KR20000006905A - An apparatus for converting a frequecy with a dynamic filtering character - Google Patents

Abstract

PURPOSE: A device for transforming a frequency is provided to eliminate a noise existing in a corresponding channel and an interference formed by an adjacent channel for improving a telephone calling quality. CONSTITUTION: An interactive mobile communication trunk system being operated according to a multichannel frequency transforming method comprises: a frequency transformer(10) for transforming a high frequency signal inputted from the outside to a middle frequency signal and transiting variably the central frequency of the transformed middle frequency signal by a controlling signal for filtering and outputting the transient middle frequency signal; and a controller(20) being received a feedback of the middle frequency signal outputted from the frequency transformer for detecting an interference of an adjacent channel or a noise existing in a specific channel and outputting a controlling signal to the frequency transformer according to the location of the interference or the noise.

Description

An apparatus for converting a frequecy with a dynamic filtering character

The present invention relates to a frequency conversion device having a dynamic filtering characteristic used in a bidirectional mobile communication relay system performing a multi-channel communication service such as CDMA, GSM, WLL, IMT2000, FLIMTS, CT-2, TACS, TRS, and the like.

More specifically, when the frequency spectrum of the intermediate frequency signal according to the communication method is stored and the frequency spectrum of the intermediate frequency signal generated by the frequency converter deviates from the stored frequency spectrum, the center frequency of the intermediate frequency signal is shifted left and right to be filtered. The present invention relates to a frequency converter having dynamic filtering characteristics.

Currently, mobile communication providers use a repeater method using a variable wave, where a variable wave is used by different input / output frequencies to prevent oscillation between input and output. Therefore, in order to use the variable wave method, the possibility of oscillation is prevented by using an internal filter.

As described above, the repeater method using a variable wave is widely used in a bidirectional mobile communication system that performs communication services in multiple channels such as CDMA, GSM, WLL, IMT2000, FLIMTS, CT-2, TACS, TRS, and the like.

In order to maintain long-distance call quality in such bidirectional mobile communication, a frequency converter is generally used. A frequency converter is a method of converting an original signal form into a transmittable frequency band to remove noise generated in the conversion process. To do this, filtering is essential.

1 is a block diagram illustrating a frequency converter generally used in a bidirectional mobile communication relay system.

As shown in FIG. 1, a general frequency converter includes: first and second local oscillators LO1 and LO2 generating constant first and second oscillation frequencies; A band pass filter (BPF) for band-pass filtering the first mixer MIX1 and the first intermediate frequency signal by mixing an external input signal and the first oscillation frequency to generate a first intermediate frequency signal; And a second mixer MIX2 for mixing the first intermediate frequency signal and the second oscillation frequency filtered by the band pass filter BPF to output the final intermediate frequency signal.

As described above, the conventional frequency converter has a problem in that the filtering characteristics and the input / output characteristics are fixed, and thus, it is difficult to actively cope with the case where the noise to be used in the channel to be used is severe or the signal interference by the adjacent channel is severe.

Accordingly, the present invention has been made to solve the above problems, when the frequency spectrum of the intermediate frequency signal according to the communication method is stored and the frequency spectrum of the intermediate frequency signal generated by the frequency converter deviates from the stored frequency spectrum, It is an object of the present invention to provide a frequency converter having a dynamic filtering characteristic which is adapted to filter by shifting the center frequency of an intermediate frequency signal from side to side.

The apparatus according to the present invention for achieving the above object, in the bidirectional mobile communication relay system operated according to the multi-channel variable wave method, after converting the high-frequency signal input from the outside into the intermediate frequency signal and the converted intermediate frequency A frequency converter for varying the center frequency of the signal by a control signal and then filtering and outputting the shifted intermediate frequency signal; The controller is configured to detect a noise existing in a specific channel or interference of an adjacent channel by receiving an intermediate frequency signal output from the frequency converter and output a control signal to the frequency converter according to its position.

1 is a schematic block diagram illustrating a general frequency converter;

2 is a schematic block diagram illustrating a frequency converter having a dynamic filtering characteristic according to the present invention;

3 (a) is a waveform diagram of an output signal of a general frequency converter;

(b) is an output signal waveform diagram of a frequency converter having a dynamic filtering characteristic according to the present invention.

* Description of Signs of Main Parts of Drawings *

10: frequency converter 20: controller

21: Spectrum Analyzer 22: Learner

23: oscillation controller 24: alarm indicator

HPF: High Pass Filter LPF: Low Pass Filter

BPF 1,2: First and second band pass filter

MIX 1,2,3,4,5: 1,2,3,4,5 Mixer

LO 1,2,3,4,5: 1,2,3,4,5 local oscillators

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

2 is a schematic block diagram illustrating a frequency converter having a dynamic filtering characteristic according to the present invention.

As shown in FIG. 2, the present invention is a bidirectional mobile communication relay system operated according to a multi-channel variable wave method, and converts a high frequency signal input from the outside into an intermediate frequency signal and then converts the center frequency of the converted intermediate frequency signal into a center frequency signal. A frequency converter 10 variably shifting by a control signal and then filtering and outputting the shifted intermediate frequency signal; The controller 20 outputs a control signal to the frequency converter 10 according to its position by detecting the noise existing in a specific channel or interference of an adjacent channel by receiving an intermediate frequency signal output from the frequency converter 10. It is composed.

Here, the frequency converter 10 may include: first, second, third and fourth local oscillators (LO1, LO2, LO3, LO4) generating a predetermined oscillation frequency according to a control signal of the controller 20; A first mixer (MIX1) for converting a high frequency signal input from the outside into an intermediate frequency signal and simultaneously shifting the center frequency of the intermediate frequency signal to the left by the oscillation frequency generated by the first local oscillator (LO1); A first bandpass filter (BPF1) for filtering the intermediate frequency signal transitioned by the first mixer (MIX1); A second mixer (MIX2) for shifting the center frequency of the intermediate frequency signal filtered by the first bandpass filter BPF1 in the right direction by the oscillation frequency generated by the second local oscillator LO2; A second band pass filter (BPF2) for filtering the intermediate frequency signal transitioned from the second mixer (MIX2); A third mixer (MIX3) for shifting the center frequency of the intermediate frequency signal filtered by the second bandpass filter BPF2 by the oscillation frequency generated by the third local oscillator LO3; A band cancellation filter (BRF) for filtering the intermediate frequency signal transitioned by the third mixer (MIX3); And a fourth mixer (MIX4) for generating a desired variable wave by shifting the center frequency of the intermediate frequency signal filtered by the band erasure filter BRF by the oscillation frequency generated by the fourth local oscillator LO4. .

In addition, the controller 20, the spectrum analyzer 21 for analyzing the frequency spectrum of the intermediate frequency signal output from the frequency converter 10; A learner 22 for storing the frequency spectrum of the intermediate frequency signal according to the communication method, and comparing the frequency spectrum of the intermediate frequency signal analyzed by the spectrum analyzer 21 with the stored frequency spectrum; The oscillation controller 23 outputs a control signal to the first, second, third and fourth local oscillators LO1, LO2, LO3, and LO4 according to the comparison result of the learner 22.

Next, the operation and effects of the apparatus according to the present invention configured as described above will be described in detail.

As shown in FIG. 3 (a), noise JAM1 by another communication device is present in the channel FA2 of the intermediate frequency signal Fout output from the frequency converter 10 and adjacent channels FA1 and FA3. If there is interference by), the spectrum analyzer 21 first analyzes the frequency spectrum of the intermediate frequency signal Fout output from the frequency converter 10.

At this time, the learner 22 stores the frequency spectrum of the intermediate frequency signal according to the communication method, and compares the frequency spectrum of the intermediate frequency signal analyzed by the spectrum analyzer 21 with the stored frequency spectrum.

According to the comparison result of the learner 22, the oscillation controller 23 outputs control signals to the first, second, third, and fourth local oscillators LO1, LO2, LO3, and LO4, respectively. The 3,4 local oscillators LO1, LO2, LO3, and LO4 generate variable oscillation frequencies according to the control signals of the controller 20, respectively, to form the 1,2,3,4 mixers (MIX1, MIX2, MIX3, MIX4). )

In general, a mixer is a frequency in which two different frequencies (for example, f1 and f2) have a sum or difference of integer multiples of these two frequencies (for example, mf1 ± nf2, where m and n are integers). The first mixer MIX1 according to the present invention mixes the oscillation frequency of the external input frequency Fin and the first local oscillator LO1 to drop the input frequency Fin into the intermediate frequency band.

At this time, the oscillation frequency of the first local oscillator LO1 is determined by the control signal output from the oscillation controller 23, and the center frequency of the intermediate frequency signal is shifted left or right by the oscillation frequency. .

That is, the first mixer MIX1 converts the signal Fin input from the outside into an intermediate frequency signal and at the same time the center frequency of the intermediate frequency signal by the oscillation frequency generated by the first local oscillator LO1. ) And the first bandpass filter BPF1 filters the intermediate frequency signal transitioned from the first mixer MIX1.

In general, a band pass filter refers to a filter having a characteristic of passing a signal in a frequency band between two specific cutoff frequencies f1 and f2 and attenuating all signals in other frequency bands.

At this time, the center frequency of the intermediate frequency signal is filtered while being shifted slightly to the left from the center frequency of the first band pass filter BPF1, so that the left band of the intermediate frequency signal is further filtered as much as the transition.

On the other hand, since the above-described processing can filter only the interference signal by the left adjacent channel FA1, the center frequency of the intermediate frequency signal is shifted to the right to filter the interference signal of the remaining right adjacent channel FA3. You have to go through the process of filtering.

That is, the second mixer MIX2 shifts the center frequency of the intermediate frequency signal filtered by the first band pass filter BPF1 to the right direction by the oscillation frequency generated by the second local oscillator LO2.

The second band pass filter BPF2 filters the intermediate frequency signal transitioned from the second mixer MIX2.

Accordingly, the output signal of the second band pass filter BPF2 is completely separated from the interference of the left and right adjacent channels FA1 and FA3.

On the other hand, the above-described processing can completely remove the interference signal by the left and right adjacent channels (FA1, FA3), but can not remove the noise (JAM1) generated in the channel (FA2), the filtering method as follows Do it again.

That is, the third mixer MIX3 transitions the intermediate frequency of the intermediate frequency signal filtered by the second band pass filter BPF2 by the oscillation frequency generated by the third local oscillator LO3. At this time, the frequency of the noise JAM1 to be removed in the intermediate frequency signal is set as the center frequency.

The band cancellation filter BRF filters the intermediate frequency signal transitioned from the third mixer MIX3.

In general, a band rejection filter is a filter having a characteristic of attenuating signals in a frequency band between two specific cutoff frequencies f1 and f2 and passing all signals in other frequency bands. Also called Filter).

The fourth mixer MIX4 generates a desired variable wave by shifting the center frequency of the intermediate frequency signal filtered by the band cancellation filter BRF by the oscillation frequency generated by the fourth local oscillator LO4.

Accordingly, the intermediate frequency signal Fout output from the fourth mixer MIX4 is not only completely separated from the interference of the adjacent channels FA1 and FA3 as shown in FIG. 3 (b) but also the noise JAM1 in the corresponding channel FA2. It is also completely separated from).

In this case, the output signal of the frequency converter 10 may be transmitted to the controller 20 remotely by a coupler COUPLER.

In addition, the controller 20 further includes an indicator 24 to inform the user of the noise inflow or signal interference according to the comparison result of the learner 22.

If a plurality of noises (Jam) exist in the corresponding channel (FA2), by configuring the third local oscillator (LO3), the third mixer (MIX3) and the band cancellation filter (BRF) in multiple stages, the corresponding channel (FA2) It is possible to remove several noises present within.

As described above, the present invention provides an intermediate frequency according to a communication method in a bidirectional mobile communication relay system performing a communication service in multiple channels such as CDMA, GSM, WLL, IMT2000, FLIMTS, CT-2, TACS, and TRS. If the frequency spectrum of the intermediate frequency signal generated by the frequency converter is out of the stored frequency spectrum after memorizing the frequency spectrum of the signal, the center frequency of the intermediate frequency signal is shifted left and right to filter the noise. At the same time, interference formed by adjacent channels can be eliminated, thereby improving the call quality of the mobile communication system.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below It will be appreciated.

Claims (5)

In the bidirectional mobile communication relay system operating according to the multi-channel variable wave method, A frequency converter for converting a high frequency signal input from the outside into an intermediate frequency signal and variably shifting the center frequency of the converted intermediate frequency signal by a control signal, and then filtering and outputting the intermediate frequency signal to which the center frequency is shifted; And a controller for detecting a noise present in a specific channel or interference of an adjacent channel by receiving an intermediate frequency signal output from the frequency converter and outputting a control signal to the frequency converter according to its position. With frequency inverter. The method of claim 1 wherein the frequency converter, First, second, third, and fourth local oscillators for generating a predetermined oscillation frequency according to the control signal of the controller; A first mixer for converting a high frequency signal input from the outside into an intermediate frequency signal and simultaneously shifting the center frequency of the intermediate frequency signal by an oscillation frequency generated by the first local oscillator; A first bandpass filter for filtering the intermediate frequency signal transitioned by the first mixer; A second mixer for predetermined shifting the center frequency of the intermediate frequency signal filtered by the first bandpass filter by the oscillation frequency generated by the second local oscillator; A second band pass filter for filtering the intermediate frequency signal transitioned by the second mixer; A third mixer for predetermined shifting the center frequency of the intermediate frequency signal filtered by the second bandpass filter by the oscillation frequency generated by the third local oscillator; A band cancellation filter for filtering the intermediate frequency signal transitioned by the third mixer; And a fourth mixer configured to generate and output a desired variable wave by shifting the center frequency of the intermediate frequency signal filtered by the band erasure filter by the oscillation frequency generated by the fourth local oscillator. Inverter. The method of claim 2 wherein the controller is A spectrum analyzer for analyzing the frequency spectrum of the intermediate frequency signal finally output from the frequency converter; A learner for storing the frequency spectrum of the intermediate frequency signal according to the communication method, and comparing the frequency spectrum of the intermediate frequency signal analyzed by the spectrum analyzer with the stored frequency spectrum; And an oscillation controller configured to output a control signal to the first, second, third and fourth local oscillators according to a comparison result of the learner. According to claim 3, wherein the controller, And an indicator for notifying a user of noise inflow or signal interference according to a comparison result of the learner. The method of claim 1, And a coupler for delivering the output signal of the frequency converter to the controller remotely.