KR20120068527A - Method and apparatus for providing quadrature error correction in binary phase shift keying - Google Patents

Method and apparatus for providing quadrature error correction in binary phase shift keying Download PDF

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KR20120068527A
KR20120068527A KR1020100130189A KR20100130189A KR20120068527A KR 20120068527 A KR20120068527 A KR 20120068527A KR 1020100130189 A KR1020100130189 A KR 1020100130189A KR 20100130189 A KR20100130189 A KR 20100130189A KR 20120068527 A KR20120068527 A KR 20120068527A
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phase shift
signal
shift keying
quadrature error
binary phase
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KR1020100130189A
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Korean (ko)
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박승근
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한국전자통신연구원
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/22—Demodulator circuits; Receiver circuits

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  • Computer Networks & Wireless Communication (AREA)
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  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

Although quadrature error due to incomplete 90 degree phase shifter of binary phase shift keying (BPSK) demodulation system has been analyzed in the performance field of communication system, new demodulation method using quadrature error It is not presented. Accordingly, an embodiment of the present invention proposes a quadrature error compensation technique of a BPSK system that can improve the performance of a BPSK demodulation system in a correlated Gaussian channel environment by calculating an average of Q signals and transforming a BPSK signal in a BPSK demodulation system.

Description

METHOD AND APPARATUS FOR PROVIDING QUADRATURE ERROR CORRECTION IN BINARY PHASE SHIFT KEYING}

The present invention relates to an I (In-phase) / Q (Quadrature-phase, 90 degree) modulation and demodulation technique in a Gaussian channel environment, and in particular, quadrature error caused by incomplete performance of a 90 degree phase shifter. The present invention relates to a quadrature error compensation method and a compensation device of a BPSK system suitable for improving binary phase shift keying (BPSK) demodulation performance.

Due to the quadrature error of the 90-degree phase shifter, the I demodulated signal and the Q demodulated signal are displayed in the form of an elliptic contour on the I / Q constellation, so that two BPSK demodulated signals are brought close to each other so that the signal interval between them becomes narrow. There is a problem of increasing the bit error rate.

Although the quadrature error due to the incomplete 90 degree phase shifter of the BPSK demodulation system has been performed in the field of performance of the communication system, a new demodulation method using the quadrature error has not been proposed.

Accordingly, an embodiment of the present invention proposes a quadrature error compensation technique of a BPSK system that can improve the performance of a BPSK demodulation system in a correlated Gaussian channel environment by calculating an average of Q signals and transforming a BPSK signal in a BPSK demodulation system.

The quadrature error compensating apparatus of the BPSK system according to an embodiment of the present invention includes an I channel mixer for multiplying a received signal in a Gaussian channel environment with an in-phase channel signal, and the received signal with a quadrature-phase channel. A Q channel mixer to multiply the signal, an I filter for filtering the output signal of the I channel mixer to output an I digital signal, a Q filter for filtering the output signal of the Q channel mixer to output a Q digital signal, and the Q An average value calculation unit for calculating an average value by sampling the Q digital signal of the filter over time, a conversion unit for converting an average value of the I digital signal of the I filter and the average value calculation unit, and a predetermined determination of the conversion result of the conversion unit It may include a determination unit for selecting a phase corresponding to the transmission bit by the reference.

Here, the received signal is,

Figure pat00001
E b is the energy per bit, T is the time interval of the bit,
Figure pat00002
Is the carrier,
Figure pat00003
Is the transmission phase angle of each bit,
Figure pat00004
Means that the mean is zero and the variance is
Figure pat00005
It may be characterized as a Gaussian noise.

In addition, the Q channel signal,

Figure pat00006
Lt; / RTI >

In addition,

Figure pat00007
May be a quadrature error of a 90 degree phase shifter.

In addition, the I digital signal and Q digital signal,

Figure pat00008
E b is energy per bit, and θ m has -π or π depending on the transmission bit,
Figure pat00009
Is quadrature error, and N I and N Q may be noise variables.

In addition, N I and N Q have an average of zero and a variance of

Figure pat00010
, Correlation coefficient
Figure pat00011
A bivariate Gaussian distribution with

In addition, the said average value is a mathematical formula

Figure pat00012
Can be saved by

In addition, the conversion unit,

Figure pat00013
A new binary phase shift keying signal can be obtained.

The new binary phase shift keying signal may be a signal in which the major axis direction of the elliptic contour is changed by 90 degrees.

In addition, the predetermined determination criterion is,

Figure pat00014
It can be characterized by.

In the quadrature error compensation method of the BPSK system according to an embodiment of the present invention, a process of multiplying a received signal in a Gaussian channel environment with an I channel signal, a process of multiplying the received signal with a Q channel signal, and a multiplication with the I channel signal Outputting the I digital signal by filtering the output signal of the process; outputting the Q digital signal by filtering the output signal of the process of multiplying with the Q channel signal; and sampling the Q digital signal over time to average Calculating, converting the I digital signal and the average value, and selecting a phase corresponding to a transmission bit according to a predetermined criterion for the conversion result of the I digital signal and the average value. have.

Here, the received signal is,

Figure pat00015
E b is the energy per bit, T is the time interval of the bit,
Figure pat00016
Is the carrier,
Figure pat00017
Is the transmission phase angle of each bit,
Figure pat00018
Means the mean is zero and the variance is
Figure pat00019
It may be characterized as a Gaussian noise.

In addition, the Q channel signal,

Figure pat00020
Lt; / RTI >

In addition,

Figure pat00021
May be a quadrature error of a 90 degree phase shifter.

In addition, the I digital signal and Q digital signal,

Figure pat00022
E b is energy per bit, and θ m has -π or π depending on the transmission bit,
Figure pat00023
Is quadrature error, and N I and N Q may be noise variables.

In addition, N I and N Q have an average of zero and a variance of

Figure pat00024
, Correlation coefficient
Figure pat00025
A bivariate Gaussian distribution with

In addition, the said average value is a mathematical formula

Figure pat00026
Can be saved by

In addition, the process of converting,

Figure pat00027
May include obtaining a new binary phase shift keying signal.

The new binary phase shift keying signal may be a signal in which the major axis direction of the elliptic contour is changed by 90 degrees.

In addition, the predetermined determination criterion is,

Figure pat00028
It can be characterized by.

According to the present invention, the bit error rate performance of the BPSK system can be greatly improved by using the quadrature error, thereby improving reliability and accuracy in the field of BPSK modulation and demodulation technology.

1 shows a quadrature error in a Gaussian channel environment, for example

Figure pat00029
I / Q signal constellation of BPSK system with quadrature error = π / 8,
2 is an I / Q signal constellation diagram of a BPSK system using a quadrature error compensation method according to an embodiment of the present invention;
3 is a block diagram illustrating a quadrature error compensation apparatus and method of a BPSK system according to an embodiment of the present invention;
4 is a quadrature error
Figure pat00030
A graph comparing the bit error rate of the existing BPSK system in the case of = pi / 8 and the bit error rate of the BPSK system according to an embodiment of the present invention.

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. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like numbers refer to like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Each block of the accompanying block diagrams and combinations of steps of the flowchart may be performed by computer program instructions. These computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment such that instructions executed through the processor of the computer or other programmable data processing equipment may not be included in each block or flowchart of the block diagram. It will create means for performing the functions described in each step. These computer program instructions may be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, and thus the computer usable or computer readable memory. It is also possible for the instructions stored in to produce an article of manufacture containing instruction means for performing the functions described in each block or flowchart of each step of the block diagram. Computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operating steps may be performed on the computer or other programmable data processing equipment to create a computer-implemented process to create a computer or other programmable data. Instructions that perform processing equipment may also provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

Also, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments the functions noted in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

The present invention aims to improve the bit error rate performance of a BPSK demodulation system in a correlated Gaussian channel environment by averaging the Q signal and converting the BPSK signal to an existing BPSK demodulation system.

Due to the quadrature error of the 90-degree phase shifter, the I / Q demodulated signal is represented in the form of an elliptic contour on the I / Q constellation, and the two BPSK demodulated signals are brought close to each other, so that the two signal intervals are narrowed to increase the bit error rate. Problems may arise.

The present invention proposes a conversion equation for adjusting the long axis direction of the elliptic contour of the signal in the BPSK demodulation process by using the amplitude average of the Q signal.

In general, an I / Q signal of a quadrature BPSK system in a Gaussian channel environment may be expressed as Equation 1 below.

Figure pat00031

Where E b is the energy per bit, phase θ m has either -π or π depending on the transmission bit,

Figure pat00032
Is a quadrature error, and the two noise variables, N I and N Q, have an average of zero and a variance of
Figure pat00033
, Correlation coefficient
Figure pat00034
Follow the bivariate Gaussian distribution with.

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

1 is a phase that generates quadrature error in I / Q constellation

Figure pat00035
An example of an elliptic contour of two BPSK signals is shown.

For the transmission bit identification of the BPSK system represented by Equation 1, the discrimination criteria of Equation 2 are used.

Figure pat00036

As shown in Figure 1, the correlation coefficient between the I signal and the Q signal shown in [Equation 1]

Figure pat00037
Phase
Figure pat00038
Has a positive and negative value.

In an embodiment of the present invention, the BPSK signal sampled by Equation 1

Figure pat00039
Next, the new BPSK signal is obtained using Equation 3 below.
Figure pat00040
Can be obtained.

Figure pat00041

here,

Figure pat00042
Is an average of Q values obtained by sampling over time, and can be obtained as shown in Equation 4 below.

Figure pat00043

Two variables created by the conversion formula [Equation 3]

Figure pat00044
Wow
Figure pat00045
The correlation coefficient of
Figure pat00046
And each variance is
Figure pat00047
Same as

FIG. 2 shows the shape of the BPSK signal newly obtained by Equation 3, and shows that the long axis direction of the elliptic contour of the BPSK signal shown in FIG. 1 is changed by 90 degrees.

In addition, in the embodiment of the present invention, when two variances of the bivariate Gaussian distribution are the same, the angle between the Q axis and the elliptic contour long axis of the signal is constant at 45 degrees. A new discrimination criterion to cope can be obtained from the coordinate transformation as shown in Equation 5 below.

Figure pat00048

In addition, Equation 6 below is a new discrimination criterion obtained from Equation 5.

Figure pat00049

3 is a diagram for describing a quadrature error compensation method and apparatus of a BPSK system according to an exemplary embodiment of the present invention.

The quadrature error compensator of the BPSK system includes an I channel mixer 102, a Q channel mixer 104, an I filter 202, a Q filter 204, an average value calculation unit 304, a conversion unit 400, and a determination unit. 500, and the like.

The I channel mixer 102 may multiply the received signal in a Gaussian channel environment by the I channel signal.

The Q channel mixer 104 may multiply the received signal by the Q channel signal.

The I filter 202 may output the I digital signal by filtering the output signal of the I channel mixer 1 102.

The Q filter 204 may output the Q digital signal by filtering the output signal of the Q channel mixer 104.

The average value calculator 304 may calculate the average value by sampling the Q digital signal of the Q filter 204 with time.

The converter 400 may convert an I digital signal of the I filter 202 and an average value of the average value calculator 304.

The determination unit 500 may select a phase corresponding to the transmission bit based on a determination criterion as shown in Equation 6 with respect to the conversion result of the conversion unit 400.

In the Gaussian channel environment, the received signal may be expressed as Equation 7 below.

Figure pat00050

Where E b is energy per bit, T is the time interval of bits,

Figure pat00051
Is the carrier,
Figure pat00052
Is the transmission phase angle of each bit,
Figure pat00053
Means that the mean is zero and the variance is
Figure pat00054
Is Gaussian noise.

Received signal

Figure pat00055
Can be multiplied by each mixer 102, 104 of the I and Q channels. In particular, the input signal of the Q channel mixer 104
Figure pat00056
Phase
Figure pat00057
Is the quadrature error of the 90-degree phase shifter.

The two mixer output signals obtain an I / Q digital signal as shown in Equation 1 by each I / Q filter 202 and 204.

On the Q channel, the average value of the Q signal may be sequentially calculated using Equation 4, and then a conversion process may be performed as shown in Equation 3 from the average value of the Q signal.

The converted two signals may select one of two phases corresponding to the transmission bit by a discrimination criterion as shown in [Equation 6].

On the other hand, the bit error rate of the BPSK demodulation system having a quadrature error in a Gaussian channel environment can be obtained as shown in Equation (8).

Figure pat00058

here,

Figure pat00059
ego,
Figure pat00060
Is noise power,
Figure pat00061
to be.

The bit error rate of the BPSK system to which the present invention is applied can be obtained by using Equation 6 as shown in Equation 9 below.

Figure pat00062

2,

Figure pat00063
Therefore, the bit error rate of the BPSK system used in the embodiment of the present invention can be illustrated as Equation 10 below.

Figure pat00064

Where random variables

Figure pat00065
The average of
Figure pat00066
And the variance is
Figure pat00067
to be.

Finally, the normalization of the Gaussian distribution

Figure pat00068
When applied to Equation 10, the bit error rate according to an embodiment of the present invention can be illustrated as Equation 11 below.

Figure pat00069

4 is a quadrature error

Figure pat00070
Is a graph comparing the bit error rate of the existing BPSK system and the bit error rate of the BPSK system according to an embodiment of the present invention.

As shown in FIG. 4, it can be seen that the bit error rate is improved as compared with the related art.

According to the embodiment of the present invention as described above, by calculating the average of the Q signal to the existing BPSK demodulation system by proposing a conversion equation for adjusting the long axis direction for the elliptic contour of the signal in the BPSK demodulation process using the amplitude average of the Q signal In order to improve the bit error rate performance of the BPSK demodulation system in a correlated Gaussian channel environment, the BPSK signal is converted.

102: I channel mixer
104: Q channel mixer
202: I filter
204: Q filter
304: average calculation unit
400: converter
500: determination unit

Claims (20)

An I-channel mixer that multiplies the received signal in a Gaussian channel environment with an I-channel signal,
A Q channel mixer for multiplying the received signal by a quadrature-phase (Q) channel signal;
An I filter for outputting an I digital signal by filtering an output signal of the I channel mixer;
A Q filter for outputting a Q digital signal by filtering an output signal of the Q channel mixer;
An average value calculator for sampling the Q digital signal of the Q filter with time to calculate an average value;
A converter for converting an average of the I digital signal of the I filter and the average value calculator;
A determination unit for selecting a phase corresponding to a transmission bit based on a predetermined determination criterion for the conversion result of the conversion unit;
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
The received signal is,
Equation
Figure pat00071
Lt; / RTI >
E b is energy per bit, T is time interval of bits,
Figure pat00072
Is the carrier,
Figure pat00073
Is the transmission phase angle of each bit,
Figure pat00074
Means the mean is zero and the variance is
Figure pat00075
Characterized by a Gaussian noise
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
The Q channel signal is,
Figure pat00076
sign
Quadrature error compensation device of binary phase shift keying system.
The method of claim 3, wherein
remind
Figure pat00077
Is the quadrature error
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
The I digital signal and the Q digital signal,
Equation
Figure pat00078
Lt; / RTI >
E b is energy per bit, and θ m has -π or π depending on the transmission bit,
Figure pat00079
Is a quadrature error, and N I and N Q are noise variables.
Quadrature error compensation device of binary phase shift keying system.
The method of claim 5, wherein
The N I and N Q have an average of zero and a variance of
Figure pat00080
, Correlation coefficient
Figure pat00081
A bivariate Gaussian distribution with
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
The average value,
Equation
Figure pat00082
Obtained by
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
Wherein,
Equation
Figure pat00083
To obtain a new binary phase shift keying signal
Quadrature error compensation device of binary phase shift keying system.
The method of claim 8,
The new binary phase shift keying signal is a signal in which the major axis direction of the elliptic contour is changed by 90 degrees.
Quadrature error compensation device of binary phase shift keying system.
The method of claim 1,
The predetermined determination criterion is
Equation
Figure pat00084
Characterized by
Quadrature error compensation device of binary phase shift keying system.
Multiplying the received signal in the Gaussian channel environment by the I-channel signal,
Multiplying the received signal by a Q channel signal;
Outputting an I digital signal by filtering an output signal that is multiplied by the I channel signal;
Outputting a Q digital signal by filtering an output signal of the multiplication process with the Q channel signal;
Sampling the Q digital signal over time to calculate an average value;
Converting the I digital signal and the average value;
Selecting a phase corresponding to a transmission bit according to a predetermined criterion for the conversion result of the I digital signal and the average value;
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The received signal is,
Equation
Figure pat00085
Lt; / RTI >
E b is energy per bit, T is time interval of bits,
Figure pat00086
Is the carrier,
Figure pat00087
Is the transmission phase angle of each bit,
Figure pat00088
Means that the mean is zero and the variance is
Figure pat00089
Characterized by a Gaussian noise
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The Q channel signal is,
Figure pat00090
sign
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 13,
remind
Figure pat00091
Is the quadrature error
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The I digital signal and the Q digital signal,
Equation Lt; / RTI >
E b is energy per bit, and θ m has -π or π depending on the transmission bit,
Figure pat00093
Is a quadrature error, and N I and N Q are noise variables.
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 15,
The N I and N Q have an average of zero and a variance of
Figure pat00094
, Correlation coefficient
Figure pat00095
A bivariate Gaussian distribution with
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The average value,
Equation
Figure pat00096
Obtained by
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The conversion process,
Equation
Figure pat00097
Obtaining a new binary phase shift keying signal by
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 18,
The new binary phase shift keying signal is a signal in which the major axis direction of the elliptic contour is changed by 90 degrees.
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
The method of claim 11,
The predetermined determination criterion is
Equation
Figure pat00098
Characterized by
Quadrature Error Compensation Method of Binary Phase Shift Keying System.
KR1020100130189A 2010-12-17 2010-12-17 Method and apparatus for providing quadrature error correction in binary phase shift keying KR20120068527A (en)

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