JPS604388A - Picture signal transmitting device - Google Patents

Abstract

PURPOSE:To transmit two analog picture signals through conventional one radio channel by transmitting a carrier after frequency-modulating the carrier with the 1st analog picture signal and further amplitue-modulating it with the 2nd analog picture signal. CONSTITUTION:The 1st analog picture signal supplied to a terminal 1 frequency- modulates a carrier by a frequency modulator FM. The output of the frequency modulator FM is further amplitude-modulated for about 50% with the 2nd analog picture signal supplied from another terminal 2 at an amplitude modulator AM. Then this modulated wave is mixed with the output wave of a transmitting local oscillator T-LOC at a frequency converter CON and radiated outside through an antenna ANT-1. At the receiving side, the mixed waves become the frequency-modulated component only by means of an amplitude limiter LIM and the 1st analog picture signal is regenerated by a frequency discriminator DISC which demodulates the frequency modulated component and, at the same time, only the 2nd analog signal is detected and outputted by means of an amplitude detector DET.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an image signal transmission device, and more particularly to an image signal transmission device that improves the transmission efficiency of analog image signals.

(b) Prior Art and Problems There are analog modulation methods and digital modulation methods for transmitting image signals. The former is divided into amplitude modulation method and frequency modulation method.

Amplitude modulation methods include double sideband modulation (DSB), single sideband modulation (SSB), and vestigial sideband modulation (VSB). A waveband modulation (VSB) method is mainly used.

On the other hand, although the frequency modulation method requires a wider transmission band than the amplitude modulation method, it is used for microwave band transmission because it is resistant to interference in the transmission path.

Furthermore, digital modulation systems are inherently more resistant to interference than analog modulation systems, but have a wider transmission band.

However, it is possible to compress bandwidth and is seen as promising for long-distance lines.

As mentioned above, there are various modulation methods, but when relaying an analog image signal (for example, a television signal), the frequency modulation method is used, and only one television signal is transmitted per wireless channel, and the effective frequency of the transmission band is There were problems in terms of usage.

(c) Purpose of the Invention The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide an image signal transmission device that can effectively utilize the transmission band when transmitting analog image signals. It is said that

(d) Structure of the Invention The object of the invention is to provide a frequency modulator that frequency modulates a carrier wave with a first analog image signal, an amplitude modulator that amplitude modulates the output of the frequency modulator with a second analog image signal. an image signal transmission device@modulating section, a means for dividing the received wave modulated in frequency and amplitude into two, and a first and second received wave obtained by the dividing means are added to a demodulator and a detector; This is achieved by providing an image signal transmission device characterized in that it includes an image signal transmission device demodulation unit comprising means for extracting first and second analog image signals from received waves using a demodulator and a detector.

(e) Embodiment of the Invention Fig. 1 is a block connection diagram of an embodiment of the invention, in which Fig. 1(a) shows a transmitting section of an image transmission device, and Fig. 1(b) shows a receiving section of an image signal transmission device. show.

In the figure, FM is a frequency modulator, AM is an amplitude modulator, and CON
is the frequency converter, T-LOC is the transmitting local oscillator, MIX
is a mixer, R-LOG is a receiving local oscillator, AMP
&'i band amplifier with offshore transducer, LIM is amplitude limiter, DI
SC is a frequency discriminator, DET is a detector, RJ-1 and A
NT-2 is an antenna, and 1 to 4 are terminals, respectively.

Among these blocks, the image signal transmission device/transmission section shown in FIG. 1(a) is connected as follows.

The input terminal of the frequency modulator FM is terminal 1, and the output terminal is the amplitude modulator AM and the frequency converter CON'i=via the antenna A.
Connected to NT-1. The terminal 2 is connected to the (2) input terminal of the amplitude modulator M, and the transmitting local oscillator T-LOC is connected to the (2) input terminal of the frequency converter CON.

On the other hand, the image transmission device receiving section shown in FIG. 1(b) is connected as follows.

The input terminal of the mixer MIX is connected to the air @ANT-2, (2)
The input terminal is connected to the receiving local oscillator R-LOC, and the output terminal is connected to the input terminal of the amplifier AMP with band F wave amplifier. The output terminal (1) of the amplifier AMP is connected to the terminal 3 via the amplitude limiter LIM and the frequency discriminator DISC, and the output terminal (2) is connected to the terminal 4 via the detector DET. ing.

Next, the operation of the image signal transmission apparatus connected in this way will be explained in N81, which is performed from the transmitter shown in FIG. 1(a).

The first analog image signal applied to terminal 1 is applied to the frequency modulator FM, which frequency modulates the carrier wave that is the output from the carrier wave generation circuit (not shown) included therein, and further modulates the frequency of the carrier wave that is the output from the carrier wave generation circuit (not shown) included in the frequency modulator FM. The output is amplitude modulated by an amplitude modulator AM by about 50 degrees according to the second analog image signal supplied from the terminal 2.

Then, this modulated wave is mixed with the output wave of the transmitting local oscillator T-LOC in the frequency converter CON, converted to a predetermined frequency and level, and then radiated to the outside from the antenna ANT-1. ) indicates the receiving section of the image signal transmission device 〇 The modulated wave received by the antenna ANT-2 is mixed with the output wave of the receiving local oscillator R-LOC in the mixer MIX, converted into an intermediate frequency component, and is converted into an intermediate frequency component. After being amplified to the required level by the amplifier with door amplifier AMP, it is divided into two parts, and the first output is removed by the amplitude limiter LIM to remove the amplitude modulation component, leaving only the frequency modulation component. The discriminator DISC demodulates and reproduces the first analog image signal. On the other hand, the second output is applied to the detector DET to detect the amplitude modulation component. Since this method does not have a detection effect on frequency modulated components, the first analog image signal is not detected, and only the amplitude modulated second analog image signal is detected.

The reason why the first and second analog image signals can be separated in this way is that the frequency modulation is related only to the frequency shift and does not affect the amplitude. On the other hand, the amplitude 1j modulation utilizes the fact that it does not depend on the frequency of the carrier wave to transmit an analog image signal through two channels.

However, in the present invention, the signal-to-noise ratio of the first analog image signal deteriorates in a portion where the amplitude due to amplitude modulation is smaller than the amplitude due to frequency modulation (for example, a portion of a horizontal synchronization signal), but this influence is minimized. If the horizontal synchronization signals of the first and second analog image signals are synchronized to limit the range to a narrow range, the image signal will hardly be affected only in the vicinity of this signal.

Furthermore, it is possible to average the signal-to-noise ratio of the frequency modulated wave by inverting the polarity of the second analog image signal line by line.

(f) Detailed Description of the Invention According to the present invention, the carrier wave is frequency-modulated with the first analog image signal and then amplitude-modulated with the second analog image signal, and the receiving side receives this modulated wave. The original image signal can be reproduced by dividing it into two parts and passing them through a frequency discriminator and a wave detector.
It is possible to transmit two analog image signals to a wireless channel, and effective use of frequencies can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram of an embodiment of the present invention, in which FIG. 1(a) is a transmitting section of an image transmission device, FIG. 1(b) is an image diagram, FM is a frequency modulator, and AM is an amplitude. Modulator, C0NI-
1: Frequency converter, T-LOCI transmitting local oscillator, M
IX is a mixer, R-LOG is a receiving local oscillator, A M
P is a band amplifier with offshore transducer, LIM is an amplitude limiter, DIS
C is a frequency discriminator, DET is a detector, Shou-1 and ANT
-2 indicates an antenna, and 1 to 4 indicate terminals, respectively.

Claims (1)

[Claims] an image signal transmission device modulation section comprising a frequency modulator that frequency modulates a carrier wave with a first analog image signal, and an amplitude modulator that amplitude modulates the output of the frequency modulator with a second analog image signal; The frequency and amplitude modulated received wave is
a means for dividing the first and second parts obtained by the dividing means;
an image signal transmission device demodulating section comprising a demodulator and a detector, and means for extracting the first and second analog image signals from the received waves by the demodulator and detector; Features of the image signal transmission device.