JP2010004145A - Wireless receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless receiver for simultaneously receiving signals in a plurality of frequency bands with a simple structure. <P>SOLUTION: The wireless receiver includes: an antenna part for receiving a high frequency radio signal; a reference signal generating means for generating first and second reference signals; first and second down converters for using the first and second reference signals to convert signals received by the antenna part into baseband signals; a first filter for selecting a prescribed frequency band from output of the first down converter; a first demodulation means for performing AM demodulation or FM demodulation to the signal selected by the first filter; a second filter for selecting from an output of the second down converter a prescribed frequency band; and a second demodulation means for performing AM demodulation or FM demodulation to the signal selected by the second filter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless reception device, and more particularly to a wireless reception device capable of demodulating a plurality of channels simultaneously.

In terrestrial digital broadcasting, an OFDM (Orthogonal Frequency Division Multiplex) system is employed. The OFDM scheme is a multi-carrier modulation scheme, and is a scheme for transmitting a signal in which digital modulated waves having a large number of orthogonal carrier frequencies are multiplexed.

  A configuration of a conventional OFDM receiver will be described with reference to FIG. The received signal received by the antenna 101 is amplified by the amplifier circuit 102 and then given to the multipliers 105 and 106, respectively. The multiplier 105 is supplied with a reference signal having substantially the same frequency as the received signal from the local oscillator 103. Multiplier 105 multiplies the received signal and the reference signal to generate a baseband signal. On the other hand, a signal obtained by shifting the phase of the reference signal from the local oscillator 103 is supplied to the multiplier 106 by the phase converter 104, and the multiplier uses this to generate a baseband signal from the received signal. Outputs from the multipliers 105 and 106 are amplified by amplifier circuits 107 and 108, and low-frequency components are extracted by low-pass filters 109 and 110. Then, after converting into a digital signal by the analog / digital converters 111 and 112, the OFDM demodulator 113 performs demodulation processing such as FFT processing.

  Although the configuration of the OFDM receiver has been described, when receiving signals of the AM modulation scheme or the FM modulation scheme, frequency conversion circuits or the like are required for the number of modulation schemes to be demodulated. Therefore, in Patent Document 1, in the configuration of FIG. 3, the frequency band of the local oscillator 103 is widened, and the arithmetic processing of the demodulator 113 can be changed according to the modulation method. Is also disclosed.

Incidentally, in addition to a request for receiving a plurality of modulation schemes with one receiver, there is also a request for simultaneously receiving a plurality of radio signals (modulation schemes may be the same or different). For example, VICS that broadcasts traffic information transmits information by FM multiplex broadcasting. Since VICS is multiplexed on a specific FM channel, in order to receive other FM broadcasts and AM broadcasts when receiving VICS, it is necessary to be able to receive a plurality of channels simultaneously.
JP-A-9-74366

  However, in the case of the conventional technique such as Patent Document 1, although signals of a plurality of modulation schemes can be demodulated, a plurality of signals cannot be demodulated simultaneously. Therefore, in order to receive a plurality of broadcasts, it is necessary to use a plurality of receivers, which is disadvantageous in terms of cost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radio receiving apparatus capable of simultaneously receiving signals of a plurality of frequency bands with a simple configuration.

  In order to achieve the above object, in the present invention, a radio signal is demodulated by the following means or processing.

  The present invention includes an antenna unit that receives a radio signal, a reference signal generation unit that generates two reference signals, and two down-converts a baseband signal by applying each reference signal to the signal received by the antenna unit. Has a converter. Each downconverter includes a filter that selects a predetermined frequency band from the output of the downconverter, and a demodulating unit that performs AM demodulation or FM demodulation on a signal selected by the filter.

  In this way, it is possible to simultaneously demodulate radio signals in any two frequency bands among radio signals of FM modulation scheme and AM modulation scheme.

  In the present invention, it is preferable that the two reference signals generated by the reference signal generating means have the same frequency and are different in phase by π / 2. Such a down-converter using two reference signals has the same configuration as that of a conventional OFDM receiver, and can use conventional components, so that the radio receiver according to the present invention can be easily manufactured. .

  In addition, the present invention preferably further includes demodulation means for performing OFDM demodulation from the outputs of the two down converters. Here, a switch means for switching whether the output from the down converter is output to the two demodulation means for performing AM and FM demodulation or to the demodulation means for performing OFDM demodulation may be further provided. Further, a configuration may be adopted in which the output from the down converter is received by a plurality of demodulation means without providing the switching means.

  In this way, it is possible to perform two-channel simultaneous reception of AM and / or FM broadcast and reception of OFDM broadcast with one wireless reception device.

  The reference signal generating means in the present invention is also preferably configured as two local oscillators whose frequencies can be adjusted independently. This is because, when receiving two frequency bands at the same time, the received signal is frequency-converted in accordance with the frequency, so that subsequent filtering processing and the like are facilitated.

  Note that the present invention can be understood as a wireless reception apparatus having at least a part of the above means. The present invention can also be understood as a wireless reception method including at least a part of the above processing. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  According to the present invention, it is possible to simultaneously receive signals of a plurality of frequency bands with a simple configuration.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
FIG. 1 shows the configuration of the wireless receiver according to the first embodiment. This receiver can receive three broadcasts of AM broadcast, FM broadcast, and terrestrial digital broadcast (OFDM broadcast), and can receive two channels of AM broadcast and FM broadcast simultaneously. This receiver requires two signals of I signal and Q signal in OFDM demodulation, but can be demodulated using only one of I signal and Q signal in AM demodulation and FM demodulation. The two channels are received simultaneously by demodulating the I signal and the Q signal individually. The simultaneous reception of two channels includes AM and AM, and simultaneous reception of FM and FM in addition to AM and FM.

  As shown in FIG. 1, the received signal received by the antenna 1 is amplified by the amplifier circuit 2 and then given to the multipliers 5 and 6, respectively. The multipliers 5 and 6 are supplied with reference signals of the same frequency from the local oscillator 3, but the phases of these reference signals are shifted by π / 2 by the phase converter 4. The multipliers 5 and 6 frequency-convert the received signal using the reference signal, amplify it by the amplifier circuits 7 and 8, and then extract the low frequency components by the low-pass filters 9 and 10, thereby reducing the received signal to the baseband signal. Converted.

  The output destination of the down-converted baseband signal is switched by the switch circuit 18. One is to output two baseband signals to different AM / FM demodulators 13 and 14, respectively. The other is to output two baseband signals to one OFDM demodulator 17.

  In the case of AM / FM demodulation, first, only the frequency band demodulated by the bandpass filters 11 and 12 is transmitted and demodulated by the AM / FM demodulators 13 and 14. Note that AM demodulation and FM demodulation may be switched by switching processing (program) performed by the demodulator.

  On the other hand, in the case of OFDM demodulation, the baseband signal is converted to a digital signal by the analog / digital converters 15 and 16, and then the OFDM demodulator 17 performs demodulation processing such as FFT processing.

  The local oscillator 3 switches the frequency of the reference signal generated in accordance with the broadcast to be received. For example, when receiving terrestrial digital broadcasting, a reference signal having a frequency matched to the channel to be received may be generated. When two channels of AM / FM are received simultaneously, a reference signal frequency of about 530 kHz is used, and signals corresponding to AM to FM (531 kHz to 90 or 108 MHz) are transmitted through the low-pass filters 9 and 10, and the band Only broadcast signals desired to be received by the pass filters 11 and 12 are output to the demodulator. However, when a wide band is received at the same time, the design of an amplifier, a filter, and the like can be complicated, so the frequency band that can be received simultaneously may be a part of AM to FM.

  According to the radio receiver according to the present embodiment, AM and FM broadcast can be simultaneously received by two channels with almost no increase in cost compared to the configuration of the conventional OFDM receiver.

(Second Embodiment)
FIG. 2 shows the configuration of the wireless receiver according to the second embodiment. In the present embodiment, reference signals are supplied to multipliers 5 and 6 from two local oscillators 21 and 22 whose frequencies can be individually set. When two AM / FM channels are received simultaneously, the local oscillators 21 and 22 generate reference signals having frequencies matching the channels demodulated by the two AM / FM demodulators 13 and 14. In this way, since only the baseband signal of the channel desired to be received can be extracted by the low-pass filters 9 and 10, no bandpass filter is required. In addition, in the first embodiment, since the wideband received signal is down-converted, the configuration of the amplifier, the filter, and the like may be complicated. It will be easy.

  When receiving digital terrestrial broadcasts, the reference signals generated by the local oscillators 21 and 22 are assumed to have the same frequency and the phase is shifted by π / 2, or the multiplier 6 as in the first embodiment. The reference signal generated by the local oscillator 21 may be shifted by π / 2 by the phase converter.

  According to the present embodiment, when two channels are received at the same time, even if the frequency bands are greatly different, such as AM broadcasting and FM broadcasting, it can be easily received.

(Other)
In the above embodiment, a radio receiver capable of switching between reception of terrestrial digital broadcasting and simultaneous reception of two channels of AM / FM has been described, but the reception function of terrestrial digital broadcasting is omitted and AM / FM is omitted. Only the two-channel simultaneous reception function may be provided.

  In the above description, the switch circuit 18 is provided, and the output destination of the baseband signal is switched between the AM / FM demodulators 13 and 14 and the OFDM demodulator 17. The baseband signal may be always input to all the demodulators without providing 18. This is because the signal-to-noise ratio of the signal is determined by the RF stage, and there is no problem even if baseband signals are input to a plurality of demodulators.

  In the above description, the direct conversion method is described as an example, but a method using an intermediate frequency such as a superheterodyne method may be adopted.

  In the above description, the configuration is described in which the received signal is processed as an analog signal. However, the received signal may be converted into a digital signal, and processing such as frequency conversion may be performed on the digital signal.

FIG. 1 is a diagram illustrating a configuration of a wireless receiver according to the first embodiment. FIG. 2 is a diagram illustrating a configuration of a wireless receiver according to the second embodiment. FIG. 3 is a diagram illustrating a configuration of a conventional OFDM receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 3 Local oscillator 4 Phase converter 5,6 Multiplier 13,14 AM / FM demodulator 17 OFDM demodulator 18 Switch circuit 21,22 Local oscillator

Claims (5)

An antenna unit for receiving radio signals;
Reference signal generating means for generating first and second reference signals;
First and second down-converters for frequency-converting signals received by the antenna unit into baseband signals using the first and second reference signals, respectively;
A first filter for selecting a predetermined frequency band from the output of the first down converter, and a first demodulating means for AM-demodulating or FM-demodulating a signal selected by the first filter;
A second filter for selecting a predetermined frequency band from the output of the second down-converter, and a second demodulating means for AM-demodulating or FM-demodulating a signal selected by the second filter;
A wireless receiver comprising: The radio reception apparatus according to claim 1, wherein the first and second reference signals are signals having the same frequency and having phases different by π / 2. The radio reception apparatus according to claim 2, further comprising third demodulation means for performing OFDM demodulation from outputs of the first and second down converters. 4. The radio according to claim 3, further comprising switch means for switching outputs of the first and second down converters between the first and second demodulation means and a third demodulation means. Receiver device. The radio reception apparatus according to claim 1, wherein the reference signal generation unit includes two local oscillators capable of adjusting a frequency.

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