Multi-band FM receiver for receiving FM broadcasting signals and TV broadcasting sound signals

A multi-band receiver for receiving broadcast signals divided by frequencies into an FM group and a TV group, the TV group including at least two different frequency ranges separated by a substantial frequency gap. The receiver includes a band selector for selecting a desired frequency group from the two group, a tuning controller for selecting a desired broadcast frequency within the desired group from a predetermined tuning band, an oscillator for separating signals of the desired frequency from the received broadcast signals and converting the separated signals into audio signals and a frequency adjuster responsive to the band selector and the tuning controller for automatically adjusting the oscillation frequency of the oscillator when the TV group has been selected for substantially removing the frequency gap from the predetermined tuning band.

FIELD OF THE INVENTION 
The present invention relates generally to a multi-band FM receiver, and 
more particularly to a multi-band FM receiver for receiving FM 
broadcasting signals and TV broadcasting sound signals. 
BACKGROUND OF THE INVENTION 
Recently, FM receivers which are adapted for receiving not only usual FM 
broadcasting signals, but also TV broadcasting sound signals have been 
developed. Such an FM receiver usually is provided with an FM receiving 
band and a TV sound receiving band. The bands are selected by a band 
selector. 
In a conventional multi-band FM receiver, however, the FM receiving band is 
assigned to receive the FM broadcasting signals and TV broadcasting sound 
signals of the lower frequency channels, i.e., the channels 1, 2 and 3. On 
the other hand, the TV sound receiving band is assigned to receive the TV 
broadcasting sound signals of the higher frequency channels, i.e., the 
channels 4, 5, ..., 12. 
This is because the frequencies of the lower frequency TV channels are 
closer to the frequencies of the FM broadcasting signals than to the 
frequencies of the higher frequency TV channels. Under the circumstances, 
the multiband FM receiver can be designed easily by assigning the lower 
frequency TV channels to the FM receiving band, instead of the TV sound 
receiving band. Thus, the TV channels are separated into at least two 
receiving bands in the conventional multi-band FM receiver. 
However, users of the conventional multi-band FM receiver must select the 
FM receiving band, when reception of the TV broadcasting sound signals of 
any the lower frequency channels is desired. Therefore, the conventional 
multi-band FM receiver has a drawback in that it confuses the users, due 
to the inconsistency between the use of the FM receiving band and the 
reception of the TV sound signals. 
In addition, the FM broadcasting signals and the TV broadcasting sound 
signals are different in the degree of FM modulation. The degree of FM 
modulation of the TV broadcasting sound signals is less than that of the 
FM broadcasting signals. As a result, different sound levels are output 
from the FM receiver for the FM broadcasting signals and the TV 
broadcasting sound signals. Thus, a user must operate the volume control 
for adjusting the output sound level, when changing between the FM 
broadcasting signals and the TV broadcasting sound signals in the FM 
receiving band. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a 
multi-band FM receiver in which an FM receiving band and a TV sound 
receiving band are assigned to exclusive reception of the FM broadcasting 
signals and the TV broadcasting sound signals, respectively. 
Another object of the present invention is to provide a multi-band FM 
receiver in which the lower frequency channels and the higher frequency 
channels of the TV broadcasting signals are combined in a single TV sound 
receiving band. 
In order to achieve the above object, a multi-band FM receiver according to 
one aspect of the present invention in which the receiver includes a band 
selector for selecting a desired frequency group from the two group, a 
tuning controller for selecting a desired broadcast frequency within the 
desired group from a predetermined tuning band, an oscillator for 
separating signals of the desired frequency from the received broadcast 
signals and converting the separated signals into audio signals and a 
frequency adjuster responsive to the and selector and the tuning 
controller for automatically adjusting the oscillation frequency of the 
oscillator when the TV group has been selected for substantially removing 
the frequency gap from the predetermined tuning band. 
Additional objects and advantages of the present invention will be apparent 
to persons skilled in the art from a study of the following description 
and the accompanying drawings, which are hereby incorporated in and 
constitute a part of this specification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be described in detail with reference to the 
accompanying drawing. 
Referring now to the accompanying drawings, an embodiment of the multi-band 
FM receiver according to the present invention will be described in 
detail. 
In the accompanying drawing, an input terminal 11 is provided for receiving 
RF signals of the FM broadcasting signals and the TV broadcasting sound 
signals. The RF signals are supplied to a frequency converter 12. The 
frequency converter 12 is also supplied with a local oscillation signal 
from a local oscillation circuit 100, which will be described in detail 
later. 
Therefore, the RF signal is converted to an intermediate frequency signal 
in the frequency converter 12. The intermediate frequency signal output 
from the frequency converter 12 is supplied to an intermediate frequency 
amplifier 13. The intermediate frequency amplifier 13 amplifies the 
intermediate frequency signal to a predetermined level. The amplified 
intermediate frequency signal is supplied to an FM demodulator 14. The FM 
demodulator 14 demodulates the intermediate frequency signal so that a 
sound signal is obtained from the FM demodulator 14. The sound signal 
output from the FM demodulator 14 is given to an audio amplifier (not 
shown) for driving a loudspeaker. 
The local oscillation circuit 100 has a phase locked loop (referred as PLL 
hereafter) configuration. That is, the local oscillation circuit 100 is 
provided with a voltage controlled oscillator (referred as VCO hereafter) 
15, a resonance circuit 15a which is a part of the VCO 15, a buffer 
amplifier 16, a coupling capacitor 17, a two-state frequency divider 18, a 
system control section 19, a low pass filter (referred as LPF hereafter) 
20 and a reference signal oscillator 21. The VCO 15 and the other 
components are connected in the form of the PLL. The local oscillation 
circuit 100 generates a local oscillation signal stabilized in the 
frequency by the reference signal oscillator 21. However, the frequency of 
the local oscillation signal is varied by the system control section 19. 
The frequency dividing ratio N1 of the two-state frequency divider 18 is 
changeable between two ratios, e.g., 1 and 1/2. 
Now, the system control section 19 will be described in detail. The system 
control section 19 is provided with a programmable frequency divider 22, a 
phase comparator 23 and a processor 24. The processor 24 may usually be 
comprised of a microcomputor. The programmable frequency divider 22 
divides an output from the two-state frequency divider 18. The frequency 
dividing ratio N2 of the programmable frequency divider 22 is controlled 
by the processor 24. The phase of the output of the programmable frequency 
divider 22 is compared with the phase of the reference frequency signal 
from the reference signal oscillator 24. The phase error signal obtained 
by the phase comparator 23 is fed back to the VCO 15 through the LPF 20. 
Thus, the frequency of the local oscillation signal generated by the VCO 
15 is controlled in accordance with frequency dividing ratio control data 
D1 applied from the processor 24 to the programmable frequency divider 22. 
The frequency dividing ratio control data D1 is varied by tuning data 
supplied from a tuning controller 25 coupled to the system control section 
19. Thus, a user can select a desired broadcasting signal through the 
tuning controller 25. 
The resonance circuit 15a of the VCO 15 includes a variable capacitor 26 
and a series circuit of inductor coils 27a and 27b. The variable capacitor 
26 is coupled in parallel with the series circuit of the inductor coils 
27a and 27b. A bias voltage source 28 applies a prescribed bias voltage Vb 
to a connection node 27c between the inductor coils 27a and 27b through a 
transistor 29 and a diode 30. The base of the transistor 29 is coupled to 
the processor 24 of the system control circuit 19 for receiving band 
control data D3. The collector of the transistor 29 is coupled to the 
resonance circuit 15a. Further, the collector of the transistor 29 is 
coupled to the two-state frequency divider 18. 
Further, the multi-band FM receiver is provided with a band selector 31. 
The band selector 31 has a slider 31a movable between an FM position 
(shown by a broken line) and a TV position (shown by a solid line). In the 
TV position, the slider 31a supplies the predetermined bias Vb of the bias 
voltage source 28 to the processor 24 through a first selector terminal 
31b. In the FM position, the slider 31a supplies the predetermined bias 
Vb to the FM demodulator 14 through a second selector terminal 31c. 
The processor 24 generates the receiving band control data D3 in response 
to the bias voltage Vb supplied from the band selector 31. That is, the 
processor 24 generates the receiving band control data D3 when the TV 
position is selected in the band selector 31. The receiving band control 
data D3 automatically changes between two states, e.g., between a low 
level "L"or "0" and a high level "H" or "1", in response to selection of 
the lower channels 1, 2 and 3 or the high channels 4, 5, . . . , 12 of the 
TV broadcasting signals. 
Now, the operation of the multi-band FM receiver will be described in 
detail. 
When setting to the FM receiving band is assumed, the output of the first 
selector terminal 31b of the band selector 31 becomes the low level "0". 
The output of the level "0" is input to the processor 24 and the processor 
24 responds to this so that a fixed output "1" is obtained at a band 
control data output terminal 19a. That is, the output level of the control 
data output terminal 19a is fixed to the level "1" in the selection of the 
FM position. In response to the level "1", the transistor 29 is turned off 
and the diode 30 is cut off. Therefore, the series circuit of inductor 
coils 27a and 27b connected in parallel to the variable capacitor 26 is 
activated, and the resonance frequency of the resonance circuit 15a is 
determined by the variable capacitor 26 and the coils 27a and 27b. The 
collector output of the transistor 29, at this time, further is supplied 
to the control terminal 18a of the two-state frequency divider 18. Thus, 
the frequency dividing ratio N1 of the two-state frequency divider 18 is 
set, e.g. to 1. 
When the band selector 31 is changed over to the TV position, the output of 
the band selector 31 through the first selector terminal 31b becomes the 
high level "1". At this moment, the output level on the band control data 
output terminal 19a of the system control section 19 becomes variable 
between a high level "1" and a low level "0". 
When the tuning controller 25 selects any one of the lower channels 1, 2 
and 3, the receiving band control data D3 on the band control data output 
terminal 19a becomes the high level "1". When the tuning controller 25 
selects any one of the higher channels 4, 5, . . . , and 12, the receiving 
band control data D3 on the band control data output terminal 19a becomes 
"0". The receiving band control data D3 is automatically changed between 
the levels "1" and "0" by the processor 24. By the output level "1" on the 
band control data output terminal 19a of the system control section 19, 
the transistor 29 is turned on and the diode 30 also is turned on. As a 
result, the connection node 27c between the inductor coils 27a and 27b is 
grounded in respect to the oscillation signal. Thus, the inductor coil 27b 
is grounded. 
Therefore, the resonance frequency of the resonance circuit 15a is 
determined by the variable capacitor 26 and the inductor coil 27a. At the 
same time, the control terminal of the two-state frequency divider 18 is 
supplied with the bias "1", so that the frequency dividing ratio N1 of the 
two-state frequency divider 18 is set, e.g. to 1/2. 
According to the automatic changes of the resonance frequency of the 
resonance circuit 15a or the frequency dividing ratio N1 of the two-state 
frequency divider 18, the frequency band gap between the group of the 
lower channels 1, 2, 3 and the other group of the higher channels 4, 5, 
... 12 is substantially eliminated. The tuning operation by the tuning 
controller 25, then, become easy. 
Furthermore, the bias voltage Vb of the bias voltage source 28 is applied 
to the FM demodulator 14 through the second selector terminal 31c of the 
band selector 31. By this bias voltage Vb, the audio volume level output 
from the FM demodulator 14 is modified so that the level difference 
between audio outputs of the FM reception and the TV sound reception is 
eliminated. 
Usually, as the lower channels 1, 2 and 3 of the TV broadcasting signal are 
received in the FM frequency band, a difference of sound volume is 
produced due to the difference of the degree of modulation degree between 
the FM broadcast wave and television sound signal. However, in the system 
of the invention such problem is not produced. 
In the conventional system explained above, the lower channels 1, 2 and 3 
are received in the usual receiving condition of the FM receiving band, so 
that a band selector does not correspond to the actually received band, 
i.e., the FM band and the TV band. 
In this invention, however, the lower channels 1, 2 and 3 and the higher 
channels 4, 5, . . . , and 12 are included within a single receiving band, 
without widening the tuning range in the TV band. As a result, the 
operation of the band selector accurately corresponds to the actually 
received channel. That is, the circuit of inductor coils 27a and 27b at 
the local oscillation circuit 100 and the two-state frequency divider 18 
are suitable in receiving the all channels 1 through 12 of the TV 
broadcasting signals in a single TV receiving band. 
While there has been illustrated and described what are at present 
considered to be preferred embodiments of the present invention, it will 
be understood by those skilled in the art that various changes and 
modifications may be made, and equivalents may be substituted for elements 
thereof without departing from the true scope of the invention. In 
addition, many modifications may be made to adapt a particular situation 
or material to the teaching of the present invention without departing 
from the central scope thereof. Therefore, it is intended that this 
invention not be limited to the particular embodiment disclosed as the 
best mode contemplated for carrying out this invention, but that the 
invention include all embodiments falling within the scope of the appended 
claims.