JP2005236694A - Passband adjusting device and radio terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize passband characteristics of an active filter. <P>SOLUTION: A modulation wave signal used in a communication system equipped with an active filter 1 is fed from a modulation wave signal generator 2 to the active filter 1, and an EVM value (EVM:Error Vector Magnitude) of the output from the active filter 1 is measured by an EVM measuring instrument 3. A control unit 4 forms an adjustment signal for minimizing the EVM value so that the passband characteristic of the active filter 1 is adjusted under control by the adjustment signal. Since the modulation wave signal used in the communication system equipped with the active filter 1 is used and the passband characteristic of the active filter 1 is adjusted so as to minimize the EVM value, the active filter 1 can be adjusted to the optimum passband characteristic adapted to the system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a portable terminal device such as a mobile phone, a PHS phone (Personal Handyphone System), a PDA device (Personal Digital Assistant) having a wireless communication function, and a notebook personal computer device having a wireless communication function. The present invention relates to a wireless terminal device and a measurement device that are suitable for application to a terminal device such as a stationary personal computer device having a communication function, and in particular, uses a modulated wave signal to set the passband characteristics of a reception system filter to an optimum adjustment value. The present invention relates to a passband adjustment device and a wireless terminal device that can be adjusted.

  In a wireless terminal device such as a mobile communication device today, a channel selection filter that allows a signal in a predetermined frequency band to pass is provided in an intermediate frequency unit (IF unit) of a reception system.

  As the channel selection filter, for example, a transconductance variable filter (gmC filter) is used as an active filter capable of adjusting or changing the passband characteristic (center frequency).

  The gmC filter sets an arbitrary passband characteristic by appropriately setting the voltage value of the filter adjustment voltage applied to the gmC filter. In addition, the gmC filter can be provided in a transmission / reception system IC, and through this, it is possible to reduce the size and cost of the wireless terminal device, so that it is widely used today. .

  Here, the active filter represented by this gmC filter has variations in the center frequency of the passband for each active filter. In particular, in the case of a filter configuration that is reduced in size and cost, the variation in the center frequency is large.

  Conventionally, a filter adjustment method and a filter adjustment apparatus are disclosed in Japanese Patent Application Laid-Open No. 2001-119268 (Patent Document 1) for the purpose of accurately adjusting the passband characteristics of an active filter with a small number of adjustment procedures. JP-A-2002-76841 discloses a filter center frequency adjusting device and method in Japanese Patent Laid-Open No. 2002-76841.

  In the prior art disclosed in the above-mentioned Patent Document 1, an unmodulated carrier (CW) is divided into three steps of coarse adjustment, fine adjustment, and finest adjustment using one wave, and RSSI measurement values (RSSI: Received Signal Strength Indicators). By detecting the filter adjustment voltage that minimizes (), the passband characteristics of the active filter can be adjusted with high accuracy and with a small adjustment procedure.

  On the other hand, in the prior art disclosed in Patent Document 2, two frequency components having the same frequency from the center frequency shifted in the + direction and the − direction with respect to the intermediate frequency filter (IF filter). While supplying a tone signal (two-wave unmodulated carrier), the current value supplied to the IF filter is changed so that the previously set center frequency is shifted in the-direction by delta F with respect to the IF filter. The RSSI measurement value (Va) in this state is measured.

  Next, the current value supplied to the IF filter is changed so that the previously set center frequency is shifted in the + direction by 2 × delta F in the state where the two unmodulated carriers are supplied to the IF filter. To measure the RSSI measurement value (Vb).

  Then, the RSSI measurement value (Va) and the RSSI measurement value (Vb) are compared, and the current value supplied to the IF filter is changed so that the smaller RSSI measurement value can be obtained. Change and set the center frequency of the filter. As a result, correction of the center frequency of the IF filter that varies with temperature and power supply voltage is realized with a small circuit configuration.

JP 2001-119268 A (pages 4-7: FIG. 8) JP 2002-76841 A (page 3: FIG. 1)

  Here, in each of the prior arts disclosed in Patent Document 1 and Patent Document 2, the center frequency of the IF filter is adjusted using an unmodulated wave.

  However, in a wireless terminal device such as a cellular phone, actually, modulation processing is performed by a predetermined modulation method such as a QPSK modulation method (QPSK: Quadrature Phase Shift Keying) or a GMSK modulation method (GMSK: Gaussian filtered Minimum Shift Keying). The received signal will be received. For this reason, when the center frequency of the IF filter is adjusted using a non-modulated wave as in each of the prior arts, the IF band is adjusted so that the optimum passband characteristic is obtained when the modulated wave is actually received. It is difficult to adjust the passband characteristics of the filter.

  In addition to extracting the channel, the IF filter is required to satisfy the root Nyquist characteristic. In order to satisfy the root Nyquist characteristic, an intermediate value is used so that the RSSI value is minimized by using an unmodulated wave. Rather than setting the frequency, the EVM value (EVM: Error Vector Magnitude = a value indicating the degree of distortion of the output with respect to the input signal) is adjusted to be minimized by using the modulated wave as in the actual communication system. Is preferred.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a passband adjustment device and a wireless terminal device that can adjust the passband characteristic of a filter to an optimum passband characteristic using a modulated wave. .

  In the present invention, a modulated wave signal is input to a filter unit that requires adjustment of the passband characteristics, and an EVM value (EVM: Error Vector Magnitude) of the output of the filter unit is set to a minimum value. Adjust the passband characteristics.

  The present invention can adjust the passband characteristic of the filter means so as to correspond to the actually received modulated wave signal. For this reason, it is possible to adjust the pass band characteristic of the filter means so as to obtain the optimum pass band characteristic for the actually received signal.

[First Embodiment]
[Configuration of passband adjustment device]
First, FIG. 1 is a block diagram of a passband adjusting apparatus according to a first embodiment to which the present invention is applied. The passband adjusting device includes a modulated wave signal generator 2 that supplies a modulated wave signal in a predetermined frequency band to an active filter 1 that can change passband characteristics according to a supplied voltage (or current). An EVM measuring device 3 such as a modulation analyzer that measures an EVM value (EVM: Error Vector Magnitude) output from the active filter 1 and a voltage value adjustment signal corresponding to the EVM value measured by the EVM measuring device 3 are active. By supplying to the filter 1, it has the control part 4 which controls the pass-band characteristic of this active filter 1.

  For example, the modulated wave signal generator 2 generates a modulated wave signal in an intermediate frequency band such as 450 kHz. Further, it is assumed that this modulated wave signal has been subjected to modulation processing by a QPSK modulation method (QPSK: Quadrature Phase Shift Keying). Further, the active filter 1 is provided with a root Nyquist filter that extracts, for example, a ± 10.5 kHz band from the modulated wave signal with 450 kHz as the center frequency.

[Operation of passband adjustment device]
In such a passband adjusting device, the modulation wave signal generator 2 generates a modulation wave signal of an intermediate frequency band of 450 kHz and supplies this to the active filter 1. The active filter 1 extracts a ± 10.5 kHz band having a frequency corresponding to an adjustment signal from the control unit 4 to be described later as a center frequency from this modulated wave signal, and supplies this to the EVM measuring device 3.

  The EVM measuring device 3 measures the EVM value of the output from the active filter 1 and supplies this measurement output (EVM output) to the control unit 4.

  As an example, the EVM measuring instrument 3 has the configuration shown in FIG. 2, and the output from the active filter 1 is supplied to the demodulator 11 and the detector 12. The demodulator 11 performs a demodulation process (in this example, a QPSK demodulation process) corresponding to the modulation process performed on the output from the active filter 1 and supplies the demodulated signal to the level adjuster 13. To do.

  Here, the comparing unit 14 compares the demodulated signal with the reference signal from the reference signal generating unit 15, and detects the distortion amount (EVM value) the demodulated signal has with respect to the reference signal. Yes. When this comparison process is performed, it is necessary to match the signal level of the demodulated signal with the signal level of the reference signal.

  Therefore, the detection unit 12 and the automatic gain control unit 16 (AGC) detect the level of the output from the active filter 1 and supply this level detection output to the level adjustment unit 13. The level adjusting unit 13 amplifies the demodulated signal from the demodulating unit 11 with a gain corresponding to the level detection output from the AGC 16, thereby matching the signal level of the demodulated signal with the signal level of the reference signal.

  The output timing of the reference signal from the reference signal generation unit 15 and the demodulated signal from the level adjustment unit 13 is adjusted by the synchronization adjustment unit 17 and supplied to the comparison unit 14. The comparison unit 14 compares the demodulated signal and the reference signal whose level adjustment and output timing are adjusted as described above, thereby detecting the distortion amount of the demodulated signal with respect to the reference signal, and using this as the EVM output. 1 is supplied to the control unit 4 shown in FIG. The control unit 4 changes the value of the adjustment signal supplied to the active filter 1 so that the value of the EVM output becomes the minimum value.

  Specifically, the relationship between the EVM value measured by the EVM measuring instrument and the value of the adjustment signal supplied from the control unit 4 to the active filter 1 is as shown in FIG. From FIG. 3, it can be seen that the EVM value of the output from the active filter 1 shows the minimum value by supplying the adjustment signal having a predetermined value to the active filter 1. That is, in the example of FIG. 3, by supplying an adjustment signal having a voltage value of 1.6 V to the active filter 1 to the active filter 1, the EVM value of the output from the active filter 1 is about 9 [% rms It can be seen that the minimum value is indicated.

  FIG. 4 shows the passband characteristics of the active filter 1, and the dotted line graph shows the passband characteristics when an adjustment signal having a voltage value of 1.2 V is supplied to the active filter 1 as a solid line. The graph shows the passband characteristics when an adjustment signal having a voltage value of 1.6 V is supplied to the active filter 1, and the one-dot chain line shows the adjustment signal having a voltage value of 2.0 V to the active filter 1. The passband characteristics when supplied are shown.

  As can be seen from FIG. 3, when the 1.6 V adjustment signal is supplied to the active filter 2, the EVM value becomes the minimum value. Therefore, the control unit 4 sets the value of the adjustment signal supplied to the active filter 1 based on the EVM value measured by the EVM measuring device so that the EVM value of the output from the active filter 1 is minimized. Control. Thereby, as shown in each graph of FIG. 4, the center frequency of the passband characteristic of the active filter 1 is gradually adjusted to 450 kHz and adjusted.

[Effect of the first embodiment]
As is clear from the above description, the passband adjustment apparatus of the first embodiment inputs a “modulated wave” to the active filter 1, and the control unit 4 outputs the EVM of the output of the active filter 1. The value of the adjustment signal supplied to the active filter 1 is controlled so that the value becomes the minimum value.

  As a result, the passband characteristic of the active filter can be adjusted using the actually received modulated wave, so that the passband characteristic of the active filter is optimized so as to obtain the optimum passband characteristic for the actually received signal. Characteristics can be adjusted.

  For this reason, by optimizing the passband characteristics, it is possible to improve reception sensitivity and call voice quality, and it is possible to improve the selectivity of adjacent channels.

  In data communication, the error rate can be lowered, and as a result, the communication speed can be improved.

  Further, adverse effects due to temperature drift can be reduced, and as a result, the operable temperature range can be expanded.

In the above description of the first embodiment, it has been described that the passband characteristic of the active filter 1 is adjusted. It is added that any filter that needs to be adjusted can adjust its passband characteristics.

[Modification of First Embodiment]
Next, the active filter 1 is normally formed as one integrated circuit (IC) on one chip as shown in FIG. For this reason, a part or all of the pass band adjusting device can be integrated into one chip by incorporating a part or all of the circuit unit of the pass band adjusting device into the filter IC.

  Specifically, FIG. 6 is an example in which the control unit 4 is incorporated in the filter IC of the active filter 1. FIG. 7 shows an example in which the modulated wave signal generator 2, the EVM measuring device 3, and the control unit 4 are incorporated in the filter IC of the active filter 1.

In this way, by making a part or all of the passband adjustment device into one chip, the passband adjustment device can be easily incorporated into a communication terminal device such as a mobile phone as described in the following embodiments. Can do.

[Second Embodiment]
Next, a mobile phone according to a second embodiment to which the present invention is applied will be described. The mobile phone according to the second embodiment is configured such that the modulation signal generator 2 and the EVM provided with the center frequency of the active filter 1 provided in the mobile phone are externally attached to the mobile phone. This is set by the measuring device 3 and the control unit 4.

[Configuration of Second Embodiment]
Specifically, the mobile phone according to the second embodiment receives the output of the active filter 1 via the EVM interface 22 (EVMIF) provided in the filter IC of the active filter 1 as shown in FIG. The adjustment signal from the control unit 4 is supplied to the active filter 1 via the control interface 23 (control IF) provided in the filter IC, and the center frequency is controlled. It is like that. The modulated wave signal from the modulated wave generator 2 is supplied to an antenna switch connected to the antenna of the mobile phone, and the modulated wave signal supplied via the antenna switch is received. The signal is supplied to the active filter 1 through the system and the intermediate frequency signal processing unit.

[Operation of Second Embodiment]
FIG. 9 shows a detailed circuit diagram of the transmission / reception system of the cellular phone according to the second embodiment. As can be seen from FIG. 9, the mobile phone is compatible with an 800 MHz and 1.5 GHz system, and an 800 MHz or 1.5 GHz modulated wave signal from the modulated wave signal generator 2 is received at a reception input terminal. 31 (EXT_RX) or a transmission output terminal 32 (EXT_TRX) to be supplied to the antenna switch 30 (ANT_SW).

  The antenna switch 30 switches the internal switch to supply the modulated wave signal supplied via the reception input terminal 31 or the transmission output terminal 32 to the RF processing unit 34. The RF processing unit 34 uses the SAW filter 33, the mixer 34 (including a low noise amplifier (LNA)) supplied with the synthesizer output from the synthesizer unit 36, and the MC filter 35 to convert the modulated wave signal from the SAW filter 33 to an intermediate frequency. The signal (IF) is converted and supplied to the filter IC 40.

  The intermediate frequency signal supplied to the filter IC 40 is amplified with a predetermined gain based on the synthesizer output from the synthesizer unit 36 and supplied to the active filter 1. As described above, the active filter 1 extracts a predetermined band from the intermediate frequency signal, supplies it to a demodulator (not shown) at the subsequent stage, and passes through the EVMIF 22 provided in the filter IC 40 as shown in FIG. To the EVM measuring instrument 3 shown in FIG.

  The EVM measuring device 3 detects the EVM value based on the output from the active filter 1 and supplies it to the control unit 4. The control unit 4 forms an adjustment signal that makes this EVM value the minimum value, and supplies this to the active filter 1 via the control IF 23 shown in FIG. Thus, similarly to the above, the passband characteristics of the active filter 1 provided in the mobile phone are converted into the modulated wave signal generator 2 and the EVM measuring device 3 provided externally to the mobile phone. Further, the control unit 4 can adjust to the optimum characteristics.

[Effects of Second Embodiment]
As apparent from the above description, the cellular phone according to the second embodiment supplies the output of the active filter 1 to the filter IC 40 to the EVM measuring device 3 externally attached to the cellular phone. EVMIF 22 and a control IF 23 for supplying an adjustment signal from the control unit 4 externally attached to the mobile phone to the active filter 1 are provided. Then, the EVM value output from the active filter 1 is measured by the externally attached EVM measuring device 3, and the control unit 4 forms an adjustment signal that minimizes the EVM value. The center frequency of the active filter 1 in the telephone is adjusted.

  Thereby, based on the modulated wave signal supplied via the antenna switch 30, the center frequency of the active filter 1 can be adjusted so that the EVM value of the output of the active filter 1 is minimized. For this reason, the passband characteristic of the active filter 1 of the mobile phone can be adjusted to an optimum characteristic corresponding to the actually received modulated wave signal.

In the case of the mobile phone according to the second embodiment, the modulated wave signal from the modulated wave signal generator 2 is sent to the active filter 1 via the antenna switch 30, the SAW filter 33, the mixer 34, and the MC filter 35. It comes to supply. For this reason, the pass band characteristic of the active filter 1 can be adjusted in a manner including the characteristics of the system preceding the active filter 1, that is, the antenna switch 30, the SAW filter 33, the mixer 34, and the MC filter 35. Therefore, it is possible to adjust the pass band characteristic of the active filter 1 so as to obtain an optimum characteristic for the receiving system of the mobile phone.

[Modification of Second Embodiment]
In the description of the second embodiment described above, the modulation wave signal generator 2, the EVM measuring device 3, and the control unit 4 are provided externally to the mobile phone. As shown, the control unit 4 may be provided in the filter IC 40 of the mobile phone (or the CPU in the mobile phone may function as the control unit 4).

In this case, the modulated wave signal from the modulated wave signal generator 2 is supplied from the antenna switch 30 and supplied to the active filter 1 in the mobile phone. The output of the active filter 1 is supplied to the EVM measuring instrument 3 externally attached to the mobile phone via the EVMIF 22 provided in the filter IC 40. Further, the EVM value from the EVM measuring device 3 is supplied to the control unit 4 provided in the filter IC 40 in the mobile phone via the EVMIF 22. Then, the control unit 4 adjusts the passband characteristic of the active filter 1 with the adjustment signal formed based on the EVM value, and the same effect as described above can be obtained.

[Third Embodiment]
Next, a mobile phone according to a third embodiment to which the present invention is applied will be described. As shown in FIG. 7, the cellular phone according to the third embodiment includes a filter IC 50 in which the active filter 1, the modulated wave signal generator 2, the EVM measuring device 3, and the control unit 4 are integrated into one chip. It is provided inside.

  In the case of the mobile phone of the second embodiment described above, the modulated wave signal from the modulated wave signal generator 2 is supplied via the antenna switch 30, but the mobile phone of the third embodiment. In this case, since the modulation wave signal generator 2 is provided in the filter IC 50, the modulation wave signal is directly supplied from the modulation wave signal generator 2 to the active filter 1. Then, an EVM value of the output of the active filter 1 is measured by the EVM measuring device 3 provided in the filter IC 50, and an adjustment signal corresponding to the EVM value is formed by the control unit 4 provided in the filter IC 50. Thus, the passband characteristic of the active filter 1 is adjusted.

  Thereby, the pass band characteristic of the active filter 1 can be optimized similarly to the above-mentioned 2nd Embodiment.

  In the case of the mobile phone according to the third embodiment, the active filter 1, the modulation wave signal generator 2, the EVM measuring device 3, and the control unit 4 are integrated into one chip in the filter IC 50. It is possible to adjust the passband characteristic of the active filter 1 only by the above.

[Control of passband characteristics adjustment timing]
Here, the CPU in the mobile phone controls the timing for supplying the modulated wave signal from the modulated wave signal generator 2 to the active filter 1.
1. Timing when an instruction to adjust the center frequency is given from the user (the user may give this adjustment instruction when the reception state is not expected, for example),
2. When silence is detected,
3. The so-called “vacant time” from when packet data is received until the next packet data is received is detected, and the modulated wave signal from the modulated wave signal generator 2 is supplied to the active filter 1 during this idle time. Control.

Thereby, the pass band characteristic of the active filter 1 can always be maintained in an optimal state using the idle time.

  Finally, the present invention is not limited to the above-described embodiments disclosed as examples. For example, in the above description of the second and third embodiments, the present invention is applied to a mobile phone. However, this is applicable to any device that has a communication function. May be.

  In addition to the above-described embodiments, it is a matter of course that various modifications can be made according to the design and the like as long as they do not depart from the technical idea of the present invention. deep.

1 is a block diagram of a passband adjusting apparatus according to a first embodiment to which the present invention is applied. It is a block diagram of the EVM measuring device provided in the passband adjusting device. FIG. 6 is a characteristic diagram showing a relationship between an adjustment signal for adjusting a pass band of an active filter and an EVM value of an output of the active filter 1. It is a figure which shows a mode that the pass band of an active filter is optimized by the pass band adjustment apparatus. It is a block diagram for demonstrating the 1st modification of a pass-band adjustment apparatus. It is a block diagram for demonstrating the 2nd modification of a pass-band adjustment apparatus. It is a block diagram for demonstrating the 3rd modification of a pass-band adjustment apparatus. It is a block diagram of the mobile telephone which becomes 2nd Embodiment to which this invention is applied. It is a circuit diagram of the transmission / reception system of the mobile phone of the second embodiment. It is a block diagram for demonstrating the modification of the mobile telephone of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Active filter, 2 Modulation wave signal generator, 3 EVM measuring device, 4 Control part, 11 Demodulation part, 12 Detection part, 13 Level adjustment part, 14 Comparison part, 15 Reference signal generation part, 16 Automatic gain control part (AGC) Part), 17 synchronization adjustment part, 22 EVM interface (EVMIF), 23 control interface (control IF), 40 filter IC, 50 filter IC

Claims (5)

Modulated wave signal generating means for supplying a modulated wave signal used in a system in which the filter means is provided to filter means capable of changing the passband characteristics in response to an adjustment signal supplied from the outside;
EVM measuring means for measuring an EVM value (EVM: Error Vector Magnitude) of the output from the filter means;
And a control means for forming the adjustment signal that minimizes the EVM value measured by the EVM measurement means and supplying the adjustment signal to the filter means. An external input means for supplying a modulated wave signal used in the wireless terminal device supplied from the modulated wave signal generating means;
Frequency conversion means for converting the modulated wave signal supplied via the external input means into a predetermined intermediate frequency signal;
Filter means for varying a passband characteristic corresponding to the supplied adjustment signal, and extracting a predetermined band from the modulated signal subjected to frequency conversion processing by the frequency conversion means with the variable passband characteristic;
An EVM interface for supplying an output from the filter means to an EVM measuring means (EVM: Error Vector Magnitude) provided outside the wireless terminal device;
Control for supplying to the filter means the adjustment signal from the control means provided outside the wireless terminal device, which forms the adjustment signal that minimizes the EVM value measured by the EVM measurement means. And a wireless terminal device having an interface. The wireless terminal device according to claim 2,
The wireless terminal device, wherein the external input means is an antenna switch for switching a reception signal received by an antenna and a transmission signal transmitted from the wireless terminal device. Modulated wave signal generating means for generating a modulated wave signal used in the wireless terminal device;
Filter means for varying a passband characteristic corresponding to the supplied adjustment signal, and extracting a predetermined band from the modulated wave signal from the modulated wave signal generating means with the varied passband characteristic;
EVM measuring means for measuring an EVM value (EVM: Error Vector Magnitude) of the output from the filter means;
Control means for forming the adjustment signal that minimizes the EVM value measured by the EVM measurement means, supplying the adjustment signal to the filter means, and variably controlling the passband characteristics of the filter means. Wireless terminal device. The wireless terminal device according to claim 4,
The wireless terminal device, wherein the control means detects an idle time of communication and supplies the adjustment signal to the filter means during the idle time.

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