JPH0159770B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention mainly relates to two
The present invention relates to an automobile radio receiver having two receiving systems, and particularly relates to the configuration of an identity determiner that determines whether audio signals from the two receiving systems are the same.

In this type of car radio receiver, one receiving system receives broadcasts under the control of a microcomputer, while the other receiving system searches for a station with better reception, and uses an identity determiner to determine whether the broadcast content is the same. By determining whether or not the broadcast content is the same and sequentially selecting and receiving stations with better reception conditions, the system does not bother the listener even when the car moves beyond the service area of many broadcast stations. Therefore, it is possible to automatically continue receiving the same broadcast program in good reception condition.

FIG. 1 shows an example of this type of radio receiver. In the figure, 1 is an antenna, 2 is a distributor, 3 is a channel selection device, 4 is an intermediate frequency amplifier, 5 is a detector, and 6 is a first
7 is a receiving system (hereinafter referred to as receiving system A), 7 is a channel selection device,
8 is an intermediate frequency amplifier, 9 is a detector, 10 is a second receiving system (hereinafter referred to as receiving system B), 11 is an audio signal switch, 12 is a low frequency amplifier, 13 is a speaker,
14 is a first electric field detector, 15 is a second electric field detector, 16 is an identity determination device, 17 is a control device, 18
is a frequency display, and 19 is an operation key. In the radio receiver configured as described above, the broadcast wave signal induced in the antenna 1 is divided into two parts by the distributor 2 and given to the receiving system A6 and the receiving system B10. The tuning devices 3 and 7 are, for example, PLL synthesizer electronic tuners, which receive frequency data from the control device 17, convert only broadcast waves of that frequency into intermediate frequency signals, and output the signals. Intermediate frequency amplifiers 4 and 8 amplify the intermediate frequency signals and detectors 5 and 9
give to Detectors 5 and 9 detect intermediate frequency signals and output audio signals. In this way, receiving system A6
One of the audio signals obtained from the reception system B10 is selected by the audio signal switch 11, amplified by the low frequency amplifier 12, and reproduced by the speaker 13. The electric field detectors 14 and 15 are each connected to the receiving system A.
6 and the reception system B10 detect the reception level of each broadcasting station being received and send the corresponding signal to the control device 1.
7, and the identity determiner 16 is for determining whether or not the audio signals from the two receiving systems have the same content. The control device 17 is composed of, for example, a microcomputer, and controls the reception frequency and displays it on the frequency display 18 in response to operations on the operation keys 19, as well as automatically selecting the same broadcast content station. This automatic channel selection operation is performed as follows, for example. First, it is assumed that a certain station is received by the receiving system A6 by a listener's manual operation and is being reproduced through the audio signal switch 11. At this time, the control device 17
The reception frequency is scanned over the entire broadcast frequency band, and a station whose reception level is higher than that of the station being received by the receiving system A6 is searched from the signals of the electric field detectors 14 and 15. Based on this result, if there is a station with a high reception level, that is, a station with good reception condition, the identity determiner 16 determines whether the audio signals from the two reception systems have the same content.
Judgment is made using As a result, if it is determined that they are not the same, the scanning by the receiving system B10 is continued, and if it is determined that they are the same, the audio signal switch 11 is set to the receiving system B10 side, and the output audio signal of the receiving system B10 is reproduced. The display on the frequency display 18 is assumed to be the receiving frequency of the receiving system B10. In addition, the receiving system A6 continues scanning the receiving frequency, which has been performed by the receiving system B10 up to now. As a result of the above operation, all stations in the broadcasting frequency band with better reception conditions than the station currently being received will be tested, and even if there are several stations with the same broadcast content, the station with the best reception among them will be tested. This will continue to be the case.

A conventional identity determiner used in this type of radio receiver is shown in FIG. In the figure, 30, 31 are low-pass filters, 32, 33
is a zero cross detector, 34 is an exclusive OR circuit (hereinafter referred to as E-OR circuit), 35 is an integrator,
36 is a first voltage comparator, 37 is a second voltage comparator, 38 and 39 are detectors, and 40 and 41 are voltage comparators.

The audio signals from receiving system A6 and receiving system B10 are provided to zero cross detectors 32, 33 after high frequency components are removed by low-pass filters 30, 31, respectively. The zero cross detectors 32 and 33 output a binary signal of "H" level or "L" level, that is, a zero crossing wave, depending on the sign of the AC component of the input audio signal, and the output of the zero cross detectors 32, 33 is applied to the E-OR circuit 34. Here E
-OR circuit 34 outputs "L" level when two inputs are both "H" and "L", and outputs "H" level when one is "H" and the other is "L" and the integrator 35 converts this E-
This is to integrate the output of the OR circuit 34 for a predetermined period. Therefore, if the two audio signals given to the identity determiner 16 are exactly the same: the outputs of the zero cross detectors 32 and 33 will be at the "H" level or "L" level at the same time, and the output of the E-OR circuit 34 will be almost continuous. As a result, the output from the integrator 35 also becomes approximately equal to the "L" level. In addition, when the two audio signals have the same content and are in opposite phases to each other, the outputs of the zero cross detectors 32 and 33 are always at the "H" level while the other is at the "L" level, and the output of the E-OR circuit 34 is “H” almost continuously
level, and the output of the integrator 35 also becomes approximately equal to the "H" level. Next, if the contents of the two audio signals are different, the above relationship does not exist between the two outputs of the zero cross detectors 32 and 33, and if enough time is taken, the period during which they are both at the "H" or "L" level at the same time will occur. The periods during which one is at "H" level and the other is at "L" level become almost equal. For this reason E-OR
Considering an appropriate period, the output of the circuit 34 will be "H" for approximately 1/2 of the period and "L" for the remaining period. Therefore, the output of the integrator 35 becomes approximately an intermediate value between the "H" level and the "L" level.

From this, if a sufficient integration period is provided, whether or not the contents of the two audio signals are the same will clearly appear as the output of the integrator 35. Voltage comparator 3
6 gives a signal indicating that the contents are the same when the output of the integrator 35 is higher than the first judgment level eth ₁ , and the voltage comparator 37 gives a signal that the output of the integrator 35 is higher than the second judgment level eth ₂
If one of the two outputs of the voltage comparators 36 and 37, i.e., the identity determination signal, is "the same", the control device 17 outputs a signal indicating that the contents are the same when the two audio signals are smaller. are determined to be the same. Here, if the "H" and "L" levels of the E-OR circuit 34 output are V _H and O, respectively,
eth ₁ is a level determined as appropriate in the range of 1/2V _H <eth ₁ <V _H , and eth ₂ is in the range of O<eth ₂ <1/2V _H .
In the above explanation, we have considered an ideal case where there is no time difference between two audio signals with the same content, but in actual broadcast audio, there is usually a time difference τ. Here, for convenience,
Considering a repeating wave with frequency f and period T (=1/f) as an audio signal, due to the time difference τ, if two audio signals are in phase, a period of 2τ during period T (here, T
>2τ) The outputs of the zero cross detectors 32 and 33 do not match, and the output eo of the integrator 35 becomes approximately eo=2τ/TV _H =2·f·τ·V _H (1). Similarly, when the two audio signals are in opposite phase, eo = (1-2・τ/T) V _H = (1-2f・τ) V _H (2), and both have no time difference. This deviates from the ideal case and reduces the accuracy of the determination. Here, the adverse effect due to the time difference τ is the frequency f
It is clear that the higher the value, the larger the value, and the low-pass filters 30 and 31 are used to remove this high-frequency component in advance to make the determination more reliably. Next, the detectors 38, 39 and the voltage comparators 40, 41
detects the audio signal level output from the low-pass filters 30 and 31 and provides a signal indicating whether or not the audio signal level is sufficient for determination, that is, an audio level determination signal, to the control device 17; When performing the identity determination, the control device 17 selects a period during which the audio level is sufficient, thereby making it possible to perform the determination with high accuracy in a relatively short time.

As mentioned above, the conventional identity determiner prevents the deterioration in determination accuracy due to the time difference τ between two audio signals by removing the high-frequency components of the audio signal using a low-pass filter. This is fine when the time difference τ is relatively small, but in actual broadcast audio signals, the time difference τ can reach as much as 1 [ms], or in rare cases, it can reach several [ms]. Figure 3 is
This shows the relationship between the integrator output, time difference τ, and frequency f from equations (1) and (2), and as shown by eo in the figure,
In order to make a correct determination for a time difference of 1 [ms], it is necessary to sufficiently attenuate components of at least 250 [Hz] or higher using a low-pass filter. However, this removes the main components of the audio signal, making the determination operation difficult.

This invention was made in order to eliminate the drawbacks of the conventional identity determiner as described above, and a delay circuit such as a shift register is provided in the audio signal path to relatively delay one of the two audio signals in advance and perform the determination. It is an object of the present invention to provide an identity determiner that operates satisfactorily even when there is a relatively large time difference between two audio signals by adding this to a conventional circuit.

FIG. 4 is a block diagram showing an embodiment of the present invention, in which 42 and 43 are shift registers, 44 is a clock generator, 45 and 46 are E-OR circuits, and 4
7 and 48 are integrators, and 49 and 50 are combiners.
In the identity determiner 16 configured in this way, the two zero-crossing waves provided by the zero-crossing detectors 32 and 33 are sent to the shift registers 42 and 4, respectively.
3, the signal is delayed for a time t and output. The clock generator 44 supplies shift registers 42 and 43 with
This clock _pulse is selected to be sufficiently higher than the cutoff frequency of the low-pass filters 30 and 31, so that the shift register 4
At No. 2 and 43, the zero-crossing wave is output almost unchanged. It goes without saying that if the number of stages of the shift register is N, then the delay time t is t=N/ _fcLk .

Next, the E-OR circuit 34 and the integrator 35 operate exactly the same as in the conventional example, and the E-OR circuit 4
5. The integrator 47 uses an E-OR circuit 46 for the zero-crossing wave delayed by the shift register 42 and the zero-crossing wave output from the zero-cross detector 43, and the integrator 48 uses the zero-crossing wave delayed by the shift register 43 and the zero-crossing detector. The same operation as in the conventional example is performed for each of the 42 output zero-crossing waves. Here, since one of the zero-crossing waves input to the E-OR circuits 46 and 47 is delayed by a time t, the integrator 4
The outputs of 7 and 49 each have a time difference (delay) between the audio signal of receiving system A6 and the audio signal of receiving system B10.
becomes the maximum or minimum when there are t and -t, and provides the best matching judgment. Third
Figures e ₁ and e ₂ respectively show the integrator 42 when the delay time t in the shift registers 32 and 33 is 0.8 [ms].
and 43. From the figure, e ₀ , e ₁ ,
e ₂ , that is, ±1.2 [m
It can be seen that the low-pass filters 30 and 31 can sufficiently attenuate approximately 500 [Hz] or more for the same content audio signals having a time difference of 500 [Hz], thereby making it possible to accurately determine the same content. It is also clear from the figure that if the delay time t of the shift registers 42 and 43 is shortened, the time difference between the two audio signals that is allowable for determination becomes smaller, but it is possible to further increase the cutoff frequency of the low-pass filters 30 and 31. Conversely, it is also possible to increase the time difference allowable for determination by increasing the delay time t.

Next, the synthesizer 49 receives the outputs of the integrators 35, 47, and 48 and is configured to always output the maximum value among them, and the synthesizer 50 receives the outputs of the integrators 35, 47, and
It is configured to receive the outputs of 7 and 48 and always output the minimum value among them. Therefore, the voltage comparators 36 and 37 operate in the same manner as in the conventional example. That is, the voltage comparator 37 compares the output of the synthesizer 50 and the comparison level _eth2 , and if the output of the synthesizer 50 is smaller,
A signal indicating that the contents are the same is given, and a signal indicating that the contents do not match is given in other cases. The voltage comparator 36 is the combiner 4
When the output of eth 9 is higher than the comparison level eth ₁ , it gives a signal whose contents are the same, and otherwise it gives a signal whose contents are mismatched. eth ₁ and eth ₂ are approximately 1/2V _H < eth ₁ < V _H , It is set to an appropriate value in the range 0<eth ₂ <1/2V _H . Furthermore, if the contents of the two audio signals are different, even if one is delayed and compared, no correlation will be obtained, and if a sufficient integration period is considered, the outputs of the integrators 47 and 48 will be approximately 1/1 2V _H and has no effect on identity determination.

As described above, according to the present invention, even if there is a relatively large time difference between two audio signals having the same content, identity determination can be performed while sufficient audio signal components remain, and the determination accuracy is improved. It also has the effect of shortening the time required for determination.

In this example, for convenience of explanation, one shift register is connected to each of the two zero-cross detectors, but in addition to connecting many more shift registers, it is also possible to connect a shift register with taps at appropriate intervals. E- by using a shift register etc.
By using a correspondingly large number of OR circuits and integrators, it is possible to further widen the allowable range of the time difference between two audio signals, raise the cutoff frequency of the low-pass filter, and increase the number of audio signal components used for judgment. good.

[Brief explanation of drawings]

FIG. 1 is a block diagram of this type of radio receiver, FIG. 2 is a block diagram showing a conventional identity determiner, FIG. 3 is an explanatory diagram of the operation of the identity determiner, and FIG. 4 is an embodiment of the present invention. FIG. 2 is a block diagram showing an example. In the figure, 1 is an antenna, 2 is a distributor, 6 is a first receiving system, 10 is a second receiving system, 11 is an audio signal switch, 12 is a low frequency amplifier, 13 is a speaker, and 14 and 15 are electric fields. Detector, 16 is an identity determiner, 17 is a control device, 30, 31 are low pass filters, 32, 33 are zero cross detectors, 34, 4
5, 46 are exclusive OR circuits, 35, 47, 48
is an integrator, 38 and 39 are detectors, 40 and 41 are voltage comparators, and 42 and 43 are shift registers.
Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first and second receiving system configured to be able to automatically select stations independently of each other; means for detecting the receiving state of the receiving station selected by these two receiving systems and determining whether it is good or bad; An identity determiner that distinguishes between the output signals of the two receiving systems, and when the two receiving systems select a receiving station with the same content, the receiving station with the better reception condition is selected by one receiving system. The identity determination device includes two low-pass filters, two zero-cross detectors, and a control device that connects the output audio signal to the audio output circuit and shifts the other receiving system to an automatic tuning state. Two shift registers connected to each other or two sets of shift registers or two shift registers each having a plurality of output taps, an exclusive OR circuit connected to the above two zero cross detectors, and one input connected to the above zero cross detector. a plurality of exclusive OR circuits connected to one of the above and whose other input is given the output of the other zero cross detector delayed by the shift register; and a plurality of integrators connected to the plurality of exclusive OR circuits. When at least one integrator output exceeds the first determination level and at least one integrator output is lower than the second determination level, the content is determined to be the same. a means for giving a signal to the control device indicating that the content is different when the signal is not to be used; and a means connected to the two low-pass filters to detect the audio signal level of the low-pass filter output, and is effective when the level of the audio signal is higher than a predetermined judgment level. and means for providing a control device with a signal that invalidates the signal when the signal is not used.