KR100643938B1 - The measurement apparatus of carrier frequency of AM modulating signal - Google Patents

Abstract

The present invention relates to the measurement of the radio wave quality, and the conventional apparatus measures the peak power by the resolution of the spectrum and the data scattered on the spectral screen, where the peak value of the accumulated power on the screen is found. If a frequency with a strong power is generated around the carrier frequency at any moment, it is difficult to find the correct carrier frequency.

Accordingly, the present invention is used in broadcasting and communication while determining whether or not the carrier frequency is a licensed frequency through a circuit for accurately finding the carrier frequency of AM broadcast signals, and measuring how much frequency bias has occurred at the licensed frequency. An apparatus for measuring carrier frequency of an AM modulated signal that can be used to measure frequency accuracy is provided.

Description

The measurement apparatus of carrier frequency of AM modulating signal

1 is a block circuit diagram of carrier frequency measurement using a conventional spectrum.

2 is a waveform diagram of a spectrum applied conventionally.

3 is a block diagram of an apparatus for measuring carrier frequency of an AM modulated signal according to one embodiment of the present invention;

Figure 4 is a signal waveform diagram of each component configured in the AM modulated signal carrier frequency measuring device according to an embodiment of the present invention.

Figure 5 is a waveform diagram of the output signal of the ADC in one embodiment of the present invention.

6 is a flowchart for finding a carrier frequency input to an ADC using digital data in a DSP according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: filter bank section 20: first mixer

30: 1st filter intermediate frequency part 40: 2nd mixer

50: second filter intermediate frequency section 60: third mixer

70: third filter intermediate frequency unit 80: analog-to-digital converter

90: DS

The present invention relates to radio wave quality measurement, and in particular, to find a carrier frequency of AM broadcast signals to determine whether or not it is an authorized frequency, and to measure how much frequency bias has occurred in an allowed frequency. A carrier frequency measurement apparatus for AM modulated signals.

1 and 2, the conventional AM modulated signal carrier frequency measuring device amplifies a signal input to the antenna ANT in the amplifier 1 and then outputs it to the spectrum analyzer 2. ,

The spectrum analyzer 2 analyzes the signal amplified and input, and shows the spectrum and power of the signal input on the screen.

In this case, a method for finding a carrier frequency of an AM signal input on the spectrum is performed as follows.

That is, after adjusting the span according to the measurement range in the menu of the spectrum analyzer 2, the power of the input signal is accumulated using the maximum hold menu.

Subsequently, the peak power of the accumulated power is found using a marker, and then the frequency corresponding to the peak power is determined as the carrier frequency.

However, the conventional device measures the peak power by the resolution of the spectrum and the data scattered on the spectral screen, where the peak value of the accumulated power on the screen is found. When a frequency with a strong power is generated in the surroundings, it is difficult to find an accurate carrier frequency.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to determine whether or not a carrier frequency is a licensed frequency through a circuit that accurately finds carrier frequencies of AM broadcast signals, and permits. An object of the present invention is to provide a carrier frequency measuring device for an AM modulated signal, which can be used to measure the accuracy of frequencies used in broadcasting and communication while measuring how much frequency deviation occurs at a given frequency.

In order to achieve the above object, the carrier frequency measuring device of the AM modulated signal according to the present invention comprises: a filter bank unit for switching according to the frequency of the AM modulated signal input through the antenna;

 A first mixer for mixing and controlling the frequency of the controlled 1st LO signal and the frequency of the AM modulated signal inputted from the switching of the filter bank unit;

 A first filter intermediate frequency unit outputting a frequency obtained by first down-converting the frequencies of the signals mixed and output from the first mixer;

 A second mixer for mixing and outputting a frequency of the signal output from the first filter intermediate frequency unit with a frequency of a fixed 2nd LO signal;                     

 A second filter intermediate frequency unit for outputting a frequency obtained by secondly down-converting the frequencies of the signals mixed and output from the second mixer;

 A third mixer (60) for mixing and outputting the frequency of the signal output from the second filter intermediate frequency unit with the frequency of the fixed 3rd LO signal;

 A third filter intermediate frequency unit configured to output a frequency obtained by third-order down-converting the frequencies of signals mixed and output from the third mixer;

 An analog-to-digital converter (ADC) for sampling the signal output from the third filter intermediate frequency unit and converting the sampled analog frequency signal into digital;

  A DSP for finding a carrier frequency input to the ADC using a signal converted from the ADC into a digital signal and calculating a carrier frequency of an AM modulated signal received at an antenna; Its features are to include.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a block diagram of an apparatus for measuring a carrier frequency of an AM modulated signal according to an embodiment of the present invention, and FIG. 4 is a signal waveform diagram of each component of an AM modulated signal carrier frequency measuring device according to an embodiment of the present invention. 5 is an output signal waveform diagram of an ADC according to an embodiment of the present invention.

3 to 5, a filter bank unit 10 for switching according to the frequency (Fi) of the AM modulated signal input through the antenna (ANT);                     

A first mixer (20) for mixing and controlling the frequency (F _L01 ) of the controlled 1st LO signal and the frequency (Fi) of the AM modulated signal input from the switching of the filter bank unit (10);

A first filter intermediate frequency unit 30 outputting a frequency (F1 = Fi-F _L01 ) in which the frequency of the signal mixed and output from the first mixer 20 is first down-converted;

A second mixer 40 for mixing the frequency F1 of the signal output from the first filter intermediate frequency unit 30 with the frequency F _L02 of the fixed 2nd LO signal;

A second filter intermediate frequency unit (50) for outputting a frequency (F2 = F1-F _L02 ) obtained by second-down converting the frequency of the signal mixed and output from the second mixer (40);

A third mixer (60) for mixing the frequency (F2) of the signal output from the second filter intermediate frequency unit (50) with the frequency (F _L03 ) of the fixed 3rd LO signal;

A third filter intermediate frequency unit (70) for outputting a frequency (F3 = F2-F _L03 ) in which the frequency of the signal mixed and output from the third mixer (60) is third-order down-converted;

An analog-to-digital converter (ADC) 80 for sampling the signal output from the third filter intermediate frequency unit 70 and converting the sampled analog frequency signal into digital;

DSP which finds a carrier frequency input to the ADC 80 using the digitally converted signal from the ADC 80 and calculates a carrier frequency of an AM modulated signal received at the antenna ANT (DSP) ( 90); It consists of.

Here, the sampling frequency in the ADC 80 should be at least two times higher than the carrier frequency of the AM modulated signal input to the ADC 80 expected to find the carrier frequency, but much more than two times to find a more accurate frequency. It is preferable that the sampling is performed at a large frequency, and in the present invention, a sampling frequency of about 10 times higher than the input carrier frequency to the ADC 80 can find an accurate carrier frequency.

Referring to the operation of the embodiment of the present invention configured as described above with reference to Figures 3 to 6 as follows.

In a method of finding a carrier frequency in an AM modulated signal input through an antenna ANT, first, the following setting is made to receive an AM broadcast signal that is being broadcast.

That is, the filter bank unit 10 is switched according to the frequency Fi of the AM modulated signal input through the antenna ANT.

Then, the AM modulated signal received through the antenna ANT according to the switching of the filter bank unit 10 is input to the first mixer 20, in which the 1st LO signal is controlled to the first mixer 20. The frequency of F _L01 is input,

In the first mixer 20, the frequency F _L01 of the 1st LO signal and the frequency Fi of the AM modulated signal input from the switching of the filter bank unit 10 are mixed, and then the first filter intermediate frequency unit is mixed. Output to (30).

In this case, the first filter intermediate frequency unit 30 performs a first down conversion to a frequency capable of processing the frequency of the signal mixed and output from the first mixer 20 by the ADC 80 and then down converts the same. The outputted frequency (F1 = Fi-F _L01 ) to the second mixer 40.

In the second mixer 40, the frequency F1 of the signal output from the first filter intermediate frequency unit 30 is mixed with the fixed frequency 2F of the LO signal F _L02 and then the second filter. Output to the intermediate frequency unit 50,

In the second filter intermediate frequency unit 50, the frequency of the signal mixed and output from the second mixer 40 is second down-converted to a frequency that can be processed by the ADC 80 and then the down-converted frequency. (F2 = F1-F _L02 ) is output to the third mixer 60.

Then, in the third mixer 60, the frequency F2 of the signal output from the second filter unit 50 is mixed with the frequency F _L03 of the fixed 3rd LO signal and then the third filter intermediate frequency. The output to the unit 70,

The third filter intermediate frequency unit 70 downconverts the frequency of the signal mixed and output from the third mixer 60 to a frequency that can be processed by the ADC 80 and then downconverts the frequency. (F3 = F2-F _L03 ) is output to the ADC80.

At this time, the ADC 80 samples the signal output from the third filter unit 70, converts the sampled analog frequency signal into digital, and outputs the converted digital signal to the DSP 90. do.

Accordingly, the DSP 90 finds a carrier frequency input to the ADC 80 by using the digitally converted signal from the ADC 80 and then calculates a carrier frequency of an AM modulated signal received by the antenna ANT. You can do it.

In other words, if the output form of the digital data of the ADC 80 is made as shown in Table 1,

Input signal strength   Digital data      Dmax   1111 1111 1111     Dmax-1   1111 1111 1110      ‥‥       ‥‥        0   1000 1000 1000      ‥‥       ‥‥     Dmin + 1   0000 0000 0001      Dmin   0000 0000 0000

In the process of finding the carrier frequency input to the ADC 80 by the DSP 90, as shown in FIG. 6, first N digital data corresponding to one second of time are input.

After that, the reference data (0. 1000 0000 0000) is designated, and the size of the reference data and the n-th data are compared.

When the counter X is found by finding a point that changes from 0111 1111 1111 to 1000 0000 0000, the counter X becomes F3, which is a carrier frequency input to the ADC 80.

Here, the carrier frequency of the AM modulated signal received by the antenna ANT can be calculated using the carrier frequency F3 input to the ADC 80 found by the DSP 90. The carrier frequency of the AM signal is It is calculated as F1 + F2 + F3.

As described above, the present invention determines whether or not the carrier frequency is a licensed frequency through a circuit for accurately finding carrier frequencies of AM broadcast signals, and measures how much frequency bias has occurred at the licensed frequency. It provides an effect that can be used to measure the accuracy of the frequencies used in the system.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Claims (1)

A filter bank unit configured to switch according to a frequency of an AM modulated signal input through an antenna; A first mixer for mixing and controlling the frequency of the controlled 1st LO signal and the frequency of the AM modulated signal inputted from the switching of the filter bank unit; A first filter intermediate frequency unit outputting a frequency obtained by first down-converting the frequencies of the signals mixed and output from the first mixer; A second mixer for mixing and outputting a frequency of the signal output from the first filter intermediate frequency unit with a frequency of a fixed 2nd LO signal; A second filter intermediate frequency unit for outputting a frequency obtained by secondly down-converting the frequencies of the signals mixed and output from the second mixer; A third mixer (60) for mixing and outputting the frequency of the signal output from the second filter intermediate frequency unit with the frequency of the fixed 3rd LO signal; A third filter intermediate frequency unit configured to output a frequency obtained by third-order down-converting the frequencies of signals mixed and output from the third mixer; An analog-to-digital converter (ADC) for sampling the signal output from the third filter intermediate frequency unit and converting the sampled analog frequency signal into digital; A DSP for finding a carrier frequency input to the ADC using a signal converted from the ADC into a digital signal and calculating a carrier frequency of an AM modulated signal received at an antenna; Carrier frequency measurement apparatus of the AM modulated signal, characterized in that consisting of.

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