Automatic scanning tuner

In an automatic scanning tuner which stops at tuned stations in scanning up and down a range of frequencies, apparatus is provided for ignoring stations at which a user does not wish the tuner to stop as it moves up or down the dial. Information regarding the stations to be ignored may be stored in advance in a memory, such as a RAM.

BACKGROUND OF THE INVENTION 
The present invention relates to an automatic scanning tuner for 
automatically scanning a tuning frequency to search for a desired station. 
Conventional tuners have had a receiving frequency incremented or 
decremented in accordance with an automatic scanning operation, the 
scanning operation being stopped immediately upon detection of a station 
to be received so that the searched station can be received thereafter. 
This automatic scanning function is a very effective method of channel 
selection and therefore is provided in many tuners. 
Generally, such a tuner is provided with a preset function in which 
frequency information of predetermined stations is preset, that is stored 
in advance, and this information is selectively or automatically 
sequentially called out by the operation of a special key so that a 
desired station is channel-selected in accordance with the called-out 
information. 
As described above, channel selection of a preset station is performed by 
use of preset information. However, when a user considers using the 
automatic scanning function, there are a few cases where the user wants to 
channel-select a station which has been preset, but in many cases, the 
user rather feels it troublesome when scanning stops at every preset 
station. Particularly, the troublesome feeling may be increased in 
countries like the United States which have so many stations that scanning 
will be stopped very often if an automatic scanning mode is selected. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to remedy the foregoing 
deficiencies in the prior art. 
It is another object of the present invention to provide an automatic 
scanning tuner in which scanning is not stopped at a preset station when 
in an automatic scanning mode, so as to reduce a user's unease, and 
accordingly improve ease of use. 
In order to attain the foregoing objects of the present invention, the 
automatic scanning tuner comprises: automatic scanning start operation 
means for instructing a start of automatic scanning; tuning frequency data 
generation means for shifting tuning frequency data in accordance with 
operation of the automatic scanning start operation means to change a 
tuning frequency; tuning detection means for detecting whether tuning to 
the tuning frequency has been carried out, the detection being based on 
the tuning frequency data from the tuning frequency data generation means; 
storage means for storing, in advance, preset data regarding a tuning 
frequency; and judgment means for judging whether preset data 
corresponding to the tuning frequency data generated by the tuning 
frequency data generation means are stored in the storage means, wherein 
when the tuning detection means detects a tuned state, the changing 
operation of the tuning frequency by the tuning frequency data generation 
means is not stopped when the judgment means judges that preset data 
corresponding to the tuning frequency data are stored in the storage means 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
First, for better understanding of the present invention, the basic 
construction of the present invention will be described with reference to 
FIG. 1. As shown in FIG. 1, the automatic scanning tuner according to the 
present invention includes an automatic scanning start operation circuit 
9.sub.1 for instructing start of automatic scanning. A tuning frequency 
data generation circuit 8a.sub.1 shifts tuning frequency data in 
accordance with an operation of the automatic scanning start operation 
circuit 9.sub.1 to change a tuning frequency. A tuning detection circuit 
8a.sub.2 detects whether tuning has been made to the tuning frequency, the 
determination being based on the tuning frequency data received from the 
tuning frequency data generation circuit 8a.sub.1. 
A storage device 8b, which may be a RAM, stores preset data about a tuning 
frequency in advance. A judgment circuit 8a.sub.3 judges whether preset 
data corresponding to the tuning frequency data generated by the tuning 
frequency data generation circuit 8a.sub.1 are stored in the storage 
device 8b. In the operation of the device, when the tuning detection 
circuit 8a.sub.2 detects a tuned state, the changing operation of the 
tuning frequency by the tuning frequency data generation circuit 8a.sub.1 
is not stopped when the judgment circuit 8a.sub.3 judges that preset data 
corresponding to the tuning frequency data are stored in the storage 
device 8b. 
In this configuration, when the automatic scanning start operation circuit 
9.sub.1 is operated so as to initiate automatic scanning, the tuning 
frequency data generation circuit 8a.sub.1 shifts tuning frequency data to 
change the tuning frequency. The tuning detection circuit 8a.sub.2 detects 
whether tuning has been made to the tuning frequency on the basis of the 
tuning frequency data from the tuning frequency data generation circuit 
8a.sub.1. If a tuned state is detected, the judgment circuit 8a.sub.3 
judges whether data corresponding to the tuning frequency at the time upon 
detection of the above-mentioned tuned state are included in the preset 
data stored in advance in the storage device 8b. If the output of the 
judgment circuit 8a.sub.3 indicates that the data does not so correspond, 
the changing operation of the tuning frequency data being executed by the 
tuning frequency data generation circuit 8a.sub.1 stops so as to terminate 
the automatic scanning operation. 
Consequently, in an automatic scanning mode, it is possible to scan 
not-preset stations effectively without stopping the scanning operation at 
stations which have been preset. 
Next, a preferred embodiment of the present invention will be described 
with reference to the drawings. 
FIG. 2 is a block diagram illustrating an embodiment of the automatic 
scanning tuner according to the present invention. In FIG. 2, the circuit 
construction includes an antenna 1, an RF amplifier 2, a mixer 3, an IF 
amplifier 4, and a detector 5. The circuit also includes a VCO 6, which in 
turn includes a local oscillator. The circuit further includes a PLL 
circuit 7 for locking an oscillation frequency, a control section 8, and 
an operation section 9. 
The PLL circuit 7 includes a programmable frequency divider, a phase 
comparator, a reference oscillator, a low pass filter, (all not shown) and 
so on. The control section 8 includes a CPU 8a (which may be a 
microprocessor) which operates on the basis of a predetermined program, 
and a RAM 8b for storing preset data. The control section 8 is arranged so 
as to set frequency division ratio, as frequency information, for the 
programmable frequency divider of the PLL circuit 7. The operation section 
9 includes an automatic scanning (up/down) start key, a preset scanning 
start key, a preset channel-selection key, a preset memory key, and so on. 
In the above-mentioned configuration, if the control section 8 supplies 
frequency dividing ratio data to the programmable frequency divider of the 
PLL circuit 7, the VCO 6 oscillates at a frequency corresponding to the 
data of frequency dividing ratio, and applies the oscillation output 
thereof to one of the inputs of the mixer 3. A reception signal received 
through the antenna 1 is applied, after being amplified in the RF 
amplifier 2, to the other input of the mixer 3, and a signal corresponding 
to a difference or sum of the two input signals is produced at the output 
of the mixer 3. The output signal of the mixer 3 is intermediate-frequency 
amplified in the IF amplifier 4, and then is applied to the detector 5 so 
that an audio signal is obtained at the output of the detector 5. The 
detector 5 produces a tuning meter signal by use of its S-shaped 
characteristic and supplies the tuning meter signal to the CPU 8a of the 
control section 8. Since the tuning meter signal has a level which becomes 
L (low) in a tuned state, the CPU 8a can detect a tuned state on the basis 
of the tuning meter signal. 
Upon operation of the automatic scanning (up/down) start key of the 
operation section 9, the CPU 8a responds to sequentially increase/decrease 
the frequency dividing ratio data which is being outputted. In response to 
the change of the frequency dividing ratio data, the oscillation frequency 
of the VCO 6 is decreased/increased to perform automatic scanning. If a 
tuned station is located during this automatic scanning, the level of the 
tuning meter signal from the detector 5 becomes L, and the CPU 8a stops 
the increase/decrease of the frequency dividing ratio data to stop the 
automatic scanning, so that the tuned station can be revived. If the tuned 
station is not a desired one, the above-mentioned operation is resumed by 
operating the automatic scanning key again. It is possible that scanning 
is stopped in a predetermined period if there is a tuned station, and 
automatic scanning is resumed automatically if a stop operation is not 
carried out within the predetermined period. 
Upon detection of a tuned station on the basis of the tuning meter signal 
from the detector 5 as described above, the CPU 8a compares the frequency 
dividing ratio data which is being produced therefrom at that time with 
the preset data stored in the RAM 8b to judge whether any data 
corresponding to the frequency dividing ratio data is stored in the RAM 
8b. If the corresponding data is not stored in the RAM 8b, the CPU 8a 
stops the automatic scanning operation as has been described above, but if 
the corresponding data is stored, the CPU 8a continues the automatic 
scanning operation without stopping it. 
FIG. 3 is a flow chart illustrating a task to be executed by the CPU 8a on 
the basis of a predetermined program upon operation of the automatic 
scanning key. In FIG. 3, if the automatic scanning key is operated, in the 
first step S1, the CPU 8a changes the frequency dividing ratio data to be 
supplied to the programmable frequency divider of the PLL circuit 7, in 
order to increase/decrease the tuning frequency. Thereafter, the CPU 8a 
judges, on the basis of the level of the tuning meter signal from the 
detector 5, whether the tuning frequency change in the step S1 is tuned to 
a tuned state. When the level of the tuning meter signal is H (high) and 
the answer is "NO" (that is, no tuned state is located), the CPU 8a 
returns to the step S1 and changes the tuning frequency again. However, if 
the level of the tuning meter signal is L and the answer of the judgment 
is "YES", that is, a tuned state is located, the CPU 8a advances to the 
step S3 in which the CPU 8 a compares the frequency dividing ratio data 
corresponding to the tuning frequency changed in the above-mentioned step 
S1 with the data stored in advance in the RAM 8b for the sake of preset 
channel-selection, to judge whether data corresponding to the preset 
tuning frequency is included in the preset data in the RAM 8b. 
If the answer of the judgment in the step S3 in "NO", that is, preset data 
corresponding to the preset tuning frequency are not stored in the RAM 8b, 
the CPU 8a stops the above-mentioned operation caused by the operation of 
the automatic scanning key, so that the reception is performed at the 
tuning frequency changed and set in the step S1. However, if the answer of 
the judgment in the step S3 in "YES", that is, preset data corresponding 
to the preset tuning frequency are stored in the RAM 8b, the CPU 8a 
returns to the step S1 in which the CPU 8a changes the tuning frequency 
again. By the above-mentioned operation in the step S3, even if a tuned 
state is caused, the automatic scanning operation is continued without 
stopping when the tuned station is a preset one. Thus, the invention 
enables a user to preset stations which are to be ignored during a 
scanning operation. 
According to the present invention, as described above, the scanning 
operation is not stopped at a preset station in an automatic scanning 
mode, but stations which are not preset are scanned efficiently. 
Accordingly, it is possible to reduce the troublesome feeling of a user 
and thus improve ease of use. 
Various changes within the spirit of the invention will be apparent to 
those of working skill in this technology. Accordingly, the invention is 
to be constructed as limited by the appended claims.