JPH02202726A - Telecasting exciter - Google Patents

Abstract

PURPOSE:To decrease the number of component parts to neglect the group delay time distortion and at the same time to reduce the distortion of a transmission waveform by modulating the amplitude at a VHF band and obtaining a remaining side band wave via a surface acoustic remaining side band filter to perform the amplification of electric power. CONSTITUTION:The video signal inputted to an input device of a video stage undergoes the modulation of amplitude via a VHF modulation circuit of a video modulation stage. This modulated wave passes through a surface acoustic wave remaining side band filter SAW VSBF. Thus a remaining side band wave is obtained. This wave undergoes the amplification of electric power via an amplifier circuit and is telecast. In this case, the modulation of amplitude is carried out at a VHF band and an SAW VSBF using the crystal of a small temperature coefficient as a piezoelectric material is applied. Thus it is possible to decrease the number of component parts for simplification of the constitution of an exciter and also to reduce the distortions caused by various types of parts. Furthermore the direct modulation is attained to prevent the occurrence of spuriousness and to neglect the generation of the group delay time distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a television broadcast exciter used in a VHF television broadcaster.

(Prior Art) Fig. 2 shows a block diagram of a conventional exciter for television broadcasting. Modulation is performed, and then this modulated wave passes through an intermediate frequency vestigial sideband filter (IFVSBF), and part of the lower sideband and upper sideband of the carrier frequency is sent to the next frequency converter, which converts it to a predetermined frequency. Converts and amplifies TV channel frequencies.

Generally, the frequency spectrum of an amplitude-modulated wave has a lower sideband and an upper sideband around the carrier frequency, as shown in FIG. However, in the case of television,
Since the video signal includes a wide frequency component ranging from DC to 4.5 M) Iz, amplitude modulation of this signal requires a wide transmission band of 9 M) Iz. However, in order to make effective use of limited radio waves, it is desirable to have a transmission band as narrow as possible if the purpose of transmitting video signals can be achieved, and for this reason, the vestigial sideband (VSB) transmission method has been proposed.
This vestigial sideband filter (VSBF) was proposed. Figure 4 shows the characteristics of this vsttp, and this VSBF
The spectrum passed through is shown in Figure 5.

This frequency converter converts a modulated wave modulated in an intermediate frequency band to a television frequency determined by the Radio Law, for example, 91.25 MHz. Since the output of this frequency conversion section is minute, the amplification section amplifies the minute power to a large power such as 10 kM or 50 kW.

(Problem B to be solved by the invention) In conventional systems of this type, modulation is performed in the intermediate frequency band, so it is only necessary to change the frequency of the local oscillator depending on the transmission channel, and processing in the intermediate frequency band is required. Therefore, it has advantages such as being technically easy to handle.
The drawbacks are that the deviation of the carrier frequency is affected by both the intermediate frequency oscillator and the local oscillation, the configuration is complicated, the number of parts increases, and the frequency of failures increases.

Additionally, since the intermediate frequency is converted into a transmission channel, there is also the drawback that spurious signals are produced.

The present invention was proposed to improve the above-mentioned disadvantages of a large number of parts and a high occurrence of distortion, and in particular to construct an exciter in which group delay time distortion can be ignored. An object of the present invention is to provide an exciter for a television broadcasting machine that enables transmission of small waveforms.

(Means for solving !Jiff) In order to achieve the above object, the present invention provides an input device to which a video signal is applied, and an output signal from the input device that converts the output signal into VHF.
a vHF modulation circuit that modulates the VHF band, a VHF band 0 surface acoustic wave vestigial sideband filter that passes the output signal from the VHF modulation circuit, and amplifies the output from the surface acoustic wave vestigial sideband filter. 1 is an exciter for television broadcasting characterized by comprising an amplifier section.

(Function) In the present invention, a video signal is amplitude-modulated in the VHF band, and the signal in the VHF band is passed through a surface acoustic wave vestigial sideband filter (SAW VSBF) to obtain a desired vestigial sideband, which is then amplified. Therefore, when performing amplitude modulation in the conventional intermediate frequency band, a frequency conversion section was required, but this can be removed in the present invention, so the configuration of the exciter can be simplified. can.

Furthermore, since the SAW VSBF is used to perform direct modulation in the VHF band, group delay time distortion can be ignored and spurious generation can be prevented.

(Example) Next, examples of the present invention will be described.

Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

FIG. 1(a) shows a block diagram of the exciter of the present invention.

In the present invention, first, a video signal is input to the input device, and the output signal from this input device is subjected to amplitude modulation in the VHF modulation circuit of the video modulation stage, and this modulated wave is a surface acoustic wave residual side wave. The system is characterized in that a residual sideband is obtained through a bandpass filter (SAHVSBF'), and the power of this is amplified through an amplifier circuit for broadcasting.

In other words, in the conventional method, amplitude modulation is performed in the intermediate frequency band,
The residual sideband of the intermediate frequency band is obtained through the intermediate frequency VSBF, and the frequency of this is converted to the desired television broadcasting frequency, and then power amplification is performed. The component parts used are as follows: Since the number of components is reduced, and therefore the number of component parts is reduced, distortions caused by the various component parts can be reduced.

Here, surface acoustic waves
Wave (hereinafter referred to as 5Ail) filter. To explain a little about the filter, there are two types of elastic waves: longitudinal waves (concentration waves) and transverse waves (waves whose vibration direction is perpendicular to the wave propagation direction). SV wave (Vertical 5hear w)
ave) and SH waves (Horizontal 5hear)
When looking at the propagation of a zero elastic wave with
Near the surface of a solid, waves exist that exhibit a different propagation mode than inside the solid due to the boundary condition called the surface. In other words, the wave reflected at the surface boundary generates a longitudinal wave component and a transverse wave component (SV wave) and propagates. In this way, longitudinal waves and transverse waves intertwine with each other and propagate near the surface. These waves are called surface waves. This wave is also called a Rayleigh wave, named after its discoverer.

An example of the structure of this filter is as shown in FIG.
When an ID electrode is formed on the surface of 031LINbOs and a voltage is applied through the ID electrode, a strain proportional to the electric field (
strain) and generate a surface acoustic wave (SAW) having a wavelength equal to the period λ of the ID electrode.

In the case of detection, the SIV filter detects the polarization displacement proportional to the strain of the piezoelectric material as a voltage by arranging the ID electrode's λ corresponding to the period of the propagating wave. It converts waves into electrical signals, and by changing the shape of the 10 electric waves used for this conversion, a filter with desired characteristics can be easily obtained.In the present invention, a filter using this SAW is used. It is something.

(Effects of the Invention) The present invention includes an input device to which a video signal is applied like a ridge, a VHF modulation circuit that modulates the output signal from the input device in the VOP band, and a VHF modulation circuit that modulates the output signal from the VHF modulation circuit. Since it is equipped with a 0 surface acoustic wave vestigial sideband filter for the VHF band to be passed through and an amplification section that amplifies the output from the surface acoustic wave vestigial sideband filter, amplitude modulation is performed in the V1 band and the surface acoustic wave Residual sideband filter (SAW VSB
F) generates a residual sideband and amplifies its power, which reduces the number of components used, and because the number of components is small, the distortion generated by various components can be reduced. has.

In addition, since SAW VSBF is used in the VHF band and direct modulation is possible, spurious signals do not occur as in the conventional case where IP is converted to a transmission channel, and the occurrence of group delay time distortion can be ignored. .

[Brief explanation of the drawing]

FIG. 1(a) is a block diagram of the exciter for television broadcasting of the present invention, FIG. 1(b) is a structural explanatory diagram of the surface acoustic wave vestigial sideband filter used in the present invention, and FIG. 2 is a conventional example. 3 is an explanatory diagram of conventional amplitude modulation, FIG. 4 is an explanatory diagram of a residual sideband filter, and FIG. 5 is an explanatory diagram of waves passing through an elastic wave filter. Figure 1 (a) (b) Figure 3 Figure 2 Figure 4 Figure 5 Procedural amendments Director General of the Japan Patent Office Yoshi 1) Tsuyoshi Moon 1. Indication of the case 1999 Patent Application No. 22428 2. Invention Name of TV broadcasting exciter 3, relationship with the case of the person making the amendment Patent groove name Nippon Tsushinki Co., Ltd. 4, Agent 160 Address 3-3-23-6 Nishi-Shinjuku, Shinjuku-ku, Tokyo, Amendment Contents (1): We will supplement the power of attorney as shown in the attached document. (2), from line 20 on page 1 of the specification to line 1 on page 2 of the same book, ``The output signal is a carrier wave and an intermediate frequency (I F
) is amplitude modulated," is corrected to "The output signal is amplitude modulated on the intermediate frequency carrier wave." (3) On page 8, line 20' of the same book, ``Figure 3 is the conventional'' has been corrected to ``Figure 3 is''.

Claims (1)

[Claims] An input device to which a video signal is applied, and a V that modulates the output signal from the input device in the VHF band.
an HF modulation circuit, and a VHF that passes the output signal from the VHF modulation circuit.
1. An exciter for television broadcasting, comprising: a surface acoustic wave vestigial sideband filter for band use; and an amplification section that amplifies an output from the surface acoustic wave vestigial sideband filter.