Mobile terminal apparatus and method for a satellite communication system

• US 5,742,639 A
• Filed: 10/13/1994
• Issued: 04/21/1998
• Est. Priority Date: 05/13/1994
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Anderson, Samuel S., Cammarata, Denise M., Janson, Keith W., Stehlik, Roy, Fasulo, Albert J. II, Cooper, Raymond R.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US08/322,858
• Time in Patent Office: 1,286 Days
• Field of Search: 375/219, 375/220, 375/222, 375/279, 375/324, 375/340, 332/103, 455/73, 455/12
• US Class Current: 375/219
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 1/403 using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations
• CPC Class Codes: H04B 7/18571 for satellites; for fixed or mobile stations

Abstract

A mobile terminal apparatus for satellite communication of voice data, facsimile and computer information, which consists of an RF transceiver section, an optional cellular board, and a processor board. The processor board has two digital signal processors and a multi-task control processor for controlling the operation of the signal processor.

Claims

1. A mobile terminal apparatus having a transceiver with a user interface, and an antenna for both radiating and collecting RF signals to and from a satellite, the transceiver, comprising:

an RF section coupled to the antenna and a processor board coupled to the RF section and the user interface;

the RF section including

a low noise amplifier and a high power amplifier coupled to the antenna,

a down converter coupled to the low noise amplifier for converting received RF signal waveforms to IF waveforms,

an up converter coupled to the high power amplifier for converting modulated analog waveforms from an IF to an RF frequency for amplification and transmission to the antenna;

a first analog to digital converter having an input connected to the down converter, for converting the analog IF waveform to a series of digital samples;

a first digital to analog converter connected to the up converter for converting modulated digital samples from the processor board to an IF frequency;

the processor board including

a signal processor including a digitally implemented demodulator function, a digitally implemented modulator function, a digitally implemented receive framing function coupled to the demodulator, a digitally implemented transmit framing function coupled to the modulator, and a digitally implemented coding function and decoding function coupled to the transmit and receive framing functions, respectively; and

a control processor coupled to the signal processor for controlling the digitally implemented functions;

wherein the receive framing function includes means for using unique words to frame transmitted informational data and to define data synchronization points.

2. The apparatus of claim 1 wherein the signal processor comprises a first signal processor unit that includes the demodulator function, the receive framing function, the modulator function, and the transmit framing function;

and

a second signal processor unit including the decoding and encoding function.

3. The apparatus of claim 1 wherein the digital signal processor comprises means for operating in the voice mode, means for operating in the facsimile and data modes, and means for operating in the signalling and packet switch modes.

4. A mobile terminal apparatus having a transceiver with a user interface, and an antenna for both radiating and collecting RF signals to and from a satellite, the transceiver, comprising:

an RF section coupled to the antenna and a processor board coupled to the RF section and the user interface;

the RF section including

a low noise amplifier and a high power amplifier coupled to the antenna,

a down converter coupled to the low noise amplifier for converting received RF signal waveforms to IF waveforms,

an up converter coupled to the high power amplifier for converting modulated analog waveforms from an IF to an RF frequency for amplification and transmission to the antenna;

a first analog to digital converter having an input connected to the down converter, for converting the analog IF waveform to a series of digital samples;

a first digital to analog converter connected to the up converter for converting modulated digital samples from the processor board to an IF frequency;

the processor board including

a signal processor including a digitally implemented demodulator function, a digitally implemented modulator function, a digitally implemented receive framing function coupled to the demodulator, a digitally implemented transmit framing function coupled to the modulator, and a digitally implemented coding function and decoding function coupled to the transmit and receive framing functions, respectively;

a control processor coupled to the signal processor for controlling the digitally implemented functions;

wherein the transmit framing function comprises voice activation and deactivation logic for turning on and off the transmitted carrier when the user is talking or silent; and

means for maintaining the satellite frame timing during both talking and silence.

5. A mobile terminal apparatus having a transceiver with a user interface, and an antenna for both radiating and collecting RF signals to and from a satellite, the transceiver, comprising:

an RF section coupled to the antenna and a processor board coupled to the RF section and the user interface;

the RF section including

a low noise amplifier and a high power amplifier coupled to the antenna,

a down converter coupled to the low noise amplifier for converting received RF signal waveforms to IF waveforms,

an up converter coupled to the high power amplifier for converting modulated analog waveforms from an IF to an RF frequency for amplification and transmission to the antenna;

a first analog to digital converter having an input connected to the down converter, for converting the analog IF waveform to a series of digital samples;

a first digital to analog converter connected to the up converter for converting modulated digital samples from the processor board to an IF frequency;

the processor board including

a signal processor including a digitally implemented demodulator function, a digitally implemented modulator function, a digitally implemented receive framing function coupled to the demodulator, a digitally implemented transmit framing function coupled to the modulator, and a digitally implemented coding function and decoding function coupled to the transmit and receive framing functions, respectively;

a control processor coupled to the signal processor for controlling the digitally implemented functions;

wherein the transmit framing comprises means for reordering in time a time ordered series of transmit bytes or a packet of data; and

means for the forward error correction of data in accordance with a constraint length convolutional coding of either one-half, one-third, or three-quarters coding.

6. In a mobile terminal apparatus for a satellite communications network where the mobile terminal unit has a transceiver with an RF section and a digital signal processing section, a method of processing RF signals received by the transceiver comprising

down converting the received RF signals to an IF frequency;

sampling digitally the IF frequency;

demodulating the digital samples;

framing the digital samples in accordance with a unique word;

decoding the framed samples;

feeding the decoded frames to a digital to analog converter;

operating a user device in accordance with the converted signals;

wherein the step of framing the digital samples comprises the substeps of using the unique words as data synchronization points;

recovering informational data embedded in a satellite frame format;

maintaining real time frame timing in accordance with the satellite frame format;

descrambling randomized data; and

recovering the original byte order of interleaved data bytes.

7. In a mobile terminal apparatus for a satellite communications network where the mobile terminal unit has a transceiver with an RF section and a digital signal processing section, a method of processing RE signals received by the transceiver comprising

down converting the received RF signals to an IF frequency;

sampling digitally the IF frequency;

demodulating the digital samples;

framing the digital samples in accordance with a unique word;

decoding the framed samples;

feeding the decoded frames to a digital to analog converter; and

operating a user device in accordance with the converted signals;

wherein the step of demodulating comprises the substeps of

mixing a sampled real IF signal to form an IQ baseband signal,

performing fast fourier transforms to identify the signal carrier frequency,

tracking the identified carrier frequency;

tracking the timing of incoming signals to be demodulated;

detecting symbols by matched filtering;

differentially encoding the detected symbols;

and computing the signals strength of the demodulated signals.

8. In a mobile terminal apparatus for a satellite communications network where the mobile terminal unit has a transceiver with an RF section and a digital signal processing section, a method of processing RF signals received the transceiver comprising

down converting the received RF signals to an IF frequency;

sampling digitally the IF frequency;

demodulating the digital samples;

framing the digital samples in accordance with a unique word;

decoding the framed samples;

feeding the decoded frames to a digital to analog converter;

operating a user device in accordance with the converted signals;

modulating an encoded digital data stream by quaternary phase shift keying the digital transmit data stream to produce an ideal IQ modulated baseband signal; and

performing a 60% root cosine filtering of the quaternary phase shift keying modulated baseband signal.