JP4920504B2 - Wireless communication terminal device and automatic frequency control method - Google Patents

Description

  The present invention relates to a radio communication terminal apparatus and an automatic frequency control method for receiving, for example, a digital television broadcast.

  2. Description of the Related Art In recent years, a mobile phone equipped with a digital TV tuner has been known as a result of higher functionality of the mobile phone. In addition, with the advancement of functions of mobile phones, high-density mounting inside mobile phone devices has progressed, and influences such as heat generation and noise wrap-around within the mobile phone are increasing. At present, digital television tuners are often used in small modularized products, and the effects of heat generation and noise wraparound inside the module cannot be ignored.

  In general, a mobile phone includes a reference signal oscillation circuit dedicated to a digital TV tuner, and performs reception processing based on a reference frequency generated from the reference signal oscillation circuit. In tuner modules and mobile phones that are mounted with high density, the frequency of the reference oscillator fluctuates due to sudden changes in the amount of heat generation or switching on / off of the power supply of some circuits, such as BER (Bit Error Rate) characteristics. Reception performance may deteriorate.

  Since the digital TV tuner is equipped with an automatic frequency control circuit, it is sufficiently resistant to stationary frequency errors and gradual frequency fluctuations. However, when the above rapid frequency fluctuation occurs, that is, when the gradient of the frequency change is large, automatic frequency control cannot follow and BER deterioration occurs. Automatic frequency control can improve tracking performance by controlling the time constant. However, if tracking performance is increased, it also changes with respect to noise, reducing noise resistance and reducing reception performance. descend.

  Therefore, recent cellular phones are required to achieve both reduction in performance deterioration due to sudden frequency fluctuations accompanying processing in the cellular phone and maintenance of high reception performance in a normal state.

Japanese Patent Application Laid-Open No. 2004-228561 realizes both a stable automatic frequency control operation and a quick pull-in operation with respect to an automatic frequency control device for a receiver in a television receiver or a VTR. In Patent Document 1, the presence / absence of a synchronization signal is detected, and when there is no synchronization signal, that is, when television reception is not performed, the filter time constant of the automatic frequency control loop is reduced to shorten the pull-in time. On the other hand, when there is a synchronization signal, that is, when receiving a television, the filter time constant of the automatic frequency control loop is increased to stabilize the operation and increase the resistance to noise.
Japanese Patent Laid-Open No. 5-37301

  However, in Patent Document 1, since the high-speed pull-in mode is not established unless the synchronization signal disappears, there is a problem that a good reception state cannot be maintained if a sudden frequency fluctuation occurs during television reception.

  The present invention has been made in view of such points, and when performing specific processing that disturbs the reference frequency, automatic frequency control with high tracking performance is performed, so that reception performance is deteriorated due to sudden frequency fluctuations. An object of the present invention is to provide a radio communication terminal apparatus and an automatic frequency control method capable of achieving both reduction and maintaining high reception performance in a normal state.

The wireless communication terminal device according to the present invention includes a reference frequency generation unit that generates a reference frequency signal for receiving and processing a television broadcast signal, and detects a frequency error in the received signal of the television broadcast , and the detected frequency error A frequency error detecting means for outputting a frequency error signal indicating the frequency error signal, and a command for executing a specific internal process for causing a frequency fluctuation during reception of the television broadcast with respect to the reference frequency signal generated by the reference frequency generating means. Specific processing execution notifying means for notifying timing, control means for setting a smaller time constant when the notification is received than when not receiving the notification, and the frequency error with the time constant set by the control means A loop filter for passing the signal and integrating the frequency error signal, and a frequency integrated by the loop filter Local signal generating means for generating a local signal of a predetermined oscillation frequency from the difference signal, orthogonal detection means for compensating for the frequency error in the received signal by orthogonally detecting the received signal with the generated local signal, The structure which comprises is taken.

An automatic frequency control method of the present invention includes a step of generating a reference frequency signal for receiving and processing a television broadcast signal, a frequency error in the received signal of the television broadcast , and a frequency indicating the detected frequency error A step of outputting an error signal, a step of notifying a timing of issuing an execution instruction of a specific internal process that causes a frequency fluctuation during reception of the television broadcast with respect to the reference frequency signal, and when receiving the notification Setting a time constant in the loop filter that is smaller than when not receiving the notification, the loop filter passing the frequency error signal and integrating the frequency error signal during the passage; Generating a local signal having a predetermined oscillation frequency from the integrated frequency error signal; And to comprise the steps of: compensating the frequency error in the received signal by quadrature detection the received signal with the local signal.

  According to the present invention, when performing specific processing that disturbs the reference frequency, automatic frequency control with high follow-up performance is performed to reduce deterioration in reception performance due to sudden frequency fluctuations and high reception performance in a normal state. It is possible to achieve both maintenance and maintenance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of radio communication terminal apparatus 100 according to Embodiment 1 of the present invention.

  The wireless communication terminal apparatus 100 includes a digital television tuner unit 150. The digital television tuner unit 150 includes an internal clock generation circuit 102, an RF circuit 104, an analog / digital (hereinafter referred to as “A / D”) unit 105, Quadrature detection unit 106, low-pass filter (hereinafter referred to as "LPF") 107, OFDM demodulation circuit 108, decoding circuit 109, control circuit 111, frequency error detection unit 114, variable loop filter 115, and numerically controlled oscillator (Numerical Controlled Oscillator: (Hereinafter referred to as “NCO”) 116.

  The TV tuner reference frequency generation unit 101 is, for example, a crystal oscillation circuit, generates a reference frequency signal for receiving and processing a digital television broadcast signal, and outputs the generated reference frequency signal to the internal clock generation circuit 102. Note that the TV tuner reference frequency generation unit 101 is often included in the tuner IC, and at that time, the crystal resonator is externally attached to the tuner IC.

  The internal clock generation circuit 102 generates various clocks used inside the digital television tuner unit 150 using the reference frequency signal input from the TV tuner reference frequency generation unit 101. The internal clock generation circuit 102 supplies the generated various clocks to the RF circuit 104 and other circuits.

  The antenna 103 receives a digital television broadcast signal and outputs it to the RF circuit 104.

  The RF circuit 104 amplifies the digital television broadcast signal input from the antenna 103, selects a signal of a predetermined channel from the amplified digital television broadcast signal, and converts the frequency into a Low-IF signal. The RF circuit 104 performs automatic gain control processing so that the input level of the A / D unit 105 is constant. Then, the RF circuit 104 outputs the Low-IF signal after frequency conversion and automatic gain control processing to the A / D unit 105.

  The A / D unit 105 A / D converts the Low-IF signal input from the RF circuit 104 and outputs the signal to the quadrature detection unit 106.

  The quadrature detection unit 106 performs quadrature detection on the digital Low-IF signal input from the A / D unit 105 using the local signal input from the NCO 116, and outputs the I component and Q component of the digital baseband signal to the LPF 107.

  The LPF 107 removes the sum frequency component generated by the quadrature detection from the I component and the Q component of the digital baseband signal input from the quadrature detection unit 106 and outputs the result to the OFDM demodulation circuit 108 and the frequency error detection unit 114.

  The OFDM demodulation circuit 108 generates a demodulated signal by OFDM demodulating the digital baseband signal composed of the I component and Q component input from the LPF 107, and outputs the generated demodulated signal to the decoding circuit 109.

  The decoding circuit 109 performs decoding processing such as deinterleaving and error correction on the demodulated signal input from the OFDM demodulation circuit 108, and outputs the decoded digital broadcast signal to the outside. As a result, the wireless communication terminal device 100 can display an image by digital broadcasting on a display screen (not shown).

  The terminal control unit 110 controls the entire wireless communication terminal device 100. Also, the terminal control unit 110 issues execution instructions for various processes at a predetermined timing. For example, the terminal control unit 110 performs channel selection, initialization of each block of the digital TV tuner unit 150, stop processing of each block of the digital TV tuner unit 150, start-up processing of the transmission system amplifier, stop processing of the transmission system amplifier, Issues execution instructions for various processes for starting the operation of the charging circuit and stopping the operation of the charging circuit. Here, the transmission amplifier is an amplifier for transmitting a signal of a cellular communication system, for example, an amplifier for transmitting an audio signal when making a call using a mobile phone function provided in the communication terminal device 100.

  The control circuit 111 controls each block of the digital television tuner unit 150. For example, the control circuit 111 receives an instruction to execute channel selection from the terminal control unit 110, initialization of each block of the digital TV tuner unit 150, or stop processing of each block of the digital TV tuner unit 150, and the RF circuit 104. The Lo frequency is set, each block is initialized, or each block is stopped.

  The specific process execution notification unit 112 collects timings at which various process execution instructions are issued from the terminal control unit 110. Then, the specific process execution notifying unit 112 notifies the TV tuner AFC loop constant control unit 113 of the timing for issuing a specific process execution command that causes a sudden change in the reference frequency. For example, the specific processing execution notifying unit 112 issues a timing for issuing an execution command for starting a transmission system transmission amplifier as a timing for issuing a specific internal processing execution command that causes a sudden change in reference frequency. The timing for issuing the execution instruction for the stop process, the timing for issuing the execution instruction for starting the operation of the charging circuit, or the timing for issuing the execution instruction for stopping the operation of the charging circuit are notified. In addition, the output of the transmission amplifier differs depending on the distance between the radio communication terminal apparatus 100 and a base station (not shown). When the distance is short, the output of the transmission amplifier is low and the heat generation is low, so the automatic frequency control loop constant is always changed. There is no need. Therefore, the specific process execution notifying unit 112 may also collect transmission power setting information from the terminal control unit 110 and perform the above notification only when transmission power equal to or greater than a predetermined threshold is set. . Note that the terminal control unit 110 and the specific process execution notification unit 112 do not need to be separate devices (CPUs) and may be provided in the same device.

  As a control means, the TV tuner AFC loop constant control unit 113 instructs the variable loop filter 115 to set a smaller time constant when the notification is received from the specific process execution notification unit 112 than when the notification is not received. . Specifically, the TV tuner AFC loop constant control unit 113 receives the notification from the specific process execution notification unit 112, and does not receive the notification, the gain of the variable loop filter 115 or the smoothing parameter (filter At least one of the band, the moving average number, the forgetting factor, etc.) is instructed to switch to a setting with high follow-up in automatic frequency control. For example, the TV tuner AFC loop constant control unit 113 increases the gain of the variable loop filter 115 when starting the transmission system transmission amplifier, stopping the transmission system transmission amplifier, starting the operation of the charging circuit, or stopping the operation of the charging circuit. Alternatively, the bandwidth of the variable loop filter 115 is widened, and an instruction is given to restore the original setting after a predetermined time has elapsed. Note that the setting change need not necessarily be in two stages, and may be in three or more stages.

  The frequency error detection unit 114 detects a frequency error from the I component and Q component of the baseband signal input from the LPF 107. Then, the frequency error detector 114 outputs a frequency error signal as a detection result to the variable loop filter 115.

  The variable loop filter 115 sets a time constant according to an instruction from the TV tuner AFC loop constant control unit 113, passes the frequency error signal input from the frequency error detection unit 114 with the set time constant, and integrates the frequency error signal. To the NCO 116. Details of the configuration of the variable loop filter 115 will be described later.

  The NCO 116 serving as a local signal generating unit generates a local signal composed of a digital sine wave and a digital cosine wave having a predetermined transmission frequency from the frequency error signal input from the variable loop filter 115. Then, NCO 116 outputs the generated local signal to quadrature detection unit 106.

  Next, the configuration of the variable loop filter 115 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the variable loop filter 115. In FIG. 2, the variable loop filter 115 changes the setting of the gain coefficient and the forgetting coefficient. However, the present invention is not limited to this. If the time constant is changed, the instruction of the TV tuner AFC loop constant control unit 113 is used. Any parameter can be set according to

  The memory 201 stores a plurality of gain coefficients K at each address, and the multiplier 204 stores the gain coefficient K stored at the address indicated by the loop filter control signal input from the TV tuner AFC loop constant control unit 113. Output to.

  The memory 202 stores a plurality of forgetting factors α at each address, and the multiplier 205 uses the forgetting factor α stored at the address indicated by the loop filter control signal input from the TV tuner AFC loop constant control unit 113. Output to.

  The memory 203 stores a plurality of (1-α) values at each address, and stores them at the address indicated by the loop filter control signal input from the TV tuner AFC loop constant control unit 113 (1- The value of α) is output to the multiplier 206.

  The multiplier 204 multiplies the frequency error signal input from the frequency error detection unit 114 by the gain coefficient K stored in the memory 201 and outputs the result to the multiplier 205.

  Multiplier 205 multiplies the frequency error signal multiplied by K inputted from multiplier 204 by forgetting factor α stored in memory 202 and outputs the result to adder 207.

  Multiplier 206 multiplies the frequency error signal of the previous cycle input from delay unit 208 by (1-α) stored in memory 203 and outputs the result to adder 207.

  Adder 207 adds the frequency error signal multiplied by α input from multiplier 205 and the frequency error signal multiplied by (1−α) input from multiplier 206, and outputs the result to delayer 208 and adder 209.

  Delay device 208 delays the frequency error signal input from adder 207 by one cycle and outputs the delayed signal to multiplier 206.

  The adder 209 adds the frequency error signal input from the adder 207 and the frequency error signal of the previous cycle input from the delay unit 210, and outputs the addition result to the NCO 116 as a control signal.

  The delay unit 210 delays the frequency error signal input from the adder 209 by one cycle and outputs the delayed signal to the adder 209.

  In FIG. 2, the gain coefficient K and the forgetting factor α can be switched. However, the present invention is not limited to this, and only one of the gain coefficient K and the forgetting factor α may be switched. . In FIG. 2, the frequency error signal is multiplied by the gain coefficient K and the forgetting coefficient α by separate multipliers. However, the present invention is not limited to this, and the multiplication may be performed by one multiplier or multiplication by the multiplier. Instead, a bit shift may be performed. Further, although the moving average filter is used in FIG. 2, it is not limited to the moving average filter.

  Incidentally, in a cellular phone, the power amplifier used in the signal transmission system generates a very large amount of heat. Therefore, depending on the positional relationship between the digital TV tuner unit 150 and the transmission system transmission amplifier, the transmission system transmission amplifier generates heat. The frequency of the oscillator is greatly affected. That is, when a call or communication is started, that is, when the transmission system transmission amplifier is turned from OFF to ON, and when a call or communication is stopped, that is, when the transmission system transmission amplifier is turned from ON to OFF, the temperature is abrupt. Variation occurs and the reference frequency varies. When the reference frequency varies, the carrier frequency of the Low-IF signal that the RF circuit 104 selects and outputs is changed. When this change is abrupt, automatic frequency control cannot follow, and the frequency error increases and the BER characteristics deteriorate. Since the heat generation amount of the charging circuit is large, the influence on the frequency of the reference oscillator due to the heat generation of the charging circuit cannot be ignored depending on the positional relationship between the charging circuit and the digital TV tuner unit 150. Embodiment 1 of the present invention solves such a problem.

  Further, the position where the TV tuner reference frequency generation unit 101 is mounted in the wireless communication terminal apparatus 100 can be greatly reduced in performance deterioration due to a rapid frequency change by mounting it at a position where the temperature change is small.

  As described above, according to the first embodiment, when performing specific processing that disturbs the reference frequency, automatic frequency control with high follow-up performance is performed, thereby reducing deterioration in reception performance due to sudden frequency fluctuations. And maintaining high reception performance in the normal state can be achieved.

(Embodiment 2)
FIG. 3 is a block diagram showing a configuration of radio communication terminal apparatus 300 according to Embodiment 2 of the present invention.

  A wireless communication terminal device 300 illustrated in FIG. 3 adds a combining circuit 313 and a reception quality determination unit 314 to the wireless communication terminal device 100 according to Embodiment 1 illustrated in FIG. Instead of the A / D unit 105, the quadrature detection unit 106, the LPF 107, the OFDM demodulation circuit 108, the terminal control unit 110, the control circuit 111, and the specific process execution notification unit 112, the antennas 301 and 302, the RF circuits 303 and 304, A / D D units 305 and 306, quadrature detection units 307 and 308, LPFs 309 and 310, OFDM demodulation circuits 311 and 312, a terminal control unit 315, a control circuit 316, and a specific process execution notification unit 317. In FIG. 3, parts having the same configuration as in FIG.

  The wireless communication terminal apparatus 300 includes a digital television tuner unit 350 that is a diversity tuner. The digital television tuner unit 350 includes an internal clock generation circuit 102, a decoding circuit 109, a frequency error detection unit 114, a variable loop filter 115, an NCO 116, RF circuits 303 and 304, A / D units 305 and 306, quadrature detection units 307 and 308, LPFs 309 and 310, OFDM demodulation circuits 311 and 312, a synthesis circuit 313, a reception quality determination unit 314, and a control circuit 316 are included.

  The antenna 301 receives a digital television broadcast signal by single branch reception or diversity reception together with the antenna 302, and outputs the received digital television broadcast signal to the RF circuit 303.

  The antenna 302 receives a digital television broadcast signal by single branch reception or diversity reception together with the antenna 301, and outputs the received digital television broadcast signal to the RF circuit 304.

  The internal clock generation circuit 102 uses the reference frequency signal input from the TV tuner reference frequency generation unit 101 to generate various clocks to be used inside the digital television tuner unit 350. The internal clock generation circuit 102 supplies the generated various clocks to the RF circuit 303, the RF circuit 304, and other circuits.

  The RF circuit 303 switches between starting and receiving power supply and stopping without receiving power supply in accordance with the control of the control circuit 316. Further, the RF circuit 303 amplifies the digital television broadcast signal input from the antenna 301 when activated, selects a signal of a predetermined channel from the amplified digital television broadcast signal, and converts the frequency into a Low-IF signal. Convert. The RF circuit 303 performs automatic gain control processing so that the input level of the A / D unit 305 is constant. Then, the RF circuit 303 outputs the Low-IF signal after frequency conversion and automatic gain control processing to the A / D unit 305.

  The RF circuit 304 switches between starting when receiving power supply and stopping when receiving power supply, under the control of the control circuit 316. In addition, the RF circuit 304 amplifies the digital television broadcast signal input from the antenna 302 when activated, selects a signal of a predetermined channel from the amplified digital television broadcast signal, and converts it to a Low-IF signal. Convert. The RF circuit 304 performs automatic gain control processing so that the input level of the A / D unit 306 is constant. Then, the RF circuit 304 outputs the Low-IF signal after frequency conversion and automatic gain control processing to the A / D unit 306.

  The A / D unit 305 performs A / D conversion on the Low-IF signal input from the RF circuit 303 and outputs the signal to the quadrature detection unit 307.

  The A / D unit 306 performs A / D conversion on the Low-IF signal input from the RF circuit 304 and outputs the signal to the quadrature detection unit 308.

  The quadrature detection unit 307 performs quadrature detection on the digital Low-IF signal input from the A / D unit 305 using the local signal input from the NCO 116, and outputs the I component and Q component of the digital baseband signal to the LPF 309.

  The quadrature detection unit 308 performs quadrature detection on the digital Low-IF signal input from the A / D unit 306 using the local signal input from the NCO 116, and outputs the I component and Q component of the digital baseband signal to the LPF 310.

  The LPF 309 removes the sum frequency component generated by the quadrature detection from the I component and the Q component of the digital baseband signal input from the quadrature detection unit 307 and outputs the result to the OFDM demodulation circuit 311 and the frequency error detection unit 114.

  The LPF 310 removes the sum frequency component generated by the quadrature detection from the I component and the Q component of the digital baseband signal input from the quadrature detection unit 308 and outputs the result to the OFDM demodulation circuit 312 and the frequency error detection unit 114.

  The OFDM demodulation circuit 311 generates a demodulated signal by OFDM demodulating the digital baseband signal composed of the I component and Q component input from the LPF 309, and outputs the generated demodulated signal to the synthesis circuit 313 and the reception quality determination unit 314.

  The OFDM demodulating circuit 312 generates a demodulated signal by OFDM demodulating the digital baseband signal composed of the I component and the Q component input from the LPF 310, and outputs the generated demodulated signal to the synthesizing circuit 313 and the reception quality determining unit 314.

  The combining circuit 313 combines two demodulated signals input from the OFDM demodulating circuit 311 and the OFDM demodulating circuit 312. At this time, the combining circuit 313 uses maximum ratio combining that adds weights so that the combined S / N is maximized and adds the respective demodulated signals. Then, combining circuit 313 outputs the signal after the maximum ratio combining to decoding circuit 109.

  The decoding circuit 109 performs decoding processing such as deinterleaving and error correction on the signal after the maximum ratio combining input from the combining circuit 313, and outputs the digital broadcast signal after the decoding processing to the outside. As a result, the wireless communication terminal device 300 can display an image by digital broadcasting on a display screen (not shown).

  The reception quality judgment unit 314 detects BER or S / N using the demodulated signal input from the OFDM demodulator circuit 311 and the demodulated signal input from the OFDM demodulator circuit 312, and the detected value of BER or S / N and a predetermined threshold value Based on the comparison result, it is determined whether or not to receive diversity. Specifically, the reception quality determination unit 314 determines that the diversity reception should not be performed when the BER detection value is less than the threshold or when the S / N detection value is equal to or greater than the threshold, and the BER detection value is equal to or greater than the threshold. Or when the S / N detection value is less than the threshold value, it is determined that the diversity reception should be performed. Reception quality determination section 314 then outputs the determination result to control circuit 316.

  The terminal control unit 315 controls the entire wireless communication terminal device 300. Further, the terminal control unit 315 issues various processing execution instructions at a predetermined timing. For example, the terminal control unit 315 performs channel selection, initialization of each block of the digital TV tuner unit 350, stop processing of each block of the digital TV tuner unit 350, and various processes of switching between diversity reception and single branch reception. Issue an execution instruction.

  The control circuit 316 controls each block of the digital TV tuner unit 350. For example, the control circuit 316 receives an instruction to execute channel selection from the terminal control unit 315, initialization of each block of the digital TV tuner unit 350, or stop processing of each block of the digital TV tuner unit 350, and the RF circuit 303. 304, the Lo frequency is set, each block is initialized, or each block is stopped. The control circuit 316 controls switching between diversity reception and single branch reception when receiving an instruction to execute diversity reception or single branch reception switching processing from the terminal control unit 315. That is, when the determination result input from the reception quality determination unit 314 is diversity-received, the control circuit 316 performs control so that power is supplied to the RF circuit 303 and the RF circuit 304, and the reception quality determination unit 314. When the determination result input from the single-branch reception is performed, control is performed so that power is not supplied to one of the RF circuit 303 and the RF circuit 304 whose reception quality is degraded.

  The specific process execution notifying unit 317 extracts, from the control circuit 316, a timing for issuing an execution instruction for switching processing between diversity reception and single branch reception as a timing for issuing an execution instruction for specific internal processing that causes a sudden change in reference frequency. To do. Then, the specific process execution notifying unit 317 notifies the TV tuner AFC loop constant control unit 113 of the timing for issuing the execution instruction for the switching process of the extracted diversity reception and single branch reception.

  When receiving the notification from the specific process execution notification unit 317, the TV tuner AFC loop constant control unit 113 instructs the variable loop filter 115 to select a smaller time constant than when not receiving the notification. More specifically, the TV tuner AFC loop constant control unit 113 receives the notification from the specific process execution notification unit 317, rather than the case where the notification is not received, the gain of the variable loop filter 115 or the smoothing parameter (filter At least one of the band, the moving average number, the forgetting factor, etc.) is instructed to switch to a setting with high follow-up in automatic frequency control. For example, the TV tuner AFC loop constant control unit 113 increases the gain of the variable loop filter 115 or widens the band of the variable loop filter 115 when switching between diversity reception and single branch reception, and after a predetermined time has elapsed. Instruct to return to the original setting. Note that the setting change need not necessarily be in two stages, and may be in three or more stages.

  The frequency error detection unit 114 detects a frequency error from the I component and Q component of the baseband signal input from at least one of the LPF 309 or the LPF 310. Then, the frequency error detector 114 outputs a frequency error signal as a detection result to the variable loop filter 115.

  The NCO 116 generates a local signal composed of a digital sine wave and a digital cosine wave having a predetermined transmission frequency from the frequency error signal input from the variable loop filter 115. Then, the NCO 116 outputs the generated local signal to the quadrature detection unit 307 and the quadrature detection unit 308.

  The configuration of the variable loop filter 115 is the same as that shown in FIG.

  In addition, the position where the TV tuner reference frequency generation unit 101 in the wireless communication terminal apparatus 300 is mounted can be greatly reduced in performance degradation due to a rapid frequency change by mounting the TV tuner reference frequency generation unit 101 at a position where the temperature change is small.

  Incidentally, in the digital television tuner unit 350 having two receiving circuits, when processing for stopping one system is performed for power saving, temperature fluctuations caused by power changes in the analog circuit and voltage due to common impedance of the power supply Variations occur, and these change the reference frequency and degrade the BER characteristics. In this case, the power change and the heat generation amount change are relatively small, but since the heat source exists in the vicinity of the TV tuner reference frequency generation unit 101 which is a reference signal oscillation circuit, the temperature variation in the TV tuner reference frequency generation unit 101 is steep. And the influence on the frequency becomes large.

  Further, in the wireless communication terminal device 300, the temperature of the TV tuner reference frequency generation unit 101 changes due to the change in the amount of heat generated by turning on or off the power of the RF circuit 303 or the RF circuit 304, thereby changing the oscillation frequency. . In the wireless communication terminal device 300, the voltage of the oscillator changes due to the common impedance of the power supply when the power supply of the RF circuit 303 or the RF circuit 304 is turned on or off, thereby changing the oscillation frequency. The change of the oscillation frequency corresponds to the change of the carrier frequency (IF) when viewed from the OFDM demodulation circuit 311 and the OFDM demodulation circuit 312, and when this change is abrupt, automatic frequency control cannot follow the change, and the frequency error is increased. It becomes larger and the BER deteriorates.

  In addition, the frequency fluctuation caused by the temperature change starts abruptly with a slight delay after the RF circuit 303 or the RF circuit 304 is turned ON or OFF, and then continues to change gradually until thermal equilibrium is reached. On the other hand, the frequency fluctuation caused by the power supply undergoes a rapid frequency change immediately after the RF circuit 303 or the RF circuit 304 is turned on or off.

  Therefore, in the second embodiment, in accordance with the ON or OFF timing of the RF circuit 303 or the RF circuit 304, for example, the gain of the variable loop filter 115 is increased or the band is widened to follow the automatic frequency control. Is set to a high setting. Then, after a predetermined time elapses, the wireless communication terminal device 300, for example, reduces the gain of the variable loop filter 115 or narrows the band to return to a setting with high noise resistance.

  As described above, according to the second embodiment, by performing automatic frequency control with high followability at the timing of branch start processing or stop processing, it is possible to reduce deterioration in reception performance due to sudden frequency fluctuations and in a normal state. Both high reception performance can be maintained.

(Embodiment 3)
FIG. 4 is a block diagram showing a configuration of radio communication terminal apparatus 400 according to Embodiment 3 of the present invention.

  Radio communication terminal apparatus 400 shown in FIG. 4 is different from radio communication terminal apparatus 100 according to Embodiment 1 shown in FIG. 1 in that a terminal control unit is used instead of terminal control unit 110, except for TV tuner reference frequency generation unit 101. 402, a specific process execution notification unit 403 instead of the specific process execution notification unit 112, and a transmission system reference frequency generation unit 401 is added. In FIG. 4, parts having the same configuration as in FIG.

  The wireless communication terminal apparatus 400 includes a digital television tuner unit 450. The digital television tuner unit 450 includes an internal clock generation circuit 102, an RF circuit 104, an A / D unit 105, an orthogonal detection unit 106, an LPF 107, and an OFDM demodulation circuit 108. , A decoding circuit 109, a control circuit 111, a frequency error detection unit 114, a variable loop filter 115, and an NCO 116.

  The transmission system reference frequency generation unit 401 uses the reference frequency (CLK) at the time of cellular communication system data transmission as the reference frequency of the digital television tuner unit 450, and is a reference at the time of data transmission of the generated cellular communication system. The frequency signal is output to the internal clock generation circuit 102.

  The internal clock generation circuit 102 generates various clocks used inside the digital television tuner unit 450 using the reference frequency signal input from the transmission system reference frequency generation unit 401. The internal clock generation circuit 102 supplies the generated various clocks to the RF circuit 104 and other circuits.

  The terminal control unit 402 controls the entire wireless communication terminal device 400. Also, the terminal control unit 402 issues various processing execution commands at a predetermined timing. For example, the terminal control unit 402 performs channel tuning, initialization of each block of the digital TV tuner unit 450, stop processing of each block of the digital TV tuner unit 450, start of handover, and various types of processing of handover stop. Issue an instruction. Here, the handover process is a process when the radio communication terminal apparatus 400 receives an instruction to perform handover from the base station, and cell search for neighboring cells before receiving an instruction to perform handover from the base station is performed. Means processing not included.

  The control circuit 111 controls each block of the digital TV tuner unit 450. For example, the control circuit 111 receives an instruction to execute channel selection from the terminal control unit 402, initialization of each block of the digital TV tuner unit 450, or stop processing of each block of the digital TV tuner unit 450, and the RF circuit 104. The Lo frequency is set, each block is initialized, or each block is stopped.

  The specific process execution notifying unit 403 extracts, from the terminal control unit 402, the timing for issuing a handover start process or end process execution command as a timing for issuing a specific internal process execution command that causes a rapid reference frequency fluctuation. To do. Then, the specific process execution notifying unit 403 notifies the TV tuner AFC loop constant control unit 113 of the timing for issuing the execution instruction for the extracted handover start process or end process.

  When receiving the notification from the specific process execution notification unit 403, the TV tuner AFC loop constant control unit 113 instructs the variable loop filter 115 to select a smaller time constant than when the notification is not received. Specifically, the TV tuner AFC loop constant control unit 113 receives the notification from the specific process execution notification unit 403, and the gain of the variable loop filter 115 or the smoothing parameter (filter At least one of the band, the moving average number, the forgetting factor, etc.) is instructed to switch to a setting with high follow-up in automatic frequency control. For example, the TV tuner AFC loop constant control unit 113 increases the gain of the variable loop filter 115 or widens the band of the variable loop filter 115 during the handover start process or end process, and after a predetermined time has elapsed. Instruct to return to the original setting. Note that the setting change need not necessarily be in two stages, and may be in three or more stages.

  The configuration of the variable loop filter 115 is the same as that shown in FIG.

  Moreover, the position where the transmission system reference frequency generation unit 401 in the wireless communication terminal device 400 is mounted can be greatly reduced in performance deterioration due to sudden frequency fluctuations by being mounted at a position where the temperature fluctuation is small.

  Incidentally, in order to reduce the size and cost, it is effective to share the reference oscillation circuit with other functional blocks. In that case, in addition to the influence of the heat source near the reference oscillator on the frequency of the reference oscillator, there are the following problems.

  When a mobile phone uses a reference clock used for cellular transmission as the frequency of a reference oscillator of a digital television tuner, the reference frequency changes instantaneously due to synchronization processing with the base station at the time of handover. This frequency variation causes BER degradation.

  The transmission system reference frequency generation unit 401 generally uses a highly accurate and highly stable TCXO (Temperature Compensated Xtal Oscillator), but the frequency changes due to the synchronization processing with the base station at the time of the handover (between base stations). Max 0.04 ppm). Some wireless communication terminal devices 400 perform processing for changing the frequency in several stages, but in this case, since the change is instantaneous, the gradient of the frequency change is large, and the influence on the BER due to the change of the frequency. Becomes larger.

  Therefore, in the third embodiment, at the start of the handover process, the setting is switched to a setting that enhances the followability in the automatic frequency control, and at the end of the handover process, the automatic frequency control setting is restored. Thereby, the setting with high follow-up can be continued during the handover process. Note that the automatic frequency control setting is not returned to the original setting at the end of the handover process, but may be returned after a certain time from the start of the handover process.

  As described above, according to the third embodiment, by performing automatic frequency control with high followability during handover start processing or end processing, it is possible to reduce reception performance degradation due to sudden frequency fluctuations and It is possible to achieve both high reception performance maintenance in the state.

(Embodiment 4)
FIG. 5 is a block diagram showing a configuration of radio communication terminal apparatus 500 according to Embodiment 4 of the present invention.

  A wireless communication terminal device 500 shown in FIG. 5 is different from the wireless communication terminal device 100 according to Embodiment 1 shown in FIG. 1 except for the TV tuner reference frequency generation unit 101, with a GPS reception unit 501 and a GPS reference frequency generation unit. 502 and a buffer 503 are added, a terminal control unit 504 is provided instead of the terminal control unit 110, and a specific process execution notification unit 505 is provided instead of the specific process execution notification unit 112. 5, parts having the same configuration as in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The wireless communication terminal device 500 includes a digital TV tuner unit 550. The digital TV tuner unit 550 includes an internal clock generation circuit 102, an RF circuit 104, an A / D unit 105, an orthogonal detection unit 106, an LPF 107, and an OFDM demodulation circuit 108. , A decoding circuit 109, a control circuit 111, a frequency error detection unit 114, a variable loop filter 115, and an NCO 116.

  The GPS receiver 501 generates position information of the wireless communication terminal device 500 by reproducing GPS information from a GPS signal received by a GPS antenna (not shown) in synchronization with the reference frequency signal input from the GPS reference frequency generator 502. .

  The GPS reference frequency generation unit 502 generates a reference frequency signal for receiving a GPS signal, and outputs the generated reference frequency signal to the GPS reception unit 501 and the buffer 503.

  The buffer 503 is provided for driving two circuits of the internal clock generation circuit 102 and the GPS receiving unit 501, and reinforces deficiency in drive capability.

  The internal clock generation circuit 102 generates various clocks used in the digital television tuner unit 550 using the reference frequency signal input from the GPS reference frequency generation unit 502 via the buffer 503. The internal clock generation circuit 102 supplies the generated various clocks to the RF circuit 104 and other circuits.

  The terminal control unit 504 controls the entire wireless communication terminal device 500. Also, the terminal control unit 504 issues various processing execution instructions at a predetermined timing. For example, the terminal control unit 504 performs channel selection, initialization of each block of the digital TV tuner unit 550, stop processing of each block of the digital TV tuner unit 550, and various processes of starting or stopping the GPS reception unit 501. Issue an execution instruction.

  The control circuit 111 controls each block of the digital television tuner unit 550. For example, the control circuit 111 receives an instruction to execute channel selection from the terminal control unit 504, initialization of each block of the digital TV tuner unit 550, or stop processing of each block of the digital TV tuner unit 550, and the RF circuit 104. The Lo frequency is set, each block is initialized, or each block is stopped.

  The specific process execution notifying unit 505 determines the timing at which the execution command for starting or stopping the GPS receiving unit 501 is issued as the timing for issuing an execution command for specific internal processing that causes a sudden change in the reference frequency. Extract from Then, the specific process execution notifying unit 505 notifies the TV tuner AFC loop constant control unit 113 of the timing for issuing the execution instruction for the extracted start process or stop process of the GPS receiving unit 501.

  When receiving the notification from the specific process execution notification unit 505, the TV tuner AFC loop constant control unit 113 instructs the variable loop filter 115 to select a smaller time constant than when not receiving the notification. More specifically, the TV tuner AFC loop constant control unit 113 receives the notification from the specific process execution notification unit 505, rather than receiving the notification, the gain of the variable loop filter 115 or the smoothing parameter (filter At least one of the band, the moving average number, the forgetting factor, etc.) is instructed to switch to a setting with high follow-up in automatic frequency control. For example, the TV tuner AFC loop constant control unit 113 increases the gain of the variable loop filter 115 or widens the band of the variable loop filter 115 during the start-up process or the stop process of the GPS reception unit 501 for a predetermined time. Instruct to return to the original setting after the elapse. Note that the setting change need not necessarily be in two stages, and may be in three or more stages.

  By mounting the GPS reference frequency generation unit 502 in the wireless communication terminal device 500 at a position where the temperature fluctuation is small, it is possible to greatly reduce the performance deterioration due to the rapid frequency fluctuation.

  Incidentally, it is also effective to share the reference oscillation circuit with other functional blocks in order to reduce the size and cost. In that case, in addition to the influence of the heat source near the reference oscillator on the frequency of the reference oscillator, there are the following problems.

  Even if the reference frequency of the GPS receiving circuit or the like does not change, the circuit block is started and stopped, so that fluctuations in the load on the oscillation circuit and fluctuations in the power supply voltage occur, which causes the oscillation frequency to change and the BER to deteriorate. .

  When the GPS signal is not received, the power supply of the GPS receiving unit 501 is turned off, so that the load impedance of the GPS reference frequency generating unit 502 changes and the power supply voltage changes, and the reference frequency changes accordingly.

  Therefore, in the fourth embodiment, the automatic frequency is increased by increasing the gain of the variable loop filter 115 or widening the band of the variable loop filter 115 in accordance with the timing of the start processing or stop processing of the GPS receiving unit 501. Control is performed so that the follow-up of control is high. Then, wireless communication terminal apparatus 500 returns to the setting with high noise resistance by reducing the gain of variable loop filter 115 or reducing the band of variable loop filter 115 after a predetermined time has elapsed.

  As described above, according to the fourth embodiment, when the reference frequency supplied to the GPS receiver that is activated as necessary is used as the reference frequency of the digital television tuner, the activation process or the stop process of the GPS receiver is involved. When the reference frequency changes due to changes in the load impedance of the GPS reference frequency generator or power supply voltage, automatic frequency control with high tracking performance reduces the deterioration in reception performance due to sudden frequency fluctuations and normal conditions This makes it possible to achieve both high reception performance and maintenance.

  In the fourth embodiment, the gain or smoothing parameter of the automatic frequency control variable loop filter 115 having high followability is set during the start-up process or stop process of the GPS receiving unit 501. However, the present invention is not limited to this. The gain or smoothing parameter of the automatic frequency control variable loop filter 115 with high followability may be set during the operation start process or the operation stop process of the function sharing the reference frequency other than the GPS receiver 501.

(Embodiment 5)
FIG. 6 is a block diagram showing a configuration of radio communication terminal apparatus 600 according to Embodiment 5 of the present invention.

  Radio communication terminal apparatus 600 shown in FIG. 6 adds temperature detection section 601 and temperature change amount detection section 602 to radio communication terminal apparatus 100 according to Embodiment 1 shown in FIG. In FIG. 6, parts having the same configuration as in FIG.

  The wireless communication terminal apparatus 600 includes a digital TV tuner unit 650. The digital TV tuner unit 650 includes an internal clock generation circuit 102, an RF circuit 104, an A / D unit 105, an orthogonal detection unit 106, an LPF 107, and an OFDM demodulation circuit 108. , A decoding circuit 109, a control circuit 111, a frequency error detection unit 114, a variable loop filter 115, and an NCO 116.

  The temperature detection unit 601 is, for example, a thermistor, detects the temperature in the vicinity of the TV tuner reference frequency generation unit 101, and outputs the detection result to the temperature change amount detection unit 602.

  Based on the temperature detection result input from the temperature detection unit 601, the temperature change amount detection unit 602 detects the temperature change amount in unit time, that is, the gradient of the temperature change. Then, the temperature change amount detection unit 602 outputs the detection result to the TV tuner AFC loop constant control unit 113.

  The TV tuner AFC loop constant control unit 113 instructs the variable loop filter 115 to select a smaller time constant than when the notification is not received from the specific process execution notification unit 112 as compared with the case where the notification is not received. Specifically, the TV tuner AFC loop constant control unit 113 receives the notification from the specific process execution notification unit 112, and does not receive the notification, the gain of the variable loop filter 115 or the smoothing parameter (filter At least one of the band, the moving average number, the forgetting factor, etc.) is instructed to switch to a setting with high follow-up in automatic frequency control. For example, the TV tuner AFC loop constant control unit 113 increases the gain of the variable loop filter 115 when starting the transmission system transmission amplifier, stopping the transmission system transmission amplifier, starting the operation of the charging circuit, or stopping the operation of the charging circuit. Alternatively, the bandwidth of the variable loop filter 115 is widened, and an instruction is given to restore the original setting after a predetermined time has elapsed. Note that the setting change need not necessarily be in two stages, and may be in three or more stages.

  Further, the TV tuner AFC loop constant control unit 113 switches the setting of automatic frequency control when the gradient of the temperature change in the detection result input from the temperature change amount detection unit 602 exceeds a predetermined threshold. For example, the TV tuner AFC loop constant control unit 113 switches the setting of at least one of the gain of the variable loop filter 115 and the smoothing parameter (filter band, moving average number, forgetting factor, etc.).

  Next, the operation of radio communication terminal apparatus 600 will be described using FIG. FIG. 7 is a diagram showing the relationship between temperature and the gradient of temperature change and time.

  The temperature detection unit 601 detects the temperature # 700, and the temperature change amount detection unit 602 calculates the temperature change slope # 701 from the detected temperature # 700 or the detected voltage corresponding to the detected temperature # 700. The temperature change amount detection unit 602 notifies the TV tuner AFC loop constant control unit 113 when the calculated temperature change gradient # 701 exceeds a predetermined switching threshold # 702. Since the temperature change amount detection unit 602 needs to detect a negative temperature change, the absolute value of the calculated temperature change gradient # 701 is obtained and the absolute value of the calculated temperature change gradient # 701 and the threshold value are obtained. Compare. FIG. 7 shows the case of a positive temperature change.

  The TV tuner AFC loop constant control unit 113 switches the automatic frequency control setting from the normal setting # 704 to the high follow-up setting # 705 in response to the notification from the temperature change amount detection unit 602, and the normal setting # when the notification disappears # Return to 704. As shown in FIG. 7, the setting is returned to the normal setting # 704 after a predetermined time T10 has elapsed from the time t1 when the notification is lost.

  When receiving a notification from the specific process execution notification unit 112, the TV tuner AFC loop constant control unit 113 performs the same setting as in the first to fourth embodiments. Also, the TV tuner AFC loop constant control unit 113 prioritizes the high follow-up setting when receiving a plurality of notifications from the specific process execution notification unit 112 and a notification from the temperature change amount detection unit 602. For example, the TV tuner AFC loop constant control unit 113 immediately after setting the high tracking capability in the automatic frequency control by the transmission processing power amplifier stop process notification from the specific process execution notification unit 112, immediately after the temperature change amount detection unit 602. If a notification is received from the temperature change amount detection unit 602, a setting with high follow-up is continued even if a predetermined time after the transmission system power amplifier stops is received.

  By mounting the TV tuner reference frequency generation unit 101 in the wireless communication terminal device 600 at a position where the temperature variation is small, it is possible to greatly reduce performance degradation due to a rapid frequency variation.

  As described above, according to the fifth embodiment, when the amount of temperature change exceeds the threshold value, automatic frequency control with high follow-up performance is performed, thereby reducing the deterioration in reception performance due to sudden frequency fluctuations and the normal state. This makes it possible to achieve both high reception performance and maintenance.

  In the first to fifth embodiments, a digital automatic frequency control circuit that generates a local signal used in digital quadrature detection by an NCO and a Lo-IF receiver using the digital automatic frequency control circuit are provided. However, the present invention is not limited to this, and each embodiment can be applied to a direct conversion receiver using analog VCO (voltage controlled oscillators). In this case, the RF circuit outputs an analog baseband signal (I signal and Q signal) by performing quadrature detection of the received signal with an analog local signal.

  The radio communication terminal apparatus and automatic frequency control method according to the present invention are suitable for receiving, for example, digital television broadcasts.

1 is a block diagram showing a configuration of a wireless communication terminal apparatus according to Embodiment 1 of the present invention. 1 is a block diagram showing a configuration of a variable loop filter according to a first embodiment of the present invention. FIG. 3 is a block diagram showing a configuration of a wireless communication terminal apparatus according to Embodiment 2 of the present invention. Block diagram showing a configuration of a wireless communication terminal apparatus according to Embodiment 3 of the present invention FIG. 7 is a block diagram showing a configuration of a wireless communication terminal apparatus according to Embodiment 4 of the present invention. FIG. 9 is a block diagram showing a configuration of a wireless communication terminal apparatus according to Embodiment 5 of the present invention. The figure which shows the relationship between the temperature which concerns on Embodiment 5 of this invention, the inclination of a temperature change, and time.

Explanation of symbols

100, 300, 400, 500, 600 Wireless communication terminal device 101 TV tuner reference frequency generation unit 102 Internal clock generation circuit 103, 301, 302 Antenna 104, 303, 304 RF circuit 105, 305, 306 A / D unit 106, 307 , 308 Quadrature detector 107, 309, 310 LPF
108, 311, 312 OFDM demodulation circuit 109 decoding circuit 110, 315 terminal control unit 111, 316 control circuit 112, 317 specific processing execution notification unit 113 TV tuner AFC loop constant control unit 114 frequency error detection unit 115 variable loop filter 116 NCO
150, 350 Digital TV tuner

Claims (8)

Reference frequency generating means for generating a reference frequency signal for receiving and processing a television broadcast signal;
A frequency error detecting means for detecting a frequency error in the reception signal of the television broadcast and outputting a frequency error signal indicating the detected frequency error;
Specific process execution notifying means for notifying the reference frequency signal generated by the reference frequency generating means of timing for issuing a specific internal process execution command that causes frequency fluctuations during reception of the television broadcast ;
Control means for setting a small time constant when receiving the notification as compared to when not receiving the notification;
A loop filter that passes the frequency error signal with a time constant set by the control means and integrates the frequency error signal;
Local signal generating means for generating a local signal of a predetermined oscillation frequency from the frequency error signal integrated by the loop filter;
Orthogonal detection means for compensating the frequency error in the reception signal by performing orthogonal detection of the reception signal with the generated local signal;
A wireless communication terminal apparatus comprising:   2. The radio communication terminal apparatus according to claim 1, wherein the specific process execution notifying unit notifies a timing at which an execution instruction of a start process or a stop process of an amplifier for transmitting a signal of a cellular communication system which is the specific internal process is issued. .   3. The wireless communication terminal device according to claim 1, wherein the specific process execution notifying unit notifies a timing at which an execution instruction for an operation start process or an operation stop process of the charging circuit which is the specific internal process is issued. Receiving means for receiving the received signal with a plurality of antennas or a single antenna;
Based on the comparison result between the detection value indicating the reception quality of the reception signal received by the reception means and a threshold value, the reception signal is received by the plurality of antennas and the reception signal is received by the single antenna. Receiving switching means for performing a switching process for switching between receiving and receiving,
The wireless communication terminal apparatus according to claim 1, wherein the specific process execution notifying unit notifies a timing at which an instruction to execute the switching process, which is the specific internal process, is issued. Comprising a reference frequency generation means for generating a reference frequency signal for data transmission of a cellular communication system as a reference frequency signal in the reception processing of the received signal;
5. The specific process execution notifying unit notifies a timing at which an execution instruction for a handover start process or an end process in the cellular communication system as the specific internal process is issued. Wireless communication terminal device. GPS receiving means for receiving GPS signals and acquiring position information;
A reference frequency generating means for generating a reference frequency signal of the GPS receiving means as a reference frequency signal in the reception processing of the received signal;
The radio according to any one of claims 1 to 4 , wherein the specific process execution notifying unit notifies a timing at which an execution instruction for starting or stopping the GPS receiving unit, which is the specific internal process, is issued. Communication terminal device. Reference frequency generation means for generating a reference frequency signal for receiving and processing the reception signal of the television tuner;
Temperature detecting means for detecting a temperature in the vicinity of the reference frequency generating means;
A temperature change amount detecting means for detecting a change amount of the detected temperature per unit time; and
Said loop filter, one of claims 1 to 4, to reduce the time constant to pass said frequency error signal as compared with the case where the amount of change when the change amount is equal to or larger than the threshold is less than the threshold value The wireless communication terminal device according to 1. Generating a reference frequency signal for receiving and processing a television broadcast signal;
Detecting a frequency error in the reception signal of the television broadcast and outputting a frequency error signal indicating the detected frequency error;
Notifying a timing of issuing an execution instruction of a specific internal process that causes a frequency variation during reception of the television broadcast with respect to the reference frequency signal ;
When receiving the notification, setting a small time constant in the loop filter compared to the case where the notification is not received;
The loop filter passes the frequency error signal and integrates the frequency error signal during the passage;
Generating a local signal having a predetermined oscillation frequency from the integrated frequency error signal;
Compensating the frequency error in the received signal by orthogonally detecting the received signal with the generated local signal;
An automatic frequency control method comprising:

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