JPH11355163A - Digital/analog shared audio broadcasting reception equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide audio broadcasting reception equipment with which both digital audio broadcasting and FM broadcasting can be received in simple circuit configuration and miniaturized design is enabled. SOLUTION: In spite of whether a received broadcasting signal is a Band II signal (a) of digital audio broadcasting(DAB) or FM Band signal (b), this broadcasting signal is converted to a first intermediate frequency(IF) signal (c) of DAB by a down converter 3 for DAB (Band II). Next, when the broadcasting signal is the Band signal (a) of DAB, the first IF signal (c) is mixed with a local oscillation frequency signal d1 from a local oscillation PLL circuit 4 by a mixer 5, converted to a second IF signal (f) and passed through a low-pass filter 7 for DAB. When the broadcasting signal is the FM Band signal (b), the first IF signal (c) is mixed with a local oscillation frequency signal d2 outputted from the local oscillation PLL circuit 4 by the mixer 5, converted to an IF signal (e) for FM broadcasting and passed through an IF filter 6 for FM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio broadcast receiving apparatus, and more particularly to a digital / analog common audio broadcast receiving apparatus capable of receiving both a digital audio broadcast signal and an FM broadcast signal.

[0002]

2. Description of the Related Art In recent years, digital audio broadcasting DAB (Digital Audio Broadcasting) for broadcasting digital audio signals using terrestrial waves or satellites.
Audio Broadcasting) is under development. It encodes audio signals with high efficiency (data compression) and OFD
This is intended to be modulated by M (Orthogonal Frequency Division Multiplexing) and broadcast.

[0003] ETSI (EUROPEAN TELECOMMUNICATION ST
DAB standard (ETS 300 401 S) by ANDARDS INSTITUTE
eptember 1994: “Radio broadcast systems; Digital Au
dioBroadcasting (DAB) to mobile, portable and fixed
According to the receivers "), there are three transmission modes (mode I, mode II, and mode III) in the transmission scheme of the DAB signal.
Among them, mode I suitable for signal transmission by terrestrial broadcasting is BandI (47 MHz to 68 MHz).
z), Band II (80.5 MHz to 108 MHz),
DAB broadcasting is possible in the Band III (174 MHz to 240 MHz) RF band.

On the other hand, the current FM broadcast is FM Band
(88 MHz to 108 MHz), and this band is almost the same as the Band II band of DAB. Looking at the current state of each country regarding DAB,
Although there is no plan to broadcast DAB in the II (80.5 MHz to 108 MHz) band, considering the recent trend of digitization of terrestrial broadcasting and satellite broadcasting, this FM Ban will be used in the future.
There is a high possibility that the d band will be allocated to Band II of DAB. In this case, existing FM broadcasting and DAB (Band II) are mixed in the band of 80.5 MHz to 108 MHz.

FIG. 4 shows a configuration of a conventional digital / analog shared audio broadcast receiving apparatus 51 capable of receiving both DAB and FM broadcasts. All received broadcast signals are converted to intermediate frequency signals by the superheterodyne method regardless of the selected channel. The first intermediate frequency of DAB is 38.912 MHz, and the second intermediate frequency is 2.048.
MHz (or 3.072 MHz), and the intermediate frequency of FM broadcast is 10.7 MHz. For this reason, DAB
BandII signal p and FM Band signal q
In order to receive both the input tuning circuit and the local oscillation circuit, it is necessary to provide separate circuits for DAB reception and FM broadcast reception as shown in FIG.

First, B of DAB received by antenna 52
R of the band of the andII signal p and the FM Band signal q
The F signal is sent to an FM down converter 54 or a DAB (Band II) down converter 55 by an input changeover switch 53. Downconverter for FM 5
In 4, the RF signal of the selected FM channel is set to 10.7.
It is converted to an intermediate frequency signal r of MHz. The converted signal passes through the FM IF filter 58 and is input to a subsequent FM demodulation circuit (not shown).

On the other hand, in the DAB (Band II) down converter 55, the RF signal of the selected DAB channel is first converted to a first intermediate frequency of 38.912 MHz, and the band is limited by a band pass filter. Next, DA
The first intermediate frequency signal s output from the Band II receiving downconverter of B and the local oscillation frequency signal t oscillated by the local oscillator 56 are mixed by the mixer 57 to produce 2.048 MHz (or 3.072 MHz). The signal is converted to a second intermediate frequency signal u.

The converted signal passes through a DAB low-pass filter 59 and is input to a subsequent DAB signal demodulation circuit (not shown). As described above, in the conventional digital / analog shared audio broadcast receiving apparatus 51, the digital audio broadcast signal and the FM broadcast signal are received and received by the respective dedicated receiving circuits.
Demodulated.

[0009]

However, the above-mentioned conventional digital / analog shared audio broadcast receiving apparatus 51 described above.
Then, as shown in FIG. 4, the FM Band for FM broadcasting is used.
When receiving both the signal p and the Band II signal q for DAB, the FM down-converter 54 and the DAB
(Band II) separate converter 55 is required. Therefore, the digital / analog shared audio broadcast receiving apparatus 51 has a problem that the number of parts is increased, miniaturization is difficult, and manufacturing cost is increased. In particular, the FM down-converter 54 shown in FIG.
In the input tuning circuit and the local oscillation circuit section in the down converter 55 for the ndII), an air-core coil and a variable coil that need to be adjusted are used, respectively, and this leads to an increase in the number of adjustment components and a major factor in cost increase. It has become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to receive both digital audio broadcasts and FM broadcasts with a simple circuit configuration and to achieve a compact design. Another object of the present invention is to provide a digital / analog shared audio broadcast receiving apparatus.

[0011]

According to a first aspect of the present invention, there is provided a digital / analog dual-use audio broadcast receiving apparatus, comprising: a digital audio broadcast signal obtained by digitally modulating an audio signal; Digital broadcasting that can receive both broadcasting signals
In the analog audio broadcast receiving apparatus, the broadcast signal is converted into a first intermediate frequency signal for digital audio broadcast and output, regardless of whether the broadcast signal is the digital audio broadcast signal or the FM broadcast signal. A first frequency converting means, and converting the first intermediate frequency signal output by the first frequency converting means to a second intermediate frequency signal for digital audio broadcasting when the broadcast signal is the digital audio broadcasting signal. And a second frequency converting means for converting the broadcast signal into an FM broadcast intermediate frequency signal and outputting the converted signal when the broadcast signal is the FM broadcast signal.

[0012] According to the invention, the digital / analog shared audio broadcast receiving apparatus receives a broadcast signal, regardless of whether the broadcast signal is a digital audio broadcast signal or an FM broadcast signal. First, the broadcast signal is converted into a first intermediate frequency signal for digital audio broadcasting by first frequency conversion means such as a signal down converter. That is, the digital audio broadcast signal is converted into the first intermediate frequency signal as in the related art, but the FM broadcast signal is not directly converted into the FM intermediate frequency signal, but is once converted into the first intermediate frequency signal.

Next, the first intermediate frequency signal output by the first frequency conversion means is input to the second frequency conversion means. When the received broadcast signal is a digital audio broadcast signal, the second frequency conversion means such as a frequency conversion circuit including a mixer converts the first intermediate frequency signal into a second intermediate frequency signal for digital audio broadcast and outputs the converted signal. I do. On the other hand, when the received broadcast signal is an FM broadcast signal, the second frequency conversion means converts the first intermediate frequency signal into an FM broadcast signal.
The signal is converted to a broadcast intermediate frequency signal and output.

As described above, only by adding a means for converting the broadcast signal converted to the first intermediate frequency signal into a different intermediate frequency signal between the time of receiving the digital audio broadcast signal and the time of receiving the FM broadcast signal, the digital audio broadcast Both signals and FM broadcast signals can be received. Therefore, according to the digital / analog shared audio broadcast receiving apparatus of the present invention, it is not necessary to branch the circuit for generating the intermediate frequency signal between the digital audio broadcast signal and the FM broadcast signal, thereby reducing the number of parts and reducing the size.・ Low manufacturing costs can be achieved.

According to a second aspect of the present invention, there is provided a digital / analog dual-use audio broadcast receiving apparatus.
2. The digital / analog shared audio broadcast receiving apparatus according to claim 1, wherein said second frequency conversion means converts the first intermediate frequency signal when converting the second intermediate frequency signal and when converting the FM intermediate frequency signal. And a local oscillation circuit for outputting an oscillation frequency signal having a frequency corresponding to the second intermediate frequency signal or the FM broadcast by mixing the first intermediate frequency signal with the oscillation frequency signal output from the local local oscillation circuit. And a mixer for converting the signal into an intermediate frequency signal for use in output.

According to the above-mentioned invention, the local oscillation circuit is suitable for two cases, that is, the case where the first intermediate frequency signal is converted into the second intermediate frequency signal and the case where the first intermediate frequency signal is converted into the FM broadcast intermediate frequency signal. Output an oscillating frequency signal of a suitable frequency. The oscillation frequency signal output by the local oscillation circuit is input to the mixer and mixed with the first intermediate frequency signal.

When an oscillation frequency signal for converting the second intermediate frequency signal is output from the local oscillation circuit and mixed, the mixer converts the first intermediate frequency signal into a second intermediate frequency signal and outputs the same. When the oscillation frequency signal for converting the FM broadcast intermediate frequency signal is output from the oscillation circuit and mixed, the mixer converts the first intermediate frequency signal into an FM broadcast intermediate frequency signal and outputs the converted signal.

As described above, since the second frequency conversion means has a simple circuit configuration including the local oscillation circuit and the mixer, the second intermediate frequency signal and the F signal can be easily and at low cost.
An M broadcast intermediate frequency signal can be generated.

According to a third aspect of the present invention, there is provided a digital / analog dual-use audio broadcast receiving apparatus.
3. The digital / analog shared audio broadcast receiving apparatus according to claim 2, wherein the local oscillation circuit is a local oscillation PLL circuit.

According to the above invention, a local oscillation PLL circuit is applied to the local oscillation circuit described in claim 2. Therefore, it is possible to provide a local oscillation circuit having a simple configuration in which the oscillation frequency can be easily controlled.

According to a fourth aspect of the present invention, there is provided a digital / analog dual-use audio broadcast receiving apparatus.
3. The digital / analog shared audio broadcast receiving apparatus according to claim 2, wherein the local oscillation circuit is a crystal oscillation circuit.

According to the above invention, the crystal oscillation circuit is applied to the local oscillation circuit described in claim 2. Therefore,
A local oscillation circuit having an accurate oscillation frequency and a simple configuration can be provided.

According to a fifth aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus for solving the above problems.
5. The digital / analog shared audio broadcast receiving apparatus according to claim 1, wherein said second intermediate frequency signal is band-limited, and a resultant digital audio broadcast band-limited signal is output. A filter circuit, and band-limiting the intermediate frequency signal for FM broadcasting,
F that outputs the resulting FM broadcast band limited signal
An M broadcast filter circuit is further provided.

According to the above invention, the second intermediate frequency signal output by the second frequency conversion means is input to a digital audio broadcast filter circuit such as a digital audio broadcast low-pass filter, and then subjected to demodulation processing. Therefore, the band is limited to the band-limited signal for digital audio broadcasting. Also, the second
The FM broadcast intermediate frequency signal output by the frequency conversion means is input to an FM broadcast filter circuit such as an FM IF filter, and band-limited to an FM broadcast band-limited signal for later demodulation processing. That is, a circuit downstream of the second frequency conversion means is branched into a circuit for processing a digital audio broadcast signal and a circuit for processing an FM broadcast signal, and demodulates each signal individually.

As described above, since the filter circuits for the digital audio broadcast signal and the FM broadcast signal are provided, it is possible to extract a signal in a frequency band suitable for demodulating each signal.

According to a sixth aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus for solving the above problems.
The digital / analog shared audio broadcast receiving apparatus according to claim 5, wherein a digital audio signal demodulation circuit demodulates the audio signal from the digital audio broadcast band-limited signal output from the digital audio broadcast filter circuit,
An FM demodulation circuit for demodulating the audio signal from the FM broadcast band limited signal output from the FM broadcast filter circuit.

According to the above invention, the digital audio broadcast band-limited signal output from the digital audio broadcast filter circuit is input to the digital audio signal demodulation circuit and demodulated into the original audio signal. The FM broadcast band-limited signal output by the FM broadcast filter circuit is input to the FM demodulation circuit and demodulated into the original audio signal.

Thus, the original audio signal is added to the digital / analog common audio broadcast receiving apparatus according to the fifth aspect of the present invention by adding a dedicated demodulation circuit to each of the digital audio broadcast signal and the FM broadcast signal. Can be played.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital / analog shared audio broadcast receiving apparatus according to the present invention will be described below with reference to FIGS.

FIG. 1 shows a block diagram of a digital / analog shared audio broadcast receiving apparatus 1 according to the present embodiment. The digital / analog shared audio broadcast receiving apparatus 1 is a DAB Ba.
ndII signal a and FM band signal b of FM broadcasting can be received, and antenna 2, DAB (Band
II) down-converter 3, local oscillation PLL circuit 4, mixer 5, FM IF filter 6, and DAB low-pass filter 7.

The antenna 2 includes a Band II signal a of DAB as a digital audio broadcast signal transmitted by digitally modulating the audio signal at the broadcast station, and an FM broadcast transmitted by modulating the audio signal at the broadcast station. FM as a signal
And a Band signal b. The DAB (Band II) down converter 3 as the first frequency conversion means converts a broadcast signal obtained as a result of selecting a desired channel from the Band II signal a or the FM Band signal b of the DAB into a first intermediate frequency signal c of the DAB. And output.

The local oscillation PLL circuit (local oscillation circuit) 4 and the mixer 5 constitute second frequency conversion means. The local oscillation PLL circuit 4 can output a local oscillation frequency signal (oscillation frequency signal) d having a desired frequency by a control unit (not shown). Local oscillation PL
By using the L circuit 4, it is possible to provide a local oscillation circuit having a simple configuration in which the oscillation frequency can be easily controlled.

The mixer 5 outputs the first intermediate frequency signal c output from the DAB (Band II) down converter 3.
And the local oscillation frequency signal d output from the local oscillation PLL circuit 4 to convert the first intermediate frequency signal c into an intermediate frequency signal having a frequency corresponding to the frequency of the local oscillation frequency signal d, and output the converted signal. .

When the intermediate frequency signal output from the mixer 5 is the FM broadcast intermediate frequency signal e, the FM IF filter 6 limits the band of the FM broadcast intermediate frequency signal e and performs necessary demodulation processing. And outputs an FM broadcast band-limited signal g of a suitable frequency band. The DAB low-pass filter 7 converts the intermediate frequency signal output from the mixer 5 into a DA signal.
When the signal is the second intermediate frequency signal f of B (Band II), the second intermediate frequency signal f is band-limited, and a digital audio broadcasting band-limited signal h of a frequency band necessary for the subsequent demodulation processing is output.

Next, a procedure of processing a broadcast signal by the digital / analog shared audio broadcast receiving apparatus 1 having the above configuration will be described.

First, B of DAB received by antenna 2
andII signal a and FM band signal b of FM broadcast
Thus, the DAB (Band II) down converter 3 selects a desired channel for DAB or FM broadcasting. Then, the Band II signal a or the FM Band signal b of the DAB corresponding to the selected channel is the first intermediate frequency 3 of the DAB by the DAB (Band II) down converter 3 regardless of the type of the broadcast signal.
The signal is converted to a first intermediate frequency signal c of 8.912 MHz.

Next, when the broadcast signal corresponding to the received / selected channel is DAB BandIIa,
The oscillation frequency of the local oscillation PLL circuit 4 is 40.96 MHz
Or 36.864 MHz (or 41.984M
Hz or 35.84 MHz).
The local oscillation frequency signal d ₁ output under the frequency control as described above and the 38.912 MHz first intermediate frequency signal c output from the DAB (Band II) down converter 3 are input to the mixer 5.

The mixer 5 mixes the first intermediate frequency signal c with the local oscillation frequency signal d ₁ and adjusts the frequency to 2.048.
MHz (or 3.072 MHz) DAB (Ban
dII) and outputs it. The second intermediate frequency signal f output from the mixer 5 is DAB
, And is band-limited and output as a digital audio broadcast band-limited signal h.

On the other hand, when the broadcast signal corresponding to the received / selected channel is the FM Band signal b,
The oscillation frequency of local oscillation PLL circuit 4 is 49.612 MH
z (or 28.212 MHz). The local oscillation frequency signal d ₂ output under the frequency control as described above and the local oscillation frequency signal d ₂ output from the down converter 3
The first intermediate frequency signal c of 8.912 MHz is input to the mixer 5.

The mixer 5 mixes the first intermediate frequency signal c with the local oscillation frequency signal d ₂ and adjusts the frequency to 10.7M.
And converts it into an FM broadcast intermediate frequency signal e. The FM broadcast intermediate frequency signal e output from the mixer 5 is input to the FM IF filter 6, band-limited, and output as an FM broadcast band-limited signal g.

Although the local oscillation PLL circuit 4 is used as the local oscillation circuit of the digital / analog shared audio broadcast receiving apparatus 1, the digital / analog shared audio broadcast receiving apparatus shown in FIG. A crystal oscillation circuit such as 21 can also be used.

The crystal oscillation circuit includes crystal oscillators 8 and 9 and an output switching circuit 10. The crystal oscillator 8 has a frequency of 40.96 MHz or 36.864 MHz.
(Or 41.984 MHz or 35.84 MH
z) and outputs the oscillation frequency signal i ₁ , and the crystal oscillator 9 has a frequency of 49.612 MHz (or 28.212 MHz).
outputs an oscillation signal i ₂ in z).

By using the crystal oscillators 8 and 9 for the local oscillation circuit, not only can the oscillation frequency be stabilized and accurate, but also because the oscillation frequency is specific to the crystal oscillators 8 and 9, No mechanism is required and the configuration is simplified.
The output switching circuit 10 selectively inputs _one of the oscillation frequency signals i ₁ and i ₂ output from the crystal oscillators 8 and 9 to the mixer 5.

In the above configuration, the received signal is DA
In the case of the Band II signal a of B, the output switching circuit 10 operates to connect the crystal oscillator 8 to the mixer 5, and as a result, 40.96 MH inputted to the mixer 5
z or 36.864 MHz (or 41.984
Oscillation frequency signal in the MHz or 35.84MHz) i ₁
Is mixed with the first intermediate frequency signal c by the mixer 5.
As a result, the first intermediate frequency signal c is converted into a second intermediate frequency signal f.

Also, if the received broadcast signal is FM Band
In the case of the signal b, the output switching circuit 10 operates to connect the crystal oscillator 9 to the mixer 5, and as a result, the oscillation frequency signal i _{2 of} 49.612 MHz (or 28.212 MHz) input to the mixer 5. Is mixed with the first intermediate frequency signal c by the mixer 5. As a result,
The first intermediate frequency signal c is converted into an FM broadcast intermediate frequency signal e.

Further, an FM demodulation circuit 11 is provided after the FM IF filter 6 shown in FIG. 1 or 2, and a DAB signal demodulation circuit 12 is provided after the low-pass filter 7 for DAB as a digital audio signal demodulation circuit. Can also.

FIG. 3 shows a digital / analog shared audio broadcast receiving apparatus 31 in which these demodulation circuits are added to the digital / analog shared audio broadcast receiving apparatus 1 of FIG. The FM demodulation circuit 11 outputs the FM output from the FM IF filter 6.
While the broadcast band limited signal g is demodulated into the original audio signal j, the DAB signal demodulation circuit 12 converts the digital audio broadcast band limited signal h output from the DAB low-pass filter 7 into the original audio signal k. Demodulate. As a result, it becomes possible to reproduce the original sound on the broadcast station side.

As described above, the DAB Band II signal a
And the FM Band signal b, these broadcast signals are temporarily converted to the first intermediate frequency signal c of DAB (Band II).
And further converts the first intermediate frequency signal c into
Only by converting to a different intermediate frequency signal when receiving DAB Band II signal a and when receiving FM Band signal b,
Both the DAB Band II signal a and the FM Band signal b can be received.

Therefore, according to the digital / analog shared audio broadcast receiving apparatus 1, 21, 31 of the present embodiment, the circuit for generating the intermediate frequency signal is provided with the DAB Band II signal a.
And the FM Band signal b, there is no need to branch, and the number of parts can be reduced, the size can be reduced, and the manufacturing cost can be reduced.

[0050]

As described above, the digital / analog shared audio broadcast receiving apparatus according to the first aspect of the present invention provides both a digital audio broadcast signal obtained by digitally modulating an audio signal and an FM broadcast signal obtained by frequency-modulating an audio signal. A digital / analog shared audio broadcast receiving apparatus capable of receiving a broadcast signal of the type described above, regardless of whether the broadcast signal is the digital audio broadcast signal or the FM broadcast signal, A first frequency converting means for converting the first intermediate frequency signal into a first intermediate frequency signal and outputting the first intermediate frequency signal,
When the broadcast signal is the digital audio broadcast signal, it is converted into a second intermediate frequency signal for digital audio broadcast and output, while when the broadcast signal is the FM broadcast signal, it is converted into an FM broadcast intermediate frequency signal. And a second frequency conversion means for outputting the output.

Therefore, a digital audio broadcast signal can be obtained simply by adding means for converting the broadcast signal converted into the first intermediate frequency signal into an intermediate frequency signal different between when the digital audio broadcast signal is received and when the FM broadcast signal is received. And FM broadcast signals. Therefore, according to the digital / analog shared audio broadcast receiving apparatus of the present invention, the circuit for generating the intermediate frequency signal is used for the digital audio broadcast signal.
There is no need to branch to the M broadcast signal, and the number of parts can be reduced, the size can be reduced, and the manufacturing cost can be reduced.

As described above, in the digital / analog shared audio broadcast receiving apparatus according to the second aspect of the present invention, in the digital / analog shared audio broadcast receiving apparatus according to the first aspect, the second frequency conversion means may include: A local oscillation circuit for outputting an oscillation frequency signal having a frequency corresponding to each of the conversion of the first intermediate frequency signal to the second intermediate frequency signal and the conversion of the first intermediate frequency signal to the FM broadcast intermediate frequency signal; A mixer that mixes the oscillation frequency signal output from the oscillation circuit with the second intermediate frequency signal or the FM broadcast intermediate frequency signal and outputs the second intermediate frequency signal or the FM broadcast intermediate frequency signal.

Therefore, the second frequency conversion means has a simple circuit configuration of a local oscillation circuit and a mixer, so that the second intermediate frequency signal and the F signal can be easily and inexpensively manufactured.
There is an effect that an intermediate frequency signal for M broadcast can be generated.

According to a third aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus according to the second aspect, wherein the local oscillation circuit is a local oscillation PLL circuit. The configuration is as follows.

Therefore, there is an effect that the local oscillation circuit can be easily and simply controlled in oscillation frequency.

According to a fourth aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus according to the second aspect, wherein the local oscillation circuit is a crystal oscillation circuit. There is a certain configuration.

Therefore, there is an effect that a local oscillation circuit having a simple configuration with an accurate oscillation frequency can be obtained.

According to a fifth aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus as set forth in any one of the first to fourth aspects. A digital audio broadcast filter circuit for band limiting a frequency signal and outputting a resulting digital audio broadcast band limited signal, and a band limit for the FM broadcast intermediate frequency signal and a resulting FM broadcast band limit And a FM broadcast filter circuit for outputting a signal.

Therefore, a filter circuit for digital audio broadcast signals and a filter circuit for FM broadcast signals are provided, respectively.
There is an effect that a signal in a frequency band suitable for demodulating each signal can be extracted.

According to a sixth aspect of the present invention, there is provided a digital / analog shared audio broadcast receiving apparatus according to the fifth aspect, wherein the digital / analog shared audio broadcast receiving apparatus outputs the digital audio / analog signal from the digital audio filter circuit. A digital audio signal demodulation circuit for demodulating the audio signal from the digital audio broadcast band limited signal, and an FM demodulation circuit for demodulating the audio signal from the FM broadcast band limited signal output from the FM broadcast filter circuit. And a configuration further comprising:

Therefore, the original audio signal is reproduced by adding a dedicated demodulation circuit to each of the digital audio broadcast signal and the FM broadcast signal to the digital / analog common audio broadcast receiving apparatus according to the fifth aspect of the present invention. It has the effect that it can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital / analog shared audio broadcast receiving apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing another configuration of the digital / analog shared audio broadcast receiving apparatus according to the embodiment of the present invention.

FIG. 3 is a block diagram showing still another configuration of the digital / analog shared audio broadcast receiving apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional digital / analog shared audio broadcast receiving apparatus.

[Explanation of symbols]

1 Digital / analog shared audio broadcast receiving device 3 Downconverter for DAB (Band II)
Frequency conversion means) 4 local oscillation PLL circuit (second frequency conversion means, local oscillation circuit) 5 mixer (second frequency conversion means) 6 IF filter for FM (filter circuit for FM broadcast) 7 low-pass filter for DAB (digital) 8 Audio oscillator (second frequency conversion means, local oscillation circuit) 9 Crystal oscillator (second frequency conversion means, local oscillation circuit) 10 Output switching circuit (second frequency conversion means, local oscillation circuit) 11 FM demodulation circuit 12 DAB signal demodulation circuit (digital audio signal demodulation circuit) 21 digital / analog shared audio broadcast receiver 31 digital / analog shared audio broadcast receiver a Band II signal of DAB (digital audio broadcast signal) b FM Band signal (FM) broadcast signal) c first intermediate frequency signal d local oscillation frequency signal d ₁ local oscillator Wavenumber signal d ₂ local oscillation frequency signal e FM broadcast intermediate frequency signal f second intermediate frequency signal g FM broadcast band limited signal h digital audio broadcast band-limited signals i ₁ oscillation signal i ₂ oscillation frequency signal j audio signal k Audio signal

Claims (6)

[Claims] 1. A digital / analog shared audio broadcast receiving apparatus capable of receiving both a digital audio broadcast signal obtained by digitally modulating an audio signal and an FM broadcast signal obtained by frequency-modulating an audio signal. Irrespective of whether the signal is the digital audio broadcast signal or the FM broadcast signal, first frequency conversion means for converting the broadcast signal into a first intermediate frequency signal for digital audio broadcast and outputting the first intermediate frequency signal; The first intermediate frequency signal output by the frequency conversion means is converted to a second intermediate frequency signal for digital audio broadcasting when the broadcast signal is the digital audio broadcast signal, and is output. When it is an FM broadcast signal, F
A digital / analog shared audio broadcast receiving apparatus, comprising: a second frequency converting means for converting the signal into an M broadcast intermediate frequency signal and outputting the converted signal. 2. The second frequency converter outputs an oscillation frequency signal having a frequency corresponding to each of the first intermediate frequency signal when the second intermediate frequency signal is converted and the FM intermediate frequency signal when the first intermediate frequency signal is converted. A local oscillation circuit, and a mixer that mixes the first intermediate frequency signal with the oscillation frequency signal output from the local oscillation circuit, converts the mixed signal into the second intermediate frequency signal or the FM broadcast intermediate frequency signal, and outputs the converted signal. 2. The digital / analog shared audio broadcast receiving apparatus according to claim 1, comprising: 3. The digital / analog shared audio broadcast receiving apparatus according to claim 2, wherein said local oscillation circuit is a local oscillation PLL circuit. 4. The digital / analog shared audio broadcast receiving apparatus according to claim 2, wherein said local oscillation circuit is a crystal oscillation circuit. 5. A digital audio broadcast filter circuit for band-limiting said second intermediate frequency signal and outputting a digital audio broadcast band-limited signal obtained as a result thereof; and band-limiting the FM broadcast intermediate frequency signal. The resulting FM
5. The digital / analog shared audio broadcast receiving apparatus according to claim 1, further comprising an FM broadcast filter circuit for outputting a broadcast band limited signal. 6. A digital audio signal demodulation circuit for demodulating the audio signal from the digital audio broadcast band-limited signal output from the digital audio filter circuit;
6. The digital / analog shared audio broadcast receiving apparatus according to claim 5, further comprising: an FM demodulation circuit for demodulating the audio signal from the FM broadcast band limited signal output from the M broadcast filter circuit.