KR102159535B1 - Multi-band Wi-Fi Access Point which removes sideband noise - Google Patents

Abstract

A multi-band Wi-Fi access point is provided that can prevent performance degradation due to mutual interference between bands. The multi-band Wi-Fi access point of the present invention includes an antenna; An N frequency duplexer connected to the antenna to separate the N frequency signals; N RF switches having a common terminal respectively connected to one of the N terminals of the N frequency duplexer, and a first terminal and a second terminal selectively connected to the common terminal; N WiFi transceivers; N power amplifiers having input terminals connected to output terminals of the N Wi-Fi transceivers, and output terminals connected to the first terminals of the N RF switches; N low noise amplifiers having input terminals connected to the second terminals of the N RF switches and output terminals connected to input terminals of the N Wi-Fi transceivers, respectively; A reference signal obtained by combining an RF reception signal of a Wi-Fi access point including sideband noise output to the N low-noise amplifiers and an RF transmission signal from other channels is received, and the sideband noise is removed from the Wi-Fi access point. N noise cancellers respectively outputting RF received signals to the input terminals of the N WiFi transceivers are provided. According to the present invention, since sideband noise of a Wi-Fi signal input to a receiving end of a Wi-Fi transceiver is removed, interference does not occur in a receiving channel.

Description

Multi-band Wi-Fi Access Point which removes sideband noise}

The present invention relates to a multi-band Wi-Fi access point, and more particularly, to a multi-band Wi-Fi access point capable of preventing performance degradation due to mutual interference between bands.

A Wi-Fi Access Point is a device that enables wireless devices to be connected to wired devices using a related standard using Wi-Fi. Most Wi-Fi technologies today are based on the IEEE 802.11 standard and are widely used due to ease of installation. In particular, as the number of users connecting to the wireless Internet using smartphones or laptop computers is increasing rapidly, not only general households, but also commercial facilities such as coffee shops, hospitals, public institutions, and companies are providing a Wi-Fi environment. The demand for

Wi-Fi access points are often more expensive to install than the equipment itself. Accordingly, in order to reduce installation cost and overcome the limitations of the installation location, a type of increasing service capacity by supporting multiple Wi-Fi bands at one access point is preferred. For example, using two 5GHz bands, it can be compared to changing a single-decker bus to a double-decker bus.

In the Wi-Fi access point, various RF signals are used according to standard standards such as IEEE 802.11a, IEEE 802.11b, IEEE 802.11n, IEEE 802.11ac, and IEEE 802.11ax, but the following is a typical 802.11b signal for convenience of explanation. Explained as.

In general, Wi-Fi access points largely use OFDM (Orthogonal Frequency-division Multiplexing) technology and CSMA (Carrier-Sense Multiple Access) technology.

Since the WiFi access point uses OFDM technology, the transmitted RF signal of the WiFi access point must satisfy the OFDM spectrum mask of FIG. 1. For example, in the case of an IEEE 802.11b signal, the transmitted RF signal of the Wi-Fi access point has a spectrum as shown in FIG. 2.

In addition, due to the use of CSMA technology, the RF channel of the Wi-Fi access point as shown in FIG. 5 uses the same frequency for both transmission and reception, so that the Wi-Fi access point does not simultaneously transmit/receive. That is, when a signal is transmitted, a signal is not received, and when a signal is received, a signal is not transmitted. This is implemented using the switch (RF switch) 40 of FIG. 5. During signal transmission, the switch 40 is connected as shown in FIG. 5, so that the RF signal output from the WiFi transceiver 10 is amplified by the power amplifier 20 and connected to the antenna through the switch 40 to transmit the signal. This is done. Conversely, when receiving a signal, the switch 40 is connected downward, and the RF signal received through the antenna is received by the WiFi transceiver 10 through the switch 40 through the low noise amplifier 30.

Meanwhile, in order to implement a multi-band Wi-Fi access point, channel combining is performed using a duplexer 50 in order to combine two different frequency channels (bands) with one antenna as shown in FIG. 6. The duplexer has a channel isolation characteristic of about 30 to 40 dB, and due to the channel isolation characteristic of this duplexer, when channel 1 receives and channel 2 transmits as indicated by a dotted line in FIG. 6, the transmission signal of channel 2 There is a problem that some of the signals are added to the received signal of channel 1.

Even in this case, if the frequency of channel 1 and the frequency of channel 2 are completely separated, the received signal of channel 1 is not affected by the transmission signal of channel 2. However, due to the side band carrier frequency interference as shown in FIG. 3, the side band lobe signal of the transmission channel 2 falls into the in-band of the reception signal of the reception channel 1. Overlap and cause interference.

Conventionally, in order to solve this problem, a band pass filter (BPF) 61 and 62 is connected to the rear end of each transmission channel switch 41 and 42 as shown in FIG. 7. The BPF 61 connected to transmission channel 1 is a BPF corresponding to the frequency band of channel 1, and the BPF 62 connected to transmission channel 2 is a BPF corresponding to the frequency band of channel 2, all of which are composed of a cavity filter. .

When an RF transmission signal having spectral characteristics as shown in FIG. 2 passes through the BPF, only the main lobe RF signal in which the sideband lobe is suppressed is output as shown in FIG. 4.

Therefore, as shown in FIG. 7, when channel 1 is received and channel 2 is transmitted due to the channel isolation characteristic of the duplexer 50, even if a part of the transmission signal of channel 2 is added to the received signal of channel 1, the BPFs 61 and 62 ), the reception channel 1 frequency and the transmission channel 2 frequency are completely separated, so that the received signal of channel 1 is no longer affected by the transmission signal of channel 2.

However, the conventional multi-band Wi-Fi access point having the structure as shown in FIG. 7 has the following problems.

-In order to filter large RF signals, a cavity filter is generally used as a BPF, but the cavity filter is large and expensive.

-Also, because of this, it is almost impossible to support more than the Tri-band (for example, one 2.4GHz band, two 5GHz bands).

An object of the present invention is to provide a multiband Wi-Fi access point capable of minimizing channel interference between adjacent bands.

Another object of the present invention is to provide a multi-band Wi-Fi access point that is small in size, inexpensive in price, and can be used even when a channel frequency is changed.

In the present invention, a noise canceller is connected to a receiving end of a WiFi transceiver to remove a WiFi sideband signal from a received signal. A multiband Wi-Fi access point according to an embodiment of the present invention includes an antenna; An N frequency duplexer connected to the antenna to separate N (N>2) frequency signals; N RF switches having a common terminal and a first terminal and a second terminal selectively connected to the common terminal, the common terminal being connected to one of the N terminals of the N frequency duplexer, respectively; N WiFi transceivers; N power amplifiers having input terminals connected to output terminals of the N Wi-Fi transceivers, and output terminals connected to the first terminals of the N RF switches; N low-noise amplifiers each having input terminals connected to the second terminals of the N RF switches; A reference signal obtained by combining an RF reception signal of a Wi-Fi access point including sideband noise output from the N low-noise amplifiers and an RF transmission signal from other channels is received, and the sideband noise is removed. N noise cancellers respectively outputting RF received signals to the input terminals of the N WiFi transceivers are provided.

In one embodiment, the multi-band Wi-Fi access point further includes N combiners for combining signals of output terminals of power amplifiers of different channels among the N power amplifiers, and outputs of the N combiners are each of the It is connected to the reference signal inputs of the N noise cancellers.

In one embodiment, the N noise cancellers each receive an RF received signal of a Wi-Fi access point including sideband noise, detect an RF center frequency from the received signal, and synchronize to the RF center frequency. PLL (Phase Locked Loop); A first mixer for mixing the synchronized frequency signal output from the PLL and the RF received signal; A first low pass filter configured to output an analog baseband signal including sideband noise by lowpass filtering the output signal of the first mixer; A first A/D converter converting a signal output from the first low-pass filter into a digital signal; A second mixer for mixing the reference signal and the synchronized frequency signal output from the PLL; A second low-pass filter configured to output an analog baseband signal of a reference signal by low-pass filtering the output signal of the first mixer; A second A/D converter converting a signal output from the second low-pass filter into a digital signal; Adaptation of receiving the received baseband signal output from the first A/D converter and the reference baseband signal output from the second A/D converter and outputting a baseband reception signal of a WiFi access point from which sideband noise has been removed Type noise canceller; A D/A converter for converting a baseband reception signal of a Wi-Fi access point from which sideband noise output from the adaptive noise canceller is removed into an analog signal; A third low-pass filter for low-pass filtering the analog signal output from the D/A converter; And a third mixer for mixing the synchronized frequency signal output from the PLL and the signal output from the third low-pass filter to output an RF reception signal of a WiFi access point from which sideband noise has been removed.

In an embodiment, the adaptive noise canceller includes: an adaptive filter for receiving the reference baseband signal and tracking leakage characteristics of the N-frequency duplexer; An adder for outputting a baseband reception signal of a Wi-Fi access point from which sideband noise is removed, which is a value obtained by subtracting an output of an adaptive filter from a reception baseband signal including sideband noise; Includes a coefficient adjustment unit that adjusts and outputs the coefficients of the adaptive filter so that the error is minimized based on the baseband received signal of the Wi-Fi access point from which the sideband noise, which is the error signal (e), has been removed using an adaptive algorithm. do. In one embodiment, the adaptation algorithm may be a least mean square (LMS) algorithm.

According to the present invention, since sideband noise of a Wi-Fi signal input to a receiving end of a Wi-Fi transceiver in a multi-band Wi-Fi access point is removed, interference from transmission signals of other channels is greatly reduced.

In addition, according to the present invention, unlike the cavity filter used in the prior art, not only the size of components such as mixer, PLL, A/D, D/A, LPF, digital filter, etc. is small, but also the price is cheaper than the cavity filter. .

In addition, even if the frequency of the Wi-Fi access point is variable, the PLL inside the Frequency Variable BPF is synchronized with the variable frequency, so that Wi-Fi sideband noise can be removed.

1 shows an OFDM spectrum mask standard specified in IEEE 802.11b.
2 shows a typical 802.11b Wi-Fi signal spectrum.
FIG. 3 shows side band carrier frequency interference in which sideband signals of adjacent channels interfere with signals of this channel.
4 is a spectrum mask with band pass filter showing the spectrum of a signal when passing an 802.11b Wi-Fi signal through a BPF in order to suppress a sideband signal of a general 802.11b Wi-Fi signal. to be.
5 is a diagram illustrating an RF channel configuration of a conventional Wi-Fi access point AP.
6 is a diagram showing a configuration of two RF channels of a multiband Wi-Fi access point in which channels are combined using a duplexer in order to combine two different frequency channels with one antenna.
7 is a diagram illustrating a configuration of a Wi-Fi RF 2 band using a BPF to suppress a sideband lobe.
8 is a diagram illustrating a configuration of a Wi-Fi RF N-band in which a sideband lobe is suppressed using a BPF.
9 is a diagram showing a configuration of a multiband Wi-Fi access point from which sideband noise is removed using a noise canceller according to an embodiment of the present invention.
10 is a diagram showing an example of an internal configuration of a noise canceller.
11 is a diagram illustrating an example of an adaptive noise canceller.

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

9 is a block diagram showing the configuration of a multiband Wi-Fi access point according to an embodiment of the present invention. The example of FIG. 9 shows an access point having three or more 802.11 Wi-Fi transceivers 110A, .., 110N.

A multiband Wi-Fi access point according to an embodiment of the present invention includes an antenna; An N frequency duplexer 151 connected to the antenna to separate N (N>2) frequency signals; N RF switches 140A, each having a common terminal and a first terminal and a second terminal selectively connected to the common terminal, the common terminal being connected to one of the N terminals of the N frequency duplexer 151, respectively. ., 140N); N Wi-Fi transceivers (110A, .., 110N); The input terminals are connected to the output terminals of the N Wi-Fi transceivers (110A, .., 110N), and the output terminals are connected to the first terminals of the N RF switches (140A, .., 140N). N power amplifiers (120A,. ., 120N); N low noise amplifiers 130A, .., and 130N, each having input terminals connected to the second terminals of the N RF switches 140A, .., 140N; By receiving a reference signal that combines the RF reception signal of the Wi-Fi access point including sideband noise output from the N low noise amplifiers (130A, .., 130N) and the RF transmission signal from other channels, sideband noise It includes N noise cancellers 170A, .., and 170N each outputting the removed RF received signal from the Wi-Fi access point to the input terminals of the N Wi-Fi transceivers 110A, .., and 110N. The multi-band Wi-Fi access point according to an embodiment of the present invention also includes N combiners 180A for combining signals of output terminals of power amplifiers of different channels among the N power amplifiers 120A, .., 120N. .., 180N) may be further included. Outputs of the N combiners 180A, .., and 180N are connected to reference signal input terminals of the N noise cancellers 170A, .., and 170N, respectively.

The output of N Wi-Fi transceivers (110A, .., 110N) passes through N power amplifiers (120A, 120B, .., 120N), respectively, to one terminal of N RF switches (140A, 140B, .., 140N). Connected. The common terminals of the N RF switches (140A, 140B, .., 140N) are connected to the N frequency duplexer 151, so that the RF switches (140A, 140B, .., 140N) have a terminal on the transmitting end (the upper terminal in the drawing). ), the output signal of the Wi-Fi transceiver (110A, .., 110N) amplified by the power amplifier (120A, 120B, .., 120N) is connected to the antenna through the N frequency duplexer 151 and transmitted wirelessly. It will be.

The radio signal received through the antenna is connected to the common terminals of the N RF switches 140A, 140B, .., and 140N through the N frequency duplexer 151. When the RF switches 140A, 140B, .., and 140N are connected to the receiving terminal (lower terminal in the drawing), the received signal is input to the input terminal of the low noise amplifiers 130A, 130B, .., and 130N. The output terminals of the low-noise amplifiers 130A, 130B, .., and 130N are input to the reception signal input terminals of the noise cancellers 170A, 170B, .., and 170N, respectively.

Among the radio signals received through the antenna, signals input through an RF switch of another transmission channel are combined in a combiner 180A, 180B, .., 180N, respectively. For example, signals of channels other than channel A are input to the combiner 180A of channel A, and signals of channels other than channel B are input to the combiner 180B of channel B. The signals combined by the combiners 180A, 180B, .., and 180N are input to the reference signal input terminals of the noise cancellers 170A, 170B, .., and 170N, respectively.

The noise canceller (170A, 170B, .., 170N) receives a reference signal that combines the RF received signal of the Wi-Fi access point including sideband noise and the RF transmission signal from other channels, thereby removing sideband noise. Outputs the RF received signal of the access point. The output signals of the noise cancellers 170A, 170B, .., and 170N are input to the receiving ends of the Wi-Fi transceivers 110A, .., and 110N, respectively.

The internal configuration of the noise cancellers 170A, 170B, .., and 170N will be described with reference to FIG. 10.

Each noise canceller 170 includes a PLL (Phase Locked Loop) 178 that receives an RF signal, detects an RF center frequency from the received signal, and synchronizes to the RF center frequency. When the synchronized frequency signal output from the PLL 178 and the RF signal are mixed in a first mixer 177a and passed through the first lowpass filter 176a, a baseband signal including sideband noise is output. do. This baseband signal is converted into a digital signal by the first A/D converter 175a, and the converted digital signal is input to the adaptive noise canceller 174 as a received baseband signal RN containing noise.

The adaptive noise canceller 174 uses a signal fed back from another transmission channel and a signal combined by a combiner 180A, 180B, .., 180N as a reference signal. For example, signals of channels other than channel A are input to the combiner 180A of channel A, and signals of channels other than channel B are input to the combiner 180B of channel B.

The reference baseband signal input to the noise canceller 170 is mixed in the second mixer 177b and passes through the second lowpass filter 176b to become an analog reference baseband signal. This analog reference baseband signal is converted into a digital signal by the second A/D converter 175b, and the converted digital signal is input to the adaptive noise canceller 174 as a reference baseband signal RS.

The adaptive noise canceller 174 receives the baseband signal (RN) and the reference baseband signal (RS) of the WiFi access point including sideband noise and receives the baseband of the WiFi access point from which the sideband noise is removed. Output the signal. The baseband received signal from which noise has been removed is converted into an analog signal by the D/A converter 173, and the analog signal is an analog base from which sideband noise is removed by passing only a low-frequency signal through the third low-pass filter 172. The band reception signal is output. The analog baseband reception signal from which sideband noise is removed is mixed with the RF synchronization frequency signal output from the PLL 178 in the third mixer 171 to output an RF received signal from which sideband noise is removed.

An embodiment of the adaptive noise canceller 174 will be described with reference to FIG. 11.

The reference baseband signal (RS) received from other transmission channels is input to an adaptive filter (1741). The adaptive filter 1741 tracks a leakage characteristic of a duplexer by an adaptive algorithm. As a result, the output of the adaptive filter 1741 becomes the same as the side band noise transferred from other transmission channels. The adder 1743 calculates a value obtained by subtracting the output of the adaptive filter 1741 from the received baseband signal RN including sideband noise. The output of the adder 1743 becomes a baseband reception signal of a WiFi access point from which sideband noise has been removed. The coefficient adjustment unit 1742 uses an adaptive algorithm to minimize the error based on the baseband received signal of the Wi-Fi access point from which the sideband noise, which is the error signal e, has been removed. Adjust and print.

As the adaptation algorithm, various adaptation algorithms such as Least Mean Square (LMS), Recursive Least Square (RLS), LMS Newton, Normalized LMS, Affine Projection, etc. can be used. In particular, since the leakage characteristics of the duplexer hardly change over time, it is desirable to use the simplest and most stable LMS algorithm.

In the LMS algorithm, the coefficient of the next (n+1) frame is calculated using Equation 1.

In Equation 1, C _i (n) is the i-th coefficient of the current (n) frame, u = convergence constant, y (n) = the output of the adaptive filter, and e(n) when ESBN is the estimated sideband noise = RN- ESBN.

As the adaptive filter 1741, a widely used and stable FIR filter can be used. The output y(n) of the N-order FIR filter can be expressed as in Equation 2.

In Equation 2, C _i (n) is the i-th coefficient of the current frame calculated by the adaptive algorithm 1742, and RS _i (n) represents the i-time delayed reference signal of the current frame. .

The present invention having the configuration as shown in Figs. 9 to 11, unlike the cavity filter used in the prior art having the configuration as shown in Fig. 7, components such as mixer, PLL, A/D, D/A, LPF, adaptive filter, etc. It is not only small in size, but also inexpensive compared to the cavity filter.Especially, even if the frequency of the Wi-Fi access point is variable, the PLL inside the noise canceller is synchronized to the variable frequency, so Wi-Fi sideband noise can be removed. There is an advantage.

In the above, although the present invention has been described with reference to several examples, the present invention is not necessarily limited to these embodiments, even though it has been described that all the components constituting the embodiments of the present invention are combined into one or operated in combination. That is, within the scope of the object of the present invention, all of the constituent elements may be selectively combined and operated in one or more. In addition, although all of the components may be implemented as one independent hardware, a program module that performs some or all functions combined in one or more hardware by selectively combining some or all of the components. It may be implemented as a computer program having Codes and code segments constituting the computer program may be easily inferred by those skilled in the art of the present invention. Such a computer program may be stored in a computer or processor readable storage medium, and read and executed by a computer or processor, thereby implementing an embodiment of the present invention.

Terms such as "include", "consist of" or "have" described above, unless otherwise stated, mean that the corresponding component may be present, and thus other components are not excluded. It should be interpreted as being able to further include other components.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

110A~110N wifi transceiver,
120A~120N power amplifier,
130A~130N low noise amplifier,
140A~140N RF switch,
151 N frequency duplexer,
170A~170N noise canceller,
180A~180N combiner.

Claims (4)

antenna;
An N frequency duplexer connected to the antenna to separate N (N>2) frequency signals;
N RF switches having a common terminal and a first terminal and a second terminal selectively connected to the common terminal, the common terminal being connected to one of the N terminals of the N frequency duplexer, respectively;
N WiFi transceivers;
N power amplifiers having input terminals connected to output terminals of the N Wi-Fi transceivers, and output terminals connected to the first terminals of the N RF switches;
N low noise amplifiers whose input terminals are respectively connected to the second terminals of the N RF switches;
A reference signal obtained by combining an RF reception signal of a Wi-Fi access point including sideband noise output from the N low-noise amplifiers and an RF transmission signal from other channels is received, and the sideband noise is removed from the Wi-Fi access point. N noise cancellers respectively outputting RF received signals to the input terminals of the N Wi-Fi transceivers;
Multi-band Wi-Fi access point having a. The method of claim 1, wherein the multi-band WiFi access point,
Further comprising N combiners for combining signals of output terminals of power amplifiers of different channels among the N power amplifiers,
The outputs of the N combiners are connected to the reference signal inputs of the N noise cancellers, respectively. The method of claim 2, wherein each of the N noise cancellers,
A PLL (Phase Locked Loop) for receiving an RF received signal from a Wi-Fi access point including sideband noise, detecting an RF center frequency from the received signal, and synchronizing to the RF center frequency;
A first mixer for mixing the synchronized frequency signal output from the PLL and the RF received signal;
A first low pass filter configured to output an analog baseband signal including sideband noise by lowpass filtering the output signal of the first mixer;
A first A/D converter converting a signal output from the first low-pass filter into a digital signal;
A second mixer for mixing the reference signal and the synchronized frequency signal output from the PLL;
A second low-pass filter configured to output an analog baseband signal of a reference signal by low-pass filtering the output signal of the first mixer;
A second A/D converter converting a signal output from the second low-pass filter into a digital signal;
Adaptation of receiving the received baseband signal output from the first A/D converter and the reference baseband signal output from the second A/D converter and outputting a baseband reception signal of a WiFi access point from which sideband noise has been removed Type noise canceller;
A D/A converter for converting a baseband reception signal of a Wi-Fi access point from which sideband noise output from the adaptive noise canceller is removed into an analog signal;
A third low-pass filter for low-pass filtering the analog signal output from the D/A converter;
A third mixer for mixing the synchronized frequency signal output from the PLL and the signal output from the third low-pass filter to output an RF reception signal of a WiFi access point from which sideband noise has been removed;
Multi-band Wi-Fi access point comprising a. The method of claim 3, wherein the adaptive noise canceller
An adaptive filter for receiving the reference baseband signal and tracking leakage characteristics of the N-frequency duplexer;
An adder for outputting a baseband reception signal of a Wi-Fi access point from which sideband noise is removed, which is a value obtained by subtracting an output of an adaptive filter from a reception baseband signal including sideband noise;
A coefficient that adjusts and outputs the coefficient of the adaptive filter 1741 so that the error is minimized based on the baseband received signal of the Wi-Fi access point from which the sideband noise, which is the error signal (e), has been removed using an adaptive algorithm Adjustment unit;
Multi-band Wi-Fi access point comprising a.

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