JPH03268525A - Vsb-am communication system and its transmitting/ receiving side equipment - Google Patents

Abstract

PURPOSE:To multiplex additional information such as a wide aspect signal by restricting a band so that a modulated signal obtained by modulating the amplitude of a carrier by the 1st modulation signal becomes a VSB type signal and the 2nd modulated signal obtained by restricting the amplitude of a narrow band becomes a DSB type signal including the whole both side wave bands. CONSTITUTION:An additional signal such as a wide aspect signal to be multiplexed with an NTSC television(TV) signal is supplied to an input terminal I2 as the 2nd modulation signal X2 whose band is narrower than that of the 1st modulation signal X1. An upper side wave band included in the output of an amplitude modulation circuit 2a and extracted by a band pass filter (BPF) circuit 2d and a lower side wave band included in the output of an amplitude modulation circuit 2b and extracted by a BPF circuit 2e are synthesized with each other by a synthesizing circuit 2f to form the 2nd modulated signal Y2. The 2nd signal Y2 is restricted at its amplitude by an inverse Nyquist filter 2g and then multiplexed with the 1st modulated signal Y1 by a multiplexing circuit 3 to generate a multiplexed TV signal Z.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a VSB-AM communication system applied to a television broadcasting system, etc., and its transmitting/receiving side apparatus.

(Prior Art) Various methods have been proposed for multiplexing additional signals such as a wide screen signal and a high frequency component of a luminance signal onto an existing NTSC signal in an EDTV signal system having a standard system configuration.

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 to be Solved by the Invention) The problem to be solved by the present invention is to develop a VSB-AM communication system that is capable of multiplexing additional signals based on a new principle that is completely different from the conventional orthogonal two-phase modulation method. The objective is to realize the transmitting and receiving side devices.

(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 modulates the amplitude of the carrier wave with the first modulation signal and performs upper and lower a first modulating means for creating a first modulated signal including sidebands; and amplitude modulating the carrier wave with a second modulation signal having a narrower band than the first modulation signal to generate upper and lower sidebands, respectively. A second modulated signal is synthesized so as to have opposite polarities to create a second modulated signal.
a modulation means, an inverse Nyquist filter that limits the amplitude of this second modulated signal, and the carrier wave is not included in either the first modulated signal or the amplitude-limited second modulated signal. a synthesizing means for synthesizing the first and second modulated signals while including the carrier wave;
Regarding the modulated signal, the second modulated signal is a VSB format 〇 signal that includes the entire band of one sideband and a part of the band of the other sideband, and the second modulated signal is narrow band amplitude limited. is equipped with band limiting means for limiting the band so that it becomes a DSB format signal including all of both sidebands, and means for transmitting the combined and band limited signal as a multiplexed signal.

On the other hand, the receiving side includes carrier wave reproducing means for regenerating a carrier 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, and each signal band including the upper and lower sidebands of the second modulated signal in the multiplexed signal is synchronously detected using a regenerated carrier wave and synthesized so that they have opposite polarities, and unnecessary frequencies are extracted from this synthesized signal. and second demodulation means for removing the component and reproducing the second modulated signal.

According to another embodiment in which the above VSB-AM communication system is combined with an orthogonal two-phase modulation system, a third signal that amplitude-modulates a carrier wave whose phase is shifted by 90 degrees from the above-mentioned carrier wave 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 DSB-A of the first modulated signal
A second band with approximately the same bandwidth as the lower band to which M is applied.
．． It is possible to multiplex the third modulation signal, and it is possible to multiplex the third modulation signal.
- Effective use of signal band is realized compared to AM communication system.

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

(Embodiment) FIG. 1 is a block diagram showing the configuration of a transmitting side device applying a VSB-AM communication system according to an embodiment of the present invention, where Il and I2 are the first and second modulated signals, respectively. X...
Input terminal of X, ■, input terminal of carrier wave C0, 1 is the first modulation circuit, 2 is the second modulation circuit, 3 is the multiplexing circuit,
4 band-pass filter circuits, 5 an RF converter, 6 an antenna, and ol 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, the first modulated signal X supplied to the input terminal I
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, an additional signal such as a wide aspect signal to be multiplexed with the NTSC television signal is supplied to the input terminal I2 as a second modulation signal x2 having a narrower band than the first modulation signal X. Furthermore, the intermediate frequency carrier wave (IF carrier) of the NTSC television signal is connected to the input terminal I3.
Supplied as 0.

Carrier wave c0 supplied to input terminal I, and input terminal It
, Iz. The angular frequencies of the second modulation signals X+ and Xz are changed to ω0. ω1. ω2, and the carrier wave C0 and the first . If the peak level of both of the second modulation signals X + and X z is normalized to "1", it can be written as CO° coso0t X, = coso)lt Xz = coso, t.

In the first modulation circuit 1, a carrier wave C0 is amplitude-modulated in a carrier wave sending format using a first modulation signal X1, thereby creating a first modulated signal Y including a carrier wave C0 and upper and lower side band waves around the carrier wave C0. Ru. Note that for convenience of explanation, the modulation index is assumed to be "1".

That is, Y.

=XI co +CD = CO3ω, ' cosωot= 1/2
(cos(ω.+ω+) t + cos(ω.−
ω1) t] + coso, t −−
- (1) As shown in FIG. 2(A), the frequency spectrum of the first modulated signal Y1 is composed of an upper sideband and a lower sideband that are symmetrically distributed on both sides of the carrier wave c0. There is. Although illustration is omitted to avoid complexity, 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.

On the other hand, in one amplitude modulation circuit 2a of the second modulation circuit 2, the carrier wave C0 is amplitude-modulated by the second modulation signal X2. Further, in the other amplitude modulation circuit 2b, the second modulation signal X2 amplitude-modulates the opposite phase carrier wave -Co. This opposite phase carrier wave -00 is connected to the input terminal ■
, is created by passing the upper carrier wave C0 through the 180° phase shift circuit 2C.

The upper sideband included in the output of the amplitude modulation circuit 2a extracted by the bandpass filtering circuit 2d and the lower sideband included in the output of the amplitude modulation circuit 2b extracted by the bandpass filtering circuit 2e are combined. A second modulated signal Y2 is created by combining in the circuit 2f.

That is, 2 = (X, C0)□ + (Xz Co ) L=
1/2 (cos(ω.+ω2)t +cos((
do -dz)t ) H1/2 (cos(C6+ω
2) t +cos(Co -dz)t ) L=
1/2 (cos(ω.+ωt)t −CO3
((110-C2)t]・・・・(2) However, the symbols []□ and [] respectively mean to extract only the upper sideband wave and lower sideband wave within [].Furthermore, the extraction It is assumed that the carrier wave itself is not included in the upper and lower sidebands.

The frequency spectrum of this second modulated signal Y2 is
As illustrated in Figure (B), the positive phase upper sideband C(lX2
and the opposite-phase lower sideband -CoXz have a carrier frequency ω. /
It is distributed symmetrically around 2π.

The second modulated signal Y2 is amplitude limited by the inverse Nyquist filter 2g, and then multiplexed with the first modulated signal Yl by the multiplexing circuit 3, resulting in a signal as shown in FIG. 2(C). A frequency spectrum multiplexed television signal Z is created.

That is, =Yl +'1'2 = 1/2 (cos(ω.+ω+)t +cos
(Co −ω+)t ]+ 1. /2 (cos
(ω.+ωz)t −CO3((IJO(dz)t
) 1 COS ω, 1 ・ ・ ・ ・ (3) This multiplexed television signal Z is passed through the bandpass filter circuit 4
Therefore, due to band limitation, VSB- as shown in Figure 2 (D)
It becomes an AM system multiplexed television signal.

That is, for an NTSC television signal, a vestigial sideband (VSB) signal is generated that includes the entire upper sideband and a part of the lower sideband, and for a multiplexed signal, it is generated that includes both the upper and lower sidebands. A full-band double sideband (DSB) signal is generated. VSB television signals are D.
It can be considered that the low frequency portion of the SB method and the high frequency portion of the single sideband (SSB) method are combined.

Therefore, the multiplexed television signal shown in FIG. 2(D) is a low-frequency DSB in which the modulated signals Y and Y2 are multiplexed.
It can be considered separately into the high-frequency S38 part and the high-frequency S38 part where only the modulated signal Y exists. Regarding this embodiment, how the modulated signals y and Y2 are multiplexed by the transmitting device and how they are demultiplexed by the receiving device will be explained based on mathematical formulas. Therefore, in the following equations, please note that the modulated signal Y is the multiplexed portion with the modulated signal Y2, that is, the low frequency portion of the DSB method.

Here, the multiplexed signal Z is decomposed into a carrier wave C6, an upper sideband [Z]8 and a lower sideband CZ)L on both sides, and Z=CG + (z)N + [Z)L ・...
(4), (z) H = 1/2 (cos(ω0+ω+)t +C05((
JJO+ dz)t )... (5) (2) L = 1/2 (cos(ωO-ω+)t cos
(ωO−ω2)t]・・・・・(6) The following relationship is obtained.

The multiplexed television signal shown in FIG. 2(D) is frequency-converted in an RF converter, and transmitted to the receiving device by being radiated from the antenna 6 or sent out onto a cable from the output terminal 01.

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 modulated signal Y2 is subjected to amplitude limitations with opposite slopes by the inverse Nyquist filter on the transmitting side and the Nyquist filter on the receiving side, so that the second modulated signal Y2 is symmetrically integrated around the carrier wave C0. subject to severe amplitude limitations. 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 . Demodulation of the second modulated signals X+ and Xz is performed.

FIG. 4 is a block diagram showing the configuration of the demodulation device on the receiving side, where 4 is an input terminal for the multiplexed television signal Z, 7 is a carrier recovery circuit, 8 is a first demodulation circuit, and 9 is a first demodulation circuit. 2
0□ is the output terminal of the reproduced first modulated signal X, and 03 is the output terminal of the reproduced second modulated signal X2.

In the carrier wave reproducing circuit 7, the carrier wave C0 is reproduced from the multiplexed television signal Z supplied to the input terminal I4. This carrier wave regeneration circuit 7 has a phase locked loop (PLL
) circuit, tank circuit, etc.

In the synchronous detection circuit 8a of the first demodulation circuit 8, 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. By being extracted by the pass filter circuit 8b, the first
The modulated signal x, is demodulated. That is, “”[ZCo)c = (Y+ Co +Yz Co + Co
” ) t・・・・(7) Calculating each term in equation (7) yields Y+C.

= [cos(ω.+ω,)t-cosωot ten cos
(ω0−ω+)t 0cos ωat)=1/
2 (2cos ω, t + cos (2ω.+ω
1) t+cos(2ωo −ω,)1) ・(8) YZ C.

= (cos(ω0 +ωz) t °cos
ω, 1-cos(ω0-ωz)t'CO3ωot)
= 1/2 [cos(2ω. +ωz)t+(o
s(2ω0-ω2)t] ・(9) c.

= 1/2 (1+ cos2ω.t)・・
・ ・ (10) becomes.

here, ω. 〉〉ω1. ω2 Then, cos (2ω) in equations (8) to (10).

+ω+)t, cos(2ω0-ω+)t, co
s(2ω0+ωz)t, cos(2ω.-ω2)t
, cos2ω. Both t are removed as harmonic components.

Furthermore, since the DC component in equation (10) is also removed, (
7) From equations (10), XI = (ZCo ”J t =cosω1t... (11)
is obtained.

This is nothing but a demodulated NTSC television signal (first modulated signal X1) modulated, transmitted, and received according to the VSB-AM communication system by synchronous detection of the reproduced carrier wave C0.

On the other hand, in the second demodulation circuit 9, the upper sideband and lower sideband of the multiplexed television signal Z are extracted by bandpass filtering circuits 9a and 9b, respectively.

The extracted upper sideband is subjected to synchronous detection using the regenerated carrier wave C0 in the synchronous detection circuit 9c. Also,
The extracted lower sideband is subjected to synchronous detection using a recovered carrier wave -00 having an opposite phase in the synchronous detection circuit 9d. This reverse phase reproduced carrier wave -00 is the reproduced carrier wave C0
is obtained by passing it through a 180° phase shift circuit 9e.

The detection outputs output from the synchronous detection circuits 9c and 9d are combined by a combination circuit 9f, and the high-frequency components and DC components included in this combined signal are removed by the low-pass filter circuit 9g, thereby producing a second modulated signal X2. is played.

That is, 2 −((Z)++ Co (Z)L Co)t・・
・ ・ (12) If each term in equation (12) is calculated, (Z'1NCG = 1/2 (cos(ω.+ω1)(・cosω.

t+ cos (ω0+ω2)t °cosωot)
= 1/4 (cos(2ω.+ω+)t + cos
ω, t+ cos (2ω.+ωz)t + cosω
zt)・・・・・(13) [z) L CO = 1/2 (cos(ω0−ω+)t −co
sω, t+ (os (ω0−ωz>t −cosω
ot) = 1/4 Ccos(2ω.-ω+)t
CosωIt+ cos (2ω.-ωz)t +
cosωzt) (14) From equations (12) to (14), it becomes: Xz −CQSω2t (15) and the second modulated signal x2 is demodulated.

In the transmitting side device illustrated in FIG. 1, the amplitude modulation circuit 2a,
2b may be constituted by a carrier-suppressed double-side band modulation circuit such as a ring modulator. Note that the amplitude modulation circuits 2a and 2b
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 2d or 2e. The amplitude modulation circuits 1, 2a and 2b can also be realized by analog multiplication circuits using operational amplifiers.

A synchronous detection circuit having a configuration such as that described on page 150 of "HK Children's Television Techniques Textbook [Volume 1]" can be used. Alternatively, these synchronous detection circuits may be realized by analog multiplication circuits using operational amplifiers.

Furthermore, A/D multiplication circuits for amplitude modulation and synchronous detection are used.
It can also be configured by a combination of a conversion circuit, a digital multiplication circuit, and a D/A conversion circuit.

In this way, (1) Normal VSB in the first modulation section of the transmitting device
The modulated signal X, which 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.

(11) The second modulated signal 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 X1 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 second demodulator of the receiving side device, so that the signal of each sideband is The components are canceled out and eliminated.

(1) The second modulated signal In the demodulator, 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.

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,
I++, I+□, 113 are the first and second . Third
114 is the input terminal of the carrier wave C0, 11 is the first modulation circuit, 12 is the second modulation circuit, 13 is the third modulation circuit, 14 is the 90° phase shift 15 is a synthesis circuit, 16 is an inverse Nyquist filter, 17 is a multiplexing circuit, 18 is a bandpass filter circuit, 19 is an RF converter, 20 is a transmitting antenna, and o4 is an output terminal.

The second modulation circuit 12 includes an amplitude modulation circuit 12a, bandpass filter circuits 12b and 12c, and an fIi calculation circuit 12d. Similarly, the third modulation circuit 13 includes an amplitude modulation circuit 13a, bandpass filter circuits 13b and 13C, and a subtraction circuit 13d.

The first modulation circuit 11 has an NTSC signal on the input terminal III.
A television signal is provided as a first modulated signal X, and an intermediate frequency carrier wave C0 on input terminal 114 is provided. The carrier wave C0 is amplitude-modulated by the first modulation signal XI, becomes a modulated signal Y, and is supplied to one input terminal of the multiplexing circuit 17.

The second modulation circuit 12 is supplied with an additional signal such as a wide aspect signal from an input terminal 1+t as a second modulation signal X2, and an intermediate frequency carrier C0 on an input terminal I+4.
is supplied. In the amplitude modulation circuit 12a, the carrier wave C0 is amplitude-modulated with the second modulation signal X2. The upper sideband (Xi Co )M included in this modulated signal is extracted by the bandpass filter circuit 12b, and the lower sideband (Xz Co
)t is extracted by the bandpass filter circuit 12C. In the subtraction circuit 12d, the lower sideband [Xt Co )t is subtracted from the upper sideband (Xz Co )o, and the second transmission signal Yf
fi = CXz Co )) I (Xz Co )
L is created.

On the other hand, the third modulation circuit 13 receives an additional signal such as the remaining part of the wide aspect signal from the input terminal 11°.
is supplied as a modulated signal X3, and an orthogonal carrier wave whose phase is shifted by 90 degrees from the carrier wave C0 is supplied from the input terminal I+4 through the 90 degree phase shift circuit 14. In the amplitude modulation circuit 13a, the orthogonal carrier wave CO is amplitude-modulated with the third modulation signal X3. The upper sideband (XiCo) included in this modulated signal is extracted by the bandpass filter circuit 13b, and the lower sideband [X, co)L is extracted by the bandpass filter circuit 13C. In the subtraction circuit 13d, the lower sideband CX3Co )L is subtracted from the upper sideband [X300], and the second transmission signal Y3 = (X3Co ) +4 (X3C0
] 1 is created.

Second. The third modulated signals Yz and Ys are sent to the synthesis circuit 15.
and is subjected to amplitude limitation by an inverse Nyquist filter 16. The amplitude-limited modulated signals Yz and Y3 are multiplexed with the modified all signal Y in the multiplexing circuit 17, and subjected to band-limiting in the bandpass filter circuit 18 as a multiplexed television signal. signal Z, frequency converted by RF converter 19, radiated from antenna 20, output terminal 0. The data is transmitted to the receiving device by being sent out over a cable.

FIG. 6 shows a first . Second. Third modulation signal X+, Xz
, Xi is a block diagram showing the configuration of a receiving side device that demodulates the signals.

In FIG. 6, IZ'l is an input terminal for a multiplexed television signal Z received and converted into an intermediate frequency band, 31 is a first demodulating circuit, 32 is a second demodulating circuit, and 33 is a third demodulating circuit. 34 is a carrier wave regeneration circuit, 35 is a 90° phase shift circuit, and 021.022102:l is the demodulated first . Second
．． This is an output terminal for the third modulation signal X I + X Z +x3.

In the carrier wave reproducing circuit 34, an intermediate frequency carrier wave C0 is reproduced from the multiplexed television signal Z supplied to the input terminal IZI. This reproduced carrier wave C0 is the first. 90° phase shift circuit 35
After that, it becomes an orthogonal recovered carrier wave with a 90' phase shift and the
The signal is supplied to the demodulation circuit 33 of.

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. In this demodulation, as already explained with respect to equations (7) to (11), signal components in both side bands having opposite polarities are canceled out in the modulated signal X2. In this way, in the first demodulation circuit 31a, the NTSC television signal is demodulated as the first modulation signal X1, and is supplied from the output terminal 021 to a signal processing circuit such as a Y/C separation circuit in the subsequent stage.

On the other hand, in the second demodulation circuit 32, the bandpass filter circuit 32
a and 32b, the upper sideband [Z)H and lower sideband (Z)L of the multiplexed television signal Z are extracted. The extracted upper sideband (z)M is subjected to synchronous detection using the reproduced carrier wave C0 in the synchronous detection circuit 32c. Further, the extracted lower sideband CZ:lt is subjected to synchronous detection using the reproduced carrier wave C0 in the synchronous detection circuit 32d. In the subtraction circuit 32e, the detection output of the synchronous detection circuit 32d is subtracted from the detection output of the synchronous detection circuit 32c. The high-frequency component and DC component included in this subtracted output are removed by the low-pass filter circuit 32g, thereby reproducing the second modulated signal X2.

When demodulating this second modulation signal X2, the first modulation signal
The fact that the signal components of both sidebands of 1 cancel out and disappear is as follows.
This is as explained using equations (12) to (14). Furthermore, it is clear from the principle of orthogonal two-phase modulation that when demodulating the second modulation signal X2, the phase of the carrier wave for the third modulation signal X3 shifts by 90' from the time of modulation, so the demodulation signal component becomes zero. It is. In this way, the second demodulation circuit 32 demodulates only the second modulation signal X2, and outputs it to the output terminal 02 as an additional signal such as a wide aspect signal.
The signal is supplied from □ to the subsequent signal processing circuit, etc.

Furthermore, in the third demodulation circuit 33, the bandpass filter circuit 3
3a and 33b respectively extract the upper sideband (z)H and lower sideband (z)L of the multiplexed television signal Z. The extracted upper sideband (Z)H is subjected to synchronous detection using the reproduced orthogonal carrier C0 in the synchronous detection circuit 33C. Further, the extracted lower sideband (z)L is subjected to synchronous detection using the reproduced orthogonal carrier C0 in the synchronous detection circuit 33d. In the subtraction circuit 33e,
From the detection output of the synchronous detection circuit 33c to the synchronous detection circuit 33d
The detection output of is subtracted. The high-frequency component and DC component included in this subtracted output are removed by the low-pass filter circuit 33g, thereby reproducing the third modulated signal X3.

When demodulating the modulated signal X3 of IK3, the phase of the carrier wave for the first and second modulated signals X, , X is shifted by 90° from that during modulation, so the demodulated signal component becomes zero.
This is clear from the principle of orthogonal two-phase modulation. In this manner, the third demodulation circuit 33 demodulates only the third modulation signal X3, and outputs it as an additional signal such as a wide aspect signal from the output terminal 02° to a subsequent signal processing circuit.

The transmitting device shown in FIG. 5 and the receiving device shown in FIG. It is installed. However, if these bandpass filter circuits are
．． It may be configured to be shared by each system of the third modulation signal x2°X.

That is, as for the transmitting side device, as shown in the block diagram of FIG.
The modulated outputs of the amplitude modulation circuits 12a and 13a are first combined by a combining circuit 15', and upper and lower sidebands of this combined signal are separated by shared bandpass filter circuits 12b and 12C. The separated sidebands are subtracted by a subtraction circuit 12d to produce a second and third modulated signal Y2. Y3 becomes the combined signal, which passes through the inverse Nyquist filter 16 and is sent to the multiplexing circuit 1.
7, the signal is multiplexed into the first modulated signal Y1. 7th
The configuration and operation of the remaining portions in the figure are the same as the corresponding portions already described with respect to FIG. 5, so a redundant explanation thereof will be omitted.

Similarly, for the receiving device, as shown in the block diagram of FIG. 8, the upper and lower sidebands (Z)H and (z)L of the multiplexed television signal Z supplied to the input terminal I2□ are First, it is separated by a shared bandpass filter circuit 32a and 32b,
Synchronous detection is performed using respective synchronous detection systems using a regenerated carrier wave and a regenerated orthogonal carrier wave. The configuration and function of each synchronous detection system are the same as those of the corresponding receiving side apparatus already explained with reference to FIG. 6, and therefore redundant explanation will be omitted.

(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 side device applying the VSB-AM communication method according to an embodiment of the present invention, and FIG. NT
The second modulated signal y is added to the SC television signal (the first modulated signal y).
A conceptual diagram for explaining an example of the frequency spectrum of a multiplexed television signal obtained by multiplexing the second modulated signal Y2 generated by the modulation circuit of FIG. FIG. 4 is a conceptual diagram showing the frequency spectrum of the first frequency spectrum from the multiplexed television signal.
．． A block diagram showing the configuration of a receiving side device that demodulates the second modulated signal, and FIGS. 5 and 6 are VSs of other embodiments of the present invention.
A block diagram showing the configuration of the transmitting side device and the configuration of the receiving side device that use the B-AM communication method, and FIGS. 7 and 8 are transmissions that apply the VSB-AM communication method according to still another embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of a side device and a receiving side device. 11+I11...input terminal of first modulation signal X, I
z, I+z...input terminal of second modulation signal X2, II
3... Input terminal for third modulation signal X3, I3, 114
... Input terminal of carrier wave C0, 1, 11 ... First modulation circuit, 2, 12 ... Second modulation circuit, 2a, 2b, 1
2a...amplitude modulation circuit, 2d, 2e, 12b, 1
2cm--band pass filter circuit, 13... third modulation circuit, 13a... amplitude modulation circuit, 13b, 13c...
Bandpass filter circuit, 3, 17... multiplexing circuit, 2g,
16... Inverse Nyquist filter, 14,121...
Input terminal for receiving multiplexed television signal, 7°34 ・
...carrier regeneration circuit, 8.31...first demodulation circuit,
9, 32... second demodulation circuit, 33... third demodulation circuit, 9a, 9b, 32a. 32b, 33a, 33b -- band pass filter circuit, 9c
, 9d, 32c, 32d, 33C, 33d... synchronous detection circuit, 03.02+... demodulated first modulation signal X
, 0□, o2□... Output terminal of demodulated second modulated signal X2, 0□3... Output terminal of demodulated third modulated signal X3. Figure 2 C'JO/2L

Claims (10)

[Claims] (1) On the transmitting side, a first modulating means that amplitude-modulates a carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands, and a first modulation means that modulates the amplitude of a carrier wave with a first modulation signal, a second modulating means for generating a second modulated signal by amplitude modulating the amplitude with a second modulating signal having a narrower band than the second modulating signal, and synthesizing the upper and lower sidebands so as to have opposite polarities; If the carrier wave is not included in any of the first modulated signal and the second modulated signal whose amplitude has been limited by the inverse Nyquist filter, These first and second
a combining means for synthesizing the modulated signals of the first modulated signal; band limiting means for limiting the band of the second modulated signal whose amplitude is limited in a narrow band so as to become a DSB format signal including all of both side bands; and means for transmitting the received 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 synchronization of the multiplexed signal with the regenerated carrier wave. a first demodulating means for detecting and reproducing the first modulated signal; and synchronously detecting each signal band including upper and lower sidebands of the second modulated signal in the multiplexed signal with the regenerated carrier wave. a second modulated signal for reproducing the second modulated signal by removing unnecessary frequency components from the combined signal and reproducing the second 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; a second modulating means for generating a second modulated signal by amplitude modulating the amplitude with a second modulating signal and combining the upper and lower sidebands so as to have opposite polarities; an inverse Nyquist filter that limits the amplitude; and if the carrier is not included in either the first modulated signal or the second modulated signal whose amplitude has been limited by the inverse Nyquist filter, the carrier is included; a synthesizing means for synthesizing these first and second modulated signals; band limiting means for limiting the band so that the second modulated signal is a VSB format signal including a band and whose amplitude is limited in a narrow band, so that the second modulated signal is a DSB format signal including all of both side bands; . A transmitting side device of a VSB-AM communication system, comprising: means for transmitting the combined and band-limited signals as a multiplexed signal. (3) The second modulation means includes one amplitude modulation circuit that modulates the amplitude of the carrier wave with the second modulation signal, and an amplitude modulation circuit that modulates the amplitude of the carrier wave with the second modulation signal, and amplitude modulates the carrier wave with the same frequency and opposite phase as the carrier wave with the second 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 comprises a signal extraction circuit for extracting the other signal of the band, and an addition circuit for adding the signals extracted by these signal extraction circuits. sending device. (4) The second modulation means includes an amplitude modulation circuit that amplitude modulates the carrier wave with the second 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 sent out according to the VSB-AM communication method as set forth in claim 1; carrier wave regeneration means for regenerating the carrier wave included in the received multiplexed signal; a first demodulator for regenerating a first modulated signal by synchronously detecting a multiplexed signal using a regenerated carrier wave; and second demodulation means for synchronously detecting the recovered carrier waves, synthesizing them so that they have opposite polarities, and removing unnecessary frequency components from the synthesized signal to reproduce the second modulated signal. A transmitting side device of the VSB-AM communication method. (6) The second 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 second 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 for amplitude modulating a carrier wave with a first modulation signal to create a first modulated signal including upper and lower sidebands; a second modulation means that generates a second modulated signal by amplitude modulating the amplitude with a second modulation signal having a narrower band than the carrier wave and combining the upper and lower sidebands so as to have opposite polarities; A carrier wave whose phase is shifted by 90° is amplitude-modulated with a third modulation signal having a narrower band than the first modulation signal, and the upper and lower sidebands are combined so that they have opposite polarities to each other to generate a third modulated signal. a third modulating means for generating a signal; an inverse Nyquist filter for amplitude limiting the second and third modulated signals; and a second modulated signal whose amplitude is limited by the first modulated signal and the inverse Nyquist filter. combining means for combining the first, second, and third modulated signals while including the carrier wave if none of the third modulated signals includes the carrier wave; 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 the second and second modulated signals are narrow band amplitude limited. Regarding the modulated signal of No. 3, it is provided with a band limiting means for limiting the band so that it becomes a DSB format signal including all of both sidebands, and a means for transmitting the combined and band limited signal as a multiplexed signal. , on the receiving side, a carrier regenerating means for regenerating a carrier 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. demodulating means; and each signal band including upper and lower sidebands of the second modulated signal in the multiplexed signal is synchronously detected with the regenerated carrier wave and synthesized so that the polarities are opposite to each other, and the synthesized signal is synthesized. a second modulated signal for reproducing the second modulated signal by removing unnecessary frequency components from the second modulated signal;
demodulating means, and each signal band including upper and lower sidebands of the third modulated signal in the multiplexed signal is synchronously detected with the regenerated carrier wave and synthesized so that the polarities are opposite to each other, and the synthesized signal is synthesized. a third modulated signal that reproduces the third modulated signal by removing unnecessary frequency components from the modulated signal;
A VSB-AM communication system characterized by comprising demodulation means. (9) 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; a second modulation means that generates a second modulated signal by amplitude modulating the amplitude with a second modulation signal and combining each of the upper and lower sidebands so that they have opposite polarities; A third modulated signal is created by amplitude modulating the carrier wave with a third 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 and third modulated signals; and a second and third modulated signal whose amplitudes are limited by the first modulated signal and the inverse Nyquist filter. combining means for combining the first, second, and third modulated signals while including the carrier wave if none of the signals includes the carrier wave; The second and third modulated signals are band-limited in a narrow band so that the modulated signal is a VSB format signal that includes the entire band of one sideband and a part of the band of the other sideband. The device is characterized by comprising: band limiting means for limiting the band so that it becomes a DSB format signal including all of both sidebands; and means for transmitting the combined and band limited signal as a multiplexed signal. A transmitting side device of the VSB-AM communication method. (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 demodulator for regenerating a first modulated signal by synchronously detecting a multiplexed signal using a regenerated carrier wave; a second demodulating means for synchronously detecting the regenerated carrier waves and combining them so that they have opposite polarities, and removing unnecessary frequency components from the combined signal to regenerate the second modulated signal; Each signal band including the upper and lower sidebands of the third modulated signal is synchronously detected using a regenerated orthogonal carrier wave whose phase is shifted by 90 degrees from the regenerated carrier wave, and is synthesized so that the polarities are opposite to each other,
A transmitting side device for a VSB-AM communication system, comprising: third demodulating means for removing unnecessary frequency components from the composite signal and reproducing the third modulated signal.