KR100704625B1 - Method and apparatus for searching Radio Frequency channel - Google Patents

Abstract

A wireless channel search method and apparatus are provided.

In accordance with another aspect of the present invention, a wireless channel search apparatus includes a mixer for mixing a local frequency initialized by a local oscillator and a received signal, a band pass filter for filtering the mixed signal, and a digital signal for the filtered signal. An FFT module for executing an FFT, based on a result of the FFT, searching for a channel having a signal magnitude greater than or equal to a threshold value lasting longer than a reference time and based on a frequency having a signal magnitude greater than or equal to the threshold value in the searched channel; And a detection module for calculating a center frequency for the channel, and a channel filter for filtering the channel corresponding to the center frequency.

Radio Frequency Channel Discovery, Critical Value, Fast Fourier Transform

Description

Method and apparatus for searching for radio channels {Method and apparatus for searching Radio Frequency channel}

1 is a block diagram illustrating a configuration of a wireless signal receiver in a conventional wireless telephone.

2 is a flowchart illustrating a channel search process performed by a conventional wireless signal receiver.

3 is a block diagram illustrating a channel search apparatus according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a channel search process according to an embodiment of the present invention.

5 illustrates data of a frequency domain FFT processed by an FFT module in a channel search apparatus according to an exemplary embodiment of the present invention.

FIG. 6 is a diagram for describing a method of finding a center frequency of a channel having a magnitude greater than or equal to a threshold value in a channel search apparatus according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

330: RF front end 301: antenna unit

302: first-order filter 303: amplifier

304: second-order filter 305: mixer

306: 3rd order filter 307: AD converter

340: baseband 308: FFT module

309 detection module 310 channel filter

311: demodulation unit

The present invention relates to a method and apparatus for searching for a wireless channel, and more particularly, to a method and apparatus for quickly searching for a channel in a wireless telephone.

1 is a block diagram illustrating a configuration of a receiver in a conventional wireless telephone. As shown in FIG. 1, the receiver 100 of the conventional wireless telephone is largely composed of an RF front end and a base band.

First, the RF front end receives a signal passing through an antenna 101 for receiving a radio signal, a primary band filter 102 for processing a radio signal received by the antenna, and a primary band filter 102. An amplifier 103 for amplifying, a second band filter 104 for processing a signal output from the amplifier 103, and a local oscillator for generating a local frequency according to a control signal of a controller ), A third-order band filter which processes a signal output from the mixer 105 and a mixer 105 for mixing the signal output from the amplifier 103 and the local frequency generated by the local oscillator 109 (mixer 105). 106).

Next, the base band detects the white noise level of the received signal and detects the presence or absence of a signal according to the detection result of the detector 107 and the detector 107. The controller 108 is configured to control the demodulator 110 to demodulate the signal output from or to control the local oscillator 109 so that another local frequency is generated.

2 is a flowchart illustrating a channel searching process at a receiving unit of a conventional wireless telephone including the above components.

First, the controller 108 sets an initial channel to start channel search (S220). For example, reset the channel number to zero.

Next, in order to generate a local frequency that matches the set channel frequency, the local oscillator 109 locks the channel frequency using a phase locked loop (S230).

When the local frequency is generated, the channel region is down converted by mixing and filtering the received signal and the local frequency (S240).

After the down conversion is performed, the detector 107 detects whether the white noise level of the down-converted signal is higher than or equal to a predetermined level, thereby determining whether the signal is detected in the corresponding channel (S250).

As a result of the determination, when there is no signal in the corresponding channel, the controller 108 changes the local frequency of the local oscillator 109 and searches for another channel (S230).

As a result of determining whether there is a signal in the corresponding channel, if there is a signal in the corresponding channel, the controller 108 controls the demodulator 110 so that the signal of the corresponding channel can be demodulated (S260).

As described above, in the conventional channel search method, the controller 108 determines a channel to check for the presence of a signal, and then controls the local oscillator 109 to obtain a frequency of the corresponding channel to detect a local frequency (Locking). Do this.

However, as in the related art, when the frequency is locked by controlling the local oscillator 109, when a phase locked loop is used to lock the frequency, a time corresponding to a lock time is obtained. This takes a problem of lowering the communication environment. For example, if there are 40 channels that can be received by the cordless telephone and the time taken to lock the reception frequency on the cordless telephone is 30ms, it takes 1.2 seconds only to lock the frequency to search all 40 channels. do. In other words, except for the time required to determine the presence of a signal by checking the white noise level (White Noise Level), it takes more than 1 second to search all 40 channels.

Also, the receiver as shown in FIG. 1 may be manufactured by software having the same structure. In the design of the detector 107, the FFT and the FFT may be used to detect a white noise level of a frequency band corresponding to one channel. After performing the same operation, it is necessary to repeat the operation of adjusting the frequency of the local oscillator 109 again according to the operation result.

Since the operation of not only the local oscillator 109 but also the detector 107 must be repeated as many as the number of channels, this operation has a problem of using a large amount of computing resources of the software with time delay.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a channel search method and apparatus for faster channel search by using a fast fourier transform (FFT) and a center frequency tracking algorithm.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a wireless channel searching apparatus according to an exemplary embodiment of the present invention includes a mixer for mixing a local frequency initialized by a local oscillator and a received signal, a band pass filter for filtering the mixed signal, and a filter for the filtered signal. An FFT module that receives a digital signal and executes an FFT, and searches for a channel having a signal magnitude greater than or equal to a threshold lasting for a reference time based on a result of the FFT, and having a signal magnitude greater than or equal to the threshold in the searched channel. And a detection module for calculating a center frequency for the found channel, and a channel filter for filtering a channel corresponding to the center frequency.

In order to achieve the above object, the wireless channel search method according to an embodiment of the present invention, mixing the received local frequency and the received signal, filtering the mixed signal, converting the filtered signal into a digital signal Performing an FFT, searching for a channel having a signal magnitude greater than or equal to a threshold value based on the FFT data for more than a reference time, based on a frequency having a signal magnitude greater than or equal to the threshold value in the searched channel. Calculating a center frequency for the channel, and filtering a channel corresponding to the center frequency.

Specific details of other embodiments are included in the detailed description and drawings, and the advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete and common knowledge in the technical field to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

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

3 is a block diagram illustrating a channel search apparatus according to an exemplary embodiment of the present invention. Referring to this, the components and functions of the channel search apparatus according to an embodiment of the present invention will be described.

As shown in FIG. 3, the channel search apparatus according to the embodiment of the present invention includes an RF front end 330 and a base band 340.

First, the RF front end 330 amplifies a radio signal received through the antenna 301 and converts it into an intermediate frequency (IF). The antenna unit 301, the primary band filter 302, and the amplifier 303, secondary band filter 304, local oscillator 312, mixer 305, tertiary band filter 306, and AD converter 307.

The antenna unit 301 receives the radio signal and provides it to the primary band filter 302.

The primary band filter 302 filters the signal received through the antenna unit 301 and provides it to the amplifier 303.

The amplifier 303 amplifies the signal provided by the primary band filter 302 and provides the amplified signal to the secondary band filter 304.

The secondary band filter 304 processes the signal output from the amplifier 303 and provides it to the mixer 305.

The local oscillator 312 generates a local frequency, so that it can be mixed with the signal output from the secondary band filter 304.

A mixer 305 mixes the local frequency generated by the local oscillator 312 and the signal output from the secondary band filter 304.

The third-order band filter 306 filters the signal output from the mixer 305 and outputs the intermediate frequency IF. The intermediate frequency output from the tertiary band filter 306 is input to the AD converter 307. In addition, the frequency band width of the tertiary band filter 306 preferably includes all channel regions of the wireless telephone. That is, if the radiotelephone can receive 40 channels, it has a bandwidth for 40 channels.

The analog to digital converter 307 receives an intermediate frequency from the tertiary band filter 306 and converts the intermediate frequency into a digital signal.

The base band portion 340 includes a channel filter 310, an FFT module 308, a detection module 309, and a demodulation module 311. The base band may be implemented in hardware or software but is preferably implemented in software.

The FFT module 308 is a part that performs FFT on the digital data generated by the AD converter 307. At this time, the FFT is collectively performed on all receivable channels of the wireless telephone. For example, if the wireless telephone can receive 40 channels, the FFT module 307 performs FFT on these 40 channels in batch. In addition, the frequency resolution required to perform the FFT is software adjustable.

The detector module 309 searches for the signal over the entire area based on the result value of the FFT module 308. In other words, it is determined whether a signal exists. When determining the presence or absence of a signal, it can be known by searching whether a signal having a magnitude greater than or equal to a predetermined threshold value exists.

In this way, the presence or absence of a signal having a magnitude greater than or equal to a threshold value is detected based on the result value of the FFT module 308, and the detection module 309 detects that a signal having a magnitude greater than or equal to the threshold value is for a predetermined time. Determine if it persists. As a result of determination, when a signal having a magnitude greater than or equal to a threshold value lasts for a predetermined time or more, the detection module 309 finds a center frequency of the corresponding signal. The center frequency information is provided to the panel filter 310. The detection module 309 may be implemented in hardware or software, but is preferably implemented in software.

When the center frequency is found by the detection module 309, the channel filter 310 filters only the signal of the channel corresponding to the center frequency and provides the filtered signal to the demodulator 311.

The demodulator module 311 demodulates the channel signal passed by the channel filter 310.

4 is a flowchart illustrating a channel search process performed in a wireless channel search apparatus including the above components. Referring to this, a wireless channel search method according to an embodiment of the present invention will be described.

Initially, the local oscillator 312 is initialized. In other words, local frequency locking is performed based on the channel frequency for channel 0 (S410).

When the local oscillator 312 is initialized, the mixer 305 mixes the signal output from the secondary band pass filter 303 and the local frequency and switches downward (S420). The signal down-converted through the mixer 305, that is, the intermediate frequency (IF) signal, is provided to the AD converter 307 through the third-order band filter 306. At this time, the tertiary band filter 306 preferably has a bandwidth in a range that can include all channels of the wireless telephone.

Thereafter, the AD converter 307 converts the input analog signal into a digital signal (S430). When converting an analog signal into a digital signal, the sampling frequency is preferably at least two times the input frequency according to the Nyquist Theory. For example, when a signal having an intermediate frequency IF of 1 MHz is input and converted into a digital signal, 30,000 samples / sec are generated every second by sampling at 3M samples / sec.

When the digital samples are generated by the AD converter 307 as described above, the FFT module 308 converts the digital signal of the time domain generated by the AD converter 307 into a signal of the frequency domain. Convert (S440). For example, in the aforementioned example, when 3K bit FFT processing is performed on data sampled at 3M samples / sec, data of a frequency band having a frequency resolution of 1 KHz can be obtained. More specifically, with a frequency range of 25KHz per channel, if the frequency resolution is 1KHz, you can get 25 data per channel, and if the total number of channels in the cordless phone is 40, then 1000 for all 40 channels. Data of the corresponding frequency band can be obtained. (Because the bandwidth of the tertiary band filter has a bandwidth that can cover the frequencies of all channels, the FFT module performs FFT on all channels.) The number of bits in the FFT process Can be changed to

Thereafter, the detection module 309 searches for a channel whose signal magnitude is greater than or equal to a threshold based on the data generated by the FFT module 308 (S450). For example, when a part of the signal FFT processed by the FFT module 308 is as shown in FIG. 5, a channel having a magnitude greater than or equal to the threshold 501 is searched for.

As a result of the search, when a channel having a size greater than or equal to the threshold 501 is searched as shown in 502, it is determined whether a signal of the corresponding channel lasts longer than a reference time (S460). At this time, the duration of the signal can be measured using a loop count. For example, when the reference time is 30ms, the signal of the corresponding channel is checked every 5ms to check whether the signal is detected six times in succession in the corresponding channel. As a result of the check, when the signal is confirmed six times in a row, it is determined that the signal of the corresponding channel lasts more than the reference time.

When the signal of the channel 502 having a magnitude greater than or equal to the threshold value 501 is maintained for more than a reference time (S460, YES), the detection module 309 calculates the center frequency of the corresponding channel (S470). At this time, the center frequency of the channel can be found using the FM frequency characteristics used in the wireless telephone.

More specifically, the FM frequency has a symmetrical frequency component on the basis of a carrier frequency, which can be used to find the center frequency for the corresponding channel.

For example, in the data illustrated in FIG. 6, for channel 14, data between points 601 to 602 is continuously above the threshold 501. In this case, the average value of the frequency of the point 601 where the magnitude of the signal begins to cross the threshold 501 and the frequency of the point 602 where the magnitude of the signal begins to fall below the threshold 501 is obtained. This average value can be determined as the center frequency 603.

When the channel with the signal is searched and the center frequency 603 of the searched channel is determined, the channel filter 310 is set as the corresponding channel (S480), and the channel with the signal is filtered. The signal filtered by the channel filter 310 is provided to the demodulator 311.

Thereafter, the demodulator 311 causes the input signal to be demodulated (S490).

Although the wireless channel search method and apparatus according to the present invention have been described with reference to the drawings illustrated as above, the present invention is not limited by the embodiments and drawings disclosed herein, and the technical scope of the present invention. Of course, various modifications can be made by those skilled in the art.

As described above, the method and apparatus for searching for a wireless channel according to the present invention have one or more of the following effects.

First, when searching a channel of a wireless telephone, signal searching can be performed on all channels collectively, thereby reducing the time required for channel searching.

Second, there is an advantage that the delay time and the use of computing resources caused by locking the channel for each channel and performing the FFT can be reduced.

Third, since the value of the frequency resolution can be adjusted by software during FFT, the channel search performance and the amount of calculation can be mutually adjusted by using a frequency resolution suitable for a wireless communication environment.

Claims (5)

A mixer for mixing the received signal with the local frequency initialized in the local oscillator; A band pass filter for filtering the mixed signal; An FFT module configured to receive a digital signal for the filtered signal and perform an FFT; Based on the result of the FFT, searching for a channel whose signal magnitude is greater than or equal to a threshold value lasts longer than a reference time, and calculating a center frequency for the searched channel based on a frequency having a signal magnitude greater than or equal to the threshold value in the searched channel. A detection module; And And a channel filter for filtering a channel corresponding to the center frequency. The method of claim 1, wherein the center frequency is, And a mean value of a frequency of a point at which a signal magnitude is greater than or equal to the threshold and a frequency of a point at which a signal magnitude is less than or equal to the threshold value in the searched channel. Mixing the received local frequency with the received signal and filtering the mixed signal; Converting the filtered signal into a digital signal to perform an FFT; Searching for a channel having a signal magnitude greater than or equal to a threshold value lasting longer than a reference time based on the FFT data; Calculating a center frequency for the found channel based on a frequency having a signal magnitude above the threshold in the found channel; And And filtering the channel corresponding to the center frequency. The method of claim 3, wherein the searching comprises: And determining whether a signal magnitude greater than or equal to the threshold value lasts longer than the reference time by using a loop count. The method of claim 3, wherein the center frequency, And a mean value of a frequency of a point at which a signal magnitude is greater than or equal to the threshold and a frequency of a point at which a signal magnitude is less than or equal to the threshold value in the searched channel.

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