable device 2 that can wirelessly transmit a key code unique to a key as a vehicle key is mounted on the vehicle 1. In this electronic key system 3, if the key code transmitted from the portable device 2 matches that of the vehicle 1 and ID verification is established, door locking / unlocking and engine starting of the vehicle 1 are permitted or executed. The electronic key system 3 includes a key operation free system that automatically transmits a key code from the portable device 2 to the vehicle 1 and a wireless key system that performs this key code transmission by button operation of the portable device 2. In this electronic key system, a weak radio wave (for example, about 54 dBμV / m) is used as a transmission radio wave exchanged between the vehicle 1 and the portable device 2. The portable device 2 corresponds to a transmitter.

  In the electronic key system 3, the vehicle 1 is provided with a system control unit 4 that manages the electronic key system 3. In addition, the vehicle 1 has an on-vehicle LF transmitter 5 disposed on the door outer wall or the like and capable of transmitting an LF-band radio signal to the outside of the vehicle, and an LF-band radio signal disposed on the vehicle. An in-vehicle LF transmitter 6 and an RF receiver 7 that is disposed in the vehicle and can receive an RF band radio signal are provided. The LF transmitters 5 and 6 and the RF receiver 7 are connected to the system control unit 4 through electrical wiring, and the operation is managed by the system control unit 4. The RF receiver 7 corresponds to the receiver.

  When the electronic key system 3 is used as a key operation free system, when the vehicle 1 is in a parked state (door lock locked, engine stopped), the portable device 2 receives an LF band request signal Srq transmitted from the LF transmitter 5 outside the vehicle. Upon reception, the portable device 2 responds to this request and transmits an ID signal Sid carrying its own key code to the vehicle 1 as a signal in the RF band (eg, 312 MHz). When the ID signal Sid is received by the RF receiver 7, the system control unit 4 compares the key code of the portable device 2 with the key code of the vehicle 1 and performs ID verification (verification outside the vehicle), and vehicle verification is established. Permit or execute unlocking of the door lock in the locked state. Further, when the vehicle 1 is in a stopped state (door lock unlocked, engine stopped), if the vehicle outside verification is established, the door lock is permitted or executed.

  Further, when the system control unit 4 detects that the door of the vehicle 1 is opened by a door courtesy switch (not shown) of the vehicle 1, this time, the system control unit 4 transmits a request signal Srq from the in-vehicle LF transmitter 6 to the inside of the vehicle. When the portable device 2 receives this request signal Srq in the vehicle, it transmits the ID signal Sid in the same way as when it is outside the vehicle. When this ID signal Sid is received by the RF receiver 7, the system control unit 4 performs ID verification (in-vehicle verification) in the same manner as in the case of external verification, and permits engine start if internal verification is established.

  When the electronic key system 3 is used as a wireless key system, when the unlock button 8 of the portable device 2 is operated while the vehicle 1 is parked, the unlock request Sul is transmitted from the portable device 2 to the RF band (for example, 312 MHz). ) Signal. When the unlocking request Sul is received by the RF receiver 7, the system control unit 4 unlocks the door lock along the unlocking request Sul if the key code in the unlocking request Sul is correct. Further, when the lock button 9 of the portable device 2 is operated while the vehicle 1 is stopped, the locking request Slk is transmitted from the portable device 2 as a signal in the RF band (for example, 312 MHz). When receiving the lock request Slk by the RF receiver 7, the system control unit 4 locks the door lock along the lock request Slk if the key code in the lock request Slk is correct. The ID signal Sid, the unlock request Sul, and the lock request Slk constitute a transmission radio wave.

  As shown in FIG. 2, the RF receiver 7 is provided with a receiving antenna 10 made of, for example, a loop antenna. A band-pass filter 11 that passes only radio waves having a frequency within a necessary range among the received radio waves Erv received by the receive antenna 10 is connected to the receiving antenna 10 as one component of the RF receiver 7. By the way, although various RF signals (ID signal Sid, unlock request Sul, lock request Slk) transmitted from the portable device 2 to the vehicle 1 are described as 312 MHz in this example, this RF signal is modulated (FM modulation). ) And transmitted to the vehicle 1, it is actually a transmitted radio wave having a predetermined frequency bandwidth. Therefore, the band-pass filter 11 of this example works so as to pass radio waves in a frequency band that takes this modulation out of the received radio waves Erv received by the receiving antenna 10.

  The bandpass filter 11 includes a programmable attenuator 12 that can select the attenuation amount while attenuating the bandpass filter output 11 a (see FIG. 5) output from the bandpass filter 11 to a predetermined value. Connected as a component. As described above, the programmable attenuator 12 is mounted on the RF receiver 7 when the received radio wave Erv having a strong electric field strength (signal reception strength: unit: dBμV / m) exceeding a certain level is applied to the RF receiver 7. This is because the receiver 7 is saturated and the reception performance is deteriorated, so that the reception radio wave Erv having a strong electric field strength is intentionally weakened. The programmable attenuator 12 is connected to an amplifier 13 that amplifies the attenuator output 12a of the programmable attenuator 12 to a certain value.

  A notch filter 14 that attenuates only radio waves in a specific frequency band in the amplified output 13 a output from the amplifier 13 is connected to the amplifier 13 as one component of the RF receiver 7. The notch filter 14 uses a frequency band within a predetermined range in the amplified output 13a (received radio wave Erv), for example, a narrow band of 10 MHz between 320 and 330 MHz as an attenuation band 15 (see FIG. 11). The amplified output 13a (received radio wave Erv) can be attenuated in the region of. The notch filter 14 of this example has a function of removing the jamming radio wave Evd from the reception radio wave Erv by passing the jamming radio wave Evd contained in the reception radio wave Erv through the attenuation band 15 and eliminating (cutting) it. Further, the notch filter 14 of this example is a tunable type capable of switching the attenuation band 15. The notch filter 14 corresponds to a tunable notch filter.

  A tuner 16 that changes the frequency of the notch filter output 14 a output from the notch filter 14 is connected to the notch filter 14 as one component of the RF receiver 7. The tuner 16 has a VCO (Voltage Controlled Oscillator) 17 that changes the input frequency (notch filter output 14a) to a predetermined value according to the voltage, and the VCO 17 so that the output of the VCO 17 takes a constant value without fluctuation. A PLL system comprising a PLL (Phase Locked Loop) 18 to be controlled is adopted. By the way, since the received radio wave Erv received by the receiving antenna 10 is an RF signal (RF = Radio Frequency) having a high frequency of several hundred MHz, if this received radio wave Erv is transmitted as an RF signal, its transmission loss The problem that becomes large occurs. Therefore, the tuner 16 of this example works to reduce the captured notch filter output 14a to a low frequency and suppress transmission loss during radio wave transmission as much as possible.

  An IF processing circuit (intermediate frequency generation circuit) 19 that performs overall control of the RF receiver 7 is connected to the tuner 16 as one component of the RF receiver 7. The IF processing circuit 19 is provided with a demodulation circuit 20 that can demodulate based on the acquired modulation signal. The IF processing circuit 19 demodulates the tuner output Eout acquired from the tuner 16 by the demodulation circuit 20 and outputs the demodulated signal Fmd to various ECUs (not shown) in the vehicle. The tuner output Eout corresponds to the processing signal, and the processing of processing the received radio wave Erv through at least the programmable attenuator 12, the amplifier 13 and the tuner 16 corresponds to the reception processing.

  The tuner 16 is provided with a tuning circuit 21 that tunes the notch filter 14 so that the attenuation band 15 of the notch filter 14 is matched with the interference radio wave Evd. The tuning circuit 21 is connected to the notch filter 14 and manages the operation of the notch filter 14. The tuning circuit 21 calculates the frequency of the interference radio wave Evd from the reception radio wave Erv actually captured by the reception antenna 10, and adjusts the attenuation band 15 of the notch filter 14 to this interference radio wave frequency, thereby performing a notch filter tuning operation ( (Notch filter adjustment processing). The tuning circuit 21 repeatedly executes this notch filter tuning operation at predetermined time intervals while the power is supplied to the RF receiver 7 and is in an activated state. The tuning circuit 21 constitutes a jamming radio wave specifying means and a notch filter control means.

  The tuning circuit 21 is connected to the programmable attenuator 12 and manages the operation of the programmable attenuator 12. When executing the tuning operation, the tuning circuit 21 increases the received radio wave Erv when the attenuation amount of the programmable attenuator 12 is reduced (in this example, the minimum value “0”) and the attenuation amount of the programmable attenuator 12 (in this example, From the value of the received radio wave Erv when “10 dBμV / m” is inserted), the internally generated distortion 22 (also referred to as inter-modulation distortion (IM) included in the received radio wave Erv: see FIG. 6B) ) And an IM separation process for separating the internally generated distortion 22 from the received radio wave Erv. The internally generated distortion 22 is noise that is generated secondarily in the RF receiver 7 such as the tuner 16. Then, the tuning circuit 21 extracts the frequency of the disturbing radio wave Evd from the received radio wave Erv after removing the internally generated distortion 22 from the received radio wave Erv. The tuning circuit 21 is also connected to the tuner 16 to manage the operation of the tuner 16.

  Next, the operation procedure of the tuning operation of the notch filter 14 performed by the RF receiver 7 of this example will be described using the flowchart of FIG. In this flowchart (notch filter tuning operation), although the RF receiver 7 is powered on, a standby state waiting for reception of an RF signal (transmitted radio wave) transmitted from the portable device 2, that is, a communication partner is searched ( It is repeatedly executed at the timing of searching (for example, a cycle of several seconds).

  For example, as shown in FIG. 4, a case is assumed where the reception antenna 10 receives a reception radio wave Erv in which the interference radio wave Evd is on the regular radio wave Ek. When the receiving antenna 10 receives the received radio wave Erv, the received radio wave Erv is passed through the bandpass filter 11. From the bandpass filter 11, as shown in FIG. A bandpass filter output 11a in which only the frequency of (bandwidth) appears is output. The bandpass filter output 11a has an RF signal frequency that is the target value of the bandpass filter 11 due to the performance characteristics of the bandpass filter 11 (in this example, 312 MHz) as a peak, and the electric field strength toward the boundary of the communication bandwidth. Takes a value that gradually decreases.

By the way, when the received radio wave Erv is allowed to pass through the amplifier 13 and the tuner 16 incorporated in the RF receiver 7, the presently generated distortion 22 is superimposed on the received radio wave Erv due to the component characteristics thereof. There is. For this reason, if there is no internally generated distortion 22, the tuner 16 outputs a tuner output (ideal tuner output) Eout1 on which only the regular radio wave Ek and the disturbing radio wave Evd ride as shown in FIG. Nevertheless, as shown in FIG. 7, when the internally generated distortion 22 occurs within the communication bandwidth of the bandpass filter 11, the tuner 16 generates an ideal tuner output Eout1 as shown in FIG. The tuner output Eout2 on which the internally generated distortion 22 is mounted is output. The internally generated distortion 22 is generated when the regular radio wave Ek having a close frequency and the disturbing radio wave Evd interfere with each other. Here, assuming that the frequency of the regular radio wave Ek is Fk, the frequency of the jamming radio wave Evd is Fr, and the frequency of the internally generated distortion 22 is Fim, the internally generated distortion 22 is generated with the following relationship.
Fim = X · Fk ± Y · Fr (X, Y = 0, 1, 2,...)
Therefore, as can be seen from this equation, the internally generated distortion 22 is generated over various frequencies corresponding to the combination of the coefficient X and the coefficient Y, and these are superimposed on the tuner output Eout. In this way, if a large number of internally generated distortions 22 are superimposed on the tuner output Eout, these may interfere with the reading of the regular radio wave Ek, and there is a possibility that the reception performance will deteriorate.

  Therefore, the tuning circuit 21 first performs IM separation processing for removing the internally generated distortion 22 from the received radio wave Erv (regular radio wave Ek and jamming radio wave Evd) as a tuning operation. As this IM separation processing, the tuning circuit 21 first sets the attenuation value of the programmable attenuator 12 to the minimum (in this example, “0”) (step 100). At this time, the tuner 16 outputs a tuner output Eout3 that is not attenuated by the programmable attenuator 12 (a tuner output according to the group of solid arrows in FIG. 8). The tuning circuit 21 refers to (searches) the tuner output Eout3 acquired from the tuner 16 at this time, and records the peak value (electric field strength) Ea when each peak is taken in the output waveform of the tuner output Eout3. That is, as shown in FIG. 9, the tuning circuit 21 creates a list table 23 in which the frequency (peak frequency) f when the tuner output Eout3 takes a peak and the peak value Ea at each frequency f are summarized (step 101). Note that the peak here refers to a phenomenon when the output waveform of the tuner output Eout3 takes the peak of a mountain, and occurs at the location indicated by the arrow in FIG.

  Subsequently, the tuning circuit 21 inserts a predetermined attenuation amount R (10 dB in this example) into the programmable attenuator 12 taking the minimum value, and increases the attenuation value by this insertion attenuation amount R (step 102). . At this time, the tuner 16 outputs a tuner output Eout4 (a tuner output according to the broken line arrow group in FIG. 8) attenuated by the amount of insertion attenuation R by the programmable attenuator 12. The tuning circuit 21 refers to (searches) the tuner output Eout4, and similarly to the case where the attenuation amount of the programmable attenuator 12 is minimized, the peak value Eb (electric field) when each peak is taken in the output waveform of the tuner output Eout4. Intensity) is recorded, and a list table 24 as shown in FIG. 10 is created (step 103). The peak values Ea and Eb constitute the first characteristic value and the second characteristic value.

  By the way, when comparing the tuner output Eout3 when the attenuation amount of the programmable attenuator 12 is minimized and the tuner output Eout4 when the predetermined attenuation amount is inserted into the programmable attenuator 12, the peak according to the regular radio wave Ek and the interference radio wave The peak according to Evd takes a change in which the value attenuates by the insertion attenuation amount R, whereas the peak according to the internally generated distortion 22 takes a value Rx that is lower than the insertion attenuation amount R. Therefore, if the difference between the peak value Ea when the attenuation amount of the programmable attenuator 12 is minimized and the peak value Eb when the predetermined attenuation amount is inserted into the programmable attenuator 12 is calculated and this value is seen, a plurality of values exist. It should be understood which of the peaks is due to the internally generated strain 22.

  Therefore, after creating the two list tables 23 and 24, the tuning circuit 21 calculates the difference Ex (= Ea−Eb) between the peak values Ea and Eb for each peak (step 104). Then, the tuning circuit 21 sets the difference Ex as a normal value for the peak where the difference Ex takes the same value as the insertion attenuation amount R, and internally sets the peak where the difference Ex takes a value larger than the insertion attenuation amount R. The generated distortion 22 is determined, and this peak is excluded from the tuner output Eout4 (step 105). Subsequently, the tuning circuit 21 collects the frequencies of the peak groups remaining after the exclusion process, and takes in this signal as an ideal tuner output Eout1 (see FIG. 6). Therefore, the ideal tuner output Eout1 without the internally generated distortion 22 is obtained through this IM separation processing.

  After this IM separation processing, the tuning circuit 21 subsequently proceeds to notch filter adjustment processing for matching the attenuation band 15 of the notch filter 14 to the jamming radio wave Evd. As the notch filter adjustment processing, the tuning circuit 21 first demodulates the ideal tuner output Eout1 by the demodulation circuit 20 (step 106). After the demodulation processing, the tuning circuit 21 actually reads the demodulated signal Sfk, and identifies the jamming radio wave Evd by checking at which radio wave frequency in the demodulated signal Sfk the preamble matches (locks) (step 107). ). That is, the tuning circuit 21 performs an operation of actually reading the demodulated signal Sfk, and processes a signal having a frequency that matches the preamble as a normal wave Ek, and processes a signal having a frequency that does not match the preamble as a jamming wave Evd. Here, actually checking the preamble to see which frequency the regular radio wave Ek has is not to accept only one type of RF signal, but to accept many types of RF signals with different frequencies. This is to make it possible. The preamble is an identification code that serves as a basis for identifying a transmitter (transmitter) that is a communication partner. When the preamble is locked, it indicates that radio waves can be received from a legitimate transmitter. . If the preamble is locked at this time, the transmitted radio wave is accepted from the regular communication partner at this time, and at this time, radio wave reception is established.

  Subsequently, when the tuning circuit 21 knows the frequency of the jamming radio wave Evd, next, as shown in FIG. 11, the tuning circuit 21 temporarily adjusts the attenuation band 15 of the notch filter 14 to the frequency of the jamming radio wave Evd and starts moving this position. As a position, the notch filter 14 is tuned so as to minimize the received signal strength indicator (RSSI) while sweeping the attenuation band 15 of the notch filter 14 (step 108). That is, the value at which the notch filter 14 can reduce the electric field strength of the jamming radio wave Evd to the minimum value within the attenuation band 15 varies depending on the frequency of the target jamming radio wave Evd at any given time. The attenuation band 15 of the notch filter 14 is set while searching for a position where it can be dropped. When this band setting is completed, the tuning operation of the notch filter 14 is finished.

  When the RF signal transmitted from the portable device 2 is received by the receiving antenna 10 under the condition where the tuning operation of the notch filter 14 has been completed, the interference signal Evd is temporarily added to the received signal Erv. Even if this is the case, the interference radio wave Evd is removed by the notch filter 14 tuned so that the attenuation band 15 is adjusted to the interference radio wave Evd, and only the regular radio wave Ek is transmitted to the IF processing circuit 19. In this way, in this example, the attenuation band 15 of the notch filter 14 is adjusted to the interfering radio wave Evd generated in the communication environment from time to time, so that the leakage of the interfering radio wave Evd hardly occurs during radio wave reception. Become. Therefore, the reception performance of the RF receiver 7 is higher.

  In this example, prior to the start of the tuning operation of the notch filter 14, the attenuation amount of the programmable attenuator 12 is switched, and the received radio wave Erv is passed through the RF receiver 7 from the values of the tuner outputs Eout3 and Eout4 before and after the switching. The internally generated distortion 22 generated at the time is determined. Then, the interfering radio wave Evd is specified using the ideal tuner output Eout1 from which the internally generated distortion 22 is removed, and the attenuation band 15 of the notch filter 14 is adjusted to the interfering radio wave Evd specified through this procedure. Therefore, if the jamming radio wave Evd is extracted from the ideal tuner output Eout1 in which the internally generated distortion 22 is excluded in this way, the jamming radio wave Evd contained in the reception radio wave Erv can be more accurately determined. This contributes to securing higher reception performance of the receiver 7.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) An RF receiver 7 is provided with a tunable notch filter 14, and the attenuation band 15 of the notch filter 14 is adjusted to the jamming wave Evd generated in the wireless communication environment at that time. Tune each time. Therefore, when the RF receiver 7 receives the RF signal, even if it receives the jamming radio wave Evd together with the RF signal, the jamming radio wave Evd can be more reliably removed from the RF signal. The reception performance of the receiver 7 can be made high.

  (2) When the jamming radio wave Evd is specified from the received radio wave Erv, IM separation processing is performed to remove the internally generated distortion 22 from the tuner output Eout4, and the jamming radio wave from the ideal tuner output Eout1 from which the internally generated distortion 22 has been removed. Specify Evd. For this reason, if the jamming radio wave identification is performed with such an ideal tuner output Eout1, the jamming radio wave Evd is identified with higher accuracy, which is highly effective in further improving the reception performance of the RF receiver 7.

  (3) The internally generated strain 22 is identified by the difference Ex between the electric field intensity at the peak when the attenuation value of the programmable attenuator 12 is minimized and the electric field intensity at the peak when the predetermined attenuation value is inserted into the programmable attenuator 12. And the difference Ex having a value larger than the insertion attenuation amount R is specified as the internally generated distortion 22. Therefore, this type of internally generated distortion 22 can be specified by a simple process of taking a binary difference.

  (4) The interference radio wave Evd in the received radio wave Erv is specified by actually reading the demodulated signal Sfk of the received radio wave Erv and checking at which frequency the preambles match. Therefore, the RF receiver 7 can accept not only one type of transmitted radio wave but also multiple types of transmitted radio waves. This also leads to an effect that various unpredictable jamming waves Evd can be excluded from reception targets.

  (5) The attenuation band 15 of the notch filter 14 is tuned by sweeping the attenuation band 15 of the notch filter 14 with respect to the jamming radio wave Evd extracted as the preamble does not match, so that the electric field intensity of the jamming radio wave Evd is most reduced. This is done by setting the position to take the value. Therefore, the notch filter 14 can be tuned to a suitable position with the highest attenuation effect.

  (6) The notch filter tuning operation is repeatedly executed at predetermined time intervals for searching for a communication partner while the RF receiver 7 is powered on. Therefore, since the jamming radio wave Evd generated in the wireless communication environment at that time is specified each time, the notch filter 14 can be tuned with higher accuracy.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
When specifying the internally generated distortion, the programmable attenuator 12 is lowered in the attenuation value and then increased in the attenuation value, but the attenuation amount at this time is not limited to “0” and “10 dB”. In other words, each attenuation value is not particularly limited as long as there is a magnitude relationship between the attenuation values.

The radio wave that can be received by the RF receiver 7 is not necessarily limited to the RF signal, and a signal having a frequency other than this may be used.
The tuning operation of the notch filter 14 does not necessarily require IM separation processing (identification of the internally generated distortion 22), and this processing may be omitted.

  The jamming radio wave identification means is not limited to identifying the jamming radio wave Evd by a method of checking whether the preambles match (lock). For example, the interference radio wave Evd and the regular radio wave Ek may be distinguished from each other by looking at the electric field strength of each reception frequency.

  The RF receiver 7 is not limited to being able to receive signals of a plurality of frequencies by performing reception processing by preamble of the received radio wave Erv. That is, the RF receiver 7 may be capable of receiving only one type of frequency. In this case, when receiving the received radio wave Erv, an operation for preamble of the received radio wave Erv becomes unnecessary, so that the receiving operation can be simplified.

  The tuning of the notch filter 14 does not necessarily require processing for setting the position where the electric field strength of the jamming radio wave Evd takes the minimum value by sweeping the attenuation band 15 when the attenuation band 15 is aligned. For example, the attenuation band 15 may be aligned by bringing the midpoint of the attenuation band 15 to the determined frequency of the interference radio wave Evd.

  The RF receiver 7 is not limited to taking an active state while the power is on. For example, a tuning-on button may be provided in the RF receiver 7 and the tuning operation may be executed while this button is on.

  The RF receiver 7 is not necessarily mounted on this type of vehicle 1 and may be employed in other devices and devices. Further, the RF receiver 7 is not necessarily applied to this type of electronic key system 3, and the application target is not particularly limited as long as the system performs wireless communication.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(1) In any one of claims 1 to 5, the tuning operation for specifying the jamming radio wave and adjusting the tunable notch filter to the jamming radio wave is performed during a period during which the receiver is in its operation mode. It is executed repeatedly at intervals. According to this configuration, the jamming radio wave generated in the communication environment from time to time is specified each time, so that the tuning of the tunable notch filter can be performed with higher accuracy.

The schematic diagram which shows the outline of the electronic key system in one Embodiment. The block diagram which shows the specific structure of a receiver. The flowchart which shows the process of a notch filter tuning operation | movement. The wave form diagram which shows the frequency-electric field strength characteristic of the received radio wave in a receiver. The wave form diagram which shows the frequency-electric field strength characteristic of the received electromagnetic wave after passing a band pass filter. (A) is a waveform diagram of an ideal tuner output that does not include internally generated distortion, and (b) is a waveform diagram of a tuner output that includes internally generated distortion. The wave form diagram which shows the frequency-electric field strength characteristic of the tuner output including internally generated distortion. The wave form diagram which shows the frequency-field strength characteristic of the tuner output before and behind that which changed the attenuation amount of the programmable attenuator. A table when the attenuation value of the programmable attenuator is lowered. A table when the attenuation value of the programmable attenuator is increased. Explanatory drawing explaining the operation | movement at the time of notch filter tuning.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Portable machine as a transmitter, 7 ... RF receiver as a receiver, 12 ... Programmable attenuator, 14 ... Notch filter as a tunable notch filter, 15 ... Attenuation band, 21 ... Interference wave specifying means and notch filter control Tuning circuit constituting means, 22 ... internally generated distortion, Sid ... ID signal constituting outgoing radio wave, Slk ... locking request constituting outgoing radio wave, Sul ... unlocking request constituting outgoing radio wave, Erv ... received radio wave, Evd ... jamming radio wave, R ... attenuation, Eout ... tuner output as processing signal, Ea ... electric field strength (peak value) as first characteristic value, Eb ... electric field strength (peak value) as second characteristic value, Ex ... Difference, Ek ... regular radio wave, f ... frequency.

Claims (5)

In a receiver that can receive outgoing radio waves transmitted from weak transmitters,
A tunable notch filter capable of attenuating the frequency of a specific band of received radio waves received from the transmitter and adjusting the attenuation band;
Interfering radio wave identification means for identifying the interfering radio wave included in the received radio wave from the received radio wave,
A receiver comprising: notch filter control means for adjusting the tunable notch filter to the frequency of the jamming radio wave specified by the jamming radio wave specifying means. A programmable attenuator capable of attenuating the received radio wave in the course of the reception process for adding processing to the received radio wave and adjusting the attenuation;
The interference radio wave specifying means first determines a first characteristic value of a processing signal generated when the received radio wave is received by setting the attenuation value of the programmable attenuator low, and then Set the attenuation value of the programmable attenuator higher than before, this time obtain the second characteristic value of the processed signal at that time, determine the internally generated distortion included in the processed signal based on these characteristic values, The receiver according to claim 1, wherein the jamming radio wave is specified using the processed signal after the internally generated distortion is removed.   The first characteristic value and the second characteristic value are values of the electric field strength of the processing signal, and the interference radio wave specifying unit is configured to determine the electric field strength of the processing signal when the attenuation value of the programmable attenuator is low. The receiver according to claim 2, wherein the internally generated distortion is determined based on a difference between an electric field strength of the processing signal when the attenuation value of the programmable attenuator is high.   The interfering radio wave identification means performs an operation of actually reading the received radio wave when identifying the interfering radio wave, and determines that the received radio wave having a frequency that matches the preamble in the radio wave is a regular radio wave, The receiver according to any one of claims 1 to 3, wherein one having a frequency with which the preambles do not match is determined as the jamming radio wave.   The notch filter control means adjusts the tunable notch filter at a position where the electric field strength of the jamming radio wave can be minimized by sweeping the attenuation band with respect to the jamming radio wave specified by the jamming radio wave identification means. The receiver as described in any one of Claims 1-4 characterized by the above-mentioned.

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