Receiving apparatus

Abstract

To provide a technique for improving accuracy of correction of a reception signal.SOLUTION: The receiving device 100 includes a modulated signal generator 10, an oscillation circuit 12, a first mixer 24a, a second mixer 24b, and a correction unit 30. The modulation signal generator 10 outputs a modulation signal. The oscillation circuit 12 outputs a local signal modulated by the modulation signal from the modulation signal generator 10. The first mixer 24a and the second mixer 24b perform quadrature detection of the received signal with the local signal from the oscillation circuit 12. The correction unit 30 corrects the quadrature component of the quadrature-detected reception signal by the in-phase component of the quadrature-detected reception signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a receiving technique, and more particularly to a receiving device for receiving a signal. [Background technology]

[0002] The receiver includes a receive channel operable to split a received RF signal into an I channel and a Q channel. The receive channel includes error sources such as pre-demodulation (PD) error, LO mixer error, and baseband (BB) error. The quadrature error corrector detects errors from each error source. Upon receiving the RF signal, the quadrature error corrector applies correction coefficients to correct each error source in the order of BB, LO, and PD (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2014 / 0270001 Summary of the Invention [Problem to be solved by the invention]

[0004] To correct the IQ quadrature error and gain error, for example, the quadrature error and gain error are estimated from the demodulated IQ signal, and a correction value is added to one of the IQ signals. To estimate the error, cross-correlation is calculated from the IQ sample values, but if the correlation between the received signal to be demodulated and the image signal is strong, the error cannot be estimated correctly, and the received signal is attenuated along with the image signal during correction.

[0005] The present invention has been made in view of the above circumstances, and its object is to provide a technique for improving the accuracy of correction of a received signal. [Means for solving the problem]

[0006] In order to solve the above problem, a receiving device according to one aspect of the present disclosure includes a modulation signal generator that outputs a modulation signal, an oscillation circuit that outputs a local signal modulated by the modulation signal from the modulation signal generator, a quadrature detector that performs quadrature detection on a received signal using the local signal from the oscillation circuit, and a correction unit that corrects the quadrature component of the received signal that has been quadrature detected by the quadrature detector using the in-phase component of the received signal that has been quadrature detected by the quadrature detector.

[0007] Any combination of the above components, and any transformation of the present invention into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present invention. [Effects of the Invention]

[0008] According to the present invention, the accuracy of correction of received signals can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a receiving device according to an embodiment. [Figure 2] 2(a) to 2(c) are diagrams showing the processing for the first comparison target. [Figure 3] 3(a) to 3(c) are diagrams showing the processing for the second comparison target. [Figure 4] 4(a)-(c) are diagrams showing details of the processing for the second comparison target in FIGS. 3(a)-(c). [Figure 5] 5(a) to 5(c) are diagrams showing the processing performed on the received signal. [Figure 6] 6(a) to 6(c) are diagrams showing details of the processing performed on the received signals of FIGS. 5(a) to 5(c). [Figure 7] 7(a) to 7(c) are diagrams showing the processing performed on the received signal. [Figure 8] 8(a) to 8(c) are diagrams showing details of the processing performed on the received signals of FIGS. 7(a) to 7(c). DETAILED DESCRIPTION OF THE INVENTION

[0010] Before describing the present invention in detail, an overview will be provided. This embodiment relates to a receiving device for receiving a wireless signal. The receiving device performs, for example, direct conversion quadrature detection. Here, in the receiving device, the correlation between the received signal and the image signal becomes strong when an unmodulated received signal and an image signal of an unmodulated interference wave have the same frequency. Furthermore, when the received signal is modulated, the correlation between the received signal and the image signal also becomes strong when the image signal of the interference wave, which is modulated in the same way as the received signal and synchronized with the received signal, has the same frequency as the received signal. When the correlation between the received signal and the image signal becomes strong, as described above, the IQ quadrature error and gain error cannot be accurately estimated, and the received signal is attenuated along with the image signal during correction. The receiving device according to this embodiment performs frequency modulation on a local signal and performs quadrature detection on the received signal using the frequency-modulated local signal. As a result, the modulation phases of the received signal and the image signal after quadrature detection are opposite, thereby weakening the correlation between the received signal and the image signal.

[0011] 1 shows the configuration of a receiving device 100. The receiving device 100 includes a modulated signal generator 10, an oscillator circuit 12, a frequency divider 14, an antenna 20, a receiving circuit 22, a first mixer 24a and a second mixer 24b collectively referred to as mixers 24, a first AAF 26a and a second AAF 26b collectively referred to as AAFs (Anti-Aliasing Filters) 26, a first ADC 28a and a second ADC 28b collectively referred to as ADCs (Analog to Digital Converters) 28, a correction unit 30, a first filter 32a and a second filter 32b collectively referred to as filters 32, and a demodulator 34.

[0012] Here, the following will be described in the order of (1) the common configuration between this embodiment and the comparison subject, and the issues with the comparison subject, and (2) the configuration of this embodiment. (1) Common configuration between this example and the comparison example and issues with the comparison example The antenna 20 receives an RF (Radio Frequency) signal from a transmitting device (not shown). The RF signal corresponds to a received signal. The RF signal may be, for example, frequency modulated, but is not limited to this. The antenna 20 outputs the received RF signal to a receiving circuit 22.

[0013] The receiving circuit 22 includes a filter that reduces noise components contained in the RF signal, an LNA (Low Noise Amplifier) ​​that amplifies the RF signal from the filter, and a filter that reduces noise components contained in the amplified RF signal. The receiving circuit 22 outputs the RF signal (hereinafter also referred to as "RF signal") that has had its noise components reduced and is amplified to the first mixer 24a and the second mixer 24b.

[0014] The comparison does not include the modulation signal generator 10. The oscillator circuit 12 outputs a local signal. The frequency divider 14 receives the local signal from the oscillator circuit 12 and adjusts the frequency of the local signal. The frequency divider 14 outputs the frequency-adjusted local signal (hereinafter also referred to as the "local signal") to the first mixer 24a and the second mixer 24b. Here, the phase of the local signal output to the second mixer 24b is shifted by 90 degrees from the phase of the local signal output to the first mixer 24a.

[0015] The first mixer 24a generates an I-phase baseband signal (hereinafter referred to as the "I signal") by multiplying the RF signal from the receiving circuit 22 by the local signal from the frequency divider 14. The I signal is an in-phase component of the RF signal. The first mixer 24a outputs the I signal to the first AAF 26a. The second mixer 24b multiplies the RF signal from the receiving circuit 22 by the local signal from the frequency divider 14 to generate a Q-phase baseband signal (hereinafter referred to as the "Q signal") that is orthogonal to the I-phase baseband signal. The Q signal is a quadrature component of the RF signal. The second mixer 24b outputs the Q signal to the second AAF 26b. The first mixer 24a and the second mixer 24b correspond to quadrature detectors, and the quadrature detectors perform quadrature detection on the RF signal using the local signal.

[0016] Below, we will explain the processing for the comparison target, also using Figures 2(a)-(c), 3(a)-(c), and 4(a)-(c). Figures 2(a)-(c) correspond to the case where the received signal is unmodulated, and will be referred to below as the "first comparison target." Figures 3(a)-(c) and 4(a)-(c) correspond to the case where the received signal is modulated, and will be referred to below as the "second comparison target."

[0017] 2(a)-(c) show processing for the first comparison target. The horizontal axis represents frequency, and the vertical axis represents signal level. FIG. 2(a) shows the signal before quadrature detection in the mixer 24. Shown are a received signal 200 output from the receiving circuit 22, a local signal 210 output from the frequency divider 14, and an interference wave 220 output from the receiving circuit 22. Here, the difference between the frequency of the received signal 200 and the frequency of the local signal 210 is equal to the difference between the frequency of the local signal 210 and the frequency of the interference wave 220.

[0018] 2(b) shows the signal after quadrature detection in mixer 24. Due to the relationship between the frequencies of received signal 200, local signal 210, and interfering signal 220 described above, after quadrature detection, image signal 230 of interfering signal 220 appears at the same frequency as received signal 200. Therefore, there is a strong correlation between received signal 200 and image signal 230. FIG. 2(c) shows the signal after quadrature detection in which correction has been performed to attenuate image signal 230. While the signal level of image signal 230 is reduced by the correction, the signal level of received signal 200 is also reduced.

[0019] 3(a)-(c) show processing for the second comparison target. The horizontal axis represents frequency, and the vertical axis represents signal level. FIG. 3(a) shows the signal before quadrature detection in the mixer 24. Shown are a received signal spectrum 202 of a received signal 200 output from the receiving circuit 22, a local signal 210 output from the frequency divider 14, and an interference wave spectrum 222 of an interference wave 220 output from the receiving circuit 22. Here, the difference between the center frequency of the received signal spectrum 202 and the frequency of the local signal 210 is equal to the difference between the frequency of the local signal 210 and the center frequency of the interference wave spectrum 222.

[0020] Figures 4(a)-(c) show details of the processing for the second comparison. Figure 4(a) is a diagram in which Figure 3(a) is broken down into instantaneous timings. According to Figure 4(a), received signal 200 oscillates between the lowest and highest frequencies of received signal spectrum 202. Also, jammer 220 oscillates between the lowest and highest frequencies of jammer spectrum 222. Here, when received signal 200 exists at the lowest frequency of received signal spectrum 202, jammer 220 exists at the highest frequency of jammer spectrum 222. When received signal 200 exists at the highest frequency of received signal spectrum 202, jammer 220 exists at the lowest frequency of jammer spectrum 222. Figures 4(b)-(c) will be described later.

[0021] 3(b) shows the signal after quadrature detection in mixer 24. Due to the relationship between the center frequency of received signal spectrum 202, the frequency of local signal 210, and the center frequency of interference wave spectrum 222 described above, after quadrature detection, image signal spectrum 232 for interference wave spectrum 222 appears at the same frequency as received signal spectrum 202. At this time, the modulation phase of received signal 200 and the modulation phase of image signal 230 are the same.

[0022] Figure 4(b) is a diagram that breaks down Figure 3(b) into instantaneous timing. According to Figure 4(b), received signal 200 oscillates between the lowest and highest frequencies of received signal spectrum 202. Also, jammer 220 oscillates between the lowest and highest frequencies of jammer spectrum 222. Furthermore, image signal 230 oscillates between the lowest and highest frequencies of image signal spectrum 232. Here, received signal 200 and image signal 230 oscillate synchronously. Therefore, there is a strong correlation between received signal 200 and image signal 230. Figure 4(c) will be discussed later.

[0023] FIG. 3(c) shows a signal after quadrature detection has been corrected to attenuate image signal spectrum 232. The correction reduces the signal level of image signal spectrum 232, but also reduces the signal level of received signal spectrum 202. FIG. 4(c) is a diagram that breaks down FIG. 3(c) into instantaneous timings. FIG. 4(c) is shown similarly to FIG. 4(b), but as mentioned above, received signal 200 and image signal 230 travel back and forth synchronously, so the correction reduces the signal level of image signal 230 and also reduces the signal level of received signal 200.

[0024] In the first and second comparison targets, the correlation between the received signal 200 and the image signal 230 is strong, so if a correction is made to reduce the signal level of the image signal 230, the signal level of the received signal 200 will also be reduced. On the other hand, if the signal level of the received signal 200 is reduced, the reception characteristics will deteriorate. Therefore, even if a correction is made to reduce the signal level of the image signal 230, it is necessary to prevent the signal level of the received signal 200 from being reduced.

[0025] (2) Configuration of this Example 1 outputs a modulation signal to the oscillation circuit 12 to cause the oscillation circuit 12 to perform modulation. The modulation signal from the modulation signal generator 10 is input to a control voltage terminal of the oscillation circuit 12, and the frequency at which the oscillation circuit 12 oscillates is frequency-modulated by the modulation signal. As a result, the oscillation circuit 12 outputs a local signal that has been frequency-modulated by the modulation signal from the modulation signal generator 10. The local signal output from the frequency divider 14 is also frequency-modulated.

[0026] The first mixer 24a and the second mixer 24b perform quadrature detection on the received signal from the receiving circuit 22 using the frequency-modulated local signal. The first AAF 26a performs band limiting on the I signal from the first mixer 24a. The first AAF 26a outputs the band-limited I signal (hereinafter also referred to as the "I signal") to the first ADC 28a. The second AAF 26b performs band limiting on the Q signal from the second mixer 24b. The second AAF 26b outputs the band-limited Q signal (hereinafter also referred to as the "Q signal") to the second ADC 28b.

[0027] The first ADC 28a performs analog-to-digital conversion on the I signal from the first AAF 26a. The first ADC 28a outputs the I signal converted into a digital signal (hereinafter also referred to as the "I signal"). The second ADC 28b performs analog-to-digital conversion on the Q signal from the second AAF 26b. The second ADC 28b outputs the Q signal converted into a digital signal (hereinafter also referred to as the "Q signal"). The first ADC 28a and the second ADC 28b can be said to be sampling units that sample the quadrature-detected signal at a predetermined timing.

[0028] The correction unit 30 receives the I signal from the first ADC 28a and the Q signal from the second ADC 28b. The correction unit 30 corrects the Q signal using the I signal. The correction is, for example, correction of an IQ quadrature error and a gain error, and corresponds to the correction for attenuating the image signal 230 (image signal spectrum 232) described above. The center frequency of the received signal input to the mixer 24 is set to "ω RX" and the frequency of the local signal input to the mixer 24 is represented as "ω LO ", the I signal "xi" output from the first mixer 24a and the Q signal "xq" output from the second mixer 24b are expressed as follows:

number

[0029] Here, "g" denotes the gain error and "φ" denotes the IQ orthogonality error. Furthermore, the gain error "g" can be approximated from the standard deviation of the gains of the I signal and the Q signal, and the IQ orthogonality error "φ" can be approximated from the correlation function of the I signal and the Q signal. Explanation of these will be omitted. From equation (4), the Q signal corrected by the correction unit 30 (hereinafter referred to as the "corrected Q signal") is expressed as follows:

number

[0030] The first filter 32a performs band limitation on the I signal from the first ADC 28a. The first filter 32a outputs the band-limited I signal (hereinafter also referred to as the "I signal") to the demodulator 34. The second filter 32b performs band limitation on the corrected Q signal from the correction unit 30. The second filter 32b outputs the band-limited corrected Q signal (hereinafter also referred to as the "Q signal") to the demodulator 34.

[0031] The demodulator 34 demodulates the I signal from the first filter 32a and the Q signal from the second filter 32b, and outputs the demodulated audio signal and data. Since a known technique may be used for the demodulation process, a description thereof will be omitted here.

[0032] The following explanation will also use Figures 5(a)-(c), 6(a)-(c), 7(a)-(c), and 8(a)-(c). Figures 5(a)-(c) and 6(a)-(c) correspond to cases where the received signal is unmodulated, as in the first comparison. Figures 7(a)-(c) and 8(a)-(c) correspond to cases where the received signal is modulated, as in the second comparison.

[0033] 5(a)-(c) show processing of a received signal. The horizontal axis represents frequency, and the vertical axis represents signal level. FIG. 5(a) shows the signal before quadrature detection in mixer 24. Shown are received signal 200 output from receiving circuit 22, local signal spectrum 212 of local signal 210 output from frequency divider 14, and interference wave 220 output from receiving circuit 22. Here, the difference between the frequency of received signal 200 and the center frequency of local signal spectrum 212 is equal to the difference between the center frequency of local signal spectrum 212 and the frequency of interference wave 220.

[0034] Figures 6(a)-(c) show the details of the processing of the received signal. Figure 6(a) is a diagram in which Figure 5(a) is broken down into instantaneous timing. Figure 6(a) shows that local signal 210 oscillates between the lowest and highest frequencies of local signal spectrum 212. Figures 6(b)-(c) will be described later.

[0035] 5(b) shows the signal after quadrature detection in mixer 24. Due to the relationship between the frequency of received signal 200, the center frequency of local signal 210, and the frequency of interfering signal 220 described above, received signal spectrum 202 and image signal spectrum 232 appear at the same frequency. In this case, the modulation phase of received signal 200 and the modulation phase of image signal 230 are opposite to each other.

[0036] FIG. 6(b) is a diagram decomposing FIG. 5(b) into instantaneous timings. According to FIG. 6(b), the received signal spectrum 202 and the image signal spectrum 232 overlap on the frequency axis. The received signal 200 and the image signal 230 oscillate between the lowest and highest frequencies of the received signal spectrum 202 or the image signal spectrum 232. However, because the received signal 200 and the image signal 230 have opposite modulation phases, the received signal 200 and the image signal 230 do not overlap at frequencies other than the center frequency of the received signal spectrum 202 or the image signal spectrum 232. Therefore, as mentioned above, the correlation between the received signal 200 and the image signal 230 is small. FIG. 6(c) will be discussed later.

[0037] FIG. 5(c) shows a signal after quadrature detection has been corrected to attenuate the image signal 230. In FIG. 5(b), the correlation between the received signal 200 and the image signal 230 is small, so even if the signal level of the image signal 230 is reduced by correction, the attenuation of the signal level of the received signal 200 is suppressed. FIG. 6(c) is a diagram in which FIG. 5(c) is broken down into instantaneous timings. FIG. 6(c) is shown similarly to FIG. 6(b), but while correction reduces the signal level of the image signal 230, it does not reduce the signal level of the received signal 200.

[0038] 7(a)-(c) show processing of a received signal. The horizontal axis represents frequency, and the vertical axis represents signal level. FIG. 7(a) shows the signal before quadrature detection in mixer 24. Shown are received signal spectrum 202 of received signal 200 output from receiving circuit 22, local signal spectrum 212 of local signal 210 output from frequency divider 14, and interference wave spectrum 222 of interference wave 220 output from receiving circuit 22. Here, the difference between the center frequency of received signal spectrum 202 and the center frequency of local signal spectrum 212 is equal to the difference between the center frequency of local signal spectrum 212 and the center frequency of interference wave spectrum 222.

[0039] Figures 8(a)-(c) show details of the processing of the received signal. Figure 8(a) is a diagram breaking down Figure 7(a) into instantaneous timing. According to Figure 8(a), received signal 200 oscillates between the lowest and highest frequencies of received signal spectrum 202, local signal 210 oscillates between the lowest and highest frequencies of local signal spectrum 212, and jammer 220 oscillates between the lowest and highest frequencies of jammer spectrum 222. In this case, the modulation phase of received signal 200 and the modulation phase of jammer 220 are opposite. Figures 8(b)-(c) will be described later.

[0040] 7(b) shows the signal after quadrature detection in mixer 24. Due to the relationship between the frequency of received signal 200, the center frequency of local signal 210, and the frequency of interfering signal 220 described above, the center frequency of received signal spectrum 202 and the center frequency of image signal spectrum 232 coincide. In this case, the modulation phase of received signal 200 and the modulation phase of image signal 230 are opposite.

[0041] Figure 8(b) is a diagram decomposing Figure 7(b) into instantaneous timing. According to Figure 8(b), the center frequency of the received signal spectrum 202 and the center frequency of the image signal spectrum 232 coincide. The received signal 200 oscillates between the lowest and highest frequencies of the received signal spectrum 202, while the image signal 230 oscillates between the lowest and highest frequencies of the image signal spectrum 232. However, because the received signal 200 and the image signal 230 have opposite modulation phases, they do not overlap at frequencies other than the center frequency. Therefore, as mentioned above, the correlation between the received signal 200 and the image signal 230 is small. Figure 8(c) will be discussed later.

[0042] FIG. 7(c) shows a signal after quadrature detection has been corrected to attenuate the image signal 230. In FIG. 7(b), the correlation between the received signal 200 and the image signal 230 is small, so even if the signal level of the image signal 230 is reduced by correction, the attenuation of the signal level of the received signal 200 is suppressed. FIG. 8(c) is a diagram in which FIG. 7(c) is broken down into instantaneous timings. FIG. 8(c) is shown similarly to FIG. 8(b), but while correction reduces the signal level of the image signal 230, it does not reduce the signal level of the received signal 200.

[0043] This configuration can be realized in hardware terms by the CPU, memory, and other LSIs of any computer, and in software terms by programs loaded into memory, but here we depict functional blocks realized by the cooperation of these. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms using only hardware, only software, or a combination of both.

[0044] According to this embodiment, quadrature detection is performed using a local signal modulated by a modulation signal, so the modulation phases of the received signal and the image signal can be reversed. Furthermore, because the modulation phases of the received signal and the image signal are reversed, the correlation between the received signal and the image signal can be reduced. Because the correlation between the received signal and the image signal is reduced, the signal level of the image signal can be reduced by correction while maintaining the signal level of the received signal. Furthermore, because the signal level of the image signal is reduced while maintaining the signal level of the received signal, the accuracy of correction of the received signal can be improved. Furthermore, because demodulation is performed on the in-phase component of the quadrature-detected received signal and the quadrature component of the corrected received signal, deterioration of the reception characteristics can be suppressed.

[0045] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and treatment processes, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0046] 10 modulation signal generator, 12 oscillator circuit, 14 frequency divider, 20 antenna, 22 receiving circuit, 24 mixer, 26 AAF, 28 ADC, 30 correction unit, 32 filter, 34 demodulator, 100 receiving device.

Claims

1. a modulation signal generator that outputs a modulation signal; an oscillation circuit that outputs a local signal modulated by the modulation signal from the modulation signal generator; a quadrature detector that performs quadrature detection on a received signal using a local signal from the oscillation circuit; a correction unit that corrects a quadrature component of the received signal that has been quadrature detected by the quadrature detector, using an in-phase component of the received signal that has been quadrature detected by the quadrature detector; A receiving device comprising:

2. 2. The receiving device according to claim 1, further comprising a demodulator that demodulates the in-phase component of the received signal quadrature-detected by the quadrature detector and the quadrature component of the received signal corrected by the corrector.

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