JPH01222512A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To cancel the fluctuation of an input signal wave and to detect a signal wave with simple circuit constitution by devising the circuit such that a phase difference of an output signal of a 1st phase shift means and a 2nd phase shift means is 180 deg. and comparing the signal waves having a phase difference of 180 deg. by a comparator means. CONSTITUTION:A band pass filter 2 consists of a series connection of a high pass filter and a low pass filter. That is, the high pass filter consists of a capacitor C1 and a resistor R1 and the low pass filter comprises an amplifier 4, capacitors C2, C3 and resistors R3, R4. A phase shift comparator 3 is made up of an integration circuit 6, a differentiation circuit 7 and a comparator 8 comparing outputs of the integration circuit 6 and the differentiation circuit 7. After an input signal wave of the band pass filter 2 is given to the integration circuit 6 having a delay effect and the differentiation circuit 7 having a lead effect of 90 deg., the voltages of the signal wave are compared by the comparator 8. Thus, the fluctuation of the signal waveform is cancelled and the signal wave is detected with simple circuit constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a receiver that selectively receives a specific broadcasting station.
In particular, it is suitably implemented in a waveform shaping circuit of a radio receiver that extracts a region identification signal.

BACKGROUND ART In conventional traffic information broadcasts, emergency broadcasts, etc., a signal called a region identification signal is superimposed on a modulated signal in order to enable identification of a broadcast source or selective reception. Therefore, the broadcast source can be identified by detecting and identifying the area identification signal at the receiver. Furthermore, if the area identification signal is stored in the receiver, it can be automatically tuned to traffic information broadcasts and emergency broadcasts.

In order to detect the area identification signal superimposed on this modulated signal, a bandpass filter is required to extract the area identification signal. To construct this bandpass filter, it has conventionally been constructed using individual semiconductors such as transistors, operational amplifiers, and the like.

Problems to be Solved by the Invention The output from the detection circuit of the receiver includes area identification signals of foreign transmissions and noise, and these signals or noise may affect the signal waveform that should be extracted. I may receive it.

FIG. 5 is a timing chart for explaining problems when using a conventional waveform shaping circuit to generate an output signal from a detection circuit of a radio receiver. Figure 5 (1) shows the output signal waveform of the conventional waveform shaping circuit, and Figure 5 (2) shows the output signal waveform of the conventional waveform shaping circuit.
) The signal waveform Wll in FIG. 5 (1), which shows the pulse waveform when level-discriminating the signal waveform shown in FIG. The waveform level-discriminated by W10 is the pulse waveform PL'l in FIG. 5(2).
It is. Generally, since the area identification signal has a certain frequency, the pulse width time T11 after level discrimination does not vary with time.

However, if the area identification signal is affected by other area identification signals or noise, the level of the signal waveform will change, that is, signal fluctuation will occur, as shown in signal waveform W12 in FIG. 5(1).

Therefore, when the signal waveform W12 is level-discriminated at the discrimination level W10 shown in FIG. 5(1), the pulse width time T12 changes with time as shown in the pulse waveform P12 in FIG. 5(2).

If the pulse width time T12 fluctuates over time in this way, the result is equivalent to a change in the repetition frequency of the region identification signal, and there is a possibility that it will be difficult to reliably extract the region identification signal.

Therefore, by eliminating the influence of other area identification signals and noise,
In order to extract only the desired area identification signal, it is necessary to configure a bandpass filter with a narrow passband width. In order to configure such a bandpass filter with a narrow passband width, it is necessary to connect several filters in series, which generally results in a complicated circuit configuration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple waveform shaping circuit that is unaffected by signal waveform fluctuations, that is, unaffected by signal level fluctuations.

Means for Solving the Problems The present invention provides first phase shift means for shifting the phase of an input signal, second phase shift means, and outputs of the first phase shift means and second phase shift means. and comparing means for inputting and comparing the inputs, and using at least one of the first phase shifting means and the second phase shifting means, the phase is equal to 1 between each of these outputs.
This is a waveform shaping circuit characterized in that the waveforms are shifted by 80 degrees.

Operation In the present invention, the signals given to the first phase shift means and the second phase shift means have a 1.0 degree difference between their respective outputs.
A phase difference of 80 degrees is produced. The outputs of the first phase shift means and the second phase shift means are given to a comparison means and subjected to level discrimination.

Embodiment FIG. 1 is an electrical circuit diagram of a waveform shaping circuit which is an embodiment of the present invention, FIG. 2 is a diagram showing the frequency characteristics of the bandpass filter 2 of FIG. 1, and FIG. 3 is a diagram showing the traffic information area in Europe. It is a spectrum diagram of another signal.

In Europe, when broadcasting traffic information, a traffic information area identification signal is transmitted together with a carrier wave. FIG. 3 shows the spectrum of the traffic information area identification signal, and BK and DK in FIG. 3 are the names of the traffic information area identification signal. The BK double signal has a frequency of 50 Hz and 80 Hz, and the DK double signal has a frequency of 125 Hz. In this way, traffic information area identification signals in Europe use very close frequencies, so unless a band-pass filter with good selectivity is used, there is a risk of being influenced by other traffic information area identification signal waves. . For example, when extracting a DK multiplied signal as a traffic information area identification signal, if the frequency characteristic of the bandpass filter is reference mark S1 in Fig. 3, the BK multiplied signal will be included in the output of the bandpass filter, and the DK multiplied signal will be included in the output of the bandpass filter. This will affect signal level discrimination.

Hereinafter, an embodiment of the present invention for extracting the 125 Hz DK shown in FIG. 3 will be described.

The waveform shaping circuit 1 includes a passband filter 2 and a phase shift comparator 3. The band pass filter 2 is a well-known circuit, and is a filter for extracting a certain specific frequency.In the present invention, a 125 Hz DK
Circuit constants are determined for double signal extraction. The band pass filter 2 has a configuration in which a high pass filter and a low pass filter are connected in series. That is, a high-pass filter is configured by the capacitor C1 and the resistor R1, and a low-pass filter is configured by the amplifier 4, capacitors C2 and C3, and resistors R3 and R4.

An output signal from a detection circuit (not shown) of the receiver is applied to an input terminal 5 of a waveform shaping circuit, and a DK signal, which is a traffic information area identification signal, is extracted from the output of a bandpass filter 2.

The phase shift comparator 3 includes an integrating circuit 6 that delays the phase of the input signal wave and a differentiating circuit 7 that advances the phase of the input signal wave. It is composed of an integrating circuit 6 and a comparator 8 that compares the output values of the differentiating circuit 7. The output signal of the amplifier 4 is applied to an integrating circuit 6, which delays the phase of the input signal wave by 90 degrees, and then applies it to the positive input terminal of a comparator 8. Further, the output of the amplifier 4 is applied to a differentiating circuit 7, which advances the input signal wave by 90 degrees, and then applies it to the negative input terminal of a comparator 8.

The comparator 8 outputs a high level signal when the output voltage of the integrating circuit 6 is higher than the output voltage of the differentiating circuit 7, and outputs a low level signal when the output value of the differentiating circuit 7 is higher than the output value of the integrating circuit 6. Output. The output signal of comparator 8 is output from output terminal 9.

The circuit operation of the waveform shaping circuit 1 configured as above will be explained using the timing chart of FIG. 4. FIG. 4 is a timing chart showing signal waveforms at each part of the phase shift comparator 3. FIG. 4 (1) shows the output signal waveform of the bandpass filter 2, which shows the signal waveform on the signal line 11. The signal waveform W1 is a DK signal wave, and the signal waveform W1 is a DK signal wave, and it contains other area identification signals and noise existing in the vicinity of the DK signal wave. The effect is that the level of the signal wave fluctuates. The signal waveform W2 shown in FIG. 4(2) shows the output of the integrating circuit 6, that is, the signal waveform on the signal line 12.
The signal waveforms W1 and W2 have a phase difference of 90 degrees. The signal waveform W3 shown in FIG. 4(3) is the output of the differentiating circuit 7 and shows the signal waveform on the signal line 13. Since the differentiating circuit 7 has the effect of advancing the phase of the input signal wave by 90 degrees, Wl and W3, which are the input signal waves of the differentiating circuit 7, have a phase difference of 90 degrees. The comparator 8 corresponds to the signal waveform W2 shown in FIG.
The voltage values of the signal waveform W3 shown in 3) are compared, and if the voltage value applied to the positive input terminal is higher than the negative input voltage value, a high level signal is output onto the signal line 14. FIG. 4(4) shows the output voltage of the comparator 8, that is, the signal waveform on the signal line 14. Signal waveform W2. shown in FIG. 4(3). As can be seen from W3, when the voltage value of the signal waveform W2 is higher than the voltage value of the signal waveform W3, a high level signal waveform is output onto the signal line 14. As can be understood from the output signal waveform in FIG. 4 (4), the output signal waveform of the comparator 8 is not affected by the fluctuation of the signal waveform of the input signal of the phase shift comparator 3, that is, the bandpass filter The fluctuations in the output signal of No. 2 are canceled by the comparator 8 and do not appear in the output.The integration circuit 6 and the differentiation circuit 7 convert the signal waveform into 90
It only has the effect of delaying or advancing the phase, and the signal fluctuations in the signal waveform on the signal line 11 are also output to the signal lines 12 and 13.
Since they are input to the positive input terminal and the negative input terminal of the comparator 8 and compared, their fluctuations are canceled and are not output on the signal line 14. Therefore, as shown in FIG. 4 (4), the high level Time width Tl.

T2 will be almost the same.

FIG. 4(5) shows the output signal wave of the bandpass filter 2, that is, the output signal wave when the signal wave on the signal line 11 is level-discriminated using the threshold level Th. As can be seen from the signal waveform in FIG. 4(5), the signal wave in FIG. 4(1) has fluctuations, so the high level time width T3. T4 varies depending on fluctuations in the input signal wave.

As described above, in this embodiment, the bandpass filter 2
The output signal wave is given to an integrating circuit 6 having a 90 degree phase delay effect and a differentiating circuit 7 having a 90 degree phase advance effect, and then the voltage values of the signal waves are compared by a comparator 8, so that a bandpass filter is applied. Level discrimination can be performed by canceling the fluctuations in the signal waveform of the second output signal wave.

Effects of the Invention As described above, according to the present invention, the output signals of the first phase shift means and the second phase shift means are configured such that the phase difference between the output signals is 180 degrees, and a signal having a phase difference of 180 degrees is generated. Since the waves are compared by the comparison means, fluctuations in the input signal wave can be canceled out, and the signal wave can be detected with a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a waveform shaping circuit which is an embodiment of the present invention, Fig. 2 is a diagram showing the frequency characteristics of the bandpass filter 2 of Fig. 1, and Fig. 3 is a traffic information regional signal in Europe. FIG. 4 is a timing chart showing the signal waveforms of each part of the phase shift comparator 3, and FIG. 5 is a timing chart for explaining conventional waveform shaping. 1... Waveform shaping circuit, 2... Bandpass filter, 3
...Phase shift comparator, 6... Integrating circuit, 7
・・・Differential circuit agent Patent attorney Kei Saikyo Part 11 Shaping round yi 1st period 2nd figure Shuho Kei (Hz) □ 3rd figure Shu-7I number (Hz) Figure 5

Claims (1)

[Claims] First phase shifting means for shifting the phase of an input signal;
a second phase shift means; and a comparison means to which the outputs of the first phase shift means and the second phase shift means are inputted and compared; The phase is 1 between each of these outputs using at least one of the
A waveform shaping circuit characterized by being shifted by 80 degrees.