JPH021952Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention corrects the frequency characteristics of a programmable attenuator, especially for the attenuation amount set independently of the frequency characteristics, with a correction value corresponding to each set operating frequency. The present invention relates to a highly accurate programmable attenuator in which a high attenuation amount can be set.

One of the main functions of an attenuator is the attenuation accuracy (error), which is specified as ±0.3dB up to 500MHz, and the attenuation of the programmable attenuator is within the specified value for the set attenuation. will be produced in This method of regulation represents the allowable range for each set attenuation amount. The operating frequencies of programmable attenuators vary widely from direct current to high frequencies, and although the actual attenuation is within the specified value above, the operating frequency may vary due to the frequency characteristics. The amount of attenuation varies depending on the Therefore, it is desired to realize a programmable attenuator with higher attenuation accuracy for the frequency used.

This invention was made in consideration of the above points,
It is an object of the present invention to provide a programmable attenuator that corrects a set attenuation amount depending on the frequency used and takes frequency characteristics into consideration. The present invention will be described below with reference to the drawings.

Fig. 1 shows the configuration of an embodiment of the programmable attenuator of the present invention, Fig. 2 is an explanatory diagram of the contents of the frequency characteristic memory in which frequency characteristic correction values are stored, and Fig. 3 shows how to calculate the interpolated value. The explanatory diagram, FIG. 4, shows a flowchart.

In FIG. 1, numeral 1 is a variable attenuator and includes a plurality of attenuators, for example, 80, 40,
20, 10dB attenuators and 8, 4, 2, 1dB
each attenuator and correction 0.8, 0.4, 0.2,
Each 0.1 dB attenuator is directly connected to each other. Whether the attenuation amount of each attenuator is inserted or set to the through side is determined by an instruction from the variable attenuator control circuit 2 according to the attenuation amount set in the attenuation amount setting circuit 3. The attenuation setting circuit 3 has a desired integer value of attenuation set externally, that is, the settable attenuators of 80, 40, 20, and 10 dB and the attenuators of 8, 4, 2, and 1 dB. The attenuation amount to be set is inputted, and the frequency to be used is set to the frequency setting circuit 4.

The frequency characteristic memory 5 stores frequency characteristic correction values for each attenuation amount obtained as follows. That is, a certain nominal attenuation amount X _i of the variable attenuator 1 (the nominal attenuation amount shown on the display etc.),
For example, for X _i =30 dB, the frequency characteristic curve is obtained by experiment at a certain frequency interval from DC ₀ to the maximum usable frequency _nax . From this _, each correction value _{S i at} each frequency ₀ , ₁ , ₂ , . In this way, the nominal attenuation X _i is 1 dB from 0 dB to the maximum attenuation X _nax dB set for variable attenuator 1.
The above frequency characteristic curves for each step attenuation are determined through experiments. Then, a correction value at each frequency ₀ , ₁ , ₂ , ... _nax is determined for each attenuation amount, and the nominal attenuation amount set in the attenuation amount setting circuit 3 is stored in the frequency characteristic memory 5 as shown in FIG.
address X _i direction, and use frequencies ₀ , _{1 , 2} , . _. .

The correction data readout circuit 6 is connected to the attenuation amount setting circuit 3.
Based on the value of the attenuation amount set in , and the value of the usage frequency set in the frequency setting circuit 4, the correction value of the attenuation amount for the usage frequency is read out from the frequency characteristic memory 5 described above. The value of the attenuation amount set in the attenuation amount setting circuit 3 specifies the address X _i of the frequency characteristic memory 5, and the value of the usage frequency set in the frequency setting circuit 4 specifies the address Y _i of the frequency characteristic memory 5.
Specify. Here, since an integer value is input as the value of the attenuation amount set in the attenuation amount setting circuit 3, the address X _i of the frequency characteristic memory 5 must be specified, but the value of the used frequency set in the frequency setting circuit 4 are stored at certain frequency intervals due to the capacity of the frequency characteristic memory 5, there may be cases where the address Y _i of the frequency characteristic memory 5 cannot be designated. In this case, two addresses Y _i and Y _i+1 with frequencies close to the value of the operating frequency set in the frequency setting circuit 4 are used.
and. That is, when the attenuation value set in the attenuation amount setting circuit 3 and the usage frequency value set in the frequency setting circuit 4 correspond to the address of the frequency characteristic memory 5, the correction data readout circuit 6 Read the frequency characteristic memory 5 at address X _i Y _i . Further, when the attenuation amount value set in the attenuation amount setting circuit 3 and the use frequency value set in the frequency setting circuit 4 do not correspond to the address of the frequency characteristic memory 5, the correction data readout circuit 6 The frequency characteristic memory 5 is read out using the two addresses X _i Y _i and X _i Y _i+1 described above.

In the calculation means 7, when there is only one correction value read out from the frequency characteristic memory 5, that correction value is output without being calculated, but when two correction values are read out from the frequency characteristic memory 5, the next correction value is outputted. Performs interpolation calculations and outputs the calculation results. That is, when the correction value S _i when the frequency characteristic memory 5 is read out at the address X _i Y _i and the correction value S i ₊₁ when the frequency characteristic memory 5 is read out at the address X _i Y _i+1 , As shown in Figure 3, two points ( _i , S _i ),
A predetermined straight line passing through ( _i+1 , S _i+1 ) or 2
A correction value S for the operating frequency _k set in the frequency setting circuit 4 is calculated from an interpolation curve such as the following curve. Then, the calculated correction value S is calculated by the calculation means 7.
is output from.

The attenuator attenuation amount correction means 8 includes the calculation means 7
This circuit outputs a corrected attenuation value to the variable attenuator control circuit 2 based on the correction value S output from the attenuation amount setting circuit 3 and the value of the attenuation amount set in the attenuation amount setting circuit 3. The attenuation amount set to 3 is corrected by the correction value S. As a result, the attenuation amount of the variable attenuator control circuit 2 for the variable attenuator 1 is finally set.

Note that the correction value S output from the calculation means 7 is sent to the display device 9, and the correction amount (value) for the set usage frequency is displayed.

The variable attenuator control means 12 includes the variable attenuator control circuit 2 described above and the attenuator attenuation amount correction means 8.

Next, the operation shown in FIG. 1 will be explained using the flow chart shown in FIG.

When a desired nominal attenuation, for example 30 dB, is set externally, this 30 dB is set in the attenuation setting circuit 3 (step 41). Frequency used from outside,
For example, assume that 10MHz is set. This 10M
Hz is set in frequency setting circuit 4 (step 4)
2). Attenuation 30dB set in attenuation setting circuit 3
and the operating frequency 10M set in frequency setting circuit 4.
Hz, the correction data reading circuit 6 generates an address for accessing the frequency characteristic memory 5 (step 43). When the address generated by this correction data reading circuit 6 corresponds to the address of the frequency characteristic memory 5 shown in FIG. 2, the frequency characteristic memory 5 is accessed with the address,
The correction value S _i is read from the frequency characteristic memory 5 (steps 44 and 46). This read correction value S _i is
switch 1 without being interpolated by calculation means 7.
0 to the attenuator attenuation amount correction means 8 as a correction amount S (=S _i ) (step 47).
Then, the variable attenuator 1 is controlled by the variable attenuator control circuit 2.
The attenuator in the attenuator is operated to correct the nominal attenuation amount of 30 dB set in the attenuation amount setting circuit 3 by the amount of correction S (step 48).

On the other hand, when the address generated by the correction data reading circuit 6 does not correspond to the address of the frequency characteristic memory 5, for example, when the desired attenuation amount is 30 dB and the frequency used is 30 MHz, the temporary address generated by the correction data reading circuit 6 Two similar addresses are created. In other words, as shown in Figure 2, the address X _i with an attenuation of 30 dB and a working frequency of 10 MHz
Y _i and an address X _i Y _i+1 with an attenuation of 30 dB and a frequency of 50 MHz are created. The correction data reading circuit 6 accesses the frequency characteristic memory 5 using these two addresses (step 45), and obtains the correction value S _i read from the frequency characteristic memory 5 at the address X _i Y _i and the address X _i Y _i+1 . The correction value S _i+1 read from the frequency characteristic memory 5 is sent to the calculation means 7. The calculation means 7 calculates the two sent correction values Si and S _i+1
and from address X _i Y _i and address X _i Y _i+1 , the third
The two points ( _i , S _i ) and ( _i+1 , S _i+1 ) shown in the figure are found ( _i = 10MHz, _i+1 = 50MHz), and as explained above, the two points ( _i , S _i ), (( _i+1 , S _i+1 ), the correction amount S for the operating frequency of 30 MHz is calculated by interpolation calculation based on a predetermined interpolation curve passing through (( i+1 , S i+1 ) (step 49). S is input to the attenuator attenuation amount correction means 8 (step 4).
7) The variable attenuator control circuit 2 corrects the set attenuation amount by the correction amount S (step 4).
8).

In this way, the attenuation amount set regardless of the frequency characteristics is corrected according to the set frequency of use, either directly or with a value obtained by interpolation calculation, and a more accurate attenuation amount is automatically set. The correction value S is then displayed on the display device 9 and output to the outside.

The switch 10 is normally used in the on state, but depending on the set operating frequency, the variable attenuator 1
It is used in the off state when there is no need to correct the nominal attenuation amount set in . At this time, the input (correction amount S) to the attenuator attenuation amount correction means 8 becomes zero. The display device 9 also displays how much error the nominal attenuation amount set in the variable attenuator 1 has with respect to the set usage frequency, and the error, that is, the correction amount S described above is displayed. Output to the outside.

Note that the frequency characteristic memory 5 stores frequency characteristic correction values for each attenuation amount, but instead of these correction values, the frequency characteristic values themselves are stored, and the variable attenuator 1 is set. You can also do that.

As described above, according to the present invention, a programmable attenuator is realized in which the attenuation amount is automatically set in accordance with the set operating frequency, that is, a programmable attenuator with even higher attenuation accuracy. If no correction is made to the used frequency, the amount of error included in the set nominal attenuation amount at the set used frequency is displayed on a display device or can be output externally. Therefore, you can know immediately even if you do not have the data sheet at hand. Also, the error at any frequency can be immediately obtained.

[Brief explanation of the drawing]

Fig. 1 shows the configuration of an embodiment of the programmable attenuator of the present invention, Fig. 2 is an explanatory diagram of the contents of the frequency characteristic memory in which frequency characteristic correction values are stored, and Fig. 3 shows how to calculate the interpolated value. The explanatory diagram, FIG. 4, shows a flowchart. In the figure, 1 is a variable attenuator, 2 is a variable attenuator control circuit, 3 is an attenuation amount setting circuit, 4 is a frequency setting circuit,
5 is a frequency characteristic memory, 6 is a correction data reading circuit, 7 is a calculation means, 8 is an attenuator attenuation amount correction means, 9 is a display device, 10 is a switch, and 12 is a variable attenuator control means.

Claims (1)

[Scope of utility model registration request] a variable attenuator 1 for obtaining a desired amount of attenuation by combining a plurality of attenuators; an attenuation amount setting circuit 3 for setting a desired amount of attenuation from the outside; a frequency setting circuit 4 for setting a frequency; A frequency characteristic memory 5 stores correction data of the amount of attenuation with respect to the frequency of the frequency characteristic memory 5; a correction data reading circuit 6 for reading out desired correction data that has been read out; a calculation means 7 that calculates an attenuation correction value for the frequency based on the attenuation correction data read from the frequency characteristic memory 5; A programmable attenuator comprising variable attenuator control means 12 for controlling the attenuation amount of the variable attenuator 1 so that the attenuation amount of the variable attenuator 1 becomes the true value based on the correction value calculated by the means 7.