JPH0637726A - Frequency multiplexing system - Google Patents

Abstract

PURPOSE:To eliminate the need for provision of a guard band for each basic group subject to frequency multiplexing and to facilitate the configuration of a filter of the system. CONSTITUTION:When frequency multiplexing is applied to 1st basic groups A, C, B whose frequency band is fG1 and 2nd basic groups B, D, F whose frequency band is fG2 for each of plural channels, a frequency band of a frequency multiplex signal B' adjacent to a frequency multiplex signal C' whose frequency band is fG1 on which the basic groups are multiplexed as they are is converted into a frequency band f2-fG2, a frequency band of a frequency multiplex signal E' adjacent to a frequency multiplex signal D' whose frequency band is fG2 on which the basic groups are multiplexed as they are is converted into a frequency band f3-fG1, a frequency band of a frequency multiplex signal A' adjacent to the frequency multiplex signal B is converted into a frequency band f1-fG1, and a frequency band of a frequency multiplex signal F' adjacent to the frequency multiplex signal E is converted into a frequency band f4-fG2, where f1, f2, f3 and f4 are frequencies of local oscillators.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency multiplexing system in a multi-channel video transmission system.

[0002]

2. Description of the Related Art Conventionally, this type of frequency multiplexing system for multi-channel video signals has been frequency-modulated or amplitude-modulated in an intermediate frequency band, frequency-converted into a predetermined frequency band by a local oscillator, and frequency-multiplexed. A method for obtaining a signal, and
As shown in FIG. 2, the signal modulated in the intermediate frequency band is
First, the local oscillator specified for each of a plurality of channels, the frequency band f _G becomes the aggregate A, B, C, D, E, and frequency converted to F, further comprising a frequency band f _G the aggregate is directly multiplexed The frequency band of the frequency multiplexed signal C ′ and the frequency multiplexed signal B ′ adjacent to one of the frequency multiplexed signals C ′ is converted into f ₆ −f _G , and the frequency multiplexed signal D ′ adjacent to the other of the frequency multiplexed signal C ′. Is converted to f ₇ -f _G and the frequency multiplexed signal A ′ adjacent to the frequency multiplexed signal B ′ is converted.
Frequency band is converted to f ₅ -f _G and the frequency multiplexed signal D ′
Frequency band of the frequency division multiplexed signal E 'adjacent to the f ₈ -f _G
It is known that the frequency band of the frequency-multiplexed signal F ′ adjacent to the frequency-multiplexed signal E ′ is converted into f ₉ −f _G.

[0003]

Among the above-mentioned conventional frequency multiplexing systems, the former has a problem in that the same number of local oscillators as the number of multiple channels is required, and the latter has a large number of multiple channels. When the frequency band corresponding to the group is also used as a multiplex channel, the leakage of the basic group, which is the original signal, becomes a problem, and in the channel for frequency conversion to the frequency bands on both sides of the basic group, in order to suppress the leakage of the basic group, Since it is necessary to provide a steep filter, it may be difficult to realize a filter. Therefore, a guard band is provided for each group of basic groups, which is not suitable for high-density frequency multiplexing. There was a point.

An object of the present invention is to provide a filter structure easily without providing a guard band for each frequency-multiplexed basic group.

[0005]

In order to achieve the above object, the present invention divides a basic group into a first basic group and a second basic group, and converts the first basic group and the second basic group into frequency multiplexed signals. When converting, the frequency-multiplexed signal obtained from the first basic group and the second
This is an arrangement in which frequency-multiplexed signals obtained from the basic group are alternately arranged.

[0006]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In this embodiment, the frequency band f is set for each of a plurality of channels.
_G1 first basic group A, C, E, and frequency band f _G2 second
Aggregates B, D, and frequency-multiplexed into two basic groups of F, frequency division multiplexed signal comprising a frequency band f _G1 the aggregate is directly multiplexed C of 'the frequency division multiplexed signal D comprising a frequency band f _G2',
The band 'frequency division multiplexed signal B' adjacent frequency division multiplexed signal C is converted into f ₂ -f _G2, the frequency band of the 'frequency division multiplexed signal E' adjacent frequency division multiplexed signal D is converted into f ₃ -f _G1 and, the frequency band of the 'frequency division multiplexed signal a' adjacent frequency division multiplexed signal B is converted into f ₁ -f _G1, the frequency band of the 'frequency division multiplexed signal F which is adjacent to the' frequency-multiplexed signal E f ₄ -
Convert to f _G2 . Where f ₁ , f ₂ , f ₃ , and f
₄ is the frequency of the local oscillator. As a result, when the first basic group A, C, E which is the frequency band f _G1 before frequency conversion and the second basic group B, D, F which is the frequency band f _G2 before frequency conversion are converted into frequency multiplexed signals, Frequency multiplexed signals A ', C', E'obtained from the first basic group A, C, E and frequency multiplexed signals B ', D', obtained from the second basic group B, D, F
It means that F'is arranged alternately.

[0008]

As described above, according to the present invention, the basic group is divided into the first basic group and the second basic group, and when the first basic group and the second basic group are converted into frequency-multiplexed signals, Since the frequency-multiplexed signal obtained from the basic group and the frequency-multiplexed signal obtained from the second basic group are alternately arranged, it becomes easy to construct a filter for eliminating the leakage of the frequency-multiplexed signal, and the multi-channel high density It is possible to obtain the effect of being suitable for the frequency multiplexing method.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional frequency multiplexing system.

[Explanation of symbols]

A, C, E First fundamental group B, D, F Second fundamental group f ₁ , f ₂ , f ₃ , f ₄ Local oscillator frequencies A ', B', C ', D', E ', F' Frequency multiplexed signal

Claims (2)

[Claims] 1. A basic group is divided into a first basic group and a second basic group,
When the first basic group and the second basic group are converted into frequency multiplexed signals, the frequency multiplexed signals obtained from the first basic group and the frequency multiplexed signals obtained from the second basic group are alternately arranged. Frequency multiplexing method. 2. The basic group is divided into a first basic group and a second basic group,
When the first basic group is converted into the frequency multiplexed signal, the frequency multiplexed signals obtained from the first basic group are arranged so as not to be adjacent to each other, and when the second basic group is converted into the frequency multiplexed signal, the second basic group is also used. The frequency multiplexing method is characterized in that the frequency multiplexing signals obtained from the above are arranged so as not to be adjacent to each other.