JP2008263585A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect and correct a phase deviation and an amplitude deviation that occur when performing quadrature detection on a received signal in accordance with a direct detection scheme, through digital signal processing. <P>SOLUTION: A pilot replica signal P<SB>rep</SB>constituted of a real part (in-phase) P<SB>r</SB>and an imaginary part (quadrature) P<SB>i</SB>generated by a phase and amplitude deviation correction processing section 12 is quadrature-modulated into RF band by multiplication circuits 16, 15 and a combination circuit 14 and combined with a received signal R<SB>RF</SB>of RF band by a combination circuit 13. The combined signal is quadrature-detected in accordance with a direct detection scheme by frequency converting circuits 3, 4 and LPF 7, 8 and an in-phase components (I<SB>0</SB>, S<SB>r</SB>) and quadrature components (Q<SB>0</SB>, S<SB>i</SB>) thereof are AD-converted by AD conversion circuits 9, 10, respectively, and supplied to the phase and amplitude deviation correction processing section 12. At the phase and amplitude deviation correction processing section 12, a correction value of the phase and amplitude deviation is created from the real part S<SB>r</SB>and the imaginary part S<SB>i</SB>of the AD-converted pilot replica signal and this value is used to correct the phase and amplitude deviation of the in-phase signal I<SB>0</SB>and the quadrature signal Q<SB>0</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a receiver that quadrature-detects a received signal, and in particular, corrects a phase deviation and an amplitude deviation generated in a quadrature-detected received signal when the quadrature-detected received signal is digitally processed. The present invention relates to a direct detection receiver.

  Receives RF (Radio Frequency) band wideband quadrature modulation signal, which is a real signal, and uses it as a zero IF system (a system that performs quadrature demodulation (orthogonal detection) of RF band received signal directly to baseband signal) There is known a receiver that directly quadrature-demodulates a signal near the baseband using a direct detection method such as a low-IF method (a method that orthogonally demodulates a received signal in the RF band to a signal near the baseband) (for example, a patent Reference 1).

  FIG. 7 is a block diagram showing a general configuration of a receiver that performs quadrature demodulation on the RF reception signals of the in-phase signal I and the quadrature signal Q that have been subjected to quadrature modulation by the zero IF method or the low IF method (hereinafter referred to as zero IF method or the like). 1 is a BPF (band pass filter), 2 is an LNA (low noise amplifier), 3 and 4 are frequency conversion circuits (mixers and multipliers), 5 is a local oscillator, 6 is a 90 ° phase shifter, 7 and 8 are LPFs (low-pass filters), 9 and 10 are AD (analog / digital) conversion circuits, and 11 is a baseband demodulator.

  In the figure, the BPF 1 uses a required frequency band as a pass band, and an attenuation amount is set outside the required frequency band, whereby the in-phase signal I and the quadrature signal Q in the required frequency band (RF band) are set. Is extracted by orthogonal modulation. The received signal is supplied to the frequency conversion circuits 3 and 4 after being subjected to low noise amplification processing at a required amplification degree by the LNA 2.

  In the frequency conversion circuit 3, the received signal in the RF band is subjected to frequency conversion (multiplication) processing with the output signal of the local oscillator 5, and the output signal of the frequency conversion circuit 3 is supplied to the LPF 7, whereby the carrier of the RF received signal is obtained. The frequency component of the sum of the frequency and the frequency of the output signal of the local oscillator 5 is attenuated, and the in-phase signal I which is the frequency component of the difference between these frequencies is obtained. Here, the frequency of the output signal of the local oscillator 5 is set to be equal to the carrier frequency of the RF reception signal (having a predetermined offset in the case of the low IF method). The LPF 7 has a pass bandwidth corresponding to the bandwidth of one carrier in the vicinity of 0 Hz, and a frequency component twice the frequency of the output signal of the local oscillator 5 is attenuated from the output signal of the frequency conversion circuit 3. A baseband in-phase signal I is output from the LPF 7.

  Further, the output signal of the local oscillator 5 is phase shifted by 90 ° by the 90 ° phase shifter 6. In the frequency conversion circuit 4, the received signal in the RF band from the LNA 2 is frequency-converted (multiplied) with the output signal of the 90 ° phase shifter 6, and the output signal of the frequency conversion circuit 4 is supplied to the LPF 8. The frequency component of the sum of the carrier frequency of the RF reception signal and the frequency of the output signal of the 90 ° phase shifter 6 is attenuated, and an orthogonal signal Q which is the frequency component of the difference between these frequencies is obtained. Here, since the frequency of the output signal of the 90 ° phase shifter 6 is also equal to the carrier frequency of the RF reception signal, the LPF 8 doubles the frequency of the output signal of the 90 ° phase shifter 6 from the output signal of the frequency conversion circuit 4. And the baseband quadrature signal Q is output from the LPF 8.

  In this way, the received signal in the RF band is quadrature demodulated by the frequency conversion circuits 3 and 4 by the direct detection method using the output signals of the local oscillator 5 and the 90 ° phase shifter 6, and is based on the LPFs 7 and 8, respectively. In-band signal I and quadrature signal Q of the band are obtained.

  The baseband in-phase signal I and the quadrature signal Q output from the LPFs 7 and 8 are both analog signals, which are converted into digital signals by the AD conversion circuits 9 and 10 and then sent to the baseband demodulation unit 11. The signal is supplied and demodulated by digital signal processing to obtain a demodulated output.

  By the way, when a wideband received signal is demodulated by the direct detection method as described above, there is a problem that a phase deviation or an amplitude deviation occurs in the demodulated signal.

  In particular, in the case of a received signal by the orthogonal frequency division multiplexing (OFDM) system (hereinafter referred to as OFDM signal), such a problem is great when the direct detection system is used. That is, an OFDM signal is obtained by RF-modulating a large number of subcarriers arranged at fixed frequency intervals orthogonal to each other in a specific discrete Fourier transform window based on the corresponding in-phase signal I and quadrature signal Q, respectively. It takes the form. For this reason, each subcarrier of the OFDM signal has subcarriers arranged on the left and right sides with a center subcarrier (DC subcarrier) as the center on the frequency axis.

That is, in this RF signal, the angular frequency ω _n of the n-th (where n =..., −2, −1, 0, 1, 2,...) Frequency component subcarrier is the DC component subcarrier. If the angular frequency is ω ₀ and the angular frequency difference between adjacent subcarriers is Δω,
ω _n = ω ₀ + n · Δω
However, Δω is each frequency corresponding to the subcarrier interval.

When such an RF signal is detected as a baseband signal using the above-described zero IF method or the like, the frequency component of the subcarrier of the angular frequency (ω ₀ + n · Δω) is the frequency of the subcarrier of the positive angular frequency (n · Δω). The frequency component of the subcarrier having the angular frequency (ω ₀ −n · Δω) detected by the component is detected to the frequency component of the subcarrier having the negative angular frequency (−n · Δω). However, there is a gain variation (amplitude deviation) between the in-phase signal I and the quadrature signal Q and an orthogonal error (phase deviation) between the in-phase signal I and the quadrature signal Q when performing quadrature demodulation. Then, a component having an inverted angular frequency is generated. As a result, a subcarrier having a positive angular frequency (n · Δω) leaks to a negative angular frequency (−n · Δω), and a subcarrier having a negative angular frequency (−n · Δω) is positive. Leaking into Δω), these frequency components interfere with each other.

  Methods for correcting such phase deviation and amplitude deviation are roughly divided into a method (1) in which such deviation is detected and corrected entirely by analog processing, and such deviation is detected by digital signal processing. And a method (2) for performing correction by using digital signal processing and a method (3) for performing detection and correction of such deviation by digital signal processing.

  As a method (1) for all analog processing, in FIG. 7, phase deviation and amplitude deviation are detected and corrected for the in-phase signal I and the quadrature signal Q immediately before being input to the AD conversion circuits 7 and 8. (For example, see FIG. 1 of Patent Document 2).

  Further, as a method (2) of detecting a deviation by digital signal processing and performing correction using an analog circuit (that is, by analog signal processing), in-phase output from the AD conversion circuits 7 and 8 in FIG. The signal I and the quadrature signal Q are used to detect a phase deviation and an amplitude deviation. The in-phase signal I and the quadrature signal Q immediately before being input to the AD conversion circuits 7 and 8 are detected using feedback control or the like. Correction is performed (see, for example, FIG. 3 of Patent Document 1).

  Further, as a method (3) for detecting deviation and correcting it entirely by digital signal processing, the digital in-phase signal I and quadrature signal Q output from the AD conversion circuits 7 and 8 in FIG. A phase deviation and an amplitude deviation are detected, and based on the detection result, these deviations are corrected for the digital in-phase signal I and quadrature signal Q output from the AD conversion circuits 7 and 8 (for example, And Patent Document 3).

  FIG. 8 is a block diagram schematically showing the configuration of the method (3). Reference numeral 12 denotes a phase and amplitude deviation correction processing unit. The same reference numerals are given to the portions corresponding to those in FIG. Omitted.

In the figure, a digital in-phase signal I and a quadrature signal Q output from the AD conversion circuits 7 and 8 are supplied to a phase and amplitude deviation correction processing unit 12. The phase and amplitude deviation correction processing unit 12 detects a phase deviation and an amplitude deviation from the supplied in-phase signal I and quadrature signal Q, and based on the detection result, these supplied in-phase signal I and Correction processing of the phase deviation and amplitude deviation of the orthogonal signal Q is performed. The corrected in-phase signal I and quadrature signal Q are supplied to the baseband demodulator 11 and demodulated by digital signal processing.
JP-A-9-247228 JP 2005-217934 A JP 2000-216839 A JP 2004-278750 A

  In the conventional method (1), which is all analog processing, the object to be detected and corrected for the phase deviation and the amplitude deviation is an analog signal. Therefore, a circuit for detection, in particular, a device for accurately detecting the phase deviation is required. Even if it is assumed that it does not exist in a practical range and that the phase deviation can be detected accurately, the correction means is practically a means that can be corrected accurately in the analog circuit processing. It is very difficult to obtain. In addition, there is a problem that detection and correction cannot be performed accurately due to errors in analog circuit components, and adjustment errors are limited due to component errors.

  In the method (2) in which the deviation is detected by digital signal processing and correction is performed using an analog circuit, phase deviation and amplitude deviation can be detected with high accuracy. However, the correction of deviation by analog signal processing is performed as described above. Similar to method (1), it is difficult to carry out with high accuracy.

  The method (3) in which the deviation detection and correction shown in FIG. 8 are all performed by digital signal processing is the above three methods as long as the phase deviation and the amplitude deviation can be detected without being affected by component errors. This is the most effective method.

  However, the in-phase signal I and the quadrature signal Q that are received and obtained from the AD conversion circuits 7 and 8 are generally not known signals, and are not known from the in-phase signal I and the quadrature signal Q. It is difficult to accurately detect the deviation. On the other hand, when multi-level modulation such as 64QAM is used as the subcarrier modulation scheme, it is desirable that the phase deviation and amplitude deviation be 0.1 degrees or less and 0.1 dB or less, respectively.

  The present invention solves such a problem, and detects the phase deviation and amplitude deviation of the received signal orthogonally detected by the direct detection method with high accuracy by digital signal processing while performing normal reception. An object of the present invention is to provide a phase and amplitude deviation correction circuit capable of accurately correcting an amplitude deviation.

  In order to achieve the above object, the present invention provides frequency conversion means for performing quadrature detection on a received signal obtained by quadrature modulation of an in-phase signal and a quadrature signal by direct detection, and AD conversion of the output signal of the frequency conversion means A phase and amplitude deviation correction processing method for a receiver, comprising: an AD converting means that performs the above-mentioned processing, and a demodulating means that digitally processes and demodulates the digital in-phase signal and quadrature signal output from the AD converting means. Phase and amplitude deviation correction processing processing means for generating a pilot replica signal, and quadrature modulation means for quadrature modulating the pilot replica signal using a local oscillator of the frequency conversion means or an output signal of a 90 ° phase shifter And a synthesizing unit that synthesizes the output signal of the quadrature modulation unit with the received signal and supplies the synthesized signal to the frequency conversion unit, and receives the quadrature modulated pilot replica signal Together with the signal, quadrature detection by the frequency conversion means, AD conversion and supply to the phase and amplitude deviation correction processing processing means, the phase and amplitude deviation correction processing means, the generated pilot replica signal and the frequency conversion means Is generated in analog means such as the frequency conversion means for the in-phase signal and the quadrature signal of the received signal that has been frequency converted and AD converted by arithmetic processing with the pilot replica signal that has been frequency converted and AD converted by A correction value for correcting the phase and amplitude deviation obtained is obtained, the in-phase signal and the quadrature signal of the received signal subjected to frequency conversion and AD conversion using the correction value are subjected to digital signal processing, and the in-phase signal is processed. And the quadrature signal and the phase deviation are corrected and supplied to the demodulating means.

  Further, as another means for realizing the present invention, frequency conversion for performing quadrature detection using a direct detection method on a received signal obtained by quadrature modulation of an in-phase signal and a quadrature signal including a pilot signal having a predetermined time length every predetermined time. Means, AD converting means for AD converting the output signal of the frequency converting means, and the digital in-phase signal and quadrature signal output from the AD converting means using the pilot signal in the channel estimation processing means A phase and amplitude deviation correction processing method of a receiver comprising a demodulating means for performing digital signal processing and demodulating after performing channel estimation processing, wherein the digital in-phase signal output from the AD converting means and Phase and amplitude deviation correction processing means for supplying an orthogonal signal and the pilot signal included in the received signal used for the channel estimation processing are provided, and the amplitude deviation is provided. The normal processing processing means includes pilot signal generating means for generating a pilot signal having the same angular frequency as the pilot signal included in the received signal orthogonally detected by the frequency converting means, and the generated pilot signal and the channel Phase and amplitude deviation caused by analog means such as the frequency conversion means between the in-phase signal and the quadrature signal of the received signal that has been frequency-converted and AD-converted by arithmetic processing with the pilot signal from the estimation processing means Correction signal is obtained, digital signal processing is performed on the in-phase signal and the quadrature signal of the received signal that have been frequency-converted and AD-converted using the correction value, and the in-phase signal and the quadrature signal The channel estimation processing means performs channel estimation processing on the in-phase signal and the quadrature signal with the phase and amplitude deviation corrected. And it is characterized in Ukoto.

  Further, the present invention provides the direct detection receiver according to claim 1 or 2, wherein the received signal is a signal of an orthogonal frequency division multiplexing system, and the received signal that has been subjected to the orthogonal detection and AD converted is represented by a symbol. FFT processing means for converting from the time domain to the frequency domain in units, and detecting a pilot signal for propagation path estimation processing from the output of the FFT processing means, calculating a deviation of one or both of the phase and amplitude, and including integration A phase or amplitude correction unit that performs correction via a feedback control loop and then outputs to the demodulation unit, and the phase or amplitude correction unit performs different corrections according to the subcarrier frequency. Direct detection receiver.

  According to the present invention, since the phase and amplitude deviation caused by an analog circuit such as a frequency conversion means when quadrature detection of a received signal can be detected and corrected by digital signal processing, there is no influence of the analog circuit on the detection. Therefore, detection with high accuracy is possible, and therefore correction can be performed with high accuracy.

  As shown in FIG. 8, the present invention basically uses a method (3) in which detection and correction of phase deviation and amplitude deviation are all performed by digital signal processing. Alternatively, these deviations can be detected with high accuracy using a pilot signal injected on the receiving side.

  First, the principle of detection and correction of phase deviation and amplitude deviation in the phase and amplitude deviation correction processing unit 12 of the present invention will be described with reference to FIG.

Now, the RF band received signal R _RF supplied to the frequency conversion circuits 3 and 4 is set to x (t) = cos (ω _c t + θ) by paying attention to an arbitrary angular frequency ω _c , and the local oscillator 5 The output signal is cos (ω _c ′ t), which is a single frequency signal with an angular frequency ω _c ′, the phase angle of the 90 ° phase shifter 6 is 90 ° + Δφ, and the frequency conversion circuits 3 and 4 and thereafter. Let g be the amplitude deviation between the generated in-phase signal I and quadrature signal Q. However, θ is an arbitrary phase. Further, it is assumed that the average value of the in-phase signal I and the quadrature signal Q of the received signal x (t) is normalized to 1 on the transmission side.

At this time, the in-phase signal I and the quadrature signal Q respectively obtained from the frequency conversion circuits 3 and 4 are expressed as a real part and an imaginary part of the following expression.
cos (ω _c t + θ) · [cos (ω _c 't) −jgsin (ω _c ' t + Δφ)]
If the above equation is arranged and the signal of the angular frequency (ω _c ′ + ω _c ) removed by the LPFs 7 and 8 is ignored, the in-phase signal I _O and the quadrature signal Q of the baseband signal R _BB obtained from the LPFs 7 and 8 respectively. _O is represented by the following formula.
R _BB = (1/2) cos {(ω _c '−ω _c ) t + θ}
-J (1/2) g [sin {([omega] _c '-[omega] _c ) t + [Delta] [phi]-[theta]}] (1)

In the above equation (1), if ω _c ′ = ω _c , paying attention to the received signal converted into direct current (the zero IF method is taken as an example, but it can be similarly realized in the low IF method), the above equation (1) ) Becomes the following equation (2).
R _BB = (1/2) cosθ−j (1/2) gsin {Δφ−θ} (2)
= (1/4) · (e ^jθ + e ^−jθ ) − (1/4) · g {e ^{j (Δφ−θ)} −e ^{−j (Δφ−θ)} }
^{= (1/4) · e jθ {} 1 + ge -jΔφ} + (1/4) · e -jθ {1-ge jΔφ} ...... (3)
= (1/4) · e ^jθ [1 + g {cos (Δφ) −jsin (Δφ)]
+ (1/4) · e ^−jθ [1-g {cos (Δφ) + jsin (Δφ)] (4)
= Ae ^jθ + Be ^-jθ (5)
However,
A = A _r + jA _i
= (1/4) · [1 + g {cos (Δφ) −jsin (Δφ)}],
B = B _r + jB _i
= (1/4) · [1-g {cos (Δφ) + jsin (Δφ)}] (6)
It is defined as Ae ^jθ means an original component (desired wave component) of the signal of interest x (t), and Be ^−jθ means an unnecessary component (image) derived from the phase / amplitude deviation.

If the above equation (5) is arranged by cos θ and sin θ,
R _BB = (A _r + jA _i ) e ^jθ + (B _r + jB _i ) e ^−jθ
= A _r (cos θ + j sin θ) + j A _i (cos θ + j sin θ) + B _r (cos θ−j sin θ) + jB _i (cos θ−j sin θ)
= (A _r + B _r ) cos θ + (− A _i + B _i ) sin θ + j (A _i + B _i ) cos θ + j (A _r −B _r ) sin θ (7)
It becomes. here,
(A _r + B _r ) = U ₁₁ , (−A _i + B _i ) = U ₁₂
, (A _i + B _i ) = U ₂₁ , (A _r −B _r ) = U ₂₂ (8)
Then, the above equation (5) becomes
R _BB = U ₁₁ cos θ + U ₁₂ sin θ + jU ₂₁ cos θ + jU ₂₂ sin θ (9)

The real part and the imaginary part of the equation (9) are the in-phase signal (I _o = U ₁₁ cos θ + U ₁₂ sin θ) from the frequency conversion circuit 3 when the phase deviation is (Δφ) and the amplitude deviation is g, and the frequency This is the quadrature signal from the conversion circuit 4 (Q _o = U ₂₁ cos θ + U ₂₂ sin θ).

Without phase deviation Δφ and amplitude deviation g, true in-phase signal I _i and quadrature signal Q _i when quadrature demodulation of signal of interest x (t) = cos (ω _c t + θ) should be cos θ and sin θ, respectively. Therefore, if the above equation (9) is expressed in a matrix as cos θ → I _i and sin θ → Q _i ,
It becomes. here,
U ₁₁ = A _r + B _r
= (1/4) {1 + gcos (Δφ)} + (1/4) {1−gcos (Δφ)} = 1/2,
U ₁₂ = (− A _i + B _i )
= − (1/4) {− sin (Δφ)} + (1/4) sin (Δφ) = j (1/2) · sin (Δφ),
U ₂₁ = (A _i + B _i )
= (1/4) {-sin (Δφ)} + (1/4) sin (Δφ) = 0
, U ₂₂ = A _r −B _r
= (1/4) {1 + gcos (Δφ)} − (1/4) {1−gcos (Δφ)} = (1/2) gcos (Δφ).

When there is no phase deviation (Δφ = 0) and no amplitude deviation (g = 1), ^t [I _o Q _o ] and ^t [I _i Q _i ] should be connected by a unit matrix, so In order to align, 2 is multiplied by Formula (10).
When there is a phase deviation or amplitude deviation, the deviation is corrected by performing an inverse matrix operation such as the following equation (11) on I _o and Q _o output from the frequency conversion circuits 3 and 4. The

_{However, det = U 11 · U 22} -U 12 · U 21
= (A _r + B _r ) (A _r −B _r ) − (− A _i + B _i ) (A _i + B _i )
= (A _r ² + A _i ² ) − (B _r ² + B _i ² )
= │A│ ² −│B│ ²
It is. In addition, in an actual radio receiver, there is a mechanism that follows the magnitude of a signal that fluctuates due to fading, etc. Compared to that, the influence of det is so small that it can be ignored, so there is no need to implement det division. Is considered 1.

Next, consider a case where a pilot signal having an arbitrary angular frequency ω _p + ω _c is superimposed on the RF band received signal R _RF . Here, it is assumed that ω _p is an angular frequency assigned to one of the sub-carriers in the OFDM band, and a sub-carrier of −ω _p at a symmetric position with respect to the center frequency is unused.
Since θ in the above equation (5) is arbitrary, if θ is replaced with ω _p t + ψ, the baseband received pilot signal P _BB (received phase and amplitude deviation) obtained from LPFs 7 and 8 is It is expressed by the following formula.
P _BB = A · exp [j (ω _p t + ψ)] + B · exp [−j (ω _p t + ψ)]
More generally, if the pilot signal is quadrature modulated with modulated signal M,
P _BB = M · A · exp [j (ω _p t + ψ)] + M ^* · B · exp [−j (ω _p t + ψ)] (13)
It is expressed as Note that a star (*) means a complex conjugate, and M is normalized to 1 for simplicity.
Further, defined as follows the real part and the imaginary part of the received pilot signal P _BB.
P _BB = S _r + jS _i (14)

Here, it is assumed that pilot replica signals P _rep ⁺ and P _rep ⁻ as shown in the following equation can be prepared.
P _rep ⁺ = M · exp [jω _P t] = P _r + jP _i
P _rep ⁻ = M ^* · exp [−jω _P t] = P _r −jP _i (15)
That is, the angular frequency is ω _P substantially equal to that of the pilot signal, and the phase has an arbitrary phase difference ψ that can be regarded as constant.

At this time, the correlation in 1 OFDM symbol time unit between the pilot signal P _BB and both pilot replica signals P _rep ⁺ and P _rep ⁻ is as follows.
<P _BB · P _rep ^->
= <{M · A · exp [j (ω _p t + ψ)] + M ^* · B · exp [−j (ω _p t + ψ)]} · M ^* · exp [−jω _P t]>
= <A · exp (jψ)> + <M ^{* 2} · B · exp [−j (2ω _P t + ψ)]>
= A _r cosψ−A _i sinφ + j (A _r sinφ + A _i cosφ) (16)
<P _BB · P _rep ^+>
= <{M · A · exp [j (ω _p t + ψ)] + M ^* · B · exp [−j (ω _p t + ψ)]} · M · exp [jω _P t]>
= <M ² · A · exp [j (2ω _p t + ψ)]> + <B · exp (−jψ)>
= B _r cosψ + B _i sinψ + j (−B _r sinψ + B _i cosψ) (17)

The correlations <P _BB · P _rep ⁻ > and <P _BB · P _rep ⁺ > are defined as _A˜ and _B˜, respectively.
On the other hand, according to the above formulas (14) and (15), A˜ and B˜ can also be expressed as follows.
_{A ~ = <P BB · P} rep ->
= <(S _r + jS _i ) · (P _r −jP _i )>
_{= <(S r · P r} + S i · P i) + j (S i · P r -S r · P i)> ...... (18)
_{B ~ = <P BB · P} rep +>
_{= <(S r + jS i} ) · (P r + jP i)>
_{= <(S r · P r} -S i · P i) + j (S i · P r + S r · P i)> ...... (19)

When calculating the matrix having the sum of the above formulas (16) and (17), the real part of the difference, and the imaginary part as elements, the following formula is obtained.
That is, the product of the matrix F for correcting the phase and amplitude deviation and the transformation matrix C for coordinate rotation corresponding to the arbitrary phase ψ is obtained.

  Based on the above-described principle, a receiver according to Embodiment 1 of the present invention will be described. The receiver of this example is substantially the same as that shown in FIG. 8 except for the phase and amplitude deviation correction processing unit 12. In the operation of the receiver of this example, it is assumed that the received signal includes a known pilot signal or a reproducible pilot signal.

The phase and amplitude deviation correction processing unit 12 of the first embodiment _applies the in-phase signal I _o and the quadrature signal Q _o of the baseband received signal R _BB from the AD conversion circuits 9 and 10 shown in the above formula (1) to By performing the correction process shown in the above equation (11), the phase deviation and amplitude deviation of these in-phase signal I _o and quadrature signal Q _o are corrected. The matrix F necessary for the correction processing is determined by calculating the above equation (20) for the pilot signal.

FIG. 2 is a block diagram of the phase and amplitude deviation correction processing unit 12 of this example, and includes a pilot signal demodulation processing unit 17, LPFs 18 and 19, multiplication circuits 20 to 23, and addition circuits 24 and 25. .
When the pilot signal demodulation processing unit 17 includes a pilot replica signal generation unit (described later) and receives the reception signal R _{BB including} the reception pilot signal P _BB from the AD conversion circuits 9 and 10, the equation (15) A pilot replica signal P _rep is generated, and the matrix F is output by calculating equation (20) in one OFDM symbol period. That is, the correction values F ₁₁ , F ₁₂ , F ₂₁ , F are obtained by using the real part I _o and imaginary part Q _{o of} the received signal R _BB and the real part P _r and imaginary part P _{i of} the pilot replica signal _Prep. Generates ₂₂ .

The LPFs 18 and 19 are not necessary in the present invention in principle, but are exemplified as an example, and may have a function as a decimation or delay line in addition to a function as a filter. In the description of this example, the outputs of the AD conversion circuits 9 and 10 and the outputs of the LPFs 18 and 19 are referred to as an in-phase signal I _o and a quadrature signal Q _o without particular distinction.

The multiplier 20 multiplies the correction value F ₁₁ and the in-phase signal I ₀ supplied from the LPF 18 and outputs the result.
The multiplier 21 multiplies the correction value F ₁₂ and the orthogonal signal Q ₀ supplied from the LPF 19 and outputs the result.
The multiplier 22 multiplies the correction value F ₂₁ and the in-phase signal I ₀ supplied from the LPF ₁₈ and outputs the result.
The multiplier 23 multiplies the correction value F ₂₂ and the orthogonal signal Q ₀ supplied from the LPF 19 and outputs the result.
The multipliers 20 to 23 operate each time a signal is supplied from the LPF 18 or 19 (that is, at the sample rate).

The adder 24 adds the output signals of the multipliers 20 and 21 and outputs the result as a corrected in-phase signal I _c .
The adder 25 adds the output signals of the multipliers 22 and 23 and outputs the result as a corrected orthogonal signal Q _c .

The processing by the multipliers 20 to 23 and the adders 24 and 25 corresponds to the above equation (11). Note that the signal obtained by the correction is expressed as I _c or the like in order to distinguish it from the true in-phase signal I _i or the like. However, if the correction value is appropriate, both are substantially equal.

Next, calculation of the correction values (F ₁₁ , F ₁₂ , F ₂₁ , F ₂₂ ) by the pilot signal demodulation processing unit 17 will be described. This can be easily obtained by calculating the pilot signal P _BB obtained by demodulation and the pilot replica signal _Prep (Equation 20).

  3 is an internal block diagram of the pilot signal demodulation processing unit 17 in FIG. 2, wherein 26 is a pilot replica signal generation unit, 27 is a real part extraction unit, 28 is an imaginary part extraction unit, 29 to 32 are multiplication circuits, 33 , 34 are sign inversion circuits, and 35 to 38 are LPFs.

The pilot replica signal generation unit 26 includes a CP detection circuit 27 and a modulation pattern generation unit 28, and generates a pilot replica signal P _rep (= P _r + jP _i ).
CP (Cyclic Prefix) detection circuit 27 receives an input of the received signal R _BB baseband from the AD conversion circuit 9 detects the peaks of the autocorrelation of the OFDM symbol length, and outputs the symbol timing.
The modulation pattern generator 28 is a complex signal (that is, a baseband of a modulated subcarrier) obtained by modulating a subcarrier on which a known pilot signal is carried (the frequency is a difference from the center frequency) with the modulation pattern M of the pilot signal. Signal) samples are held as a table for a plurality of OFDM symbols corresponding to the period of the modulation pattern, and the table is read in synchronism with the symbol timing given from the CP detection circuit 27 to obtain the pilot replica signal P _rep Output as.

Actually, even if the product of the transformation matrix C and the matrix F of Ψ which is not 0 is treated as the matrix F, the phase rotation of the angle Ψ occurring in the corrected signals I _c and Q _c is This means that the phase rotation is compensated with respect to the phase, which is not a problem at all.

The multiplier 29 multiplies the real part P _r of the pilot replica signal by the in-phase signal I _o supplied from the AD conversion circuit 9 and outputs the result.
The multiplier 30 multiplies the real part P _r of the pilot replica signal by the in-phase signal Q _o supplied from the AD conversion circuit 10 and outputs the result.
The multiplier 31 multiplies the real part P _i of the pilot replica signal by the in-phase signal I _o supplied from the AD conversion circuit 9 and outputs the result.
The multiplier 32 multiplies the real part P _i of the pilot replica signal by the in-phase signal Q _o supplied from the AD conversion circuit 10 and outputs the result.

The sign inversion circuit 33 inverts the positive / negative sign and outputs the output signal of the multiplier 30.
The sign inverting circuit 34 inverts the positive / negative sign and outputs the output signal of the multiplier 31.
The LPF 35 performs simple addition averaging of the signal supplied from the multiplier 32 for one OFDM symbol, and further averages (low-pass filtering) it for several OFDM symbols as necessary to obtain a correction value F _11. Output.
Each LPF36,37,38, sign inverting circuit 33, the sign inverting circuit 34, it was treated in the same manner as LPF35 signals supplied from the multiplier 29, and outputs the correction value _{F 12, F 21, F 22} .

The signal output from the multiplier 32 and the like includes a component obtained by complex multiplication of R _BB and the pilot replica signal _{Prep in} addition to the reception pilot signal P _BB of interest. However, as long as it is handled in units of OFDM symbols, other subcarriers included in R _BB are orthogonal to the subcarriers of the pilot signal, and thus their average value is zero. That is, Expressions (16) and (17) hold not only for P _BB but also for R _BB including P _BB .

  In pilot replica signal generation unit 26, a constant value may be used as modulation pattern M, and a DC subcarrier having a frequency of 0 may be used as a subcarrier on which a pilot signal is placed. In addition, the pilot replica signal generation unit 26 is not limited to the above-described one, and for example, a subcarrier corresponding to the pilot signal (without FFT) may be orthogonally demodulated and subjected to symbol determination as the pilot replica signal. When the pilot signal is intermittently placed on the subcarrier, the operation of the pilot replica signal demodulation processing unit 17 may be stopped and the same compensation value F may be continuously used when there is no pilot.

In the above description, the phase deviation Δφ and the amplitude deviation g are treated as not depending on the frequency. However, when the band of the received signal R _BB (OFDM signal band) is wide, the frequency dependence thereof cannot be ignored. It may be. In that case, a plurality of subcarriers on which pilot signals are carried may be arranged evenly in the band, and correction values detected using these pilot signals may be averaged and used.

  As described above, in the first embodiment, when the received signal is subjected to quadrature detection by the direct detection method in the frequency conversion circuits 3 and 4 by using the pilot replica signal, the frequency conversion circuits 3 and 4 and the 90 ° phase shift are performed. The phase deviation and amplitude deviation generated in an analog circuit such as the detector 6 can be detected by digital signal processing, and the phase deviation and amplitude deviation can be corrected by digital signal processing. And amplitude deviation can be detected and corrected.

  FIG. 1 is a configuration diagram of a receiver according to Embodiment 2 of the present invention. The receiver of this example is different from the receiver of the first embodiment in that it includes a configuration in which a pilot signal is injected as an analog RF signal into the previous stage of the frequency conversion circuit. The receiver of this example does not assume that a pilot signal is included in the received signal.

The phase and amplitude deviation correction processing unit 41 of the second embodiment is substantially the same as the phase and amplitude deviation correction processing unit 12 of the first embodiment, but the generated pilot replica signal _Prep is used as an analog baseband signal. Has a function to output to the outside.
However, this pilot replica signal P _rep has a value not used for, for example, a subcarrier for data transmission as its angular frequency ω _prep , and has, for example, each frequency of a subcarrier near a DC subcarrier. In addition, the pilot replica signal P is essentially an analysis signal P _rep = P _r + jP _i
It is necessary to represent a, and P _r of the real part (in-phase component), each consisting of the corresponding two real signals in the P _i of the imaginary part (quadrature component). As will be described later, the pilot replica signal P is generated by digital signal processing and is output by a DA converter (not shown) having the same configuration. Therefore, it can be assumed that _Pr and _Pi themselves are orthogonal with sufficient accuracy.

Real part P _r of the pilot replica signal P _rep is multiplied by the output signal of the local oscillator 5 by the multiplier 16, and a real part P _i is the output signal of the multiplier 15 in the 90 ° phase shifter 6 of the pilot replica signal P _rep is multiplied, the output signals of the multipliers 16 and 15 are combined in combining circuit 14, a pilot replica signal P _rep real part P _r and an imaginary part quadrature modulated signal and a P _i to RF band (hereinafter, RF band pilot replica signal) P _RF is obtained. That is, the local oscillator 5, the 90 ° phase shifter 6, the multipliers 15 and 16, and the synthesis circuit 14 constitute a quadrature modulator.
The image component (the frequency component of ω _c −ω _p with respect to each frequency ω _c + ω _{p of the} RF pilot signal) included in the output of the synthesis circuit 14 causes detection errors of the phase and amplitude deviation and is sufficiently suppressed. However, secondary distortion or the like may be bad because its influence is limited.

The RF band pilot replica signal P _RF is combined with the RF band received signal R _RF from the LNA 2 by the combining circuit 13 and supplied to the frequency conversion circuits 3 and 4 as a pilot signal. The pilot signal P _RF is the same manner as in Example 1, there is no need to supply at all times, switching means for cutting off the supply is provided as appropriate.

In the frequency conversion circuits 3 and 4, the combined signal of the RF band received signal R _RF and the RF band pilot signal P _RF is detected by the direct detection method by the output signal of the local oscillator 5 in the same manner as in the past, and the detection output is obtained. By passing the signals through the LPFs 7 and 8, the in-phase signal I and the quadrature signal Q of the baseband composite signal are obtained. These combined signals are converted into digital signals by the AD conversion circuits 9 and 10 and supplied to the phase shift and amplitude deviation correction processing unit 41.

Here, the real part S _r and the imaginary part S _i of the baseband pilot replica signal P _BB output from the LPFs 7 and 8 are similar to the in-phase signal I and the quadrature signal Q of the base band received signal R _BB. In addition, phase deviations and amplitude deviations by analog circuits such as the frequency conversion circuits 3 and 4, the 90 ° phase shifter 6, the LPFs 7 and 8, and an amplifier (not shown) are mixed. The phase and amplitude deviation correction processing unit 41 detects the phase deviation and amplitude deviation from the real part S _r and the imaginary part S _{i of the} baseband pilot replica signal P _BB , and supplies them based on the detection result. phase signal I of the received signal R _BB baseband, for correcting the phase deviation and amplitude deviation in an orthogonal signal Q.

By the way, initially, in the explanation of the principle of the present invention, it is assumed that the subcarrier of −ω _p is unused, but the case where this subcarrier is used will be considered.
In simple terms, the correction value F _{11 and the} like may be averaged so that the correlation between the modulation pattern of the subcarrier of the angular frequency −ω _prep and the modulation pattern of the pilot can be regarded as zero. That is, if averaging is performed for a sufficient time, the pilot signal can be set freely regardless of whether the reception signal R _BB is inside or outside the band.
Next, let us consider a case where both subcarriers ω _p and −ω _p can be used for pilot signals, the modulation pattern of both subcarriers is the same (the amplitude is also the same) M, and the phase Ψ is also the same. .
Since Expressions (13) to (20) make ω _p arbitrary and are linear, the superposition theorem holds. Assuming that P _BB ⁻ is an expression obtained by replacing ω _p in Expression (13) with −ω _p , Expression (16) and Expression (17) are obtained by inverting the sign of sinΨ with respect to P _BB ⁻ . When adding together with the initial formulas (16) and (17), only the term of cosΨ remains. As a result, the product CF of the matrix in equation (20) is cos Ψ · F, and the correction value F _{11 and the} like are obtained by the same calculation as in the case of the subcarrier on one side. That is, it is not necessary to use the quadrature modulator as shown in FIG. 1 as a configuration in which the pilot replica signal is up-converted and injected into the front stage of the frequency conversion circuits 3 and 4, and two tones of ω _p and −ω _p are used. The resulting normal mixer may be used. However, since the amplitude and phase of both pilots need to be exactly the same, the pilot in the received signal R _RF that has received the frequency characteristic of the propagation path as in the first embodiment cannot be used, as in this example. Even when injection is performed after reception, the difference between ω _p and −ω _p should be as small as possible to avoid the influence of the frequency characteristics of the mixer.
Note that the gain fluctuation due to cos Ψ can be absorbed by the normal AGC of the radio receiver, as in the determinant of the matrix U. However, since the become cosΨ approximately 0 less sensitive, the phase of one to several OFDM symbols every P _r and P _i alternately enter the mixer the, pilot replica signal to 0 and 90 degrees alternately P _r and P _i may be exchanged when the correction value F ₁₁ becomes smaller than 0.5.

As described above, the receiver according to the second embodiment can freely select a pilot signal regardless of the reception signal R _RF, and the phase and phase for any R _RF or when no R _RF is received. The amplitude deviation can be corrected, and even if there is a phase and amplitude deviation that is so large that it is difficult to demodulate the pilot signal from the received signal _RRF , it can be corrected in advance.

FIG. 4 is a block diagram showing a receiver according to Embodiment 3 of the present invention, in which 40 is a digital signal processing unit, 41 is a phase and amplitude deviation correction processing unit, 42 is a time / frequency synchronization processing unit, and 43 is a CP. (CyclicPrefix) removal unit, 44 is an FFT (Fast Fourier Transform) processing unit, 45 is a channel estimation unit, 46 is a parallel / serial conversion unit, and 47 is a demodulation processing unit. The same reference numerals are given to the portions corresponding to, and duplicate explanations are omitted.
The receiver of this example is intended to demodulate the OFDM signal and uses a pilot signal included in the OFDM signal for channel estimation.

In the figure, only the RF band received signal R _RF from the LNA 2 is supplied to the frequency conversion circuits 3 and 4, subjected to quadrature detection by the direct detection method and supplied to the LPFs 7 and 8, and the baseband received signal R _BB In-phase signal I ₀ and quadrature signal Q ₀ are obtained. The in-phase signal I ₀ and the quadrature signal Q ₀ are converted into digital signals by the AD conversion circuits 9 and 10 and supplied to the digital signal processing unit 40.

In the digital signal processing unit 40, the phase and amplitude deviation of the in-phase signal I ₀ and the quadrature signal Q ₀ are corrected by the phase and amplitude deviation correction processing unit 41, and symbol synchronization and synchronization are performed by the time / frequency synchronization processing unit 42. Frequency offset compensation is performed and CP removal processing unit 43 performs CP removal processing. The output signal of the CP removal processing unit 43 is subjected to FFT processing by the FFT processing unit 44 and becomes a baseband modulated wave signal for each subcarrier. The baseband modulated signal is supplied to the channel estimation unit 45, a pilot signal of a known pattern to be inserted in a known regularity to the baseband modulated wave signal (hereinafter, referred to as the received pilot signal P _R) to the clue Thus, channel estimation and compensation processing (equalization) are performed. The equalized baseband modulated wave signal is supplied to the parallel / serial converter 46, converted into a serial signal, supplied to the demodulation processor 47, and demodulated.
The time / frequency synchronization processing unit 42 to the demodulation processing unit 47 correspond to the baseband demodulation unit 11 of the first and second embodiments, and can be realized using a known technique. As a subcarrier modulation scheme, BPSK can be used for the pilot subcarrier and QAM can be used for the data subcarrier. As a means for realizing the digital signal processing unit 40, a commercially available DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), or dynamic reconfiguration device can be used.

Channel estimation processing unit 45 may store the original pattern of the pilot signal (known pattern) as a pilot replica signal P _rep, based on a comparison of the received pilot signals P _R and P _rep, the phase equivalent or amplitude equivalent This _Prep is supplied to the phase and amplitude deviation correction processing unit 41 at symbol timing.

The pilot replica signal generation unit 26 of the phase and amplitude deviation correction processing unit 41 of this example converts the pilot replica signal _Prep supplied from the channel estimation processing unit 45 into the frequency of the corresponding subcarrier, and then the multiplier. It differs from the previous embodiment in that it is supplied to 29-32 and the like. That is, since the pilot replica signal P _rep from the channel estimation processor 45 is just a symbol similar to the modulation pattern M, and the complex signal and the complex multiplication of the subcarrier stored in the table or the like, the same sub-carrier frequency and P _BB Convert to

  FIG. 5 is a block diagram showing a receiver according to the fourth embodiment of the present invention. The configuration from the BPF 1 to the AD conversion circuits 9 and 10 is the same as that in the third embodiment, and is not shown. The receiver of this example further includes a phase correction processing unit 48 and an amplitude correction processing unit 49 in the subsequent stage of the phase and amplitude deviation correction processing unit 41 so as to further correct the remaining phase deviation and amplitude deviation. This is different from the receiver of the third embodiment in the points. The other components corresponding to those in the previous drawings are given the same reference numerals and redundant description is omitted.

First, the principle of this example will be briefly described.
Multiplying the in-phase signal I ₀ and the quadrature signal Q ₀ in Equation (2) above,
_{I 0 · Q 0 = - (} 1/2) cos {(ω c '- ω c) t + θ} · gsin {(ω c' -ω c) t + θ-ΔΦ}
LPF [I ₀ · Q ₀ ] =-(1/8) g · sin (ΔΦ) (21)
It becomes. However, LPF [] is a function that takes out a component in the vicinity of a direct current on a sufficient time average. Since the FFT processing unit 44 is a digital process, and no phase deviation or amplitude deviation occurs, the received baseband signal R _SC = I _SC + jQ _SC of any subcarrier in the subcarriers obtained from the FFT processing unit 44 However, Formula (21) is applicable.
Further, in the equation (2), (ω _c ′ −ω _c ) t + θ = α is set for the subcarrier of interest (ω _c ′ = ω _c in the case of baseband, but it is not limited now), and the phase and amplitude are already set Since it is corrected by the deviation correction processing unit 41, if cos (ΔΦ) ≈1 and g≈1, Equation (2) is
R _SC = (1/2) cosα−j (1/2) g {sinΔΦ · cosα + cosΔΦ · sinα}
≒ (1/2) cosα
-J (1/2) g {sinΔΦ · cosα + sinα} (22)
It becomes.
In equation (22), cos α is the original in-phase signal of R _SC , and sin α is the original quadrature signal, so an extra component contained in the quadrature signal Q _SC of the received baseband signal R _SC may be subtracted. That is, a signal obtained by multiplying the in-phase signal I _SC by g · sin (ΔΦ) is subtracted from Q _SC .

On the other hand, when the in-phase signal I ₀ (I _SC ) and the quadrature signal Q ₀ (Q _SC ) of Equation (2) are squared,
I _SC ² = (1/2) [1 + cos2 {(ω _c '−ω _c ) t + θ}]
Q _SC ² = g ² (1/2) [1 + sin 2 {(ω _c '−ω _c ) t + θ−ΔΦ}] (23)
It becomes. Assuming that a modulation scheme in which symbols are generated evenly in each quadrant of the constellation, such as QPSK and QAM, is adopted as the subcarrier of interest, cos and sin in Equation (22) are sufficient symbols. If you average only 0,
LPF [Q _SC ² −I _SC ² ] = (g ² −1) / 2 (24)
Thus g ² is obtained. The quadrature signal Q _SC may be divided by the square root, but since g≈1 is assumed, the following approximation holds.
1 / g≈1- (g ² -1) / 2 (25)

FIG. 6 is an internal block diagram of the phase correction processing unit 48 and the amplitude correction processing unit 49 of FIG.
The phase correction processing unit 48 receives from the parallel / serial conversion unit 46 a signal obtained by time-division multiplexing the baseband signal (soft decision symbol data) of each subcarrier in the OFDM symbol period.
The multiplier 301 multiplies the in-phase signal input from the parallel / serial converter 46 by a phase correction value (described later) and outputs the result.
The adder 302 adds the multiplication result input from the multiplier 301 to the orthogonal signal input from the parallel / serial converter 46 and outputs the result.
The phase correction processing unit 48 outputs the in-phase signal input from the parallel / serial conversion unit 46 and the addition output of the adder 302 to the amplitude correction processing unit 49 as an in-phase signal and a quadrature signal after phase correction. .

Multiplier 303 multiplies the phase-corrected in-phase signal and quadrature signal and outputs the result.
The control loop 304 performs low-pass filtering (averaging) on the multiplication value input from the multiplier 303 by the LPF 311 to obtain a value corresponding to the equation (21), and integrates it by the integrator 312. A predetermined loop gain _GPP is multiplied by 313 and output to the multiplier 301 as a phase correction value.

All the components in the phase correction processing unit 48 except the multiplier 313 operate basically every time a baseband signal is input (for each sample). However, the control loop 304 stops operation when the baseband output from the phase correction processing unit 48 is not suitable for averaging, such as when the signal is that of a BPSK modulated pilot subcarrier or DC subcarrier. .
Since sin (ΔΦ) detected in the process corresponding to the equation (21) is integrated and feedback controlled as described above, even a slight remaining deviation is converged to a correction value for correcting it. Can do. Since the output of the multiplier 303 varies randomly from sample to sample, the LPF 311 is provided to prevent the variation from appearing in the phase correction value. However, the loop gain G _PP is set to a number sufficiently smaller than 1. If you choose, you may be able to make it unnecessary. The operation period of the multiplier 313 is arbitrary, but is, for example, one OFDM symbol period.

Next, in the amplitude correction processing unit 49, the squarer 321 squares and outputs the in-phase signal input from the phase correction processing unit 48.
The multiplier 322 multiplies the quadrature signal input from the phase correction processing unit 48 by an amplitude correction value (described later) and outputs the result.
The squarer 323 squares the signal input from the multiplier 322 and outputs the result.
The subtracter 324 subtracts the signal input from the squarer 321 from the signal input from the squarer 323 and outputs the result.

The control loop 324 obtains a value corresponding to the equation (24) by low-pass filtering the difference value input from the subtractor 324 by the LPF 331, integrates the value by the integrator 332, and outputs a predetermined value by the multiplier 313. It outputs the result of the loop gain G _PP.
The adder 325 subtracts the signal input from the control loop 324 from 1 to obtain a value corresponding to Expression (25), and outputs the value to the multiplier 322 as an amplitude correction value.
The amplitude correction processing unit 49 outputs the in-phase signal input from the phase correction processing unit 48 and the quadrature signal output from the multiplier 322 to the demodulation processing unit 47 as an in-phase signal and a quadrature signal after amplitude correction, respectively. To do.

  In the amplitude correction processing unit 49 as well as the phase correction processing unit 48, the multiplier 321 to the subtracter 324 operate every time a baseband signal is input (for each sample). Also, the correction converges without leaving a deviation by a feedback loop including integration.

  The phase correction processing unit 48 and the amplitude correction processing unit 49 are not limited to being connected in the order shown in FIG. Further, the present invention is not limited to the one provided immediately after the parallel / serial conversion processing unit 46, and may be inserted at any location after the phase and amplitude deviation correction processing unit 41. However, the configuration for processing the baseband signal of each subcarrier after the equivalent as in this example has the following advantages.

  That is, if a plurality of control loops 304 and 324 (more precisely, means for holding the tap value of the LPF and the current value of the integrator) are provided, and switching is performed in a time division manner according to the subcarrier frequency, Even when the phase deviation and the amplitude deviation have frequency dependence, correction can be performed by calculating a correction value suitable for each frequency. The number of switching control loops may be the number of subcarrier groups (segments) obtained by bundling a predetermined number of consecutive subcarriers, or the total number of subcarriers.

The block diagram which shows the receiver which concerns on Example 2 of this invention The block diagram which shows an example of the phase and amplitude deviation correction process part in FIG. Internal block diagram showing an example of a pilot signal demodulation processing unit in FIG. The block diagram which shows the receiver which concerns on Example 3 of this invention The block diagram which shows the receiver which concerns on Example 4 of this invention Internal block diagram of the phase correction processing unit 48 and the amplitude correction processing unit 49 of FIG. Block diagram of a conventional direct detection receiver Block diagram showing the basic configuration of the conventional method (3) and the receiver according to Embodiment 1 of the present invention

Explanation of symbols

1 BPF
2 LNA
3, 4 Frequency conversion circuit 5 Local oscillator 6 90 ° phase shifter 7, 8 LPF
9, 10 AD conversion circuit 11 Baseband demodulation unit 12 Phase and amplitude deviation correction processing unit 13-16 Synthesis circuit 17 Pilot signal demodulation processing unit 18, 19 LPF
20-23 Multiplier 24, 25 Adder 26 Pilot Replica Signal Generation Unit 27 CP Detection Circuit 28 Modulation Pattern Generation Unit 29-32 Multiplier 33, 34 Sign Inversion Circuit 35-38 LPF
40 digital signal processing unit 41 phase and amplitude deviation correction processing unit 42 time / frequency synchronization processing unit 43 CP removal unit 44 FFT processing unit 45 channel estimation unit 46 parallel / serial conversion unit 47 demodulation processing unit 48 phase correction processing unit 49 amplitude correction Processing part

Claims (3)

Analog quadrature detection means for quadrature detection of a received signal obtained by quadrature modulation of an in-phase signal and quadrature signal by direct detection method, AD conversion means for AD converting the output signal of the analog quadrature detection means, and the AD conversion means In a direct detection receiver provided with demodulation means for demodulating the digital in-phase signal and quadrature signal output from digital signal processing,
Phase and amplitude deviation correction processing means for generating a pilot signal;
Frequency conversion means for up-converting the pilot signal to an RF band using an output signal of a local oscillator of the analog quadrature detection means;
Synthesizing the output signal of the frequency converting means with the received signal and supplying the synthesized signal to the frequency converting means, and the upconverted pilot signal is orthogonalized by the analog quadrature detecting means together with the received signal. Detection, AD conversion, and supply to the phase and amplitude deviation correction processing means,
The phase and amplitude deviation correction processing means includes:
By calculating the pilot signal to be generated and the received signal subjected to quadrature detection and analog-to-digital conversion by the analog quadrature detection unit, a correction value for correcting the phase and amplitude deviation generated by the analog quadrature detection unit is obtained.
Using the correction value, the in-phase signal and the quadrature signal of the received signal subjected to quadrature detection and AD conversion are subjected to digital signal processing, and the phase and amplitude deviation between the in-phase signal and the quadrature signal are corrected. A direct detection receiver, characterized in that the direct detection receiver is supplied to the demodulation means. Analog quadrature detection means for performing quadrature detection on a received signal obtained by quadrature modulation of an in-phase signal and a quadrature signal including a pilot signal having a predetermined time length every predetermined time, and an output of the analog quadrature detection means An AD conversion means for AD converting the signal, and the digital in-phase signal and quadrature signal output from the AD conversion means are subjected to channel estimation processing using the pilot signal by the channel estimation processing means, and then digitally processed. In a direct detection receiver provided with a demodulation means for demodulating by signal processing,
Phase and amplitude deviation correction processing processing means for supplying the digital in-phase signal and quadrature signal output from the AD conversion means and the pilot signal included in the reception signal used for the channel estimation processing is provided. And
The amplitude deviation correction processing means includes:
Pilot replica generation means for generating a pilot replica signal having substantially the same angular frequency as the pilot signal included in the received signal orthogonally detected by the frequency conversion means;
By calculating the pilot replica signal and the received signal that has been subjected to quadrature detection and analog-to-digital conversion by the analog quadrature detection means, a correction value for correcting the phase and amplitude deviation generated by the analog quadrature detection means is obtained.
Using the correction value, the in-phase signal and the quadrature signal of the received signal subjected to quadrature detection and AD conversion are subjected to digital signal processing, and the phase and amplitude deviation between the in-phase signal and the quadrature signal are corrected. ,
A direct detection receiver characterized in that the channel estimation processing means performs channel estimation processing on the in-phase signal and the quadrature signal whose phase and amplitude deviations are corrected. The direct detection receiver according to claim 1 or 2, wherein the received signal is an orthogonal frequency division multiplexing signal,
FFT processing means for converting the orthogonally detected and AD-converted received signal from the time domain to the frequency domain in symbol units;
For each subcarrier demodulated signal output from the FFT processing means, a deviation of at least one of phase and amplitude is detected, corrected through a feedback control loop including integration, and then output to the demodulating means. Phase or amplitude correction means, and
The direct detection receiver characterized in that the phase or amplitude correction means performs different correction according to the frequency of the subcarrier.