JP2003179531A - Ofdm signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an OFDM signal receiver having an improved bit error rate in which a digital intermediate frequency signal obtained through digital conversion of receiving signals of a plurality of receiving systems 1 and 2 subjected to in-phase addition has a power of specified level or above. <P>SOLUTION: The OFDM signal receiver comprises a plurality of receiving systems 1 and 2 including frequency converters 19 and 26, local oscillators 20 and 27, PLL circuits 21 and 28, intermediate frequency circuits 22 and 29, an adder 3 for adding the output signals from the receiving systems 1 and 2, an A/D 7 for converting the output signal from the adder 3 digitally, an OFDM demodulator 8, regulable reference signal generating means 10-12 for feeding phase-shift reference signals to the PLL circuits 21 and 28, and phase shift quantity control means 13-15 for setting the phase-shift regulation state of the regulable reference signal generating means 10-12 such that the demodulated signal has a power of specified level or above and variance thereof is minimized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM signal receiver, and more particularly to an O signal used in terrestrial digital broadcasting.
The present invention relates to an OFDM signal receiving device that receives an FDM signal and has a diversity receiving function suitable for use in a vehicle-mounted receiving device.

[0002]

2. Description of the Related Art Generally, OFDM (Orthogonal Frequency Division Multiplexing; Orthogonal) mounted on a moving body such as an automobile.
Frequency Division Multi
As the moving body moves, the plex signal receiving apparatus suffers fading in which the intensity of the received radio wave changes, and cannot always receive the received signal in a good condition. For this reason, in this type of signal receiving apparatus, in order to avoid that the received signal cannot always be received in a good state due to fading, a diversity receiving function having a plurality of receiving systems is adopted, and reception in a good state is performed. I am able to

Here, FIG. 5 is a block diagram showing an example of the configuration of an OFDM signal receiving apparatus having a plurality of known reception systems, and shows an example having two reception systems as the plurality of reception systems. .

As shown in FIG. 5, this OFDM signal receiving apparatus has a first receiving system 41 and a second receiving system 42.
A first local oscillator 43, a PLL circuit 44, a reference signal oscillator 45, a second local oscillator 46, a diversity signal adding means 47, an OFDM demodulator 48, and a demodulation signal output terminal 49. . In this case, the first reception system 41 includes the antenna 50, the high frequency filter 51, the low noise high frequency amplifier 52, the first frequency mixer 53, and the first frequency mixer 53.
It has an intermediate frequency filter 54, a second frequency mixer 55, a second intermediate frequency filter 56, and an analog-digital converter (A / D) 57, and the second reception system 42 has an antenna 58 and a high frequency wave. The filter 59, the low noise high frequency amplifier 60, the first frequency mixer 61, the first intermediate frequency filter 62, the second frequency mixer 63, the second intermediate frequency filter 64, and the analog-digital converter (A / D) 65
Have and. Further, the diversity signal adding means 47 is
Two digital phase shifters 66 and 67 and a cross correlation detector 6
8 and an adder 69. Note that the two antennas 5
0 and 58 are arranged at relatively distant places.

In the first reception system 41, the high frequency filter 41 has an input end connected to the antenna 50,
The output end is connected to the input end of the low noise high frequency amplifier 52. The output end of the low-noise high-frequency amplifier 52 is connected to the first input end of the first frequency mixer 53. The first frequency mixer 53 has a second input end connected to the output end of the first local oscillator 43 and an output end connected to the input end of the first intermediate frequency filter 54. The output terminal of the first intermediate frequency filter 54 is connected to the first input terminal of the second frequency mixer 55. The second frequency mixer 55 has a second input end connected to the output end of the second local oscillator 46 and an output end connected to the second intermediate frequency filter 56.
Connected to the input end of. The second intermediate frequency filter 56 is
The output end is connected to the input end of the analog-digital converter 57, and the output end of the analog-digital converter 57 is connected to the first input end of the diversity signal adding means 47.

In the second receiving system 42, the high frequency filter 59 has an input end connected to the antenna 58 and an output end connected to the input end of the low noise high frequency amplifier 60.
The output end of the low noise high frequency amplifier 60 is connected to the first input end of the first frequency mixer 61. First frequency mixer 61
Has a second input end connected to the output end of the first local oscillator 43 and an output end connected to the input end of the first intermediate frequency filter 62. The output terminal of the first intermediate frequency filter 62 is connected to the first input terminal of the second frequency mixer 63. The second frequency mixer 63 has a second input end connected to the output end of the second local oscillator 46 and an output end connected to the input end of the second intermediate frequency filter 64. The output terminal of the second intermediate frequency filter 64 is connected to the input terminal of the analog-digital converter 65, and the output terminal of the analog-digital converter 65 is connected to the second input terminal of the diversity signal adding means 47.

Further, the first local oscillator 43 has a control end connected to the output end of the PLL circuit 44 and an output end connected to the first input end of the PLL circuit 44. The PLL circuit 44 is
The second input end is connected to the output end of the reference signal oscillator 45. The OFDM demodulator 54 has an input end connected to the output end of the diversity signal adding means 47 and an output end connected to the demodulation signal output terminal 49.

In the diversity signal adding means 47, the input terminal of the digital phase shifter 66 is connected to the first input terminal of the diversity signal adding means 47, and the output terminal is connected to the first input terminal of the adder 69. It Digital phase shifter 67
Has an input end connected to the second input end of the diversity signal adding means 47 and an output end connected to the second input end of the adder 69. In the cross-correlation detector 68, the first input terminal is connected to the first input terminal of the diversity signal adding means 47, the second input terminal is connected to the second input terminal of the diversity signal adding means 47, and the first control terminal is digital. At the control end of the phase shifter 66,
The second control ends are respectively coupled to the control ends of the digital phase shifter 67. The output terminal of the adder 69 is connected to the output terminal of the diversity signal adding means 47.

The OFDM signal receiving apparatus having the above-described structure operates generally as follows.

In the first receiving system 41, the antenna 50
When an OFDM radio signal is received at, the received signal is
After the unnecessary frequency signal component is removed by the high frequency filter 51, it is amplified by the low noise high frequency amplifier 52 and supplied to the first frequency mixer 53. The first frequency mixer 53 is
This received signal and the first local oscillator 43 supply the first
Frequency mixing is performed with the local oscillation signal to generate a first frequency mixing signal. The first intermediate frequency filter 54 selectively outputs the first intermediate frequency signal from the first frequency mixed signal output from the first frequency mixer 53. The second frequency mixer 55 is
The first intermediate frequency signal supplied from the first intermediate frequency filter 54 and the second local oscillation signal supplied from the second local oscillator 43 are frequency mixed to generate a second frequency mixed signal. The second intermediate frequency filter 56 includes the second frequency mixer 5
The second intermediate frequency signal is selectively output from the second frequency mixed signal output by the signal generator 5. Analog-digital converter 57
Converts the second intermediate frequency signal supplied from the second frequency mixer 55 into a digital intermediate frequency signal and supplies it to the next diversity signal adding means 47.

Further, in the second receiving system 42, the same OF as the signal received by the first receiving system 41 by the antenna 58 is received.
The DM radio signal is received and the same signal receiving operation as the signal receiving operation in the first receiving system 41 described above is performed, and the digital intermediate frequency signal output from the second receiving system 42 is supplied to the diversity signal adding means 47. To be done.

In this case, the first local oscillation signal generated by the first local oscillator 43 is a PL to which the first local oscillation signal and the reference signal output from the reference signal oscillator 45 are supplied.
The stabilized oscillation frequency is set by the control of the L circuit 44.

Next, in the diversity signal adding means 47, the digital phase shifter 66 shifts the phase of the digital intermediate frequency signal supplied from the first receiving system 41 as described later, and the digital phase shifter 67 shifts the second phase shifter 67 to the second phase. The digital intermediate frequency signal supplied from the reception system 42 is phase-shifted as described later. Further, the cross-correlation detector 68 uses the first reception system 41
Digital intermediate frequency signal supplied from the second receiving system 4
The cross-correlation with the digital intermediate frequency signal supplied from 2 is detected, and the phase of the digital intermediate frequency signal output from the digital phase shifter 66 and the digital intermediate output from the digital phase shifter 67 are detected based on the detection result. The digital phase shifters 66 and 67 are arranged so that the frequency signals have the same phase.
Correct the phase shift amount of. By performing such phase correction, the digital intermediate frequency signal output from the digital phase shifter 66 and the digital intermediate frequency signal from the digital phase shifter 67 are in-phase added by the adder 69, and the added digital intermediate frequency signal is added. Is output as.

Thereafter, the OFDM demodulator 48 OFDM demodulates the added digital intermediate frequency signal output from the diversity signal addition means 47, and the demodulated signal is supplied to a utilization circuit (not shown) through the demodulated signal output terminal 49. .

According to the OFDM signal receiving apparatus, the diversity signal adding means 47 makes the phases of the two digital intermediate frequency signals in-phase and adds these signals to obtain the added digital intermediate frequency signal. The signal power of the added digital intermediate frequency signal is maximized, and the OFDM radio signal can be received in a good reception state.

[0016]

The above-mentioned known OFDM signal receiving apparatus having a plurality of receiving systems can realize a relatively good receiving state when applied to a vehicle. The diversity signal adding means 47 for performing digital signal processing is used in the signal receiving device,
Among them, the digital phase shifters 66 and 67 and the cross correlation detector 6
In the case where 8 is configured, since it includes a large number of multipliers, a large number of dividers, and a complex correlator composed of logic circuits, the circuit scale becomes enormous even if it is configured by an integrated circuit (IC), resulting in consumption. The power will increase.

Further, in the OFDM signal receiving apparatus having a plurality of known receiving systems, since the analog circuit portions of the receiving systems 41 and 42 are independent of each other, the scale of the analog circuit portion is large and the whole. The structure becomes large and the manufacturing cost increases.

An OFDM signal receiving apparatus designed to solve such a problem has already been proposed by the same applicant as the present applicant.

FIG. 6 is a block diagram showing an example of the main configuration of the proposed OFDM signal receiving apparatus, and shows an example in which a plurality of receiving systems are two systems.

As shown in FIG. 6, this OFDM signal receiving apparatus has a first receiving system 70 and a second receiving system 71.
, An adder 72, a second frequency mixer 73, a second local oscillator 74, a second intermediate frequency filter 75, an analog-digital converter (A / D) 76, an OFDM demodulator (DET) 77. , Demodulation signal output terminal 78, reference signal oscillator 79, phase shifters 80 and 81, and power detector (PW
DET) 82 and a phase controller (CONT) 83. In this case, the first reception system 70 includes the antenna 84.
A high frequency filter 85 and a low noise high frequency amplifier 86
A first frequency mixer 87, a first local oscillator 88,
PLL circuit (PLL) 89 and first intermediate frequency filter 9
0, the second reception system 71 includes an antenna 91, a high frequency filter 92, a low noise high frequency amplifier 93, and a first
It has a frequency mixer 94, a first local oscillator 95, a PLL circuit (PLL) 96, and a first intermediate frequency filter 97.

In the first receiving system 70, the high frequency filter 85 has an input end connected to the antenna 84,
The output terminal is connected to the low noise high frequency amplifier 86. The output end of the low noise high frequency amplifier 86 is connected to the first input end of the first frequency mixer 87. The first frequency mixer 87 has a second input end connected to the output end of the first local oscillator 88 and an output end connected to the input end of the first intermediate frequency filter 90. The input terminal of the first local oscillator 88 is connected to the output terminal of the PLL circuit 89, and the output terminal is connected to the input terminal of the PLL circuit 89. In the PLL circuit 89, the control input terminal is the phase shifter 8
0, the first intermediate frequency filter 90 is connected to
The output terminal is connected to the first input terminal of the adder 72.

In the second receiving system 71, the high frequency filter 92 has an input end connected to the antenna 91 and an output end connected to the low noise high frequency amplifier 93. The output end of the low noise high frequency amplifier 93 is connected to the first input end of the first frequency mixer 94. The first frequency mixer 94 has a second input end connected to the output end of the first local oscillator 95 and an output end connected to the input end of the first intermediate frequency filter 93. The first local oscillator 95 has an input end connected to the output end of the PLL circuit 96 and an output end connected to the input end of the PLL circuit 96. The control input terminal of the PLL circuit 96 is connected to the output terminal of the phase shifter 81. The output terminal of the first intermediate frequency filter 97 is connected to the second input terminal of the adder 72.

The output terminal of the adder 72 is connected to the first input terminal of the second frequency mixer 73. The second frequency mixer 73 has a second input end connected to the output end of the second local oscillator 74 and an output end connected to the input end of the second intermediate frequency filter 75. The output terminal of the second intermediate frequency filter 75 is connected to the input terminal of the analog-digital converter 76.
The output terminal of the analog-digital converter 76 is connected to the input terminal of the OFDM demodulator 77 and the input terminal of the power detector 82. The output end of the OFDM demodulator 77 is connected to the demodulation signal output terminal 78, and the output end of the power detector 82 is connected to the input end of the phase control unit 83. The input ends of the phase shifters 80 and 81 are connected to the output end of the reference signal oscillator 79. Each of the phase shifters 80 and 81 has a control input end coupled to a control output end of the phase control unit 83.

The OFDM signal receiving apparatus according to the above proposal is
In general, it operates as follows.

The same OFD with the two antennas 84 and 91
When the M wireless signals are received, the received signals are amplified by the low-noise high-frequency amplifiers 86 and 93 after the unnecessary frequency signal components are removed by the high-frequency filters 85 and 92, respectively. It is supplied to the mixers 87 and 94. The first frequency mixers 87 and 94 frequency-mix the received signal and the first local oscillation signals supplied from the first local oscillators 88 and 95, and generate first frequency mixing signals, respectively. At this time, the PLL circuits 89 and 96 phase-control the first local oscillation signal generated by the first local oscillators 88 and 95 by the reference signal supplied from the reference signal oscillator 79 through the phase shifters 80 and 81, and The frequency of the first local oscillation signal of the first local oscillators 88 and 95 is set according to the control result. The first intermediate frequency filters 90 and 97 have a first
The first intermediate frequency signal is selected and output from the first frequency mixed signals output from the frequency mixers 87 and 94, and the two selected and output first intermediate frequency signals are supplied to the adder 72.

The adder 72 adds and synthesizes the two supplied first intermediate frequency signals in the in-phase state to form an added first intermediate frequency signal, and supplies the added first intermediate frequency signal to the second frequency mixer 73. The second frequency mixer 73 frequency-mixes the added first intermediate frequency signal and the second local oscillation signal supplied from the second local oscillator 74 to generate a second frequency mixing signal. The second intermediate frequency filter 75 selectively outputs the second intermediate frequency signal from the second frequency mixed signal output by the second frequency mixer 73. The analog-digital converter 76 converts the second intermediate frequency signal supplied from the second intermediate frequency filter 75 into a digital intermediate frequency signal, and supplies the obtained digital intermediate frequency signal to the demodulator 77 and the power detector 82. To do. The demodulator 77 OFDM demodulates the digital intermediate frequency signal and supplies the demodulated signal to a utilization circuit (not shown) through the demodulated signal output terminal 78. The power detector 82 detects the amount of power corresponding to the digital intermediate frequency signal and supplies the detection result to the phase controller 83. The phase control unit 83 individually controls the phase shift amounts of the phase shifters 80 and 81 based on the detection result of the power detector 82, and P
The phase amount of the reference signal supplied to the LL circuits 89 and 96 is individually changed, and the power amount detected by the power detector 82 is adjusted to be maximum.

According to this OFDM signal receiving apparatus, the amount of power of the digital intermediate frequency signal OFDM-demodulated by the demodulator 77 is maximized by controlling the amount of phase shift of the phase shifters 80 and 81 as described above. Therefore, the radio signal can be received in a good state.

By the way, the receiving device according to the above-mentioned proposal can solve various problems in the conventional OFDM signal receiving device of this kind, but when fading occurs in the incoming radio wave, the received signal band It is difficult to improve the bit error rate (BER, that is, the bit error rate) when the level of a specific frequency component inside is extremely lowered.

The present invention has been made in view of the above technical background, and an object thereof is power in a digital intermediate frequency signal obtained by digitally converting an addition intermediate frequency signal obtained by in-phase addition of reception signals of a plurality of reception systems. Is more than a specified value,
And OFDM with improved bit error rate
It is to provide a signal receiving device.

[0030]

In order to achieve the above object, the present invention provides an antenna, a frequency mixer for converting the frequency of an OFDM signal received by the antenna, and a local oscillator signal for the frequency mixer. A plurality of receiving systems having a local oscillator for supplying a frequency, a PLL circuit for setting an oscillation frequency of the local oscillator, an intermediate frequency circuit for selecting an intermediate frequency signal from an output frequency mixing signal of the frequency mixer, and a plurality of receiving systems for outputting. Adder for adding intermediate frequency signals, an analog-digital converter for converting the added intermediate frequency signals output from the adder into digital signals, an OFDM demodulator for OFDM demodulating digital signals, and a plurality of receiving systems An adjustable reference signal generating means for supplying a reference signal having a phase shifted to each PLL circuit and an OFDM demodulator are connected, And a phase shift amount control means for setting the phase shift adjustment state of the adjustable reference signal generating means so that the power of the demodulated signal of the signal generator becomes a predetermined value or more and the dispersion of the power of the demodulated signal is minimized. Equipped with the means.

According to the above means, each P of the plurality of receiving systems is
In order to supply the phase-shifted reference signals to the LL circuits, the phase shift amount control means connected to the OFDM demodulator is used to adjust the phase shift amount of the adjustable reference signal generation means.
By performing the adjustment, the power of the demodulated signal of the OFDM demodulator is set to a predetermined value or more and the signal dispersion of the demodulated signal is set to be the minimum, so that the OFDM signal receiving apparatus of this type can be Similarly, good signal reception can be performed, and signal reception can be performed in a state where the bit error rate is minimum.

In this case, the adjustable reference signal generating means in the above means comprises a reference signal oscillator common to a plurality of receiving systems for generating a reference signal, and a plurality of phase shifters for individually shifting the reference signals. Can be configured.

With such a structure, the structure of the adjustable reference signal generating means can be simplified and the signal loss due to the provision of a plurality of phase shifters can be reduced.

The adjustable reference signal generating means in the above means may be constituted by a plurality of digital synthesizers which generate the reference signals which are individually phase-shifted by the supply of the phase data. .

With such a configuration, the phase and frequency of the reference signal can be digitally controlled, so that not only the configuration of the adjustable reference signal generating means is simplified but also the control processing is simplified. Can be achieved.

Further, the phase shift amount control means in the above means may be configured to include a power detector of the demodulated signal of the OFDM demodulator and a power dispersion detector of the demodulated signal of the OFDM demodulator. .

With this configuration, the power detection of the demodulated signal and the dispersion detection of the demodulated signal can be individually performed,
Both detections do not interfere with each other.

Further, in the above-mentioned means, the addition intermediate frequency signal is secondly added between the adder and the analog-digital converter.
A second frequency mixer for frequency conversion into an intermediate frequency signal and a second frequency mixer
The second local oscillator for supplying the second local oscillation signal to the frequency mixer and the second frequency from the output frequency mixing signal of the second frequency mixer
The second intermediate frequency circuit for selecting the intermediate frequency signal is provided.

With such a configuration, the receiving device of the double superheterodyne system is configured, so that it is possible to relatively freely select each frequency band of the first local oscillation signal and the second local oscillation signal. Become.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 relates to one embodiment of an OFDM signal receiving apparatus according to the present invention, and is a block diagram showing the configuration of the main part thereof, showing an example in which a plurality of receiving systems are two systems. is there.

As shown in FIG. 1, the OFDM signal receiving apparatus according to this embodiment includes a first receiving system 1 and a second receiving system 1.
The reception system 2, the adder 3, the second frequency mixer 4, the second local oscillator 5, the second intermediate frequency filter 6, the analog-digital converter (A / D) 7, the OFDM demodulator ( DET) 8, demodulated signal output terminal 9, reference signal oscillator 10, phase shifters 11 and 12, and power detector (PWD
ET) 13, a dispersion detector (DV DET) 14, and a phase controller (CONT) 15. In this case, the part consisting of the reference signal oscillator 10 and the phase shifters 11 and 12 constitutes the adjustable reference signal generating means, and the part consisting of the power detector 13, the dispersion detector 14 and the phase controller 15 is the phase shifter. It constitutes a quantity control means.

The first receiving system 1 includes an antenna 16
A high frequency filter 17 and a low noise high frequency amplifier 18
A first frequency mixer 19, a first local oscillator 20,
PLL circuit (PLL) 21 and first intermediate frequency filter 2
The second reception system 2 includes an antenna 23, a high frequency filter 24, a low noise high frequency amplifier 25, a first frequency mixer 26, a first local oscillator 27, and a PLL circuit (PLL) 28. And a first intermediate frequency filter 29.

In the first receiving system 1, the high frequency filter 17 has an input end connected to the antenna 16 and an output end connected to the low noise high frequency amplifier 18. The output of the low-noise high-frequency amplifier 18 is connected to the first input of the first frequency mixer 19. The first frequency mixer 19 has a second
The input end is connected to the output end of the first local oscillator 20, and the output end is connected to the input end of the first intermediate frequency filter 22.
The first local oscillator 20 has an input end connected to the output end of the PLL circuit 21, and an output end connected to the input end of the PLL circuit 21. The control input end of the PLL circuit 21 is connected to the output end of the phase shifter 11. The output terminal of the first intermediate frequency filter 22 is connected to the first input terminal of the adder 3.

In the second receiving system 2, the high frequency filter 24 has an input end connected to the antenna 23 and an output end connected to the low noise high frequency amplifier 25. The output end of the low noise high frequency amplifier 25 is connected to the first input end of the first frequency mixer 26. The first frequency mixer 26 has a second input end connected to the output end of the first local oscillator 27, and an output end connected to the first local oscillator 27.
It is connected to the input terminal of the intermediate frequency filter 29. The first local oscillator 27 has an input end connected to the output end of the PLL circuit 28 and an output end connected to the input end of the PLL circuit 28.
The control input terminal of the PLL circuit 28 is connected to the output terminal of the phase shifter 12. The output terminal of the first intermediate frequency filter 29 is connected to the second input terminal of the adder 3.

The output terminal of the adder 3 is connected to the first input terminal of the second frequency mixer 4. Second frequency mixer 4
Has a second input end connected to the output end of the second local oscillator 5 and an output end connected to the input end of the second intermediate frequency filter 6. The output terminal of the second intermediate frequency filter 6 is connected to the input terminal of the analog-digital converter 7. The output terminal of the analog-digital converter 7 is connected to the input terminal of the OFDM demodulator 8, the input terminal of the power detector 13 and the input terminal of the dispersion detector 14. The output end of the OFDM demodulator 8 is connected to the demodulation signal output terminal 9. The output terminals of the power detector 13 and the dispersion detector 14 are connected to the input terminals of the phase controller 15, respectively. The input ends of the phase shifters 11 and 12 are connected to the output end of the reference signal oscillator 10, and the control input ends thereof are respectively coupled to the control output ends of the phase controller 15.

O according to this embodiment having the above structure
The FDM signal receiving apparatus generally operates as follows.

In the first receiving system 1, when the OFDM radio signal is received by the antenna 16, the received signal is amplified by the low noise high frequency amplifier 18 after the unnecessary frequency signal component is removed by the high frequency filter 17. It is supplied to the first frequency mixer 19. The first frequency mixer 19 frequency-mixes the received signal and the first local oscillation signal supplied from the first local oscillator 20 to generate a first frequency mixing signal. At this time, the PLL circuit 20 uses the first local oscillator 2
The phase of the first local oscillation signal generated by 0 is controlled by the reference signal supplied from the reference signal oscillator 10 through the phase shifter 11, and the first local oscillation of the first local oscillator 20 is performed by the control signal obtained as a result of the phase control. The frequency (phase) of the signal is set. The phase shift amount of the reference signal in the phase shifter 11 will be described later. The first intermediate frequency filter 22 is
The first intermediate frequency signal is selected and output from the first frequency mixed signal output from the first frequency mixer 19, and the selected and output first intermediate frequency signal is supplied to the adder 3.

In the second reception system 2, when the same OFDM radio signal as the OFDM radio signal received by the first reception system 1 is received by the antenna 23, the reception signal is an unnecessary frequency signal by the high frequency filter 24. After the component is removed, it is amplified by the low noise high frequency amplifier 25 and supplied to the first frequency mixer 26. The first frequency mixer 26 is
The received signal and the first local oscillator 27 supply the first
Frequency mixing is performed with the local oscillation signal to generate a first frequency mixing signal. Also at this time, the PLL circuit 28 phase-controls the first local oscillation signal generated by the first local oscillator 27 by the reference signal supplied from the reference signal oscillator 10 through the phase shifter 12, and the result of the phase control is obtained. The frequency (phase) of the first local oscillation signal of the first local oscillator 27 is set by the control signal. The phase shift amount of the reference signal in the phase shifter 12 will be described later. The first intermediate frequency filter 29 selectively outputs the first intermediate frequency signal from the first frequency mixed signal output from the first frequency mixer 26, and supplies the selectively output first intermediate frequency signal to the adder 3.

The adder 3 includes the first and second receiving systems 1 and 2.
The two first intermediate frequency signals respectively supplied from the above are added and combined in the in-phase state to form an added first intermediate frequency signal, and the added first intermediate frequency signal is supplied to the second frequency mixer 4. The second frequency mixer 4 frequency-mixes the added first intermediate frequency signal and the second local oscillation signal supplied from the second local oscillator 5 to generate a second frequency mixing signal, and the second frequency mixing signal is generated. Is supplied to the second intermediate frequency filter 6. The second intermediate frequency filter 6 selectively outputs the second intermediate frequency signal from the supplied second frequency mixed signal, and supplies the obtained second intermediate frequency signal to the analog-digital converter 7.
The analog-digital converter 7 converts the supplied second intermediate frequency signal into a digital intermediate frequency signal, and supplies the obtained digital intermediate frequency signal to the demodulator 8. Demodulator 8
The digital intermediate frequency signal is OFDM demodulated, the demodulated signal is supplied to a utilization circuit (not shown) through the demodulated signal output terminal 9, and at the same time, the demodulated signal is supplied to the power detector 13 and the dispersion detector 14, respectively.

The power detector 13 detects the amount of power corresponding to the demodulated signal, supplies the detection result to the phase controller 15, and the dispersion detector 14 detects the signal dispersion in the demodulated signal,
The detection result is supplied to the phase controller 15.

Next, FIG. 2 shows a phase shifter 1 executed by the phase amount control means including the power detector 13, the dispersion detector 14, and the phase controller 15 of the OFDM signal receiving apparatus shown in FIG.
It is a flow chart which shows the operation process of 0 and 11 phase shift control.

3A, 3B, and 3C show the frequency spectra of two received signals having different signal dispersion levels and the frequency of the transmitted signal which is the original signal of the received signals. It is a waveform diagram showing an example of a spectrum, (a)
Is a transmission signal waveform, (b) is a reception signal waveform with a relatively large signal dispersion, (c) is a reception signal waveform with a relatively small signal dispersion, the horizontal axis is the frequency, and the vertical axis is the signal level.

As shown in FIG. 3A, when a rectangular wave signal having a constant signal level within a prescribed frequency range is transmitted as a radio signal as a transmission signal waveform, the OFDM signal is generated due to fading during transmission. The received signal received by the signal receiving device becomes a substantially rectangular wave signal in which the signal level fluctuates within the specified frequency range, as shown in FIG. 3B or 3C. In this case, the signal waveform shown in FIG. 3B is a signal when the fluctuation of the signal level within the specified frequency range is relatively large with respect to the average signal level and the signal dispersion amount is large. FIG. 3C is a waveform when the fluctuation of the signal level within the specified frequency range in FIG. 3C is a relatively small fluctuation with respect to the average signal level and the signal dispersion amount is small.

The OFDM signal receiving apparatus according to this embodiment focuses on the signal dispersion amount as well as the signal power of the received signal. As will be described later, the setting of the phase amount control means sets the demodulated signal power to a predetermined value. The value is equal to or more than the value, and the signal dispersion amount of the demodulated signal is set to be the smallest.

Now, the operation process of the phase shift control executed by the phase amount control means of the OFDM signal receiving apparatus shown in FIG. 1 will be described with reference to the flow chart shown in FIG.

First, in step S1, the phase amount control means causes the phase shifter 10 so that the power of the demodulated signal becomes the maximum power (P0) based on the detection result of the power detector 13.
The phase difference (φ0) between the two reference signals output from 11 is searched.

Next, in step S2, the phase amount control means causes the phase shifters 10 and 11 so that the phase difference between the two reference signals output from the phase shifters 10 and 11 becomes (φ0).
Adjust and set the phase shift amount of.

Next, in step S3, the phase amount control means measures the signal power (P) of the demodulated signal in the power detector 13.

In the next step S4, the phase amount control means measures the signal dispersion (dσ) of the demodulated signal in the dispersion detector 14.

Subsequently, in step S5, the phase amount control means uses the signal power level decrease (dP) from the maximum power (P0) preset in the phase controller 15 to determine the maximum power (P0) and the signal power. Whether or not the signal power (P) is smaller than the maximum power (P0) minus the signal power level decrease (dP) with (P) (P <
It is determined whether or not the condition of P0-dP is satisfied).
When it is determined that the condition of P <P0-dP is satisfied (Y), the process proceeds to the next step S6, while P <P
When it is determined that the condition P0-dP is not satisfied (N), the process proceeds to another step S12.

Next, in step S6, the phase amount control means sets the phase difference (φ0) of the reference signals output from the phase shifters 10 and 11 by the phase control unit 15 to the currently set phase difference (φ0). The phase shift amount of each of the phase shifters 10 and 11 is adjusted and set so that the phase difference (φ + dφ) is increased by an amount (dφ).

Next, in step S7, the phase amount control means measures the signal power (P +) of the demodulated signal at the phase difference (φ + dφ) set in step S6 in the power detector 13.

In step S8, the phase amount control means uses the signal power level decrease (dP) from the preset maximum power (P0) in the phase controller 15 to determine the maximum power (P0) and step S7. The signal power (P +) is the maximum power (P +) between the signal power (P +) measured in
0) less the signal power level decrease (dP) is subtracted (whether the condition of P + <P0-dP is satisfied) is determined. And P + <P0-d
When it is determined that the condition of P is satisfied (Y), the process proceeds to the next step S9, while when it is determined that the condition of P + <P0-dP is not satisfied (N), the previous step S9 is performed.
Returning to step 3, the operations after step S3 are repeatedly executed again.

Subsequently, in step S9, the phase amount control means determines the phase difference (φ0) of the reference signals output from the phase shifters 10 and 11 by the phase control unit 15 in step S9.
A little more than the phase difference (φ + dφ) set in 6 (2d
The phase shift amounts of the phase shifters 10 and 11 are adjusted and set so that the phase difference (φ-dφ) is reduced by φ).

In step S10, the phase amount control means measures the signal power (P-) of the demodulated signal when the power detector 13 has the phase difference (φ-dφ) set in step S9.

Next, in step S11, the phase amount control means uses the signal power level decrease (dP) from the preset maximum power (P0) in the phase controller 15 to determine the maximum power (P0) and step. Whether the signal power (P-) between the signal power (P-) measured in S10 is less than the maximum power (P0) minus the signal power level decrease (dP) (P- < It is determined whether or not the condition of P0-dP is satisfied). And P- <P0
When it is determined that the condition of -dP is satisfied (Y), the process returns to the first step S1 and the operations after step S1 are repeatedly executed again, while the condition of P- <P0-dP is not satisfied. When judged (N), the previous step S
Returning to step 3, the operations after step S3 are repeatedly executed again.

Further, in step S12, the phase amount control means measures the signal dispersion value (σ0) of the demodulated signal in the dispersion detector 14.

Next, in step S13, the phase amount control means sets the signal dispersion value between the signal dispersion value (σ0) measured in step S12 in the phase control unit 15 and the preset specified signal dispersion value (dσ). It is determined whether or not (σ0) is larger than the specified signal variance value (dσ) (whether or not the condition of σ0> dσ is satisfied). And σ0> d
When it is determined that the condition of σ is satisfied (Y), the process proceeds to the next step S14, while when it is determined that the condition of σ0> dσ is not satisfied (N), another step S22 is performed.
Move to.

In the next step S14, the phase amount control means sets the phase difference (φ0) of the reference signals output from the phase shifters 10 and 11 by the phase controller 15 to the currently set phase difference (φ). The phase shift amounts of the phase shifters 10 and 11 are adjusted and set so that the phase difference (φ + dφ) is increased by a slight amount (dφ).

Subsequently, in step S15, the phase amount control means measures the signal dispersion amount (σ +) of the demodulated signal at the phase difference (φ + dφ) set in step S14 in the dispersion detector 14.

Next, in step S16, the phase amount control means sets the signal dispersion between the signal dispersion value (σ +) measured in step S15 in the phase control section 15 and the preset specified signal dispersion value (dσ). It is determined whether the value (σ +) is larger than the specified signal variance value (dσ) (whether the condition of σ +> dσ is satisfied). And σ +> dσ
When it is determined that the condition (4) is satisfied (Y), the process proceeds to the next step S17, while when it is determined that the condition (σ +> dσ) is not satisfied (N), the process proceeds to another step S23.

Then, in step S17, the phase amount control means causes the phase control unit 15 to shift the phase shifters 10 and 11.
The phase difference (φ0) of the reference signal output from the device is slightly larger than the phase difference (φ + dφ) set in step S14 (2
The phase shift amounts of the phase shifters 10 and 11 are adjusted and set so that the phase difference (φ-dφ) is reduced by dφ).

In step S18, the phase amount control means measures the signal dispersion amount (σ-) of the demodulated signal when the phase difference (φ-dφ) set in step S17 is set in the dispersion detector 14.

Subsequently, in step S19, the phase amount control means outputs a signal between the signal dispersion value (σ−) measured in step S18 in the phase control unit 15 and the preset specified signal dispersion value (dσ). It is determined whether the variance value (σ−) is larger than the specified signal variance value (dσ) (whether the condition of σ−> dσ is satisfied). And σ-> d
When it is determined that the condition of σ is satisfied (Y), the process proceeds to the next step S20, while when it is determined that the condition of σ−> dσ is not satisfied (N), another step S24 is performed.
Move to.

Next, in step S20, the phase amount control means determines the phase difference (φ0) of the reference signals output from the phase shifters 10 and 11 by the phase control unit 15 in step S20.
It is slightly larger than the phase difference (φ-dφ) set in 17 (2d
The phase shift amounts of the phase shifters 10 and 11 are adjusted and set so that the phase difference (φ + dφ) is increased by φ).

Next, in step S21, the phase amount control means measures the signal dispersion value (σ) of the demodulated signal at the phase difference (φ + dφ) set in step S20 in the dispersion detector 14.

In step S21, the phase amount control means sets the signal dispersion value (σ) measured by the dispersion detector 14 to the specified signal dispersion value (dσ). After this setting is performed, the process returns to step S3 and again to step S3.
The operations after 3 are repeatedly executed.

In step S22, the phase amount control means sets the signal dispersion amount (σ0) measured by the dispersion detector 14 to the specified signal dispersion value (dσ). After this setting is performed, the process returns to step S3, and the operations after step S3 are repeatedly executed again.

Further, in step S23, the phase amount control means sets the signal dispersion amount (σ +) measured by the dispersion detector 14 to the specified signal dispersion value (dσ). After this setting is performed, the process returns to step S3, and the operations after step S3 are repeatedly executed again.

Further, in step S24, the phase amount control means sets the signal dispersion amount (σ−) measured by the dispersion detector 14 to the specified signal dispersion value (dσ). After this setting is performed, the process returns to step S3, and the operations after step S3 are repeatedly executed again.

As described above, according to the OFDM signal receiving apparatus of this embodiment, the phase shifter 1 by the phase amount control means is used.
By controlling the amount of phase shift with respect to the reference signals 1 and 12, the setting is made so that the signal dispersion of the demodulated signal is minimized when the signal power of the demodulated signal of the OFDM demodulator 8 is set to a predetermined value or more. Not only can the same good signal reception as that of the conventional OFDM signal receiving apparatus of this type be performed, but also the signal reception can be performed in a state where the bit error rate (BER) is minimized.

In the above embodiment, an example in which the adjustable reference signal generating means having the reference signal oscillator 10 and the two phase shifters 11 and 12 is used has been described. The adjustable reference signal generating means used in the invention comprises a reference signal oscillator 10 and two phase shifters 11 and 12.
The configuration is not limited to the above configuration, and may be another configuration, for example, a digital synthesizer configuration.

FIG. 4 is a block diagram showing an example of the adjustable reference signal generating means of the digital synthesizer configuration.

As shown in FIG. 4, the adjustable reference signal generating means includes digital synthesizers 30 and 31 having ROMs 30R and 31R incorporated therein, digital-analog converters (D / A) 32 and 33, and a band. It includes pass filters 34 and 35.

The output end of the digital synthesizer 30 is connected to the input end of the digital-analog converter 32, and the clock signal, the frequency data and the phase data are supplied thereto. The digital synthesizer 301, the output end of which is connected to the input end of the digital-analog converter 33, is supplied with the clock signal, the frequency data, and the phase data, respectively. The output terminal of the digital-analog converter 32 is connected to the input terminal of the bandpass filter 34, and
The output end of the analog converter 33 is the bandpass filter 3
5 is connected to the input terminal. The bandpass filter 34 is
The output terminal is connected to the control input terminal (reference signal input terminal) of the PLL circuit 21 (see FIG. 1), and the bandpass filter 35
Has an output end connected to the control input end (reference signal input end) of the PLL circuit 28 (see FIG. 1). In this case, the ROM 3 built in each of the digital synthesizers 30 and 31
In 0R and 31R, one cycle of sine wave data is stored in a form in which both the amplitude and the phase are discretized.

The adjustable reference signal generating means of the digital synthesizer configuration having the above configuration operates as follows.

When the same clock signal and frequency data are supplied to the digital synthesizers 30 and 31, the built-in ROMs 30R and 31R generate sine wave data of the same frequency in synchronization with the clock signal. Further, the digital synthesizers 30 and 31 are supplied with digital phase data from the phase amount control means, and the phases of the sine wave data generated by the ROMs 30R and 31R are set by the digital phase data. Digital synthesizer 30, 31
The sine wave data output from is converted into an analog sine wave signal by analog-digital converters 32 and 33, respectively. Unwanted frequency components are removed from these analog sine wave signals by the bandpass filters 34 and 35, and the analog sine wave signals are respectively used as reference signals in FIG.
Is supplied to the PLL circuits 21 and 28 shown in FIG.

By using the adjustable reference signal generating means having such a digital synthesizer structure, the phase and frequency of the reference signal can be digitally controlled and processed.
Not only can the structure of the adjustable reference signal generating means be simplified, but also the control processing can be simplified.

In the above embodiment, the OFD
The M signal receiving device includes a second frequency mixer 4, a second local oscillator 5 between the adder 3 and the analog-digital converter 7.
The example of the double superheterodyne system having the second intermediate frequency filter 6 has been described, but the OFDM signal receiving apparatus according to the present invention is not limited to the double superheterodyne system, and the received signal to be used , And the frequency of the first intermediate frequency signal,
It is also possible to omit the second frequency mixer 4, the second local oscillator 5, and the second intermediate frequency filter 6 and change to a single superheterodyne system.

Further, the OFDM in the above embodiment
The signal receiving device is suitable for use in vehicles such as automobiles, but the OFDM signal receiving device according to the present invention is not limited to such an application, and can be applied to other applications. is there.

[0092]

As described above, according to the invention described in claim 1, in order to supply the phase-shifted reference signals to the respective PLL circuits of the plurality of reception systems, the shift circuit connected to the OFDM demodulator is used. The amount of phase shift of the adjustable reference signal generating means is adjusted by using the phase amount control means. By performing the adjustment, the power of the demodulated signal of the OFDM demodulator is made equal to or higher than a predetermined value, and the signal of the demodulated signal is adjusted. Since the setting is such that the dispersion is minimized, it is possible to perform good signal reception as in the conventional OFDM signal receiving apparatus of this type, and to perform signal reception in the state where the bit error rate is the minimum. The effect is that you can do it.

According to the invention described in claim 2, the structure of the adjustable reference signal generating means can be simplified,
There is an effect that the signal loss due to the provision of the plurality of phase shifters can be reduced.

Further, according to the invention of claim 3,
Since the phase and frequency of the reference signal can be digitally controlled, there is an effect that not only the configuration of the adjustable reference signal generating means can be simplified but also the control processing can be simplified.

Further, according to the invention described in claim 4, the power detection of the demodulated signal and the dispersion detection of the demodulated signal can be separately performed, and there is an effect that both detections do not interfere with each other. .

Further, according to the invention of claim 5,
Since the double super-heterodyne type receiver is configured, it is possible to relatively freely select each frequency band of the first local oscillation signal and the second local oscillation signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of an OFDM signal receiving apparatus according to the present invention and showing a main configuration thereof.

2 is a flowchart showing an operation process of phase shift control of a phase shifter executed by a phase amount control means including a power detector, a dispersion detector, and a phase controller of the OFDM signal receiving apparatus shown in FIG. is there.

FIG. 3 shows two demodulated signals having different degrees of signal dispersion,
It is a signal waveform diagram which shows each example of the transmission signal which is the original signal of the demodulation signal.

FIG. 4 is a block diagram showing an example of an adjustable reference signal generating means having a digital synthesizer configuration.

FIG. 5 is a block diagram showing an example of a configuration of an OFDM signal receiving apparatus having a plurality of known receiving systems.

FIG. 6 is a block diagram showing an example of the main configuration of an already proposed OFDM signal receiving apparatus.

[Explanation of symbols]

1st receiving system 2 Second receiving system 3 adder 4 Second frequency mixer 5 Second local oscillator 6 Second intermediate frequency filter 7, 32, 33 Analog-digital converter (A / D) 8 OFDM demodulator (DET) 9 Demodulation signal output terminal 10 Reference signal oscillator 11,12 Phase shifter 13 Power detector (PW DET) 14 Dispersion detector (DV DET) 15 Phase control unit (CONT) 16,23 antenna 17, 24 High frequency filter 18,25 Low noise high frequency amplifier 19, 26 First frequency mixer 20, 27 1st local oscillator 21, 28 PLL circuit (PLL) 22, 29 First intermediate frequency filter 30, 31 Digital Synthesizer 34, 35 bandpass filter

Claims (5)

[Claims] 1. Each receiving system sets an antenna, a frequency mixer for frequency-converting an OFDM signal received by the antenna, a local oscillator for supplying a local oscillation signal to the frequency mixer, and an oscillation frequency of the local oscillator. P
An LL circuit, a plurality of reception systems having an intermediate frequency circuit that selects an intermediate frequency signal from the output frequency mixing signals of the frequency mixer, an adder that adds the intermediate frequency signals output from the plurality of reception systems, and An analog-digital converter for converting the added intermediate frequency signal output from the adder into a digital signal, an OFDM demodulator for OFDM demodulating the digital signal, and a reference phase-shifted to each PLL circuit of the plurality of reception systems. An adjustable reference signal generating means for supplying a signal and the OF demodulator,
Phase shift amount control for setting the phase shift adjustment state of the adjustable reference signal generating means so that the power of the demodulated signal of the DM demodulator becomes a predetermined value or more and the dispersion of the power of the demodulated signal is minimized. And an OFD characterized by comprising:
M signal receiving device. 2. The adjustable reference signal generating means comprises a reference signal oscillator common to the plurality of receiving systems for generating a reference signal, and a plurality of phase shifters for individually shifting the reference signal. The OFDM receiver according to claim 1, characterized in that. 3. The OFDM receiving apparatus according to claim 1, wherein the adjustable reference signal generating means comprises a plurality of digital synthesizers for generating reference signals which are individually phase-shifted by supplying phase data. 4. The phase shift amount control means includes a power detector of a demodulated signal of the OFDM demodulator and a power dispersion detector of a demodulated signal of the OFDM demodulator. Item 2. The OFDM signal receiving device according to Item 1. 5. A second frequency mixer and a second frequency mixer for converting the frequency of the added intermediate frequency signal into a second intermediate frequency signal between the adder and the analog-digital converter. 5. A second local oscillator for supplying a local oscillation signal and a second intermediate frequency circuit for selecting a second intermediate frequency signal from an output frequency mixed signal of the second frequency mixer are provided. OFDM according to any one
Signal receiving device.