Apparatus for adapting computer for satellite communications

• US 5,019,910 A
• Filed: 09/12/1988
• Issued: 05/28/1991
• Est. Priority Date: 01/29/1987
• Status: Expired due to Term

• Current Assignee: Norsat International Incorporated (Hytera Communications Corp. Ltd.)
• Original Assignee: Norsat International Incorporated (Hytera Communications Corp. Ltd.)
• Inventors: Filmer, Donald D.
• Primary Examiner(s): Chin, Tommy P.
• Application Number:
  US07/243,598
• Time in Patent Office: 988 Days
• Field of Search: 358/188, 358/185, 358/83, 358/143, 358/149, 358/903, 358/194.1, 358/191.1, 358/195.1, 455/12, 455/13, 455/179, 455/182, 455/183, 455/185, 455/186, 455/158
• US Class Current: 725/68
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations

Abstract

Computer controllable apparatus for receiving and demodulating a satellite broadcast signal. A programmable radio frequency tuner/demodulator demodulates the broadcast signal to produce a baseband output signal. A video demodulator then demodulates the baseband output signal to produce a video output signal. First and second programmable audio frequency tuner/demodulators further demodulate the baseband output signal to produce first and second audio output signals. A data demodulator further demodulates the second audio output signal to produce a data output signal.

Claims

1. Apparatus for receiving and demodulating a satellite broadcast signal, comprising:

(a) programmable radio frequency tuner/demodulator means for demodulating said broadcast signal to produce a baseband output signal;

(b) addressable storage means for storing tuning data representative of one or more tuning frequencies;

(c) data receptor means for receiving address data from an external source;

(d) control means for;

(i) coupling to said data receptor means and decoding said address data to produce an address of a corresponding storage location within said storage means;

(ii) extracting said tuning data from said corresponding storage location; and

,

(iii) programming said radio frequency tuner/demodulator means with said tuning data; and

,

(e) video demodulator means for demodulating said baseband output signal to produce a video output signal, said video demodulator means comprising;

(i) first deemphasis means for deemphasizing said baseband output signal;

(ii) low pass filter means for low pass filtering said deemphasized baseband output signal;

(iii) first amplifier means for amplifying said filtered, deemphasized baseband output signal;

(iv) first polarity switching means for controllably switching the polarity of said amplified, filtered, deemphasized baseband output signal; and

,

(v) clamping means for removing dispersion from said amplified, filtered, deemphasized baseband output signal.

2. Apparatus as defined in claim 1, wherein said video demodulator means is further for demodulating said baseband output signal to produce an unclamped, unfiltered baseband output signal, and further comprises:

(a) second deemphasis means for deemphasizing said baseband output signal;

(b) second amplifier means for amplifying the deemphasized baseband signal output by said second deemphasis means; and

,

(c) second polarity switching means, coupled to said first polarity switching means, for controllably switching the polarity of the amplified, deemphasized baseband signal output by said second amplifier means to produce said unclamped, unfiltered, baseband output signal.

3. Apparatus as defined in claim 1, wherein said video demodulator means is further for demodulating said baseband output signal to produce an unclamped, unfiltered baseband output signal, and further comprises:

(a) second deemphasis means for deemphasizing said baseband output signal;

(b) second amplifier means for amplifying the deemphasized baseband signal output by said second deemphasis means; and

,

(c) second polarity switching means, coupled to said first polarity switching means, for controllably switching the polarity of the amplified, deemphasized baseband signal output by said second amplifier means to produce said unclamped, unfiltered, baseband output signal;

and wherein said control means is further for;

(d) receiving polarity switching data from said external source; and

,

(e) transmitting said polarity switching data to said first and second polarity switching means, thereby causing the polarity of said video output signal and the polarity of said unclamped, unfiltered, baseband output signal to adopt a state represented by said polarity switching data.

4. Apparatus for receiving and demodulating a satellite broadcast signal, comprising:

(a) programmable radio frequency tuner/demodulator means for demodulating said broadcast signal to produce a baseband output signal;

(b) addressable storage means for storing tuning data representative of one or more tuning frequencies;

(c) data receptor means for receiving address data from an external source;

(d) control means for;

(i) coupling to said data receptor means and decoding said address data to produce an address of a corresponding storage location within said storage means containing first audio tuning data for tuning said first frequency audio tuner/demodulator means;

(ii) extracting said first audio tuning data from said corresponding storage location;

(iii) programming said first audio frequency tuner/demodulator means with said first audio tuning data; and

,

(e) first programmable audio frequency tuner/demodulator means for demodulating said baseband output signal to produce a first audio output signal, said first programmable audio frequency tuner/demodulator means further comprising;

(i) first voltage controlled oscillator means for producing a first local oscillator output signal having a frequency determined by an input reference signal;

(ii) first reference oscillator means for producing a first fixed frequency reference output signal;

(iii) first programmable divider means for receiving said first audio tuning data and for dividing said first local oscillator output signal by an amount determined by said first audio tuning data;

(iv) first programmable reference divider means for receiving said first audio tuning data and for dividing said first fixed reference frequency output signal by an amount determined by said first audio tuning data;

(v) first comparator means for comparing the frequency of signals output by said first programmable divider means with the frequency of signals output by said first programmable reference divider means and for producing an output signal representative of the difference between said signal frequencies, said difference comprising said first voltage controlled oscillator input reference signal;

(vi) signal mixing means for mixing said baseband output signal with said local oscillator output signal to produce an intermediate frequency output signal;

(vii) first bandpass filter means for bandpass filtering said intermediate frequency output signal to produce a filtered intermediate frequency output signal;

(viii) first switchable bandpass filter means for bandpass filtering said intermediate frequency output signal within a narrow frequency pass band to produce a narrowly filtered intermediate frequency output signal;

(ix) second switchable bandpass filter means for bandpass filtering said intermediate frequency output signal within a wide frequency pass band to produce a widely filtered intermediate frequency output signal; and

,

(x) filter switching means for controllably actuating one or the other of said first and second switchable bandpass filter means.

5. Apparatus as defined in claim 4, wherein said control means is further for:

(a) receiving filter switching data from said external source; and

,

(b) transmitting said filter switching data to said filter switching means, thereby actuating one or the other of said first and second switchable bandpass filters.

6. Apparatus for receiving and demodulating a satellite broadcast signal, comprising:

(a) programmable radio frequency tuner/demodulator means for demodulating said broadcast signal to produce a baseband output signal;

(b) addressable storage means for storing tuning data representative of one or more tuning frequencies;

(c) data receptor means for receiving address data from an external source;

(d) control means for;

(i) coupling to said data receptor means and decoding said address data to produce an address of a corresponding storage location within said storage means;

(ii) extracting said tuning data from said corresponding storage location; and

,

(iii) programming said radio frequency tuner/demodulator means with said tuning data;

(e) first programmable audio frequency tuner/demodulator means for demodulating said baseband output signal to produce a first audio output signal;

(f) second programmable audio frequency tuner/demodulator means for demodulating said baseband output signal to produce a second audio output signal;

(g) data demodulator means for demodulating said second audio output signal to produce a data output signal said data demodulator means further comprising;

(i) first amplifier means for amplifying said second audio output signal to produce an amplified replica thereof;

(ii) voltage level shifting means for shifting the voltage level of said amplified replica signal; and

,

(iii) comparator means for comparing the width of signal pulses output by said voltage level shifting means with a reference pulse width and for adjusting the width of said signal pulses to equal said reference pulse width.