JP2001116779A - Wireless frequency monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically acquire calibration data by the minimum working of a worker in an RF monitor so as to calibrate the nonlinear output of a detector by the calibration data when the signal level of an RF signal is detected by using the detector. SOLUTION: A step variable attenuator 14 capable of varying and controlling an amount of attenuation by an instruction from CPU 2 in stages is provided in the front stage of a detector 18. When the calibration data Bn are stored in EEPROM 24, the calibration data Bn are automatically stored to EEPROM 24 by successively changing the amount of the attenuation of the step variable attenuator 14 in stages while the RF signal of a constant level is applied on the step variable attenuator 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal level (transmission / reception power) of a radio frequency signal transmitted / received by a radio communication device.
A radio frequency (RF) monitor for monitoring the

[0002]

2. Description of the Related Art Radio frequencies (R
F) Convert the signal into a DC analog signal using a detector,
Signal level (voltage or current value) of this DC analog signal
There is known an RF monitor that monitors the transmission / reception power of a wireless communication device by detecting and displaying on a display device. In this type of RF monitor, a detector used to convert an RF signal into a DC analog signal has non-linear characteristics, so that it is not possible to accurately detect transmission / reception power before the detector is used.

Therefore, the inventor of the present invention has previously calibrated the measured value by linearly approximating the measured value based on the DC analog voltage or current value output from the detector using the calibration data. Monitor was proposed (Japanese Patent Application No.
095615). FIG. 1 shows the configuration of this RF monitor. In this RF monitor, an RF signal transmitted and received by the wireless communication device is input to a detector 7 and converted into a DC analog monitor voltage. This DC analog monitor voltage is A
/ D converter 1 The CPU 2 outputs a control signal a
Controls the A / D converter 1 to convert the DC analog monitor voltage into a digital signal and output it as a digital monitor signal b. Digital monitor signal b output
Are stored in the RAM 3 via the data bus based on the designated address of the CPU 2. The CPU 2 takes out the digital monitor signal c from the RAM 3 and inputs it to the calibration processing circuit 5 composed of a ROM. The calibration processing circuit 5 uses the calibration table data d stored in the calibration data storage EEPROM 4 and performs calibration processing using the data d as a reference monitor value. The calibration processing value e output from the calibration processing circuit 5 is C
Display 6 consisting of LCD display etc. by PU2
And the monitor value is displayed.

FIG. 4 shows an example of a table of calibration data stored in the EEPROM 4. In this calibration table, the range up to the full scale of the monitor is equally divided into an arbitrary number of sections, n calibration points are provided, and calibration data is set for each calibration point. In the table of FIG.
Represents a calibration point number (n = 0, 1, 2,... N), and An
Represents the true value of the input signal at the calibration point n, and Bn represents An
Is the calibration data (output value of the converter) corresponding to
Vn represents transmission / reception power (for example, watt) corresponding to the input signal An.

The storage of calibration data in the EEPROM 4 is performed by an operator in the following procedure. That is, the operator first causes the display 6 to display the calibration table shown in FIG. 4 and selects Bn corresponding to the calibration point number n to be input. Bn
Is selected by moving the cursor to the calibration point number n using the numeric keypad 8 provided on the display 6 and pressing the "ENTER" key. With this selection, the RF monitor will
It is in a state of waiting for input of n. Next, the operator generates an RF signal of transmission / reception power corresponding to the display value Vn using an external signal generator such as a reference measuring device, and inputs the RF signal to the detector 7. The output of the detector is converted into a digital signal by the A / D converter 1, and the digital signal is stored in the RAM as a digital monitor signal b.
3 is stored. Next, by pressing the “execute” key with the ten keys 8, the digital monitor signal b is stored in the RAM.
The value stored in 3 is stored in EEPROM 4 as Bn. Thus, the data Bn for the calibration point of the number n
Is completed, Bn is stored for the calibration point of the number n-1 by the same operation. The above operation needs to be sequentially performed for n calibration points.

[0006]

In this RF monitor, it is necessary to prepare calibration data for a large number of calibration points in order to perform a monitor display with a small error and high accuracy. R proposed in Japanese Patent Application No. 10-095615
The problem with the F monitor is that when the calibration data Bn is stored in the EEPROM from the A / D converter, the operator sets the level of the RF input signal using an external signal generator for each calibration point, and sets the corresponding calibration data. Must be entered each time. As a result, in order to store the calibration data for a large number of calibration points in order to improve the accuracy of monitor display, the number of operations and the amount of work of the operator significantly increase, and a large amount of time is required for the calibration data storage operation. .

Another problem with the RF monitor is that it becomes impossible to measure when the signal level of the RF signal to be monitored exceeds the full scale range of the RF monitor. To deal with this problem, a complicated circuit is required.

It is therefore an object of the present invention to improve the above-mentioned RF monitor and to provide an RF monitor capable of automatically acquiring a large amount of calibration data and easily storing it in a calibration table. It is another object of the present invention to provide an RF monitor capable of effectively measuring even when the signal level of an input RF signal becomes excessive.

[0009]

An RF monitor according to the present invention comprises:
A programmable control means (CPU), a step variable attenuator for stepwise attenuating an input radio frequency signal according to a command of the control means, and outputting an attenuated radio frequency signal; Detector for converting a frequency output signal into a DC analog monitor signal, A / D conversion means for converting a signal level of the DC analog monitor signal output from the detector into a digital value, and calibration for calibrating the digital value A calibration data storage unit for storing data (Bn in FIG. 5) for a plurality of calibration points in accordance with a command from the control unit, and calibrating the digital value based on the calibration data in response to a command from the control unit A calibration processing unit that outputs a calibration value; and a display unit that displays a calibration value corresponding to the input radio frequency signal. The control means, when storing the calibration data in the calibration data storage means,
The output value (Bn) of the A / D conversion means is calibrated for each calibration point while the attenuation of the step variable attenuator is changed stepwise while an input radio frequency signal of a constant level is applied to the step variable attenuator. It is programmed to store as data.

As described above, since the RF monitor of the present invention is provided with the step variable attenuator in the preceding stage of the detector, the amount of attenuation can be variably controlled stepwise by a command from the control means. Therefore, when the calibration data is stored in the calibration data storage means, the calibration data is stored by changing the attenuation of the step variable attenuator stepwise while applying a constant level input radio frequency signal to the step variable attenuator. It can be automatically stored in the calibration data storage means. Therefore, the calibration data storage process is speeded up and a large amount of hexadecimal number calibration data is easily obtained, so that the interval between calibration points can be subdivided, and an ultra-high-precision RF monitor can be realized. . Further, since the operator does not need to perform any operation other than inputting the reference RF signal from the outside, operability and maintainability are improved.

In a preferred embodiment, the minimum attenuation of the step variable attenuator can be arbitrarily changed. With this configuration, when the signal level of the input RF signal exceeds the appropriate input range of the detector, the signal level input to the detector is adjusted to an appropriate range by increasing or decreasing the attenuation of the step variable attenuator. Can be.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2, a radio frequency monitor (RF monitor) 10 of the present invention comprises a central processing unit (CPU) 12 comprising a microprocessor circuit for controlling the entire RF monitor, and A step variable attenuator 14 capable of variably controlling the amount of attenuation according to a digital control signal; and converting a control signal g from the CPU 12 into a control signal h in a signal form that the step variable attenuator 14 can process. An input / output interface 16 for outputting to the variable attenuator 14, a detector 18 for converting an RF signal output from the step variable attenuator 14 to a DC analog monitor voltage, and a detector 1 in accordance with a control signal a of the CPU 12.
A / D converter 20 that performs analog-to-digital conversion (A / D conversion) of the DC analog monitor voltage output from the A / D converter 8 into a digital monitor signal, and a RAM (random number) that temporarily stores the digital monitor signal b output from the A / D converter 20 Access memory) 22. The RF monitor 10 also includes an EEPROM (Electrically Erasable Programmable Read Only Memory) 24 for storing calibration data,
Digital monitor signal c read from M22 is EEP
A display 30 such as a liquid crystal display having a calibration processing circuit 26 for performing a calibration process based on the calibration data d read from the ROM 24 and a keyboard 28 including ten keys and an execution key, and displaying a calibrated digital monitor signal e; It has.

The EEPROM 24 has a calibration table shown in FIG.
Bull is stored. In the calibration table of FIG.
n is an arbitrary number n of the full scale measurement range of the RF monitor 10.
The calibration point numbers (n = 0,
1, 2,... N). The maximum value of the calibration point n is A / D
Hexadecimal digital value bits output by converter 20
Determined by number. Of the output digital value of the A / D converter 20
When the number of bits is X, the maximum value of the calibration point n is 2 to the power of X.
Become. An is the step variable attenuator 1 for the calibration point n.
4 to the input analog RF signal applied to the detector 18
This is the true value (decimal number) of the signal level. Bn is A / D
Calibration for use in calibrating the nonlinear output of converter 20
An A / D converter corresponding to the input signal An
Actual output value of the data 20 (hexadecimal data indicated by the suffix h)
). The calibration data Bn is stored in the CPU in a manner described later.
Stored in EEPROM 24 in advance by automatic input by 12
Is done. Vn is transmission / reception power (W) corresponding to the input signal An.
). Dn is the attenuation of the step variable attenuator 14
And the set value D at which the amount of attenuation is maximized ₀And minimum attenuation
Set value D to be (zero)_nIs a value obtained by equally dividing
You. Minimum attenuation D_nIs the input RF signal, as described below.
Is changed by the operator when exceeds the proper input range of the detector
be able to.

Calibration data Bn in the calibration table of FIG.
Is executed in advance by the following procedure in accordance with an instruction from the operator.
2 is automatically stored in the EEPROM 24. EE
The input of Bn to the PROM 24 includes the step variable attenuator 14, the detector 18, the A / D converter 20, the RAM 22
Done through. In order to explain the procedure of storing the calibration data Bn with reference to the flowchart of FIG. 6 and FIG. 2, a process (steps S01 to S03) to be described later for changing the attenuation of the step variable attenuator is skipped.
R corresponding to the full-scale RF input An as an input signal
The F signal is set by manual operation of an external signal generator such as a reference measuring device, and is applied to the step variable attenuator 14 (step S04). Thereafter, until the storage of Bn is completed, the signal level of the RF input signal applied to the step variable attenuator 14 is kept constant without changing,
The automatic storage operation of the calibration data Bn is started by automatically and variably controlling the attenuation amount of the step variable attenuator 14 by the CPU 12.

First, the CPU 12 reduces the amount of attenuation Dn of the step variable attenuator 14 to a minimum value D via control signals g and h.
_n (zero) (step S05), and outputs the full-scale input RF signal to the detector 18 without attenuating (step S06). The detector 18 converts the input RF signal into a DC analog monitor voltage and outputs the same to the A / D converter 20. The CPU 12 sends the control signal a to the A / D converter 20 to convert and output the analog monitor voltage into a hexadecimal digital value (step S07) and temporarily store the same in the RAM 22 (step S08). The CPU 12 further sends the temporarily stored hexadecimal digital value to the EEPROM 24 as the calibration data signal f, and the full scale RF input A
EEPRO as hexadecimal calibration data Bn corresponding to n
It is stored in M24 (steps S09, S10).

After the calibration data Bn corresponding to the full-scale RF input An has been stored, the hexadecimal calibration data Bn corresponding to the RF input An (A _{1 to} An _-1 ) less than the full scale is next stored. (B _{1 to} B _n−1 ) are sequentially and automatically stored. For example, to store calibration data _{B 1} corresponding to the RF input _{A 1} is, CPU 12 is a control signal g
And controlling the step variable attenuator 14 through the h, to convert the input RF signal to hexadecimal digital value is inputted to the detector 18 after being attenuated on the basis of the attenuation D _1,
Hexadecimal digital values A / D converter 20 outputs is stored in the calibration data _{B 1} as EEPROM 24.
The CPU 12 further performs the above operations on the calibration data B _{2 to} B
Repeatedly for _n-1 (steps S06 to S10
Repeat). When the storage of Bn has been completed for all the calibration points n (step S11), the calibration data storage processing ends. Calibration data B ₀ is allowed to store in advance as a fixed value the minimum value capable of output of the A / D converter 20.

Next, the normal measurement operation of the RF monitor 10 will be described with reference to the flowchart of FIG. 7 and FIG. Unless there is a request for updating the calibration data Dn (step S27), the CPU 12 repeats the processing of steps S21 to S26 in the flowchart of FIG. 7 to detect and display the transmission / reception power of the input RF signal. More specifically, the CPU 12
First, the attenuation of the step variable attenuator 14 is set to the minimum value D
_The step variable attenuator 14 is controlled to set _n (zero) (step S21). It outputs a control signal g according to the attenuation D _n at full scale output interface 16, step variable attenuator step variable attenuator 14 is converted into a control signal h processable form 14
The output is output to Since the attenuation of the step variable attenuator 14 is set to the minimum value D _n (zero) in this manner, the input RF signal is input to the detector 18 without being attenuated, and is converted into a DC analog monitor voltage. . The DC analog monitor voltage output from the detector 18 is A
/ D converter 20. Next, the CPU 12 outputs the control signal a to the A / D converter 20, converts the DC analog voltage into a digital signal, and outputs it as a hexadecimal digital monitor signal b (step S22). CP
U12 designates a storage location (address) in the RAM 22, and temporarily stores the digital monitor signal b output from the A / D converter 20 in the RAM 22 (step S2).
3). The CPU 12 causes the A / D converter 20 to execute hexadecimal digital value conversion at regular time intervals, and
To update the stored data. The calibration calculation process is performed on the data temporarily stored in the RAM 22 (step S24).

In the calibration calculation process (step S24), C
The PU 12 first activates the calibration processing circuit 26 (Step S241). The calibration processing circuit 26 detects a calibration point section of the input data (step S242), performs a calibration calculation (step S243), and outputs a calibration processing value (step S244). In the detection of the calibration point section of the input data (step S242), the CPU 12 extracts the data stored in the RAM 22 (the hexadecimal output value of the A / D converter 20) from the RAM 22 as a digital monitor signal c and inputs it to the calibration processing circuit 26. The calibration processing circuit 26 is an EEPROM
The calibration data Bn of the calibration table (FIG. 5) stored in 24 is taken out as a signal d and used, and the calibration process is performed using this as a reference value. The calibration processing circuit 26 compares the input digital monitor signal c with Bn and calculates which calibration point the data of the digital monitor signal is located between.

When the position P of the digital monitor signal data is n <
When P <n + 1, the calibration output value M is calculated based on the following equation. _{M = A n + {( "} C" d- "B n" d) / ( "B n + 1" d- "B n" d)} × {(A n + 1) -A n} ··· ( Equation 1) In the equation, C represents the value of the digital monitor signal c stored in the RAM 22 (actual hexadecimal output of the A / D converter 20), and "" d represents a numerical value converted from a hexadecimal number to a decimal number.

Calculating based on Equation 1, the calibration output value M
Is linearly approximated in the calculated calibration point section. An example of linear approximation is shown in the graph of FIG. In FIG. 3, data An (or Bn) at each calibration point n corresponds to the transmission / reception power Vn, the solid curve represents the actual output of the A / D converter 20, and the dashed line represents the calibration output value calculated based on Equation 1. Represent. As can be seen from the solid curve in FIG. 3, the detector 18 has a non-linear output characteristic. In the example of FIG. 3, the position P of the digital monitor signal data c is located between the calibration points n = 1 and n = 2. The actual hexadecimal output of the A / D converter 20 is C, and the point P on the solid curve corresponding to the hexadecimal output C is linearly approximated by the point M on the broken line, and the nonlinear output of the detector is approximately Calibrated. The true value of the transmission / reception power at point P is _VP , and the calibration output value at point M is V _P
M. The difference between the point P and M (V M _{-V P)} is meter error, it is possible to determine the calibration point and calibration points for the required meter error. By dividing the interval between the calibration points and increasing the number of calibration points in a large amount, it is possible to display a monitor value with extremely high accuracy.

The CPU 12 performs a calibration calculation process (step S2).
ASCII code conversion is performed to display the calibration processing value M obtained in the calibration processing circuit 26 and output from the calibration processing circuit 26 on the display 30 (step S25), and the converted calibration processing value is used as a monitor value by the signal e to display the LCD. Display 3
0 and display (step S26). If there is no request for updating the calibration data after the display control (step S27),
The CPU 12 returns to step S22. If there is an update request, the process exits the routine of the flowchart of FIG. 7 and shifts to the calibration data update process of the flowchart of FIG.

Next, the operation for updating the attenuation amount data in the calibration table will be described. The attenuation Dn of the step variable attenuator 14 stored in the EEPROM 24 is set such that, when the input RF signal to be monitored exceeds the appropriate input range of the detector 18, the input power range input to the detector is set to an appropriate range. Can be changed to adjust. Referring to the flowchart of FIG. 6, firstly, it is displayed on the display unit 30 the data at the time of full-scale n of the calibration table shown in FIG. 5, to determine the necessity of the attenuation D _n at full scale operator (Step S01). Attenuation D _n at the time of full scale, the minimum set value of the step variable attenuator 14, an input-during normal monitoring and monitor calibration values
Also used for changes.

The level of the RF signal input to the detector 18 is
If the level exceeds the appropriate level or decreases extremely,
Attenuation D at full scale_nNeed to be updated. So
In the case of (1), the operator operates the
Cursor by D _nMove up and numeric keypad
New D by 28_nEnter the value and press the “ENTER” key.
Press to confirm. Press the “Execute” key again.
With the new D_nIs stored in the EEPROM 24
(Step S02). CPU 12 has a new D_nAnd the original D
_n, And calculate each D₀~ D_n-1Add to or subtract from
By calculating₀~ D_n-1Is automatically updated and EEP
It is stored in the ROM 24 (step S03). Then new
Large attenuation D_nFrom step S04 to step S1
1 is performed as described above, and all calibration points n
Then, Bn is updated. In subsequent measurements, steps are possible
The variable attenuator 14 has a new attenuation D_nBased on the input RF signal
The signal is attenuated and output to the detector 18,
The input level to be input is maintained in an appropriate range.

Although a specific embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications and changes can be made. For example, the input / output interface 16 can be replaced with a D / A converter, and the step variable attenuator 14 can be replaced with a voltage-controlled PIN diode variable attenuator.

[0025]

The first effect of the present invention is that an ultra-high precision RF
That is, the monitor can be easily realized. The reason is that the calibration data Bn can be automatically acquired and stored, so that a large amount of calibration data can be used and the calibration point interval can be subdivided. The second effect of the present invention is that the calibration data B
n memory work time can be greatly reduced,
This means that maintainability is improved. The reason is that the calibration data Bn is automatically stored only by the operator inputting the RF input signal corresponding to the full scale display value. A third effect of the present invention is that effective measurement can be performed even when the signal level of an input RF signal becomes excessive. The reason is that the input power range input to the detector can be adjusted to an appropriate range by changing the attenuation Dn of the step variable attenuator. Another advantage of the present invention is that it is highly versatile. The reason is that the calibration point and the calibration data of the data stored in the calibration data storage circuit can be freely set.

[Brief description of the drawings]

FIG. 1 is a block diagram of an RF monitor according to an earlier proposal of the present inventors.

FIG. 2 is a block diagram of an RF monitor according to the present invention.

FIG. 3 is a graph illustrating an example of linear approximation.

FIG. 4 shows an example of a description of a calibration table of the RF monitor shown in FIG. 1;

FIG. 5 shows an example of a description of a calibration table of the RF monitor of the present invention.

FIG. 6 is a flowchart showing a data storage / update mode of a calibration table in the RF monitor of the present invention.

FIG. 7 is a flowchart showing an operation in a measurement mode of the RF monitor of the present invention.

[Explanation of symbols]

 10: RF monitor 12: Control means (CPU) 14: Step variable attenuator 18: Detector 20: A / D converter 24: Calibration data storage means (EEPROM) 26: Calibration processing means 30: Display means (liquid crystal display)

Claims (5)

[Claims] 1. A programmable control means, and a step variable attenuator for attenuating an input radio frequency signal according to a command of the control means and outputting an attenuated radio frequency signal;
A detector for converting a radio frequency output signal of the variable attenuator into a DC analog monitor signal, A / D converting means for converting a signal level of the DC analog monitor signal output from the detector into a digital value, and the digital value Calibration data storage means for storing calibration data for calibrating a plurality of calibration points in accordance with a command of the control means, and calibrating the digital value based on the calibration data in response to a command of the control means A calibration processing unit that outputs a calibration value; and a display unit that displays a calibration value corresponding to the input radio frequency signal, wherein the control unit is configured to store the calibration data in the calibration data storage unit at a certain level. With the input radio frequency signal applied to the step variable attenuator, the attenuation of the step variable attenuator is changed stepwise for each of the calibration points. A radio frequency monitor which is programmed to store an output value of the A / D conversion means as the calibration data for each of the calibration points. 2. A radio frequency monitor according to claim 1, wherein said calibration processing means calibrates an output digital value of said A / D conversion means by linear approximation. 3. The radio frequency monitor according to claim 1, wherein the minimum attenuation of the step variable attenuator is changeable. 4. The radio frequency monitor according to claim 3, wherein the minimum attenuation of the step variable attenuator is increased when the signal level of the input radio frequency signal exceeds a proper input range of the detector. . 5. A radio frequency monitor according to claim 1, wherein said calibration data storage means comprises an electrically erasable programmable read only memory element.