CN101582872A - Method for correcting amplitude and phase deviation of OFDM receiver - Google Patents

Abstract

The invention provides a method for correcting the amplitude and phase deviation of an OFDM receiver. A baseband of the OFDM receiver carries out corresponding statistical operation on an I path and a Q path of received pilot signals to estimate an amplitude deviation and a phase deviation; and the compensation of the amplitude deviation and the phase deviation is carried out on the estimated amplitude deviation and the estimated amplitude deviation. The invention adopts the statistical characters of the pilot signals to calculate the amplitude deviation and the phase deviation, thereby having the characteristics of simple operation and little amount of calculation, obtaining the advantages of small scale of circuit and low power consumption on the circuit design and use.

Description

A kind of OFDM receiver method for correcting amplitude and phase deviation

Technical field

The present invention relates to communication technical field, particularly a kind of OFDM (OrthogonalFrequency Division Multiplexing, OFDM) receiver method for correcting amplitude and phase deviation.

Background technology

In zero intermediate frequency reciver based on the wireless communication system of orthogonal frequency division multiplex OFDM technology, in wideband wireless local area network communication system based on IEEE802.11a or HiperLAN2 standard, since the signal on I road that local oscillator produces in the radio-frequency transmitter circuit and Q road thereby can not to keep be completely orthogonally can produce I, Q two-way unbalance phase deviation, the signal on same I road and Q road respectively the gain of the filter of process and amplifying circuit can not to keep be identical, thereby can produce I, the unbalanced amplitude error of Q two-way.This imbalance of amplitude and phase deviation will have a strong impact on the function of system in zero intermediate frequency reciver.The received signal that comprises amplitude and phase deviation can be represented with following formula:

Being write as equation is:

K wherein _ErrWith

Be respectively amplitude error, x (k), y (k) ideal signal for receiving, x ' are (k), y ' is (k) for receiving the signal of band deviation.

At present, the detection method of amplitude and phase deviation, generally have following two tangible problems: (1) adds the uneven testing circuit of amplitude and phase deviation at radio-frequency front-end, this method increases the detection and the correction circuit of amplitude and phase deviation respectively at the transmitter and receiver end, utilize the sine or the cosine signal test of single carrier then and revise the amplitude and phase deviation that the radio-frequency front-end local oscillator causes, but this method need increase the scale and the implementation complexity of radio circuit; (2) adopt the algorithm of sef-adapting filter in base band, this algorithm at first utilizes the coefficient of known training symbol calculating filter, eliminate the image frequency interference signal that causes by amplitude and phase deviation with filter then, but this method amount of calculation is big, realizes complex circuit designs.

Summary of the invention

The objective of the invention is to, a kind of OFDM receiver method for correcting amplitude and phase deviation is provided, have the few characteristics of computing simple computation amount, make circuit scale little, low in energy consumption.

OFDM receiver method for correcting amplitude and phase deviation of the present invention, wherein, OFDM receiver base band is carried out corresponding statistical calculation with the I road of the pilot signal that receives and Q road and is estimated amplitude error and phase deviation, utilizes the amplitude error and the phase deviation that estimate to carry out the compensation of amplitude error and phase deviation then.

Wherein, described I road and Q road with the pilot signal that receives carried out corresponding statistical calculation and estimated amplitude error k _ErrAnd phase deviation

Comprise the following steps:

Steps A: the I road of statistical computation reception pilot signal, Q road signal absolute value adds up and S respectively _I, S _Q

Step B: statistical computation pilot signal I road and Q road product of signals S _{I, Q}

Step C: the I road signal that statistical computation receives pilot signal square adds up and S _{I, I}

Step D: with adding up and S of the Q road signal absolute value in the described steps A _QDivided by adding up and S of I road signal absolute value _I, obtain the amplitude error estimated value $1/k_{\mathrm{est}}=\frac{S_Q}{S_I};$ The I road signal that receives pilot signal with obtaining among the described step B square adds up and S _{I, I}Square add up and S divided by the I road signal that receives pilot signal _{I, I}, obtain the phase deviation estimated value $P_{\mathrm{est}}=\frac{S_{I,Q}}{S_{I,I}}.$

Wherein, in the described steps A, the adding up and S of pilot signal I road signal absolute value _IThe statistical computation formula be:

$S_I=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|x^{\′}\left(k\right)\right|$

Wherein, x ' (k) is the signal of the band deviation that receives.

Wherein, in the described steps A, the adding up and S of pilot signal Q road signal absolute value _QThe statistical computation formula be:

$S_Q=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|y^{\′}\left(k\right)\right|$

Wherein, y ' (k) is the signal of the band deviation that receives.

Wherein, among the described step B, pilot signal I road and Q road product of signals S _{I, Q}The statistical computation formula be:

$S_{I,Q}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·y^{\′}\left(k\right)]$

Wherein, x ' (k), y ' (k) is the signal of the band deviation that receives.

Wherein, among the described step C, the I road signal of pilot signal square adds up and S _{I, I}The statistical computation formula be:

$S_{I,I}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·x^{\′}\left(k\right)]$

Wherein, x ' (k), y ' (k) is the signal of the band deviation that receives.

Wherein, the amplitude error that estimates of described utilization and the phase deviation compensation computing formula of carrying out amplitude error and phase deviation is $\left\{\begin{array}{c}{x}^{\′\′}\left(k\right)=\frac{x^{\′}\left(k\right)}{k_{\mathrm{est}}}\\ y^{\′\′}\left(k\right)=\frac{P_{\mathrm{est}}}{k_{\mathrm{est}}}{x}^{\′}\left(k\right)+y^{\′}\left(k\right)\end{array}\right.$

Wherein, x " (k), y " (k) be the compensation after signal.

The invention has the beneficial effects as follows: according to OFDM receiver method for correcting amplitude and phase deviation of the present invention, owing to adopted the statistical property calculating amplitude and the phase deviation of pilot signal to have the few characteristics of computing simple computation amount, thereby can obtain advantage in circuit design, the use, promptly circuit scale is little, low in energy consumption.

Description of drawings

Fig. 1 utilizes long training symbol to carry out the schematic diagram of amplitude and phase deviation detection frequently and compensation;

Fig. 2 is that amplitude and phase deviation detects and the implementation method schematic diagram.

Embodiment

Below, 1～2 describe OFDM receiver method for correcting amplitude and phase deviation of the present invention in detail with reference to the accompanying drawings.

Core concept of the present invention is: OFDM receiver base band is estimated amplitude error k with the signal that receives by the statistical calculation on I road and Q road _ErrAnd phase deviation

Utilize the k that estimates then _ErrWith Carry out the compensation of amplitude error and phase deviation.Wherein, the OFDM wireless communication system that is applicable to IEEE802.11a, IEEE802.11g and IEEE802.16d of the present invention.

Particularly, this method comprises the steps:

Step 100: after receiver receives frequency pilot sign, utilize frequency pilot sign calculate to receive the adding up and be of I road signal absolute value of pilot signal:

$S_I=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|x^{\′}\left(k\right)\right|---\left(1\right)$

Step 200: the adding up and be of Q road signal absolute value that calculate to receive pilot signal:

$S_Q=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|y^{\′}\left(k\right)\right|---\left(2\right)$

Step 300: calculate to receive adding up and being of the I road of pilot signal and Q road product of signals

$S_{I,Q}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·y^{\′}\left(k\right)]---\left(3\right)$

Step 400: the I road signal that calculate to receive pilot signal square adds up and is

$S_{I,I}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·x^{\′}\left(k\right)]---\left(4\right)$

Step 500: utilize formula (1) formula and formula (2) to be divided by to obtain the amplitude error estimated value to be

$1/k_{\mathrm{est}}=\frac{S_Q}{S_I}---\left(5\right)$

Step 600: utilize formula (3) formula and formula (4) to be divided by to obtain the phase deviation estimated value to be

$P_{\mathrm{est}}=\frac{S_{I,Q}}{S_{I,I}}---\left(6\right)$

According to prior art as can be known, the compensating signal that receives is:

With writing as equation form after formula (7) expansion be:

Rule of thumb the unbalanced phase deviation in I road Q road is generally less than 10 °, therefore, obtains following formula:

Respectively the estimated value k of amplitude and phase deviation _EstAnd P _EstBring formula (8) into, the signal after the compensation is

$\left\{\begin{array}{c}{x}^{\′\′}\left(k\right)=\frac{x^{\′}\left(k\right)}{k_{\mathrm{est}}}\\ y^{\′\′}\left(k\right)=\frac{P_{\mathrm{est}}}{k_{\mathrm{est}}}{x}^{\′}\left(k\right)+y^{\′}\left(k\right)\end{array}\right.---\left(10\right)$

Wherein, x " (k), y " is a signal after the compensation (k), and what formula (5) calculated is the inverse of amplitude imbalance error, and therefore direct division arithmetic of multiplying replacement in the compensation of formula (10) can reduce the scale of hardware circuit design like this.

For the wideband wireless local area network communication system based on IEEE802.11a or HiperLAN2 standard, Fig. 1 carries out the schematic diagram of amplitude and phase deviation detection frequently and compensation for utilizing long training symbol; As shown in Figure 1, be that the short sequence (Short Preamble) of 16 clocks, 2 length long sequence (LS1 and LS2) that is 64 clocks, intervening sequence (GI) and signal and the data etc. that length is 32 samplings are formed by 10 length.At receiving terminal, carry out I, the detection of Q two-way imbalance of amplitude and phase and compensation with long sequence.Statistical property according to long sequence LS1 (LS2) according to above-mentioned algorithm, can realize with sequential chart as shown in Figure 1.Fig. 2 is that amplitude and phase deviation detects and the implementation method schematic diagram.Can have in the realization of side circuit with the input signal statistical calculation is the digital means of feature.

In sum, according to OFDM receiver method for correcting amplitude and phase deviation of the present invention, owing to adopted such scheme promptly to adopt the statistical property calculating amplitude and the phase deviation of pilot signal to have the few characteristics of computing simple computation amount, thereby can obtain advantage in circuit design, the use, promptly circuit scale is little, low in energy consumption etc.

More than be in order to make those of ordinary skills understand the present invention; and to detailed description that the present invention carried out; but can expect; in the scope that does not break away from claim of the present invention and contained, can also make other variation and modification, these variations and revising all in protection scope of the present invention.

Claims (7)

1. OFDM receiver method for correcting amplitude and phase deviation, it is characterized in that, OFDM receiver base band is carried out corresponding statistical calculation with the I road of the pilot signal that receives and Q road and is estimated amplitude error and phase deviation, utilizes the amplitude error and the phase deviation that estimate to carry out the compensation of amplitude error and phase deviation then.

2. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 1 is characterized in that, described I road and Q road with the pilot signal that receives carried out corresponding statistical calculation and estimated amplitude error k _ErrAnd phase deviation

Comprise the following steps:

Steps A: the I road of statistical computation reception pilot signal, Q road signal absolute value adds up and S respectively _I, S _Q

Step B: statistical computation pilot signal I road and Q road product of signals S _{I, Q}

Step C: the I road signal that statistical computation receives pilot signal square adds up and S _{I, I}

Step D: with adding up and S of the Q road signal absolute value in the described steps A _QDivided by adding up and S of I road signal absolute value _I, obtain the amplitude error estimated value $1/k_{\mathrm{est}}=\frac{S_Q}{S_I};$ The I road signal that receives pilot signal with obtaining among the described step B square adds up and S _{I, I}Square add up and S divided by the I road signal that receives pilot signal _{I, I}, obtain the phase deviation estimated value $P_{\mathrm{est}}=\frac{S_{I,Q}}{S_{I,I}}.$

3. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 2 is characterized in that, in the described steps A, and the adding up and S of pilot signal I road signal absolute value _IThe statistical computation formula be:

$S_I=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|x^{\′}\left(k\right)\right|$

Wherein, x ' (k) is the signal of the band deviation that receives.

4. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 3 is characterized in that, in the described steps A, and the adding up and S of pilot signal Q road signal absolute value _QThe statistical computation formula be:

$S_Q=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\left|y^{\′}\left(k\right)\right|$

Wherein, y ' (k) is the signal of the band deviation that receives.

5. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 4 is characterized in that, among the described step B, and pilot signal I road and Q road product of signals S _{I, Q}The statistical computation formula be:

$S_{I,Q}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·y^{\′}\left(k\right)]$

Wherein, x ' (k), y ' (k) is the signal of the band deviation that receives.

6. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 5 is characterized in that, among the described step C, the I road signal of pilot signal square adds up and S _{I, I}The statistical computation formula be:

$S_{I,I}=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[x^{\′}\left(k\right)\·x^{\′}\left(k\right)]$

Wherein, x ' (k), y ' (k) is the signal of the band deviation that receives.

7. OFDM receiver method for correcting amplitude and phase deviation as claimed in claim 6 is characterized in that the compensation computing formula that amplitude error that described utilization estimates and phase deviation are carried out amplitude error and phase deviation is

$\left\{\begin{array}{c}{x}^{\′\′}\left(k\right)=\frac{x^{\′}\left(k\right)}{k_{\mathrm{est}}}\\ y^{\′\′}\left(k\right)=\frac{P_{\mathrm{est}}}{k_{\mathrm{est}}}{x}^{\′}\left(k\right)+y^{\′}\left(k\right)\end{array}\right.$

Wherein, x " (k), y " (k) be the compensation after signal.

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