Multiple use digital transmitter/transceiver with time multiplexing

• US 5,220,557 A
• Filed: 09/23/1991
• Issued: 06/15/1993
• Est. Priority Date: 09/23/1991
• Status: Expired due to Fees

• Current Assignee: Microelectronics Technology Inc (MTI Laboratory Inc)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Kelley, Edwin A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): BLUM, RUSSELL
• Application Number:
  US07/765,157
• Time in Patent Office: 631 Days
• Field of Search: 370/11, 370/50, 370/70, 375/7, 375/60, 375/61, 455/73, 455/84, 455/103
• US Class Current: 370/345
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A digital transmitter/transceiver accommodates multiple simultaneous receiver and transmitter channels by time division multiplexing the tuning and modulation hardware. Only a single digital-to-analog converter is required for multiple channel transmission, and time multiplexing permits the use of only a single set of digital hardware.

Claims

1. A multiple use radio frequency (RF) transmitter, comprising:

means for generating a plurality of different digital information signals.

separating said digital information signals by time multiplexing,

means for generating respective digital carrier signals for said information signals, said carrier signals having higher frequencies than their respective information signals,

means for modulating said digital carrier signals with their respective digital information signals,

means for accumulating said modulated signals to a composite digital signal,

digital-to-analog converter (DAC) means common to each of said modulated signals for converting said composite digital signal to composite signal in analog format,

means for altering the frequency of said composite signal to a desired radio frequency (RF) band, and

means for excluding frequencies outside said desired RF band from said composite signal.

2. The multiple use RF transmitter of claim 1, said digital information and digital carrier signal generating means generating their respective signals on a time multiplexed basis, said modulating means operating on a time multiplexed basis to produce a plurality of time multiplexed modulated signals, and said accumulating means accumulating said time multiplexed modulated signals to a simultaneous time basis.

3. The multiple use RF transmitter of claim 2, wherein said frequency altering means comprises an analog frequency upconverter that is connected to operate upon the output and said DAC.

4. The multiple use RF transmitter of claim 2, said digital information signal generating means comprising a digital signal processor for generating baseband digital information signals, finite impulse response (FIR) filter means for generating higher frequency images of said baseband signals, and means for selecting a desired image signal for each information signal for modulating a respective carrier signal.

5. The multiple use RF transmitter of claim 4 said FIR filter means comprising a single FIR filter that is common to each of said digital information signals, said FIR filter operating at the data rate of said baseband digital information signals multiplied by the number of said signals.

6. The multiple use RF transmitter of claim 4, said means for selecting a desired one of said images comprising an interpolating filter.

7. The multiple use RF transmitter of claim 1, said means for altering the frequency of said composite signal comprising means for increasing the sampling rate of said signal and thereby producing higher frequency images of said signal.

8. The multiple use RF transmitter of claim 7, said means for altering the frequency of said composite signal comprising a finite impulse response (FIR) filter.

9. The multiple use RF transmitter of claim 7, said means for increasing the sampling rate of said composite signal assigning a zero value to the added samples.

10. The multiple RF transmitter of claim 7, said means for excluding frequencies outside of said desired RF band from said composite signal comprising an analog bandpass filter tuned to said desired RF band.

11. A multiple use radio frequency (RF) transmitter, comprising:

means for generating a plurality of different digital information signals comprising a digital signal processor for generating baseband digital information signals, means for generating higher frequency images of said baseband signals, and means for selecting a desired image signal for each information signal for modulating a respective carrier signal.

means for generating respective digital carrier signals for said information signals, said carrier signals having higher frequencies than their respective information signals,

means for modulating said digital carrier signals with their respective digital information signals.

means for accumulating said modulated signals to a composite digital signal,

digital-to-analog converter (DAC) means common to each of said modulated signals for converting said composite digital signal to a composite signal in analog format,

means for altering the frequency of said composite signal to a desired radio frequency (RF) band, and

means for excluding frequencies outside said desired RF band from said composite signal.

12. The multiple use RF transmitter of claim 11, said means for generating higher frequency images of said baseband signals comprising means for increasing the sampling rates of said baseband signals.

13. The multiple use RF transmitter of claim 12, said means for increasing the sampling rates of said baseband signals assigning a zero value to the added samples.

14. The multiple use RF transmitter of claim 12, said means for generating higher frequency images of said baseband signals comprising finite impulse response (FIR) filter means.

15. A multiple use radio frequency (RF) transmitter, comprising:

means for generating a plurality of different digital information signals,

means for generating respective digital carrier signals for said information signals, said carrier signals having higher frequencies than their respective information signals,

means for modulating said digital carrier signals with their respective digital information signals.

means for accumulating said modulated signals to a composite digital signal,

digital-to-analog converter (DAC) means common to each of said modulated signals for converting said composite digital signal to composite signal in analog format.

a finite impulse response (FIR) filter for altering the frequency of said composite signal and means for increasing the sampling rate of said signal and thereby producing higher frequency images of said signal, and

means for excluding frequencies outside said desired RF band from said composite signal.

16. The multiple use RF transmitter of claim 15, said means for generating higher frequency images of said baseband signals further comprising an x/sinx predistortion filter for compensating sinx/x distortion in the FIR filter means.

17. A multiple use radio frequency (RF) transmitter, comprising:

means for generating a plurality of time multiplexed digital information signals,

means for generating digital carrier signals for said information signals on a time multiplexed basis in synchronism with the multiplexing of said digital information signals,

means for digitally modulating said digital carrier signals with respective digital information signals,

digital-to-analog converter means common to each of said modulated signals for converting said modulated carrier signals to analog format, and

means for altering the frequency of said modulated signals to a desired RF band.

18. A multiple use radio frequency (RF) transmitter, comprising:

means for generating a plurality of time multiplexed digital information signals,

means for generating digital carrier signals for said information signals,

means for digitally modulating said digital carrier signals with their respective digital information signals,

digital-to-analog converter means common to each of said modulated signals for converting said modulated carrier signals to analog format, and

FIR filter means for increasing the sampling rate of said modulated signals and thereby producing higher frequency images of said signals.

19. A multiple use radio frequency (RF) transceiver comprising:

means for generating a plurality of different digital information signals,

means for digitizing received analog RF signals,

means for generating digital carrier signals for said information signals and digital tuner signals for said digitized RF signals,

digital modulator means for digitally modulating said digital carrier signals with respective digital information signals and for extracting desired frequencies from said digitized RF signals with said tuner signals,

means for providing reception outputs from said extracted frequencies of said digitized RF signals,

digital-to-analog converter (DAC) means common to each of said modulated digital signals for converting said signals to analog format, and

means for altering the frequency of said modulated signals to a desired RF band.

20. The multiple use RF transceiver of claim 19, further comprising digital means for time multiplexing said digital information signals together with said digitized received RF signals for presentation of said digital modulator means as a composite signal, and time demultiplexing means for separating said modulated digital carrier signals from the extracted frequencies of said digitized RF signals.

21. The multiple use RF transmitter of claim 20, said means for providing reception outputs including digital finite impulse response (FIR) filter means and digital interpolation filter means functioning to reduce the sampling rate for said extracted frequencies, and further functioning as frequency multipliers for said digital information signals.

22. The multiple use RF transmitter of claim 21, said time multiplexing means comprising first multiplexing means for time multiplexing said digital information signals together and second multiplexing means for time multiplexing the multiplexed digital information signals together with said digitized received rF signals.

23. The multiple use RF transmitter of claim 22, said time demultiplexing means comprising first demultiplexing means for separating said modulated digital carrier signals from the extracted frequencies of said digitized RF signals, and second demultiplexing means for separating the extracted frequencies of said digitized RF signals.

24. The multiple use RF transmitter of claim 20, including a digital signal processor (DSP) for generating said digital information signals, said DSP controlling the assignment of said time multiplexing and demultiplexing means to said digital information signals and said digitized received RF signals.