RADIO TRANSMITTER

• US 20090088099A1
• Filed: 07/07/2008
• Published: 04/02/2009
• Est. Priority Date: 03/18/2003
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bristow, Robert
• Granted Patent: US 8,320,845 B2
• Time in Patent Office: Days
• US Class Current: 455/127.200
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/26 Modifications of amplifiers to reduce influence of noise generated by amplifying elements
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2203/45366 the AAC comprising multiple transistors parallel coupled at their gates only, e.g. in a cascode dif amp, only those forming the composite common source transistor
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/45085 Long tailed pairs H03F3/45112, H03F3/45139 take precedence
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators

Abstract

A radio transmitter includes a transmitter circuit which produces a signal at a first frequency, and has digital divider circuitry, for dividing the first frequency to produce a signal at a second frequency. The noise performance of the digital divider is adjusted, depending upon the transmitter output power. Specifically, the digital divider is operated with a relatively good noise performance when the gain of the power amplifier is high, and is operated with a worse noise performance at low output powers. This can ensure that a specified noise requirement is met, without excessively increasing the power consumption or the size of the device.

Claims

1. A radio transmitter, comprising:

a frequency generator for producing a signal at a first frequency;

digital divider circuitry for dividing the first frequency to produce a signal at a second frequency; and

a power amplifier for amplifying the signal at the second frequency to produce an output signal at a desired power, further comprising;

control circuitry adapted to adjust a noise performance of the digital divider circuitry on the basis of the desired power.

2. The radio transmitter of claim 1, wherein the control circuitry is adapted to improve the noise performance of the digital divider circuitry as the desired power increases.

3. The radio transmitter of claim 1, wherein the digital divider circuitry comprises a digital divider, and the control circuitry comprises means for controlling a bias current thereof.

4. The radio transmitter of claim 1, wherein the digital divider circuitry comprises a plurality of digital dividers and the control circuitry comprises means for selecting one of said digital dividers for operation.

5. The radio transmitter of claim 1, for use in a mobile radio communications apparatus.

6. The radio transmitter of claim 5, further comprising a mobile telephone.

7. A radio transmitter, comprising:

a frequency generator for producing a signal at a first frequency;

digital divider circuitry for dividing the first frequency to produce a signal at a second frequency;

a power amplifier for amplifying the signal at the second frequency to produce an output signal at a desired power, and control circuitry adapted to adjust a noise performance of the digital divider circuitry on the basis of the desired power, wherein the control circuitry is adapted to adjust the noise performance of the digital divider circuitry by dynamically adjusting the bias current to the digital divider circuitry as the desired power changes.

8. The radio transmitter of claim 7, wherein the bias current to the digital divider circuitry is increased as the desired power increases and the bias current to the digital divider circuitry is decreased as the desired power decreases.

9. A method of operation of a radio transmitter, the radio transmitter having a frequency generator for producing a signal at a first frequency, a digital divider circuitry for dividing the first frequency to produce a signal at a second frequency, control circuitry adapted to adjust a noise performance of the digital divider circuitry, and a power amplifier for amplifying the signal at the second frequency to produce an output signal at a desired power, the method comprising the step of:

adjusting, by the control circuitry, a noise performance of the digital divider circuitry on the basis of the desired power by adjusting a bias current of the digital divider circuitry as the desired power changes.

10. The method of claim 9, further comprising the steps of:

increasing the bias current as the desired power increases; and

decreasing the bias current as the desired power decreases.

11. A method of operation of a radio transmitter, the radio transmitter having a frequency generator for producing a signal at a first frequency, digital divider circuitry for dividing the first frequency to produce a signal at a second frequency and a power amplifier for amplifying the signal at the second frequency to produce an output signal at a desired power, the method comprising the step of:

adjusting a noise performance of the digital divider circuitry on the basis of the desired power.

12. The method of claim 11, wherein the step of adjusting further comprises the step of improving the noise performance of the digital divider circuitry as the desired power increases.

13. The method of claim 11, wherein the digital divider circuitry has a digital divider and the method comprises the further step of adjusting a bias current thereof.

14. The method of claim 11, wherein the digital divider circuitry has a plurality of digital dividers and the method further comprises the step of selecting one of said digital dividers for operation.