JP5588425B2 - Step attenuator and signal generator having the same - Google Patents

Description

  The present invention relates to a step attenuator that changes an attenuation amount of an input signal in a step-like manner and a signal generation device including the step attenuator.

  Conventionally, as a signal generator provided with this type of step attenuator, for example, the one described in Patent Document 1 is known.

  The signal generation device described in Patent Literature 1 outputs a signal source that generates a signal, a level correction unit that corrects the signal from the signal source to a predetermined level, and a signal from the level correction unit that is attenuated to a predetermined level. And a step attenuator for outputting a test signal having a radio frequency and a signal level designated by the tester.

  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. In general, the conventional step attenuator has a configuration in which each attenuator section is covered with a metal shield case in order to improve isolation between the input and output with respect to a high frequency signal.

JP 2005-249626 A

  However, in the conventional signal generator, it is necessary to generate a test signal having a wide range of frequencies from kilohertz to gigahertz, but it is difficult to increase the maximum attenuation of the step attenuator for a wide range of frequencies. In order to make the dynamic range of the output signal level variable in a wider range, further improvement of isolation has been demanded.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a step attenuator and a signal generator including the step attenuator that can increase isolation between input and output as compared with the conventional one. .

The step attenuator according to claim 1 of the present invention is formed on the substrate (30), and the amount of attenuation can be varied by a predetermined step value by combining a plurality of attenuators (21 to 26) in one direction. In the attenuator (20), a signal line (1 to 7) for inputting or outputting a signal to each attenuator and a plurality of attenuators arranged on the substrate and accommodating the plurality of attenuators in a predetermined number. A shielding case (40) having a storage chamber (40a to 40d), and the signal line is formed on a surface signal line (1, 3, 7) formed on a surface of the substrate and an inner layer of the substrate. and formed inner-layer signal line (32a, 32 b), wherein the shield case is provided with a first and a second partition wall for partitioning each accommodating chamber (41 to 45), before The first partition wall (41) has a first contact part (41b) that contacts the surface of the substrate and an opening part (41a) that opens a part of the first contact part and passes the surface signal line. The second partition wall (42) includes a second contact portion (42a) that contacts a surface region of the substrate including a part of a projection region obtained by projecting the inner layer signal line onto the surface of the substrate. And at least one pair of the first partition wall and the second partition wall is provided alternately from the signal input side to the output side.

With this configuration, the step attenuator according to claim 1 of the present invention includes the first and second partition walls, so that the isolation between the input and the output can be increased as compared with the conventional one. Also, with this configuration, the step attenuator according to claim 1 of the present invention enhances the isolation between the inner layer signal lines connected to the surface signal line provided in the inner layer of the substrate on which the second partition wall is located. it is possible.

  The present invention can provide a step attenuator having an effect that isolation between input and output can be increased as compared with the conventional one, and a signal generating device including the step attenuator.

It is a block block diagram in one Embodiment of the signal generator which concerns on this invention. FIG. 4 is a diagram schematically showing a state in which step ATT20 is mounted on a multilayer substrate 30 in an embodiment of a signal generating apparatus according to the present invention. FIG. 4 is a diagram showing a state where step ATT20 is covered with a shield case 40 in one embodiment of a signal generator according to the present invention. FIG. 3 is a perspective view showing a configuration of a partition wall 41 in an embodiment of a signal generator according to the present invention. FIG. 3 is a perspective view showing a configuration of a partition wall 42 in an embodiment of a signal generator according to the present invention. In one Embodiment of the signal generator which concerns on this invention, it is a graph which shows the experimental data which compared the thing (solid line) concerning the isolation | separation thing (solid line) about the isolation characteristic. FIG. 10 is a diagram showing a step ATT according to a first other aspect in the embodiment of the signal generating device according to the present invention. In one Embodiment of the signal generator which concerns on this invention, it is a figure which shows step ATT which concerns on a 2nd other aspect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An example in which the step attenuator according to the present invention is applied to a signal generator will be described.

  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, and an automatic level control circuit (ALC) 17. , An operation unit 18, a setting unit 19, and a step attenuator (step ATT) 20.

  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. The waveform data storage unit 11 constitutes a baseband signal output unit according to the present invention.

  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. This local oscillator 15 constitutes a local oscillation signal generating means according to the present invention.

  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 ALC 17. This quadrature modulator 14 constitutes a radio frequency signal generating means according to the present invention.

  The ALC 17 adjusts the power level of the output signal of the quadrature modulator 14 to a predetermined power level and outputs it to the step ATT20. The power level set by the ALC 17 is set by a setting signal from the setting unit 19. The ALC 17 can adjust the output signal level in units of 0.1 dB, for example. The ALC 17 constitutes signal level setting means according to the present invention.

  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 ATT20, and the radio frequency.

  The setting unit 19 is constituted by a microcomputer, for example, and controls the entire apparatus. The setting unit 19 also sends setting signals for setting each test condition to the waveform data storage unit 11, the local oscillator 15, the ALC 17, and the step ATT 20 based on each test condition set by the tester operating the operation unit 18. Output and set each test condition.

  Here, as a setting for the ALC 17, for example, when the user sets the output level of the signal generation device 10 to −40.2 dBm, the setting unit 19 sets the attenuation of the step ATT 20 to 30 dB, A control signal for setting the output signal level to -10.2 dBm is output.

  The step ATT20 includes a plurality of ATT units 21 to 26, and is an ATT that can attenuate the level of the input RF signal by a predetermined attenuation amount step. The attenuation amount of step ATT20 is set by a setting signal from the setting unit 19. The detailed configuration of step ATT20 will be described with reference to FIG.

  FIG. 2 schematically shows a state in which the step ATT 20 is mounted on the multilayer substrate 30. The step ATT20 is covered with a shield case as will be described later, but FIG. 2 shows a state in which the shield case is removed.

  As shown in FIG. 2A, the step ATT20 has four sections S1 to S4. Sections S1 to S3 include ATT portions 21 to 23, respectively. Section S4 includes three ATT units 24-26 connected in series. The symbol “A” described in FIG. 2A represents ATT.

  The ATT unit 21 includes two changeover switches (SW) 21a and 21c and an ATT 21b having an attenuation of 40 dB. As shown in FIG. 2B, the switching SWs 21a and 21c are configured to switch between an attenuation state for selecting the ATT 21b and a bypass state for selecting the surface signal line 31a that bypasses the ATT 21b. That is, the switching SWs 21a and 21c can switch the attenuation amount of the ATT unit 21 to 40 dB or 0 dB. Switching of the attenuation amount by the switching SWs 21 a and 21 c is performed based on a setting signal from the setting unit 19. Similarly, in the ATT units 22 to 26, the attenuation state and the bypass state can be switched by each switching SW.

  A surface signal line 1 formed on the surface of the multilayer substrate 30 is connected to the switching SW 21 a of the ATT unit 21.

  A surface signal line is formed between the ATT portions 21 and 22 via an inner layer signal line (described later) of the multilayer substrate 30. That is, between the SW 21c of the ATT portion 21 and the SW 22a of the ATT portion 22, the surface signal lines 2a and 2d formed on the surface of the multilayer substrate 30, the inner layer signal line (not shown), the surface signal line 2a, 2d and the inner layer signal lines are connected by interlayer signal lines 2b and 2c. Here, the interlayer signal lines 2b and 2c are formed, for example, by performing panel plating on through holes or via holes formed by drilling or laser processing.

  The ATT portions 22 and 23 are connected by a surface signal line 3 formed on the surface of the multilayer substrate 30.

  The space between the ATT portions 23 and 24 is the same as that between the ATT portions 21 and 22 described above, and the surface signal lines 4a and 4d formed on the surface of the multilayer substrate 30, the inner layer signal lines, the surface signals. The lines 4a and 4d are connected to each other by interlayer signal lines 4b and 4c that connect the inner layer signal lines.

  Surface signal lines 5 and 6 formed on the surface of the multilayer substrate 30 are connected between the ATT portions 24 and 25 and between the ATT portions 25 and 26, respectively. A surface signal line 7 formed on the surface of the multilayer substrate 30 is connected to the switching SW 26 c of the ATT unit 26.

  Next, a configuration in which step ATT20 is covered with a shield case 40 will be described with reference to FIG. FIG. 3A is a plan view of the step ATT 20 including a cross-sectional view of the shield case 40, and FIG. 3B is a cross-sectional view of the step ATT 20 covered with the shield case 40.

  The multilayer substrate 30 has a surface metal layer 31 formed on the surface and constituting the above-described surface signal lines 5 and 6, a first metal inner layer 32 constituting the above-described inner signal line, and a second metal inner layer 33 to be grounded.

  The shield case 40 includes partition walls 41 to 45, side walls 46 and 47, an upper wall 48, and storage chambers 40a to 40d formed by these walls. The shield case 40 is formed, for example, by being integrally formed by aluminum die casting. However, the shield case 40 may be formed by a process such as punching, bending, or welding using a press working technique.

  The partition walls 41, 43, and 45 and the partition walls 42 and 44 have different shapes. Here, the partition walls 41, 43 and 45 each constitute a first partition wall according to the present invention. Moreover, the partition walls 42 and 44 each constitute a second partition wall according to the present invention.

  As shown in FIG. 4, the partition wall 41 has an opening 41a and a contact portion 41b. The opening 41 a is formed by opening a part of the contact portion 41 b that comes into contact with the surface of the multilayer substrate 30, and allows the surface signal line 1 to pass therethrough. The opening 41a is set such that the width dimension W and the height dimension H are as small as possible in order to suppress electromagnetic coupling between the surface signal line 1 and the partition wall 41 with respect to the operating frequency. In addition, the contact part 41b comprises the 1st contact part which concerns on this invention.

  The partition walls 43 and 45 also have the same configuration as the partition wall 41 although not shown. In the example shown in FIG. 4, the partition wall 41 is disposed so as to be orthogonal to the surface signal line 1, but is not limited to this, and the partition wall 41 and the surface signal line 1 intersect at an arbitrary angle. It may be a configuration.

  As shown in FIG. 5, the partition wall 42 has a contact portion 42 a that contacts the surface of the multilayer substrate 30. The surface signal line 2a is connected to the surface signal line 2d via the interlayer signal lines 2b and 2c and the inner layer signal line 32a. As shown in the figure, the contact portion 42 a of the partition wall 42 comes into contact with the surface region of the multilayer substrate 30 including a part of the projection region obtained by projecting the inner signal line 32 a onto the surface of the multilayer substrate 30. In addition, the contact part 42a comprises the 2nd contact part which concerns on this invention.

  Although not shown, the partition wall 44 has the same configuration as the partition wall 42. In the example shown in FIG. 5, the partition wall 42 is arranged so as to be orthogonal to the inner layer signal line 32a. However, the present invention is not limited to this, and the partition wall 42 and the inner layer signal line 32a intersect at an arbitrary angle. It may be a configuration.

  Returning to FIG. 3, the ATT units 21 to 26 will be described. The attenuation amounts of the ATTs included in the ATT units 21 to 26 are different. The attenuation amount is 40 dB for the ATT 21b, 20 dB for the ATT 22b, 40 dB for the ATT 23b, 5 dB for the ATT 24b, 10 dB for the ATT 25b, and 5 dB for the ATT 26b. With this configuration, the step ATT20 can set the attenuation from 0 dB to 120 dB in 5 dB steps.

  Here, in this embodiment, the reference attenuation amount is set to 20 dB, and the ATT units 21 to 26 are accommodated in the accommodation chambers 40a to 40d based on the reference attenuation amount. That is, the ATT units 21 to 23 having an attenuation amount of 20 dB or more are accommodated in the accommodation chambers 40a to 40c, respectively. The ATT units 24 to 26 having an attenuation of less than 20 dB are accommodated in one accommodation chamber 40d. The reference attenuation is obtained in advance by experiment or simulation. With this configuration, the step ATT 20 can accommodate a plurality of ATT portions 24 to 26 that are not easily affected by signal leakage between input and output in one accommodation chamber 40d, so that the number of partition walls can be reduced and the structure of the shield case 40 can be reduced. Can be simplified.

  Further, among the ATT units 21 to 26, an ATT unit 22 having a smaller attenuation than these is provided between the ATT units 21 and 23 having the maximum attenuation 40 dB. This is because the attenuation characteristic of the step ATT20 tends to be stabilized when the ATT having a relatively large attenuation is separated as much as possible. Therefore, it is desirable to obtain beforehand an ATT portion that has a relatively large attenuation and is preferably not adjacent to each other by experiment or simulation.

  Further, the partition wall 41, 42, 43, 44 and 45 are sequentially provided in the step ATT20 from the input side to the output side. That is, the partition wall 41, 43, 45 (first partition wall) and the partition walls 42, 44 (second partition wall) are alternately provided in the step ATT20. With this configuration, the step ATT 20 can increase the isolation between input and output as compared with the case where all the partition walls are formed by the first partition walls or the partition walls formed by the second partition walls.

  In the example shown in FIG. 3, the partition walls 41 and 42 and the partition walls 43 and 44 include two pairs of the first partition wall and the second partition wall. Accordingly, it is desirable to increase or decrease the number of pairs of the first partition wall and the second partition wall.

  Next, the isolation characteristic of step ATT20 in this embodiment is demonstrated using FIG. FIG. 6 shows experimental results comparing the conventional step ATT (broken line) with the step ATT20 (solid line) in the present embodiment for the isolation characteristics in the frequency range from 100 MHz to 6000 MHz. In this experiment, the ATT units 21 to 26 were not allowed to function, and a continuous wave having a signal level of 0 dBm was used as an input signal for isolation measurement.

  As shown in FIG. 6, the isolation of the conventional step ATT is −113 dB or less. Logically, it is impossible to obtain an attenuation equal to that of isolation. If the isolation is about −113 dB, the maximum attenuation is a step ATT of about −80 dB.

  On the other hand, the isolation of step ATT20 in this embodiment can secure −150 dB or less, which is improved by 40 dB from the conventional one. This step ATT20 is practical as a step ATT having a maximum attenuation of −120 dB.

  Next, the operation of the signal generation apparatus 10 in the present embodiment will be described using the block configuration diagram shown in FIG.

  When the tester operates the operation unit 18, test conditions desired by the tester are input, and the test unit sets the test conditions in each unit. Specifically, the setting unit 19 outputs a signal designating waveform data to the waveform data storage unit 11 and a signal designating local oscillation frequency to the local oscillator 15. Further, the setting unit 19 outputs a signal designating the power level of the output signal to the ALC 17 and a signal designating the attenuation amount to the step ATT20.

  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.

  The DACs 12 and 13 convert the baseband waveform data of the I-phase component and the Q-phase component into analog waveform data, 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 quadrature modulation signal and the local oscillation signal to perform quadrature modulation and frequency conversion to perform RF conversion. A signal is generated, and the generated RF signal is output to the ALC 17.

  The ALC 17 performs level control for setting the level of the input RF signal to −10 dBm, for example, and outputs the result to step ATT20.

  The step ATT20 attenuates the RF signal by the attenuation amount set by the setting unit 19 and outputs it as an RF test signal. The test target of the output destination is, for example, a mobile communication terminal or base station, or a device used for them.

  As described above, the signal generation device 10 according to the present embodiment includes the partition walls 41, 43, and 45 and the partition walls 42 and 44. The signal lines are arranged at the positions of the partition walls 41, 43, and 45 of the multilayer substrate 30. Since the signal line is passed on the inner layer side of the multilayer substrate 30 at the position of the partition walls 42 and 44, the isolation between the input and output can be improved as compared with the conventional one.

  Next, another aspect of the step ATT will be described with two examples.

  The step ATT according to the first other aspect is formed on the multilayer substrate 50 as shown in FIG. The multilayer substrate 50 has a surface metal layer 51 formed on the surface, a first metal inner layer 52 and a second metal inner layer 53 constituting an inner signal line, and a third metal inner layer 54 that is grounded.

  As shown in the drawing, at the position of the partition wall 42, the inner layer signal line 52a formed in the first metal inner layer 52 in the multilayer substrate 50 is connected to the interlayer signal lines 2b and 2c. Further, at the position of the partition wall 44, the inner layer signal line 53a formed in the second metal inner layer 53 in the multilayer substrate 50 is connected to the interlayer signal lines 3b and 3c. In the step ATT having this configuration, the inner layer signal line 52a and the inner layer signal line 53a are formed in different layers, so that the isolation between the inner layer signal lines is improved. Isolation can be significantly improved over that of

  The step ATT according to the second other aspect is formed on the multilayer substrate 60 as shown in FIG. The multilayer substrate 60 has a surface metal layer 61 formed on the surface, a first metal inner layer 62, a second metal inner layer 63 and a third metal inner layer 64 constituting an inner signal line, and a fourth metal inner layer 65 to be grounded.

  As shown in the figure, in this example, the step ATT includes five partition walls 42. The metal inner layers constituting the inner signal line are sequentially formed as a first metal inner layer 62, a second metal inner layer 63, and a third metal inner layer 64 from the signal input side. The step ATT of this configuration improves the isolation between these inner layer signal lines by forming adjacent inner layer signal lines in different layers, and does not use the partition wall 41 having an opening. Isolation on the surface side of the substrate 30 can be greatly improved.

  In the above-described embodiment, as illustrated in FIG. 3, the ATT units 21 to 26 have been described as examples connected in a straight line. However, the present invention is not limited to this, for example, A plurality of ATT units may be arranged in a plane.

  As described above, the step attenuator according to the present invention and the signal generation apparatus including the step attenuator have an effect that isolation between input and output can be increased as compared with the conventional one, and the attenuation amount of the input signal is stepped. The present invention is useful as a step attenuator that changes the shape of a signal and a signal generator equipped with the same.

1, 2a, 2d, 3, 4a, 4d, 5-7, 31a Surface signal line 1a, 1b, 2b, 2c, 3b, 3c, 4b, 4c, 7a, 7b Interlayer signal line 10 Signal generator 11 Waveform data storage (Baseband signal output means)
12, 13 DAC
14 Quadrature modulator (radio frequency signal generating means)
15 Local oscillator (local oscillation signal generating means)
17 ALC (Signal level setting means)
18 Operation section 19 Setting section 20 Step ATT
21-26 ATT part 21a, 21c, 22a, 26c changeover SW
21b, 22b, 23b, 24b, 25b, 26b ATT
30, 50, 60 Multilayer substrate 31, 51, 61 Surface metal layer 32, 52, 62 First metal inner layer 32a, 32b Inner layer signal line 33, 53, 63 Second metal inner layer 40 Shield case 40a, 40b, 40c, 40d Chamber 41, 43, 45 Partition wall (first partition wall)
41a, 43a Opening 41b Contact part (first contact part)
42, 44 Partition wall (second partition wall)
42a Contact part (second contact part)
46, 47 Side wall 48 Upper surface wall 52a, 53a, 62a, 63a, 64a, 62b, 63b Inner layer signal line 54, 64 Third metal inner layer 65 Fourth metal inner layer

Claims (1)

In the step attenuator (20) formed on the substrate (30) and capable of varying the attenuation by a predetermined step value by combining a plurality of attenuators (21 to 26) arranged in one direction,
A signal line (1-7) for inputting or outputting a signal to each attenuator;
A shield case (40) disposed on the substrate and having a plurality of storage chambers (40a to 40d) for storing the plurality of attenuators in a predetermined number;
The signal line is
Surface signal lines (1, 3, 7) formed on the surface of the substrate;
The inner-layer signal line formed on the inner layer of the substrate (32a, 32 b), provided with,
The shield case includes first and second partition walls (41 to 45) that partition the storage chambers,
The first partition wall (41) has a first contact part (41b) that contacts the surface of the substrate and an opening part (41a) that opens a part of the first contact part and passes the surface signal line. )
The second partition wall (42) includes a second contact portion (42a) that contacts a surface region of the substrate including a part of a projection region obtained by projecting the inner layer signal line onto the surface of the substrate,
A step attenuator, wherein at least one set of the first partition wall and the second partition wall is alternately provided from the signal input side to the output side.

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