JP4735472B2 - Mobile communication system, mobile phone terminal, and low-noise amplifier switching threshold control method used therefor - Google Patents

Description

  The present invention relates to a mobile communication system, a mobile phone terminal, a low noise amplifier switching threshold value control method used therefor, and a program therefor, and more particularly to an LNA (Low Noise Amplifier) having a mechanism capable of performing gain switching according to a reception level in a mobile phone terminal. .

  Conventionally, the LNA gain mode switching threshold is constant regardless of the communication rate, and therefore, a reception level at which reception sensitivity does not deteriorate even when the communication rate is high is set (for example, see Patent Document 1).

  A general configuration of this LNA is shown in FIG. In FIG. 8, the LNA circuit 30 includes an LNA 31, a bias (Bias) circuit 32, a switch 33, and a logic (Logic) circuit 34.

  The LNA circuit 30 has a high gain mode and a low gain mode. In the high gain mode, the LNA 31 is turned on to amplify the signal and increase the S / N (Signal / Noise) ratio (ratio of signal to noise). . On the contrary, in the low gain mode, the LNA 31 is turned off and a path for bypassing the LNA 31 (path via the switch 33) is provided to output the signal without amplifying it.

  Therefore, when the received signal level is sufficiently high, there is an advantage that the current consumption can be reduced by setting the low gain mode to the amount that the LNA 31 is turned off. For this reason, in general, in a mobile phone terminal, when the reception level is high, the LNA 31 is set to the low gain mode as much as possible, the current consumption is reduced, and the reception level is reduced, that is, the S / N ratio is deteriorated. When it is near, the mode is switched to the high gain mode, the S / N ratio is improved, and the reception sensitivity is improved.

  However, generally, as the communication rate increases, the required S / N ratio becomes severe, and the reception sensitivity level becomes worse as the communication rate increases. Therefore, this is a switching threshold value for switching the LNA 31 from the low gain mode to the high gain mode. If the reception level is set to a reception level that is several dB higher than the reception sensitivity level when the communication rate is low, the LNA 31 changes from the low gain mode to the high gain mode even when the communication rate is high, even if the required S / N ratio or less. Since it is not switched to, the reception sensitivity is greatly deteriorated.

  For example, in the case of WCDMA (Wideband Code Division Multiple Access), which is a communication method standardized by 3GPP (3rd Generation Partnership Project), the reception sensitivity (reference example) differs depending on the communication rate as shown in FIG. That is, in the low gain mode of the LNA 31 and the communication rate is 384 kbps, the reception level for switching from the low gain mode to the high gain mode of the LNA 31 is set to, for example, −90 dBm, which is lower than the reception sensitivity level of 384 kbps. If the level is -85 dBm, the data cannot be demodulated correctly.

  Conversely, if the reception level that is the threshold for switching from the low gain mode to the high gain mode of the LNA 31 is set to a reception level that is several dB higher than the reception sensitivity level when the communication rate is high, the communication rate is low and sufficient Even when there is an S / N ratio, since the LNA 31 is in the high gain mode, the current is wasted.

Japanese Patent Laid-Open No. 2005-223583

  In the conventional mobile phone terminal described above, even when the communication rate is low and the reception sensitivity is sufficient, there is a situation where the LNA is switched to the high gain mode, and the current is consumed wastefully by the LNA. There's a problem.

  Accordingly, an object of the present invention is to solve the above-described problems, use a low-noise amplifier in a low-gain mode as much as possible, and reduce a current consumption, a mobile communication system, a mobile phone terminal, and a low-noise amplifier switching used for them. A threshold control method and a program therefor are provided.

A mobile communication system according to the present invention includes a base station and a mobile communication device including a low noise amplifier having a mechanism capable of switching gains according to a reception level from the base station, and a mobile phone terminal corresponding to a communication rate from low speed to high speed. a system, the portable telephone terminal, possess means for measuring the communication rate, and a control means for performing control for changing the threshold value of the switching gain of the low noise amplifier in accordance with the measured transmission rate, Further, the mobile phone terminal includes a counting unit that counts the number of gain switching of the low noise amplifier, and the control unit is configured to perform the predetermined period when the count value of the counting unit reaches a switching number limit value within a predetermined time. It is characterized by prohibiting the gain switching of the low noise amplifier.

A mobile phone terminal according to the present invention includes a low noise amplifier having a mechanism capable of switching gains according to a reception level from a base station, and corresponds to a communication rate from low speed to high speed, and measures the communication rate. includes a means, the counting means that depending on the measured communication rate have a control means for performing control for changing the threshold value of the switching gain of said low noise amplifier, further counts the gain switching frequency of the low-noise amplifier, the The control means prohibits the gain switching of the low noise amplifier for a predetermined period when the count value of the counting means reaches a switching frequency limit value within a predetermined time.

The low-noise amplifier switching threshold control method according to the present invention includes a low-noise amplifier having a mechanism capable of performing gain switching according to the reception level from the base station, and switches the low-noise amplifier used in a mobile phone terminal corresponding to a communication rate from low speed to high speed In the threshold control method, the mobile phone terminal performs a process of measuring the communication rate and a control process of performing a control of changing a gain switching threshold of the low noise amplifier according to the measured communication rate Further, the mobile phone terminal executes a counting process for counting the number of gain switching times of the low noise amplifier, and in the control process, when the count value of the counting means reaches a switching number limit value within a predetermined time, The low-noise amplifier gain switching is prohibited for a predetermined period.

A program according to the present invention includes a low noise amplifier having a mechanism capable of switching gain according to a reception level from a base station, and is a program executed by a mobile phone terminal corresponding to a communication rate from low speed to high speed. The control device executes a process for measuring the communication rate and a control process for performing a control for changing a gain switching threshold of the low noise amplifier according to the measured communication rate, and further, a gain of the low noise amplifier A counting process for counting the number of times of switching is executed, and in the control process, when the count value of the counting means reaches a switching number limit value within a predetermined time, the gain switching of the low noise amplifier is prohibited for a predetermined period. It is characterized by being.

  That is, the low-noise amplifier switching threshold control method of the present invention has an LNA (Low Noise Amplifier) having a mechanism in which a mobile phone terminal corresponding to a communication rate from low speed to high speed can perform gain switching according to the reception level. The control is performed to change the gain switching threshold of the LNA according to the communication rate.

  That is, in the low noise amplifier LNA switching threshold value control method of the present invention, in order to solve the above-described problem, the reception level serving as a threshold value when the LNA is switched from the low gain mode to the high gain mode is dynamically switched according to the communication rate. Since a mechanism is provided, it is possible to reduce power consumption as much as possible while maintaining reception characteristics.

  As described above, in the low noise amplifier switching threshold value control method of the present invention, the threshold value when the LNA is switched from the low gain mode to the high gain mode is changed corresponding to the communication rate, so the LNA is used in the low gain mode as much as possible. Thus, current consumption can be reduced.

  Further, in the low noise amplifier switching threshold value control method of the present invention, the threshold value when the LNA switches from the low gain mode to the high gain mode is changed corresponding to the communication rate, so that the LNA can be used in the low gain mode as much as possible. In addition, reception sensitivity does not deteriorate even when the communication rate is high.

  Furthermore, in the low noise amplifier switching threshold control method of the present invention, when reception level fluctuation is large due to fading environment or the like, the reception sensitivity deterioration is suppressed by limiting the number of LNA gain mode switching within a certain time. Is possible.

  Furthermore, in the low noise amplifier switching threshold control method of the present invention, even when the reception level varies greatly due to fading environment or the like, if the reception environment is better than the SIR (Signal to Interference power Ratio) value, the LNA gain mode switching is frequently performed. Allowing it to happen.

  By adopting the configuration and operation as described above, the present invention can use the low-noise amplifier in the low-gain mode as much as possible, and the effect that the current consumption can be reduced is obtained.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration example of a mobile phone terminal according to a first embodiment of the present invention. In FIG. 1, a mobile phone terminal according to a first embodiment of the present invention includes a CPU (central processing unit) device 11, a digital signal processing device 12 under the basic control, an analog signal processing device 13, and an RF signal. (Radio Frequency) device 14, memory device 15, power supply device 16, battery 17, and antennas 18 and 19.

  The CPU device 11 controls the digital signal processing device 12, the analog signal processing device 13, the RF device 14, the memory device 15, the power supply device 16, and exchanges data with the digital signal processing device 12.

  The RF device 14 performs modulation / demodulation of a radio signal, the analog signal processing device 13 performs AD (analog / digital) conversion of the signal from the RF device 14, sends the AD converted signal to the digital signal processing device 12, and performs digital signal processing. The signal from the device 12 is DA (digital / analog) converted, and the DA converted signal is sent to the RF device 14.

  The digital signal processing device 12 performs digital signal processing on the signal from the analog signal processing device 13 to decode the signal, and sends the decoded signal to the CPU device 11.

  Further, the digital signal processing device 12 measures the RSSI (Received Signal Strength Indicator) level, and depending on the measured value, the RF device 14 receives the received gain control signal or LNA (Low Noise Amplifier). Send the mode switching signal.

  Further, the digital signal processing device 12 performs power control of the transmission signal and performs SIR (Signal to Interference power Ratio) measurement.

  Control information and the like are written in the memory device 15, and the CPU device 11 reads and writes according to the control, and stores LNA mode switching threshold data. The memory device 15 also stores a program for the CPU device 11 to control and a program executed by the digital signal processing device 12.

  The power supply device 16 supplies power to the CPU device 11, the digital signal processing device 12, the analog signal processing device 13, the RF device 14, and the memory device 15 in accordance with control from the CPU device 11. The battery 17 supplies a voltage to the entire device via the power supply device 16. The antennas 18 and 19 receive a signal from a base station (not shown) and transmit a signal from the mobile phone terminal to the base station.

  FIG. 2 is a block diagram showing the configuration of the RF device 14 of FIG. In FIG. 2, an RF device 14 normally includes an antenna switch (ANTSW) 141 that switches between antennas 18 and 19 to be used, a duplexer 142 that is a filter that separates a transmission signal and a reception signal, and signal amplification while suppressing noise as much as possible. LNA 143 that can be switched between high gain mode and low gain mode, BPF (Band Path Filter) 144 that attenuates signals other than the received signal, signal modulation / demodulation circuit, transmission, variable gain amplifier for transmission, baseband filter, RFIC (Radio Frequency Integrated Circuit) 145 consisting of an amplifier, PLL (Phase Locked Loop) synthesizer, BPF 146 for attenuating signals other than transmission signals, and an amplifier capable of amplifying to high power That the PA147, and a isolator 148. which does not flow back signal high power.

  The LNA switching threshold value control method according to the first embodiment of the present invention will be described with reference to FIGS. Hereinafter, how to obtain RSSI and LNA gain will be shown as an example. In this example, a case of WCDMA (Wideband Code Division Multiple Access) will be described.

In the case of WCDMA, the received signal is demodulated and then divided into an I signal and a Q signal. First, instantaneous power is obtained (RSSI calculation # 1). This instantaneous power is
RX_Level (n) = I (n) ² + Q (n) ²
(N = 0 to N)
It is calculated by the formula. N is an arbitrary number of samples.

Next, the average instantaneous power is obtained (RSSI calculation-2). This average instantaneous power is
RX_Level2 = 1 / N · ΣRX_Level (n)
It is calculated by the formula. Note that Σ is the sum of n = 0 to N.

Subsequently, the average instantaneous power value is converted by dB (RSSI calculation # 3). The dB conversion is
RX_Level_dB = 10 Log (RX_Level2)
It is done with the formula.

  Further, a known level (for example, a signal of −60 dBm) is input from the antenna 18, and the digital signal processing device 12 calculates RSSI calculation # 1 to RSSI calculation # 3 (RSSI calculation # 4).

In the digital signal processing device 12, when the LNA 143 is in the high gain mode,
RX_Level correction value = −60 dBm−RX_Level_dB
-LNA_GAIN-RFIC_GAIN
When the LNA 143 is in the low gain mode,
RX_Level correction value = −60 dBm−RX_Level_dB
-RFIC_GAIN
(RSSI calculation # 5).

LNA_GAIN, which is the gain of LNA 143, is the difference between the RSSI in the low gain mode and the RSSI in the high gain mode in RSSI calculation # 5, and RFIC_GAIN is the gain of the receiving variable amplifier of RFIC 145, which is set by digital signal processing device 12 Therefore, it is a known value. For example, if the value of RX_Level_dB is 10 dBm, LNA_GAIN = 20 dB, and RFIC_GAIN = 30 dB, the RX_Level correction value is −10 dB. With the above,
RSSI = RX_Level_dB + RX_Level_Comp
It becomes. In this embodiment, RSSI = −10 dB (RSSI calculation # 6).

  Next, a method for switching the LNA 143 from the low gain mode to the high gain mode will be described. Initially, when the LNA 143 is in the low gain mode, RSSI measurement (RSSI calculation # 7) is performed. At that time, for example, when the high gain threshold (HIGHGAIN_TH) = − 90 dBm, which is the high gain mode switching threshold, is set to RSSI = −90 dBm, the digital signal processing device 12 detects that the high gain threshold ≧ RSSI. Thereafter, a signal for switching the LNA 143 from the low gain mode to the high gain mode is sent, and the LNA 143 switches from the low gain mode to the high gain mode. The subsequent RSSI measurement method is performed by RSSI calculation # 6.

  Similarly, the switching method of the LNA 143 from the high gain mode to the low gain mode is, for example, when the low gain threshold (LOWGAIN_TH), which is the threshold for low gain mode switching, is set to −50 dBm and the RSSI = −50 dBm. 12 detects a low gain threshold ≦ RSSI, and then sends a signal for switching the LNA 143 from the high gain mode to the low gain mode, and the LNA 143 switches from the high gain mode to the low gain mode. The subsequent RSSI measurement method is performed by RSSI calculation # 7.

  An LNA switching threshold control method according to an embodiment of the present invention will be described with reference to the control procedure of FIGS. 3 and 4 based on the above RSSI calculation method and the relationship of switching from low gain mode to high gain mode of LNA. To do. In this embodiment, the case of WCDMA, which is a communication method standardized by 3GPP (3rd Generation Partnership Project), will be described, but only the control procedure related to the present invention will be described below. 3 and 4, the processing of the digital signal processing device 12 can also be realized by the digital signal processing device 12 executing the program of the memory device 15.

  First, in order to perform voice and data communication, the CPU 11 opens a data channel (CH) [DPDCH (Dedicated Physical Data Channel), DPCCH (Dedicated Physical Control Channel)] at a certain communication rate, for example, “384 kbps”. The digital signal processing device 12 is commanded, and at that time, the communication rate (“384 kbps”), the high gain threshold value, and the low gain threshold value read from the memory device 15 are set (a1 in FIG. 3). In this example, high gain threshold = −60 dBm and low gain threshold = −40 dBm.

  Next, as an initial setting, the digital signal processing device 12 sets a low gain mode in the LNA 143 of the RF device 14 (a2 in FIG. 3), starts communication using a data channel, and 1 slot ( 667 μs) starts gain control on the received signal and power control on the transmitted signal (a3 in FIG. 3), and simultaneously performs RSSI measurement for one slot. At this time, the measured RSSI is -65 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold and detects that the high gain threshold ≧ RSSI (a4 in FIG. 3), so that the LNA 143 is switched from the low gain mode to the high gain mode at the next slot boundary ( A5 in FIG. 3) RSSI measurement is performed between 1 slot. At this time, the measured RSSI is -35 dBm.

  The digital signal processor 12 compares the RSSI and the value of the low gain threshold value and detects that the low gain threshold value ≦ RSSI (a6 in FIG. 3), and switches the LNA 143 from the high gain mode to the low gain mode at the next slot boundary ( A7) in FIG. Thereafter, the digital signal processing device 12 performs the same control as described above.

  Next, the CPU device 11 instructs the digital signal processing device 12 to close the data channel in order to stop the voice and data communication (a8 in FIG. 3). The digital signal processing device 12 stops the gain control for the reception signal, the power control for the transmission signal, and the RSSI measurement for one slot in a slot (667 μs) unit with respect to the RF device 14 (a9 in FIG. 3). The LNA 143 of the device 14 is set to the low gain mode (a10 in FIG. 3).

  Thereafter, the CPU device 11 instructs the digital signal processing device 12 to open the data channel at a certain communication rate, for example, “12.2 kbps” for voice and data communication, and at that time, reads from the memory device 15. The communication rate (“12.2 kbps”), high gain threshold, and low gain threshold are set (a11 in FIG. 3). In this example, high gain threshold = −90 dBm and low gain threshold = −40 dBm.

  The digital signal processing device 12 starts communication using the data channel, and starts gain control on the reception signal and power control on the transmission signal in units of one slot (667 μs) with respect to the RF device 14 (a13 in FIG. 4). ) Simultaneously, RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -65 dBm.

  Since the digital signal processing device 12 compares the RSSI with the value of the high gain threshold value and detects that the high gain threshold value <RSSI (a14 in FIG. 4), it is not necessary to change the mode of the LNA 143 at the next slot boundary. When RSSI measurement is performed for one slot and the measurement result is −95 dBm, the LNA 143 is in the low gain mode, so RSSI = −95 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold value and detects that the high gain threshold value ≧ RSSI (a15 in FIG. 4), so that the LNA 143 is switched from the low gain mode to the high gain mode at the next slot boundary ( (A16 in FIG. 4) The RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -35 dBm.

  The digital signal processing device 12 compares the RSSI and the low gain threshold value, and detects that the low gain threshold value ≧ RSSI (a17 in FIG. 4), and switches the LNA 143 from the high gain mode to the low gain mode at the next slot boundary (FIG. 4). 4 a18). Thereafter, the digital signal processing device 12 performs the same control as described above.

  Thereafter, the CPU device 11 instructs the digital signal processing device 12 to close the data channel in order to stop the voice and data communication (a19 in FIG. 4). The digital signal processing device 12 stops the gain control for the reception signal, the power control for the transmission signal, and the RSSI measurement between the slots in units of one slot (667 μs) with respect to the RF device 14 (a20 in FIG. 4). The LNA 143 of the device 14 is set to the low gain mode (a21 in FIG. 4).

  As described above, in this embodiment, since the LNA 143 has a mechanism for dynamically switching the reception level as a threshold when the LNA 143 switches from the low gain mode to the high gain mode according to the communication rate, while maintaining the reception characteristics, Power consumption can be reduced as much as possible. In this embodiment, the LNA 143 can be used in the low gain mode as much as possible, and the current consumption can be reduced.

  FIG. 5 is a sequence chart showing a control procedure of the LNA switching threshold value control method according to the second embodiment of the present invention. The configuration of the mobile phone terminal and the RF device of the mobile phone terminal according to the second embodiment of the present invention is the same as that of the first embodiment of the present invention shown in FIGS. . The control procedure of the LNA switching threshold control method according to the second embodiment of the present invention will be described with reference to FIGS. In the control procedure of FIG. 5, the processing of the digital signal processing device 12 can also be realized by the digital signal processing device 12 executing a program of the memory device 15.

  The second embodiment of the present invention limits the number of times of mode switching of the LNA 143 within a certain time, has a large reception level fluctuation due to fading, etc., frequently crosses the mode switching threshold (low gain threshold, high gain threshold), and frequently It differs from the other embodiments in that the reception sensitivity deterioration due to the mode switching of the LNA 143 is suppressed.

  This is because when the communication rate is high, the value of the high gain threshold is higher than when the communication rate is low, but even when a high level signal is received, the signal does not saturate. This is because the threshold value cannot be increased, and as a result, the mode switching threshold interval becomes narrower than when the communication rate is low. As a result, mode switching of the LNA 143 is likely to occur frequently, and in particular, a data error near the slot boundary where the mode switching of the LNA 143 is performed may occur. However, the LNA 143 is not switched as much as possible.

  First, the CPU device 11 instructs the digital signal processing device 12 to open a data channel at a certain communication rate (for example, “384 kbps”) for voice and data communication. A communication rate “384 kbps”, a high gain threshold (HIGHGAIN_TH), a low gain threshold (LOWGAIN_TH), a mode switching frequency limit value (SW_LIMIT), a mode switching count time (SW_COUNT_TIME), and a mode switching prohibition time (SW_PROHIBIT_TIME) are set (b1 in FIG. 5). ). In this example, a high gain threshold = −60 dBm, a low gain threshold = −40 dBm, a mode switching frequency limit value = 4 times, a mode switching count time = 6 slots, and a mode switching prohibition time = 2 slots.

  As an initial setting, the digital signal processing device 12 sets a low gain mode in the LNA 143 of the RF device 14 (b2 in FIG. 5), starts communication using the data channel, and makes a unit of 1 slot (667 μs) to the RF device 14. Starting with gain control on the received signal and power control on the transmitted signal, RSSI measurement is performed for one slot at the same time (b3 in FIG. 5). At this time, the measured RSSI is -65 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold value, and in order to detect that the high gain threshold value ≧ RSSI, the mode switching frequency is counted as “1” (b4 in FIG. 5), and the next slot boundary Then, the LNA 143 is switched from the low gain mode to the high gain mode (b5 in FIG. 5), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -35 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the low gain threshold value, and in order to detect that the low gain threshold value ≦ RSSI, counts the number of mode switching as “2” (b6 in FIG. 5), and the next slot boundary Then, the LNA 143 is switched from the high gain mode to the low gain mode (b7 in FIG. 5), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -65 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold value, and in order to detect that the high gain threshold value ≧ RSSI, the mode switching frequency is counted as “3” (b8 in FIG. 5), and the next slot boundary Then, the LNA 143 is switched from the low gain mode to the high gain mode (b9 in FIG. 6), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -35 dBm.

The digital signal processing device 12 compares the RSSI and the value of the low gain threshold, detects the low gain threshold ≦ RSSI, and counts the number of mode switching as “4” (b10 in FIG. 5), and the next slot boundary. Thus, the LNA 143 is switched from the high gain mode to the low gain mode (b11 in FIG. 5). At this point, since the number of mode switching frequency limit values has been exceeded within 6 slots, mode switching is prohibited for 2 slots thereafter (b12 in FIG. 5) . Thereafter, the digital signal processing device 12 performs the same control as described above.

  As described above, in this embodiment, by limiting the number of times of mode switching of the LNA 143 within a certain period of time, the reception level fluctuates greatly due to fading, etc., frequently crosses the mode switching threshold, and mode switching of the LNA 143 occurs frequently. It is possible to suppress deterioration in reception sensitivity due to the operation.

  FIG. 6 is a diagram showing how to obtain the SIR in the third embodiment of the present invention, and FIG. 7 is a sequence chart showing the control procedure of the LNA switching threshold control method according to the third embodiment of the present invention. The configuration of the mobile phone terminal and the RF device of the mobile phone terminal according to the third embodiment of the present invention is the same as that of the first embodiment of the present invention shown in FIGS. . A control procedure of the LNA switching threshold control method according to the third embodiment of the present invention will be described with reference to FIGS. 1, 2, 6, and 7. FIG. In the control procedure of FIG. 7, the processing of the digital signal processing device 12 can also be realized by the digital signal processing device 12 executing the program of the memory device 15.

  In the third embodiment of the present invention, when the SIR is good, reception level fluctuation is large due to fading, etc., frequently straddling the mode switching threshold (low gain threshold, high gain threshold), and mode switching of the LNA 143 frequently occurs. Even in the case where the LNA 143 is present, the mode switching restriction of the LNA 143 is not performed.

  First, how to obtain SIR is shown. In the case of WCDMA, after demodulating the received signal, it is divided into an I signal and a Q signal, and the I signal and the Q signal are orthogonal to each other, so that symbol points can be formed on the complex plane. Symbol points are gathered at points, but in reality, the points are spread due to the influence of interference waves. This is shown in FIG.

  The strength up to the ideal symbol point is called RSCP (Received Signal Code Power), which is the power of the signal after despreading. The intensity of spread (dispersion of symbol points) is referred to as ISCP [Interference Signal Code Power: Interference wave (also referred to as interference wave) signal average power], and it can also be said to be the difference between symbol points before and after despreading. And SIR is derived | led-out by ratio of RSCP and ISCP.

  That is, SIR = RSCP ÷ ISCP, and the larger the interference wave, the smaller the value. Further, Ec / No (= RSCP / RSSI), which is a ratio of desired signal energy per bit and noise, may be used instead of SIR from RSSI and RSCP. All of this processing is performed by the digital signal processing device 12.

  First, the CPU device 11 instructs the digital signal processing device 12 to open a data channel at a certain communication rate (for example, “384 kbps”) for voice and data communication. Communication rate “384 kbps”, high gain threshold (HIGHGAIN_TH), low gain threshold (LOWGAIN_TH), mode switching count limit value (SW_LIMIT), mode switching count time (SW_COUNT_TIME), mode switching prohibition time (SW_PROHIBIT_TIME), mode switching allowable SIR threshold (SW_SIR_TH) ) Is set (c1 in FIG. 7). In this example, high gain threshold = −60 dBm, low gain threshold = −40 dBm, mode switching frequency limit value = 3, mode switching count time = 6 slots, mode switching prohibition time = 2 slots, and mode switching allowable SIR threshold = −16 dB. To do.

  As an initial setting, the digital signal processing device 12 sets a low gain mode in the LNA 143 of the RF device 14 (c2 in FIG. 7), starts communication using a data channel, and makes a unit of 1 slot (667 μs) to the RF device 14. Starting with gain control on the received signal and power control on the transmitted signal, RSSI measurement and SIR measurement are performed for one slot (c3 in FIG. 7). At this time, the measured RSSI is -65 dBm.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold value, and in order to detect that the high gain threshold value ≧ RSSI, counts the number of mode switching as “1” (c4 in FIG. 7), and the next slot boundary Then, the LNA 143 is switched from the low gain mode to the high gain mode (c5 in FIG. 7), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -35 dBm. Further, since the mode switching of the LNA 143 occurs in this slot, the digital signal processing device 12 stores the SIR value of this slot.

  The digital signal processing device 12 compares the RSSI and the value of the low gain threshold value, and in order to detect that the low gain threshold value ≦ RSSI, counts the number of mode switching as “2” (c6 in FIG. 7), and the next slot boundary Then, the LNA 143 is switched from the high gain mode to the low gain mode (c7 in FIG. 7), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -65 dBm. Further, since the mode switching of the LNA 143 occurs in this slot, the digital signal processing device 12 stores the SIR value of this slot.

  The digital signal processing device 12 compares the RSSI and the value of the high gain threshold value, and in order to detect that the high gain threshold value ≧ RSSI, the mode switching frequency is counted as “3” (c8 in FIG. 7), and the next slot boundary Then, the LNA 143 is switched from the low gain mode to the high gain mode (c9 in FIG. 7), and RSSI measurement between 1 slot is performed. At this time, the measured RSSI is -35 dBm. Further, since the mode switching of the LNA 143 occurs in this slot, the digital signal processing device 12 stores the SIR value of this slot.

  The digital signal processing device 12 compares the RSSI and the value of the low gain threshold, detects the low gain threshold ≦ RSSI, and counts the number of mode switching as “4” (c10 in FIG. 7), and next slot boundary. Then, the LNA 143 is switched from the high gain mode to the low gain mode (c11 in FIG. 7).

  Subsequently, the digital signal processing device 12 performs SIR measurement of the next slot, obtains an average value (SW_SIR_AVE) of SIR values of the slot in which mode switching has occurred, and calculates the value (SW_SIR_AVE) as a mode switching allowable SIR threshold (SW_SIR_TH). Compare with If SW_SIR_AVE> SW_SIR_TH, the digital signal processing device 12 clears the number of mode switching times. If SW_SIR_AVE ≦ SW_SIR_TH, the number of mode switching number limit values has been exceeded within 6 slots at this time, so the following two slots Mode switching is prohibited (c12 in FIG. 7). Thereafter, the digital signal processing device 12 performs the same control as described above.

  Thus, in this embodiment, when the SIR is good, the reception level fluctuation is large due to fading, etc., the mode switching threshold is frequently straddled, and the mode switching of the LNA 143 occurs frequently. It is possible to prevent the restriction.

It is a block diagram which shows the structural example of the mobile telephone terminal by 1st Example of this invention. It is a block diagram which shows the structure of RF apparatus of FIG. It is a sequence chart which shows the control procedure of the LNA switching threshold value control method by 1st Example of this invention. It is a sequence chart which shows the control procedure of the LNA switching threshold value control method by 1st Example of this invention. It is a sequence chart which shows the control procedure of the LNA switching threshold value control method by 2nd Example of this invention. It is a figure which shows how to obtain | require SIR in the 3rd Example of this invention. It is a sequence chart which shows the control procedure of the LNA switching threshold value control method by 3rd Example of this invention. It is a figure which shows the general structure of the conventional LNA. It is a figure which shows the example from which receiving sensitivity changes with communication rates.

Explanation of symbols

11 CPU device
12 Digital signal processor
13 Analog signal processor
14 RF equipment
15 Memory device
16 Power supply
17 Battery 18, 19 Antenna
141 Antenna switch
142 Duplexer
143 LNA
144,146 BPF
145 RFIC
147 PA
148 Isolator

Claims (7)

A mobile communication system including a base station and a mobile phone terminal that supports a communication rate from low speed to high speed, including a low noise amplifier having a mechanism capable of switching gain according to a reception level from the base station,
The mobile telephone terminal, possess means for measuring the communication rate, and a control means for performing control for changing the threshold value of the switching gain of the low noise amplifier in accordance with the measured transmission rate,
Furthermore, the mobile phone terminal includes a counting means for counting the number of gain switching of the low noise amplifier,
The mobile communication system , wherein the control means prohibits the gain switching of the low noise amplifier for a predetermined period when the count value of the counting means reaches a switching frequency limit value within a predetermined time .   The mobile phone terminal includes means for measuring a SIR (Signal to Interference Power Ratio) value,
  The mobile communication system according to claim 1, wherein the control unit does not limit the number of gain switching of the low noise amplifier when detecting that the reception environment is good based on the measured SIR value.   A mobile phone terminal that includes a low-noise amplifier with a mechanism that allows gain switching according to the reception level from the base station, and that supports communication rates from low speed to high speed,
  Means for measuring the communication rate, and control means for performing control to change a gain switching threshold of the low noise amplifier according to the measured communication rate,
  Furthermore, it includes a counting means for counting the number of gain switching of the low noise amplifier,
  The mobile phone terminal characterized in that the control means prohibits gain switching of the low-noise amplifier for a predetermined period when the count value of the counting means reaches a switching frequency limit value within a predetermined time.   Means for measuring SIR (Signal to Interference Power Ratio) values;
  4. The mobile phone terminal according to claim 3, wherein when the control unit detects that the reception environment is good based on the measured SIR value, the control unit does not limit the number of gain switching of the low noise amplifier.   A low noise amplifier switching threshold control method used for a mobile phone terminal that supports a communication rate from low speed to high speed, including a low noise amplifier having a mechanism that can perform gain switching according to a reception level from a base station,
  The mobile phone terminal performs a process of measuring the communication rate, and a control process of performing control to change a gain switching threshold of the low noise amplifier according to the measured communication rate,
  Further, the mobile phone terminal executes a counting process for counting the number of gain switching of the low noise amplifier,
  In the control process, when the count value of the counting means reaches a switching frequency limit value within a predetermined time, gain switching of the low noise amplifier is prohibited for a predetermined period.   The mobile phone terminal performs a process of measuring an SIR (Signal to Interference Power Ratio) value,
  6. The low noise amplifier switching threshold control method according to claim 5, wherein, in the control processing, when it is detected that the reception environment is good based on the measured SIR value, the number of gain switching of the low noise amplifier is not limited. .   A program executed by a mobile phone terminal that supports a communication rate from low speed to high speed, including a low-noise amplifier that has a mechanism that allows gain switching according to the reception level from the base station,
  Causing the control device of the mobile phone terminal to execute a process of measuring the communication rate and a control process of performing a control to change a gain switching threshold of the low noise amplifier according to the measured communication rate;
  Further, a counting process for counting the number of gain switching of the low noise amplifier is executed,
  In the control process, a program for prohibiting gain switching of the low-noise amplifier for a predetermined period when the count value of the counting means reaches a switching number limit value within a predetermined time.

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