JP2007235804A - Reception field strength detection circuit and reception field strength detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reception field strength detection circuit and reception field strength detection method thereof for a diversity receiver or the like which requires a high-accuracy and high-speed antenna selection means. <P>SOLUTION: A low-pass filter 4a is provided only in detectors 2c, 2d which operates with a weak electric field. Thus, since a baseband modulation signal is not residual in the weak electric field where a reception field strength becomes lower than or equal with a set threshold value, the reception field strength can be accurately detected and increase in frequency of channel switching caused by a malfunction of antenna selection, erroneous detection of phasing or erroneous recognition of high-speed movement can be prevented. Furthermore, a transient response time of reception field strength is also shorter than that of the conventional reception field strength, thereby reducing an antenna selection time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio receiver used for mobile communication with fading, and more particularly to a received electric field strength detection circuit and a received electric field strength detection method.

  In recent years, diversity reception has been known as a means for reducing the influence of fading in wireless communication in a mobile communication wireless device such as a mobile phone or a mobile phone in which deep fading due to movement of the own station or a partner station occurs. . As the most general diversity receiver, there has been proposed an antenna switching diversity receiver that has a single receiving unit and a plurality of antennas and receives the antennas by appropriately switching them under appropriate conditions.

  Hereinafter, the configuration of the diversity receiver will be described with reference to FIG. In FIG. 31, reference numerals 101 and 102 denote antennas, and reference numeral 103 denotes an antenna switch for selectively outputting the antenna 101 or 102. A reception wireless unit 104 receives a desired reception signal via the antenna 101 or 102 connected by the antenna switch 103. In the wireless reception unit 104, the received signal is amplified by the low noise amplifier 9 and input to the mixer 8. Then, the received signal is converted into the first intermediate frequency band by the mixer 8, and only the first desired signal is input to the mixer 6 by the band pass filter 7. Further, the first desired signal is converted into the second intermediate frequency band by the mixer 6, and only the second desired signal is input to the amplifier 1 a of the electric field intensity detection circuit by the band pass filter 5. The second desired signal is limiter amplified by a plurality of cascade-connected amplifiers 1a, 1b, 1c, and 1d. Reference numeral 105 denotes antenna selection means for controlling the antenna switch 103 when the received electric field strength is below a preset switching threshold, and switching to the antenna 102 if the current antenna 101 is connected. If 102 is connected, the antenna 101 is switched.

Hereinafter, the configuration of a conventional reception field strength detection circuit will be described with reference to FIG. As a receiving apparatus for wireless communication or the like, there is a superheterodyne system that demodulates a received signal input from an antenna after converting it to an intermediate frequency band. In FIG. 5, a plurality of amplifiers 1a, 1b, 1c, and 1d are provided in the reception radio section after the intermediate frequency band in order to amplify the intermediate frequency signal. The reception electric field strength detection circuit 10 includes detectors 2a, 2b, 2c, and 2d that detect reception signal levels to the respective amplifiers 1a, 1b, 1c, and 1d. The adder 3 combines the detection signals of the detectors 2a, 2b, 2c, and 2d, thereby obtaining a received electric field strength detection signal. This received electric field strength detection signal is smoothed by the low-pass filter 4 and then input to the antenna selection means 105.
The

  Hereinafter, a circuit configuration for detecting received electric field strength, particularly a detector for detecting a received signal level, will be described with reference to FIG. By cascading a plurality of amplifiers 1a, 1b, 1c, 1d, the received signals are amplified by the amplifiers 1a, 1b, 1c, 1d. The output signals of the amplifiers 1a, 1b, 1c and 1d are detected by the detectors 2a, 2b, 2c and 2d. The detectors 2a, 2b, 2c, and 2d have the same configuration, and each includes four transistors A to D, a current source, and a resistor. 4 a is a capacitor constituting the low-pass filter 4.

  When the received electric field strength is a weak electric field, a received signal having a very low level is input to the amplifier 1a. 7, 8, 9, and 10 show the base voltage waveforms of the transistors A to D constituting the detectors 2a, 2b, 2c, and 2d. As shown in FIGS. 7, 8, 9, and 10, the received signal is gradually amplified by the amplifiers 1a, 1b, 1c, and 1d, and the received signal is output as a limiter by the amplifier 1d. Detectors 2a, 2b, 2c, and 2d are provided at the outputs of the amplifiers 1a, 1b, 1c, and 1d, respectively. The emitters of the transistors A to D are common, and a constant current flows. The bases of the transistors A and D receive the differential signal output from the amplifier, the bases of the transistors B and C are common, and the differential signals output from the amplifier are added to a constant midpoint potential. The collectors of the transistors B and C are common, and the collectors of the transistors A and D are also common.

  In the detector 2a, since the differential signal input to the bases of the transistors A and D is small, the transistors A, B, C, and D maintain an equilibrium state, and the constant current is evenly distributed to the transistors A, B, C, and D. Since the current flows are divided, the added current of the detector 2a is as shown in FIG. In the detector 2d, the differential signal of the amplifier 1d output as a limiter is input to the transistors A and D by a plurality of cascaded amplifiers 1a, 1b, 1c, and 1d. When the base potential of the transistor A is high and the base potential of the transistor D is low, all of the constant current flows through only the transistor A among the transistors A, B, C, and D. Further, when the base potential of the transistor D is high and the base potential of the transistor A is low, all of the constant current flows through only the transistor D among the transistors A, B, C, and D. Since the collectors of the transistors A and D are common, the added current of the detector 2d is as shown in FIG. As shown in FIGS. 12 and 13, the output current waveforms of the intermediate detectors 2b and 2c are intermediate waveforms of FIGS.

  When the received electric field strength is a medium electric field, the input / output waveforms of the detectors 2a, 2b, 2c, 2d are as shown in FIGS. When the received electric field strength is a strong electric field, the input / output waveforms of the detectors 2a, 2b, 2c, 2d are as shown in FIGS. As the received electric field strength increases, the amplifier in the previous stage is output as a limiter.

  The operating characteristics of the detector when the received electric field strength is weak (FIGS. 7 to 14), the operating characteristics of the detector when the received electric field strength is medium (FIGS. 15 to 22), and the received electric field strength The relationship between the received signal level and the received electric field strength detection signal will be described with reference to the operating characteristics (FIGS. 23 to 30) of the detector in the case of a strong electric field.

  When the received signal level is small, differential signals as shown in FIGS. 7 to 10 are output from the amplifiers, and the detection signals are as shown in FIGS. There is almost no detection signal at the detector 2a, the detection signal at the detector 2b is small, the detection signal at the detector 2c is large, and the detection signal at the detector 2d becomes a limiter waveform. The received electric field strength detection signal to which the respective detection signals are added is small, indicating that a small received signal level is input.

  When the reception signal level is medium, differential signals as shown in FIGS. 15 to 18 are output from the respective amplifiers, and the detection signals are as shown in FIGS. 19 to 22. The detection signal at the detector 2a is small, the detection signal at the detector 2b is large, and the detection signals at the detectors 2c and 2d have a limiter waveform. The received electric field strength detection signal to which each detection signal is added is medium, indicating that a medium reception signal level is input.

  When the received signal level is high, differential signals as shown in FIGS. 23 to 26 are output from the amplifiers, and the detection signals are as shown in FIGS. 27 to 30. The detection signal at the detector 2a is large, and the detection signals at the detectors 2b, 2c, and 2d are limiter waveforms. The received electric field strength detection signal to which the respective detection signals are added is large, indicating that a large received signal level is input.

That is, the relationship between the received signal level and the received electric field strength detection signal is proportional as shown in FIG. In FIG. 32, solid lines with reference numerals 2 a to 2 d indicate the operating characteristics of the detectors 2 a, 2 b, 2 c, 2 d, and long broken lines with reference numeral 3 indicate the operating characteristics of the adder 3. A short broken line indicates a threshold for switching the antenna. By sending a received electric field strength detection signal proportional to the received signal level to the baseband unit, the received signal level can be recognized in the baseband unit, and antenna selection and diversity reception are possible.
JP 2000-295150 A Japanese Patent Laid-Open No. 7-250004

  In the configuration of the conventional received electric field strength detection circuit, if the attenuation amount of the low-pass filter is not sufficient, the baseband modulation signal remains, so that the received electric field strength cannot be detected correctly.

  Hereinafter, in the conventional example, operation characteristics when the received electric field intensity is not correctly detected will be described with reference to FIG. FIG. 34A is a diagram showing the relationship between the received electric field strength and the moving speed. In the diversity receiver, an operation of switching the antenna is performed when the received electric field strength is equal to or lower than a preset threshold value. However, if the attenuation of the low-pass filter is not sufficient, the residual amount of the baseband modulation signal will increase, so if the received field strength detection signal is near the threshold value, an antenna selection malfunction will occur and antenna switching will occur. The number of times increases.

  In addition, the receiving device of the mobile communication device recognizes the moving speed based on the fading cycle of the received electric field strength. When the fading cycle is short, it is determined that the communication device is moving at high speed, and when the fading cycle is long, it is determined that the communication device is moving at low speed. For example, the fading period when an 800 MHz communication device is moved at a speed of 100 km per hour is calculated as follows.

Communication device wavelength = speed of light / communication device frequency
= 3 × 10 ⁸ [m / sec] / 800 [MHz] = 37.5 cm
Fading period = wavelength of communication equipment / moving speed
= 37.5 [cm] / 100 [km / h] = 0.0135 sec
When the residual amount of the baseband modulation signal is large, the fluctuation due to the residual component of the baseband modulation signal that appears in the received electric field strength is erroneously determined as a fading period, and the communication device is erroneously recognized as moving at high speed. For this reason, a communication device misrecognized as moving at high speed increases the number of channel switching in order to search for a new base station.

  As described above, if the attenuation amount of the low-pass filter is not sufficient, the receiving device of the mobile communication device causes an increase in the number of channel switching due to an erroneous operation of antenna selection, erroneous detection of fading period, or erroneous recognition of high-speed movement. Therefore, the reception quality deteriorates. Therefore, in the low-pass filter, it is necessary to sufficiently attenuate the residual amount of the baseband modulation signal that appears in the received electric field strength to a desired value.

  Hereinafter, the operation characteristics when the received electric field intensity is correctly detected in the conventional example will be described with reference to FIG. Since the attenuation of the low-pass filter is sufficient, the residual amount of the baseband modulation signal is small, so even if the received electric field strength is close to the threshold, malfunction of antenna selection, false detection of fading period, high speed An increase in the number of channel switching due to misrecognition of movement can be prevented. However, the attenuation amount of the low-pass filter and the transient response time of the received electric field strength are in a trade-off relationship, and the transient response time becomes longer if sufficient attenuation is ensured.

  Here, FIG. 34A and FIG. 35A will be described.

  FIGS. 34 (a) and 35 (a) show the fading characteristics of the receiver. The horizontal axis represents the moving speed, and the vertical axis represents the received electric field strength. With the horizontal axis as the moving speed, the fading cycle is recognized when the received electric field strength detection signal is below the threshold value. Specifically, it is determined that the mobile communication device is moving at a low speed because the fading cycle is long (the number of times that the received electric field strength detection signal is equal to or less than the threshold value is small). Further, it is determined that the mobile communication device is moving at high speed because the fading cycle is short (the number of times the received electric field strength detection signal is equal to or less than the threshold value). When the mobile communication device moves at a high speed (for example, on a bullet train), the mobile communication device moves away from the currently receiving base station, so that the reception quality deteriorates and the call is likely to be disconnected. Therefore, by recognizing the moving speed, the mobile communication device starts searching for a better base station that is closer to the user and prevents deterioration in reception quality.

  Next, FIG. 34 (b) and FIG. 35 (b) will be described.

  FIGS. 34 (b) and 35 (b) are diagrams for explaining the antenna branch selection operation of the receiver, with the horizontal axis representing time and the vertical axis representing received field strength. The diversity receiver has two antennas, a whip antenna and a built-in antenna. For example, the antenna 101 is a whip antenna, and the antenna 102 is a built-in antenna. With the horizontal axis as time, the mobile communication device performs antenna branch selection at the time from when the power is turned on until reception is started. In the antenna branch selection, the reception electric field strength at the antenna 101 is detected, the antenna selection is switched, the reception electric field strength is also detected at the antenna 102, and an antenna having a larger reception electric field strength is selected to achieve good reception. It means that reception starts with quality. FIG. 34 (b) and FIG. 35 (b) show changes in the received electric field strength at that time.

  Hereinafter, response characteristics in the case where the conventional received electric field strength is correctly detected will be described with reference to FIG. In the diversity receiver, it is desirable that the antenna switching time for antenna selection is as short as possible. Especially when the power is turned on, a fast antenna selection means is required to start reception with the antenna with the stronger reception field strength, and the time required for antenna selection increases as the transient response time of the reception field strength decreases. To do. However, when the low-pass filter is sufficiently attenuated, the transient response time of the received electric field strength becomes long, and the antenna selection at the time of power-on is not in time, and a reception error occurs.

In the case of FIG. 34B, compared with FIG. 35B, the response time of the rising and falling of the received electric field strength is short, and the antenna branch selection can be completed sufficiently earlier than the antenna selection switching timing. However, as described above, erroneous detection of the received electric field strength occurs.
In FIG. 35 (b), compared with FIG. 34 (b), the response time of the rising and falling of the received electric field strength is long and is later than the antenna selection switching timing, so that the antenna branch selection cannot be completed.

  Therefore, the present invention increases the number of times of channel switching due to erroneous operation of antenna selection below the threshold value of the received electric field strength, erroneous detection of fading period, and erroneous recognition of high-speed movement while speeding up the antenna selection time in mobile communication equipment. The purpose is to prevent.

  In order to solve the above-described problem, the received electric field strength detection circuit according to the present invention detects the output signal of a plurality of cascaded amplifiers that amplify the received signal, respectively, thereby weakening the received signal level from a strong electric field. Receives by combining the multiple detectors that detect the level of the received signal and the detection signals output from the multiple detectors in a state where the lower limit level of the received signal that can be detected decreases sequentially until the received signal level in the electric field. The first adder that outputs the electric field strength detection signal and the detection of the level of the received signal at the time of the weak electric field such that the received electric field strength detection signal is not more than a preset threshold value among the plurality of detectors. A first low-pass filter for smoothing a detection signal provided between the shared detector and the first adder;

  According to this configuration, the detection signal output from the detector sharing the detection of the level of the received signal at the time of the weak electric field is smoothed by the first low-pass filter, and the detection signal output from the other detectors Is not smoothed, so that the number of times of channel switching due to incorrect operation of antenna selection, false detection of fading period, or misrecognition of high-speed movement in the weak electric field of the received signal that is below the threshold value of the received electric field strength while speeding up the antenna selection time Can be prevented from increasing.

  In the above configuration, a filter that inputs only a desired received signal of the received signals output from the previous stage amplifier to the next stage amplifier between two consecutive stages of the amplifiers of the plurality of stages. It is preferable to arrange.

  Moreover, in the said structure, it is preferable to provide the 2nd low-pass filter which smoothes the output signal of a 1st adder.

  According to this configuration, by providing the second low-pass filter, the baseband modulation signal does not remain in the received electric field strength detection signal, and the received electric field strength can be detected with high accuracy.

  In the above configuration, there are at least two detectors that share the detection of the level of the received signal in the weak electric field such that the received electric field strength detection signal is equal to or lower than the set threshold value, and the first low frequency band The pass filter is provided between the first adder and at least two detectors that share the detection of the level of the received signal in the weak electric field such that the received electric field strength detection signal is equal to or less than the set threshold value. It is preferable that the attenuation amount of the first low-pass filter corresponding to the detector that is provided individually and shares the detection of the level of the received signal with a weaker electric field is larger.

  Further, in the above configuration, there are at least two detectors that share the detection of the level of the received signal in the weak electric field such that the received electric field strength detection signal is equal to or less than the set threshold value, and the received electric field strength detection signal A second adder that adds detection signals output from at least two detectors that share the detection of the level of the received signal at the time of a weak electric field such that is less than a set threshold value, The output signal of the adder is preferably supplied to the first low-pass filter.

  In the above configuration, the first stage amplifier of the plurality of stages includes a plurality of antennas and an antenna switching unit that switches received signals from the plurality of antennas and supplies the received signals to the first stage amplifier. It is preferable to switch the antenna switch according to the output of the adder.

  The received electric field strength detection method of the present invention amplifies a received signal in a plurality of stages, generates a detection signal at each stage by detecting the amplified signal at each stage, and adds and combines the detection signals at each stage. A reception field strength detection method for generating a reception field strength detection signal by using a detection signal corresponding to a received signal level in a weak electric field such that the reception field strength detection signal is equal to or lower than a preset threshold value Is added after smoothing.

  According to this method, the detection signal corresponding to the level of the reception signal at the time of the weak electric field such that the reception electric field strength detection signal is equal to or lower than a preset threshold is added after being smoothed, and the other detection signals are detected. Signals are added without being smoothed, so that the antenna selection time is made fast, and the weak signal of the received signal that is below the threshold value of the received electric field strength causes malfunctions in antenna selection, false detection of fading period, and false recognition of high-speed movement. The increase in the number of channel switching due to can be prevented.

  The reception antenna selection method of the present invention detects the reception field strength of each of the plurality of antennas using the antenna selection step of selecting any one of the reception signals of the plurality of antennas and the reception field strength detection method described above. The received electric field strength detection step, the comparison step for comparing the received electric field strength of each of the plurality of antennas detected by the received electric field strength detection step, and the antenna element having the maximum received electric field strength based on the comparison result of the comparison step Selecting a received signal.

  According to this method, the same operation and effect as the received electric field strength detection method of the present invention can be obtained.

  The reception method of the present invention includes an antenna selection step of selecting any one of reception signals of a plurality of antennas, and a reception electric field that detects the reception field strength of each of the plurality of antennas using the reception field intensity detection method described above. An intensity detection step; a fading detection step for detecting a fading period from a change in the received electric field intensity detected by the received electric field intensity detection step; and a determination step for determining a moving speed of the communication device from the fading period detected by the fading detection step. And a switching step of switching the base station when the moving speed determined by the moving speed determining step is greater than a predetermined value, and a base station selecting step of selecting a received signal from the base station switched by the switching step.

  According to this method, the same operation and effect as the received electric field strength detection method of the present invention can be obtained.

  According to the received electric field strength detection method of the present invention, the antenna selection time is made high speed, and in the weak electric field of the received signal that is below the threshold value of the received electric field strength, the antenna selection malfunctions, the fading error detection, and the high speed movement error occur. An increase in the number of channel switching due to recognition can be prevented.

(First embodiment)
Hereinafter, a received electric field strength detection circuit and a received electric field strength detection method according to a first embodiment of the present invention will be described with reference to FIG. The reception radio unit after the intermediate frequency band includes a plurality of amplifiers 1a, 1b, 1c, and 1d, and detectors 2a, 2b, 2c, and 2d that detect received signal levels to the respective amplifiers 1a, 1b, 1c, and 1d, and , An adder 3a and a low-pass filter 4a. The number of amplifiers and detectors need not be four. The difference from the conventional example is that an adder 3a and a low-pass filter 4a are added. With this additional circuit, the detection signals of the detectors 2c and 2d, that is, the detection signal in which the reception signal whose reception electric field strength of the mobile communication device is equal to or lower than the threshold appears in the weak electric field are smoothed by the low-pass filter 4a. No baseband modulation signal remains. Accordingly, the baseband modulation signal does not remain in the received electric field strength detection signal at a level near the threshold value, and the baseband modulation signal does not fluctuate. As a result, the received electric field strength detection signal can be accurately detected at a level near the threshold. Therefore, erroneous switching can be prevented when antenna switching is performed by comparing with a threshold value. Further, there is no false detection of the fading cycle, no false detection of the moving speed of the mobile communication device, and therefore no increase in the number of channel switching.

  In addition, when the received electric field strength detection signal exceeds the threshold value and the received signal is a strong electric field, the detection signal is added as it is without being smoothed, so that a high-speed response can be realized. At this time, the received electric field strength detection signal is sufficiently higher than the threshold value, and the comparison result with the threshold value does not reverse, so there is no problem even if the received electric field strength detection signal cannot be detected with high accuracy. Basic operations other than the above are the same as in the conventional example.

  Hereinafter, the operation characteristics of the received electric field strength detection circuit will be described with reference to FIG. As the electric field strength of the received signal increases, the detector operates in the order 2d → 2c → 2b → 2a. In addition, when the received signal whose received electric field strength is below the threshold is a weak electric field, the detector 2d operates completely, the detector 2c starts operating, and the detectors 2a and 2b do not operate. The detection signals of the detectors 2c and 2d are synthesized by the adder 3a and smoothed by the low-pass filter 4a. The output signal of the low-pass filter 4a and the detection signals of the detectors 2a and 2b are combined by the adder 3 to become a received electric field strength detection signal. With the above configuration, the reception electric field strength detection circuit 10 is configured.

  Hereinafter, the operation characteristics of the received electric field strength detection according to the present invention will be described with reference to FIG. FIG. 33A is a view similar to FIGS. 34A and 35A. When the received signal whose received electric field strength of the mobile communication device is below the threshold value is a weak electric field, the detector 2d operates completely, the detector 2c starts operating, and the detectors 2a and 2b do not operate. Since the detection signals of the detectors 2c and 2d are synthesized by the adder 3a and smoothed by the low-pass filter 4a, no baseband modulation signal remains in the received electric field intensity detection signal, and the received electric field intensity is accurate. It can be detected well.

  In addition, when the received signal whose received electric field strength of the mobile communication device is equal to or greater than the threshold value is a strong electric field, the detectors 2c and 2d operate completely, and the detectors 2b and 2a also start operating. The detection signals of the detectors 2c and 2d are synthesized by the adder 3a and smoothed by the low-pass filter 4a. The output signal of the low-pass filter 4a and the detection signals of the detectors 2a and 2b are combined by the adder 3 to generate a reception electric field intensity detection signal. Therefore, the baseband modulation signal is included in the reception electric field intensity detection signal. Although it remains, even if the received electric field strength cannot be detected with high accuracy, the rate of increase in the number of times of channel switching due to erroneous operation of antenna selection, erroneous detection of fading, and erroneous recognition of high-speed movement is considerably low, so there is no problem.

  Hereinafter, the response characteristic of the reception electric field strength detection of the present invention will be described with reference to FIG. FIG. 33 (b) is a view similar to FIG. 34 (b) and FIG. 35 (b). In the detectors 2c and 2d provided with the low-pass filter 4a, the residual amount of the baseband modulation signal appearing in the received electric field strength detection signal is small, and the transient response time is long. The detectors 2a and 2b not provided with the low-pass filter 4a have a large baseband modulation signal appearing in the received electric field strength and a short transient response time. There is a trade-off between the residual amount of the baseband modulation signal appearing in the received electric field strength and the transient response time. The transient response time of the received electric field strength synthesized by the adder 3 becomes shorter than the conventional received electric field strength, and the antenna selection time can be increased.

  In the case of FIG. 33B, the response time of the rising and falling of the received electric field strength is longer than that in FIG. 34B, but the antenna branch selection can be completed earlier than the antenna selection switching timing. Moreover, no erroneous detection of the received electric field intensity occurs.

  In FIG. 33 (b), compared with FIG. 35 (b), the response time of the rising and falling of the received electric field strength is short and is earlier than the antenna selection switching timing, so that the antenna branch selection can be completed.

  According to the reception field strength detection method of the reception apparatus according to the present invention, while making the antenna selection time fast, in the weak signal field of the received signal that is below the threshold value of the reception field strength, malfunction of antenna selection, fading detection error, It is possible to prevent an increase in the number of channel switching due to erroneous recognition of movement.

(Second Embodiment)
Hereinafter, a received electric field strength detection circuit and a received electric field strength detection method according to a second embodiment of the present invention will be described with reference to FIG. The reception radio section after the intermediate frequency band is a band in which only the desired reception signal among the reception signals output from the amplifiers 1a, 1b, 1c, and 1d and the previous stage amplifier 1b is input to the next stage amplifier 1c. A pass filter 5, detectors 2 a, 2 b, 2 c, and 2 d that detect received signal levels to the amplifiers 1 a, 1 b, 1 c, and 1 d, an adder 3 a, and a low-pass filter 4 a are provided. The number of stages of amplifiers and detectors need not be four, and the bandpass filter 5 does not have to be between the amplifiers 1b and 1c. The bandpass filter 5 is generally an external component such as a ceramic filter. However, in order to reduce the size of the mobile communication device and increase the integration of the receiving device, the second embodiment of the present invention uses GmC. Built in a semiconductor integrated circuit with a filter. Except that the band-pass filter 5 is provided, it is the same as in the first embodiment.

  According to the reception field strength detection method of the reception apparatus according to the present invention, while making the antenna selection time fast, in the weak signal field of the received signal that is below the threshold value of the reception field strength, malfunction of antenna selection, fading detection error, It is possible to prevent an increase in the number of channel switching due to erroneous recognition of movement. Further, by incorporating the bandpass filter 5 in the semiconductor integrated circuit with a GmC filter, it is possible to reduce the size of the mobile communication device and increase the integration of the receiving device.

(Third embodiment)
Hereinafter, a received electric field strength detection circuit and a received electric field strength detection method according to a third embodiment of the present invention will be described with reference to FIG. The reception radio section after the intermediate frequency band includes a plurality of amplifiers 1a, 1b, 1c, 1d, detectors 2a, 2b, 2c, 2d for detecting the received signal level to each amplifier, an adder 3a, and a low A pass filter 4a and a low pass filter 4b are provided. The number of amplifiers and detectors need not be four. The second embodiment is the same as the second embodiment except that the low-pass filter 4b is added to the output of the adder 3, that is, the output of the received electric field strength detection circuit 10.

  Hereinafter, the operation characteristics of the received electric field strength detection according to the present invention will be described with reference to FIG. In this embodiment, since the low-pass filter 4b is also provided at the output of the received electric field strength detection circuit 10, the baseband modulation signal does not remain in the received electric field strength detection signal, and the received electric field strength can be detected with high accuracy. Others are the same as in the first embodiment.

  Hereinafter, the response characteristic of the reception electric field strength detection of the present invention will be described with reference to FIG. In this embodiment, the attenuation amount of the low-pass filter 4b provided at the output of the received electric field strength detection circuit 10 can be reduced as compared with the conventional case. Therefore, the transient response time of the received electric field strength is also shorter than the conventional received electric field strength, and the antenna Selection time can be increased. Others are the same as in the first embodiment.

  According to the reception field strength detection method of the reception apparatus according to the present invention, while making the antenna selection time fast, in the weak signal field of the received signal that is below the threshold value of the reception field strength, malfunction of antenna selection, fading detection error, It is possible to prevent an increase in the number of channel switching due to erroneous recognition of movement.

(Fourth embodiment)
Hereinafter, a received electric field strength detection circuit and a received electric field strength detection method according to a fourth embodiment of the present invention will be described with reference to FIG. The reception radio unit after the intermediate frequency band includes a plurality of amplifiers 1a, 1b, 1c, and 1d, and detectors 2a, 2b, 2c, and 2d that detect received signal levels to the respective amplifiers 1a, 1b, 1c, and 1d, and And low-pass filters 4c and 4d. The number of amplifiers and detectors need not be four. Other configurations are the same as those of the conventional example.

  Hereinafter, the operation characteristics of the received electric field strength detection will be described with reference to FIG. The detector operates in the order of 2d → 2c → 2b → 2a. In addition, when the received signal whose received electric field strength is below the threshold is a weak electric field, the detector 2d operates completely, the detector 2c starts operating, and the detectors 2a and 2b do not operate. A low-pass filter 4 c is provided between the detector 2 c and the adder 3, and a low-pass filter 4 d is provided between the detector 2 d and the adder 3. The detector 2d operates earlier than the detector 2c, and when the received signal is a weak electric field, the detector 2d is fully operated and the detector 2c starts to operate. Therefore, the detection signal of the detector 2d Becomes dominant to the received electric field strength. Therefore, the attenuation amount of the low-pass filter 4d between the detector 2d and the adder 3 is set larger than that of the low-pass filter 4c between the detector 2c and the adder 3.

  Hereinafter, the operation characteristics of the received electric field strength detection according to the present invention will be described with reference to FIG. When the received signal whose received electric field strength of the mobile communication device is below the threshold value is a weak electric field, the detector 2d operates completely, the detector 2c starts operating, and the detectors 2a and 2b do not operate. The attenuation amount of the low-pass filter 4d between the detector 2d and the adder 3 is set larger than that of the low-pass filter 4c between the detector 2c and the adder 3, so that the received electric field strength detection signal is obtained. The baseband modulation signal does not remain further, and the received electric field strength can be detected with higher accuracy. In addition, when the received signal whose received electric field strength of the mobile communication device is equal to or greater than the threshold value is a strong electric field, the detectors 2c and 2d operate completely, and the detectors 2b and 2a also start operating. The detection signals from the detectors 2c and 2d are smoothed by the low-pass filters 4c and 4d. The output signals of the low-pass filters 4c and 4d and the detection signals of the detectors 2c and 2d are combined by the adder 3 to generate a reception field strength detection signal. Although the signal remains, even if the received electric field strength cannot be detected accurately, there is no problem because the rate of increase in the number of channel switching due to erroneous antenna selection, fading error detection, or high-speed movement misrecognition is quite low. .

  Hereinafter, the response characteristic of the reception electric field strength detection of the present invention will be described with reference to FIG. In the detectors 2c and 2d provided with the low-pass filters 4c and 4d, the residual amount of the baseband modulation signal appearing in the received electric field strength is small, and the transient response time is long. The detectors 2a and 2b not provided with the low-pass filter 4a have a large baseband modulation signal appearing in the received electric field strength and a short transient response time. There is a trade-off between the residual amount of the baseband modulation signal appearing in the received electric field strength and the transient response time. The transient response time of the received electric field strength synthesized by the adder 3 becomes shorter than the conventional received electric field strength, and the antenna selection time can be increased.

  Basic operations other than the change in operation due to the provision of the low-pass filters 4c and 4d are the same as in the conventional example.

  According to the reception field strength detection method of the reception apparatus according to the present invention, while making the antenna selection time fast, in the weak signal field of the received signal that is below the threshold value of the reception field strength, malfunction of antenna selection, fading detection error, It is possible to prevent an increase in the number of channel switching due to erroneous recognition of movement.

  The reception antenna selection method of the present invention detects the reception field strength of each of the plurality of antennas using the antenna selection step of selecting any one of the reception signals of the plurality of antennas and the reception field strength detection method described above. The received electric field strength detection step, the comparison step for comparing the received electric field strength of each of the plurality of antennas detected by the received electric field strength detection step, and the antenna element having the maximum received electric field strength based on the comparison result of the comparison step Selecting a received signal.

  Further, the reception method of the present invention detects the received electric field strength of each of the plurality of antennas using the antenna selection step for selecting one of the received signals of the plurality of antennas and the received electric field strength detection method described above. A reception field strength detection step, a fading detection step for detecting a fading period from a change in the reception field strength detected by the reception field strength detection step, and a moving speed of the communication device is determined from the fading cycle detected by the fading detection step A determination step, a switching step for switching the base station when the moving speed determined in the moving speed determination step is greater than a predetermined value, and a base station selection step for selecting a received signal from the base station switched in the switching step. Including.

  Any of the above-described inventions have the same effects as the received electric field strength detection method.

  As described above, according to the received electric field strength detection circuit and the received electric field strength detection method according to the present invention, the received electric field strength is obtained by providing the low-pass filter only in the detector in which the received signal operates in the weak electric field. If the received signal is less than the set threshold, the baseband modulation signal does not remain when the received signal is weak, so the received field strength can be detected with high accuracy, erroneous antenna selection, fading misdetection, and high-speed movement misrecognition. The increase in the number of channel switching due to can be prevented. Moreover, since the transient response time of the received electric field strength is also shorter than the conventional received electric field strength, the antenna selection time can be increased. The present invention is useful for a diversity receiver or the like that requires high-precision and high-speed antenna selection means.

It is a block diagram which shows the structure of the received electric field strength detection circuit of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the received electric field strength detection circuit of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the received electric field strength detection circuit of the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the received electric field strength detection circuit of the 4th Embodiment of this invention. It is a block diagram which shows the structure of the conventional receiving electric field strength detection circuit. It is a circuit diagram which shows the structure of the received electric field strength detection circuit of the 1st Embodiment of this invention, especially the structure of the detector which detects a received signal level. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a figure which shows the operating characteristic of the detector 2a. It is a figure which shows the operating characteristic of the detector 2b. It is a figure which shows the operating characteristic of the detector 2c. It is a figure which shows the operating characteristic of the detector 2d. It is a block diagram which shows the structure of a diversity receiver. It is a figure which shows the operating characteristic of reception electric field strength detection. It is a figure which shows the operating characteristic of the reception electric field strength detection of this invention. It is a figure which shows the operating characteristic of the conventional reception electric field strength detection. (When the detection accuracy of the received electric field strength is low and the transient response time is short) It is a figure which shows the operating characteristic of the conventional reception electric field strength detection. (When the received field strength detection accuracy is high and the transient response time is long)

Explanation of symbols

1a, 1b, 1c, 1b Amplifier 2a, 2b, 2c, 2d Detector 3, 3a Adder 4, 4a, 4b, 4c, 4d Low pass filter 5 Band pass filter 6 Mixer 7 Band pass filter 8 Mixer 9 Low noise amplifier DESCRIPTION OF SYMBOLS 10 Reception electric field strength detection circuit 101,102 Antenna 103 Antenna switch 104 Reception radio | wireless part 105 Antenna selection means

Claims (9)

By detecting the output signals from multiple cascaded amplifiers that amplify the received signal, the lower limit level of the received signal that can be detected is gradually lowered from the received signal level in the strong electric field to the received signal level in the weak electric field. A plurality of detectors for detecting the level of the received signal in the state,
A first adder that adds and synthesizes detection signals output from the plurality of detectors and outputs a received electric field strength detection signal;
Among the plurality of detectors, a detector for sharing detection of a received signal level in a weak electric field such that the received electric field strength detection signal is not more than a preset threshold value, and the first adder, And a first low-pass filter for smoothing a detection signal provided between the two.   The filter which inputs only the desired received signal of the received signals output from the amplifier of the previous stage into the amplifier of the next stage is arranged between two consecutive amplifiers of the plurality of amplifiers. The receiving field strength detection circuit according to the description.   The received electric field strength detection circuit according to claim 1, further comprising a second low-pass filter for smoothing an output signal of the first adder. There are at least two detectors that share the detection of the level of the received signal in a weak electric field such that the received electric field strength detection signal is less than or equal to a set threshold value;
The first low-pass filter includes at least two detectors that share detection of a received signal level in a weak electric field such that the received electric field strength detection signal is less than or equal to a set threshold value. An attenuation amount of the first low-pass filter corresponding to a detector that is individually provided between the adder and the detector that shares the detection of the level of a received signal with a weaker electric field is further increased. 1. The reception field strength detection circuit according to 1. There are at least two detectors that share the detection of the level of the received signal in a weak electric field such that the received electric field strength detection signal is less than or equal to a set threshold value;
A second addition for adding the detection signals output from at least two detectors that share the detection of the level of the reception signal at the time of the weak electric field such that the reception electric field strength detection signal is equal to or less than a set threshold value. Equipped with
The received electric field strength detection circuit according to claim 1, wherein an output signal of the second adder is supplied to the first low-pass filter.   The first adder comprises: a plurality of antennas in front of the first-stage amplifier among the plurality of stages of amplifiers; and an antenna switching unit that switches received signals from the plurality of antennas and supplies the signals to the first-stage amplifier. The reception field strength detection circuit according to claim 1, wherein the antenna switch is switched according to the output of the received signal.   A reception signal is amplified in multiple stages, a detection signal is generated in each stage by detecting the amplified signal in each stage, and a reception electric field strength detection signal is generated by adding and combining the detection signals in each stage. Received electric field strength that is added after smoothing a detected signal corresponding to the level of the received signal in a weak electric field such that the received electric field strength detected signal is below a preset threshold value. Detection method. An antenna selection step for selecting one of the reception signals of a plurality of antennas;
A reception field strength detection step of detecting a reception field strength of each of the plurality of antennas using the reception field strength detection method according to claim 7;
A comparison step of comparing the reception field strength of each of the plurality of antennas detected by the reception field strength detection step;
A selection step of selecting a reception signal from an antenna element having the maximum reception electric field intensity based on a comparison result in the comparison step. An antenna selection step for selecting one of the reception signals of a plurality of antennas;
A reception field strength detection step of detecting a reception field strength of each of the plurality of antennas using the reception field strength detection method according to claim 7;
A fading detection step of detecting a fading period from a change in the reception field strength detected by the reception field strength detection step;
A determination step of determining a moving speed of the communication device from the fading period detected by the fading detection step;
A switching step of switching the base station when the moving speed determined by the moving speed determining step is greater than a predetermined value;
A base station selection step of selecting a received signal from the base station switched by the switching step.

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