Apparatus and method for generating a transition between the on and off states of a radio frequency transmitter

• US 5,621,763 A
• Filed: 05/15/1995
• Issued: 04/15/1997
• Est. Priority Date: 07/22/1991
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Greene, Robert I., Diehl, John W., Cahill, Stephen V., Walczak, Thomas J.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US08/440,854
• Time in Patent Office: 701 Days
• Field of Search: 375/309, 375/312, 375/313, 375/295, 375/296, 375/229, 332/155, 332/158, 330/279, 330/127, 455/116, 178/116
• US Class Current: 375/312
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals
• CPC Class Codes: H04W 52/04 TPC

Abstract

An apparatus and method generates a shaped transition between the minimum and maximum output power levels of a transmitter (500). When the transmitter is turned on a stepped transition (415) is generated at the beginning (3) of the transition region (409) followed by a shaped transition (417) to the end (6) of the transition region (409). When the transmitter (500) is turned off a shaped transition region (417'"'"') is generated at the beginning (162) of the transition region (411) followed by a stepped transition (415'"'"') at the end (3) of the transition region (411). The stepped transition (415 or 415'"'"') is generated by adjusting a voltage controlled attenuator (545) and the bias of a power amplifier (545) in the transmitter (500). The shaped transition (417 or 417'"'"') is generated by processing transmitted information through finite impulse response filters (507 or 509) before or after the time slot permitted for transmitting information.

Claims

1. A method for generating a digital burst signal in a transmitter, the digital burst signal defining a predetermined time duration including a first, a second and a third time period, the first time period providing a first transition time during which the transmitter is permitted to adjust between first and second output power levels, the second time period providing a transmission time during which the transmitter is permitted to transmit a predetermined number of sequential symbols at the transmitter'"'"'s second output power level, the third time period providing a second transition time during which the transmitter is permitted to adjust between the second and first output power levels, the method comprising the steps of:

generating a first set of predetermined number of sequential symbols, which are sequentially followed by a second set of predetermined number of sequential symbols, which are sequentially followed by a third set of predetermined number of sequential symbols, wherein each of predetermined number of sequential symbols in the first and third sets of predetermined number of sequential symbols have a zero value;

filtering the generated predetermined number of sequential symbols responsive to a predetermined impulse response having a leading portion and a trailing portion; and

controlling the timing of when the first, second and third sets of predetermined number of sequential symbols are generated by the step of generating responsive to the predetermined impulse response, wherein the first set of predetermined number of sequential symbols sequentially followed by the second set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the leading portion of the predetermined impulse response to cause the transmitter to adjust between the first and second output power levels only during the first transition time and wherein the second set of predetermined number of sequential symbols sequentially followed by the third set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the trailing portion of the predetermined impulse to cause the transmitter to adjust between the second and the first output power levels only during the second transition time.

2. A method according to claim 1 further comprising a step of biasing "on" the transmitter at a beginning of the first time period and "off" the transmitter at an end of the second time period.

3. A method according to claim 1 wherein the first and second output power levels further comprise "off" and "on" states, respectively, of the transmitter.

4. A method according to claim 1 wherein the first and second output power levels further comprise fixed and variable output power levels, respectively.

5. A method according to claim 1 further comprising a step of modulating either the generated predetermined number of sequential symbols or the filtered predetermined number of sequential symbols.

6. A digital burst signal transmitter, the digital burst signal defining a predetermined time duration including a first, a second and a third time period, the first time period providing a first transition time during which the transmitter is permitted to adjust between first and second output power levels, the second time period providing a transmission time during which the transmitter is permitted to transmit a predetermined number of sequential symbols at the transmitter'"'"'s second output power level, the third time period providing a second transition time during which the transmitter is permitted to adjust between the second and first output power levels, the digital burst signal transmitter comprising:

a signal generator for generating a first set of predetermined number of sequential symbols, which are sequentially followed by a second set of predetermined number of sequential symbols, which are sequentially followed by a third set of predetermined number of sequential symbols, wherein each of predetermined number of sequential symbols in the first and third sets of predetermined number of sequential symbols have a zero value;

a filter for filtering the generated predetermined number of sequential symbols responsive to a predetermined impulse response having a leading portion and a trailing portion; and

a controller for controlling the timing of when the first, second and third sets of predetermined number of sequential symbols are generated by the step of generating responsive to the predetermined impulse response, wherein the first set of predetermined number of sequential symbols sequentially followed by the second set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the leading portion of the predetermined impulse response to cause the transmitter to adjust between the first and second output power levels only during the first transition time and wherein the second set of predetermined number of sequential symbols sequentially followed by the third set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the trailing portion of the predetermined impulse to cause the transmitter to adjust between the second and the first output power levels only during the second transition time.

7. An apparatus according to claim 6 further comprising a processor for biasing "on" the transmitter at a beginning of the first time period and "off" the transmitter at an end of the second time period.

8. An apparatus according to claim 6 wherein the first and second output power levels further comprise "off" and "on" states, respectively, of the transmitter.

9. An apparatus according to claim 6 wherein the first and second output power levels further comprise fixed and variable output power levels, respectively.

10. An apparatus according to claim 6 further comprising a modulator for modulating either the generated predetermined number of sequential symbols or the filtered predetermined number of sequential symbols.

11. A method for operating a radiotelephone in a time division multiple access system, comprising the steps of:

receiving a first digital burst signal during a first time slot of a signaling frame; and

transmitting a second digital burst signal during a second time slot of the signaling frame, the second digital burst signal defining a predetermined time duration including a first, a second and a third time period, the first time period providing a first transition time during which the transmitter is permitted to adjust between first and second output power levels, the second time period providing a transmission time during which the transmitter is permitted to transmit a predetermined number of sequential symbols at the transmitter'"'"'s second output power level, the third time period providing a second transition time during which the transmitter is permitted to adjust between the second and first output power levels, the method of transmitting further comprising the steps of;

generating a first set of predetermined number of sequential symbols, which are sequentially followed by a second set of predetermined number of sequential symbols, which are sequentially followed by a third set of predetermined number of sequential symbols, wherein each of predetermined number of sequential symbols in the first and third sets of predetermined number of sequential symbols have a zero value;

filtering the generated predetermined number of sequential symbols responsive to a predetermined impulse response having a leading portion and a trailing portion; and

controlling the timing of when the first, second and third sets of predetermined number of sequential symbols are generated by the step of generating responsive to the predetermined impulse response, wherein the first set of predetermined number of sequential symbols sequentially followed by the second set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the leading portion of the predetermined impulse response to cause the transmitter to adjust between the first and second output power levels only during the first transition time and wherein the second set of predetermined number of sequential symbols sequentially followed by the third set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the trailing portion of the predetermined impulse to cause the transmitter to adjust between the second and the first output power levels only during the second transition time.

12. A radiotelephone for use in a time division multiple access system, comprising:

a receiver for receiving a first digital burst signal during a first time slot of a signaling frame; and

a transmitter for transmitting a second digital burst signal during a second time slot of the signaling frame, the second digital burst signal defining a predetermined time duration including a first, a second and a third time period, the first time period providing a first transition time during which the transmitter is permitted to adjust between first and second output power levels, the second time period providing a transmission time during which the transmitter is permitted to transmit a predetermined number of sequential symbols at the transmitter'"'"'s second output power level, the third time period providing a second transition time during which the transmitter is permitted to adjust between the second and first output power levels, the means for transmitting further comprising;

a signal generator for generating a first set of predetermined number of sequential symbols, which are sequentially followed by a second set of predetermined number of sequential symbols, which are sequentially followed by a third set of predetermined number of sequential symbols, wherein each of predetermined number of sequential symbols in the first and third sets of predetermined number of sequential symbols have a zero value;

a filter for filtering the generated predetermined number of sequential symbols responsive to a predetermined impulse response having a leading portion and a trailing portion; and

a controller for controlling the timing of when the first, second and third sets of predetermined number of sequential symbols are generated by the step of generating responsive to the predetermined impulse response, wherein the first set of predetermined number of sequential symbols sequentially followed by the second set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the leading portion of the predetermined impulse response to cause the transmitter to adjust between the first and second output power levels only during the first transition time and wherein the second set of predetermined number of sequential symbols sequentially followed by the third set of predetermined number of sequential symbols are generated at a predetermined time for loading into predetermined taps forming the trailing portion of the predetermined impulse to cause the transmitter to adjust between the second and the first output power levels only during the second transition time.