Composite BPSK/AM-BPSK based spectral suppression of out-of-band energy from saturated RF amplifier

• US 6,721,369 B1
• Filed: 11/09/1999
• Issued: 04/13/2004
• Est. Priority Date: 11/09/1998
• Status: Expired due to Term

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Belcher, Donald K., Hash, Ronald J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): ODOM, CURTIS B
• Application Number:
  US09/436,551
• Time in Patent Office: 1,617 Days
• Field of Search: 375/296, 375/260, 455/108, 341/152, 330/10
• US Class Current: 375/296
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 27/08 Amplitude regulation arrangements
• CPC Class Codes: H04L 27/20 Modulator circuits; Transmitter circuits

Abstract

An amplitude modulation (AM) based mechanism controllably alters the shape of a binary phase shift keyed (BPSK) digital spreading waveform modulated onto an RF carrier. The modulated RF carrier is amplified by a saturated RF amplifier. The spectral properties of the amplified AM-BPSK waveform, when combined with the spectral properties of a BPSK waveform modulated onto the RF carrier and amplified by another saturated RF amplifier, produces a composite BPSK-modulated RF waveform containing substantially suppressed sidelobes.

Claims

1. A method of amplifying a modulated radio frequency (RF) carrier waveform for RF transmission, said modulated RF carrier waveform containing transitions between first and second states comprising:

(a) providing amplifier circuitry that is operative to amplify said modulated RF carrier waveform applied thereto for RF transmission; and

(b) modifying the shape of said transitions of said modulated RF carrier waveform in a manner that is effective to substantially suppress energy content of spectral sidelobes outside an intended limited bandwidth of said amplifier circuitry upon RF transmission.

2. A method according to claim 1, step (a) comprises operating said amplifier circuitry in its saturation region.

3. A method according to claim 2, wherein said modulated RF carrier waveform comprises a binary phase shift keyed (BPSK) digital spreading waveform modulated onto an RF carrier.

4. A method according to claim 3, wherein step (b) comprises:

(b1) modulating said BPSK waveform onto said RF carrier to produce a BPSK-modulated RF carrier waveform, said BPSK-modulated RF carrier waveform being amplified by an associated RF amplifier operating in its saturation region to produce an amplified BPSK-modulated RF carrier waveform,

(b2) amplitude-modulating transition regions of said BPSK waveform to produce an amplitude modulated (AM)-BPSK waveform,

(b3) modulating said AM-BPSK waveform onto said RF carrier to produce an AM-BPSK modulated RF carrier waveform, said AM-BPSK modulated RF carrier waveform being amplified by an associated RF amplifier operating in its saturation region to produce an amplified AM-BPSK modulated RF carrier waveform, and

(b4) combining said amplified BPSK-modulated RF carrier waveform produced in step (b1) with said amplified AM-BPSK modulated RF carrier waveform produced in step (b3) to produce a modulated RF carrier waveform having a composite spectral characteristic in which energy content of spectral sidelobes is suppressed.

5. A method according to claim 4, wherein step (b2) comprises amplitude-modulating said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

6. A method according to claim 4, wherein step (b2) comprises reducing the amplitude of said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

7. An apparatus for amplifying a modulated radio frequency (RF)carrier waveform for RF transmission, said modulated RF carrier waveform containing transitions between first and second states comprising:

amplifier circuitry that is operative to amplify said modulated RF carrier waveform applied thereto for RF transmission; and

a modulator that is operative to modify the shape of said transitions of said modulated RF carrier waveform in a manner that is effective to substantially suppress energy content of spectral sidelobes outside an intended limited operational bandwidth of said amplifier circuitry upon RF transmission.

8. An apparatus according to claim 7, wherein said amplifier circuitry is operated in its saturation region.

9. An apparatus according to claim 8, wherein said modulated RF carrier waveform comprises a binary phase shift keyed (BPSK) digital spreading waveform modulated onto an RF carrier.

10. An apparatus according to claim 9, wherein said modulator comprises a first modulator that is operative to modulate said BPSK waveform onto said RF carrier to produce a BPSK-modulated RF carrier waveform, and wherein said amplifier circuitry includes a first RF amplifier operating in its saturation region, and being coupled to amplify said BPSK-modulated RF carrier waveform to produce an amplified BPSK-modulated RF carrier waveform, a second modulator that is operative to amplitude-modulate transition regions of said BPSK waveform to produce an amplitude modulated (AM)-BPSK waveform, a third modulator that is operative to modulate said AM-BPSK waveform onto said RF carrier to produce an AM-BPSK modulated RF carrier waveform, and a second RF amplifier operating in its saturation region and being operative to amplify said AM-BPSK modulated RF carrier waveform to produce an amplified AM-BPSK modulated RF carrier waveform, and further including a combiner which is operative to combine said amplified BPSK-modulated RF carrier waveform with said amplified AM-BPSK modulated RF carrier waveform to produce a composite modulated RF carrier waveform having a spectral characteristic in which energy content of spectral sidelobes is suppressed.

11. An apparatus according to claim 10, wherein said second modulator is operative to amplitude-modulate said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

12. An apparatus according to claim 10, wherein said second modulator is operative to reduce the amplitude of said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

13. An apparatus comprising:

a first modulator that is operative to modulate a first waveform onto an RF carrier to produce a first modulated RF carrier waveform;

a first RF amplifier operating in its saturation region, and being coupled to amplify said first modulated RF carrier waveform to produce a first amplified modulated RF carrier waveform having a first energy content in spectral sidelobes outside an intended limited bandwidth;

a second modulator that is operative to amplitude-modulate transition regions of said first waveform to produce a second amplitude modulated (AM) waveform;

a third modulator that is operative to modulate said second AM waveform onto said RF carrier to produce an AM RF carrier waveform;

a second RF amplifier operating in its saturation region, and being operative to amplify said second AM RF carrier waveform to produce a second amplified AM RF carrier waveform having a second energy content in spectral sidelobes outside said intended limited bandwidth; and

a combiner which is operative to combine said first amplified modulated RF carrier waveform and said second amplified AM RF carrier waveform to produce a composite modulated RF carrier waveform having a spectral characteristic in which said first and second energy contents of spectral sidelobes are suppressed.

14. An apparatus according to claim 13, wherein said second modulator is operative to amplitude-modulate a BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

15. An apparatus according to claim 13, wherein said second modulator is operative to reduce the amplitude of a BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

16. An apparatus for amplifying a binary phase shift keyed (BPSK) waveform that transitions between first and second phase values comprising:

a first modulator that is operative to modulate said BPSK waveform onto an RF carrier to produce a BPSK-modulated RF carrier waveform;

a first RF amplifier operating in its saturation region, and being coupled to amplify said BPSK-modulated RF carrier to produce an amplified BPSK-modulated RF carrier waveform;

a second modulator that is operative to amplitude-modulate transition regions of said BPSK waveform to produce an amplitude modulated (AM)-BPSK waveform;

a third modulator that is operative to modulate said AM-BPSK waveform onto said RF carrier to produce an AM-BPSK modulated RF carrier waveform;

a second RF amplifier operating in its saturation region and being operative to amplify said BPSK modulated RF carrier to produce an amplified AM-BPSK modulated RF carrier waveform; and

a combiner which is operative to combine said amplified BPSK modulated RF carrier waveform and said amplified AM-BPSK modulated RF carrier waveform to produce a composite modulated RF carrier waveform.

17. An apparatus according to claim 16, wherein said second modulator is operative to amplitude-modulate said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.

18. An apparatus according to claim 16, wherein said second modulator is operative to reduce the amplitude of said BPSK waveform beginning prior to and concluding after each transition of said BPSK waveform.