JPH03278633A - Vsb-am communication system and its sender receiver side equipment - Google Patents

Abstract

PURPOSE:To attain effective use of a frequency band by multiplexing 2nd and 3rd modulation signals on almost the same band width as a low frequency band to which DSB-AM of a 1st modulation signal is applied. CONSTITUTION:Modulated signals Y2, Y3 by modulation circuits 2, 3 are synthesized by a synthesis circuit 4, subject to amplitude limit by an inverse Nyquist filter 5, the result is multiplexed on the modulated signal Y1 from a modulation circuit 1 by a multiplex circuit 6, subject to band limit at a band pass filter circuit 7 to be a VSB-AM system multiplex television signal. That is, a signal at a residual side band (VSB) including all bands of the upper side band and part of band of the lower side band is generated as the modulated signal Y1 (NTSC television signal) and a signal at double side bands (DSB) including all the upper and lower side bands is generated as the modulated signals Y2, Y3 (additional signals). Thus, additional information such as a wide aspect signal is multiplexed on the NTSC television signal and effective use of the frequency band is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a VSB-AMi11 communication system commonly used in television broadcasting systems and a receiving side device for the above system.

(Prior Art) For F and DTV signal systems that are compatible with the NTSC standard system, various methods have been proposed for multiplexing additional signals such as wide screen signals and high-frequency components of brightness signals onto existing NTSC signals. .

As a typical example of such a multiplexing method, the orthogonal components of the video carrier wave are amplitude-demodulated using additional signals, and
An orthogonal two-phase modulation method that is multiplexed onto a TSC signal has been proposed. For details of this orthogonal two-phase modulation method, please refer to
Inoue et al.'s paper titled ``Study of wide screen EDTV system'' published in the Technical Report of the Television Society of Japan on August 25, 1983, and ``Television Please refer to the invention by Yasugi et al. titled ``High Definition Signal Generating Device''.

(Problem B to be Solved by the Invention) The problem to be solved by the present invention is to further multiplex an additional signal based on a new principle to the multiplexed television signal based on the conventional orthogonal two-phase modulation method. The object of the present invention is to realize a VSB-AM communication system and its transmitting/receiving side equipment that makes more effective use of the frequency band.

(Means for Solving the Problems) According to the VSB-AM communication system of the present invention and its transmitting/receiving side transmission for solving the above problems, the transmitting side device amplitude-modulates the carrier wave with a first modulation signal and performs upper and lower a first modulating means for creating a first modulated signal including sidebands; and a first modulating means for generating a first modulated signal including a sideband;
a second modulating means for generating a second modulated signal including upper and lower sidebands by amplitude modulating a second modulating signal having a narrower band than the modulating signal; a third modulating means for generating a third modulated signal by performing amplitude modulation with a narrow band third modulating signal and combining the upper and lower sidebands so as to have opposite polarities; an inverse Nyquist filter that limits the amplitude of the third modulated signal; the first modulated signal and the second modulated signal whose amplitude is limited by the inverse Nyquist filter; If the carrier wave is not included in any of the third modulated signals, the carrier wave is included in the first modulated signal. a synthesizing means for synthesizing the second and third modulated signals, and before and after the synthesizing means, the entire band of one sideband and a part of the band of the other sideband for the first modulated signal; Bandwidth limiting to limit the band so that the second and third modulated signals, which are narrow band amplitude limited, become a VSB format signal including a DSB format signal that includes both side bands. and means for transmitting the combined and band-limited signal as a multiplexed signal.

On the other hand, the receiving side device includes a carrier wave regenerating means for regenerating a carrier wave included in the received multiplexed signal, and a first modulated signal for regenerating the first modulated signal by synchronously detecting the multiplexed signal using the regenerated carrier wave. demodulating means; a second demodulating means for regenerating the second modulated signal by synchronously detecting the multiplexed signal with an orthogonal regenerated carrier wave whose phase is shifted by 90 degrees from the regenerated carrier wave; Each signal band including the upper and lower sidebands of the modulated signal is synchronously detected using the regenerated carrier wave and synthesized so that they have opposite polarities, and unnecessary frequency components are removed from this synthesized signal to reproduce a third modulated signal. A third demodulation means is used.

Furthermore, according to another embodiment in which the VSB-AM communication method is combined with an orthogonal two-phase modulation method, a fourth signal that amplitude modulates a carrier wave that is out of phase with the carrier wave by 90 degrees is added as an additional signal. .

That is, according to the VSB-AM communication system and its transmitting/receiving side device of the present invention, the second modulated signal is distributed in a bandwidth that is almost the same as the lower band of the first modulated signal to which DSB-AM is applied. It is now possible to multiplex the third and fourth modulation signals, making it possible to multiplex the third and fourth modulation signals.
The signal band can be used more effectively than the B-AM communication method or the orthogonal two-phase VSB-AM communication method.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 shows VSB-AM communication 4 according to an embodiment of the present invention.
12 is a block diagram showing the configuration of a transmitting side device that is compatible with three methods; FIG. I3 is the first. Second. The input terminals for the third modulation signals X+, Xz, and X3, ■, the input terminal for the carrier wave C0, 1 the first modulation circuit, 2 the second modulation circuit, 3 the third modulation circuit, and 4 the synthesis circuit. circuit, 5 is an inverse Nyquist filter, 6 is a multiplexing circuit, 7 is a band pass filter circuit, 8 is an RF converter, 9 is an antenna, 0. is an output terminal for multiplexed television signals.

The transmitting device in FIG. 1 is exemplified as a multiplexed television signal transmitting device that multiplexes an NTSC standard television signal with an additional signal such as a wide aspect signal of a narrower band and transmits the resulting signal. .

That is, input terminal 1. the first modulated signal X supplied to
Reference numeral 1 denotes a baseband NTSC television signal consisting of a luminance signal Y and a carrier chrominance signal multiplexed on its high frequency portion by frequency interleaving. Further, input terminals I2 and 13 are supplied with additional signals such as a wide aspect signal to be multiplexed to the NTSC television signal, and a second modulation signal X2 and a third modulation signal having a narrower band than the first modulation signal X1. It is supplied as signal X3. Further, an intermediate frequency carrier wave (IF carrier) of the NTSC television signal is supplied to the input terminal I4 as a carrier wave C0.

Carrier wave C0 supplied to input terminal ■4 and input terminal 1+
, Iz, Iz. The angular frequencies of the second and third modulation signals XI, Xz, and X:+ are ω in the same order. ,ω1
．． ω2. ω3, and the carrier wave Co and the first . Second. The third modulation signal x,,X,.

If the peak level of any of X is normalized to "1", it can be written as co2CO5ωot X+ = cos+u+, tX, = cosω2t X, = cosω3t.

In the first modulation circuit 1, a carrier wave C8 is amplitude-modulated in a carrier wave sending format using a first modulation signal X1, and a first modulated signal Y including a carrier wave C8 and upper and lower side band waves around the carrier wave C8 is created. Ru. Note that for convenience of explanation, the modulation index is assumed to be "1".

That is, l −X + Co + 06 = COSω1L “ COSω, 1 = 1/2
[cos(Co +ω+)t +cos(ω,
−ω+)1) 10COSω. t・
...(1) As shown in FIG. 2(A), the frequency spectrum of the first modulated signal Y is the upper and lower sidebands of the carrier wave C6 and X and C, which are distributed symmetrically on both sides of the carrier wave C6. It is composed of. Although illustrations are omitted to avoid complication,
The high frequency portion of each sideband of the modulated signal Y is composed of the high frequency component of the luminance signal and the carrier color signal.

Further, the second modulated signal Y2 by the second modulation circuit 2 is expressed as follows: 2 = 1/2 (cos ((ω.+ωz)t
+π/2)+ cos ((ω.-C2)t +π/
2)]・(2) becomes.

The frequency spectrum of this second modulated signal Y2 is
As illustrated in Figure (B), the upper and lower side bands of XzCo are the carrier wave frequency ω. It is symmetrically distributed around /2π.

Furthermore, in one amplitude modulation circuit 3a of the third modulation circuit 3, the carrier wave C is generated by the third modulation signal X3.

is amplitude modulated. Further, in the other amplitude modulation circuit 3b, the carrier wave -00 having an opposite phase is amplitude-modulated by the third modulation signal X3. This opposite phase carrier wave -00 is created by passing the carrier wave C0 on the input terminal I4 through the 180° phase shift circuit 3C.

The upper sideband of X3Co contained in the output of the amplitude modulation circuit 3a is extracted by the bandpass filtering circuit 3d, and the lower sideband contained in the output -X:lCO of the amplitude modulation circuit 3b is extracted by the bandpass filtering circuit 3e. A third modulated signal Y3 is created by combining the extracted signals in a combining circuit 3f.

That is, 3 = (X3 Co))l + (X3 Co
) t= 1/2 (cos(ω.+ω3) is 10 cos
(ω.-C3)t)u1/2 (cos(ω.+ω3)
t + cos (ω.-ωx) t) t= 1/
2 (cos(ω.+ω3)t-cos(ω.-ω,)
t]・・・・・(3) However, the symbols []8 and [] mean that only the upper and lower sideband waves within [] are extracted, respectively. Furthermore, it is assumed that the extracted upper and lower sidebands do not include the carrier wave itself.

The frequency spectrum of this third modulated signal Y is
As illustrated in Figure (C), the positive phase upper sideband CoX5 and the opposite phase lower sideband -COX3 have a carrier wave frequency ω. /2
It is distributed symmetrically around π.

Second. The third modulated signals Y2 and Y3 are combined by a combining circuit 4, subjected to amplitude limitation by an inverse Nyquist filter 5, and then multiplexed into the first modulated signal Y1 by a multiplexing circuit 6. A multiplexed television signal Z having a frequency spectrum as shown in FIG. 2(D) is created.

That is, =YI +Y, +Y3 = 1/2 (cos(ω0 + ω + )
t + cos (ω. −ω ,)t ]+
1/2 (cos ((ω0 +ωz)t +π
/2)+cos((ω0-ωz)t 1π/2)]+
1/2 (cos(ω. 10ω,)t-cos(ω.-
ω3)t]+cos ωot ・ ・ ・ ・ (4) This multiplexed television signal Z is passed through the bandpass filter circuit 7
By subjecting the signal to band restriction, a VSB-AM multiplexed television signal as shown in FIG. 2(E) is obtained.

That is, for the modulated signal Y+ (N'rsc television signal), a vestigial sideband (VSB) signal including the entire upper sideband and a part of the lower sideband is generated, and the modulated For the signals Y2 and Y3 (multiplexed signals), a double sideband (DSB) signal including the entire upper and lower sidebands is generated. The VSB format NTSC television signal is
It can be considered that the low frequency portion of the DSB method and the high frequency portion of the single sideband (SSB) method are combined.

Therefore, the multiplexed television signal shown in FIG.
It can be considered in eight parts.

For this example, the modulated signals Y, , Y2 and Y,
It will be explained based on mathematical formulas how the signals are multiplexed by the transmitting device and how they are demultiplexed by the receiving device. Therefore, in the following equations, the modulated signal Y, the modulated signal Y2. Note the multiplexed part with Y3, ie the low frequency part of the DSB scheme.

Here, the multiplexed signal Z is decomposed into a carrier wave C0, an upper sideband [Z) on both sides thereof, and a lower sideband (z)L, so that Z=Co'' (Z)H+(Z)L・... (
5), then (Z) K = 1/2 (cos(ω.+ω+)t +cos((
ω. +ωz)t+π/2) +cos (ω.+ω
, )t]・ ・ ・ ・ (6) (Zl L = 1/2 (cos(ω.−ω+)t +cos
((ω.-ωz)t+π/2)-co direct ω. -ω3)t
] ・ ・ ・ ・ The following relationship (7) is obtained.

The multiplexed television signal in FIG. 2(E) is frequency-converted in the RF converter 8 and transmitted to the receiving device by being radiated from the antenna 9 or sent out on a cable from the output terminal oI. be done.

In a receiving device such as a television receiver, a multiplexed television signal in an RF band received by an antenna or the like is converted into a multiplexed television signal Z in an intermediate frequency band in a tuner. This multiplexed television signal Z in the intermediate frequency band is subjected to amplitude limitation by the Nyquist filter and becomes a multiplexed television signal with a frequency spectrum as shown in FIG. 3. In this frequency spectrum, the second. Third
The modulated signals Yz and Yy are subjected to amplitude limitations with slopes opposite to each other by the inverse Nyquist filter on the transmitting side and the Nyquist filter on the receiving side, thereby receiving a comprehensive amplitude limitation symmetrical around the carrier wave C0. . Note that this arrangement of signal frequencies is inverted as a result of down-conversion in the tuner.

An intermediate frequency carrier wave C0 is regenerated from the intermediate frequency band multiplexed television signal shown in FIG. 3, and the first . Second. third modulation signals X+, X2;

Demodulation of X3 is performed.

FIG. 4 is a block diagram showing the configuration of the demodulation device on the reception side, where 1 is an input terminal for the multiplexed television signal Z, 11 is a first demodulation circuit, 12 is a second demodulation circuit, 13
is the third demodulation circuit, 14 is the carrier regeneration circuit, and 15 is 90
'Phase shift circuit, 0□ is the output terminal of the regenerated first modulation signal X1, 03 is the output terminal of the regenerated second modulation signal X2, and 04 is the output of the regenerated third modulation signal X. It is a terminal.

In the carrier wave regeneration circuit 14, a carrier wave C0 is regenerated from the multiplexed television signal Z supplied to the input terminal I.

This carrier regeneration circuit 14 has a phase-off loop (PLL).
) circuit, tank circuit, etc.

In the synchronous detection circuit 11a of the first demodulation circuit 11, the multiplexed television signal Z is synchronously detected (product detection, product demodulation) using the reproduced carrier wave C0. The high-frequency component and DC component of this detection output are removed by the low-pass filter circuit 11b, thereby reproducing only the first modulated signal X1. In this synchronous detection, the reproduced output of the second modulated signal Y2, which is multiplied by the orthogonal reproduced carrier wave whose phase is shifted by 90' from that during modulation, becomes zero. Further, regarding the third modulated signal Y3, the upper and lower sidebands cancel each other out, so that the reproduced output becomes zero.

In other words, X! = (Z Co ) t = (Y+ Co + Ys Co + C
o ”) t・ ・ ・ ・ (8) (8) Calculating each term in 2 yields Y, c.

= (cos(C0+ω+)t-cosω, 1+co
s (ω.−ω+)t, −cos ω. t)=1/
2 (2cos ω, t+cos(2ωo +ω,)i
+cos(2ω.-ω+)1 (9) Y:lC.

= (cos(C0+ωx)t −cos ωo
tcos (C0-C3) t 0cos ωat
)=1/2 Ccos(2ω.+ωi)t+co
s (2ω.-C1)t (10) C0 1/2 [1+ cos 2ω. t] (11).

Here, ω. 〉〉ω8. ω, ・ ・ ・ ・ (12
), then cos(2ω) in equations (8) to (1).

+ω+)t, cos(2ω.-ω+)t, cos(
2ω. +ω:+)t, cos(2ω0-ω:+)t
, cos2ωat are all removed as harmonic components.

Furthermore, since the DC component in equation (11) is also removed, (
From equations 8) to (11), the following equations can be obtained:

This is nothing but a demodulated NTSC television signal (first modulated signal X+) modulated, transmitted, and received according to the VSB-AM communication method by synchronous detection of the reproduced carrier wave C0.

On the other hand, in the second demodulation circuit 12, during synchronous detection by the synchronous detection circuit 12a, the first modulated signal Y1, which is multiplied by the orthogonal recovered carrier wave whose phase is shifted by 90 degrees during modulation, is multiplied by the third modulated signal Y1. Both reproduction outputs of the modulated signal Yj become zero. Therefore, the high-frequency component and DC component of this synchronous detection output are removed by the low-pass filter circuit 12b, thereby reproducing only the second modulated signal x2.

Further, in the third demodulation circuit 13, the bandpass filter circuit 13
The upper sideband (Z)a and the lower sideband (z)L of the multiplexed television signal Z are extracted by a and 13b, respectively. Regarding the extracted upper sideband, the synchronous detection circuit 13c
At this point, synchronous detection is performed using the regenerated carrier wave C0. Furthermore, regarding the extracted lower sideband, the synchronous detection circuit 13
At d, synchronous detection is performed using the recovered carrier wave -00 of opposite phase. This reverse phase recovered carrier wave -00 is obtained by passing the recovered carrier wave C0 through the 180° phase shift circuit 13e.

During synchronous detection by the synchronous detection circuits I3c and 13d, the reproduced output of the modulated signal Y2, which is multiplied by a reproduced carrier wave whose phase is shifted by 90 degrees from that during modulation, becomes zero. Further, regarding the modulated signal Y1, the synchronous detection outputs of the upper and lower sidebands cancel each other out during subtraction by the subtraction circuit 13f, so that the reproduced output becomes zero. Therefore, the detection outputs output from the synchronous detection circuits 13c and 13d are subtracted by the subtraction circuit 13f, and the high-frequency components and DC components included in this subtraction output are removed by the low-pass filter circuit 13g, thereby performing the third modulation. Only signal X3 is reproduced.

That is, 3 [(Z))l Co -[2)L Co)L・
・ ・ ・ (l 4) If you calculate each term in equation (14), (Z), C.

= 1/2 [cos(ω.+ωυt −cosωa
t+ (os (ω.+ω3)t −cosω.t)
= 1/4 (cos(2ωo +ω+)t + co
sω, t+ cos (2ω0+ω:+)t + co
sω, 1) − (Z) L c.

-1/2 (-cos(ω.-ω+)1+ cos
(ω0-ω3)t = 1/4 (-cos(2ω.-ω+)1+co
s(2ω.-ω3)t (15) COSωot cosωot) -cosω, 1 + cosω3t] ・ ・ ・ ・ (16) From equations (14) to (16), X3 ”' CO3ωsj ・ ・ ・ ・ (17) , only x3, which is equal to the third modulated signal X3, is demodulated.

In the transmitting side device illustrated in FIG. 1, the amplitude modulation circuit 3a,
3b may be constituted by a carrier suppression double-side band modulation circuit such as a ring modulator. Note that the amplitude modulation circuits 3a and 3b may be configured with a carrier wave sending double-side band modulation circuit such as a well-known collector modulation circuit or a base modulation circuit, and the carrier wave may be removed by a subsequent band-pass filter circuit 3d or 3e. . The amplitude modulation circuits 1, 2a, 3a, and 3b can also be realized by analog multiplication circuits using operational amplifiers.

Furthermore, the synchronous detection circuit 11a of the receiving side device shown in FIG.
, 12a, 13c, and 13d, a synchronous detection circuit having a configuration as described on page 150 of "NHK Television Technology Textbook [Part 1], published by Japan Broadcasting Publishing Association" can be used. Alternatively, these synchronous detection circuits may be realized by analog multiplication circuits using operational amplifiers. Furthermore, a multiplication circuit for amplitude modulation or synchronous detection can be constructed by a combination of an A/D conversion circuit, a digital multiplication circuit, and a D/A conversion circuit.

In this way, (i) normal VSB in the first modulation section of the transmitting device;
The modulated signal X1 that has received -AM is subjected to normal synchronous detection in the first demodulation section of the receiving device, thereby adding the signal components of each sideband and reproducing it.

(ii) The third modulated signal x 3, in which sidebands on opposite sides are combined after undergoing amplitude modulation with carrier waves of opposite phase in the third modulation section of the transmitting side device, is By undergoing normal synchronous detection in the demodulator, the signal components of each sideband are canceled out and eliminated.

(iii) Normal VSB in the first modulation section of the transmitting device
-The modulated signal X+ that has received the AM is synthesized after each of the upper and lower sidebands undergoes synchronous detection using a carrier wave with an opposite phase in the third demodulator of the receiving device, and the signal of each sideband is then synthesized. The components are canceled out and eliminated.

(iv) The third modulated signal In the demodulation section, the upper and lower sidebands are subjected to synchronous detection using carrier waves having opposite phases, and then synthesized, whereby the signal components of each sideband are added and reproduced.

(v) 1st. Unlike the third modulated signals X, X3, the second modulated signal X2 is modulated and demodulated using an orthogonal carrier wave whose phase is shifted by 90 degrees.
The signal is reproduced without being affected by the third modulation signals X+ and Xt.

Therefore, the combination of the vertical relationship of the sidebands and the positive/inverse relationship of the carrier wave phase can be reversed from that in FIG. 1.

FIG. 5 is a block diagram showing the configuration of a transmitting side device applying the VSB-AM communication method according to another embodiment of the present invention,
II++ 'It + I+! + 1 + 4 are respectively the 1st. Second. Third. Fourth modulation signal X+, XzX3
．． Input terminal of X-, 115 is input terminal of carrier wave C0, 2
1 is a first modulation circuit, 22 is a second modulation circuit, 23 is a third modulation circuit, 24 is a second modulation circuit, 25 is a synthesis circuit, 26 is an inverse Nyquist filter, 27 is a multiplexing circuit, 2
8 is a band pass filter circuit, 29 is an RF converter, 30 is a transmitting antenna, and 011 is an output terminal.

1st. The second modulation circuits 21, 22 respectively correspond to the first . Corresponds to the second modulation circuit 1°2,
Modulated signals Y, , Y with frequency spectra illustrated in FIGS. 2(A) and 2(B), respectively.

generate. Further, the third modulation circuit 23 corresponds to the third modulation circuit 3 in the transmitting side device in FIG.
A modulated signal Y having a frequency spectrum illustrated in is generated. However, this third modulation circuit 23 amplitude modulates the carrier wave C0 with the third modulation signal X3.
), the upper and lower sidebands are extracted from the bandpass filter circuit 23b23c), and the extracted sidebands are subtracted from each other (subtraction circuit 23d) to generate the third modulated signal Y3. . As a result, carrier waves having opposite phases are amplitude-modulated by the third modulation signal X, and the upper and lower sidebands are extracted from each and added.
It realizes the same function as the third modulation circuit 3 in FIG. 1 which generates the modulated signal Y.

Furthermore, in this embodiment, an amplitude modulation circuit 24a) amplitude-modulates an orthogonal carrier wave shifted by about 90 degrees from the carrier wave C0 with a fourth modulation signal X4, and a bandpass filter circuit 23b extracts upper and lower sidebands from this. , 23c), a fourth modulation circuit 24 is added that generates a fourth modulated signal ¥4 by subtracting the extracted sidebands (subtraction circuit 23d).

This fourth amplitude modulation circuit 24 is similar to the third amplitude modulation circuit 2
3, the bandpass filter circuits 23b and 23C and the subtraction circuit 23d are shared between the amplitude modulation circuit 23 and the subtraction circuit 23d.
A combining circuit 24b for combining the outputs of a and 24a is added.

The first modulation circuit 21 is supplied with a first modulation signal XI (NTSC television signal) on an input terminal III and an intermediate frequency carrier wave C0 on an input terminal 115.

The carrier wave C0 is amplitude-modulated by the first modulation signal X+, becomes a modulated signal Y, and is supplied to one input terminal of the multiplexing circuit 26.

The amplitude modulation circuit 22a of the second modulation circuit 22 is supplied with an additional signal such as a wide aspect signal from an input terminal r+z as a second modulation signal X2, and an input terminal J
An intermediate frequency orthogonal carrier wave is supplied from I5 through a 90° phase shift circuit 22b. The output of the amplitude modulation circuit 22a is the second
is supplied to one input terminal of the combining circuit 25 as the modulated signal Y2.

In the amplitude modulation circuit 23a of the third modulation circuit 23, the carrier wave Ca is amplitude-modulated with the third modulation signal X. The upper sideband (X) included in this modulated signal.

C0]8 is extracted by the bandpass filter circuit 23b, and the lower sideband Cx3C,)□ is extracted by the bandpass filter circuit 23c. In the subtraction circuit 23d, the upper sideband (X3 C
o) s to lower sideband (X: +C.

] 1 is subtracted, and the third modulated signal Y3 = (X3C(
+)□−(X3Co)L is created.

On the other hand, the fourth modulation circuit 24 receives an additional signal such as the remaining part of the wide aspect signal from the input terminal 114.
is supplied as a modulated signal X, and an orthogonal carrier wave is supplied from the 90-degree phase shift circuit 22b. Amplitude modulation circuit 2
4a, the orthogonal carrier C0 is amplitude modulated with a fourth modulation signal X4. The upper sideband (Xn
Co]*+ is extracted by the bandpass filter circuit 23b, and the lower sideband (X4C6)L is extracted by the bandpass filter circuit 23b.
Extracted in 3c. In the subtraction circuit 23d, the upper sideband (X
The lower sideband (XaCo)t is subtracted from 4Co)s,
Fourth modulated signal Ya = (X4 CO) - (X4 .C0).

・　・　・　・　・(18) is created.

Second. Third. Fourth modulated signal Yz, Y3, Y
a is synthesized by a synthesis circuit 25 and subjected to amplitude limitation by an inverse Nyquist filter 26. The modulated signals Yz, Y3 . Ya is multiplexed with the modulated signal Y1 in the multiplexing circuit 27, subjected to band restriction as a multiplexed television signal in the bandpass filtering circuit 28, becomes a multiplexed television signal Z, frequency-converted in the RF converter 29, and transmitted to the antenna. The signal is transmitted to the receiving device by being radiated from 30 or transmitted onto a cable from output terminal 011.

FIG. 6 shows a first . Second. Third. Fourth modulation signal X+
, Xz , X:l , and X4. FIG.

In FIG. 6, III is an input terminal for the multiplexed television signal Z received and converted into an intermediate frequency band, 31 is a first demodulation circuit, 32 is a second demodulation circuit, 33 is a third demodulation circuit, 34 is a fourth demodulation circuit, 35 is a carrier wave regeneration circuit, 36 is a 90° phase shift circuit, OZl+Ozz+02
3, Oza is the demodulated 1st, 2nd, . Third. Fourth modulation signals x, , X2 . X-co.

This is the output terminal of X4.

In the carrier wave regeneration circuit 35, an intermediate frequency carrier wave C0 is regenerated from the multiplexed television signal Z supplied to the input terminal rz+. This reproduced carrier wave C0 is the first. 90° phase shift circuit 36
After that, the second
demodulation circuit 32 and a fourth demodulation circuit 34.

In the synchronous detection circuit 31a of the first demodulation circuit 31, the multiplexed television signal Z is synchronously detected (multiplicative product detection, product demodulation) using the reproduced carrier wave C0, and the high-frequency components and DC components of this detection output are converted into low-frequency components. The first modulated signal x is demodulated by being extracted by the pass filter circuit 31b. During this demodulation, the reproduced output of the modulated signals Y2 and Y4 becomes zero based on the principle of orthogonal two-phase modulation and demodulation. Also, (8)
As already explained with respect to equations (12) to (12), with respect to the modulated signal Y2, signal components in both sidebands having opposite polarities are cancelled, and the reproduced output thereof becomes zero. In this manner, the first demodulation circuit 31 reproduces the NTSC television signal as the first modulated signal Xl, and supplies it from the output terminal 0□ to a subsequent signal processing circuit such as a Y/C separation circuit.

In addition, in the second demodulation circuit 32, when the synchronous detection circuit 32a performs synchronous detection, the reproduced outputs of the first modulated signal Y1 and the third modulated signal ¥3 both become zero due to the principle of orthogonal two-phase modulation and demodulation. . Further, regarding the fourth modulated signal Y4, the detected signals of the upper and lower sidebands cancel each other out, so that the reproduced output becomes zero. Therefore, the high-frequency component and DC component of the synchronous detection output are removed by the low-pass filter circuit 32b, so that only the second modulated signal x2 is reproduced.

On the other hand, in the third demodulation circuit 33, the bandpass filter circuit 33
a and 33b, respectively, extract the upper sideband (z)+4 and lower sideband (z)L of the multiplexed television signal Z. The extracted upper sideband [Z) and I are subjected to synchronous detection using the reproduced carrier wave C0 in the synchronous detection circuit 33C. Furthermore, for the extracted lower sideband (2) L, the synchronous detection circuit 33d generates a recovered carrier C0.
synchronous detection is performed. In the subtraction circuit 33e, the detection output of the synchronous detection circuit 33d is subtracted from the detection output of the synchronous detection circuit 33C. The high frequency component and DC component included in this subtracted output are removed by the low pass filter circuit 33f, thereby reproducing the third modulated signal X3.

As described above, when demodulating the third modulated signal X3, the signal components of both sidebands of the first modulated signal Y are canceled out and disappear.

Furthermore, when demodulating the third modulated signal This is clear from the principle of the modulation method. In this way, in the third demodulation circuit 33, the third modulation signal X3
Only the signal is demodulated and supplied as an additional signal such as a wide aspect signal from the output terminal 0□ to a subsequent signal processing circuit.

Furthermore, in the fourth demodulation circuit 34, the third demodulation circuit 33
The upper sideband of the multiplexed television signal Z [Z] is
8 and the lower sideband (z)L are extracted. The extracted upper sideband [Z) 8 is subjected to synchronous detection using the regenerated orthogonal carrier wave Co in the synchronous detection circuit 34c. Furthermore, the extracted lower sideband [Z)L is subjected to synchronous detection using the reproduced orthogonal carrier C0 in the synchronous detection circuit 34d. In the subtraction circuit 34e, the detection output of the synchronous detection circuit 34d is subtracted from the detection output of the synchronous detection circuit 33c. The high-frequency component and DC component included in this subtracted output are removed by the low-pass filter circuit 34f, so that only the fourth modulated signal X is reproduced.

When demodulating this fourth modulated signal X4, the phase of the carrier wave for the first and third modulated signals Y, , Y is shifted by 90 degrees from that during modulation, so the reproduced signal component becomes zero.
This is clear from the principle of orthogonal two-phase modulation. Also, the second
Regarding the modulated signal Yz, the detected signals of the upper and lower sidebands cancel each other out and disappear during subtraction by the subtracting circuit 34e, so that its reproduced output becomes zero. In this way, in the fourth demodulation circuit 34, the fourth modulation signal x4
Only the signal is demodulated and output as an additional signal such as a wide aspect signal from the output terminal 0□4 to a subsequent signal processing circuit or the like.

(Effects of the Invention) Since the VSB-AM communication system of the present invention has the above-described configuration, it is possible to use the NT
Additional information such as wide aspect signals can be multiplexed onto SC television signals and the like, making effective use of frequency bands possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a transmitting device that uses the VSB-AM communication system according to an embodiment of the present invention, and FIG. NT
The second modulated signal y+ is added to the SC television signal (first modulated signal y+).
．． The second modulated signal Y, generated by the third modulation circuit,
FIG. 3 is a conceptual diagram illustrating an example of the frequency spectrum of a multiplexed television signal obtained by multiplexing Y, FIG. From the multiplexed television signal, the first . Second. A block diagram showing the configuration of the receiving side device that demodulates the third modulated signal, and FIGS. 5 and 6 show the configuration of the transmitting side device and the receiving side to which the VSB-AM communication system of another embodiment of the present invention is applied. FIG. 2 is a block diagram showing the configuration of the device. I+, T++...input terminal of first modulation signal X1, I
z, I+z...input terminal of second modulation signal X2, L,
I+, . . . input terminal for third modulation signal X3, II4.
. . . input terminal for the fourth modulation signal X4, I4. IIS...
- Input terminal of carrier wave C0, 1°21...first modulation circuit, 2,22...second modulation circuit, 3.23...third modulation circuit, 526...inverse Nyquist filter ,6
．． 27... Multiplexing circuit, 11.31... First demodulating circuit, 12.32... Second demodulating circuit, 13.33...
. . . third demodulation circuit, 34 . . . fourth demodulation circuit. Figure 2 Figure 2 Figure 2

Claims (10)

[Claims] (1) On the transmitting side, a first modulating means for amplitude modulating a carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands, and a first modulating means that is 90 degrees out of phase with the carrier wave. The orthogonal carrier wave is
a second modulating means for generating a second modulated signal including upper and lower sidebands by amplitude modulating a second modulating signal having a narrower band than the modulating signal; a third modulating means for generating a third modulated signal by amplitude modulating the upper and lower sidebands with a narrowband third modulation signal and combining the upper and lower sidebands so as to have opposite polarities; an inverse Nyquist filter that limits the amplitude of the modulated signal of No. 3; and the carrier wave is included in both the first modulated signal and the second and third modulated signals whose amplitudes are limited by the inverse Nyquist filter. If not, a combining means for combining the first, second, and third modulated signals while including the carrier wave, and a combining means for combining the first, second, and third modulated signals while including the carrier wave, and one sideband for the first modulated signal before and after this combining means. For the second and third modulated signals, which are narrowband amplitude-limited to be VSB-format signals that include the entire band and a part of the other sideband, DSB that includes all of the both sidebands is used. a band-limiting means for limiting the band so that the signal becomes a signal of the same format, and a means for transmitting the synthesized and band-limited signal as a multiplexed signal, and the receiving side is provided with a means for transmitting the combined and band-limited signal as a multiplexed signal. carrier wave reproducing means for regenerating the included carrier wave; first demodulating means for synchronously detecting the multiplexed signal using the regenerated carrier wave to regenerate the first modulated signal;
a second demodulating means for reproducing the second modulated signal by synchronously detecting the multiplexed signal using an orthogonal regenerated carrier wave shifted by 0°;
Each signal band including upper and lower sidebands of the third modulated signal in the multiplexed signal is synchronously detected using the regenerated carrier wave and combined so that they have opposite polarities, and unnecessary frequency components are removed from this combined signal. a third modulated signal that reproduces the third modulated signal;
A VSB-AM communication system characterized by comprising demodulation means. (2) a first modulating means for amplitude modulating a carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands; 1
a second modulating means for generating a second modulated signal including upper and lower sidebands by amplitude modulating a second modulating signal having a narrower band than the modulating signal; a third modulating means for generating a third modulated signal by amplitude modulating the upper and lower sidebands with a narrowband third modulation signal and combining the upper and lower sidebands so as to have opposite polarities; an inverse Nyquist filter that limits the amplitude of the modulated signal of No. 3; and the carrier wave is included in both the first modulated signal and the second and third modulated signals whose amplitudes are limited by the inverse Nyquist filter. If not, a combining means for combining the first, second, and third modulated signals while including the carrier wave, and a combining means for combining the first, second, and third modulated signals while including the carrier wave, and one sideband for the first modulated signal before and after this combining means. For the second and third modulated signals, which are narrowband amplitude-limited to be VSB-format signals that include the entire band and a part of the other sideband, DSB that includes all of the both sidebands is used. 1. A transmission side device for VSB-AM communication system, characterized in that it is equipped with a band limiting means for limiting the band so that the signal becomes a signal of the same format, and a means for transmitting the combined and band limited signal as a multiplexed signal. . (3) The third modulation means includes one amplitude modulation circuit that amplitude modulates the carrier wave with the third modulation signal, and an amplitude modulation circuit that modulates the amplitude of the carrier wave with the third modulation signal; the other amplitude modulation circuit that modulates; one signal extraction circuit that extracts one of the upper and lower sidebands included in the output of the one amplitude modulation circuit; and the upper and lower sidebands included in the output of the other amplitude modulation circuit. The VSB-AM communication system according to claim 2, characterized in that the VSB-AM communication system is provided with a signal extraction circuit for extracting the other side of the band, and an addition circuit for adding the signals extracted by these signal extraction circuits. sending device. (4) The third modulation means includes an amplitude modulation circuit that amplitude modulates the carrier wave with the third modulation signal, and one filter that extracts one of the upper and lower sidebands included in the output of the amplitude modulation circuit. circuit, another filter circuit that extracts the other of the upper and lower sidebands included in the output of the amplitude modulation circuit, and a subtraction circuit that subtracts the signals extracted by each of these filter circuits. A transmission side device for a VSB-AM communication system according to claim 2. (5) means for receiving a multiplexed signal transmitted in accordance with the VSB-AM communication system as set forth in claim 1; and carrier wave reproducing means for regenerating a carrier included in the received multiplexed signal. , a first demodulating means for synchronously detecting the multiplexed signal using the regenerated carrier wave to regenerate the first modulated signal; and synchronizing the multiplexed signal using an orthogonal regenerated carrier wave whose phase is shifted by 90 degrees from the regenerated carrier wave. a second demodulating means for detecting and reproducing the second modulated signal; and a second demodulating means for detecting and reproducing the second modulated signal;
Each signal band including the upper and lower sidebands of the modulated signal of
A receiving side device of a VSB-AM communication system, characterized in that it is equipped with a third demodulating means for reproducing a modulated signal of the VSB-AM communication system. (6) The third demodulation means includes one filtering circuit that extracts one of the upper and lower sidebands of the received multiplexed signal, and another filtering circuit that extracts the other of the upper and lower sidebands of the received multiplexed signal. circuit, one synchronous detection circuit that synchronously detects the signal extracted by the one filtering circuit with the regenerated carrier wave, and a synchronous detection circuit that synchronously detects the signal extracted by the other filtering circuit with a carrier wave having the same frequency and an opposite phase as the regenerated carrier wave. A VSB according to claim 5, characterized in that the VSB is provided with the other synchronous detection circuit that performs synchronous detection with the synchronous detection circuit, and an addition circuit that adds the outputs of these synchronous detection circuits.
- Receiving side device of AM communication system. (7) The third demodulation means includes one filtering circuit that extracts one of the upper and lower sidebands of the received multiplexed signal, and another filtering circuit that extracts the other of the upper and lower sidebands of the received multiplexed signal. a circuit, one synchronous detection circuit that synchronously detects the signal extracted by the one filtering circuit with the regenerated carrier wave, and another synchronous detection circuit that synchronously detects the signal extracted by the other filtering circuit with the regenerated carrier wave. and a subtraction circuit for subtracting the outputs of these synchronous detection circuits.
- Receiving side device of AM communication system. (8) On the transmitting side, a first modulating means that amplitude-modulates the carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands, and a first modulating means that is out of phase with the carrier wave by 90 degrees. The orthogonal carrier wave is
a second modulating means for generating a second modulated signal including upper and lower sidebands by amplitude modulating a second modulating signal having a narrower band than the modulating signal; a third modulating means for generating a third modulated signal by amplitude modulating the amplitude with a narrow band third modulating signal and combining the upper and lower sidebands so as to have opposite polarities; A fourth modulated signal is obtained by amplitude modulating the phase-shifted carrier wave with a fourth modulating signal having a narrower band than the first modulating signal, and combining the upper and lower sidebands so that they have opposite polarities. an inverse Nyquist filter that limits the amplitude of the second, third, and fourth modulated signals; and a second modulated signal whose amplitude is limited by the first modulated signal and the inverse Nyquist filter. , a combining means for combining the first, second, third and fourth modulated signals while including the carrier wave if none of the third and fourth modulated signals includes the carrier wave; , before and after this combining means, the first modulated signal is a VSB format signal including the entire band of one sideband and a part of the band of the other sideband, and has a narrow band amplitude. band limiting means for limiting the bands of the limited second, third and fourth modulated signals so that they become DSB format signals including all of both sidebands; and means for transmitting the multiplexed signal as a multiplexed signal, and the receiving side includes carrier wave regeneration means for regenerating a carrier included in the received multiplexed signal, and synchronously detecting the multiplexed signal with the regenerated carrier wave and transmitting the multiplexed signal. a first demodulating means for reproducing the first modulated signal; and a second demodulating means for reproducing the second modulated signal by synchronously detecting the multiplexed signal using an orthogonal regenerated carrier wave whose phase is shifted by 90 degrees from the regenerated carrier wave.
demodulating means, and each signal band including the upper and lower sidebands of the third modulated signal in the multiplexed signal is synchronously detected by the regenerated carrier wave and synthesized so that the polarities are opposite to each other, and the synthesized signal is a third demodulating means for reproducing the third modulated signal by removing unnecessary frequency components from the signal; and a third demodulating means for reproducing the third modulated signal by removing unnecessary frequency components from the signal; and fourth demodulation means for synchronously detecting orthogonal regenerated carrier waves, synthesizing them so that they have opposite polarities, and removing unnecessary frequency components from the synthesized signal to reproduce the fourth modulated signal. VSB-AM communication method. (9) a first modulation means that amplitude-modulates the carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands;
The second carrier wave is an orthogonal carrier wave whose phase is shifted by 90 degrees from the carrier wave.
a second modulating means for generating a second modulated signal including upper and lower sidebands by amplitude modulating a second modulating signal having a narrower band than the modulating signal; a third modulating means for generating a third modulated signal by amplitude modulating the amplitude with a narrow band third modulating signal and combining the upper and lower sidebands so as to have opposite polarities; A fourth modulated signal is obtained by amplitude modulating the phase-shifted carrier wave with a fourth modulating signal having a narrower band than the first modulating signal, and combining the upper and lower sidebands so that they have opposite polarities. an inverse Nyquist filter that limits the amplitude of the second, third, and fourth modulated signals; and a second modulated signal whose amplitude is limited by the first modulated signal and the inverse Nyquist filter. , a combining means for combining the first, second, third and fourth modulated signals while including the carrier wave if none of the third and fourth modulated signals includes the carrier wave; , before and after this combining means, the first modulated signal is a VSB format signal including the entire band of one sideband and a part of the band of the other sideband, and has a narrow band amplitude. band limiting means for limiting the bands of the limited second, third and fourth modulated signals so that they become DSB format signals including all of both sidebands; 1. A transmitting side device of a VSB-AM communication system, comprising means for transmitting a multiplexed signal. (10) means for receiving a multiplexed signal sent out according to the VSB-AM communication system as set forth in claim 8; carrier wave regeneration means for regenerating the carrier wave included in the received multiplexed signal; a first demodulating means for synchronously detecting the multiplexed signal using a regenerated carrier wave to regenerate the first modulated signal; and synchronously detecting the multiplexed signal using an orthogonal regenerated carrier wave whose phase is shifted by 90 degrees from the regenerated carrier wave. a second demodulating means for reproducing the second modulated signal; and a second demodulating means for reproducing the second modulated signal;
Each signal band including the upper and lower sidebands of the modulated signal of
a third demodulating means for reproducing a modulated signal; and synchronously detecting each signal band including upper and lower sidebands of the fourth modulated signal in the multiplexed signal with the orthogonal regenerated carrier wave so that the signals have opposite polarities. and a fourth demodulating means for reproducing the fourth modulated signal by removing unnecessary frequency components from the combined signal and reproducing the fourth modulated signal.
Receiving side device of M communication method.