JPH03283779A - Signal processing circuit - Google Patents

Abstract

PURPOSE:To process plural kinds of signals for plural base band transmission systems while using one modulator or demodulator in common by varying a parameter relating to an input signal when a base band transmission system of the input signal is detected. CONSTITUTION:A signal demodulated by a demodulation section 10 via a filter section 9 is inputted to a transmission system detection section 12, in which a base band transmission system is detected. The information is inputted to an additional signal generating section 13 having a same characteristic as that of an additional signal generating section 5 and to an AFC section 14 having a same characteristic as that of an AFC section 7 to control an additional signal and an AFC respectively. An additional signal from the additional signal generating section 13 controlled by a signal from the transmission system detection section 12 is synthesized with an output signal of a delay circuit section 11 retarding a demodulation signal in a timing difference at an inverted polarity at a signal subtraction section 15, from which an output base band signal is obtained. Thus, plural kinds of signals are processed by only one, e.g. modulator in common.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to signal processing circuits such as modulators and demodulators, and particularly to signal processing circuits that can share the processing of multiple types of signals using multiple baseband transmission methods. Regarding processing circuits.

] Summary of the Invention J This invention detects a baseband transmission method from an input signal, and changes parameters such as pre-emphasis, additional signals such as spread signals, AFC (automatic frequency control method), and modulation degree based on this. This makes it possible to process multiple types of signals related to multiple baseband transmission systems by sharing one modulator or demodulator, for example.

Note that this summary is provided solely for the purpose of quickly accessing the technical content of the present invention, and does not have any influence on the technical scope of the present invention or the interpretation of rights.

1 Conventional technology l Conventionally, in this type of modulator and demodulator, when the baseband transmission method is different, a modulator and demodulator for each transmission method are used, and switching is performed at the input and output of the modulator and demodulator. Alternatively, modules for each transmission method were built into the modulator and demodulator, and the input and output of these could be switched.

[Problem to be Solved by the Invention 1] Generally, when devices or modules are switched and used, signal interruption due to the switching and reliability deterioration due to the changeover switch occur, and additional equipment is required for each transmission method. Therefore, when modulating and demodulating multiple transmission methods,
Conventionally, the drawbacks were that the system became enormous and its reliability deteriorated.

An object of the present invention is to provide a signal processing circuit that solves these problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a detection means for detecting a baseband transmission method of an input signal, and a means for changing parameters related to the input signal based on the detection result of the detection means. It is characterized by having the following.

[Function 1] According to the present invention, the baseband transmission method is detected from the input signal, and based on this, parameters such as pre-emphasis, additional signals such as spread signals, AFC (automatic frequency control method), modulation degree, etc. are changed. As a result, multiple types of signals related to multiple baseband transmission systems can be processed using one modulator or demodulator in common.

[Example 1 Next, embodiments of the present invention will be described with reference to the drawings.

An example of the configuration of a modulator according to the present invention is shown in FIG. 1, and an example of the configuration of a demodulator is shown in FIG. Moreover, the modulator according to the present invention can be used as an NTS
FIG. 3 shows an example of application to a C/MUSE signal common digital FM modulator.

As shown in FIG. 1, in the modulator of the present invention, an input signal is input to a delay circuit section 1, then passed through a signal addition section 8, inputted to a modulation section 2, and then passed through a filter section 3 for output modulation. Output as a wave signal (main route). The transmission method detection unit 4 detects the baseband transmission method from the input signal. Additional signal generator 5. Modulation degree adjustment section 6. The AFC section 7 is
It is controlled by the transmission method detection section 4.

Note that the solid lines in the figure indicate the flow of signals, and the broken lines indicate the flow of control (the same applies to FIGS. 2 and 3).

Next, the operation will be explained. First, the information detected from the input signal in the transmission method detection section 4 is transmitted to the additional signal generator 5, such as a spread signal. Modulation degree adjustment section 6 that adjusts the modulation degree. Controls the AFC section 7 that controls the carrier frequency. Of these, the signal output from the additional signal generator 5 is synthesized by the signal adder 8 with a signal obtained by delaying the input signal by a timing difference by the delay circuit 1. This composite signal is input to the modulation section 2 where it is adjusted to a predetermined modulation degree and carrier frequency by the modulation degree adjustment section 6 and the AFC section 7. The output signal from the modulation section 2 is outputted as an output modulated wave signal through a filter section 3 that removes spurious and limits the transmission bandwidth. Further, the input signal is input to the AFC section 7, where the carrier frequency is controlled based on the information on the transmission method and the signal level.

In FIG. 2, which shows an example of the demodulator of the present invention, an input signal passes through a filter section 9 that removes out-of-band signals, is demodulated by a demodulation section 10 that performs demodulation, and is passed through a delay circuit section 11 and a signal subtraction section 15. (main route). The transmission method detection section 12 detects the transmission method from the signal demodulated by the demodulation section 10. 13 is an additional signal generating section, and 14 is an AFC section.

The signal demodulated by the demodulation section 10 via the filter section 9 is input to the transmission method detection section 12, where the baseband transmission method is detected. This information is input to an additional signal generating section 13 having the same characteristics as the additional signal generating section 5 shown in FIG. 1, and an AFC section 14 having the same characteristics as the AFC section 7 shown in FIG. Control each.

The additional signal from the additional signal generating section 13 controlled by the signal from the transmission method detecting section 12 is combined in the signal subtracting section 15 with the polarity reversed from the output signal of the delay circuit section 11 that delays the demodulated signal by the timing difference. and get the output bass punt signal.

Further, the demodulated signal from the demodulating section 10 is input to the AFC section 14, and the center frequency of the demodulating section 10 is controlled based on the information on the transmission system and the level of this demodulated signal.

Next, the operation of FIG. 3 showing an embodiment in which the modulator according to the present invention is applied to a digital FM modulator for NTSC/MUSE signals will be described.

In this modulator, an input signal is input to a delay circuit section 16, passes through a signal addition section 22, is FM-modulated by a DDS (direct digital synthesizer) 17, and is FM-modulated by a DDS (direct digital synthesizer) 17.
Spurious is removed by PF (band pass filter) 18, and the band is limited and output (main route)
. Reference numeral 19 denotes an NTC3/MUSE detection unit that detects whether the input signal is an NTSC system or a MUSE system, and the spread signal ROM 2G and the AFC unit 21 are controlled by this detection information.

As the input signal, a digital signal such as PCM is used, but in the case of an analog signal, an A/D converter is used before this.

NTSC/M detects the transmission method from the input digital signal
The USE detection unit 19 detects differences in data transmission speeds, synchronization signals, etc., and determines whether the system is an NTSC system or a MUSE system. Based on this judgment information, the spread signal ROM 20 stores the spread signal for the NTSC system (for example, 15Hz), the M
A spread signal (for example, 30 Hz) for the USE system is generated. These nine signals are sent to the delay circuit section 1 that corrects the timing.
6 and the signal addition section 22.

On the other hand, in the AFC section 21, the NTSC/MUSE detection section 1
The carrier frequency of the DDS 17 is controlled by the judgment information from 9. For this frequency control, for example, a digital vCO
For example, the reference frequency in the phase conversion function of the DDS 17 is changed using a digital voltage controlled oscillator (digital voltage controlled oscillator).

In the DDS17 where each parameter is controlled in this way,
FM modulated wave data obtained by sin-converting the amount of phase rotation corresponding to the level value of the input signal is D/A converted and an FM modulated wave is output. Spurious and out-of-band components generated by the DDS 17 are removed by the BPF 18.

Effects of the Invention 1 As explained above, according to the present invention, there is no signal switching of the main route in the modulator or demodulator, for example, and each parameter can be controlled from the same module even if the transmission method changes. The device can be made smaller and its reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a configuration example of a modulator according to the present invention, FIG. 2 is a diagram showing a configuration example of a demodulator according to the present invention, and FIG. 3 is a diagram showing a configuration example of a demodulator according to the present invention. It is a figure which shows the example applied to a container. 4...Transmission signal detection unit, 5...Additional signal generation unit, 6...Modulation degree adjustment unit, 7...AFC unit. Patent applicant Japan Broadcasting Corporation

Claims (1)

[Claims] 1) A signal processing circuit comprising: a detection means for detecting a baseband transmission method of an input signal; and means for changing a parameter regarding the input signal based on a detection result of the detection means.