AU602279B2 - Creation of Inventions and Patents with Artificial Intelligence

AU602279B2 – Picture quality indicator for satellite broadcasting receiver
– Google Patents

AU602279B2 – Picture quality indicator for satellite broadcasting receiver
– Google Patents
Picture quality indicator for satellite broadcasting receiver

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Publication number
AU602279B2

AU602279B2
AU27586/88A
AU2758688A
AU602279B2
AU 602279 B2
AU602279 B2
AU 602279B2
AU 27586/88 A
AU27586/88 A
AU 27586/88A
AU 2758688 A
AU2758688 A
AU 2758688A
AU 602279 B2
AU602279 B2
AU 602279B2
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AU
Australia
Prior art keywords
amplifier
output
picture quality
satellite broadcasting
noise
Prior art date
1987-12-29
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Ceased

Application number
AU27586/88A
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AU2758688A
(en

Inventor
Mitsugu Kuboki
Noriaki Omoto
Osamu Shizuya
Yoshikazu Yoshimura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Panasonic Holdings Corp

Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1987-12-29
Filing date
1988-12-23
Publication date
1990-10-04

1988-12-23
Application filed by Matsushita Electric Industrial Co Ltd
filed
Critical
Matsushita Electric Industrial Co Ltd

1989-06-29
Publication of AU2758688A
publication
Critical
patent/AU2758688A/en

1990-10-04
Application granted
granted
Critical

1990-10-04
Publication of AU602279B2
publication
Critical
patent/AU602279B2/en

2008-12-23
Anticipated expiration
legal-status
Critical

Status
Ceased
legal-status
Critical
Current

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Classifications

H—ELECTRICITY

H04—ELECTRIC COMMUNICATION TECHNIQUE

H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION

H04N5/00—Details of television systems

H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards

H04N5/445—Receiver circuitry for the reception of television signals according to analogue transmission standards for displaying additional information

H—ELECTRICITY

H04—ELECTRIC COMMUNICATION TECHNIQUE

H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION

H04N17/00—Diagnosis, testing or measuring for television systems or their details

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01Q—ANTENNAS, i.e. RADIO AERIALS

H01Q1/00—Details of, or arrangements associated with, antennas

H01Q1/12—Supports; Mounting means

H01Q1/125—Means for positioning

H01Q1/1257—Means for positioning using the received signal strength

H—ELECTRICITY

H04—ELECTRIC COMMUNICATION TECHNIQUE

H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION

H04N7/00—Television systems

H04N7/20—Adaptations for transmission via a GHz frequency band, e.g. via satellite

Description

r i~;c c 6022 ’79 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLTE SPECIFICATION NAME ADDRESS OF APPLICANT: Matsushita Electric Industrial Co., Ltd.
1006, Oaza Kadoma Kadoma-shi Osaka-fu, 571 Japan NAME(S) OF INVENTOR(S): Noriaki OMOTO Mitsugu KLUBOKI Osamu SHIZUYA Yoshikazu YOSHIMURA ADDRESS FOR SERVICE: f This documnt maii n er ps 5 n) I A V t fl-.’9 tid iN. .uIc DAVIES COLLISON Patent Attormey 3 1 Little Collins Street, Melbourne, 3300.
COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Picture quality indicator for satellite broadcasting receiver The following statement is a full description of this invention, including the best method of performing it known to me/us:- 4- I c I -li i IIL_ L FIELD OF TIHE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION: The present invention relates to a satellite broadcasting receiver, particularly relates to a received picture quality indicator of the satellite broadcasting receiver that can be used for such as the installation pointing angle adjustment of an antenna by use of the quality indication of received broadcasting waves.
2. DESCRIPTION OF THE PRIOR ART: A rather long time has already passed since the transmission of TV signals between broadcasting stations utilizing geostationary satellites was put into practical use. And, the satellite broadcasting for the actual t C’ public service to be received by individual domestic c receivers has been started. The conventional satellite 0 G
S
t c broadcasting, for example used in Japan, is that, as shown a c e in FIG.13. Microwave carrier wave is modulated by TV signals and radiated from a geostationary satellite. And at the ground, it is focused by a satellite broadcasting a reception antenna 31 (in Japan this antenna is named and called as BS antenna, hence it is also referred to as BS antenna hereinafter). Then, the microwave carrier wave is converted into 1-GHz band using a satellite broadcasting 00 0a c. converter 32 (In Japan this is named and called as BS converter, and hereinafter it is referred to as BS converter) which includes a ultra-low noise amplifier.
Using a coaxial cable 33 the output signal from the BS converter 32 is sent to a satellite broadcasting receiver 34 (in japan it is named and called as BS tuner, then also hereinafter it is referred to as BS tuner) which is usually installed inside of a house. Then, the channel is selected and signal processing such as PM-demodulation is carried out, and the output of video and audio signals are delivered to a TV receiver To get high quality pictures on a TV scten, it is necessary to increase the SN ratio (signal to noise ratio) of the demodulated video signals. Since the SN ratio of the demodulated video signal is proportional to the CN ratio (carrier to noise ratio), i’t is also necessary to increase the CN ratio to attain high quality pictures. In order to get a larger CN ratio, it is necessary to keep the noise level as low as possible by using a low noise BS converter and also to raise the carrier level as high as i possible by using a high gain BS antenna. As for a BS ‘antenna for the direct reception system as is described here, antennas of high gains such as of 35 dBi are ordinarily used, so their directivitles necessarily become extremely sharp such as around 2 degrees in their halfmaximum angle, Consequently, in order to extract the
L*J
__~LCL
I I capability of those antennas, it becomes necessary to make the antenna point precisely to the incident carrier wave direction at the time of antenna installation.
For this purpose, heretofore the AGC terminal voltage in the BS tuner 34 has been utilized for adjusting antenna pointing angle (direction) and from which an output voltage proportional to the input signal power level to the BS tuner 34 is obtained and is indicated on such as a voltmeter 36 as shown in FIG.13. A BS tuner wherein the antenna pointing angle adjustment is carried out by using the AGC output terminal voltage is constituted as shown, for example, in FIG.14. FIG.14 is an outline block diagram showing a part of a BS tuner from input stage to an AGO detector stage of 1-st IF (intermediate frequency In FIG.14, numeral 41 designates a 1-st IF input terminal of the BS tuner, S numeral 42 designates a 1-st IF amplifier, numeral 43 designates a frequency converter, numeral 44 designates a a0 4 on .local oscillator, numeral 45 designates an AGC amplifier (variable-gain amplifier), numeral 46 designates a bandpass filter (BPF), numeral 47 designates an AGC detector, 4 numeral 48 designates a DC level-shift amplifier, and a V, numeral 49 designates an AGC output terminal. The IF signal inputted trough the 1-st IF input terminal 41 is channel-selected by the frequency converter 43, and then, the signal is inputted through the AGC amplifier 45, the a 4 3 BPF 46, to the demodulator. The AGC detector 47 is to detect the signal level, which issues a control voltage Vc responding to the detected level. The AGC amplifier 45 is a variable-gain amplifier, which acts so as to make the I AGC detected level constant by changing the gain in accordance with the control voltage Vc.
is a drawing showing an example of the gain control characteristic of the AGC amplifier 45. In general, since the forward AGC scheme employing transistors is used, the gain decreases as the gain I control voltage increases. The time when the gain of the AGC amplifier is high corresponds to the case that the 1st IF input signal level is low, whereas the time when the gain of the AGC amplifier is low corresponds to the case that the the 1-st IF input signal level is high.
I Accordingly, the relation between the AGC control vo.tage Vc and the 1-st IF input signal level becomes almost in a proportional relation as is shown in FIG.16.
The 1-st IF input signal level C of the BS tuner can be expressed by (Refer to a literature: “Satellite Broadcasting Receiver, Part 1, Specification of -Target, Dempa-Gijutu Kyoukai): C (EIRP.G c Gr)/(B R. Lf L k) (1) where EIRP Equivalent isotropic radiation power of satellite Lf Free space propagation loss Gr :Antenna gain P Antenna pointing loss R Attenuation due to rain G, BS converter gain Lk Attenuation due to cable.
According to Eq(l), the 1-st IF input signal level of the BS tuner is in an inversely proportional relation to the antenna pointing loss. Therefore, by delivering the AGC control voltage through an auxiliary out.lut terminal provided on the BS converter and reading it by such as a voltmeter, it becomes possible to make the antenna pointing loss to be zero. Thus, the antenna pointing angle adjustment is achievable by making the 1-st IF signal input level reaches its maximum.
In such the constitution as described above, however, as is clear from the level of 1-st IF input signal of the BS tuner depends not only on the input intensity of incident carrier wave into the BS antenna 1, which determines the picture quality, but also depends upon the gain of the BS converter and the attenuation of the coaxial cable connecting the BS converter to the BS tuner. The gain of the BS converter is usually 48 dB 4 r and the attenuation of the coaxial cable is in a range frorm 4 dB to 15 dB for lengths of 10 m to 30 m. Taking the sum of these attenuations, the range of the 1-st IF input signal level becomes as wide as of 23 dB.
.,it Accordingly, in the conventional scheme, the AGC output *r terminal level varies depending on the gain of the BS converter as well as on the length of the coaxial cable either of whii,., have no direct relation to the TV signal reception CN ratio in the BS reception system. For this reason, although the use of the AGC output terminal is useful for the antenna pointing angle adjustment, there has been a problem that it cannot be used for the indication of the measure of the received picture goodness (received picture quality).
OBJECT AND SUMMARY OF THE INVENTION i The purpose of the present invention is to provide a stable received picture quality indication circuit that is capable of indicating the received picture quality (CN ratio) of the satellitL broadcasting receiver apparatus, and hence usable for the antenna pointing angle adjustment procedure at the time of antenna installation.
in ordcr to aclhieve this p* e ,-a-p-i-e-ttre quality indicator for satellite TV receiver of the present invention comprises an FM-demodulator for demodulating the satellite TV signal, a band-pass filtep-for receiving demodulated output .as its input s-[gnal and removing e.g.
the TV signal components, video .uminance component, color sub-carrier cpm onent of the video signal and its second and t ‘d harmonics and audio sub-carrier component and it armonics from the demodulated output signal .4utted thereto, thereby to extract ose-epene- an–‘ ‘i The present invention provides picture quality indicator for satellite broadcasting receiver comprising: an FM-demodulator for demodulating a satellite broadcasting signal comprising TV signals, I 5 a band-pass filter adapted to remove the TV signals by passing only a i demodulated noise component at frequency bands outside the spectrum of the TV signals, an amplifier for amplifying ,ad noise component, a detection circuit for detecting the amount of said noise component output from said amplifier, and a level indicator for indicating the figure of merit (or picture quality factor) of received picture quality in relation to the output level of said detection circuit.
Preferably said band-pass filter has a characteristic which passes only the noise component which include no video luminance signal component, no color sub-carrier nor its second, third harmonic components, no audio subcarrier component nor its harmonic components.
Preferably the amplifier amplifying the noise component is an amplitude-limiting type amplifier wherein the amplification gain decreases as the noise level increases.
Preferably the present invention provides picture quality indicator for satellite bradcasting receiver comprising: an FM-demodulator for demodulating a satellite broadcasting signal Scomprising TV signals, a band-pass filter adapted to remove the TV signals by passing only a demodulated noise component at frequency bands outside the spectrum of the Tv ignals, a first amplifier for amplifying said noise component, a detection circuit for detecting the amount of said noise component output from said amplifier, and a second amplifier for amplifying the output of said detection circuit, said second amplifier having variable gain characteristic such that the gain thereof decreases as the input thereto increases, and -6b- 1 a level indicator for indicating the figure of merit 2 (or picture quality factor) of received picture quality in J 3 relation to the output level of said second amplifier.
4 6 7 8 ‘1 10 9 11 12 13 14 16 17 18 19 21 22 23 24 i S 26 27 28 29 31 32 33 34 36 900323.cadat.075, shita. 1,6 i i -i i amplilfitL ful a 11 plifying the cXtrta ample level for the detection and has an amplitude’ limiting amplification function which loweps the amplification gain when the noise f 1 becomes high, a detection circuit for deliver g DC outputs proportional to the amplified nois ower level received thereby, and a level indicato or indicating the goodness of the recepti picture quality in accordance with the above- G-utput le~e- rc,!coivod thereby.
SIn the present invention, by the constitution as j described above, TV signals comprising video signal and audio sub-carrier and the demodulated output components :i comprised of demodulated noise component varyi ig depending upon the BS antenna input level are issued from the FM- Sdemodulator. Then, by the bhnd-pass filter, only the demodulated noise component at frequency bands at which no i TV signal is present, can be extracted. In the demodulated noise component at the signal detector output i terminal of FM scheme, their noise amplitude increases as i the demodulation frequency goes higher such as they are called as the rectangular noise. Therefore, the higher the frequency of the band-pass filter is selected, the larger the noise voltage is obtained. And hence, from a band-pass filter whose center frequency is higher than the highest frequency component of the composite TV signal, the extraction of the noise component is made easily. And I 7 the noise voltage becomes decreasing as the BS antenna input level increases. The noise component extracted by the band-pass filter is amplified up to an ample level by an amplifier, then thereafter inputted into a detection circuit to detect the noise component, and thus, the DC output corresponding to the level of the noise voltage is obtained.
Hereupon, since the output level of the video signal of the demodulated TV signal is specified to be 1 Vp-p, the SN ratio of the video signal is inversely proportional to the DC output corresponding to the amount of the noise voltage detected as described above.
Accordingly, if this DC output is converted into a DC output voltage proportional to the SN ratio, degree of the receiver capability can be evaluated by this DC output.
And, the level indicator superposes this DC output level on the TV signal, and by known function of the on-screen ;t ‘level indicator, SN ratio of the demodulated video signal is displayed on the picture screen of a TV receiver.
The relation between the SN ratio of the demodulated TV signal and the CN ratio of the received signal can be expressed by .I EMP. In IpM represents the FM improvement factor, IEMP indicates thefactor of improvement by the emphasis. Upon application of Japanese satellite broadcasting ii c s~”rspecifications, IFM and IEMP become IFM= 21 dB and IEMp=29 dB. According to the SN ratio and the CN ratio are in a proportional relation, then when the CN ratio changes due to the gain variation by the change of antenna pointing direction, the SN ratio also changes, thus by displaying the SN ratio on a displayed TV picture screen, it can be utilized for the antenna pointing angle adjustment at the time of antenna installation.
Furthermore, in case that an amplitude limiting type amplifier is used for the amplifier for amplifying the noise component, even if the noise voltage level becomes larger than a specified constant level, the DC output detected by the detection circuit becomes to be suppressed, owing to the amplitude limiting action.
Therefore, even for a rapid degradation of the SN ratio at low level inputs due to such as any deviation in the antenna pointing angle, it can keep the indication which is approximately proportional to the CN ratio.
BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a block diagram of a satellite broadcasting receiver picture quality indicator in a first :-li embodiment of the present invention.
FIG.2 is a spectral diagram of a demodulated signal in the demodulated output of a BS tuner.
FIG.3 is a spectral diagram of a demodulated noise in the demodulated output of a BS tuner.
S4 0 a 09 FIG.4 is a characteristic curve showing a relation of the CN ratio versus detected noise output in case of using an amplifier excluding an amplitude limiting I function.
is a characteristic curve showing a I relation of the CN ratio versus detected noise output in case of using an amplifier having the amplitude limiting function.
FIG.6 is a circuit diagram which shows an example of an amplifier having the amplitude limiting function.
i FIG.7 is an input-output characteristic of such i the amplifier, FIG.8 is a plan view showing an Indication I scheme on a displayed TV picture.
FIG.9 is a block diagram of a satellite broadcasting receiver picture quality indicator in a second embodiment of the present invention.
is an output characteristic of an I amplifier of the above-mentioned satellite broadcasting receiver picture quality indicator.
FIG.11 is a characteristic curve showing a relation of the output versus the CN ratio of the amplifier.
FIG.1J is a circuit diagram showing an example of the amplifier in the’second embodiment.
**10 0 I I FIG.13 is an illustration showing an antenna Spointing angle adjustment scheme using an AGC output terminal.
FIG.14 is a block diagram showing the constitution of a BS tuner for obtaining the AGC output.
and FIG.16 are characteristic curves showing that the AGC output terminal is proportional to the 1-st IF signal level.
DETAILED DESCRIPTION OF TIE PREFERRED EMBODIMENTS In the following, on one embodiment of the present invention, explanation is given with referring to the drawings. FIG.1 is a block diagram of a satellite broadcasting receiver picture quality indicator in a first i embodiment of the present invention. In FIG.1; numeral 1 designates a 1-st IF input terminal through which the signal from a BS converter is fed by a coaxial cable; numeral 2 designates a channel selection circuit selecting each station from a number of channels; numeral 3 I designates an FM-demodulhtion circuit for demodulating the FM-modulated signal; numeral 4 designates a band-pass filter for extracting the noise component from the FMdemoduiated output signal: numeral 5 designates an amplifier for amplifying the extracted signal up to a necessary level for the detection; numeral 6 d,’-gnates a detector for obtaining a DC output (detected .Jtput) corresponding to the amount of noise power; numeral 7 11 I ii i 1. designates a video signal processing circuit for performing the application of the de-emphasis on the FM- 1 demodulation output or the removing of the energy dispersal signal components which are characteristic of the FM-demodulation output; numeral 8 designates an onscreen indication circuit, which superposes the detected output of the noise. amount from the detector 6 on the video signal and indicates it on a TV receiver screen.
On the satellite broadcasting receiver picture quality indicator constituted as described above, its operation is elucidated below. First, the received signal inputted onto the 1-st IF input terminal 1 of the BS tuner is channel-selected by the channel selection circuit 2,
I
and after receiving the FM-demodulation by the FMi demodulation circuit 3. And then, after obtaining video signal by carrying out the de-emphasis, energy dispersal signal removal as well as audio sub-carrier signal removal in the video signal processing circuit 7, the informations I such as the channel indication and volume indication are j| superposed on the video signal by the on-screen indication circuit 8, and thereafter it is sent to the TV receiver 9, The operation of the circuit described so far is ordinarily included in the functions of a BS tu The FM-demodulated signal is, as shown in FIG.2, comprised of video luminance component, video color subcarrier component (center frequency 3.58 Milz), audio 4 r, 4 i _I i sub-carrier component (center frequency 5.727272 MHz) and higher harmonics of video color sub-carrier components. And in the demodulated noise, as shown in SFIG.3 and as it is called as triangular noise, its noise power increases as the frequency increases. Therefore, for the band-pass filter (BPF) 4, which is for removing the demodulated signal component and for extracting only the noise component, it is desirable to take its center j i frequency to be around 8 IMHz and its bandwidth to be of an order of 1 MHz. In case of selecting the center frequency of the BPF to be 11 MHz or higher, the demodulated signal component can be removed. However, in general, since the frequency bandwidth of the FM demodulator of the BS tuner is spreading over frequencies from 50 Hz up to about 8 MHz, and frequency components higher than this is not guaranteed and hence the output level of the noise component becomes dropping at high frequencies. Therefore, it becomes necessary to take the gain of the rear stages higher, but such high gain of the rear stage Iintroduces a wide-scattering fluctuation of the noise |1 component, and is not desirable. The noise extracted by the BPF 4 is amplified by the amplifier 5 up to a sufficient level for the detection by the detector 6 using a diode, and inputted into the detector 6 and detected there. In case of absence of the amplitude limiting 1function in the amplifier 5, when thre I CN ratio of the input signal is changed, for example, when the CN ratio drops, the detected output increases sharply as is shown in FIG.4. This is considered to be caused by that, in the case of satellite broadcasting, since the FM is employed for the modulation of the video signal, at levels below about 9 dB the so-called threshold phenomenon takes place and hence the noise level increases sharply.
If the detected output thus obtained described above and as shown in FIG.4 is indicated directly, that is, without adding any processing, the linearity of the indication output against the change of the CN is not a desirable one, and an available range of the indication is also limited. For this reason, a certain device for eliminating the above-mentioned difficulty is required, thus by limiting the noise amplitude not so as to exceed a specified value by means of giving an amplitude limiting function to the gain of the amplifier, the linearity of the detected output against the CN ratio is improved and can be brought into such as shown in The amplifier having the amplitude limiting function can be realized using a transistorized differential amplifier as shown in F.G.6, wherein Q1 and Q2 are transistors, R 1
R
2
R
3 and R 4 are bias resistors of transistors Q, and Q 2
R
5 and R 6 are load resistors, Ry, Rg and R 9 are emitter resistors. Terminals 11 and 20 are input and output terminals, respectively, and terminal c I 1 i i Ii is for connection to a positive power source terminal.
The input-output characteristic of this differential amplifier is shown in FIG.7, whose curve shows a constant gain in a region where the input levels are small. This is because, when the input becomes large, the output cannot become large exceeding the difference between the power supply voltage and the emitter voltage, and a gain saturation region appears in a region where the input levels are large as shown in FIG.7. If this amplifier is used as a final stage of the noise amplifier, the noise voltage cannot become larger than a specified value. Then it becomes possible to suppress a sharp increase of the noise power to be applied to the detector due to a degradation of the CN ratio caused by the threshold phenomenon, and hence a detected output as shown in is obtained.
By inputting the detected output proportional to the noise power thus obtained from the detector 6 to the on-screen indication circuit 8 and superposing it on the video signal, the indication of the amount proportional to the CN ratio can be displayed on superposed on TV picture on the screen of the TV receiver 9. Hereupon, as an Indication scheme on the picture screen, the bar indication on the TV picture, for example, as shown in FIG.8 may be employed. For example, the scheme of the bar indication to represent the CN ratio is such that the ‘4 It 4 t -r -L -Ir -Cnum;ber of white bars increases as the picture quality increases up to a maximum number of e.g. 32 bars for the highest quality.
And, if the detected output is indicated by a voltmeter, it can also be utilized for the BS antenna pointing angle adjustment.
[Second Embodiment] Next, on a second embodiment of the present invention, explanation i-i given with referring to the drawings. FIG.9 is a block diagram of a satellite broadcasting receiver picture quality indicator of the second embodiment of the present invention. Corresponding parts and components to the first embodiment are shown by tihe same numerals and marks, and the description thereon made in the first embodiment similarly apply. Differences and features of this second embodiment from the first embodiment are as follows. In FIG.9, differences from the first embodiment of FIG.l are those points that an amplifier 51 having no amplitude limiting function is employed as the amplifier for amplifying the output of a BPF 4, and an amplifier 52 having a nonlinear amplification function is added to the output side of the detector 6, then thereafter its output is connected to an on-screen indication circuit 8.
Operation of the satellite broadcasting receiver picture quality indicator constituted as described above i i is explained below. Since up to the extraction of the noise component by the BPF 4, its operation is the same as in the first embodiment, explanation for this part is omitted here. Different from the first embodiment, as for the amplifier 51, since an amplifier without having the amplitude limiting function is employed, when the CN ratio Is changed, the detected output of the detector 6 increases sharply where the CN ratio becomes below 9 dB, as is shown in FIG.4. If the output is directly displayed on the TV receiver 9 through the indication means 10, the linearity of the indicated output for the change of the CN ratio is not good, and a range which can be indicated is limited. The example of FIG.10 is for improving such problem of poor lineality. That is, by letting the amplifier 52 provided at the output side of the detector 6, an input-output characteristic is obtained that the gain is boosted while the input is small, whereas it becomes relatively suppressed when the input becomes S large, so that the linearity of output of the amplifier 52 for the CN ratio is improved as shown in FIG.11.
The amplifier having an input-output characterstic as shown in FIG.10 can be realized by a circuit including an operational amplifier as shown in FIG.12.
Therein, R 1 1
R
1 2
R
1 3 and R14 are bias resistors of an operational amplifier 53 and they determine the bias voltages with the help of a voltage source 54 and a Zener 17 0 r7 i diode 55. The input-output characteristic or this amplifier can be expressed by the following equation; when
V
0
V
1
V
z
R
2
VR
2
V
0 1 1 V 2 (3) RI RI and when 0 V-vl V z,
R
2 1 R 2 Vo=(+R )V R3 RV 2 V z 1+ 2) R R2 R2 1+ 3 1+1+-
R
3
R
3
R
3 As is understood from the above equation, when the InpUt voltage V 1 is small and a difference with respect to the output voltage V 0 is smaller than the Zener voltage V z the Zener diode is not In the conductive state. Hence, the input-output characteristic is Iiexpressed by whereas, when the input voltage V 1 becomes large and a difference with respect the output voltage V 0 becomes large and the Zener diode becomes conductive state, the input-output characteristic becomes to be expressed by and thus the gain decreases.
By inputting the output of the mplifier 52 thus obtained into the on-screen indication circuit 8 and thus superposing it on the video signal, it becomes possible to indicate the value corresponding to the CN ratio on the 18 i* screen of the TV receiver 9.
As has been describes above, in the present invention, by extracting the noise component from the FM demodulated output and by detecting it, the output proportional to the noise pov’er is obtained, and by indicating it as the CN ratio, it can be used for the purpose of the antenna pointing angle adjustment, and also the picture quality indication for the satellite broadcasting receiver becomes possible, hence its practical usefulness is large.
Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be resorted I to without departing from the spirit and the scope of the invention as hereinafter claimed.
I19

Claims (3)

2. Picture quality indicator for satellite broadcasting receiver stated in I claim 1, whex~ein said band-pass filter has a characteristic which passes only the noise component which include no video luminance signal component, no color sub-carrier nor its second, third hrnic components, no audio sub-carrier component nor its harmonic components.

3. Picture quality indicator for satellite broadcasting receiver stated in claim 1, wherein the amplifier amplifying the noise component is an amplitude-limiting type amplifier wherein the amplification gain docreases as the noise level increases.

4. Picture quality indicator for satellite broadcasting receiver comprising: an FM-demodulator for demodulating a satellite broadcasting signal comprising TV signals, a band-pass filter adapted to remove the TV signals by passing only a demodulated noise component at frequency bands outside the spectrum of the TV signals, a first amplifier for amplifying said noise component, a detection circuit for detecting the amount of said II 21 noise component output from said amplifier, and a second amplifier for amplifying the output of said detection circuit, said second amplifier having variable gain characteristic such that the gain thereof decreases as the input thereto increases, and a level indicator for indicating the figure of merit (or picture quality factor) of received picture quality in relation to the output level of said second amplifier. A picture quality indicator for satellite broadcasting substantially as hereinbefore described with reference to the drawings. ‘1j 14 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 36 38 DATED THIS 23rd March, 1990 DAVIES COLLISON Fellows Institute of Patent Attorneys of Australia. Patent Attorneys for the Applicant 900323,c-dat.075, shita.j,2j

AU27586/88A
1987-12-29
1988-12-23
Picture quality indicator for satellite broadcasting receiver

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Application Number
Priority Date
Filing Date
Title

JP62334535A

JPH01175487A
(en)

1987-12-29
1987-12-29
Satellite television receiver picture quality display device

JP62-334535

1987-12-29

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AU2758688A

AU2758688A
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1989-06-29

AU602279B2
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1990-10-04

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1987-12-29
1988-12-23
Picture quality indicator for satellite broadcasting receiver

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US4935814A
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EP0322789B1
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JP
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KR920010036B1
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US5287187A
(en)

1989-05-15
1994-02-15
Canon Kabushiki Kaisha
Video signal processing apparatus displaying image and process information

GB8928539D0
(en)

1989-12-18
1990-02-21
Thomson Consumer Electronics
Segmented bar display for a programmable tuner

GB8928551D0
(en)

1989-12-18
1990-02-21
Thomson Consumer Electronics
Band indicative segmented tuning bar display

JP3013408B2
(en)

1990-08-17
2000-02-28
ソニー株式会社

Receiver

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active
Granted

1988

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CA
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patent/CA1293798C/en
not_active
Expired – Lifetime

1988-12-22
KR
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patent/KR920010036B1/en
not_active
IP Right Cessation

1988-12-23
EP
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Expired – Lifetime

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AU
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Ceased

1988-12-23
DE
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not_active
Expired – Fee Related

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US
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patent/US4935814A/en
not_active
Expired – Fee Related

Also Published As

Publication number
Publication date

DE3850950D1
(en)

1994-09-08

EP0322789B1
(en)

1994-08-03

JPH01175487A
(en)

1989-07-11

CA1293798C
(en)

1991-12-31

AU2758688A
(en)

1989-06-29

EP0322789A1
(en)

1989-07-05

JPH0566078B2
(en)

1993-09-21

KR890011401A
(en)

1989-08-14

KR920010036B1
(en)

1992-11-13

US4935814A
(en)

1990-06-19

DE3850950T2
(en)

1994-12-15

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