Apparatus for receiving broadcasting signals

An apparatus for receiving broadcasting signals, which includes a digital audio broadcasting signal receiving portion for receiving a digital audio broadcasting signal to obtain a reproduced digital broadcasting sound signal, an analog audio broadcasting signal receiving portion for receiving an analog audio broadcasting signal to obtain a reproduced analog broadcasting sound signal, a variable delay portion for delaying the reproduced analog broadcasting sound signal obtained from the analog audio broadcasting signal receiving portion to have a variable delay time, and a signal matching control portion for controlling the variable delay portion to reduce a difference in delay time between the reproduced analog broadcasting sound signal obtained through the variable delay portion and the reproduced digital broadcasting sound signal obtained from the digital audio broadcasting signal receiving portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an apparatus for receiving 
broadcasting signals, and more particularly, to a broadcasting signal 
receiving apparatus which is operative to receive not only an analog audio 
broadcasting signal, such as an amplitude-modulated (AM) audio 
broadcasting signal or a frequency-modulated (FM) audio broadcasting 
signal, but also a digital audio broadcasting (DAB) signal for obtaining a 
reproduced sound signal. 
2. Description of the Prior Art 
Although an analog audio broadcasting system which includes an AM audio 
broadcasting system in which audio information signals are transmitted in 
the form of an AM audio information signal and a FM audio broadcasting 
system in which audio information signals are transmitted in the form of a 
FM audio information signal, has been put to practical use for a long time 
in the field of audio broadcasting, there has been recently proposed to 
introduce a digital audio broadcasting system in which audio information 
signals are transmitted in the form of a digital audio information signal 
for the purpose of improving quality of audio information transmitted or 
received in the system. Especially, in the European Continent, the digital 
audio broadcasting system called "DAB" has been already put to practical 
use in some countries. 
It is expected that the digital audio broadcasting system would have great 
development henceforth so as to be in the mainstream in the field of audio 
broadcasting, in place of the analog audio broadcasting system, some time 
in the not so far future. However, at present, in a region wherein the 
digital audio broadcasting system has been already put to practical use or 
has been concretely planed to be materialized, a service area in which the 
digital audio information signal transmitted from a broadcasting station 
can be properly received is restricted to be relatively small. Therefore, 
in the case where the digital audio broadcasting is actually carried out, 
the analog audio broadcasting is also carried out, in addition to the 
digital audio broadcasting, so that the same program is transmitted 
through each of the digital audio broadcasting and the analog audio 
broadcasting at the same time. 
In the analog audio broadcasting, the analog audio information signal, such 
as the AM or FM audio information signal, is transmitted from an analog 
signal broadcasting station in the form of the analog audio broadcasting 
signal, and in the digital audio broadcasting, the digital audio 
information signal is transmitted from a digital signal broadcasting 
station in the form of the digital audio broadcasting signal. The digital 
audio broadcasting signal transmitted in the digital audio broadcasting 
contains audio information data which represents audio information. Such 
audio information data are usually subjected to a time interleaving 
arrangement for the purpose of minimizing deterioration resulting from 
data bit omission, data bit transformation and so on. 
The audio information data are transmitted in the form of a series of unit 
segments each having a time duration of, for example, 24 ms and 
constituting a logical frame. The time interleaving arrangement to which 
the audio information data are subjected is carried out with an 
interleaving completion segment consisting of successive sixteen logical 
frames. Accordingly, time interleaved audio information data corresponding 
to each group of successive sixteen original logical frames constitute 
successive sixteen new logical frames. This means that the time 
interleaved audio information data are provided with a relatively long 
delay time, such as more than 400 ms, which is longer than a time 
corresponding to successive sixteen original logical frames. Consequently, 
it is understood that the audio information data contained in the digital 
audio broadcasting signal transmitted from the digital signal broadcasting 
station has been provided with the relatively long delay time of, for 
example, 400 ms. 
Under such a situation as mentioned above, it has been proposed to use an 
analog/digital broadcasting signal receiver which is an apparatus for 
receiving both the analog audio broadcasting signal transmitted from the 
analog signal broadcasting station and the digital audio broadcasting 
signal transmitted from the digital signal broadcasting station in an area 
in which both of the analog audio broadcasting and the digital audio 
broadcasting are put into practice. The analog/digital broadcasting signal 
receiver comprises an analog audio broadcasting signal receiving portion 
for receiving the analog audio broadcasting signal and obtaining a 
reproduced sound signal based on the received analog audio broadcasting 
signal (a reproduced analog broadcasting sound signal), a digital audio 
broadcasting signal receiving portion for receiving the digital audio 
broadcasting signal and obtaining a reproduced sound signal based on the 
received digital audio broadcasting signal (a reproduced digital 
broadcasting sound signal), and a reproduced signal selecting portion for 
deriving selectively the reproduced analog broadcasting sound signal and 
the reproduced digital broadcasting sound signal. 
In the digital audio broadcasting signal receiving portion of the 
analog/digital broadcasting signal receiver, the audio information data 
contained in the received digital audio broadcasting signal are subjected 
to various signal processings so that the reproduced digital broadcasting 
sound signal is obtained. One of these signal processings to which the 
audio information data contained in the received digital audio 
broadcasting signal are subjected is a time de-interleaving arrangement 
for releasing the audio information data from the time interleaving 
arrangement to revert to original audio information data. The time 
de-interleaving arrangement to which the audio information data contained 
in the received digital audio broadcasting signal are subjected is carried 
out to each group of successive sixteen logical frames constituting the 
interleaving completion segment. That is, sixteen logical frames are 
successively derived from each of the interleaving completion segments of 
the audio information data contained in the received digital audio 
broadcasting signal to be stored in a memory device, and after those 
sixteen logical frames are once stored in the memory device, each of them 
is read from the memory device in a predetermined deinterleaving manner so 
that the time de-interleaving arrangement is carried out to each of the 
interleaving completion segments of the audio information data contained 
in the received digital audio broadcasting signal. 
Meanwhile, in the analog audio broadcasting signal receiving portion of the 
analog/digital broadcasting signal receiver, the received analog audio 
broadcasting signal is subjected to a demodulation processing and other 
signal processings, for example, a frequency-demodulation processing, a 
de-emphasis processing and so on in case of the FM audio broadcasting 
signal, so that the reproduced analog broadcasting sound signal is 
obtained. 
Then, the reproduced digital broadcasting sound signal obtained from the 
digital audio broadcasting signal receiving portion and the reproduced 
analog broadcasting sound signal obtained from the analog audio 
broadcasting signal receiving portion are selectively derived through the 
reproduced signal selecting portion in such a manner that the reproduced 
digital broadcasting sound signal is selected when it is obtained 
appropriately and the reproduced analog broadcasting sound signal is 
selected when the reproduced digital broadcasting sound signal is not 
obtained appropriately. 
In the analog/digital broadcasting signal receiver as described above, 
since the time de-interleaving arrangement is carried out to each group of 
successive sixteen logical frames constituting the interleaving completion 
segment of the audio information data contained in the received digital 
audio broadcasting signal in the digital audio broadcasting signal 
receiving portion, the time de-interleaved audio information data obtained 
in the digital audio broadcasting signal receiving portion are provided 
with a delay time which is longer than a time corresponding to the group 
of successive sixteen logical frame. Consequently, the reproduced digital 
broadcasting sound signal obtained based on the audio information data 
contained in the received digital audio broadcasting signal from the 
digital audio broadcasting signal receiving portion has a relatively long 
delay time, such as more than 400 ms, which has been caused mainly by the 
time de-interleaving arrangement carried out in the digital audio 
broadcasting signal receiving portion. 
On the other hand, the reproduced analog broadcasting sound signal which is 
obtained based on the received digital audio broadcasting signal subjected 
to the demodulation processing and other signal processings, for example, 
the frequency-demodulation processing, the de-emphasis processing and so 
on in case of the FM audio broadcasting signal, from the analog audio 
broadcasting signal receiving portion has a relatively short delay time, 
such as less than several tens .mu.s, which has been caused mainly by the 
signal processings carried out in the analog audio broadcasting signal 
receiving portion. 
Accordingly, when the digital audio broadcasting signal transmitted from 
the digital signal broadcasting station and the analog audio broadcasting 
signal transmitted from the analog signal broadcasting station are 
received respectively by the digital audio broadcasting signal receiving 
portion and the analog audio broadcasting signal receiving portion of the 
analog/digital broadcasting signal receiver under a situation in which the 
same program is transmitted from each of the digital signal broadcasting 
station and the analog signal broadcasting station at the same time, the 
reproduced digital broadcasting sound signal and the reproduced analog 
broadcasting sound signal, each of which represents the same sound 
information, are obtained with a relatively large time difference between 
each other from the digital audio broadcasting signal receiving portion 
and the analog audio broadcasting signal receiving portion, respectively. 
That is, first, the reproduced analog broadcasting sound signal with a 
relatively short delay time is obtained from the analog audio broadcasting 
signal receiving portion, and then, the reproduced digital broadcasting 
sound signal with a relatively long delay time, which represents the same 
audio information as that represented by the reproduced analog 
broadcasting sound signal, is obtained from the digital audio broadcasting 
signal receiving portion. 
In such a case, the relatively long delay time with which the reproduced 
digital broadcasting sound signal has as explained above results in the 
sum of the relatively long delay time, such as 400 ms, which the audio 
information data contained in the digital audio broadcasting signal has 
been provided when it is received by the digital audio broadcasting signal 
receiving portion and another relatively long delay time, such as 400 ms, 
which is caused in the digital audio broadcasting signal receiving 
portion, and therefore, reaches to, for example, 800 ms. 
The above mentioned operation by which the reproduced digital broadcasting 
sound signal and the reproduced analog broadcasting sound signal each 
representing the same sound information are obtained with the relatively 
large time difference between each other from the digital audio 
broadcasting signal receiving portion and the analog audio broadcasting 
signal receiving portion, respectively, brings disadvantages on the 
analog/digital broadcasting signal receiver as described below. 
When the analog/digital broadcasting signal receiver is equipped to a 
vehicle and moved with the vehicle from a position in a condition wherein 
the reproduced analog broadcasting sound signal is obtained appropriately 
from the digital audio broadcasting signal receiving portion to another 
position in a condition wherein the reproduced analog broadcasting sound 
signal is not obtained appropriately from the digital audio broadcasting 
signal receiving portion and thereby the signal selection by the 
reproduced signal selecting portion is changed from the reproduced digital 
broadcasting sound signal to the reproduced analog broadcasting sound 
signal, a discontinuation of signal resulting from the relatively large 
time difference is caused between the reproduced digital broadcasting 
sound signal which had been derived before the change in the signal 
selection by the reproduced signal selecting portion and the reproduced 
analog broadcasting sound signal which is derived after the change in the 
signal selection by the reproduced signal selecting portion. This results 
in deterioration in quality of the reproduced sound signals obtained from 
the analog/digital broadcasting signal receiver. 
Such a discontinuation of signal between the reproduced digital 
broadcasting sound signal and the reproduced analog broadcasting sound 
signal is also caused when the signal selection by the reproduced signal 
selecting portion is changed from the reproduced analog broadcasting sound 
signal to the reproduced digital broadcasting sound signal. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
apparatus for receiving broadcasting signals, in which a digital audio 
broadcasting signal receiving portion for receiving a digital audio 
broadcasting signal to obtain a reproduced digital broadcasting sound 
signal and an analog audio broadcasting signal receiving portion for 
receiving an analog audio broadcasting signal to obtain a reproduced 
analog broadcasting sound signal are provided, and which avoids the 
aforementioned disadvantages encountered with the prior art. 
Another object of the present invention is to provide an apparatus for 
receiving broadcasting signals, in which a digital audio broadcasting 
signal receiving portion for receiving a digital audio broadcasting signal 
to obtain a reproduced digital broadcasting sound signal and an analog 
audio broadcasting signal receiving portion for receiving an analog audio 
broadcasting signal to obtain a reproduced digital broadcasting sound 
signal are provided, and which can prevent the reproduced digital and 
analog broadcasting sound signals each representing the same sound 
information from being derived selectively with a relatively large time 
difference between each other from the digital and analog audio 
broadcasting signal receiving portions. 
A further object of the present invention is to provide an apparatus for 
receiving broadcasting signals, in which a digital audio broadcasting 
signal receiving portion for receiving a digital audio broadcasting signal 
to obtain a reproduced digital broadcasting sound signal and an analog 
audio broadcasting signal receiving portion for receiving an analog audio 
broadcasting signal to obtain a reproduced analog broadcasting sound 
signal are provided, and which can prevent the reproduced digital and 
analog broadcasting sound signals each representing the same sound 
information from being derived successively with a discontinuation of 
signal between each other from the digital and analog audio broadcasting 
signal receiving portions. 
A still further object of the present invention is to provide an apparatus 
for receiving broadcasting signals, in which a digital audio broadcasting 
signal receiving portion for receiving a digital audio broadcasting signal 
to obtain a reproduced digital broadcasting sound signal and an analog 
audio broadcasting signal receiving portion for receiving an analog audio 
broadcasting signal to obtain a reproduced analog broadcasting sound 
signal are provided, and which is operative to delay the reproduced analog 
broadcasting sound signal obtained from the analog audio broadcasting 
signal receiving portion so as to coincide in time substantially with the 
reproduced digital broadcasting sound signal obtained from the digital 
audio broadcasting signal receiving portion. 
According to the present invention, there is provided an apparatus for 
receiving broadcasting signals, which comprises a digital audio 
broadcasting signal receiving portion for receiving a digital audio 
broadcasting signal to obtain a reproduced digital broadcasting sound 
signal, an analog audio broadcasting signal receiving portion for 
receiving an analog audio broadcasting signal to obtain a reproduced 
analog broadcasting sound signal, a variable delay portion for delaying 
the reproduced analog broadcasting sound signal obtained from the analog 
audio broadcasting signal receiving portion to have a variable delay time, 
and a signal matching control portion for controlling the variable delay 
portion to reduce a difference in delay time between the reproduced analog 
broadcasting sound signal obtained through the variable delay portion and 
the reproduced digital broadcasting sound signal obtained from the digital 
audio broadcasting signal receiving portion. 
In the apparatus for receiving broadcasting signals thus constituted in 
accordance with the present invention, under a situation wherein the 
reproduced digital and analog broadcasting sound signals are obtained 
respectively from the digital and analog audio broadcasting signal 
receiving portions, the analog broadcasting sound signal obtained from the 
analog audio broadcasting signal receiving portion is delayed by the 
variable delay portion to have the variable delay time and the variable 
delay portion is controlled by the signal matching control portion so as 
to reduce the difference in delay time between the reproduced analog 
broadcasting sound signal obtained through the variable delay portion and 
the reproduced digital broadcasting sound signal obtained from the digital 
audio broadcasting signal receiving portion. 
Accordingly, even though the reproduced digital and analog broadcasting 
sound signals are obtained respectively from the digital and analog audio 
broadcasting signal receiving portions with a relatively large difference 
in delay time between each other, the difference in delay time between the 
reproduced digital broadcasting sound signal obtained from the digital 
audio broadcasting signal receiving portion and the reproduced analog 
broadcasting sound signal obtained through the variable delay portion is 
reduced to be, for example, substantially zero. As a result, when the 
reproduced digital broadcasting sound signal obtained from the digital 
audio broadcasting signal receiving portion and the reproduced analog 
broadcasting sound signal obtained through the variable delay portion are 
derived selectively to be used for reducing sound, a discontinuation of 
signal resulting from a time difference between the reproduced digital and 
analog broadcasting sound signals derived selectively is not caused 
substantially or is sharply reduced. 
Consequently, with the apparatus for receiving broadcasting signals 
according to the present invention, it is possible to avoid such 
disadvantages that the reproduced digital and analog broadcasting sound 
signals each representing the same sound information are derived with a 
relatively large time difference between each other from the digital and 
analog audio broadcasting signal receiving portions, respectively, and a 
discontinuation of signal resulting from the relatively large time 
difference is caused between the reproduced digital and analog 
broadcasting sound signals derived successively.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows schematically an embodiment of apparatus for receiving 
broadcasting signals according to the present invention. 
Referring to FIG. 1, the embodiment comprises of a digital audio 
broadcasting signal receiving portion 11, an analog audio broadcasting 
signal receiving portion 12, a variable delay portion 13, a signal 
matching control portion 14, a reproduced signal selecting portion 15, an 
output terminal 16, a control unit 17 and an input portion 18. 
The digital audio broadcasting signal receiving portion 11 is operative to 
tune in to a digital audio broadcasting signal transmitted from a digital 
signal broadcasting station for receiving the same. In the digital audio 
broadcasting signal receiving portion 11, audio information data contained 
in the received digital audio broadcasting signal are subjected to a time 
de-interleaving arrangement by a time de-interleaving portion to produce a 
reproduced digital broadcasting sound signal SAD constituted with time 
de-interleaved audio information data as a first reproduced sound signal. 
The analog audio broadcasting signal receiving portion 12 is operative to 
tune into an analog audio broadcasting signal, for example, an FM audio 
broadcasting signal transmitted from an analog signal broadcasting station 
for receiving the same. In the analog audio broadcasting signal receiving 
portion 12, the received FM audio broadcasting signal is subjected to a 
demodulation processing, a de-emphasis processing, a level control by a 
level control portion and so on to produce a reproduced analog 
broadcasting sound signal SAA as a second reproduced sound signal. 
The variable delay portion 13 is operative to delay the reproduced analog 
broadcasting sound signal SAA (the second reproduced sound signal) 
obtained from the analog audio broadcasting signal receiving portion 12 to 
have a variable delay time for producing a delayed reproduced analog 
broadcasting sound signal SAA' which is the reproduced analog broadcasting 
sound signal SAA obtained through the variable delay portion 13. The 
variable delay time which the variable delay portion 13 provides the 
reproduced analog broadcasting sound signal SAA with is controlled by the 
signal matching control portion 14. 
The signal matching control portion 14 is operative to detect a difference 
in delay time and a difference in level between the reproduced digital 
broadcasting sound signal SAD (the first reproduced sound signal) obtained 
from the digital audio broadcasting signal receiving portion 11 and the 
delayed reproduced analog broadcasting sound signal SAA' obtained through 
the variable delay portion 13. The signal matching control portion 14 is 
also operative to control, in response to a detection output of the 
difference in delay time between the reproduced digital broadcasting sound 
signal SAD and the delayed reproduced analog broadcasting sound signal 
SAA', the variable delay time which the variable delay portion 13 provides 
the reproduced analog broadcasting sound signal SAA with so as to reduce 
the difference in delay time between the reproduced digital broadcasting 
sound signal SAD and the delayed reproduced analog broadcasting sound 
signal SAA' and to control, in response to a detection output of the 
difference in level between the reproduced digital broadcasting sound 
signal SAD and the delayed reproduced analog broadcasting sound signal 
SAA', the level control portion in the analog audio broadcasting signal 
receiving portion 12 so as to reduce the difference in level between the 
reproduced digital broadcasting sound signal SAD and the delayed 
reproduced analog broadcasting sound signal SAA'. 
The reproduced signal selecting portion 15 is operative to derive 
selectively the reproduced digital broadcasting sound signal SAD obtained 
from the digital audio broadcasting signal receiving portion 11 and the 
delayed reproduced analog broadcasting sound signal SAA' obtained through 
the variable delay portion 13 to the output terminal 16. 
The control unit 17 is operative to perform control operations to the 
digital audio broadcasting signal receiving portion 11, the analog audio 
broadcasting signal receiving portion 12 and the reproduced signal 
selecting portion 15 in response to various command signals CX supplied 
from the input portion 18. In the control operation to the digital audio 
broadcasting signal receiving portion 11, various data are exchanged 
between the control unit 17 and the digital audio broadcasting signal 
receiving portion 11 and control signals are supplied to the digital audio 
broadcasting signal receiving portion 11 from the control unit 17. In the 
control operation to the analog audio broadcasting signal receiving 
portion 12, control signals are supplied to the analog audio broadcasting 
signal receiving portion 12 from the control unit 17. In the control 
operation to the reproduced signal selecting portion 15, the reproduced 
signal selecting portion 15 is caused by the control unit 17 to derive 
selectively the reproduced digital broadcasting sound signal SAD and the 
delayed reproduced analog broadcasting sound signal SAA'. 
With such a structural arrangement, each of the difference in delay time 
and the difference in level between the reproduced digital broadcasting 
sound signal SAD obtained from the digital audio broadcasting signal 
receiving portion 11 and the delayed reproduced analog broadcasting sound 
signal SAA' obtained through the variable delay portion 13, both of which 
are supplied to the reproduced signal selecting portion 15, is reduced to 
be, for example, substantially zero. Then, to the output terminal 16, for 
example, the reproduced digital broadcasting sound signal SAD supplied 
from the digital audio broadcasting signal receiving portion 11 to the 
reproduced signal selecting portion 15 is derived when the reproduced 
digital broadcasting sound signal SAD is obtained appropriately from the 
digital audio broadcasting signal receiving portion 11 and the delayed 
reproduced analog broadcasting sound signal SAA' supplied through the 
variable delay portion 13 to the reproduced signal selecting portion 15 is 
derived in place of the reproduced digital broadcasting sound signal SAD 
when the reproduced digital broadcasting sound signal SAD is not obtained 
appropriately from the digital audio broadcasting signal receiving portion 
11. 
FIGS. 2-A, 2-B and 2-C show in detail structures of the digital audio 
broadcasting signal receiving portion 11, the analog audio broadcasting 
signal receiving portion 12 , the variable delay portion 13 and the signal 
matching control portion 14. 
Referring to FIG. 2-A, in the digital audio broadcasting signal receiving 
portion 11, the digital audio broadcasting signal having reached to an 
antenna 21 is received through a tuning operation by a tuner 22. The 
tuning operation by the tuner 22 is performed in response to a tuning 
control signal STD supplied from the control unit 17. In the tuner 22, the 
received digital audio broadcasting signal is subjected to an amplifying 
processing and a frequency-converting processing to produce an 
intermediate frequency (IF) signal SID. The IF signal SID is supplied to 
an analog to digital (A/D) convertor 23. 
A digital IF signal DID corresponding to the IF signal SID is obtained from 
the A/D convertor 23 to be supplied to a quadrature demodulator 24. In the 
quadrature demodulator 24, the digital IF signal DID is subjected to a 
quadrature demodulation processing to produce I and Q signals DI and DQ 
which are a pair of quadrature demodulated output signals. 
The I and Q signals DI and DQ obtained from the quadrature demodulator 24 
are supplied to a first Fourier transform (FFT) differential demodulator 
25. In the FFT differential demodulator 25, each of the I and Q signals DI 
and DQ is subjected to transformation from a time domain signal to a 
frequency domain signal to produce control information data DCD 
representing control information transmitted through the Fast Information 
Channel (FIC) and audio information data DAD representing audio 
information transmitted through the Main Service Channel (MSC). The audio 
information data DAD have been time interleaved and provided with a 
relatively long delay time, such as more than 400 ms, which has been 
caused mainly by the time interleaving arrangement carried out in the 
digital signal broadcasting station. 
The control information data DCD obtained from the FFT differential 
demodulator 25 are supplied directly to a Vitervi decoder 26. The audio 
information data DAD obtained from the FFT differential demodulator 25 are 
subjected to a program selection processing by which a required program is 
extracted in a program selector 27 and supplied to a time de-interleaving 
portion 28. The program selection processing in the program selector 27 is 
performed in accordance with a program selection control signal SSP 
supplied from the control unit 17. 
In the time de-interleaving portion 28, the audio information data DAD 
supplied through the program selector 27 are subjected to a time 
de-interleaving arrangement. This time de-interleaving arrangement is 
carried out to each group of successive sixteen logical frames each having 
a time duration of, for example, 24 ms and constituting an interleaving 
completion segment of the audio information data DAD which have been time 
interleaved. On that occasion, the sixteen logical frames constituting the 
interleaving completion segment of the audio information data DAD are 
successively derived to be stored in a memory 29, and after those sixteen 
logical frames are once stored in the memory 29, each of them is read from 
the memory 29 in a predetermined deinterleaving manner so that the time 
de-interleaving arrangement is carried out to each of the interleaving 
completion segments of the audio information data DAD. Then, time 
de-interleaved audio information data DAD' are obtained from the time 
de-interleaving portion 28. 
The time de-interleaved audio information data DAD' thus obtained is 
provided with a relatively long delay time, such as more than 400 ms, 
which is caused by the time de-interleaving arrangement to which the audio 
information data DAD from the program selector 27 is subjected in the time 
de-interleaving portion 28, in addition to the relatively long delay time, 
such as more than 400 ms, of the audio information data DAD. This means 
that the time de-interleaved audio information data DAD' has totally a 
relatively long delay time, such as more than 800 ms. 
The time de-interleaved audio information data DAD' obtained from the time 
de-interleaving portion 28 are supplied to the Vitervi decoder 26. In the 
Vitervi decoder 26, the control information data DCD from the FFT 
differential demodulator 25 and the time de-interleaved audio information 
data DAD' from the time de-interleaving portion 28 are subjected 
respectively to error correction processings. The time de-interleaved 
audio information data DAD' subjected to the error correction processing 
are supplied from the Vitervi decoder 26 to a high efficiency decoder 30 
and the control information data DCD subjected to the error correction 
processing are supplied from the Vitervi decoder 26 to the control unit 
17. 
In the high efficiency decoder 30, the time de-interleaved audio 
information data DAD' subjected to the error correction processing are 
further subjected to a high efficiency decoding by which data suppressed 
in accordance with a high efficiency coding are expanded to produce 
decoded audio data DA. Further, program associated data DPA which are 
contained in the time de-interleaved audio information data DAD' are 
obtained from the high efficiency decoder 30 to be supplied to the control 
unit 17. The control unit 17 is operative to produce control data DVD 
based on the control information data DCD from the Vitervi decoder 26, the 
program associated data DPA from the high efficiency decoder 30 and so on 
and to supply the Vitervi decoder 26 with the control data DVD for 
performing a control operation to the Vitervi decoder 26. 
The decoded audio data DA obtained from the high efficiency decoder 30 are 
supplied to a digital to analog (D/A) convertor 31 to be converted to an 
analog sound signal corresponding to the decoded audio data DA. This 
analog sound signal is supplied to the reproduced signal selecting portion 
15 and the signal matching control portion 14 as the reproduced digital 
broadcasting sound signal SAD. Since the time de-interleaved audio 
information data DAD' obtained from the time de-interleaving portion 28 
has the relatively long delay time, such as more than 800 ms, as 
aforementioned, the reproduced digital broadcasting sound signal SAD 
obtained from the digital audio broadcasting signal receiving portion 11 
as described above has also a relatively long delay time, such as more 
than 800 ms. 
Meanwhile, in the analog audio broadcasting signal receiving portion 12 
shown in FIG. 2-B, the analog audio broadcasting signal having reached to 
an antenna 41 is received through a tuning operation by a tuner 42. The 
tuning operation by the tuner 42 is performed in response to a tuning 
control signal STA supplied from the control unit 17. In the tuner 42, the 
received analog audio broadcasting signal is subjected to an amplifying 
processing and a frequency-converting processing to produce an 
intermediate frequency (IF) signal SIA. The IF signal SIA is amplified by 
an IF amplifier 43 and supplied to a frequency-demodulator 44. 
In the frequency-demodulator 44, the IF signal DIA is subjected to a 
FREQUENCY-demodulation processing to produce a demodulated audio signal 
SA. The demodulated audio signal SA obtained from the 
frequency-demodulator 44 is supplied to a de-emphasis portion 45 to be 
subjected to the de-emphasis processing and thereby to produce a 
reproduced sound signal SA'. 
The reproduced sound signal SA' obtained from the de-emphasis portion 45 is 
supplied to a level control portion 46. In the level control portion 46, 
the level of the reproduced sound signal SA' is controlled in accordance 
with a level control signal SCL supplied from a signal matching control 
unit 50 provided in the signal matching control portion 14 to the level 
control portion 46. The reproduced sound signal SA' with its level 
controlled in the level control portion 46 is derived from the analog 
audio broadcasting signal receiving portion 12 as the reproduced analog 
broadcasting sound signal SAA. 
The reproduced analog broadcasting sound signal SAA thus obtained from the 
analog audio broadcasting signal receiving portion 12 is supplied to the 
variable delay portion 13. In the variable delay portion 13, the 
reproduced analog broadcasting sound signal SAA is converted to a digital 
sound signal DAA in an A/D convertor 47 to be stored in a memory 48. The 
storage of the digital sound signal DAA in the memory 48 is carried out in 
accordance with a storage control signal QW supplied from a memory control 
portion 51 provided in the signal matching control portion 14 to the 
memory 48. 
Further, in the variable delay portion 13, the digital sound signal DAA 
stored in the memory 48 is read from the memory 48 as a digital sound 
signal DAA'. The reading of the digital sound signal DAA from the memory 
48 is carried out in accordance with a reading control signal QR supplied 
from the memory control portion 51 provided in the signal matching control 
portion 14 to the memory 48. 
The digital sound signal DAA' thus obtained from the memory 48 is provided 
a delay time corresponding a time from the storage of the digital sound 
signal DAA in the memory 48 to the reading of the digital sound signal DAA 
from the memory 48, compared with the digital sound signal DAA obtained 
from the A/D convertor 47. Then, the digital sound signal DAA' obtained 
from the memory 48 is converted to an analog sound signal corresponding to 
the digital sound signal DAA' in a D/A convertor 49 and this analog sound 
signal obtained from the D/A convertor 49 is derived from the variable 
delay portion 13 as the delayed reproduced analog broadcasting sound 
signal SAA'. 
The delayed reproduced analog broadcasting sound signal SAA' thus obtained 
through the variable delay portion 13 is supplied to the reproduced signal 
selecting portion 15 and the signal matching control portion 14. This 
delayed reproduced analog broadcasting sound signal SAA' is provided with 
the delay time of the digital sound signal DAA' from the memory 48, which 
corresponds to the time from the storage of the digital sound signal DAA 
in the memory 48 to the reading of the digital sound signal DAA from the 
memory 48, in addition to a relatively short delay time, such as less than 
several tens .mu.s, of the reproduced analog broadcasting sound signal 
SAA, which is caused mainly by the frequency-demodulation processing to 
which the IF signal SIA is subjected and the de-emphasis processing to 
which the demodulated audio signal SA is subjected. 
In the signal matching control portion 14 shown in FIG. 2-C, the reproduced 
digital broadcasting sound signal SAD obtained from the digital audio 
broadcasting signal receiving portion 11 is subjected to an envelope 
detection in a detecting rectifier 53 and a detection output signal SED 
corresponding to the envelope wave form of the reproduced digital 
broadcasting sound signal SAD is obtained from the detecting rectifier 53. 
Further, the delayed reproduced analog broadcasting sound signal SAA' 
obtained through the variable delay portion 13 is subjected to an envelope 
detection in a detecting rectifier 54 and a detection output signal SEA 
corresponding to the envelope wave form of the delayed reproduced analog 
broadcasting sound signal SAA' is obtained from the detecting rectifier 
54. 
The detection output signal SED obtained from the detecting rectifier 53 
and the detection output signal SEA obtained from the detecting rectifier 
54 are supplied to a comparator 55. In the comparator 55, the envelope 
wave form of the reproduced digital broadcasting sound signal SAD and the 
envelope wave form of the delayed reproduced analog broadcasting sound 
signal SAA' are compared with each other based on the detection output 
signals SED and SEA. As a result, a comparison output signal SOT 
corresponding to a difference between the envelope wave form of the 
reproduced digital broadcasting sound signal SAD and the envelope wave 
form of the delayed reproduced analog broadcasting sound signal SAA' is 
obtained from the comparator 55. 
The comparison output signal SOT thus obtained from the comparator 55 
represents a difference in delay time between the reproduced digital 
broadcasting sound signal SAD and the delayed reproduced analog 
broadcasting sound signal SAA'. Accordingly, the detecting rectifiers 53 
and 54 and the comparator 55 constitute a time difference detecting 
portion for detecting the difference in delay time between the reproduced 
digital broadcasting sound signal SAD obtained from the digital audio 
broadcasting signal receiving portion 11 and the delayed reproduced analog 
broadcasting sound signal SAA' obtained through the variable delay portion 
13 and this time difference detecting portion produces the comparison 
output signal SOT as a detection output signal. 
The comparison output signal SOT is digitalized in an A/D convertor 56 to 
produce a digital signal DOT. The digital signal DOT corresponding to the 
comparison output signal SOT is supplied form the A/D convertor 56 to the 
signal matching control unit 50. The signal matching control unit 50 is 
operative to supply the memory control portion 51 with a memory control 
signal SCM which is formed based on the digital signal DOT in order to 
control the memory control portion 51 in such a manner that the storage 
control signal QW and the reading control signal QR supplied from the 
memory control portion 51 to the memory 48 are varied in response to the 
digital signal DOT and therefore the storage time of the digital sound 
signal DAA in the memory 48, namely, the delay time which the digital 
sound signal DAA is provided within the variable delay portion 13 is so 
controlled as to reduce the difference in delay time between the 
reproduced digital broadcasting sound signal SAD and the delayed 
reproduced analog broadcasting sound signal SAA' to be, for example, 
substantially zero. 
Further, in the signal matching control portion 14, a low frequency 
component of the reproduced digital broadcasting sound signal SAD obtained 
from the digital audio broadcasting signal receiving portion 11 is 
extracted to detect an average level of the reproduced digital 
broadcasting sound signal SAD in a low pass filter (LPF) 58 and a 
detection output signal SLD corresponding to the average level of the 
reproduced digital broadcasting sound signal SAD is obtained from the LPF 
58. Similarly, a low frequency component of the delayed reproduced analog 
broadcasting sound signal SAA' obtained through the variable delay portion 
13 is extracted to detect an average level of the delayed reproduced 
analog broadcasting sound signal SAA' in a LPF 59 and a detection output 
signal SLA corresponding to the average level of the delayed reproduced 
analog broadcasting sound signal SAA' is obtained from the LPF 59. 
The detection output signal SLD obtained from the LPF 58 and the detection 
output signal SLA obtained from the LPF 59 are supplied to a comparator 
60. In the comparator 60, the average level of the reproduced digital 
broadcasting sound signal SAD and the average level of the delayed 
reproduced analog broadcasting sound signal SAA' are compared with each 
other based on the detection output signals SLD and SLA. As a result, a 
comparison output signal SOL corresponding to a difference between the 
average level of the reproduced digital broadcasting sound signal SAD and 
the average level of the delayed reproduced analog broadcasting sound 
signal SAA' is obtained from the comparator 60. 
The comparison output signal SOL thus obtained from the comparator 60 
represents a difference in level between the reproduced digital 
broadcasting sound signal SAD and the delayed reproduced analog 
broadcasting sound signal SAA'. Accordingly, the LPFs 58 and 59 and the 
comparator 60 constitute a level difference detecting portion for 
detecting the difference in level between the reproduced digital 
broadcasting sound signal SAD obtained from the digital audio broadcasting 
signal receiving portion 11 and the delayed reproduced analog broadcasting 
sound signal SAA' obtained through the variable delay portion 13 and this 
level difference detecting portion produces the comparison output signal 
SOL as a detection output signal. 
The comparison output signal SOL is digitalized in an A/D convertor 61 to 
produce a digital signal DOL. The digital signal DOL corresponding to the 
comparison output signal SOL is supplied form the A/D convertor 61 to the 
signal matching control unit 50. The signal matching control unit 50 is 
operative to supply the level control portion 46 in the analog audio 
broadcasting signal receiving portion 12 with the level control signal SCL 
which is formed based on the digital signal DOL in order to control the 
level control portion 46 so as to reduce the difference in level between 
the reproduced digital broadcasting sound signal SAD and the delayed 
reproduced analog broadcasting sound signal SAA' to be, for example, 
substantially zero. 
With such control operations to the variable delay portion 13 and the level 
control portion 46 in the analog audio broadcasting signal receiving 
portion 12, which are conducted by the signal matching control portion 14, 
each of the difference in delay time and the difference in level between 
the reproduced digital broadcasting sound signal SAD and the delayed 
reproduced analog broadcasting sound signal SAA' both supplied to the 
reproduced signal selecting portion 15 is reduced to be, for example, 
substantially zero. 
As shown in FIG. 2-A, a selection control signal SSW which is produced in 
the control unit 17 in response to, for example, the command signal CX 
supplied from the input portion 18, is supplied to the reproduced signal 
selecting portion 15. The reproduced signal selecting portion 15 is 
operative, in accordance with the selection control signal SSW, to derive 
selectively the reproduced digital broadcasting sound signal SAD obtained 
from the digital audio broadcasting signal receiving portion 11 and the 
delayed reproduced analog broadcasting sound signal SAA' obtained through 
the variable delay portion 13 to the output terminal 16. Thereby, the 
reproduced digital broadcasting sound signal SAD is derived to the output 
terminal 16 when the reproduced digital broadcasting sound signal SAD is 
obtained appropriately from the digital audio broadcasting signal 
receiving portion 11 and the delayed reproduced analog broadcasting sound 
signal SAA' obtained through the variable delay portion 13 is derived to 
the output terminal 16 in place of the reproduced digital broadcasting 
sound signal SAD when the reproduced digital broadcasting sound signal SAD 
is not obtained appropriately from the digital audio broadcasting signal 
receiving portion 11. 
In such a case, since each of the difference in delay time and the 
difference in level between the reproduced digital broadcasting sound 
signal SAD and the delayed reproduced analog broadcasting sound signal 
SAA' both supplied to the reproduced signal selecting portion 15 is 
reduced to be, for example, substantially zero, a discontinuation of 
signal between the reproduced digital broadcasting sound signal SAD and 
the delayed reproduced analog broadcasting sound signal SAA' derived 
selectively is not caused substantially or is sharply reduced when the 
signal selection by the reproduced signal selecting portion 15 is changed 
from the reproduced digital broadcasting sound signal SAD to the delayed 
reproduced analog broadcasting sound signal SAA' or from the delayed 
reproduced analog broadcasting sound signal SAA' to the reproduced digital 
broadcasting sound signal SAD.