KR100405002B1 - Automatic calibration method of electric field strength meter - Google Patents

Abstract

The present invention relates to a method for automatically correcting a measurement level of a field strength meter, which allows to efficiently correct an error caused by a characteristic deviation of various components and circuits used in the field strength meter while simultaneously correcting a measurement error of the field strength meter. It is about.

The method for automatically correcting a measurement level of a field strength meter according to the present invention includes a first step of receiving a radio signal for correcting a measurement level in three different frequency bands and measuring the RSSI level of the field strength meter, and a center frequency band. by subtracting the RSSI level at the maximum and minimum frequencies in the RSSI level, the difference value (Δy _H) a second step to obtain the (Δy _L), the difference value (Δy _H) (Δy _L) a predetermined value in the ( After converting the transmission level below 0.5V), the third step of measuring the reception level of the FSM and the field strength meter, and the system correction equation is calculated according to the reception level of the FSM and the field strength meter, and based on the field strength A fourth step of adjusting and setting the level of the meter; a fifth step of measuring the reception level of the electric field strength meter and the ESM whose level is adjusted; and an absolute value of a difference value between the reception level of the field strength meter and the FSM; The sixth step of obtaining and the seventh step of fixing a correction parameter for correcting the measurement level when the absolute value of the difference value is lower than a predetermined value (1dB).

Therefore, according to the present invention, the overall gain / sensitivity of the field strength meter is compensated for by the gain variation of each component circuit such as the LNA, VCO, mixer, etc. of the field strength meter and the automatic gain correction of the antenna according to the frequency band is performed. Fluctuation correction can be performed at the same time.

Description

Automatic calibration method of electric field strength meter

The present invention relates to a method for automatically correcting a measurement level of an electric field strength meter, and more particularly, to correct an error caused by a characteristic deviation of various components and circuits used in the electric field strength meter while correcting a measurement error of the electric field strength meter. The present invention relates to a method for automatically calibrating a measurement level of an electric field strength measuring instrument that can be calibrated efficiently.

In addition, the present invention compensates the gain variation by each component of the LNA, VCO, mixer, etc. of the field strength meter, and performs an automatic gain correction of the antenna according to the frequency band, thereby changing the overall gain / sensitivity of the field strength meter. The present invention relates to a method for automatically correcting a measurement level of an electric field strength measuring instrument that enables simultaneous calibration.

Recently, due to the rapid growth of the mobile communication and wireless field, various corresponding RF measuring instruments have been developed.

In particular, the electric field strength measuring device is a device for measuring the electric field strength radiated from a wireless communication device such as a base station, a terminal, and is a measuring equipment used for wireless communication system design and A / S work. Since these RF measuring instruments play a role in determining the success or failure of the development and maintenance of new equipment or services, it is essential to secure measurement errors and reliability of the equipment.

As shown in FIG. 1, the field strength measuring instrument includes an antenna 1, an LNA (2: Low Noise Amplifier), a filter (3: filter), a mixer (4: mixer), and an IF amplifier (5: Intermediate Frequency Amp). And a RSSI (Radio Signal Strength Indicator) voltage sensing unit 6, VCO 7, PLL IC 8, control and display unit 9, and the like.

The electric field incident on the antenna 1 in the field strength meter is converted into an electrical signal by the antenna 1 having a gain of α dB at an operating frequency, amplified by the LNA 2 of gain β dB, and a loss of γ dB. After passing through the band pass filter 3, it is input to the mixer 4 having a conversion gain of δ dB.

The input signal is mixed with the oscillation signal oscillated by the VCO 7, converted into an intermediate frequency signal of 21.4 MHz, amplified by the IF amplifier 5, and applied to the RSSI voltage sensing unit 6. Accordingly, the RSSI voltage detector 6 extracts a RSSI (Radio Signal Strength Indicator) voltage from the amplified signal and provides it to the control and display unit 9.

At this time, the oscillation frequency provided from the VCO (7) ) Is determined by Equation 1 below.

here, Is the oscillation frequency, Is the measurement frequency.

Accordingly, the control and display unit 9 can display the reception electric field level when receiving the radio signal transmitted from the object to be measured.

However, it is necessary to measure not only the gain in each component of the above-mentioned electric field strength measuring device, but also the matching error from the impedance matching circuit connecting each component, and the characteristic error according to the change of operating frequency. The disadvantage is that each instrument has to undergo a complex calibration process.

An object of the present invention is to automatically measure the measurement level of the field strength measuring instrument to correct the error caused by the characteristic deviation of various components and circuits used in the field strength measuring instrument at the same time. To provide a correction method.

In addition, an object of the present invention is to compensate for the gain variation by each component of the LNA, VCO, mixer, etc. of the field strength meter, and to perform the automatic gain correction of the antenna according to the frequency band, thereby increasing the overall gain / An object of the present invention is to provide a method for automatically correcting a measurement level of an electric field strength meter, which can simultaneously perform a sensitivity fluctuation correction.

1 is a schematic diagram showing a general field strength measuring instrument.

2 is a schematic diagram showing a correction system for correcting a measurement level of an electric field strength meter.

3 is a graph showing a change state of the antenna gain according to the frequency band.

4 is a graph for explaining a correction method by the correction system according to the present invention.

5 is a flowchart illustrating a method for automatically correcting a measurement level of an electric field strength measuring device according to the present invention.

※ Explanation of code about main part of drawing ※

1, 300, 400: Antenna 2: LNA

3: filter 4: mixer

5: IF amplifier 6: RSSI voltage detector

7: VCO 8: PLL IC

9 control and display unit 100 flex encoder

200: SSG 500: field strength measuring instrument

600: FSM

In order to achieve the object as described above, the method for automatically calibrating the measurement level of an electric field strength measuring device is based on an intermediate frequency of the maximum frequency (x ₂ ), the center frequency (x ₀ ), and the minimum frequency (x ₁ ) of the radio signals within the measurement bandwidth. A first step of measuring an EFM RSSI (Electric Field Strength Meter Radio Signal Strength Indicator) level (y ₂ ) (y ₀ ) (y ₁ ) for automatic correction of the measurement level; The maximum frequency (x ₂₎ of the EFM RSSI level (y ₂₎ and the center frequency (x ₀₎ of the EFM RSSI level (y ₀₎ and EFM RSSI level (y ₁₎ and the center frequency of the lowest frequency (x ₁₎ (x ₀ difference EFM of the RSSI level (y ₀₎ of a) (Δy _H) (the second step to obtain the Δy _L); The difference value (Δy _H) (Δy _L) and EFM with a predetermined value the difference value to the contrast _{(0.5V) (Δy H) (} Δy L) a predetermined value (0.5V) or more, when the center frequency (x ₀₎ The difference between the RSSI level, the EFM RSSI level of the maximum frequency (x ₂ ), the EFM RSSI level of the center frequency (x ₀ ), and the EFM RSSI level of the minimum frequency (x ₁ ) and the EFM RSSI level of the center frequency (x ₀ ). A third step of storing the value Δy _H Δy _L as an error voltage; And when the center frequency (x ₀ ) is greater than the measurement frequency (x) in comparison to the center frequency (x ₀ ) and the measurement frequency (x), the measurement frequency (x) and the center frequency (x ₀ ) in Equation 2 below. And its EFM RSSI level (y ₀ ), its minimum frequency (x ₁ ) and its EFM RSSI level (y ₁ ), respectively, to obtain a compensation value (yy _O ) of the measurement frequency (x), and to obtain a center frequency (x _O ). Is smaller than the measurement frequency (x), the following equation (3) and the measurement frequency (x) and the center frequency (x _O ) and its EFM RSSI level (y _O ), the maximum frequency (x ₂ ) and its EFM RSSI level (y ₂ ) the fourth step of obtaining the compensation value (yy _O ) of the measurement frequency (x) by applying each of the steps, and by using the compensation value (yy _O ) characterized in that for automatically correcting the antenna measurement level in the frequency band used [Equation 2] [Equation 3]

As another embodiment of the method for automatically correcting the measurement level of the electric field strength meter according to the present invention, the measurement level is determined from an intermediate frequency of the maximum frequency (x ₂ ), the center frequency (x ₀ ), and the minimum frequency (x ₁ ) of the radio signals within the measurement bandwidth. A first step of measuring the EFM RSSI (Electric Field Strength Meter Radio Signal Strength Indicator) level (y ₂ ) (y ₀ ) (y ₁ ) for the automatic correction of; The maximum frequency (x ₂₎ of the EFM RSSI level (y ₂₎ and the center frequency (x ₀₎ of the EFM RSSI level (y ₀₎ and EFM RSSI level (y ₁₎ and the center frequency of the lowest frequency (x ₁₎ (x ₀₎ EFM RSSI level _(O y) and a difference (Δy _H) (the second step to obtain the Δy _L) of: wherein in case the difference value (Δy _H) (Δy _L) to a predetermined value (0.5V) When the difference value Δy _H (Δy _L ) is less than the predetermined value (0.5V), the measurement frequency (x) is set to the center frequency (x ₀ ), and the measurement frequency (x) whose transmission level is changed at 20dBm interval is transferred to the FSM. Measuring a received reception level and storing RSSI voltages received by the EFM at the same location, respectively; Applying the measured frequency and the RSSI voltage to Equations 5 to 8 below to obtain the characteristic curves of the reception level (dBm) of the FSM and the RSSI (V) of the EFM, and arrange them as shown in Equation 9 below. A fourth step of obtaining and storing a correction equation as shown in Equation 10 by substituting to A fifth step of measuring and setting the levels of the EFMs according to the correction equations, measuring the reception levels of the adjusted EFMs and the ESMs, and obtaining an absolute value for the difference between the respective reception levels; And a sixth step of repeatedly correcting the level of the EFM until the absolute value of the difference value is lower than a predetermined value (1 dB). It is characterized in that to correct the gain of the system by performing [Equation 5]. [Equation 6] [Equation 7] [Equation 8] [Equation 9] [Equation 10]

In another embodiment of the present invention, the method further includes converting the units of the measured RSSI level by an equation for converting the units.

Hereinafter, the configuration and operation according to an embodiment of the present invention will be described in more detail with an exemplary drawing.

2 is a measurement level correction system of an electric field strength measuring device configured to obtain data to be used for measurement level correction, and is composed of a flex encoder 100 (Flex Encoder), an SSG (200: Standard Signal Generator), an antenna 300, and the like. Transmission means for transmitting a radio signal for measuring the electric field strength is configured.

In addition, an electric field strength meter (500: electric field strength meter) requiring measurement level correction for receiving a radio signal transmitted from a transmission means and an FSM (600: calibration standard equipment used to obtain data for correction of measurement error) Field Strength Meter) is provided with an antenna 400.

At this time, the antenna 300 connected to the SSG 200 and the field strength meter 500 and the antenna 400 of the FSM 600 that receive the radio signal transmitted therefrom do not fall apart from each other by a predetermined distance (R, 30m). desirable.

In addition, the loss due to the transmission / reception cable used may be corrected together when the antenna gain is measured and corrected.

Of course, the electric field strength measuring device 500 for measuring the electric field strength by receiving the radio signal transmitted from the transmission means, as shown in Figure 1, the antenna 1, the LNA 2, the filter 3, the mixer 4 ), IF amplifier 5, RSSI voltage sensing section 6, VCO 7, PLL IC 8, control and display section 9, and the like.

The operation of the present invention configured as described above will be described with reference to Figs.

The method for automatically correcting the measurement level of the electric field strength meter according to the present invention will be described by dividing the gain correction of the antenna and the gain correction of the system.

First, the field strength measuring antenna mainly uses a dipole-type whip antenna and is designed to have a maximum gain at the center frequency of the field strength measuring frequency band. Therefore, it can be modeled that a gain change such as an inverse quadratic function occurs in a band other than the center frequency, as shown in FIG. As shown in Fig. 3, since the magnitude of gain change above and below the center frequency is small, it may be regarded as a first-order function in this region.

The gain correction method of the antenna using the test environment of FIG. 1 is as follows. The description here is based on the domestic paging frequency of 322 to 328.6 MHz.

First, the environment of the transmission means is set such that a radio signal having a transmission power of -20 dBm is transmitted from the transmission means, that is, the flex encoder 100, the SSG 200, the antenna 300, or the like (S51) (S52).

Then, the field strength meter 600 receives the RSSI level at the center frequency (325.3 MHz) and the lowest frequency (322 MHz) and the maximum frequency (328.6 MHz) in the service band (for example, 322 to 328.6 MHz). It is measured (S53). The RSSI level is subtracted from each of the measured frequencies (lowest, center, and maximum) (S54).

In other words, the RSSI level measured at the center frequency is subtracted from the RSSI level measured at the center frequency and ignored if the difference Δy _H (Δy _L ) is less than 0.5 V. The difference value Δy _H (Δy _L ) from the RSSI level at the frequency is stored as an error voltage.

In general, since the antenna has the maximum antenna gain, the compensation value of the measurement frequency can be calculated from Equations 2 to 4 below, where (x, y) represents the frequency and RSSI level at the measurement frequency ( S56).

I) When measured frequency <center frequency

Ii) In case of measuring frequency> center frequency

As an example, the calculation of the compensation value in the case of 327.00 MHz is as follows.

(RSSI compensation value)

Next, the actual field strength meter has a system error due to component circuit and component deviation, which is corrected by comparison with standard FSM measurements.

In the present invention, the automatic gain correction is performed for the deviation caused by the constituent circuit elements of the field strength meter (LNA (2), VCO (7), mixer 4, etc.) to correct the overall gain / sensitivity variation of the field strength meter. This can be done at the same time, which is conceptually illustrated in FIG.

As shown in Fig. 4, a slope error exists between the RSSI level and the FSM level of the field strength meter, and this is also corrected.

This system calibration first sets the measurement / calibration units (dBm, dBμV / M, μV / M, ...). The following description will be based on dBm.

An electric field strength measuring instrument and a correction system for system correction are configured as shown in FIG. 2, and the frequency is set around the measurement frequency (S57).

Then, the environment of the transmission means is set such that the radio signal having the transmission power is transmitted from the transmission means, that is, the flex encoder 100, the SSG 200, the antenna 300, and the like at 20 dBm intervals from 0 dBm to -40 dBm (S57). . At this time, the level received by the FSM 500, which is a calibration standard equipment, is recorded / stored. In addition, the field strength measuring unit 600 is located at the same point and the above process (S57) is repeated, and at this time, the received RSSI level is recorded / stored (S58).

Characteristic curves (straight lines) of the FSM 500 and the electric field strength measuring device 600 are calculated from the data obtained in the above process (S57) (S58). The characteristic curve may be calculated as shown in Equation 5 below.

If the slope is replaced by a _S , it is obtained as in Equation 6 below.

Therefore, the RSSI level V of the EFM 600 is equal to the following Equation (7).

If the slope is replaced by a _E again, as shown in Equation 8 below,

Becomes

Accordingly, the correction equation is calculated through the following relational expression (S59).

Equation (8) is summarized as in Equation (9) below.

Here, using the data measured by the electric field strength measuring device 600, x value can be obtained from the equation (9). Substituting the x value into Equation 5 and then arranging, y _S value can be obtained as shown in Equation 10 below.

The correction equation obtained through this process is input to the memory of the electric field strength measuring device 600 (S60).

Then, the environment of the transmission means is reset to transmit a radio signal having a transmission power of -20 dBm.

At this time, the reception level (correction) of the field strength measurement device 600 is read in the same state as the reception level (correction value) of the field strength measurement device 600, and it is checked whether there is a deviation (error) between the two values (S61) (S62). ).

Where deviation = If <1 dB, the measurement is terminated (S63). If the deviation is> 1 dB, the above steps (S58 to S61) are repeated until the result is satisfied.

Finally, when changing the measurement frequency and the measurement unit is converted using a unit conversion formula, that is, the following equations (11) to (14) (S64).

,

,

Equation 12, Equation 13, and Equation 14 below show conversion equations for conversion to other units when the measurement basic units are dBm, dBμV, and dBμV / m.

Therefore, according to the present invention, the measurement error of the field strength measuring instrument that needs to be corrected can be corrected in real time using the FSM, which is a calibrated standard equipment, and the gain deviation compensation by the circuit elements, the automatic gain correction for the antenna, and accordingly The effect is to simultaneously compensate for gain and characteristic variations across the field strength meter system.

Since the measurement level correction method according to the present invention is for the entire system, it is possible to further reduce the measurement error of the equipment compared to applying compensation for individual circuit elements, and also compensates according to the frequency band so that the reliability of the equipment for the desired frequency There is an effect to increase.

In particular, the application of the present invention has the advantage that even a gradual characteristic change and measurement error generated by using the equipment such as aging (aging) can be corrected.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the present invention, and such modifications and modifications belong to the appended claims.

Claims (3)

EFM RSSI (Electric Field Strength Meter Radio Signal Strength Indicator) level for automatic correction of the measurement level from the intermediate frequency of the maximum frequency (x ₂ ) and the center frequency (x ₀ ) and the minimum frequency (x ₁ ) of the radio signals within the measurement bandwidth. (y ₂ ) a first step of measuring (y ₀ ) (y ₁ ); The maximum frequency (x ₂₎ of the EFM RSSI level (y ₂₎ and the center frequency (x ₀₎ of the EFM RSSI level (y ₀₎ and EFM RSSI level (y ₁₎ and the center frequency of the lowest frequency (x ₁₎ (x Calculating a difference value Δy _H (Δy _L ) from the EFM RSSI level (y _O ) of ₀ ); The difference value (Δy _H) (Δy _L) and EFM with a predetermined value the difference value to the contrast _{(0.5V) (Δy H) (} Δy L) a predetermined value (0.5V) or more, when the center frequency (x ₀₎ The difference between the RSSI level, the EFM RSSI level of the maximum frequency (x ₂ ), the EFM RSSI level of the center frequency (x ₀ ), and the EFM RSSI level of the minimum frequency (x ₁ ) and the EFM RSSI level of the center frequency (x ₀ ). A third step of storing the value Δy _H Δy _L as an error voltage; And When the center frequency (x ₀ ) is greater than the measurement frequency (x) in contrast to the center frequency (x ₀ ) and the measurement frequency (x), the measurement frequency (x) and the center frequency (x ₀ ) and The EFM RSSI level (y ₀ ), the minimum frequency (x ₁ ) and its EFM RSSI level (y ₁ ) are applied respectively to obtain a compensation value (yy _O ) of the measurement frequency (x), and the center frequency (x _O ) is When the measurement frequency (x) is smaller than the measurement frequency (x), the measurement frequency (x) and the center frequency (x _O ) and its EFM RSSI level (y _O ), the maximum frequency (x ₂ ) and its EFM RSSI level (y ₂₎ ) Is applied to each other to obtain a compensation value (yy _O ) of the measurement frequency (x), thereby automatically correcting the antenna measurement level in the frequency band used by the compensation value (yy _O ). Automatic calibration of measuring level of strength measuring instrument. [Equation 2] [Equation 3] EFM RSSI (Electric Field Strength Meter Radio Signal Strength Indicator) level for automatic correction of the measurement level from the intermediate frequency of the maximum frequency (x ₂ ) and the center frequency (x ₀ ) and the minimum frequency (x ₁ ) of the radio signals within the measurement bandwidth. (y ₂ ) a first step of measuring (y ₀ ) (y ₁ ); The maximum frequency (x ₂₎ of the EFM RSSI level (y ₂₎ and the center frequency (x ₀₎ of the EFM RSSI level (y ₀₎ and EFM RSSI level (y ₁₎ and the center frequency of the lowest frequency (x ₁₎ (x Calculating a difference value Δy _H (Δy _L ) from the EFM RSSI level (y _O ) of ₀ ); The difference value (Δy _H) as below (Δy _L) to a predetermined value (0.5V) by the difference value (Δy _H) (Δy _L) a predetermined value (0.5V) than the center of the measuring frequency (x) frequency ( x ₀ ) and measuring the reception level received by the FSM at the measurement frequency (x) whose transmission level is changed at intervals of 20 dBm, and storing RSSI voltages received by the EFM at the same location, respectively; Applying the measured frequency and the RSSI voltage to Equations 5 to 8 below to obtain the characteristic curves of the reception level (dBm) of the FSM and the RSSI (V) of the EFM, and arrange them as shown in Equation 9 below. A fourth step of obtaining and storing a correction equation as shown in Equation 10 by substituting to A fifth step of measuring and setting the levels of the EFMs according to the correction equations, measuring the reception levels of the adjusted EFMs and the ESMs, and obtaining an absolute value for the difference between the respective reception levels; And A sixth step of repeatedly correcting the level of the EFM until the absolute value of the difference value is lower than a predetermined value (1 dB); Method for automatically correcting the measurement level of the electric field strength meter, characterized in that for correcting the gain of the system. [Equation 5] [Equation 6] [Equation 7] [Equation 8] [Equation 9] [Equation 10] The method of claim 2, The method of claim 1, further comprising the step of converting the unit of the measured RSSI level by the following equations (11) to (14) for converting the unit. [Equation 11] [Equation 12] [Equation 13] [Equation 14]