JP2014195168A - Receiver and noise correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a noise component included in a local signal and to improve a data transmission characteristic.SOLUTION: A mixer multiplies a reception signal by a local signal to frequency convert into an upconvert signal and a downconvert signal. A band pass filter eliminates the upconvert signal. An adder changes a local signal frequency fed from a local oscillator, to multiplex with the downconvert signal. An A/D converter converts the multiplexed signal of the downconvert signal with the local signal, from an analog signal to a digital signal. A local noise estimation unit separates the local signal fed from the local oscillator from the digitized multiplexed signal of the local signal fed from the local oscillator with the downconvert signal, to estimate a noise component. A noise correction unit corrects the reception signal on the basis of the estimated noise component of the local signal.

Description

  The present invention relates to a receiving apparatus and a noise correction method for a local signal.

  In recent years, with the progress of digital signal processing, in the field of wireless communication, it has become possible to use a radio device that performs digital signal processing using a CPU (Central Processing Unit) having a clock speed equal to or higher than an RF (Radio Frequency) frequency. On the other hand, since the radio signal itself has an analog waveform, the antenna receives radio signals that arrive on the radio receiver side and discriminates signals having different frequencies, and an SNR (signal sufficient for signal demodulation) A function of amplification is required so as to obtain an (noise ratio).

  When the filtering function is performed in an RF stage, that is, an analog stage, a filter is arranged between a necessary signal bandwidth (Bd) and a bandwidth (Bu) to be removed as an unnecessary signal outside the band. Therefore, Bu> Bd, that is, Bu / Bd> 1, and ideal solutions Bu = Bd and Bu / Bd = 1 cannot be obtained so as to remove all unnecessary bands. Further, Bd / fo obtained by dividing Bd by the carrier frequency (fo) is called a ratio band. As the ratio band is smaller, that is, the band is narrower than the carrier frequency, Bu / Bd is a value farther from 1. Become. Therefore, unnecessary signals in the high frequency band can be removed by removing unnecessary waves outside the band with an analog filter having a large value of Bu / Bd in the RF stage and performing frequency conversion (frequency shift) to a low frequency. An unnecessary signal in the vicinity of the signal band is removed using a filter with / Bd close to 1. Further, after digital conversion, unnecessary signals outside a larger band are removed by a digital filter.

  As for the amplification function, it is necessary to amplify a radio signal (desired wave) received from the antenna so that an SNR sufficient to demodulate the signal is obtained. It is ideal to amplify at the RF first stage with little additional noise, but at the RF first stage where the filtering is not sufficient, the unwanted wave outside the band is amplified simultaneously with the desired signal, and the signal level of the unwanted wave is particularly high. If it is larger than the desired wave, in addition to the dynamic range of the signal, a dynamic range including the level difference of the unwanted wave from the desired wave is required, covering the desired wave and unwanted wave with independent signal levels. It is necessary to perform amplification with a dynamic range. In general, there is no amplifier having a dynamic range necessary for practical use, while removing unnecessary signals at the RF initial stage, between RF stages after RF filtering, IF (Intermediate Frequency) stage after frequency conversion, or baseband stage. A means for amplifying in stages in multiple stages is taken.

  As described above, by repeating filtering and amplification including frequency conversion, the analog signal is converted into a digital signal by an A / D (Analog to Digital) converter at the baseband stage or IF stage under the necessary SNR, and further filtered. The signal is demodulated in response to waveform shaping.

  In recent years, the functional density of digital processing after the A / D converter has increased, and instead of an analog filter whose performance is determined by its physical size, a digital filter whose filtering characteristics and physical size are not directly related The specific gravity of unwanted wave suppression due to is increasing. Here, in order to suppress the out-of-band unnecessary wave by the digital filter, it has been performed that the sampling frequency of the A / D converter is increased and digitized with a wide bandwidth.

  The received signal is transmitted after the carrier signal is modulated on the information emitting side. Here, on the transmission side, the carrier frequency is modulated by amplitude modulation (AM), phase modulation (PM), or both amplitude and phase (QAM: Quadrature Amplitude Modulation) based on information data to be transmitted. ing. Further, there are cases where GMSK (Gaussian Minimum Shift Keying) or quaternary FSK (Frequency Shift Keying) is used because it is difficult to send an unnecessary wave component out of the band even if a nonlinear element is used on the circuit. Furthermore, OFDM (Orthogonal Frequency Division Multiplexing) in which signals obtained by data modulation of individual carriers are arranged at equal intervals so as to be orthogonal to each other on the frequency axis may be used.

  A transmission system and a reception system are secured so that the signal modulated on the transmission side is not subjected to amplitude fluctuation and phase fluctuation as much as possible on the transmission side, the reception side, and the propagation path therebetween. With regard to the transmission path, it is not always possible to secure a stable propagation path in both amplitude and phase due to multipath, Doppler effect, etc., but improvements have been obtained by devising an equalizer or the like.

  Regarding the phase stability, deterioration due to the frequency converter is observed in both the transmitter and the receiver. In the frequency conversion, the signal is converted into a desired frequency by multiplying the signal by a local oscillator having a frequency difference before and after the conversion (for example, Patent Document 1). Here, the local oscillator usually obtains a desired frequency signal by locking a signal of a VCO (voltage controlled oscillator) to a reference frequency signal by a PLL (Phase Lock Loop). However, if the signal purity of the VCO is poor, the local oscillator is phase-shifted to the oscillation frequency. Noise is included. Here, when a local oscillator including such phase noise is used, the phase of the desired signal is modulated by the phase noise of the local signal, which may deteriorate data transmission characteristics (increase the error rate).

JP 2012-1000029 A

  As described above, when the local signal from the local oscillator includes phase noise, the phase of the desired signal is modulated by the phase noise of the local signal, and the data transmission characteristics are deteriorated. In particular, a receiving unit of a mobile communication radio device that prefers a small and simple structure uses a simple local oscillator, and thus is easily affected by phase noise of a local signal.

  In view of the above-described problems, an object of the present invention is to provide a receiver and a noise correction method that can estimate a noise component included in a local signal and improve data transmission characteristics.

  In order to solve the above-described problem, a receiving device according to one embodiment of the present invention includes a local oscillator that oscillates a local signal, a reception signal and the local signal, and a frequency conversion into an up-convert signal and a down-convert signal. A mixer for performing the processing, a band-pass filter for removing one of the up-converted signal and the down-converted signal, and changing the frequency of the local signal from the local oscillator to multiplex with the up-converted signal or the down-converted signal. An adder to be converted, an A / D converter for converting a multiplexed signal of the local signal from the local oscillator and the up-converted signal or the down-converted signal from an analog signal to a digital signal, and a digital signal by the A / D converter. Low from the local oscillator A local signal noise estimator that separates a local signal from the local oscillator from a multiplexed signal of a local signal and the up-converted signal or the down-converted signal, and estimates a noise component included in the local signal from the local oscillator And a noise correction unit that corrects the received signal based on the noise component of the local signal estimated by the local signal noise estimation unit.

  Further, in the reception device according to one aspect of the present invention, the local signal noise estimation unit compares the separated local signal with an ideal local signal, and compares the separated local signal with the ideal local signal. A noise component included in the local signal from the local oscillator may be estimated based on an error from the signal.

  Further, in the receiving device according to one aspect of the present invention, the adder may be disposed at a subsequent stage of the bandpass filter.

  In the receiving device according to one aspect of the present invention, a signal obtained by dividing or multiplying a local signal from the local oscillator may be supplied to the adder or the mixer.

  In addition, the noise correction method according to one aspect of the present invention multiplies a reception signal and a local signal, performs frequency conversion to an up-conversion signal and a down-conversion signal, and uses a band-pass filter to perform the up-conversion signal or the down-conversion signal. A noise correction method for correcting the influence of a noise component included in the local signal in a receiving apparatus that removes one of the local signal, wherein the adder is a local signal from a local oscillator that oscillates the local signal. A procedure for changing the frequency and multiplexing with the up-convert signal or the down-convert signal, and an A / D converter that multiplexes the local signal from the local oscillator with the up-convert signal or the down-convert signal. For converting an analog signal to a digital signal A local signal noise estimator separates a local signal from the local oscillator from a multiplexed signal of the local signal from the local oscillator converted into a digital signal and the up-converted signal or the down-converted signal, and A step of estimating a noise component included in a local signal from a local oscillator, and a step of correcting a received signal based on the noise component of the estimated local signal by the noise correction unit. .

  According to the present invention, the noise component included in the local signal can be estimated, and the data transmission characteristic can be improved by correcting the received signal based on the noise component included in the local signal.

It is a block diagram which shows the receiver which concerns on 1st Embodiment. It is explanatory drawing of operation | movement of the receiver which concerns on 1st Embodiment. It is a block diagram which shows the receiver which concerns on 2nd Embodiment. It is a block diagram which shows the receiver which concerns on 3rd Embodiment. It is a block diagram which shows the receiver which concerns on 4th Embodiment. It is a block diagram which shows the receiver which concerns on 5th Embodiment.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a receiving apparatus according to the first embodiment. As shown in FIG. 1, the receiving apparatus according to the present embodiment includes an antenna 11, an LNA (Low Noise Amplifier) 12, a bandpass filter 13, a mixer 14, a local oscillator 15, an adder 16, and a band. A path filter 17, an A / D (Analog to Digital) converter 18, a local signal noise estimation unit 19, and a noise correction unit 20 are provided.

  The LNA 12 amplifies the reception signal from the antenna 11. The band pass filter 13 selects a signal in a band of an RF (Radio Frequency) signal that is a desired wave from the received signals. The mixer 14 multiplies the received RF signal and the local signal, and converts the frequency into an up-converted signal and a down-converted signal. The local oscillator 15 oscillates a local signal. The adder 16 superimposes the local signal on the output signal of the mixer 14. Note that the local signal superimposed on the adder 16 is frequency-divided or multiplied as necessary so that the frequency can be multiplexed by superimposing it on an IF (Intermediate Frequency) signal, and the frequency thereof is changed. The band pass filter 17 removes one of the up-convert signal and the down-convert signal from the output signal of the mixer 14 and extracts it as an IF (Intermediate Frequency) signal.

  The A / D converter 18 converts the IF signal on which the local signal is superimposed from an analog signal to a digital signal. The local signal noise estimation unit 19 separates the local signal and the down-convert signal from the output signal of the A / D converter 18 and obtains a noise component included in the local signal from the separated local signal. The noise correction unit 20 corrects the received signal based on the noise component of the local signal estimated by the local signal noise estimation unit 19.

  Next, the operation of this embodiment will be described. In FIG. 1, the reception signal of the antenna 11 is supplied to the mixer 14 via the LNA 12 and the band pass filter 13. The mixer 14 is supplied with a local signal from the local oscillator 15. The mixer 14 multiplies the received RF signal by the local signal from the local oscillator 15, and the received RF signal is an up-converted signal (the sum frequency of the RF signal and the local signal, as shown in FIG. 2A). Signal) and a down-converted signal (a signal having a difference frequency between the RF signal and the local signal).

  The output signal of the mixer 14 is supplied to the adder 16. Further, a local signal is supplied from the local oscillator 15 to the adder 16. As shown in FIG. 2B, the local signal is superimposed on the output signal of the mixer 14 by the adder 16. The output signal of the adder 16 is supplied to the band pass filter 17.

  The up-convert signal is removed by the band pass filter 17. Therefore, as shown in FIG. 2C, the down-convert signal component and the local signal component are output from the band pass filter 17 as IF signals. The output signal of the band pass filter 17 is supplied to the A / D converter 18. The output signal of the bandpass filter 17 is converted from an analog signal to a digital signal by the A / D converter 18.

  For example, in a wireless local area network (LAN), a signal of several GHz (2.4 GHz band, 5 GHz band, etc.) is used as the RF signal. A signal of 100 MHz to 300 MHz is used as the IF signal. Here, for example, when the frequency of the RF signal is 2 GHz and the frequency of the IF signal is 100 MHz, the frequency of the local signal from the local oscillator 15 is 2.1 GHz or 1.9 GHz. Thus, normally, the frequency of the local signal is higher than the frequency of the IF signal, and the local signal does not fall within the band of the bandpass filter 17. Moreover, it is difficult to directly perform A / D conversion on such a high frequency local signal. Therefore, in this example, the local signal is frequency-divided or multiplied as necessary to reduce the frequency so that the local signal superimposed on the adder 16 can be frequency-multiplexed with the IF signal. Then, by multiplexing the local signal into the IF signal, the received signal and the local signal can be digitized by the same A / D converter 18.

  As the local oscillator 15, a PLL (Phase Locked Loop) is usually used. In the PLL, the phase comparator compares the phase of the reference signal from the reference oscillator with the phase of the output signal of the VCO (Voltage Controlled Oscillator) via the frequency divider, and the comparison output of this phase comparator The oscillation frequency of the VCO is controlled. In the local oscillator having such a configuration, a signal obtained by dividing the local signal can be extracted from the frequency divider. If a local signal having a frequency within the band of the band pass filter 17 can be extracted from the output of the frequency divider, the local signal can be supplied to the adder 16.

  As shown in FIG. 2D, the local signal noise estimation unit 19 separates the local signal from the output signal of the A / D converter 18 by a digital filter. A noise component included in the local signal is obtained from the separated local signal. The noise correction unit 20 corrects the received signal based on the estimated noise component of the local signal.

  Thus, in the present embodiment, the frequency of the local signal from the local oscillator 15 is lowered to a frequency that can be multiplexed with the IF signal, and the local signal is superimposed on the IF signal by the adder 16, and the A / D converter 18 The IF signal composed of the down-convert signal component and the local signal component is digitized. The local signal noise estimator 19 separates the down-converted signal and the local signal by digital processing, and estimates the noise component of the local signal. When the local signal is digitized in this way, a noise component included in the local signal can be estimated by digital processing. This will be further described.

  The local signal from the local oscillator 15 is ideally a sine wave, but includes a noise component of phase fluctuation and amplitude fluctuation. Therefore, the local signal L (t) from the local oscillator 15 is expressed as follows in a complex expression with a variable of time t.

Here, L ₀ (t) represents the amplitude component of the signal of the local oscillator 15, and ωt + φ (t) represents the phase component of the signal of the local oscillator 15. Ω is the set local frequency

On the other hand, the antenna 11, LNA 12, when a signal input via a band-pass filter 13, S (t), the received signal S (t) the center frequency omega _s of the signal S (t) is the information modulation S _Since it is modulated by ₀ (t) e ^{jθ (t)} , it can be expressed as follows.

  The received signal and the local signal from the local oscillator 15 are multiplied by the mixer 14. Then, a local signal is superimposed on the output of the mixer 14 by the adder 16. Then, the up-convert signal is removed by the band pass filter 17. In this case, the bandpass filter 17 outputs a signal Q (t) composed of a down-converted signal component and a local signal component as follows.

  In Expression (3), the first term on the right side is a down-converted signal component, and the second term is a local signal component.

  The signal from the band pass filter 17 is converted into a digital signal by the A / D converter 18. Then, the local signal noise estimator 19 determines from the output signal of the A / D converter 18 the down-converted signal component (first term on the right side of equation (3)) and the local signal component (second term on the right side of equation (3)). ) And are separated. The down-convert signal component and the local signal component can be separated in terms of frequency by, for example, a digital filter.

Here, the local signal is a sine wave signal having a known frequency. Therefore, the amplitude noise L ₀ (t) and the phase noise φ (t) included in the local signal can be obtained from the separated local signal components using the set value ω of the known local signal frequency. .

The local signal noise estimator 19 in FIG. 1 thus separates the down-converted signal component and the local signal component from the output signal of the A / D converter 18, and the known local signal is separated from the separated local signal. The amplitude noise L ₀ (t) and the phase noise φ (t) of the local signal are estimated using the frequency setting value ω.

In addition, the noise correction unit 20 substitutes the estimated amplitude noise L0 (t) and phase noise φ (t) into the down-converted signal component (the first term on the right side of the equation (3)), thereby obtaining the received signal. Correct and estimate the information modulation S ₀ (t) e ^{jθ (t)} .

In the above description, the local signal is directly superimposed on the IF signal. However, the local signal of the local oscillator 15 can be frequency-multiplexed with the down-converted signal within the band of the bandpass filter 17. The frequency is divided or multiplied as necessary. If attention is paid to the following when the local signal is divided or multiplied, the information modulation S ₀ (t) e ^{jθ (t)} can be similarly estimated.

  In the above analysis, the received signal S (t) and the local signal L (t) are treated as signals on the time axis. However, the received signal S (t) and the local signal L (t) are Fourier-transformed to obtain a frequency. In the region, the signal S (ω) and the local signal L (ω) may be calculated. In this way, by handling the signal in the frequency domain, the down-converted signal and the local signal can be more easily separated.

Further, the down-converted signal indicated by the first term on the right side of the equation (3) is obtained as a result of multiplying the local signal of the equation (1) and the received signal of the equation (2) by the mixer 14. . In addition, in the received signal, amplitude noise L ₀ (t) and phase noise φ (t) components of the local signal included in the local signal are included as modulation components. Therefore, if the output signal of the A / D converter 18 is converted to the frequency domain, the down-converted signal and the local signal are separated, and the separated down-converted signal is divided by the separated local signal, the amplitude noise of the local signal The components of L ₀ (t) and phase noise φ (t) are canceled, and the noise of the received signal can be corrected.

Next, the process of estimating the amplitude noise L ₀ (t) and the phase noise φ (t) of the local signal in the local signal noise estimation unit 19 will be described.

As described above, an ideal local signal is a sine wave having a known frequency ω. Therefore, by comparing the waveform of the local signal separated from the output signal of the A / D converter 18 with the waveform of the ideal local signal set from the known frequency ω, and obtaining this error, the amplitude noise L of the local signal is obtained. ₀ (t) and phase noise φ (t) can be estimated.

That is, the signal at each sampling time t _n (n = 1, 2,..., N) of the local signal separated from the output signal of the A / D converter 18 is L (t _n ), and there is no amplitude noise and no phase noise. Assuming that the signal at each sampling time of a local signal is M (t _n ), the amplitude noise L ₀ (t) and phase noise φ (t) of the local signal are the ideal local signal L (t _n ). It can be estimated by obtaining the amplitude noise L ₀ (t) and the phase noise φ (t) that minimize the sum of errors from the signal M (t _n ).

The error between the local signal L (t _n ) and the ideal local signal M (t _n ) is obtained as follows.

The sum of errors between the local signal L (t _n ) and the ideal local signal M (t _n ) is obtained as follows.

  Here, N is a numerical value that gives a time width in which a change in the sum of errors can be substantially ignored (can be regarded as being substantially stable).

The amplitude noise L ₀ (t) and the phase noise φ (t) that minimize the sum of errors between the local signal L (t _n ) and the ideal local signal M (t _n ) are, for example, LMS (Least Mean Square). ) It can be estimated by an algorithm.

  That is, the local signal to be estimated is

The ideal local signal without amplitude noise and phase noise.

Assuming that the coefficient for adding the amplitude noise L ₀ (t) and the phase noise φ (t) is W _n , the amplitude noise and the phase noise included in the local signal separated from the output signal of the A / D converter 18 In the LMS algorithm,

In the next step, the coefficient W _{n + 1} is updated to calculate the error ε (t). Here, W ₀ is an initial value, Δt is a step size, and μ is a parameter that determines the speed of convergence. Then, the above steps are repeated, and the amplitude noise L ₀ (t) and the phase noise φ (t) are estimated from the coefficient W _n when the sum of the squares of the error ε (t) is minimized.

  As described above, in the present embodiment, the local oscillator 15 that oscillates the local signal, the mixer 14 that multiplies the reception signal and the local signal, and converts the frequency into the up-convert signal and the down-convert signal, the up-convert signal, or A band-pass filter 17 that removes one of the down-converted signals, an adder 16 that changes the frequency of the local signal from the local oscillator and multiplexes with the up-converted signal or the down-converted signal, and a local signal from the local oscillator A / D converter 18 that converts a multiplexed signal of a signal and an up-convert signal or a down-convert signal from an analog signal to a digital signal, and a local signal and an up-convert signal or down from a local oscillator digitized by the A / D converter Comber The local signal from the local oscillator is separated from the multiplexed signal with the signal, and a local signal noise estimator 19 for estimating a noise component included in the local signal from the local oscillator, and the local signal estimated by the local signal noise estimator And a noise correction unit 20 that corrects the received signal based on the noise component of the signal.

  With this configuration, in this embodiment, the adder 16 superimposes the local signal on the IF signal, and the A / D converter 18 digitizes the IF signal composed of the down-converted signal component and the local signal component. The amplitude noise and phase noise of the local signal can be estimated by digital processing. The received signal can be corrected by the estimated amplitude noise and phase noise of the local signal.

  The processing for estimating and correcting the noise of the local signal as described above may be performed when a signal such as a pilot signal is received. The process for estimating and correcting the noise of the local signal as described above need not be performed continuously, and may be performed at predetermined time intervals.

[Second Embodiment]
FIG. 3 is a block diagram showing the receiving apparatus according to this embodiment. As shown in FIG. 3, the receiving apparatus according to the present embodiment includes an antenna 111, an LNA 112, a bandpass filter 113, a mixer 114, a local oscillator 115, an adder 116, a bandpass filter 117, and an A / D converter 118, local signal noise estimation section 119, noise correction section 120, and frequency divider 131 are provided. The antenna 111, LNA 112, band pass filter 113, mixer 114, local oscillator 115, adder 116, band pass filter 117, A / D converter 118, local signal noise estimation unit 119, and noise correction unit 120 are the same as those in the first embodiment. Corresponding to the antenna 11, LNA 12, band pass filter 13, mixer 14, local oscillator 15, adder 16, band pass filter 17, A / D converter 18, local signal noise estimation unit 19 and noise correction unit 20 in the form Yes.

  In this embodiment, the local signal from the local oscillator 115 is supplied to the mixer 114 and also supplied to the adder 116 via the frequency divider 131. Thus, the local signal supplied to the adder 116 is frequency-divided through the frequency divider 131, and the frequency is lowered. Thereby, the local signal superimposed on the adder 116 can be within the band of the band pass filter 117, and the down-convert signal and the local signal can be frequency-multiplexed into the IF signal.

[Third Embodiment]
FIG. 4 is a block diagram showing the receiving apparatus according to the present embodiment. In this embodiment, as shown in FIG. 4, an antenna 211, an LNA 212, a band pass filter 213, a mixer 214, a local oscillator 215, an adder 216, a band pass filter 217, and an A / D converter 218. A local signal noise estimation unit 219, a noise correction unit 220, and a frequency divider 231.

  In the second embodiment described above, the adder 116 is disposed between the mixer 114 and the bandpass filter 117, whereas in this embodiment, the adder 216 is provided in the subsequent stage of the bandpass filter 217. I have to. In this case, the local signal superimposed on the adder 216 need not be within the band of the bandpass filter 217. As a result, in the present embodiment, the frequency that can be digitized by the A / D converter 218 can be obtained by multiplexing the down-convert signal and the local signal.

[Fourth Embodiment]
FIG. 5 is a block diagram showing a receiving apparatus according to this embodiment. As shown in FIG. 5, the receiving apparatus according to the present embodiment includes an antenna 311, an LNA 312, a bandpass filter 313, a mixer 314, a local oscillator 315, an adder 316, a bandpass filter 317, and A / D converter 318, local signal noise estimation section 319, noise correction section 320, and multiplier 332 are provided. The antenna 311, LNA 312, bandpass filter 313, mixer 314, local oscillator 315, adder 316, bandpass filter 317, A / D converter 318, local signal noise estimation unit 319, and noise correction unit 320 are the first implementation described above. Corresponding to the antenna 11, LNA 12, band pass filter 13, mixer 14, local oscillator 15, adder 16, band pass filter 17, A / D converter 18, local signal noise estimation unit 19 and noise correction unit 20 in the form Yes.

  In this embodiment, in FIG. 5, the local signal from the local oscillator 315 is supplied to the mixer 314 and the adder 316 via the multiplier 332. In this case, the local signal from the local oscillator 315 is in the band of the band pass filter 317. Then, the local signal supplied to the mixer 314 is multiplied by the multiplier 332 and its frequency is increased.

[Fifth Embodiment]
FIG. 6 is a block diagram showing a receiving apparatus according to this embodiment. In this embodiment, as shown in FIG. 6, an antenna 411, an LNA 412, a band pass filter 413, a mixer 414, a local oscillator 415, an adder 416, a band pass filter 417, and an A / D converter 418 are provided. A local signal noise estimation unit 419, a noise correction unit 420, and a multiplier 432.

  In the fourth embodiment described above, the adder 316 is disposed between the mixer 314 and the bandpass filter 317, whereas in the present embodiment, the adder 416 is provided in the subsequent stage of the bandpass filter 417. I have to. In this case, the local signal to be superimposed on the adder 416 does not need to be within the band of the bandpass filter 417, and the frequency that can be digitized by the A / D converter 418 by multiplexing the down-convert signal and the local signal. do it.

  In the above-described embodiment, the local signal is superimposed on the IF signal, the IF signal including the down-converted signal component and the local signal component is digitized, the down-converted signal and the local signal are separated by digital processing, and the local signal is separated. The amplitude noise and phase noise of the signal are estimated. In this manner, since the received signal and the local signal are digitized by the same A / D converter, noise accompanying the phase error of the clock of the A / D converter can be canceled.

  If the influence of the phase noise caused by the A / D converter can be ignored, A that converts the local signal from the local oscillator from the analog signal to the digital signal separately from the A / D converter that converts the IF signal from the analog signal to the digital signal. An A / D converter is provided, and amplitude noise and phase noise are estimated from the local signal digitized by the A / D converter, and the noise component of the received new word is corrected based on the estimated noise component of the local signal. May be.

It should be noted that a program for realizing all or part of the functions of the receiving apparatus is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed, thereby executing each part. Processing may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” is a program that dynamically holds a program for a short time, like a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the above-described functions, or may be a program that can realize the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

14, 114, 214, 314, 414: mixers 15, 115, 215, 315, 415: local oscillators 16, 116, 216, 316, 416: adders 17, 117, 217, 317, 417: band-pass filter 18, 118, 218, 318, 418: A / D converters 19, 119, 219, 319, 419: local signal noise estimation units 20, 120, 220.312, 420: noise correction units 131, 231: frequency dividers 332, 432 : Multiplier

Claims (5)

A local oscillator that oscillates a local signal;
A mixer that multiplies the received signal by the local signal and converts the frequency into an up-converted signal and a down-converted signal;
A bandpass filter for removing one of the up-converted signal or the down-converted signal;
An adder that changes the frequency of the local signal from the local oscillator and multiplexes with the up-converted signal or the down-converted signal;
An A / D converter that converts a multiplexed signal of the local signal from the local oscillator and the up-converted signal or the down-converted signal from an analog signal to a digital signal;
A local signal from the local oscillator is separated from a multiplexed signal of the local signal from the local oscillator and the up-converted signal or the down-converted signal digitized by the A / D converter, and the local signal from the local oscillator is separated. A local signal noise estimator for estimating a noise component included in the signal;
A noise correction unit that corrects a received signal based on a noise component of the local signal estimated by the local signal noise estimation unit;
A receiving apparatus comprising: The local signal noise estimation unit compares the separated local signal with an ideal local signal, and determines a local signal from the local oscillator based on an error between the separated local signal and the ideal local signal. The receiving apparatus according to claim 1, wherein a noise component included in is estimated. The receiving apparatus according to claim 2, wherein the adder is arranged at a subsequent stage of the bandpass filter.   4. The receiving apparatus according to claim 1, wherein a signal obtained by dividing or multiplying a local signal from the local oscillator is supplied to the adder or the mixer. 5. A reception device that multiplies a reception signal and a local signal, converts the frequency into an up-conversion signal and a down-conversion signal, and removes one of the up-conversion signal or the down-conversion signal by a bandpass filter. A noise correction method for correcting the influence of a noise component included in the local signal,
A step in which an adder changes a frequency of a local signal from a local oscillator that oscillates a local signal, and multiplexes with the up-convert signal or the down-convert signal
A procedure in which an A / D converter converts a multiplexed signal of a local signal from the local oscillator and the up-converted signal or the down-converted signal from an analog signal to a digital signal;
A local signal noise estimation unit separates the local signal from the local oscillator from the multiplexed signal of the local signal from the local oscillator converted into a digital signal and the up-converted signal or the down-converted signal, and the local signal A procedure for estimating the noise component contained in the local signal from the oscillator;
A procedure for correcting a received signal based on a noise component of the estimated local signal by a noise correction unit;
A noise correction method comprising:

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