JP5076923B2 - Wireless receiver - Google Patents

Description

  The present invention relates to a radio receiving apparatus that receives a radio frequency signal and converts it into an intermediate frequency.

2. Description of the Related Art Conventionally, a radio apparatus that automatically adjusts a signal level of a received radio frequency (Radio Frequency: hereinafter also referred to as “RF”) signal by an AGC (Automatic Gain Control) circuit or the like is known (for example, Patent Documents). 1-4.)
In such a radio receiving apparatus, the received radio frequency signal is frequency-converted to an intermediate frequency (hereinafter also referred to as “IF”) signal, and the signal processing unit performs signal processing on the IF signal. Is common. When the IF signal is processed by the signal processing unit, the signal level of the IF signal is preferably a predetermined constant level.

Therefore, the signal processing unit adjusts the signal level of the IF signal to a predetermined constant level based on the signal level of the IF signal frequency-converted from RF. For example, the signal processing unit calculates an average value of the IF signal, and adjusts the signal level of the IF signal to a predetermined constant level based on the calculated average value.
Japanese Patent Laid-Open No. 10-271054 Japanese Patent Laid-Open No. 11-312938 JP 2001-69066 A JP 2002-176411 A

  However, if the signal level of the frequency-converted IF signal changes unstably, there is a problem that the signal level of the IF signal cannot be properly adjusted to a predetermined constant level based on the IF signal.

On the other hand, if the signal level of the IF signal is adjusted after the signal level of the IF signal is stabilized, there is a problem that the responsiveness decreases.
Accordingly, it is conceivable to stabilize the signal level of the IF signal by performing attenuation on the RF signal based on the signal level of the received RF signal and quickly converging the RF signal.

  However, if the level of the RF signal that determines whether or not the RF signal is attenuated by the attenuator is near the threshold, and the level of the RF signal fluctuates at that time, it is appropriately determined that the attenuation by the attenuator is performed. There are things that cannot be done.

  For example, if the signal level is erroneously determined to be greater than or equal to the threshold value due to the occurrence of noise in the vicinity of the threshold value, the signal level of the IF signal fluctuates because attenuation by the attenuator is performed even though attenuation is not necessary. The signal may not converge quickly.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a radio receiving apparatus that quickly and appropriately stabilizes the signal level of the intermediate frequency signal.

According to the first to fifth aspects of the present invention, the signal level of the radio frequency signal is in a predetermined range that is equal to or higher than the first predetermined level in a state where the signal level of the intermediate frequency is lower than the second predetermined level. If the signal level of the radio frequency signal is within a predetermined range at a predetermined second clock after the first clock, the attenuator is held in an attenuation operation state in which the radio frequency signal is attenuated. Can be converged to output. Thereby, the signal level of the intermediate frequency signal can be quickly stabilized. Each of the first clock and the second clock may be one clock or a plurality of clocks.

  Further, even if the attenuation with respect to the radio frequency signal is tentatively determined in the first clock due to noise or the like in the vicinity of the threshold of the predetermined range, if the signal level of the radio frequency signal deviates from the predetermined range in the predetermined second clock after the first clock. Hold the attenuator in a non-attenuating operating state that does not perform attenuation on the radio frequency signal. Thereby, it is possible to prevent erroneous attenuation of the radio frequency signal due to the influence of noise or the like generated in the radio frequency signal. As a result, the intermediate frequency signal can be properly stabilized.

According to the second aspect of the present invention, the first hold means holds the attenuator in the attenuation operation state or the non-attenuation operation state in the second clock before the signal level of the intermediate frequency signal becomes equal to or higher than the second predetermined level. If the signal level of the intermediate frequency signal does not become equal to or higher than the second predetermined level before a predetermined time elapses, the hold state for the attenuator is released.

The fact that the signal level of the intermediate frequency signal does not become the second predetermined level or more after a predetermined time has passed since the operation state of the attenuator is held means that the radio frequency signal of an appropriate signal level is not received. Represents. Therefore, in such a case, it is desirable to release the hold state for the attenuator after a predetermined time has passed, as in the second aspect of the invention.

On the other hand, if the signal level of the intermediate frequency signal until a predetermined time elapses after holding the operating state of the attenuator in the attenuation operation state is lower than the second predetermined level after becoming equal to or higher than the second predetermined level, Alternatively, when the signal level of the intermediate frequency signal falls below the second predetermined level after the second hold means holds the attenuator in the non-attenuating operation state, a radio frequency signal having an appropriate signal level is received. Represents that. In such a case, it is desirable to release the hold state for the attenuator after the signal level of the intermediate frequency signal has dropped below the second predetermined level, as in the second aspect of the invention.

According to the third aspect of the present invention, the first clock and the second clock are continuous.
As a result, when the signal level of the radio frequency signal continues within a predetermined range in the continuous first clock and second clock, the attenuator is held in the attenuation operation state. On the other hand, if the radio frequency signal fluctuates discontinuously due to the influence of noise etc. near the threshold value in the predetermined range, the signal level of the radio frequency signal will not continue to be in the predetermined range, so the attenuator is held in the non-attenuating operation state it can. As a result, it is possible to prevent the attenuator from being erroneously held in the damping operation state.

According to the invention described in claim 4, the first clock and the second clock are separated from each other by a predetermined number of clocks.
Thereby, for example, when the radio frequency signal fluctuates periodically, the signal level of the radio frequency signal periodically falls within a predetermined range by separating the first clock and the second clock by the number of clocks corresponding to the cycle. The attenuator can be held in the damped operating state.

  On the other hand, when the signal level of the radio frequency signal does not periodically fall within the predetermined range, the attenuator can be held in the non-attenuating operation state. As a result, it is possible to prevent the attenuator from being erroneously held in the damping operation state.

  According to the fifth aspect of the present invention, the radio frequency signal is a signal according to an Orthogonal Frequency Division Multiplexing (OFDM) system. In the orthogonal frequency division multiplexing method, since a large number of subcarriers are superimposed, the signal level of the received radio frequency signal has a large peak and the signal level is not constant.

  Therefore, in the receiving device that receives the radio frequency signal of the orthogonal frequency division multiplexing system having such characteristics, the signal level of the intermediate frequency signal can be quickly and appropriately adjusted by performing the attenuation process described in claim 1. Can be stabilized.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A wireless receiver 10 according to an embodiment of the present invention is shown in FIG.
(Wireless receiver 10)
The radio receiving apparatus 10 of this embodiment includes a receiving antenna 12, an amplifier 14, power detectors 20 and 28, a comparator 22, variable attenuators 24 and 30, a frequency converter 26, a control circuit 40, and the like. A radio frequency (RF) signal of the type is received.

  The power detector 20 and the comparator 22, the variable attenuator 24, the frequency converter 26, the power detector 28, and the control circuit 40 are respectively “radio frequency signal level determining means”, “attenuator”, It corresponds to “frequency conversion means” and “intermediate frequency signal level determination means”. The control circuit 40 corresponds to “attenuation provisional deciding means”, “first hold means”, “second hold means”, and “hold release means” described in the claims.

The power detector 20 detects the power of an RF signal received by the receiving antenna 12 and amplified by an amplifier 14 such as an LNA (Low Noise Amplifier) and outputs it as an RF-RSSI (RF-Received Signal Strength Indicator) signal. . The comparator 22 compares the RF-RSSI signal with a first predetermined level (TH1 in FIG. 2) preset for the RF signal. The COMP signal that is the output of the comparator 22 is “H” when the signal level of the RF-RSSI signal is equal to or higher than TH (Threshold) 1 which is a predetermined range, and the signal level of the RF-RSSI signal is lower than TH1. Becomes 'L'.

  In the present embodiment, for simplification of description, the comparator 22 will be described as a configuration that compares the RF-RSSI signal, which is the signal level of the RF signal, with one TH1. On the other hand, the comparator 22 may be configured to compare a plurality of signal levels with the RF-RSSI signal and output a plurality of COMP signals.

  The variable attenuator 24 attenuates the RF signal received by the receiving antenna 12 and amplified by the amplifier 14 based on an RF-ATT (RF-Attenuator) signal output from the control circuit 40. When the RF-ATT signal is 'H', the RF signal is attenuated, and when the RF-ATT signal is 'L', the RF signal is not attenuated.

  The comparator 22 compares a plurality of signal levels with the RF-RSSI signal and outputs a plurality of COMP signals. The control circuit 40 outputs a plurality of RF-ATT signals based on the plurality of COMP signals. If so, the variable attenuator 24 may be configured to perform attenuation on the RF signal in multiple stages according to the signal level of the RF signal.

The frequency converter 26 converts the RF signal into an IF signal by mixing the RF signal that has passed through the variable attenuator 24 with a local oscillation signal having a frequency corresponding to the carrier frequency.
The power detector 28 detects the power of the IF signal that is the output signal of the frequency converter 26 and outputs it as an IF-RSSI signal.

The variable attenuator 30 adjusts the signal level of the IF signal based on the IF-ATT signal output from the control circuit 40, and outputs the IF signal to the control circuit 40 with a predetermined constant level.
The control circuit 40 includes a CPU, a ROM, a RAM, a flash memory, and the like. For an IF signal that has passed through the variable attenuator 30 and has been adjusted to a predetermined constant level, demodulation, extraction of a baseband signal, etc. Perform the process.

The control circuit 40 outputs an RF-ATT signal that controls attenuation of the RF signal by the variable attenuator 24 based on the COMP signal that is an output signal of the comparator 22.
Further, the control circuit 40 outputs an IF-ATT signal that controls attenuation of the IF signal by the variable attenuator 30 based on the IF-RSSI signal that is an output signal of the power detector 28.

When the IF-RSSI signal becomes equal to or higher than a second predetermined level (TH2 in FIG. 2) at which the receiving antenna 12 can detect that the RF signal has been received, the control circuit 40 sets RX_CARRIER (see FIG. 2) to “H”. To do. As shown in FIG. 2, the control circuit 40 is based on an average value obtained by averaging the signal levels of the IF-RSSI signal after a predetermined time has elapsed since the IF_RSSI signal rises and the RX_CARRIER signal becomes 'H'. An IF-ATT signal for adjusting the attenuation rate by the variable attenuator 30 is generated. Waiting until a predetermined time elapses after the IF-RSSI signal rises avoids an unstable state of the rise of the IF-RSSI signal, and the IF-RSSI signal in a stable state without fluctuation of the signal level of the IF-RSSI signal. This is to calculate the average value of.

The control circuit 40 functions as the following units according to a control program stored in the ROM or flash memory of the control circuit 40.
(Temporary damping means)
As shown in (A), (B), (C), and (D) of FIG. 3, the control circuit 40 sets the first clock (CLK1) at which the COMP signal becomes “H” while RX_CARRIER is “L”. , Provisional determination of attenuation of the RF signal by the variable attenuator 24 is made.

(First hold means)
In a state in which the attenuation of the RF signal by the variable attenuator 24 is tentatively determined, as shown in FIGS. 3A and 3B, in the second clock (CLK2) continuous to the first clock (CLK1), If the COMP signal is 'L', the control circuit 40 determines whether the RF signal is at a signal level near TH1, or that the COMP signal becomes 'H' at the first clock is due to noise, Alternatively, it is determined that the signal level of the RF signal is an instantaneous peak value, and the RF-ATT signal is temporarily set to “L” and held. As a result, the variable attenuator 24 is held in a non-attenuating operating state in which attenuation for the RF signal is not performed.

  On the other hand, as shown in (C) and (D) of FIG. 3, if the COMP signal continues to be “H” in the second clock (CLK2) continuous to the first clock (CLK1), the control circuit 40 It is determined that the signal level of the RF signal exceeds TH1 and is relatively high, and the RF-ATT signal is temporarily set to “H” and held. As a result, the variable attenuator 24 is held in an attenuation operation state in which attenuation for the RF signal is performed.

(Second hold means)
As shown in FIG. 3E, the control circuit 40 determines that the signal level of the RF signal is relatively smaller than TH1 if RX_CARRIER becomes 'H' before the operating state of the variable attenuator 24 is held. The RF-ATT signal is set to “L” and held. As a result, the variable attenuator 24 is held in a non-attenuating operating state in which attenuation for the RF signal is not performed.

(Hold release means)
As shown in FIG. 3A, when the COMP signal becomes “H” in the first clock and the COMP signal becomes “L” in the second clock, the RF-ATT signal is temporarily held at “L”. When RX_CARRIER becomes “H” before a predetermined period T elapses, the COMP signal becomes “H” in the first clock, and the COMP signal becomes “L” in the second clock. It is determined that the signal level of the RF signal is in the vicinity of TH1, or because of the influence of noise or an instantaneous peak value. In this case, the control circuit 40 determines that attenuation with respect to the RF signal is unnecessary, and continues the state in which the RF-ATT signal is held at “L”. Thereby, the non-attenuating operation state by the variable attenuator 24 is continued.

  Further, as shown in FIG. 3C, the COMP signal continuously becomes “H” in the first clock and the second clock, and the RF-ATT signal is temporarily held at “H”, and then a predetermined period T When RX_CARRIER becomes 'H' before the time elapses, the control circuit 40 indicates that the COMP signal becomes 'H' in the first clock and the second clock because of noise and an instantaneous peak value, It is determined that this is a result of receiving an RF signal having a relatively large signal level exceeding TH1. In this case, the control circuit 40 determines that attenuation with respect to the RF signal is necessary, and continues to hold the RF-ATT signal at 'H'. Thereby, the damping operation state by the variable attenuator 24 is continued.

  Then, as shown in FIGS. 3A, 3C, and 3E, when RX_CARRIER is changed from 'H' to 'L' while the RF-ATT signal is held at 'L' or 'H', The control circuit 40 determines that the reception of the RF signal is completed, and cancels the hold state of the RF-ATT signal. Thereby, the operating state of the held variable attenuator 24 is released.

  In (A), (C), and (E) of FIG. 3, the control circuit 40 determines that an RF signal having an appropriate signal level is received, so RX_CARRIER changes from “H” to “L”. To cancel the hold state of the RF-ATT signal.

  On the other hand, as shown in FIGS. 3B and 3D, RX_CARRIER remains “L” even after a predetermined period T has elapsed since the RF-ATT signal was held at “L” or “H”. If the signal does not become “H”, the control circuit 40 causes the COMP signal to become “H” in the first clock and the COMP signal to become “L” or “H” in the second clock because of noise or instantaneous. Judgment is due to the influence of the peak value. In this case, the control circuit 40 determines that attenuation of the RF signal is unnecessary because it has not received the RF signal of an appropriate signal level. In this case, the control circuit 40 cancels the state where the RF-ATT signal is held at 'L' or 'H' after a predetermined period T has elapsed. Thereby, the non-attenuating operation state or the attenuation operation state by the variable attenuator 24 is released.

(Attenuation control for RF signal)
Next, attenuation control for the RF signal will be described based on the control routine of FIG. In the flowchart of FIG. 4, “S” represents a step.

  In S300, the control circuit 40 sets the signal level of the RF-ATT signal to the initial state 'L'. In step S <b> 302, the control circuit 40 determines whether RX_CARRIER is “H”.

  When RX_CARRIER is 'L' instead of 'H' (S302: No), the control circuit 40 temporarily determines the hold state of the RF-ATT signal based on the value of the COMP signal in S304.

If the COMP signal is “L” in S304, the control circuit 40 determines that the RF signal has not been received, and proceeds to S300.
If the COMP signal is “H” in S304, the control circuit 40 determines that there is a possibility of receiving an RF signal having a signal level equal to or higher than TH1. In S <b> 306, the control circuit 40 determines the hold state of the RF-ATT signal based on the value of the COMP signal in the second clock continuous to the first clock in which the COMP signal becomes “H” in S <b> 304.

  If the COMP signal is 'H' in S306, the control circuit 40 temporarily holds the RF-ATT signal at 'H'. As a result, the variable attenuator 24 is temporarily held in the damping operation state.

  If the COMP signal is 'L' in S306, the control circuit 40 indicates that the RF signal is at a signal level near TH1, or that the COMP signal becomes 'H' at the first clock is due to noise. Alternatively, it is determined that the signal level of the RF signal is an instantaneous peak value, and the RF-ATT signal is temporarily held at 'L' in S310.

  In S <b> 312 and S <b> 314, the control circuit 40 holds the RF-ATT signal at “H” or “L”, and RX_CARRIER becomes “H” until a predetermined period T (see FIG. 3) set in the timer elapses. Determine whether it will be.

  In a state where the RF-ATT signal is held at “H” or “L” in S312 and S314, if RX_CARRIER does not become “H” before the predetermined period T elapses, the control circuit 40 determines that the COMP signal is not received in S304. It is judged that “H” is due to the influence of noise and instantaneous peak value. Then, when the predetermined period T has elapsed in S314, the control circuit 40 proceeds to S300, releases the hold state of the RF-ATT signal, and sets the RF-ATT signal to 'L'.

  In S312, S314, when RX_CARRIER becomes 'H' before the predetermined period T elapses while the RF-ATT signal is held at 'H' or 'L' (S312: Yes), the control circuit 40 in S318. Determines whether RX_CARRIER changes from 'H' to 'L'.

  When RX_CARRIER becomes 'L' in S318 (S318: No), the control circuit 40 proceeds to S300, releases the hold state of the RF-ATT signal, and sets the RF-ATT signal to 'L'.

  When RX_CARRIER becomes “H” in S302 before the RF-ATT signal is held to “H” or “L”, the control circuit 40 indicates that the signal level of the received RF signal is relatively smaller than TH1. In step S316, the RF-ATT signal is set to “L” and held. As a result, the variable attenuator 24 is held in a non-attenuating operating state in which attenuation for the RF signal is not performed.

  As a result of RX_CARRIER being 'H' in S302, if RX_CARRIER is changed from 'H' to 'L' in S318 while the RF-ATT signal is held at 'L' in 8S316 (S318: No), the control circuit 40 Shifts the processing to S300, cancels the hold state of the RF-ATT signal, and sets the RF-ATT signal to 'L'.

  In the present embodiment described above, the variable attenuator 24 is held in an attenuation operation state in which attenuation of the RF signal is performed if the signal level of the RF signal is a predetermined range equal to or higher than TH1 in the continuous first and second clocks. Therefore, the RF signal can be quickly converged and output to the frequency converter 26 to obtain the IF signal. Thereby, the control circuit 40 can calculate the average of the stable IF signal quickly, and can adjust the attenuation rate with respect to the IF signal by the variable attenuator 30 based on the calculated average value. As a result, the signal level of the IF signal can be quickly adjusted to a constant level.

  Further, even if attenuation for the RF signal is tentatively determined in the first clock due to noise or the like in the vicinity of TH1, if the signal level of the RF signal is lower than TH1 in a predetermined second clock after the first clock, attenuation for the RF signal is performed. The variable attenuator 24 is held in a non-attenuating operation state in which no operation is performed. As a result, it is possible to prevent erroneous attenuation of the RF signal due to the influence of noise or the like generated in the RF signal. As a result, the signal level of the IF signal can be properly stabilized.

  In addition, when receiving an RF signal having a large peak and a non-constant signal level as in the OFDM system, the signal of the IF signal is obtained by performing attenuation processing on the RF signal of the present embodiment. The level can be adjusted quickly and appropriately to a certain level.

[Other Embodiments]
In the above embodiment, the first clock and the second clock are continuous clocks. On the other hand, the first clock and the second clock may be clocks separated by a predetermined number of clocks.

  Thereby, for example, when the RF signal fluctuates periodically, the first clock and the second clock are separated by the number of clocks corresponding to the period, thereby being attenuated when the signal level of the RF signal periodically falls within a predetermined range. Can be held in a damped operating state.

  On the other hand, when the signal level of the RF signal does not periodically fall within the predetermined range, the attenuator can be held in the non-attenuating operation state. As a result, it is possible to prevent the attenuator from being erroneously held in the damping operation state.

  In the above-described embodiment, the present invention is applied to a radio receiving apparatus for OFDM RF signals. On the other hand, if it is a wireless reception device that converts a received RF signal into an IF signal, the signal level of the IF signal is promptly changed regardless of the RF signal of any method, not limited to the OFDM method. And it can be properly stabilized.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The block diagram which shows the radio | wireless receiving apparatus by this embodiment. The characteristic view which shows the electric power detection of RF signal and IF signal. The term chart which shows the attenuation process with respect to RF signal. The flowchart which shows the attenuation process routine with respect to RF signal.

Explanation of symbols

10: wireless receiver, 20: power detector (radio frequency signal level determining means), 22: comparator (radio frequency signal level determining means), 24, 30: variable attenuator, 26: frequency converter (frequency converting means) , 28: power detector (intermediate frequency signal level determination means), 40: control circuit (intermediate frequency signal level determination means, temporary attenuation determination means, first hold means, second hold means, hold release means)

Claims (5)

An attenuator for attenuating the received radio frequency signal;
Frequency conversion means for converting the radio frequency signal that has passed through the attenuator into an intermediate frequency signal;
Radio frequency signal level determination means for determining that the attenuation by the attenuator is within a predetermined range when the signal level of the radio frequency signal is equal to or higher than a first predetermined level before frequency conversion by the frequency conversion means; ,
Intermediate frequency signal level determining means for determining whether a signal level of the intermediate frequency signal is equal to or higher than a second predetermined level indicating that the radio frequency signal is received;
In the first clock when the signal level of the radio frequency signal falls within the predetermined range in a state where the signal level of the intermediate frequency signal is lower than the second predetermined level , attenuation of the radio frequency signal by the attenuator is performed. Attenuation provisional deciding means for tentative decision;
If the signal level of the radio frequency signal is within the predetermined range at a predetermined second clock after the first clock, the attenuator is held in an attenuation operation state for performing attenuation on the radio frequency signal, and the second First hold means for holding the attenuator in a non-attenuating operating state when a signal level of the radio frequency signal deviates from the predetermined range in the clock;
When the signal level of the intermediate frequency signal becomes equal to or higher than the second predetermined level before the first hold means holds the attenuator in the attenuation operation state or the non-attenuation operation state, the attenuator is operated in the non-attenuation operation. Second holding means for holding in a state;
A radio receiving apparatus comprising: The signal level of the intermediate frequency signal is set to the second predetermined level until a predetermined time elapses after the first hold means holds the attenuator in the attenuation operation state or the non-attenuation operation state in the second clock. Or the signal level of the intermediate frequency signal is the second predetermined time after the predetermined time elapses after the first hold means holds the attenuator in the attenuation operation state in the second clock. than the second predetermined level after becoming more levels or reduced, or the second holding means the attenuator the undamped operating said state from the hold to an intermediate frequency signal signal level is the second Patent of the drops below a predetermined level, further comprising a hold release means for releasing the hold state of the attenuator Radio receiver according to claim 1,.   The radio reception apparatus according to claim 1, wherein the first clock and the second clock are continuous.   The radio reception apparatus according to claim 1, wherein the first clock and the second clock are separated from each other by a predetermined number of clocks.   The radio reception apparatus according to claim 1, wherein the radio frequency signal is a signal based on an orthogonal frequency division multiplexing system.

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