EP0320641A2
Expired / Lapsed
EP
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Device for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator
Assignee: STMicroelectronics SRL
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Filing: 1988-11-18
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Granted: —
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Expires: 2008-11-18
Abstract
Abstract A method, and related device, for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator (2), which has an output (13) for the demodulated signal and a so-called standard selecting input pin (12), consists of detecting the polarity of the demodulated signal at the output (13) of the demodulator (2) and comparing that polarity with the polarity of the input signal to the demodulator (2). The voltage value on the standard selecting pin (12) is changed over on detecting a different modulation polarity between the input and output video signals to/from the demodulator (2) to enable the latter to operate to the correct standard at all times.
Inventors
- 👤 Maurizio Zuffada
- 👤 Fabrizio Sacchi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 20:33
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/46
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
102 words
A method for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator (2) having an output (13) for the demodulated signal and an input pin (12), commonly referred to as the standard selecting pin, characterized in that it comprises the steps of: detecting the polarity of the demodulated signal at the demodulator (2) output (13); comparing that polarity with the polarity of the input signal to the demodulator; and changing the voltage value at the standard selecting pin (12) on a different polarity being detected between the input signal and the output signal to/from the demodulator.
Claim 2
Independent Claim
102 words
A method for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator (2) having an output (13) for the demodulated signal and an input pin (12), commonly referred to as the standard selecting pin, characterized in that it comprises the steps of: detecting the polarity of the demodulated signal at the demodulator (2) output (13); comparing that polarity with the polarity of the input signal to the demodulator; and changing the voltage value at the standard selecting pin (12) on a different polarity being detected between the input signal and the output signal to/from the demodulator.
Claim 3
Dependent Claim
88 words
A method according to Claim 1, characterized in that said polarity detecting step consists of picking up the demodulated signal from said output (13), applying that signal to the input (16) of a regenerated circuit (18) having a second input (17) connected to a positive supply pole (VC) and being adapted to charge a capacitor (C), applying the voltage value (V CD ) across said capacitor (C) to one input of an operational amplifier (A2) having the other input connected to a reference voltage pole (V R ).
Claim 4
Independent Claim
61 words
A method according to Claims 1 and 2, characterized in that said polarity comparing step is effected by applying the signal at the output (U2) of said operational amplifier (A2) to the input of a flip-flop type of storage cell (25) whose output (Q) is linked operatively to a second input (P) adapted to receive a step pulse of predetermined duration.
Claim 5
Independent Claim
32 words
A method according to the preceding claims, characterized in that said voltage value changing step is linked operatively to the logic voltage value at the output (Q) of said storage cell (25).
Claim 6
Independent Claim
167 words
A device (1) for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator (2) having an output (13) for the demodulated signal and an input pin (12) commonly referred to as the standard selecting pin, characterized in that it comprises: a regenerated circuit (18) having first (16) and second (17) inputs respectively connected to a positive supply pole (VC) and the demodulator (2) output (16), said circuit (18) having an output connected to one end of a capacitor (C) having the other end grounded; an operational amplifier ((A2) having the inverting (-) input connected to a positive voltage reference pole (VR) and the non-inverting (+) input connected to said capacitor (C); and a storage cell (25) having a first input (T) connected to the output (U2) of said amplifier (A2) and a second or preset input (P) adapted to receive a step pulse of predetermined duration; said storage cell (25) having an output (Q) connected to said standard selecting pin (12).
Claim 7
Independent Claim
167 words
A device (1) for automatically selecting the demodulation standard of a video signal, useful with an intermediate frequency demodulator (2) having an output (13) for the demodulated signal and an input pin (12) commonly referred to as the standard selecting pin, characterized in that it comprises: a regenerated circuit (18) having first (16) and second (17) inputs respectively connected to a positive supply pole (VC) and the demodulator (2) output (16), said circuit (18) having an output connected to one end of a capacitor (C) having the other end grounded; an operational amplifier ((A2) having the inverting (-) input connected to a positive voltage reference pole (VR) and the non-inverting (+) input connected to said capacitor (C); and a storage cell (25) having a first input (T) connected to the output (U2) of said amplifier (A2) and a second or preset input (P) adapted to receive a step pulse of predetermined duration; said storage cell (25) having an output (Q) connected to said standard selecting pin (12).
Claim 8
Dependent Claim
82 words
A device according to Claim 5, characterized in that said regenerated circuit (18) comprises an operational amplifier (A1) having the non-inverting (+) input connected to the demodulator (2) output (13) and the inverting (-) input and output (U1) respectively connected to the emitter (ES) and the base (DS) of a pnp transistor with a grounded collector (CS), said emitter (ES) being also connected to a positive supply pole (VC) via a current source (IC) and to one end of said capacitor (C).
Claim 9
Dependent Claim
26 words
A device according to Claim 5, characterized in that a low-pass filter (15) is provided between said regenerated circuit (18) and the demodulator (2) output (13).
Claim 10
Dependent Claim
57 words
A device according to Claim 5, characterized in that the output (Q) of said storage cell (25) is connected to the base (B1) of an npn transistor (T1) having the emitter (E1) grounded and the collector (C1) connected both to a positive pole (VC) via a resistor (R) and to said pin (12) of the demodulator (2).
References Cited (Backward Citations)
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