JPH01252026A - Radio receiver - Google Patents

Abstract

PURPOSE:To suppress erroneous detection and to smoothly select a traffic information broadcasting station by providing the level detecting means of a receiving signal, a means to compare a level with a prescribed value and a gate means, which allows an output from an identifying signal detecting means when this level is larger than the prescribed value and prohibits the output when the level is smaller. CONSTITUTION:A receiving level detector 42 and a detuning degree detecting part 44 are provided in a car radio and a receiving signal level and a detuning degree are detected. Then, a gate part 54 is provided in the output side of a BK detecting part 46 and when the receiving level is lower than the prescribed value and a receiving station is detuned, the output of a BK detecting signal is prohibited. Thus, even when the BK detecting part 46 erroneously outputs the BK detecting signal by a large noise between stations to be peculiarly for FM, a weak signal noise, approach interference and separation interference, etc., the BK detecting signal is not inputted to a microcomputer 56. Accordingly, at the time of SK seak, the signal is prevented from being fixed to an erroneous receiving frequency.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a radio receiver, and in particular to SK and BK in the West German traffic information broadcasting system.

The present invention relates to a radio receiver that can detect identification signals such as DK without error.

[Conventional technology]

In West Germany, the entire country is divided into several suitable broadcasting areas, and one of the multiple FM stations in each area is designated as a traffic information broadcasting station (SK station) to broadcast traffic information at specific times. and a BK double signal indicating the SK double signal area indicating that it is an SK station, and a DK signal indicating that it is the traffic information broadcasting time period to be output at the corresponding time, and the identification signal detection unit In the car radio that exists, SK
An SDK broadcasting system that allows automatic station selection is being implemented.

An example of a car radio used in this system is shown in FIG.

An RF/IF section 12 is disposed horizontally on the antenna IO, and performs high frequency amplification, tuning, mixing, and intermediate frequency amplification based on the received signal from the antenna 10.

This RF/IF section 12 has a PLL circuit 14 for horizontal 12 control.
is connected, and the tuning frequency is varied according to the varactor voltage input from this PLL circuit 14.

The side 12 of the RF/IF section 12 is connected to a detection section 16, which performs detection on the intermediate frequency signal and generates a stereo composite signal (CO
MPO3IT[! 0UT).

This stereo composite signal is demodulated into left and right audio signals in a demodulation section (not shown), amplified, and outputted from a speaker.

An SK signal detection section 18 including a PLL circuit is also connected to the output side of the detection section 16, and detects the presence or absence of an SK multiplied signal in the received signal.

This SK signal detection section 18 and PLL circuit 14 are connected to a microcomputer 20.

An operation unit (not shown) is also connected to the microcomputer 20, and when the user performs a manual tuning operation, for example, it outputs frequency control data that varies according to the operation to the PLL circuit 14, and generates a corresponding varactor voltage. Vary the receiving frequency.

Also, when the user turns on the SDK key to listen to traffic information, automatic SK station selection (SK seek) is performed as follows, and continuously changing frequency control data is sent to the PLL circuit 14. output and generate a correspondingly varying varactor voltage to continuously vary the receiving frequency.

Then, when the receiving frequency reaches a certain frequency, S
When the K-fold signal 57 includes Hz general transmission wave, SK
The PLL circuit of the signal detection section 18 is locked after the pull-in operation, and outputs the lock signal to the microcomputer 20 as an SK multiplied signal detection (g).

When the microcomputer 20 receives this detection signal, it stops varying the frequency control data, fixes the reception frequency, and sets the reception state to the SK station.

If you want to move from this state to another SK station, turn on the seek key on the operation panel, and the microcomputer 20 will return to the SK seek system. Then, the next SK station is received.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, when a 51 KHz component is input to the SK signal detection section 1B, the lock is applied.
Large inter-office noise or weak signal noise in FM enters the SK signal detection unit 18, or interference noise that passes through the side peak of the band-limiting filter in the intermediate frequency stage due to nearby interference or M timing etc. There is a problem in that when the signal enters the signal detection section 18, a detection signal is erroneously output.

The present invention was made in view of such problems, and an object of the present invention is to obtain a radio receiver that can perform smooth SK seeking while suppressing false detection of identification signals due to inter-station noise and weak signal noise. The purpose is to suppress false detection of identification signals due to noise.

[Means to solve the problem]

In the radio receiver according to the present invention, the radio receiver includes an identification signal detection means for detecting an identification signal of a specific broadcast and outputting a detection signal, and a received signal level detection means for detecting the level of the received signal; Level determining means for comparing the received signal level with a certain predetermined value; and gate means for permitting detection signal output of the identification signal detecting means when the received signal level is greater than a certain predetermined value and prohibiting it when it is smaller. It is characterized by

Further, in another radio receiver according to the present invention, the out-of-tune detection means for detecting out-of-tune of the received signal and the identification signal detection means are enabled to output the detection signal when the #I key is detected, and are prohibited when the #I key is detected. It is characterized by having a gate means for

Further, the identification signal detection means in another radio receiver according to the present invention includes: an identification signal component extraction section that extracts an identification signal component from a received signal; an identification signal level detection section that detects the level of the identification signal component; The present invention is characterized in that it includes a detection signal generating section that generates a detection signal when the signal level is higher than a certain predetermined value.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIG. 1.

FIG. 1 shows the configuration of a car radio according to the present invention.

An RF/IF section 32 is interposed between the antennas 30, and performs high frequency amplification, tuning, mixing, and intermediate frequency amplification based on the signals received from the antenna 30.

This RF/IF section 32 has a PLL circuit 34 for inter-section 2 control.
is connected, and the tuning frequency is varied according to the varactor voltage input from this PLL circuit 34.

Intersection 2 of the RF/IF section 32 is connected to a detection section 36, which performs detection on the intermediate frequency signal and generates a stereo composite signal (CO
MPOSITE 0UT).

This stereo composite signal is demodulated into left and right audio signals in a demodulation section (not shown), amplified, and outputted from a speaker.

A reception level detection unit 4 is installed in the two wave stages between the RF/IF unit 32.
2 is connected, and the intermediate frequency signal is DC detected and output as a level detection signal of the received signal.

The relationship between the ANT input and the level detection signal is as shown in Figure 2.
The larger the ANT input, the smaller the level detection signal output.

Further, an M tuning detection section 44 is connected to the detection circuit of the detection section 36, and from the DC component of the detection output, the degree of detuning from the center frequency of the intermediate frequency signal is detected and output as an s tm degree detection signal. Ru.

FIG. 3 shows the relationship between the detuning frequency and the detuning degree detection signal.

A BK detection section 46 is connected to the output side of the detection section 36, and detects the presence or absence of a BK multiplied signal in the received signal.

Here, the SK station always sends a 57kHz SK double signal 23.
．． Six types of BK double signals from 75 to 53.98 Hz are transmitted, and 125 Hz D signals are transmitted during traffic information broadcasts.
K times the signal is transmitted.

In the BK detection section 46, an SK amplification circuit 48 is first connected to the output side of the detection section 36, and the SK amplification circuit 48 is connected to the output side of the detection section 36.
k) Iz acid component amplification is performed.

A BK bandpass filter 50 is connected to the output side of this SK amplifier circuit 48, and the 23. 75-53. The 98Hz BK signal component is passed.

A BK detection circuit 52 is connected to the output side of the BK bandpass filter 50, and when a BK acid component is input, it is DC-detected, and when a predetermined threshold level is exceeded, a BK detection circuit 52 is connected. ” outputs the BK detection signal.

In this way, the BK detection section 46 does not use a PLL for BK detection, so if a BK double signal exists in the received signal, it can be detected without time delay, and the BK detection signal can detect the SK
If it is substituted for the detection signal, the reliability will be increased compared to the case where the SK multiplied signal is simply detected.

The DC detection signal of the Naori K detection circuit 52 is transmitted to the SK amplifier circuit 4.
8, so that fluctuations in the detected signal due to fluctuations in received field strength are suppressed.

Here, the detected output has a band characteristic as shown in A in FIG. 5, which is determined by the inter-section filter characteristics of the RF/IF section 32, and the threshold for BK detection is set as indicated by the broken line B.

Even in the normal band part centered on the intermediate frequency f (range of output or f outside the normal band, ±10
Since there is sensitivity near a point far away from 0 kHz (range of Y and Y' in Figure 5), when side beak interference is received during detuning or close interference, an erroneous BK detection signal may be output. .

Therefore, the output side of the BK detection section 46 is connected to the microcomputer 56 via the gate section 54, and the BK detection signal passes through the gate section 54 and is input to the microcomputer 56 only when a predetermined condition is satisfied. It has become so.

The output sides of the reception level detection section 42 and detuning degree detection section 44 are connected to this gate section 54, and it is determined whether or not the BK detection signal can pass based on the level detection signal and the detuning degree detection signal.

The gate section 54 is configured as shown in FIG. 4, and the BK detection signal from the BK detection section 46 is sent to the BK input terminal BK, the level detection signal from the received level detection section 42 is sent to the first mute terminal MUTE1, and detuning degree detection. The M tone detection signals from the section 44 are respectively input to the second mute terminal MUTE2.

BK input terminal BK is connected to transistor Q1 via resistor R1.
is connected to the base of this transistor Q1.
The base of is connected to ground via resistor R2, and the emitter is connected directly to ground.

The collector of the transistor Ql is connected to the +5V power supply via the resistor R3, and the gate output terminal 0υ
Connected to T.

Further, a capacitor C is connected between the collector of the transistor Q1 and the ground to give a time constant to the rise and fall of the gate output.

If no other transistor is connected to the collector of transistor Ql, BK input to BK input terminal BK
When the detection signal is rH (when BK is not detected), transistor Q1 is turned on, C is discharged, and the gate output 0υT becomes "
It is in LJ state.

In this state, the SK station is received, and the BK detection unit 46 detects [L
” When the BK detection signal of the level is input, the transistor Q
l is turned off, and the gate output signal rises and becomes "H" with a time constant determined by R3 and C.

When the rising edge of this gate output signal is input, the microcomputer 56 determines that there is an rSK station.

If the BK detection signal is erroneously activated for a short period of time due to noise, etc.
When the transistor Ql is turned off for a short time due to the low voltage, the gate output remains low because C is not sufficiently charged, and the microcomputer 56 does not misjudge that the rSK station is on. Become.

Conversely, the gate output OUT is r based on the regular BK detection signal.
In this state, the BK detection signal becomes rH for a short time due to a sudden change in the electric field strength, and the transistor Q
When l is on for a short period of time, the gate output remains r)(J) because C is not sufficiently discharged, and the microcomputer 56 does not misjudge that there is no SK station.

On the other hand, the first mute terminal -UTE1 is connected to the base of a transistor Q2 via a resistor R4, the base of this transistor Q2 is connected to ground via a resistor R5, and the emitter is directly connected to ground. There is.

And the collector of transistor Q2 is the gate output terminal O
Connected to UT.

Resistors R4 and R5 are for setting a threshold level, and when the received signal level falls below a certain level and the level detection signal exceeds a certain predetermined level, transistor Q2 is turned on and the gate output terminal OUT is set to "L". .

Therefore, even if the BK detection unit 46 mistakenly outputs an “L” level BK detection signal due to large noise peculiar to FM output from the detection unit 36 when the signal is weak or there is no receiving station,
Gate output rising is prohibited.

Further, the second mute terminal MUTE 2 is connected to the base of a transistor Q3 via a resistor R6, and the base of this transistor Q3 is connected to the ground via a resistor R7, and the emitter is directly connected to the ground. .

And the collector of transistor Q3 is the gate output terminal 0
Connected to 1JT.

Resistors R6 and R7 are also for threshold level setting, and R
In the F/IF section 12, the two inter-section frequencies are detuned from the center frequency of the station, and when the detuning degree detection signal exceeds a certain predetermined level, the transistor Q3 is turned on and the gate output terminal 01lT is turned on.
Let it be "L".

The solid line C in FIG. 5 shows the relationship between the detuning frequency and the detuning degree detection signal, and the dashed line shows the threshold level.

Therefore, if there is a receiving station only within the regular intermediate frequency band, J
! Since +Im degree is small, transistor Q3 does not turn on,
On the condition that the transistor Q2 side is off, the BK detection section 46 detects the BK multiplied signal and outputs [LJ], the transistor Q1 turns off, and the gate output OUT changes to rH.

Conversely, if the receiving station is in the side peak interference region, the degree of detuning will increase, transistor Q3 will turn on, and gate output terminal 0 will be turned on.
Set 1IT to "L".

Therefore, even if the BK detection section 46 erroneously outputs an "L" level BK detection signal due to side peak interference at the time of proximity interference or detuning at the start of seek, the rise of the gate output is prohibited.

Particularly in car radios that apply soft mute according to the received signal level, side peak interference that occurs when the mute is shallow may cause the BK detection section 46 to output an erroneous BK detection signal, but as described above, Since output of the BK detection signal from the gate section 54 is prohibited when the degree of detuning is large, erroneous judgment by the micro combinator 56 can be prevented.

The gate section 54 and the PLL circuit 34 are connected to a microcomputer 56.

The microcomputer 56 has a manual tuning key and S
An operation unit (not shown) including a DK key, a seek key, etc. is also connected.

This microcomputer 56 is a CPU connected to a bus.
, ROM, and RAM, and performs manual tuning control, SK seek control, etc. according to the user's operation on the operation unit according to a predetermined program stored in the ROM.

Next, the operation of the above embodiment will be explained.

First, when the user operates the manual tuning key, the microcomputer 56 outputs frequency control data that varies according to the operation to the PLL circuit 34, generates a corresponding varactor voltage, and varies the receiving frequency.

When the user stops operating the manual tuning key after receiving a certain station, the microcomputer 56 fixes the frequency control data, fixes the varactor voltage output by the PLL circuit 34, and continues receiving the station.

At this time, the stereo composite signal frequency output from the detection section 36 is demodulated into left and right audio signals by a demodulation circuit, and then amplified by an amplifier and outputted from a speaker.

Unlike this, when the user turns on the SDK key to listen to traffic information, automatic SK station selection (SK seek)
I do.

That is, the microcomputer 56 outputs continuously changing frequency control data to the PLL circuit 34, generates a correspondingly changing varactor voltage, and continuously changes the receiving frequency.

Not only while a station is not being received, but also when the signal is weak even when a station is being received, the detection section 36 generates large inter-station noise peculiar to FM, and this noise causes the BK detection section 46 to erroneously receive an "L" BK detection signal. It may be output.

However, when the received signal level is low, the output voltage of the received level detection section 42 becomes high, and the transistor Q2 of the gate section 54 is turned on to maintain the gate output at "L".

Therefore, the rising edge of the gate output is not input to the microcomputer 56, and the receiving frequency continues to be changed.

When the reception signal level for a certain station increases due to subsequent changes in the reception frequency, and the output voltage of the reception level detection section 42 becomes low and transistor Q2 is turned off, the reception frequency is still slightly different from the center frequency of the station. If the output voltage of the detuning degree detection unit 44 is high and the transistor Q
3 is turned on and the gate output remains at "L".

Therefore, even if the BK detection section 46 erroneously outputs a BK detection signal due to proximity interference from a receiving station (including an SK station), rising input to the microcomputer 56 is blocked.

Then, when the center frequency of the station enters the regular intermediate frequency band due to a subsequent change in reception frequency, the output voltage of the MiMI degree detection section 44 decreases, and the transistor Q3 is turned off.

At this time, if the receiving station is an SK station, the BK detection section 4G outputs a normal BK detection signal "LJ", and the transistor Ql changes from on to off.

Then, all the transistors Q1 to Q3 are turned off, so that the capacitor C is charged through the resistor R3 and rises to rH with a predetermined time constant.

Based on this rise change, the microcomputer 56
It is determined that there is an rsK station, and the frequency control data is stopped from being varied and the reception frequency is fixed to set the reception state to an SK station.

As a result, if the receiving station is broadcasting traffic information, it can be heard with a good S/N ratio.

If the receiving station is not an SK station, the BK detection unit 46
” level BK detection signal is not output, and the gate output is also “L” level.
” at this time, the microcomputer 56
continues variable control of the receiving frequency.

However, when a certain normal station is received, the output voltage of the reception level detection section 42 and the M adjustment detection section 44 is low, and the transistors Q2 and Q3
When both are turned off, if pulse-like noise enters, the BK detection section 46 may erroneously output a BK detection signal of "L" for a short period of time.

At this time, transistor Q1 turns off for a short time, but since the rise of capacitor C is slow, noise disappears and BK
When the detection signal becomes "H" and the transistor Q1 is turned on, the voltage of the capacitor C returns to "L" without rising to the "H" level, thereby preventing the microcomputer 56 from malfunctioning.

Separately, when an SK station is being received, the output of the BK detection section 46 may be interrupted for a short period of time due to sudden changes in electric field strength.
When the level becomes "H", transistor Q1 is turned on for a short time.

However, since it takes time for capacitor C to discharge, if transistor Q1 is turned off again, the gate output will be
There is no need for the microcomputer 56 to misjudge that there is no rsK station.

When the user wants to change to another SK station while receiving reception from a certain SK station, the user turns on the seek key.

Then, the micro combinator 56 varies the frequency control data for the PLL circuit 34, thereby varying the reception frequency.

At this time, first, the SK station from which the signal was being received is detuned, deviates from the regular intermediate frequency band, and enters the side peak interference region, where the BK multiplied signal is received again.

Then, the BK detection section 46 once sets the BK detection signal to "H" and then receives 1TiAPl interference and outputs the BK detection signal of "L" again, and the output of this BK detection section 46 simply indicates that there is an rsK station. If you judge that, you will be fixed to the wrong reception frequency.

However, in this embodiment, when the SK station starts M tuning, the output voltage of the detuning degree detection section 44 increases, and the transistor Q3 of the gate section 54 turns on, discharging the capacitor C and making the gate output "L". The output of the detection unit 46 is S
When the K station is detuned, the microcomputer 56 does not manually start up even if it becomes LJ again, so there is no erroneous judgment that there is an rSK station.

Therefore, the reception frequency continues to change, and then another SK station in good radio wave condition is received, and when the center frequency of the station reaches the regular band of the IF filter, the gate output changes from "L" to rH again. energized by this rise, the microcomputer 56 determines that there is an rsK station and fixes the reception frequency.

This makes it possible to listen to traffic information from a new SK station.

According to this embodiment, the reception level detection section 42 is installed in the car radio.
A detuning degree detecting section 44 is provided to detect the received signal level and #Il adjustment, and a gate section 54 is provided on the output side of the BK detecting section 46 to detect when the received signal level is lower than a certain predetermined level and By prohibiting the output of the BK detection signal when a station is out of tune, the BK detection unit 46 may mistakenly detect BK due to large inter-station noise or weak signal noise peculiar to FM, or proximity interference or out-of-tune interference. Even if the signal is output, it can be prevented from being input to the microcomputer 56, so that it is no longer fixed to an incorrect reception frequency when performing SK seek.

In addition, since the BK detection section 46 does not use a PLL for BK detection, it can be detected without time delay if the BK multiplied signal exists in the received signal, and since the BK detection signal is substituted for the SK detection signal, the SK Increases detection reliability.

Furthermore, a capacitor C is connected between the output terminal of the gate section 54 and the ground.
and a transistor Q2. When the output of the BK detection section 46 changes while both Q3 are off, the gate output changes with a time constant, so that the output of the BK detection section 46 may be incorrectly changed for a short period of time due to noise etc. When the value changes, this can be absorbed, improving the detection accuracy of SK stations.

In addition, the BK detection circuit 52 has a time constant for the detection signal change when the reception of the BK multiplied signal is turned off, so that the "L" output does not change even if the BK multiplied signal cannot be detected for a short period of time due to a sudden change in electric field strength, etc. In this case, when searching for an SK station in preset reception, the turn-on of transistor Ql is delayed when switching channels, and transistors Q2. If there is no Q3 side, the BK multiplied signal of the new channel will be received again without the capacitor C being sufficiently discharged, and the transistor Q
1 is turned off, the rising edge of the gate output is not input to the microcomputer 56, and it is no longer possible to determine that there is an rSK station.

However, in this embodiment, when switching channels, the received signal level decreases or changes to M tone, and the transistor Q
2. Q3 turns on and discharges the capacitor C, so the new channel is an SK station and the BK detection section 46 is delayed.
When it outputs "L", the gate output rises from "L" to "H", and the microcomputer 56 can reliably determine that there is an rSK station.

In the above embodiment, a reception level detection section and a detuning degree detection section are provided separately, and when a predetermined threshold level set individually for each output voltage is exceeded, the output of the BK detection signal is prohibited. However, the BK detection output may be prohibited based on the output of only one of the reception level detection section or the detuning degree detection section, or the sixth detection section may be used as a detection section.
When using a detection IC circuit with a mute function in which the received signal level and detuning degree are combined and output as a mute signal as shown in the figure, when this mute signal exceeds a certain predetermined threshold level, the BK detection signal Output may also be prohibited.

Moreover, it can also be applied to BK detection or DK detection instead of SK detection.

〔Effect of the invention〕

According to the radio receiver of the present invention, the received signal level detecting means detects the level of the received signal, the level determining means compares the received signal level with a certain predetermined value, and the received signal level is lower than the certain predetermined value. By providing the gate means that allows the output of the detection signal of the identification signal detection means when it is large and prohibits it when it is small, it is possible to prevent seek malfunctions of a specific broadcasting station due to inter-station noise or noise when the signal is weak.

In addition, by providing detection means for detecting detuning of the received signal, and gate means for permitting the detection signal output of the identification signal detecting means when detuning is detected, and prohibiting it when the detuning is small, it is possible to prevent proximity interference. It is possible to prevent seek malfunctions of specific broadcast stations due to detuning and detuning interference.

Further, the identification signal detection means includes an identification signal component extractor for extracting the identification signal component from the received signal, an identification signal level detector for detecting the level of the identification signal component, and a detection signal for detecting when the received signal level is higher than a certain predetermined value. Real-time identification signal detection is possible by forming a detection signal generation section that generates a signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a car radio with a traffic information receiving function according to one embodiment of the present invention, FIG. 2 is a diagram explaining the operation of the reception level detection section in FIG. 1, and FIG. A diagram explaining the operation of the detuning degree detection section in Fig. 1, Fig. 4 a circuit diagram showing the configuration of the gate section in Fig. 1, and Fig. 5 explaining the relationship between the #l adjustment and the operation of the gate section. FIG. 6 is a circuit diagram of a detection IC with a mute function, and FIG. 7 is a block diagram of a conventional car radio with a traffic information receiving function. 42: Reception level detection section, 44: Detuning degree detection section, 46:
BK detection section, 48: SK amplifier circuit, 50: BK
Bandpass filter, 52: BK detection circuit, 54: Gate section, 56: Microcomputer, Q1 to Q3: Transistor. (V) Antenna input (dBu) Figure 2 (V) Figure 3 Figure 6

Claims (3)

[Claims] (1) A radio receiver including an identification signal detection means for detecting an identification signal of a specific broadcast and outputting a detection signal, comprising a reception signal level detection means for detecting the level of the reception signal, and a reception signal level detection means for detecting the reception signal level. The present invention is characterized by comprising: level determination means for comparing with a predetermined value, and gate means for permitting detection signal output of the identification signal detection means when the received signal level is greater than a predetermined value and prohibiting it when it is smaller. radio receiver. (2) In a radio receiver including an identification signal detection means for detecting an identification signal of a specific broadcast and outputting a detection signal, the radio receiver includes an out-of-tune detection means for detecting detuning of a received signal, and an out-of-tune detection means for detecting detuning of a received signal. When the detection signal output of the identification signal detection means is enabled,
A radio receiver characterized by comprising: a gate means for prohibiting when the radio receiver is small; (3) The identification signal detection means includes: an identification signal component extractor that extracts the identification signal component from the received signal; an identification signal level detector that detects the level of the identification signal component; 3. The radio receiver according to claim 1 or 2, further comprising: a detection signal generating section that generates a detection signal when the detection signal is large.