JP2010177824A - Radio communication terminal, transmission circuit, and transmission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption of a transmission circuit and suppress the degradation of reception characteristic of a reception circuit in an FDD system. <P>SOLUTION: The radio communication terminal 100 includes a transmission circuit 120 to transmit a transmission signal through duplexer 110, a reception circuit 170 to receive a reception signal through the duplexer 110, and a controller 180 to control the transmission circuit 120 on the basis of the received SNR. The transmission circuit 120 includes an IF band circuit 140 that processes transmission signals in an intermediate frequency band in either of the normal mode or low power-consumption mode that is smaller in power consumption and out-band attenuation than the normal mode. The controller 180 operates the IF band circuit 140 in the low power-consumption mode when the received SNR exceeds a necessary SNR, and it operates the IF band circuit 140 in the normal mode when the received SNR is below the necessary SNR. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication terminal, a transmission circuit, and a transmission control method used in a wireless communication system employing a frequency division duplex method.

  In a wireless communication system employing a frequency division duplex (FDD) scheme, a wireless communication terminal that performs wireless communication with a wireless base station includes an antenna, a transmission circuit that transmits a transmission signal via the antenna, and an antenna. A receiving circuit for receiving the received signal, and a duplexer connected to each of the antenna, the transmitting circuit, and the receiving circuit. The duplexer attenuates transmission signals outside the transmission band and attenuates reception signal components outside the reception band.

  In recent years, wideband wireless communication schemes such as an orthogonal frequency division multiple access (OFDMA) scheme or a single carrier frequency division multiple access (SC-FDMA) scheme have attracted attention. The intermediate frequency (IF) band circuit of the transmission circuit corresponding to the broadband wireless communication system and conforming to the superheterodyne system or the double superheterodyne system has a wide passband and attenuates the transmission signal outside the passband. A band-pass filter having a large (hereinafter referred to as out-of-band attenuation) is provided.

  Since such a band pass filter has a large loss in the pass band, that is, a pass loss, NF (noise figure) in the IF band circuit deteriorates. Therefore, it is necessary to improve the NF by providing an amplifier in the IF band circuit. On the other hand, providing the amplifier increases the power consumption of the IF band circuit.

  Therefore, a technique has been proposed in which a band-pass filter having a large out-of-band attenuation and a band-pass filter having a small out-of-band attenuation are selectively used according to the transmission power of the transmission circuit (see Patent Document 1). The transmission circuit described in Patent Document 1 uses a band-pass filter with a small out-of-band attenuation when the transmission power is small and the interference power to other wireless communication devices (for example, peripheral wireless communication terminals) can be reduced. . When a band-pass filter with a small out-of-band attenuation is used, the amplifier can be turned off and an increase in power consumption can be avoided.

JP 2006-33731 A

  By the way, the reception circuit receives a transmission signal leaking from the transmission circuit into the reception band via the duplexer. A transmission signal within the reception band that leaks into the reception circuit becomes a factor that degrades the reception characteristics of the reception circuit. In particular, when the power of the reception signal received by the reception circuit from the radio base station is small, the influence of the transmission signal leaking into the reception circuit becomes relatively large, and it is difficult for the reception circuit to normally demodulate the reception signal. .

  However, since the transmission circuit described in Patent Document 1 transmits a transmission signal using a band-pass filter with a small out-of-band attenuation when the transmission power is small, the transmission signal in the reception band leaking into the reception circuit is transmitted. Increases power. That is, the technique described in Patent Document 1 has a problem that although the power consumption of the transmission circuit can be reduced, the reception characteristic of the reception circuit is deteriorated.

  Accordingly, the present invention provides a wireless communication terminal, a transmission circuit, and a transmission control method capable of suppressing deterioration of reception characteristics of a reception circuit while reducing power consumption of the transmission circuit in a wireless communication system employing an FDD scheme. The purpose is to do.

  In order to solve the above-described problems, the present invention has the following features. A first feature of the wireless communication terminal according to the present invention is a duplexer connected to an antenna (antenna 101) for attenuating a transmission signal outside the transmission band and attenuating a reception signal outside the reception band having a frequency band different from the transmission band. (Duplexer 110), a radio communication terminal having a transmission circuit (transmission circuit 120) that transmits the transmission signal via the duplexer, and a reception circuit (reception circuit 170) that receives the reception signal via the duplexer (Radio communication terminal 100), which leaks into the reception band from the transmission circuit via the duplexer, and receives a reception quality level (for example, reception SNR) reflecting the power of the transmission signal received by the reception circuit And a control unit (control unit 180) for controlling the transmission circuit based on the reception quality level, An intermediate frequency band circuit (IF band circuit 140) that processes the transmission signal in the intermediate frequency band in either one mode or a second mode in which power consumption and out-of-band attenuation are smaller than in the first mode. And the control unit operates the intermediate frequency band circuit in the second mode when the reception quality level satisfies a predetermined condition capable of maintaining the reception characteristics of the reception circuit, and the reception quality level is set to the predetermined level. The gist is to operate the intermediate frequency band circuit in the first mode when the condition is not satisfied.

  According to such a wireless communication terminal, the control unit operates the intermediate frequency band circuit in the second mode when the reception quality level satisfies a predetermined condition capable of maintaining the reception characteristics of the reception circuit. Since the second mode consumes less power than the first mode, the power consumption of the transmission circuit can be reduced. Further, the control unit causes the intermediate frequency band circuit to operate in the first mode when the reception quality level does not satisfy a predetermined condition for maintaining the reception characteristics of the reception circuit. Since the first mode has a larger out-of-band attenuation than the second mode, it is possible to reduce the power of the transmission signal in the reception band that leaks into the reception circuit, and to suppress the deterioration of the reception characteristics of the reception circuit.

  Therefore, according to the wireless communication terminal of the present invention, in the wireless communication system adopting the FDD scheme, it is possible to suppress the degradation of the reception characteristics of the reception circuit while reducing the power consumption of the transmission circuit.

  A second feature of the wireless communication terminal according to the present invention relates to the first feature, wherein the control unit further detects a transmission power level indicating the power of the transmission signal, and the transmission power level is predetermined. The transmission power level is below the transmission power level threshold and the reception quality level satisfies the predetermined condition, the intermediate frequency band circuit is operated in the second mode, and the transmission power level is below the transmission power level threshold, In addition, the gist is to operate the intermediate frequency band circuit in the first mode when the reception quality level does not satisfy the predetermined condition.

  A third feature of the wireless communication terminal according to the present invention relates to the first feature, wherein the control unit further detects a received power level (for example, RSSI) indicating the power of the received signal received by the receiving circuit. When the received power level exceeds a predetermined received power level threshold, the intermediate frequency band circuit is operated in the second mode.

  A fourth feature of the wireless communication terminal according to the present invention relates to the third feature, wherein the control unit is configured such that the received power level is lower than the received power level threshold, and the received quality level satisfies the predetermined condition. When the intermediate frequency band circuit is operated in the second mode, the transmission power level is lower than the reception power level threshold, and the reception quality level does not satisfy the predetermined condition, The gist is to operate the band circuit in the first mode.

  A fifth feature of the wireless communication terminal according to the present invention relates to the first feature, wherein the reception circuit receives the reception signal modulated by a modulation scheme according to adaptive modulation, and the control unit When the required reception quality level required for the modulation scheme is further detected, and the reception quality level satisfies the required reception quality level, the intermediate frequency band circuit is operated in the second mode, and the reception quality level is The gist is to operate the intermediate frequency band circuit in the first mode when the required reception quality level is not satisfied.

  A sixth feature of the wireless communication terminal according to the present invention relates to any one of the first to fifth features, wherein the transmission circuit is a mixer (mixer for performing conversion from the intermediate frequency band to the radio frequency band). 151), and the intermediate frequency band circuit includes an amplifier (amplifier 141) to which a power supply switch (switch SW3) for switching power supply is connected and a first bandpass filter (amplifier 141) connected to the output of the amplifier. A first mode intermediate frequency band circuit (switch SW3, band pass filter 142) having a band pass filter 142) and a second band pass filter (band pass filter) having a smaller out-of-band attenuation than the first band pass filter. 143) and a second mode intermediate frequency band circuit (bandpass filter 143), and the transmission signal in the intermediate frequency band is transmitted to the first mode. A first switch (switch SW1) that is input to either the intermediate frequency band circuit or the second mode intermediate frequency band circuit, and either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit A second switch (switch SW2) for inputting the output signal to the mixer, and the control unit sets the first switch and the second switch to the intermediate frequency for the first mode in the first mode. Switching to the band circuit side, supplying power to the amplifier using the power supply switch, and in the second mode, moving the first switch and the second switch to the second mode intermediate frequency band circuit side. The gist is to stop the supply of power to the amplifier using the power supply switch.

  A seventh feature of the radio communication terminal according to the present invention relates to the first to sixth features, wherein the transmission circuit performs the transmission according to an orthogonal frequency division multiple access scheme or a single carrier frequency division multiple access scheme. The gist is to transmit a signal.

  A feature of the transmission circuit of the present invention is a superheterodyne or double superheterodyne transmission circuit (transmission circuit 120) used in a radio communication system (radio communication system 10) employing a frequency division duplex system. A first mode having an amplifier (amplifier 141) connected to a power supply switch (switch SW3) for switching power supply or not, and a first bandpass filter (bandpass filter 142) connected to the output of the amplifier. Intermediate mode band circuit (switch SW3, band pass filter 142) and second mode intermediate band configured by a second band pass filter (band pass filter 143) having a smaller out-of-band attenuation than the first band pass filter. A frequency band circuit (bandpass filter 143) and a transmission signal in an intermediate frequency band; A first switch (switch SW1) that is input to either the 1-mode intermediate frequency band circuit or the second-mode intermediate frequency band circuit, and a mixer (mixer) for performing conversion from the intermediate frequency band to the radio frequency band 151) and a second switch (switch SW2) that inputs an output signal of either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit to the mixer. .

  The transmission control method of the present invention is characterized by a duplexer connected to an antenna, for attenuating a transmission signal outside the transmission band and attenuating a reception signal outside the reception band having a frequency band different from the transmission band, and via the duplexer. A transmission circuit configured to transmit the transmission signal; and a reception circuit configured to receive the reception signal via the duplexer, wherein the transmission circuit has a power consumption and out of band than the first mode or the first mode. A transmission control method used in a radio communication terminal including an intermediate frequency band circuit that processes the transmission signal in an intermediate frequency band in any one of the second modes having a small attenuation amount, wherein the transmission control method uses the duplexer via the duplexer. Leaking into the reception band and detecting the reception quality level reflecting the power of the transmission signal received by the reception circuit; and the reception quality level The intermediate frequency band circuit is operated in the second mode when a predetermined condition capable of maintaining the reception characteristics of the receiving circuit is satisfied, and the intermediate frequency when the reception quality level does not satisfy the predetermined condition. And a step of operating the band circuit in the first mode.

  The present invention provides a wireless communication terminal, a transmission circuit, and a transmission control method capable of suppressing deterioration of reception characteristics of a reception circuit while reducing power consumption of the transmission circuit in a wireless communication system employing an FDD scheme. it can.

1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. It is a circuit block diagram which shows the circuit structure of the radio | wireless communication terminal which concerns on embodiment of this invention. It is a figure which shows the structural example of the table which the memory | storage part which concerns on embodiment of this invention has memorize | stored. It is a figure for demonstrating the example of NF calculation of the transmission circuit which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radio | wireless communication terminal which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the configuration of the wireless communication system, (2) the configuration of the wireless communication terminal, (3) the operation of the wireless communication terminal, (4) the effect, and (5) other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Radio Communication System FIG. 1 is a schematic configuration diagram of a radio communication system 10 according to the present embodiment. As shown in FIG. 1, the radio communication system 10 includes a radio communication terminal 100 and a radio base station 200. The wireless communication system 10 has a configuration based on the LTE (Long Term Evolution) standard standardized by 3GPP (3rd Generation Partnership Project).

  For downlink communication of the radio communication system 10, that is, transmission from the radio base station 200 to the radio communication terminal 100, an OFDMA scheme, which is one of multicarrier communication schemes, is employed. Further, the SC-FDMA method, which is one of the single carrier communication methods, is employed for uplink communication of the wireless communication system 10, that is, transmission from the wireless communication terminal 100 to the wireless base station 200.

  The wireless communication system 10 employs the FDD method as a duplex method. That is, the frequency band used for uplink communication is different from the frequency band used for downlink communication.

  The wireless communication system 10 employs transmission power control. In uplink communication, the radio base station 200 periodically issues a transmission power control instruction for controlling the transmission power of the radio communication terminal 100 so as to keep the power of the received signal from the radio communication terminal 100 constant. To 100. In downlink communication, the radio communication terminal 100 periodically issues a transmission power control instruction for controlling the transmission power of the radio base station 200 so as to keep the power of the received signal from the radio base station 200 constant. 200.

  In addition, adaptive modulation is employed for each of uplink communication and downlink communication of the wireless communication system 10. In adaptive modulation, the modulation scheme is dynamically switched. Such a modulation scheme is also called a modulation class or an MCS level. In the wireless communication system 10 adopting adaptive modulation, a plurality of modulation schemes are determined in advance, each modulation scheme is provided with a required reception quality level, and any one of these modulation schemes is selected. Selected.

(2) Configuration of Radio Communication Terminal Next, regarding the configuration of the radio communication terminal 100, (2.1) schematic configuration of radio communication terminal, (2.2) configuration of transmission circuit, (2.3) NF of transmission circuit This will be described in the order of calculation examples.

(2.1) Schematic Configuration of Radio Communication Terminal FIG. 2 is a circuit configuration diagram showing a circuit configuration of the radio communication terminal 100. As illustrated in FIG. 2, the wireless communication terminal 100 includes an antenna 101, a duplexer 110, a transmission circuit 120, a reception circuit 170, a control unit 180, and a storage unit 190.

  The duplexer 110 is connected to the antenna 101, attenuates transmission signals outside the transmission band, and attenuates reception signals outside the reception band having a frequency band different from the transmission band. Specifically, the duplexer 110 includes a band-pass filter 111 that attenuates transmission signals outside the transmission band, and a band-pass filter 112 that attenuates reception signals outside the reception band.

  The transmission circuit 120 transmits a transmission signal via the duplexer 110. In the present embodiment, the transmission circuit 120 uses a double superheterodyne method including two intermediate frequency (IF) bands. The transmission circuit 120 includes an IF band circuit 140 that processes an IF band transmission signal in either the normal mode (first mode) or the low power consumption mode (second mode). In the low power consumption mode, the power consumption and out-of-band attenuation of the transmission circuit 120 are smaller than in the normal mode.

  The reception circuit 170 receives a reception signal via the duplexer 110 and demodulates the reception signal modulated by the radio base station 200 using a modulation scheme according to adaptive modulation.

  The control unit 180 is constituted by a CPU, for example, and controls various functions provided in the wireless communication terminal 100. The storage unit 190 is configured by a memory, for example, and stores various information used for control and the like in the wireless communication terminal 100.

  The control unit 180 leaks into the reception band from the transmission circuit 120 via the duplexer 110 and detects the reception quality level reflecting the power of the transmission signal received by the reception circuit 170. In the present embodiment, the control unit 180 detects a reception signal-to-noise power ratio (hereinafter, reception SNR) as the reception quality level.

  The received SNR represents a ratio between the power of the received signal (that is, the desired signal) received by the receiving circuit 170 from the radio base station 200 and the power of the signal other than the desired signal (that is, noise) received by the receiving circuit 170. . The reception SNR measurement may be performed by either the reception circuit 170 or the control unit 180. The control unit 180 detects the degree of interference (noise) that the transmission circuit 120 gives to the reception circuit 170 by detecting the reception SNR thus measured.

  In addition to the received SNR, the control unit 180 detects a required SNR that is a required reception quality level required for a modulation scheme being used in downlink communication. The association between the modulation scheme in adaptive modulation and the required SNR of the modulation scheme is stored in advance in the storage unit 190 as shown in FIG. In the example of FIG. 3, the required SNR “18.1 [dB]” is associated with the modulation scheme “QPSK”, and the required SNR “21.9 [dB]” is associated with the modulation scheme “16QAM”. The required SNR “30.5 [dB]” is associated with “64QAM”. The control unit 180 detects a modulation scheme in use in downlink communication, and detects a required SNR corresponding to the detected modulation scheme from the storage unit 190.

  In the normal mode, when the reception SNR satisfies a predetermined condition capable of maintaining the reception characteristics of the reception circuit 170, that is, when the reception SNR satisfies the required SNR, the control unit 180 switches the IF band circuit 140 to the low power consumption mode. . As a result, the power consumption of the IF band circuit 140 is reduced as compared with the normal mode.

  On the other hand, in the low power consumption mode, when the reception SNR does not satisfy a predetermined condition for maintaining the reception characteristics of the reception circuit 170, that is, when the reception SNR does not satisfy the required SNR, the control unit 180 causes the IF band circuit 140 to Switch to normal mode. Thereby, the reception characteristic of the receiving circuit 170 is improved as compared with that in the low power consumption mode.

  The control unit 180 detects RSSI that is a reception power level indicating the power of the reception signal (that is, the desired signal) received by the reception circuit 170 from the radio base station 200. In the present embodiment, the control unit 180 selects either the low power consumption mode or the normal mode in consideration of RSSI. The RSSI measurement may be performed by either the receiving circuit 170 or the control unit 180. The control unit 180 grasps the level of the received signal received by the receiving circuit 170 based on the RSSI thus measured.

  The control unit 180 compares the detected RSSI with the RSSI threshold (reception power level threshold). The RSSI threshold is stored in advance in the storage unit 190 as shown in FIG. In the example of FIG. 3, “−73.0 [dBm]” is stored as the RSSI threshold. When the RSSI is higher than the RSSI threshold, the influence of the interference that the transmission circuit 120 has on the reception circuit 170 can be ignored. Therefore, the control unit 180 preferentially selects the low power consumption mode over the normal mode. On the other hand, when the RSSI is lower than the RSSI threshold, the influence of the interference that the transmission circuit 120 has on the reception circuit 170 cannot be ignored. Therefore, the control unit 180 selects the normal mode in preference to the low power consumption mode. .

(2.2) Configuration of Transmission Circuit Next, the configuration of the transmission circuit 120 will be described in detail. By using the double superheterodyne method, two IF bands, the first IF band and the second IF band, are required. The transmission circuit 120 includes a D / A converter 121, a low-pass filter 122, an amplifier 123, a mixer 131, a local oscillator 132, a switch SW1 (first switch), an amplifier 141, a band-pass filter 142 (first band-pass filter), a band It has a pass filter 143 (second band pass filter), a switch SW2, a switch SW3 (power supply switch), a mixer 151, a local oscillator 152, a band pass filter 161, an amplifier 162, a step attenuator 163, an amplifier 164, and an amplifier 165. In the present embodiment, the amplifier 141, the band pass filter 142, and the band pass filter 143 constitute an IF band circuit 140 that processes an IF band transmission signal in either the normal mode or the low power consumption mode.

  The D / A converter 121 converts a digital signal from a modulation circuit (not shown) of the transmission circuit 120 into a second IF band transmission signal (analog signal). The low pass filter 122 is connected to the output of the D / A converter 121 and attenuates the low frequency component of the second IF band transmission signal. The amplifier 123 is connected to the output of the low pass filter 122 and amplifies the output signal of the low pass filter 122.

  The mixer 131 is connected to the outputs of the amplifier 123 and the local oscillator 132. The mixer 131 mixes the output signal of the amplifier 123 and the oscillation signal generated by the local oscillator 132, and converts the mixed signal into a transmission signal in the first IF band, which is a higher frequency band than the second IF band. The transmission signal in the first IF band is input to the switch SW1.

  The switch SW1 has one input and two outputs. Switching of the switch SW1 is controlled by the control unit 180. An amplifier 141 is connected to one output of the switch SW1. The amplifier 141 is connected to a switch SW3 that switches whether power is supplied to the amplifier 141. The amplifier 141 amplifies the output signal of the switch SW1. The amplifier 141 is used to avoid NF degradation in the IF band. A band pass filter 142 is connected to the output of the amplifier 141. The band pass filter 142 attenuates signal components outside the pass band of the transmission signal in the first IF band. In the present embodiment, the amplifier 141 and the band pass filter 142 constitute a first mode IF band circuit.

  A band pass filter 143 is connected to the other output of the switch SW1. The band pass filter 143 attenuates signal components outside the pass band of the transmission signal in the first IF band. The band pass filter 143 has a smaller out-of-band attenuation than the band pass filter 142. That is, since the band-pass filter 143 has a smaller pass loss than the band-pass filter 142, it is possible to suppress NF degradation without providing an amplifier. In the present embodiment, the bandpass filter 143 constitutes a second mode IF band circuit. The switch SW1 is used to input the first IF band transmission signal to either the first mode IF band circuit or the second mode IF band circuit.

  The switch SW2 has two inputs and one output. Switching of the switch SW2 is controlled by the control unit 180. The output of the band pass filter 142 is connected to one input of the switch SW2. The output of the band pass filter 143 is connected to the other input of the switch SW2. That is, the switch SW2 is used to input the output signal of either the first mode IF band circuit or the second mode IF band circuit to the mixer 151.

  A mixer 151 is connected to the output of the switch SW2. The mixer 151 mixes the output signal of the switch SW2 and the oscillation signal generated by the local oscillator 152, and converts it into a transmission signal in a radio frequency (RF) band that is a higher frequency band than the IF band. A band pass filter 161 is connected to the output of the mixer 151.

  The bandpass filter 161, the amplifier 162, the step attenuator 163, the amplifier 164, and the amplifier 165 constitute an RF band circuit 160 that processes an RF band transmission signal. The band pass filter 161 attenuates signal components outside the pass band in the RF band transmission signal. An amplifier 162 is connected to the output of the band pass filter 161. The amplifier 162 amplifies the output signal of the band pass filter 161. A step attenuator 163 used for transmission power control is connected to the output of the amplifier 162. The step attenuator 163 attenuates the output signal of the amplifier 162 under the control of the control unit 180. An amplifier 164 is connected to the output of the step attenuator 163, and an amplifier 165 is connected to the output of the amplifier 164. Each of the amplifier 164 and the amplifier 165 amplifies the RF band transmission signal.

  For transmission circuit 120 configured as described above, control unit 180 switches switch SW1 and switch SW2 to the first mode IF band circuit side in the normal mode, and supplies power to amplifier 141 using switch SW3. Supply. In the low power consumption mode, control unit 180 switches switch SW1 and switch SW2 to the second mode IF band circuit side and stops supplying power to amplifier 141 using switch SW3.

  Hereinafter, the operation of the transmission circuit 120 will be described. The band-pass filter 142 and the band-pass filter 143 attenuate the frequency band limitation and the frequency component outside the band. The band-pass filter 142 and the band-pass filter 143 attenuate the frequency component outside the band. Adjacent channel leakage power is determined. In FDD communication, the characteristics of out-of-band spurious naturally satisfy the standard, and together with the characteristics of the duplexer 110, it also becomes interference power to the reception band and greatly affects the reception characteristics of the reception circuit 170. .

  The transmission power is determined by the control unit 180 setting the step attenuator 163. The control unit 180 controls the switch SW1, the switch SW2, and the switch SW3 according to the set value of the step attenuator 163. When the step attenuator 163 is set below the transmission power level at which the out-of-band spurious / adjacent channel leakage power sufficiently satisfies the standard, the control unit 180 sets the switch SW1 and the switch SW2 to the second mode IF band circuit (bandpass filter). 143) switch to the side. Since the band-pass filter 143 has low loss, there is no deterioration of NF in the IF band, and power consumption is reduced by stopping power supply to the amplifier 141.

  Even if out-of-band spurious / adjacent channel leakage power is within the standard, there may be cases where the reception band is disturbed. For example, in the LTE standard, the reception sensitivity in the 5 MHz band is defined as -101.6 dBm / 5 MHz (QPSK). Since the required SNR in QPSK is -1.0 dB, the allowable noise level is -100.6 dBm / 5 MHz. The interference level leaking from the transmission circuit 120 into the reception circuit 170 must be less than or equal to this number. That is, the reception characteristics of the reception circuit 170 may not be maintained simply by satisfying the standards for out-of-band spurious and adjacent channel leakage power. Therefore, the control unit 180 also controls the switch SW1, the switch SW2, and the switch SW3 within a range that does not affect the reception characteristics in consideration of the RSSI, the reception SNR, and the reception modulation method (required SNR). The received SNR that can obtain sufficient communication quality can be determined from the modulation scheme of the received signal. Then, by measuring the RSSI / received SNR, it is possible to determine the interference power to the allowable reception band.

(2.3) Transmission Circuit NF Calculation Example Next, an NF calculation example in the transmission circuit 120 will be described. NF is an index indicating the noise characteristics of circuit elements such as amplifiers, and indicates how much the SNR on the output side deteriorates relative to the SNR on the input side. For example, if the SNR on the input side is 20 dB and the SNR on the output side deteriorates to 15 dB, the noise figure of this circuit element is 5 dB. The calculation formula of the noise figure F is shown below.

  Equation (2) represents the noise figure F in decibels.

Also, the input noise is defined by Ni = kTB, and if So / Si is gain G, equation (1) is expressed by (3). The output noise No is obtained by amplifying the input noise Ni with a gain G and further adding noise Na generated therein, and can also be expressed by equation (4).

When considering the noise figure in a circuit configuration in which multi-stage circuit elements are connected, the total noise figure Ftotal is shown below.

  Equation (6) is converted to dB.

  4A shows the D / A converter 121 (DAC), the low-pass filter 122 (LPF), the amplifier 123 (2nd Amp), the mixer 131 (IF Mixer), and the amplifier 141 (1st IF Amp) shown in FIG. It is a figure which shows the example which calculated the noise figure in the band pass filter 142 (IF Filter1) using said formula. On the other hand, FIG. 4B is a diagram illustrating an NF calculation example when the connection positions of the amplifier 141 (1st IF Amp) and the band pass filter 142 (IF Filter 1) are reversed in the circuit configuration of FIG. That is, in FIG. 4B, it is assumed that the amplifier 141 (1st IF Amp) is connected to the output of the band pass filter 142 (IF Filter 1). From FIG. 4A and FIG. 4B, it can be seen that the circuit configuration of FIG. 2 is excellent in NF.

(3) Operation of Radio Communication Terminal FIG. 5 is a flowchart showing the operation of the radio communication terminal 100.

  In step S100, the reception circuit 170 receives the transmission power control instruction transmitted from the radio base station 200. The transmission power control instruction is, for example, an instruction to increase or decrease the transmission power by a predetermined level. In step S101, the control unit 180 determines the transmission power level in accordance with the transmission power control instruction received by the reception circuit 170.

  In step S102, control unit 180 determines whether or not the transmission power level determined in step S100 is equal to or less than a transmission power level threshold. If the transmission power level is less than or equal to the transmission power level threshold, the process proceeds to step S103. On the other hand, when the transmission power level exceeds the transmission power level threshold, the process proceeds to step S114. In step S114, control unit 180 sets IF band circuit 140 to the normal mode. In step S114, control unit 180 sets step attenuator 163 according to the transmission power level determined in step S100.

  In step S <b> 103, the control unit 180 detects RSSI in the receiving circuit 170. In step S104, the control unit 180 determines whether the RSSI exceeds the RSSI threshold. If the RSSI exceeds the RSSI threshold, the process proceeds to step S112. On the other hand, if the RSSI is equal to or less than the RSSI threshold, the process proceeds to step S105. In step S105, the control unit 180 detects a reception modulation scheme that is a modulation scheme in use in downlink communication. In step S106, the control unit 180 detects a required reception SNR that is a required SNR corresponding to the reception modulation scheme.

  In step S107, the control unit 180 detects the received SNR and determines whether the received SNR satisfies the required reception SNR. If the received SNR satisfies the required reception SNR, that is, if the received SNR exceeds the required reception SNR, the process proceeds to step S108. In step S108, control unit 180 sets IF band circuit 140 to the low power consumption mode. In step S109, control unit 180 sets step attenuator 163 according to the transmission power level determined in step S100.

  On the other hand, if the received SNR does not satisfy the required reception SNR in step S107, that is, if the received SNR is lower than the required reception SNR, the process proceeds to step S110. In step S110, control unit 180 sets IF band circuit 140 to the normal mode. In step S111, control unit 180 sets step attenuator 163 according to the transmission power level determined in step S100.

  In step S116, the transmission circuit 120 transmits a transmission signal. Note that the operation flow shown in FIG. 5 is repeatedly executed at predetermined time intervals.

(4) Effect According to the wireless communication terminal 100, the control unit 180 operates the IF band circuit 140 in the low power consumption mode when the received SNR satisfies the required SNR. Since the low power consumption mode consumes less power than the normal mode, the power consumption of the transmission circuit 120 can be reduced. The control unit 180 operates the IF band circuit 140 in the normal mode when the reception SNR does not satisfy the required SNR. Since the normal mode has a larger out-of-band attenuation than the low power consumption mode, the power of the transmission signal leaking into the reception band can be reduced, and deterioration of the reception characteristics of the reception circuit 170 can be suppressed.

  In the present embodiment, the control unit 180 operates the IF band circuit 140 in the normal mode when the transmission power level exceeds a predetermined transmission power level threshold. The fact that the transmission power level exceeds the transmission power level threshold means that the out-of-band spurious characteristics / adjacent channel leakage power is outside the standard. In such a case, by operating the IF band circuit 140 in the normal mode, the out-of-band spurious characteristics and the adjacent channel leakage power can be kept within the standard.

  In the present embodiment, the control unit 180 operates the IF band circuit 140 in the low power consumption mode when the RSSI exceeds the RSSI threshold. When the RSSI exceeds the RSSI threshold value, that is, when the RSSI is high, the influence of the transmission signal leaking into the reception band can be ignored. Therefore, the IF band circuit 140 is operated in the low power consumption mode, thereby consuming the transmission circuit 120. Electric power can be reduced.

  In the present embodiment, the first mode IF band circuit includes an amplifier 141 and a band-pass filter 142 connected to the output side of the amplifier 141. Thus, by connecting the band pass filter 142 to the output side of the amplifier 141, NF can be improved as compared with the case where the band pass filter 142 is connected to the input side of the amplifier 141.

(5) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the transmission circuit 120 has a configuration according to the double superheterodyne system including two IF bands, but may be a superheterodyne system including only one IF band.

  In the above-described embodiment, the reception SNR is used as the reception quality level that reflects the power of the transmission signal leaking into the reception band. However, the reception SNR is not limited to the reception SNR, and the reception error rate (bit error rate or block error rate). ) Etc. may be used.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  SW1, SW2, SW3 ... switch, 10 ... wireless communication system, 100 ... wireless communication terminal, 101 ... antenna, 110 ... duplexer, 111, 112, 142, 143 ... band pass filter, 120 ... transmission circuit, 121 ... D / A Converter: 122 ... Low pass filter, 123 ... Amplifier, 131,151 ... Mixer, 132,152 ... Local oscillator, 140 ... IF band circuit, 141 ... Amplifier, 160 ... RF band circuit, 161 ... Band pass filter, 162,164 165, amplifier, 163 step attenuator, 170 receiving circuit, 180 control unit, 190 storage unit, 200 radio base station

Claims (9)

A duplexer connected to the antenna for attenuating a transmission signal outside the transmission band and attenuating a reception signal outside the reception band having a frequency band different from the transmission band;
A transmission circuit for transmitting the transmission signal via the duplexer;
A wireless communication terminal having a receiving circuit for receiving the received signal via the duplexer,
A control unit that detects a reception quality level reflecting the power of the transmission signal received by the reception circuit from the transmission circuit via the duplexer, and controls the transmission circuit based on the reception quality level;
The transmission circuit includes an intermediate frequency band circuit that processes the transmission signal in the intermediate frequency band in either the first mode or the second mode in which power consumption and out-of-band attenuation are smaller than in the first mode. Including
The controller is
When the reception quality level satisfies a predetermined condition capable of maintaining the reception characteristics of the reception circuit, the intermediate frequency band circuit is operated in the second mode,
A radio communication terminal that operates the intermediate frequency band circuit in the first mode when the reception quality level does not satisfy the predetermined condition. The controller is
Further detecting a transmission power level indicating the power of the transmission signal;
When the transmission power level is below a predetermined transmission power level threshold and the reception quality level satisfies the predetermined condition, the intermediate frequency band circuit is operated in the second mode,
The wireless communication according to claim 1, wherein the intermediate frequency band circuit is operated in the first mode when the transmission power level is lower than the transmission power level threshold and the reception quality level does not satisfy the predetermined condition. Terminal. The controller is
Further detecting a received power level indicating the power of the received signal received by the receiving circuit;
The radio communication terminal according to claim 1, wherein when the received power level exceeds a predetermined received power level threshold, the intermediate frequency band circuit is operated in the second mode. The controller is
When the received power level is below the received power level threshold and the received quality level satisfies the predetermined condition, the intermediate frequency band circuit is operated in the second mode,
The wireless communication according to claim 3, wherein the intermediate frequency band circuit is operated in the first mode when the transmission power level is lower than the reception power level threshold and the reception quality level does not satisfy the predetermined condition. Terminal. The receiving circuit receives the received signal modulated by a modulation method according to adaptive modulation;
The controller is
Further detecting the required reception quality level required for the modulation scheme;
When the reception quality level exceeds the required reception quality level, the intermediate frequency band circuit is operated in the second mode;
The radio communication terminal according to claim 1, wherein the intermediate frequency band circuit is operated in the first mode when the reception quality level is lower than the required reception quality level. The transmission circuit includes a mixer for performing conversion from the intermediate frequency band to a radio frequency band,
The intermediate frequency band circuit is:
A first mode intermediate frequency band circuit having an amplifier to which a power supply switch for switching power supply is connected, and a first bandpass filter connected to the output of the amplifier;
An intermediate frequency band circuit for a second mode configured by a second bandpass filter having a smaller out-of-band attenuation than the first bandpass filter;
A first switch for inputting the transmission signal in the intermediate frequency band to either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit;
A second switch for inputting an output signal of either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit to the mixer;
The controller is
In the first mode, the first switch and the second switch are switched to the first mode intermediate frequency band circuit side, and power is supplied to the amplifier using the power supply switch.
The first switch and the second switch are switched to the second mode intermediate frequency band circuit side in the second mode, and power supply to the amplifier is stopped using the power supply switch. The wireless communication terminal according to any one of claims 1 to 5.   The radio transmission terminal according to any one of claims 1 to 6, wherein the transmission circuit transmits the transmission signal according to an orthogonal frequency division multiple access scheme or a single carrier frequency division multiple access scheme. A superheterodyne method or a double superheterodyne method transmission circuit used in a radio communication system employing a frequency division duplex method,
A first mode intermediate frequency band circuit having an amplifier to which a power supply switch for switching power supply is connected, and a first bandpass filter connected to the output of the amplifier;
An intermediate frequency band circuit for a second mode configured by a second bandpass filter having a smaller out-of-band attenuation than the first bandpass filter;
A first switch for inputting an intermediate frequency band transmission signal to either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit;
A mixer for performing conversion from the intermediate frequency band to a radio frequency band;
A transmission circuit comprising: a second switch that inputs an output signal of either the first mode intermediate frequency band circuit or the second mode intermediate frequency band circuit to the mixer. A duplexer connected to the antenna for attenuating a transmission signal outside the transmission band and attenuating a reception signal outside the reception band having a frequency band different from the transmission band;
A transmission circuit for transmitting the transmission signal via the duplexer;
A receiving circuit for receiving the received signal via the duplexer;
The transmission circuit includes an intermediate frequency band circuit that processes the transmission signal in the intermediate frequency band in either the first mode or the second mode in which power consumption and out-of-band attenuation are smaller than in the first mode. A transmission control method used for a wireless communication terminal including:
Leaking into the reception band from the transmission circuit via the duplexer, and detecting a reception quality level reflecting the power of the transmission signal received by the reception circuit;
When the reception quality level satisfies a predetermined condition capable of maintaining the reception characteristics of the reception circuit, the intermediate frequency band circuit is operated in the second mode;
And a step of operating the intermediate frequency band circuit in the first mode when the reception quality level does not satisfy the predetermined condition.

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