JP4361398B2 - High frequency attenuator and signal generator using the same - Google Patents

Description

  The present invention relates to a high frequency attenuator and a signal generator using the same, for example, a high frequency attenuator used as a step attenuator for changing the level of a high frequency signal, and a signal generator using the same.

  FIG. 6 is a block diagram showing a final output stage of a general signal generator. The signal supplied from the signal source 2 to the level correction unit 3 is input to the digital attenuator unit 10, and outputs a signal to the connector 9 that can set an excellent attenuation amount with a large variable range and step accuracy. The digital attenuator unit 10 is composed of a plurality of attenuation sections including a first section 10a, a second section 10b, a third section 10c, a fourth section 10d, and an nth section 10x. The maximum attenuation is defined by the attenuation resolution and the total attenuation of each section.

  However, the digital attenuator unit 10 has the following problems. The digital attenuator unit 10 uses a highly accurate attenuating element, and uses a switching element (such as a mechanical switch or an electronic switch) having excellent high-frequency characteristics to switch the attenuation amount with high accuracy. However, sufficient current level accuracy cannot be obtained at the output connector 9 simply by adopting the configuration as described above, for measurement of current communication devices.

  For this reason, in a normal signal generator, the output power of the output connector 9 is measured with a power meter or the like, and the deviation from the true value of the measured value is stored in the level correction value storage unit 30 as a level correction value, and the actual level The output level is corrected by adjusting the attenuation amount (or gain) of the level correction unit 3 (variable attenuator or variable gain amplifier) by this correction value at the time of setting, thereby improving the attenuation accuracy.

  However, all combinations of attenuations and correction values of frequency characteristics are collected in a matrix (if the attenuation to obtain the correction value is t (m) and the frequency point is f (n), the correction value is C [t (m), f (n)] and an m × n matrix), it takes a lot of time to acquire the correction data. Further, when the attenuation is set to a large value such as 100 dB or more, the output level of the output connector 9 is lowered, so that measurement with the power meter is impossible. Even when using a measurement device that can measure relative levels in a narrow band and high dynamic range, such as a spectrum analyzer, it is necessary to reduce the resolution bandwidth or increase the number of averages in order to reduce the influence of floor noise. The measurement time per correction value point is significantly increased.

  In order to solve this problem, instead of acquiring all the correction values for each set value of the attenuation amount of the digital attenuator unit 10, a method is considered in which the set values are thinned out and the correction values corresponding to the remaining set values are obtained by calculation. It is done.

The simplest method of this method is as follows.
(1) n in the state where each of the first, second, third, fourth,..., N sections of the digital attenuator unit 10 is set to the attenuating element side and all other sections are set to the passing side. Get the correction value of the type. Here, the correction values of each section are Er (A), Er (B), Er (C), Er (D),..., Er (X), respectively.
(2) The amount of attenuation when a plurality of sections are set on the attenuating element side is the sum of the values of the attenuators and the correction values.
For example, the actual attenuation amount when the second section 10b and the fourth section 10d are set to the attenuation side is [B + D + Er (B) + Er (D)] [dB].

  Considering the above, the correction value acquisition time is 7/127 for a digital attenuator unit of 7 bits (1, 2, 4, 8, 16, 32, 64 dB total 127 dB), for example, 1/18. To decrease. Further, since correction value data near the maximum attenuation is not acquired, the substantial measurement time is further shortened. However, in an actual attenuator, each section has different reflection characteristics at the time of passing and at the time of attenuation. Therefore, the above method cannot correct errors due to mismatch loss between the sections.

  For example, a mismatch error of a maximum of 0.087 dB occurs at a connection portion between sections of VSWR = 1.22, and a maximum mismatch error of 7 sections is 0.52 dB (0.087 × 6). However, in reality, when the isolation between the input and output of each section is small, a change in impedance of a section other than the adjacent section is also affected, so that a larger mismatch error may occur.

Further, Patent Document 1 discloses a method for measuring the S parameter of the through state and the attenuation state of each single section and calculating the attenuation amount of a plurality of sections based on these.
USP 6091247

  However, the method for obtaining the attenuation amount from the S parameter described above obtains cascade connection by multiplication of the S parameter, but originally it is necessary to perform the calculation with the T parameter, and an ordinary digital step attenuator or voltage variable attenuator is required. The change in input / output impedance when switching the attenuation of each section generated in is not considered.

  The present invention has been made to solve such a problem, and each section of the digital attenuator unit has its input / output reflection characteristics changed during bypass (through) / attenuation. It is an object of the present invention to provide a high-frequency attenuator capable of shortening the measurement time and a signal generator using the same by considering the combination of one section and the correction value determination procedure.

In order to solve the above problems, the high frequency attenuation device of the present invention has the following configuration.
An input unit (4) to which a high-frequency signal is input, a digital attenuator unit (1) including a plurality of attenuation sections each having a predetermined attenuation amount, and an output unit (9) that outputs a processed electric signal ) And a combination storage unit (7) in which combinations of the plurality of attenuation sections for setting the attenuation amount of the digital attenuator unit to a desired set attenuation amount are stored, and the digital attenuator unit includes the plurality of attenuation units Attenuation sections of the digital attenuator unit are connected in series, one end of the digital attenuator unit is connected to the input unit, the other end of the digital attenuator unit is connected to the output unit, and the high frequency input from the input unit A plurality of attenuation sections configured with a predetermined combination of signals from the combination storage unit; Umbrella were, in a high frequency damping device for output from the output unit to the desired set attenuation,
The digital attenuator unit has at least four or more attenuation sections, and the attenuation sections include a first maximum attenuation section (1d) that provides the maximum attenuation among the plurality of attenuation sections, and the first attenuation section. A second maximum attenuation section (1e) disposed on one side of the first maximum attenuation section and providing the same attenuation as the first maximum attenuation section, and connected to the other of the first maximum attenuation section. and a 2 or more attenuation sections that give different attenuation adjacent minimum attenuation section one depressed section of the two or more attenuation section that gives the smallest attenuation in the plurality of depressed section , and the sum of the attenuation of the two or more damping section the minimum attenuation section to the maximum attenuation And only a small structure equal to the attenuation attenuation,
The combination of the plurality of attenuation sections stored in the combination storage unit includes a combination in which the digital attenuator unit has a maximum set attenuation amount, and a combination in which the first set attenuation amount is smaller than the maximum set attenuation amount. A second set attenuation amount smaller than the first set attenuation amount,
The combination in the set attenuation amount that is equal to or less than the maximum set attenuation amount and equal to or more than the first set attenuation amount is a combination in which the first maximum attenuation section and the second maximum attenuation section are in an attenuation state.
A combination of attenuation amounts smaller than the first set attenuation amount and greater than or equal to the second set attenuation amount is a combination in which the first maximum attenuation section is in an attenuation state and the second maximum attenuation section is in a bypass state. Yes,
The combination in the set attenuation smaller than the second set attenuation is a combination in which the first maximum attenuation section and the second maximum attenuation section are in a bypass state.

The signal generator using the high frequency attenuator according to claim 2 of the present invention has the following configuration.
The high frequency attenuation according to claim 1, further comprising: a signal source (2) ; a level correction unit (3) for correcting a signal from the signal source by a predetermined level; and the digital attenuator unit for inputting the signal from the level correction unit. A level correction value storage unit (6) for storing correction data of the predetermined level for correcting an error of the apparatus, the digital attenuator unit, and each attenuation section of the digital attenuator unit stored in the combination storage unit relative allowed union, the calculated correction data determined from the actual attenuation, and in accordance with the combination of the depressed section, with operation control unit for varying the (5) a predetermined level correction of the level correcting unit It was.

Furthermore, in the signal generator using the high-frequency attenuator according to claim 3 , the following structure is provided in the signal generator according to claim 2.
The actual attenuation amount is an attenuation amount including an attenuation amount of each attenuation section of the digital attenuator unit as well as a mismatch loss between the attenuation sections, and the arithmetic control unit includes a plurality of consecutive attenuation amounts including the maximum set attenuation amount. the actual attenuation in the set attenuation respectively, calculated from at least three of the actual attenuation, calculates the correction data.

Each section of the digital attenuator unit changes input / output reflection characteristics when bypassed or attenuated. However, the measurement time can be shortened by considering the combination of single sections of each section and the level correction value calculation procedure. it can.

Hereinafter, a high frequency attenuation device and a signal generation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a signal generator using a high frequency attenuation device. FIG.
4 is a section combination table for explaining a combination of sections of the digital attenuator unit 1 and a procedure for calculating a level correction value. FIG. 3 is a table describing a calculation formula for calculating the level correction value. FIG. 4 is a table showing level correction values for the set attenuation amount. FIG. 5 is a table showing section combinations with respect to the set attenuation amount.

  Based on FIG. 1, the operation of the signal generator using the high-frequency attenuator will be described. The set attenuation amount of the digital attenuator unit 1 is set to 95 dB. The combination of each section is such that the first section 1a is attenuated, the second section 1b is bypassed, and the third section 1c is attenuated. The fourth section 1d is in attenuation, the fifth section 1e is in bypass, the sixth section 1f is in attenuation, and the seventh section 1g is in attenuation.

Based on the table shown in FIG. 5 stored in the combination storage unit 7, the arithmetic control unit 5 performs switching control of each section of the digital attenuator unit 1 for the combination of the set attenuation amounts 95 dB. The actual attenuation amount of the set attenuation amount 95 dB is obtained based on the table shown in FIG. The difference between the actual attenuation amount and the set attenuation amount is calculated as a level correction value, and is stored as a table shown in FIG. Here, the level correction value of the set attenuation amount 95 dB is C19. The calculation control unit 5 sets the attenuation amount (or amplification amount) of the level correction unit 3 to C19. The signal output from the signal source 2 is C19 level corrected by the level correction unit 3 and output to the output connector 9 via the digital attenuator unit 1.

  Next, a procedure for obtaining the actual attenuation amount will be described using the table of FIG. Consider a state of 95 dB (G19).

G19 is a state in which a 5 dB (S1) section of the first section is added to the state of 90 dB of G18. Here, it is assumed that the following equation holds.
G19−G18 = G11−G10 (1)
Then, G19 is obtained by calculation as follows.
G19 (95 dB) = G18 (90 dB) + G11 (55 dB) −G10 (50 dB) (2)
In order for the above equation to hold, the following equation must hold.

In order for Formula (1) to hold, the mismatch loss at the input / output of the 5 dB (S1) section needs to be the same for each of G19 and G11, and G18 and G10. (In addition to this, the isolation between the control system and the input / output terminals on the structure is sufficiently large with respect to the attenuation to be inserted, but here this condition is satisfied. To do.)
It is assumed that the external impedance viewed from the input side of the 5 dB (S1) section does not change.

On the output side of the 5 dB (S1) section, the third section 20 dB (S3) is set to the attenuation side in both G18 and G10 states. For this reason, the setting of the 40 dB (S4) section of the fourth section, which is the first maximum attenuation section, is changed, and the input impedance of the 40 dB (S4) section is changed, so that the output side of 5 dB (S1) is generated. The amount of mismatch loss change is 4 times the intensity of the reflected wave on the input side of the 40 dB (S4) section reflected on the output side of the 5 dB (S1) section (G10, G11, G18, G19) When the calculation is performed under the condition that all the polarities are the worst conditions, it can be as small as 0.0055 dB. Actually, there are reflected waves at a plurality of other locations as a cause of mismatch loss, but these influences are scarce under the parameter conditions as in this example.

10dB (S2) section minimum attenuation = 0dB = -S21 (10S2)
20dB (S3) section minimum attenuation = 18dB = -S21 (20S3)
40 dB (S4) section minimum input return loss = 20 dB (with or without attenuation) = -S11 (40S4)
Minimum output return loss of 5 dB (S1) section = 20 dB (during attenuation and regardless of bypass) = -S22 (5S1)
And

[10dB (S2) → 20dB (S3) → 40dB (S4) input reflection → 20dB (S3) → 10dB (S2) → 5dB (S1) output reflection] × 4 = 4 × 20LOG (1 +/- 10 ^ (( S21 (10S2) + S21 (20S3) + S11 (40S4) + S21 (20S3) + S22 (5S1)) / 20) = +/- 0.0055 dB
It becomes. Here, S in S21, S22, and S11 represents an S parameter.

It is a block diagram of a signal generator using a high frequency attenuation device showing an embodiment of the present invention, It is a section combination table for explaining a procedure for calculating a combination of sections of the digital attenuator unit 1 and a level correction value according to an embodiment of the present invention. Is a table describing a calculation formula for calculating a level correction value, showing an embodiment of the present invention, It is a table which shows the level correction value with respect to setting attenuation amount which shows one Embodiment of this invention. FIG. 5 is a table showing section combinations for set attenuation amounts, showing an embodiment of the present invention; It is a block diagram of the signal generator using the conventional high frequency attenuation device which shows one Embodiment of this invention.

Explanation of symbols

1 Digital attenuator unit,
2 signal source,
3 Level correction part,
4 Input section,
5 arithmetic control unit,
6 level correction value storage,
7 Union Memory Department,
8 Formula storage unit,
9 Output section.

Claims (3)

An input unit (4) to which a high-frequency signal is input, a digital attenuator unit (1) including a plurality of attenuation sections each having a predetermined attenuation amount, and an output unit (9) that outputs a processed electric signal ) And a combination storage unit (7) in which combinations of the plurality of attenuation sections for setting the attenuation amount of the digital attenuator unit to a desired set attenuation amount are stored, and the digital attenuator unit includes the plurality of attenuation units Attenuation sections of the digital attenuator unit are connected in series, one end of the digital attenuator unit is connected to the input unit, the other end of the digital attenuator unit is connected to the output unit, and the high frequency input from the input unit A plurality of attenuation sections configured with a predetermined combination of signals from the combination storage unit; Umbrella were, in a high frequency damping device for output from the output unit to the desired set attenuation,
The digital attenuator unit has at least four or more attenuation sections, and the attenuation sections include a first maximum attenuation section (1d) that provides the maximum attenuation among the plurality of attenuation sections, and the first attenuation section. A second maximum attenuation section (1e) disposed on one side of the first maximum attenuation section and providing the same attenuation as the first maximum attenuation section, and connected to the other of the first maximum attenuation section. and a 2 or more attenuation sections that give different attenuation adjacent minimum attenuation section one depressed section of the two or more attenuation section that gives the smallest attenuation in the plurality of depressed section , and the sum of the attenuation of the two or more damping section the minimum attenuation section to the maximum attenuation And only a small structure equal to the attenuation attenuation,
The combination of the plurality of attenuation sections stored in the combination storage unit includes a combination in which the digital attenuator unit has a maximum set attenuation amount, and a combination in which the first set attenuation amount is smaller than the maximum set attenuation amount. A second set attenuation amount smaller than the first set attenuation amount,
The combination in the set attenuation amount that is equal to or less than the maximum set attenuation amount and equal to or more than the first set attenuation amount is a combination in which the first maximum attenuation section and the second maximum attenuation section are in an attenuation state.
A combination of attenuation amounts smaller than the first set attenuation amount and greater than or equal to the second set attenuation amount is a combination in which the first maximum attenuation section is in an attenuation state and the second maximum attenuation section is in a bypass state. Yes,
The high frequency attenuation device according to claim 1, wherein the combination of the set attenuation amounts smaller than the second set attenuation amount is a combination in which the first maximum attenuation section and the second maximum attenuation section are in a bypass state.
A signal source (2);
A level correction unit (3) for correcting a predetermined level of the signal from the signal source;
The high-frequency attenuation device according to claim 1, comprising the digital attenuator unit for inputting a signal from the level correction unit;
A level correction value storage unit (6) for storing correction data of the predetermined level for correcting an error of the digital attenuator unit;
For each combination of attenuation sections of the digital attenuator unit stored in the combination storage unit, the correction data calculated from the actual attenuation amount is calculated, and the level correction unit is determined according to the combination of each attenuation section. And a calculation control section (5) for varying the predetermined level correction.
The actual attenuation amount is an attenuation amount including an attenuation amount of each attenuation section of the digital attenuator unit and a mismatch loss between the attenuation sections.
The arithmetic control unit is
3. The signal generator according to claim 2, wherein an actual attenuation amount in each of a plurality of consecutive set attenuation amounts including the maximum set attenuation amount is obtained from at least three actual attenuation amounts, and the correction data is calculated. .

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