JP2013138308A - Signal generator and signal generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal generator and signal generation method capable of ensuring a dynamic range of an output signal level in a wide range without increasing the number of attenuator sections of a step attenuator.SOLUTION: A signal generator 10 comprises a level adjuster 20 for adjusting a power level of an output signal of an orthogonal modulator 14 to a predetermined power level, and outputting the adjusted signal to a step ATT 17. The level adjuster 20 comprises: a variable attenuator 21 for attenuating power of the output signal of the orthogonal modulator 14 according to a control signal; a detector input level setter 23 having a passing unit 23a which makes an input signal pass through as it is, and an attenuation unit 23b which attenuates the input signal by a predetermined attenuation amount; a detector 24 for detecting an output signal of the detector input level setter 23; and a comparator 27 for comparing a detection signal level with a reference level, and outputting a control signal for setting an attenuation amount to the variable attenuator 21 so that a reference point level becomes a predetermined value.

Description

  The present invention relates to a signal generation apparatus and a signal generation method for generating a test signal in a characteristic test for a mobile communication terminal such as a mobile phone or a mobile terminal.

  Conventionally, in a characteristic test of a mobile communication terminal or the like, a signal generator is used to supply a test signal to the mobile communication terminal or the like (see, for example, Patent Document 1).

  A signal generation device described in Patent Document 1 includes a baseband signal generation unit that generates an IQ baseband signal, quadrature modulation means that outputs a quadrature modulation signal obtained by modulating a local oscillation signal input from a local oscillator with an IQ baseband signal, and A step attenuator for attenuating the signal level of the quadrature modulation signal to a predetermined level and outputting it, so that a test signal having a radio frequency and a signal level designated by the tester can be output.

  In the above-described configuration, the step attenuator is configured such that a plurality of attenuator sections are selectively connected in series, and the attenuation amount can be varied in steps by a combination of attenuation amounts of the respective attenuator sections.

JP 2008-205812 A

  However, in the conventional signal generator, it is necessary to generate test signals in a wide range of frequencies from kilohertz to gigahertz, and the maximum attenuation of the step attenuator that can obtain sufficient performance in a wide range of frequencies is limited to about 120 dB. In order to make the dynamic range of the output signal level more variable, there is a problem that it is technically difficult to respond by increasing the number of attenuator sections of the step attenuator. Further, in the conventional signal generator, even if the number of attenuator sections can be increased, there is a problem that the number of parts of the step attenuator increases and the step attenuator increases in size.

  The present invention has been made in view of the above-described circumstances, and provides a signal generating apparatus and a signal generating method capable of ensuring a wide dynamic range of an output signal level without increasing the number of attenuator sections of a step attenuator. The purpose is to provide.

  A signal generator according to claim 1 of the present invention includes a modulated signal generating means (14) for modulating a baseband signal to generate a modulated signal, and a step attenuator (attenuating an input signal by a predetermined attenuation value) 17), a signal generator (10) provided with a level adjuster (20) that adjusts the signal level of the modulated signal to a predetermined signal level and outputs the signal level to the step attenuator. The signal level changing means (21) for changing the signal level of the modulation signal in accordance with the input control signal and outputting it to the step attenuator, and the signal level changing based on the output signal level of the signal level changing means Detection level setting means (23) for passing or attenuating the output signal of the means, and detection means (2) for detecting the output signal of the detection level setting means And a signal level control means (27) for outputting the control signal to the signal level changing means so that the output signal level of the signal level changing means becomes the predetermined signal level based on the output signal level of the detecting means. And a configuration provided with.

  With this configuration, in the signal generation device according to claim 1 of the present invention, the detection level setting means passes or attenuates the output signal of the signal level changing means based on the output signal level of the signal level changing means, The dynamic range of the output signal level of the level adjuster can be made wider. Therefore, the signal generator according to claim 1 of the present invention can ensure a wide dynamic range of the output signal level without increasing the number of attenuator sections of the step attenuator.

  In the signal generator according to claim 2 of the present invention, the detection level setting means includes a passing section (23a) for passing the output signal of the signal level changing means, and the output signal of the signal level changing means is attenuated by a predetermined amount. At least one attenuating section (23b) that selects one of the passing section and the attenuating section and sets the output signal level of the signal level changing means. Yes.

  With this configuration, the signal generation device according to claim 2 of the present invention selects either one of the passing unit and the attenuating unit to pass or attenuate the output signal of the signal level changing unit, and outputs the level adjuster. By making the dynamic range of the signal level wider, the dynamic range of the output signal level can be secured in a wide range without increasing the number of attenuator sections of the step attenuator.

  In the signal generator according to claim 3 of the present invention, the attenuator sets the signal level of the output signal of the signal level changing means within a predetermined signal level range that can be detected by the detecting means. It has the composition which is.

  With this configuration, the signal generator according to claim 3 of the present invention sets the signal level of the output signal of the signal level changing means within a predetermined signal level range that can be detected by the detecting means, and By making the dynamic range of the output signal level wider, it is possible to ensure a wide dynamic range of the output signal level without increasing the number of attenuator sections of the step attenuator.

  According to a fourth aspect of the present invention, there is provided a signal generation method for modulating a baseband signal to generate a modulated signal, and a step attenuator for attenuating an input signal by a predetermined attenuation value (14). 17), and a signal generation method using a signal generator (10) provided with a level adjuster (20) that adjusts the signal level of the modulation signal to a predetermined signal level and outputs the signal level to the step attenuator The signal level changing step (S21) for changing the signal level of the modulation signal according to the input control signal, and the output signal of the signal level changing step is passed based on the output signal level of the signal level changing step. Alternatively, a detection level setting step (S23) for attenuating, and a detection step (S24) for detecting the output signal of the detection level setting step. , Based on the output signal level of said detection step, the output signal level of the modulated signal has a structure including a control signal level control step (S26) so that the predetermined signal level.

  With this configuration, in the signal generation method according to claim 4 of the present invention, in the signal level attenuation step, the output signal of the signal level changing means is passed or attenuated based on the output signal level of the signal level changing means, The dynamic range of the output signal level of the level adjuster can be made wider. Therefore, the signal generator according to claim 1 of the present invention can ensure a wide dynamic range of the output signal level without increasing the number of attenuator sections of the step attenuator.

  The present invention can provide a signal generation device and a signal generation method having an effect that a wide dynamic range of an output signal level can be secured without increasing the number of attenuator sections of a step attenuator. .

It is a block block diagram in one Embodiment of the signal generator which concerns on this invention. It is a figure which shows the reference value setting table in one Embodiment of the signal generator which concerns on this invention. It is a figure which shows the power level range and dynamic range of a detector and detector input level setting device in one Embodiment of the signal generator which concerns on this invention. It is a flowchart in one Embodiment of the signal generator which concerns on this invention. 5 is a flowchart showing level control of a level adjuster in an embodiment of a signal generator according to the present invention.

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

  First, the configuration of an embodiment of a signal generator according to the present invention will be described.

  As shown in FIG. 1, the signal generator 10 in this embodiment includes a waveform data storage unit 11, digital analog converters (DACs) 12 and 13, a quadrature modulator 14, a local oscillator 15, a step attenuator (step ATT) 17, An operation unit 18, a setting unit 19, and a level adjuster 20 are provided.

  The waveform data storage unit 11 stores digital baseband waveform data as a plurality of test signal data for testing the device under test. The tester can operate the operation unit 18 and select and output the test signal data stored in the waveform data storage unit 11 via the setting unit 19. The test signal data includes baseband waveform data of an I-phase component (in-phase component) and a Q-phase component (orthogonal component). The waveform data is generated by, for example, a DSP (Digital Signal Processor) not shown.

  Each of the DACs 12 and 13 converts the digital baseband signal waveform data of the I-phase component and Q-phase component output from the waveform data storage unit 11 into an analog value and outputs the analog value to the quadrature modulator 14. .

  The local oscillator 15 generates a local oscillation signal having a local oscillation frequency based on a setting signal from the setting unit 19 and outputs the local oscillation signal to the quadrature modulator 14.

  The quadrature modulator 14 includes multipliers 14a and 14b, a 90-degree phase shifter 14c, and an adder 14d, and includes an I-phase component from the DAC 12 and a Q-phase component from the DAC 13, and a local oscillation signal input from the local oscillator 15. Is multiplied to perform quadrature modulation and frequency conversion to generate a radio frequency signal (RF signal) and output it to the level adjuster 20. This quadrature modulator 14 constitutes a modulation signal generating means according to the present invention.

  The level adjuster 20 adjusts the power level of the output signal of the quadrature modulator 14 to a predetermined power level and outputs it to the step ATT 17. The level adjuster 20 includes a variable attenuator 21, an amplifier 22, a detector input level setter 23, A detector 24, a reference value output unit 26, and a comparator 27 are provided.

  The variable attenuator 21 receives a control signal for setting the attenuation amount from the comparator 27, and an attenuation amount for attenuating the power of the output signal of the quadrature modulator 14 is set in accordance with this control signal. ing. The variable attenuator 21 can set a continuous fine attenuation amount, for example. Here, the variable attenuator 21 constitutes a signal level changing means according to the present invention. In the present embodiment, the variable attenuator 21 that attenuates the output signal of the quadrature modulator 14 is exemplified as the signal level changing means according to the present invention. However, the present invention is not limited to this, and the quadrature modulator is not limited thereto. Any amplifier that can change the signal level of the 14 output signals may be used.

  The amplifier 22 amplifies the output signal of the variable attenuator 21. A reference point for level adjustment in the level adjuster 20 is provided on the output side of the amplifier 22. The signal set to a predetermined power level at this reference point is output to the detector input level setting unit 23 and step ATT17.

  The detector input level setting unit 23 includes a passing part 23a that passes the input signal as it is, an attenuating part 23b that attenuates the input signal by a predetermined attenuation, a selector switch 23c that selects one of the passing part 23a and the attenuating part 23b, and 23d. The changeover switches 23c and 23d are operated by a setting signal from the setting unit 19. The illustrated example is a state in which the changeover switches 23c and 23d are selecting the attenuation unit 23b. The detector input level setting unit 23 constitutes detection level setting means according to the present invention.

  The passage part 23a is formed of, for example, a conductor wiring provided on the substrate. The attenuating unit 23b is configured by a resistor or other attenuating element or an attenuating circuit such as a π-type attenuator, and is matched with the impedance on the input side and the output side. In the illustrated example, the number of the attenuating units 23b is one, but the detector input level setting unit 23 may include a plurality of attenuating units 23b having different attenuation amounts.

  The detector 24 detects the output signal of the detector input level setting unit 23 and outputs it to the comparator 27. This detector 24 constitutes a detection means according to the present invention.

  The reference value output unit 26 generates a reference level signal set by the setting signal from the setting unit 19 and outputs the reference level signal to the comparator 27.

  The comparator 27 compares the output signal level of the detector 24 with the reference level signal from the reference value output unit 26, and the power level of the reference point R (hereinafter referred to as “reference point level”) is, for example, −. A control signal for setting the attenuation is output to the variable attenuator 21 so as to be 10 dBm. The comparator 27 constitutes signal level control means according to the present invention.

  Step ATT17 is an ATT in which the attenuation is set in a step larger than the above-described variable attenuator 21 (for example, 5 dB step). That is, a relatively large attenuation amount is set in step ATT17, and a fine attenuation amount is set in the variable attenuator 21 described above. The step ATT 17 includes a plurality of attenuator sections each having a predetermined amount of attenuation, and the amount of attenuation can be stepped by a combination of the amounts of attenuation of each attenuator section. The step ATT 17 attenuates the input signal by the attenuation amount set by the setting signal from the setting unit 19 and outputs an RF test signal having a power level desired by the tester.

  The operation unit 18 is operated by a tester in order to make settings relating to test conditions and test procedures, and includes, for example, an input device such as a keyboard, dial, or mouse, and a control circuit that controls these devices. . The test conditions set by the tester include, for example, waveform data stored in the waveform data storage unit 11, the output level of the RF test signal output by the step ATT 17 and the radio frequency.

  The setting unit 19 is constituted by a microcomputer, for example, and controls the entire apparatus. In addition, the setting unit 19 generates a setting signal for setting each test condition based on each test condition set by the tester operating the operation unit 18, the waveform data storage unit 11, the local oscillator 15, the step ATT 17, and the detector input. Each test condition is set by outputting to the level setter 23 and the reference value output unit 26, respectively.

  Here, as a setting for the reference value output unit 26, the setting unit 19 operates as follows based on, for example, a reference value setting table as shown in FIG.

  In the reference value setting table, with respect to the output level of the signal generator 10 set by the user, the attenuation of step ATT17, the target value of the reference point R, the setting of the detector input level setting unit 23, the reference value output unit 26 The output values correspond to each other.

  As shown in FIG. 2, the amount of attenuation at step ATT17 is predetermined with respect to the output level. The target value of the reference point R is a value obtained by adding the attenuation amount of the step ATT17 to the output level, and this item may be excluded from the reference value setting table. The setting of the detector input level setting unit 23 is determined in advance as to whether the output level is attenuated (−20 dB) or passed (0 dB). In the illustrated example, the output level is −9.9 dB or more. When the attenuation and output level are -10.0 or less, the passage is set. The output value of the reference value output unit 26 represents a value obtained by adding the attenuation value set by the detector input level setting unit 23 to the target value of the reference point R.

  For example, when the user sets the output level of the signal generator 10 to +10.0 dBm, the setting unit 19 sets the attenuation of step ATT17 to 0 dB based on the reference value setting table, and the detector input level setting unit 23 Is set to the selection of the attenuation unit 23b, and a control signal for setting the reference point level to +10.0 dBm is output to the reference value output unit 26. In this case, since the output level of the detector 24 decreases according to the attenuation amount of the attenuation unit 23b, the control signal for the reference value output unit 26 is in accordance therewith.

  Further, for example, when the user sets the output level of the signal generator 10 to -10.0 dBm, the setting unit 19 sets the attenuation of step ATT17 to 20 dB based on the reference value setting table, and the detector input level The setting unit 23 is set to select the passage unit 23a, and a control signal for setting the reference point level to +10.0 dBm is output to the reference value output unit 26.

  The setting unit 19 can also correct the frequency characteristic of the analog circuit by correcting the reference level set in the reference value output unit 26. For example, the setting unit 19 obtains the frequency characteristics of the amplifier 22, the attenuation unit 23b, and the detector 24 in advance, corrects these frequency characteristics to a flat value, and sets the reference point level to a desired value. The reference level of the output unit 26 can also be set.

  Next, the function of the detector input level setting unit 23 will be described.

  In general, a level adjuster of a signal generator includes a detector. The range of the power level that the detector can detect well, that is, the dynamic range of the detector is narrower than the dynamic range of the other components of the level adjuster, and the dynamic range of the detector determines the dynamic range of the level adjuster. Yes.

  In the present embodiment, as shown in FIG. 3, the power level range in which the detector 24 can detect well is set to −50 dBm to −10 dBm. In this case, the dynamic range of the detector 24 is 40 dB, which is also the dynamic range of the level adjuster 20.

  Further, it is assumed that the attenuation amount of the passage unit 23a of the detector input level setting unit 23 is 0 dB, and the attenuation amount of the attenuation unit 23b is 20 dB. In this case, in a state where the detector input level setting unit 23 selects the passage unit 23a, the detector 24 can detect an RF signal having a reference point level of −50 dBm to −10 dBm. On the other hand, in a state where the detector input level setting unit 23 selects the attenuating unit 23b, the detector 24 can detect an RF signal having a reference point level of −30 dBm to +10 dBm.

  Therefore, for example, when the reference point level is set to −50 dBm to −10 dBm (−50 dBm or more and less than −10 dBm), the setting unit 19 passes the RF signal through the passage unit 23a and −10 dBm to +10 dBm (−10 dBm to +10 dBm or less). ), The RF signal is passed through the attenuator 23b. As a result, the dynamic range of the level adjuster 20 is expanded by 20 dB from the beginning to 60 dB. Here, assuming that the maximum attenuation of step ATT17 is 120 dB, the maximum attenuation 140 dB is obtained by adding the dynamic range 20 dB of the level adjuster 20 to this. Therefore, the signal generator 10 can widen the dynamic range of the output signal by 20 dB compared to the conventional case.

  Next, the operation of the signal generator 10 in this embodiment will be described with reference to the block diagram shown in FIG. 1 and the flowchart shown in FIG.

  When the tester operates the operation unit 18, the test condition desired by the tester is input, and the test unit sets the test condition in each unit by the setting unit 19 (step S11). Specifically, the setting unit 19 uses a signal for designating waveform data in the waveform data storage unit 11, a signal for designating the local oscillation frequency in the local oscillator 15, and a signal for designating the attenuation amount in the step ATT 17, as a reference value. A signal indicating the reference value is output to the output unit 26.

  The setting unit 19 determines whether the set value of the reference point level is -10 dBm to +10 dBm or -50 dBm to -10 dBm (step S12).

  In step S12, when the set value of the reference point level is −50 dBm to −10 dBm, the setting unit 19 causes the changeover switches 23c and 23d of the detector input level setting unit 23 to select the passage unit 23a (step S13). On the other hand, when the set value of the reference point level is −10 dBm to +10 dBm, the setting unit 19 causes the changeover switches 23c and 23d of the detector input level setting unit 23 to select the attenuation unit 23b (step S14).

  The waveform data storage unit 11 outputs I-phase component and Q-phase component baseband waveform data designated by the tester to the DACs 12 and 13, respectively (step S15).

  The DACs 12 and 13 convert the baseband waveform data of the I-phase component and the Q-phase component into analog waveform data (step S16) and output the analog waveform data to the quadrature modulator 14.

  The quadrature modulator 14 receives a baseband signal from the DACs 12 and 13 and a local oscillation signal from the local oscillator 15 and multiplies the baseband signal and the local oscillation signal to perform quadrature modulation and frequency conversion to generate an RF signal. Generate (step S17), and output the generated RF signal to the level adjuster 20.

  The level adjuster 20 performs level control for setting the level of the input RF signal to 0 dBm, for example (step S20), and outputs the result to step ATT17.

  Step ATT17 attenuates the RF signal by the attenuation amount set by setting unit 19 (step S18) and outputs it as an RF test signal (step S19). The test target of the output destination is, for example, a mobile communication terminal or base station, or a device used for them.

  Next, the operation of the level adjuster 20 in step S20 will be described based on the block configuration diagram shown in FIG. 1 and the flowchart shown in FIG. Here, an example is given in which the level adjuster 20 adjusts the reference point level to 0 dBm. In this case, in the detector input level setting unit 23, the changeover switches 23c and 23d select the attenuating unit 23b side.

  The variable attenuator 21 attenuates the RF signal output from the quadrature modulator 14 to a predetermined value based on the attenuation amount setting control signal from the comparator 27 (step S21), and outputs it to the amplifier 22.

  The amplifier 22 amplifies the RF signal output from the variable attenuator 21 with a predetermined amplification factor (step S22), and outputs the amplified signal to the step ATT17 and the detector input level setting unit 23.

  The detector input level setting unit 23 attenuates the input RF signal by 20 dB by the attenuating unit 23b (step S23) and outputs the attenuated signal to the detector 24.

  The detector 24 detects the input RF signal (step S24) and outputs the detection signal to the comparator 27.

  The comparator 27 compares the signal level output from the detector 24 with the reference signal level from the reference value output unit 26 (step S25), and outputs a control signal for setting the attenuation so that the reference point level becomes 0 dBm. It outputs to the variable attenuator 21 (step S26). Here, the reference signal level corresponds to the level of the detection signal detected after being attenuated by 20 dB.

  In the description of steps S21 to S26 described above, an example is given in which the reference point level is 0 dBm and the reference point level setting value is −10 dBm to +10 dBm. When the setting value of the quasi-point level is -50 dBm to -10 dBm, the selector switches 23c and 23d select the passing unit 23a side in the detector input level setting unit 23, and the RF signal is allowed to pass through without being attenuated in step S23. It becomes.

  As described above, in the signal generator 10 according to the present embodiment, the detector input level setting unit 23 passes or attenuates the output signal of the level adjuster 20 based on the output signal level of the level adjuster 20. The dynamic range of the output signal level of the level adjuster 20 can be made wider.

  Therefore, the signal generator 10 in the present embodiment can ensure a wide dynamic range of the output signal level without increasing the number of attenuator sections in step ATT17.

  As described above, the signal generation device and the signal generation method according to the present invention have the effect of ensuring a wide dynamic range of the output signal level without increasing the number of attenuator sections of the step attenuator, It is useful as a signal generating apparatus and a signal generating method for generating a test signal in a characteristic test for a mobile communication terminal such as a mobile phone or a mobile terminal.

10 Signal Generator 11 Waveform Data Storage Unit 12, 13 DAC
14 Quadrature modulator (modulation signal generating means)
15 Local oscillator 17 Step ATT
18 Operation section 19 Setting section 20 Level adjuster 21 Variable attenuator (signal level changing means)
22 Amplifier 23 Detector input level setting device (detection level setting means)
23a passing section 23b attenuating section 23c, 23d changeover switch 24 detector (detection means)
26 reference value output unit 27 comparator (signal level control means)

Claims (4)

A modulation signal generator (14) that modulates a baseband signal to generate a modulation signal and a step attenuator (17) that attenuates an input signal with a predetermined attenuation value and outputs the attenuated signal are provided. In the signal generator (10) including a level adjuster (20) that adjusts the signal level to a predetermined signal level and outputs the signal level to the step attenuator.
The level adjuster is
Signal level changing means (21) for changing the signal level of the modulation signal in accordance with an input control signal and outputting the signal to the step attenuator;
Detection level setting means (23) for passing or attenuating the output signal of the signal level changing means based on the output signal level of the signal level changing means;
Detection means (24) for detecting an output signal of the detection level setting means;
Signal level control means (27) for outputting the control signal to the signal level changing means so that the output signal level of the signal level changing means becomes the predetermined signal level based on the output signal level of the detection means; A signal generator characterized by comprising. The detection level setting means includes:
A passing section (23a) for passing the output signal of the signal level changing means;
And at least one attenuation unit (23b) for attenuating the output signal of the signal level changing unit by a predetermined amount, and selecting one of the passing unit and the attenuation unit to output the signal level changing unit The signal generator according to claim 1, wherein the signal generator sets a level.   The said attenuation part sets the signal level of the output signal of the said signal level change means within the predetermined signal level range which the said detection means can detect, The said Claim 2 characterized by the above-mentioned. Signal generator. A modulation signal generator (14) that modulates a baseband signal to generate a modulation signal and a step attenuator (17) that attenuates an input signal with a predetermined attenuation value and outputs the attenuated signal are provided. In the signal generation method using the signal generator (10) including the level adjuster (20) that adjusts the signal level to a predetermined signal level and outputs the signal level to the step attenuator.
A signal level changing step (S21) for changing the signal level of the modulation signal in accordance with an input control signal;
A detection level setting step (S23) for passing or attenuating the output signal of the signal level changing step based on the output signal level of the signal level changing step;
A detection step (S24) for detecting the output signal of the detection level setting step;
And a signal level control step (S26) for controlling the output signal level of the modulation signal to be the predetermined signal level based on the output signal level of the detection step.

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