KR101235833B1 - Apparatus and method for receiving using multi antenna in wireless communication system - Google Patents

Abstract

The present invention relates to a receiving apparatus and method in a wireless communication system, and more particularly, to a receiving apparatus and method in a wireless communication system using multiple antennas.

The apparatus according to the present invention includes a plurality of variable gain amplifiers for adjusting gains of RF signals received through a plurality of antennas, and a plurality of signals for converting signals output from the plurality of variable gain amplifiers into digital signals, respectively. A receiving device including analog to digital converters, comprising: receiving digital signals output from the plurality of analog to digital converters, calculating gains of the variable gain amplifiers, and calculating a minimum gain value among the calculated gain values; An automatic gain controller for calculating difference values between the minimum gain value and the remaining gain values, and a plurality of noise matching amplifiers for attenuating digital signals output from the plurality of analog to digital converters according to the calculated difference values. Include.

Digital Amplifier, Noise Variance, Automatic Gain Controller (AGC), Antenna

Description

Receiving apparatus and method in wireless communication system using multiple antennas {APPARATUS AND METHOD FOR RECEIVING USING MULTI ANTENNA IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a receiving apparatus and method in a wireless communication system, and more particularly, to a receiving apparatus and method in a wireless communication system using multiple antennas.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy [2006-S-014-03, 200Mbps IEEE 802.11n modem and RF chipset development].

The receiving end of a general wireless communication system uses a variable gain amplifier (VGA) and an analog digital converter (ADC). The variable gain amplifier (VGA) functions to correct the gain of the signal received at the receiving end, and the analog-to-digital converter (ADC) converts the analog signal passed through the variable gain amplifier (VGA) into a digital signal.

If the signal received at the receiving end of the wireless communication system excessively sets the gain of the signal in the variable gain amplifier (VGA), the signal passing through the variable gain amplifier (VGA) may be out of the operating range of the analog-to-digital converter (ADC). have. This causes the distortion of the received signal. On the contrary, if the gain of the signal is set small in the variable gain amplifier (VGA), the demodulation performance is lowered because the quantization noise is increased.

On the other hand, the gain control of the signal received by a general multiple antenna was properly adjusted for each antenna. However, in the wireless channel, the power of the input signal is different for each antenna. In some cases, the power magnitude of a signal in one antenna is more than 100 times greater than the power of a signal received by another antenna. In this case, an antenna having a large power of a received signal has a low relative noise after gain adjustment, while an antenna having a small power of a received signal has a high relative noise after gain adjustment. That is, an antenna having a large power of a received signal has a high signal-to-noise ratio, and an antenna having a small power of a received signal has a low signal-to-noise ratio.

As such, although the signal-to-noise ratio of each antenna of the multiple antennas is different according to the environment of the wireless channel, when gain adjustment is performed by an AGC (Automatic Gain Controller) and a variable gain amplifier (VGA), the output of the variable gain amplifier (VGA) The average power of the signals is about the same. When the signals having similar average powers are input to a multiple input multiple output (MIMO) system, particularly when applied to a linear equalizer having a simple implementation complexity, the demodulation performance of the signal is degraded.

In addition, after the gain is adjusted by the variable gain amplifier (VGA), if the frequency bandwidth of the received signal is decreased or increased, that is, if the frequency bandwidth is changed, the gain voltage reference value of the variable gain amplifier (VGa) should also be changed. There was a problem.

Accordingly, an object of the present invention is to provide a receiving apparatus and method in a wireless communication system capable of preventing deterioration of demodulation performance when signal-to-noise ratios are different for each antenna of a multi-antenna system.

It is another object of the present invention to provide a receiving apparatus and method in a wireless communication system that does not change the gain voltage reference value of the variable gain amplifier when the frequency bandwidth of the received signal varies.

The apparatus according to the present invention includes a plurality of variable gain amplifiers for adjusting gains of RF signals received through a plurality of antennas, and a plurality of signals for converting signals output from the plurality of variable gain amplifiers into digital signals, respectively. A receiving device including analog to digital converters, comprising: receiving digital signals output from the plurality of analog to digital converters, calculating gains of the variable gain amplifiers, and calculating a minimum gain value among the calculated gain values; An automatic gain controller for calculating difference values between the minimum gain value and the remaining gain values, and a plurality of noise matching amplifiers for attenuating digital signals output from the plurality of analog to digital converters according to the calculated difference values. Include.

In addition, the method according to the present invention, a plurality of variable gain amplifiers for adjusting the gain of the RF signals received through a plurality of antennas and the signals output from the plurality of variable gain amplifiers respectively converted into digital signals, respectively A receiving method comprising a plurality of analog to digital converters, the method comprising: receiving digital signals output from the plurality of analog to digital converters from an automatic gain controller and calculating gain values of the plurality of variable gain amplifiers; A gain controller selecting a minimum gain value among the calculated gain values, the automatic gain controller calculating a difference value between the minimum gain value and the remaining gain values, and a plurality of noise matching amplifiers using the calculated difference Digital scene output from the analog to digital converters according to the values Including the process of the decay.

Using the apparatus and method according to the present invention, in a linear receiver of a WLAN system using multiple antennas, there is an advantage that can make noise variance for each antenna almost similar. It also has the advantage of not changing the gain voltage reference of the variable gain amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. In the following description of the present invention, a part obvious to those skilled in the art will be omitted so as not to disturb the gist of the present invention. In addition, it is to be noted that each of the terms described below are only used to help the understanding of the present invention, and may be used in different terms despite the same purpose in each manufacturing company or research group. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated with like reference numerals throughout the specification.

1 is a block diagram of a receiving apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 1, a receiving apparatus according to an exemplary embodiment of the present invention may include a variable gain amplifier 100, an analog digital converter (ADC) 200, an automatic gain controller (AGC). 300, a noise matching amplifier (AMP) 400, and a modem (not shown). Here, for convenience of description, a reception path starting with the first antenna 1 is called a first reception path, and a reception path starting with the second antenna 2 is called a second reception path, and the third antenna 3 A reception path starting with a) is called a third reception path. The variable gain amplifier 100, the ADC 200, and the noise matching amplifier 400 are positioned on each of the first to third receive paths. And the first to third receive paths are connected to a modem (not shown).

The variable gain amplifier 100 receives an RF signal input through each of the plurality of antennas 1, 2, and 3. The variable gain amplifier 100 includes a low noise amplifier (LNA) 121 and a variable gain amplifier (VGA) 122. The variable gain amplifier 100 amplifies an RF signal including an in-phase (I) signal and a quadrature (Q) signal by applying a gain to an input RF signal. In this case, the gain applied to the RF signal is determined according to the power of the input RF signal.

The LNA 121 may roughly adjust the gain of the input RF signal. When the gain adjustment is performed to some extent in the LNA 121, the VGA 122 performs fine gain adjustment. In this way, if the gain control width can be adjusted according to system requirements by simultaneously using the LNA 121 and the VGA 122, fast and stable gain adjustment can be performed.

The ADC 200 converts the RF signal amplified by the variable gain amplifier 100 into a digital signal. Since the ADC 200 has a certain operating range, the variable gain amplifier 100 must adjust the gain so that the amplified RF signal input to the ADC 200 is included in the operating range of the ADC 200. . This gain adjustment is performed at AGC 300.

The AGC 300 receives a digital signal output from the ADC 200 on the first path, calculates a difference between the digital signal and a predetermined reference signal, and then uses the calculated difference value to determine the LNA on the first path. A gain value for controlling the 121 and the VGA 122 is calculated. In addition, a gain control signal corresponding to the calculated gain value is provided to the LNA 121 and the VGA 122 on the first path. In a similar manner, the gain values for controlling the LNA 121 and the VGA 122 on the second path and the third path are respectively calculated, and gain control signals corresponding to the calculated gain values are calculated on the second to third paths. Provided by LNA 121 and VGA 122.

Also, the AGC 300 extracts the minimum gain value among the gain values for controlling the LNA 121 and the VGA 122 on the calculated first to third paths. Then, the difference between the remaining two gain values and the estimated minimum gain value is respectively calculated, and the calculated relative gain difference values are provided to the noise matching amplifier 400 on the first to third paths.

The noise matching amplifier 400 receives a signal output from the ADC 200 and a relative gain difference value output from the AGC 300. Then, the noise matching amplifier 400 attenuates and outputs the signal output from the ADC 200 using the provided relative gain difference value.

A modem (not shown in the figure) processes the signal output from the noise matching amplifiers 400 on the first to third paths. These modems include buffers, carrier frequency offset (CFO) compensators, FET operators, phase compensators, detectors, demappers, deinterleavers, deparers, decoders, and descramblers. (Descrambler), MAC, etc. may be implemented. Here, the detector comprises a linear equalizer. The linear equalizer may perform 2x3 MIMO detection, H-automatic detection, pseudo EVM calculation, and amplitude tracking.

Then, the operation of the receiving apparatus according to the preferred embodiment of the present invention shown in FIG. 1 will be described in detail below.

In FIG. 1, it is assumed that RF signals input to the plurality of antennas 1, 2, and 3 are all different in power. RF signals input to the first to third paths through the plurality of antennas 1, 2, and 3 are passed through the LNA 121 and the VGA 122 on each path to adjust gain. The signal is converted into digital signals by the ADC 200 and finally input to the modem 500. However, the digital signals passing through the ADC 200 on each path are input to the AGC 300. AGC 300 then converts the provided digital signals into gain control signals for adjusting the gain of LNA 121 and VGA 122 on each path, and converts the converted gain control signals to LNA 121 on each path. And VGA 122. Here, a method of generating gain control signals for controlling the gain of the LNA 121 and the VGA 122 on each path will be described in detail below.

First, AGC 300 calculates the power of each of the RF signals in digital form. The calculation of power assumes that only a predetermined section of each of the RF signals in the digital form calculates power. For example, in the case of a WLAN system, the power of RF signals corresponding to 0.8us (sec) is calculated.

If the ADC 200 becomes saturated during the power measurement period, the AGC 300 stops calculating power and reduces the gain value of the variable gain amplifier 100 by a predetermined register value (gain_large). If the ADC 200 is not saturated during the power measurement period and the calculated power is smaller than the target value, that is, the voltage reference value, the gain value is calculated to be equal to the voltage reference value. During the power measurement interval, if the calculated power is greater than the voltage reference value, the gain value is calculated so that the calculated power is equal to the voltage reference value. This approach speeds up gain adjustment when the power of the received RF signal is large.

AGC 300 waits for a predetermined period of time until a new gain value is calculated. However, the period should be large enough so that the RF signal is applied to the gain change. The power calculation and gain update after this period are performed repeatedly until the measured power becomes less than the voltage reference value, thereby updating the gain value. The updated gain value is maintained at the gain values of the LNA 121 and the VGA 122 for some time. In this way, the signals output from the ADC 200 are not saturated, and the effects due to quantization errors are minimized.

After the above process, the AGC 300 selects the minimum gain value among the calculated gain values. The path having the smallest gain value is determined to have the largest signal-to-noise ratio (SNR), and the remaining two paths are determined to have a relatively small signal-to-noise ratio. Thus, the remaining two paths with a small signal-to-noise ratio have a larger gain than the path with the largest signal-to-noise ratio.

AGC 300 then calculates the difference between the minimum gain value and the other gain values and provides the calculated gain difference values to each noise matching amplifier 400 on the first to third paths.

The noise matching amplifier 400 then attenuates the signal output from the ADC 200 using the gain difference value provided.

The reason for equalizing the power of noise variance is necessary to decorrelate the RF signal input to the plurality of antennas in the linear equalizer of the modem. Equation 1 below shows a signal received by multiple antennas.

Referring to Equation 1, in order to obtain the transmitted signal x with the RF signal r received by the plurality of antennas, the vector x of the transmitted signal can be estimated by applying a linear equalizer. Can be. Equations 2 to 6 below are processes for estimating the transmitted signal vector x. Here, H means a channel and n means noise.

Processing the vector x of the transmitted signal with a linear equalizer can neglect the effect on noise variance. How this noise variance affects the reception performance will be described with reference to Equations 7 to 10 below.

If only the part affected by noise in Equation 7 is separated, Equation 8 is shown below.

In Equation 8, when the variance of noise is defined, Equation 9 below is defined.

In Equation 9, when all the terms are squared to obtain a noise variance, Equation 10 is given below.

)의 값과 등화 벡터(w)에 영향을 받는 형태가 된다. 만약, 각 제 1 내지 제 3 경로 별로 노이즈 분산(noise variance,

)값이 동일하면, 아래의 <수학식 11>과 같이 등가적으로 표현할 수 있다.As shown in Equation 10, noise variance for each of the first to third paths

) And the equalization vector (w). If the noise variance for each of the first to third paths,

If the) values are the same, they can be equivalently expressed as in Equation 11 below.

As shown in Equation 11, when the noise variance becomes equal for each of three paths, the quality of the signal obtained by using the linear equalizer during signal demodulation is equalized by the equalization vector (w) rather than the effect of the noise of each antenna. Can only be judged by the norm of

In addition, the receiving apparatus according to the preferred embodiment of the present invention has a noise matching amplifier 400 in a wireless communication system supporting multiple bandwidths, the same in any bandwidth as long as AGC 300 does not change the voltage reference value (Vref) Effectively cover the dynamic range to have a voltage reference value.

2 and 3 are graphs showing a packet error rate (PER) with respect to a voltage reference value when having a bandwidth of 20 MHz or 40 MHz.

Referring to FIG. 2, it can be seen that the voltage reference value Vref, which brings the best performance for each bandwidth, is different, and the range of the voltage reference value is lower than that of 40 MHz when receiving a signal having a 20 MHz bandwidth. Therefore, when the bandwidth of the noise matching amplifier 400 is reduced and the size of the final output is reduced by 20 MHz, it can be seen that a range of similar voltage reference values is obtained as shown in FIG. 3.

So far I looked at the center of the preferred embodiment for the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The disclosed embodiments should, therefore, be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

1 is a block diagram of a receiving apparatus according to a preferred embodiment of the present invention.

2 and 3 are graphs showing a packet error rate (PER) with respect to a voltage reference value when having a bandwidth of 20 MHz or 40 MHz.

Claims (6)

Receiving includes a plurality of variable gain amplifiers for adjusting the gain of the RF signals received through a plurality of antennas, and a plurality of analog to digital converters for converting the signals output from the plurality of variable gain amplifiers into digital signals, respectively In the device, Receiving the digital signals output from the plurality of analog-to-digital converters, calculating gain values of the plurality of variable gain amplifiers, selecting a minimum gain value from the calculated gain values, the minimum gain value and the remaining gain values An automatic gain controller for calculating the difference values of A plurality of noise matching amplifiers for attenuating digital signals output from the plurality of analog to digital converters according to the calculated difference values Receiving device comprising a. The method of claim 1, Each of the variable gain amplifiers, A receiving device comprising a low noise amplifier (LNA) and a variable gain amplifier (VGA). The method of claim 1, And a modem for processing signals output from the plurality of noise matching amplifiers, the modem comprising a linear equalizer. Receiving includes a plurality of variable gain amplifiers for adjusting the gain of the RF signals received through a plurality of antennas, and a plurality of analog to digital converters for converting the signals output from the plurality of variable gain amplifiers into digital signals, respectively In the method, Calculating the gain values of the plurality of variable gain amplifiers by receiving the digital signals output from the plurality of analog to digital converters in an automatic gain controller; Selecting, by the automatic gain controller, a minimum gain value from the calculated gain values; Calculating, by the automatic gain controller, difference values between the minimum gain value and the remaining gain values; A plurality of noise matching amplifiers attenuate digital signals output from the analog to digital converters according to the calculated difference values Including, the receiving method. 5. The method of claim 4, Each of the variable gain amplifiers, A low noise amplifier (LNA) and a variable gain amplifier (VGA). 5. The method of claim 4, And inputting signals output from the plurality of noise matching amplifiers to a linear equalizer included in a modem.

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