Device and method for radio transmitters

• US 6,047,168 A
• Filed: 06/23/1997
• Issued: 04/04/2000
• Est. Priority Date: 06/28/1996
• Status: Expired due to Term

• Current Assignee: Optis Wireless Technology, LLC (Brevet Capital)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Carlsson, Torsten, Hellmark, Martin
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): Trinh, Sonny
• Application Number:
  US08/880,740
• Time in Patent Office: 1,016 Days
• Field of Search: 455/63, 455/70, 455/139, 455/205, 455/126, 455/127, 455/118, 455/119, 375/295, 375/298, 375/300, 370/215, 370/205, 370/206, 370/252, 332/144, 332/145, 330/284, 330/285
• US Class Current: 455/126
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

The present invention relates to a device and a method in a transmitter stage in a radio transmitter for modulating and amplifying an information signal for further transmission through a radio channel. The transmitter stage in the radio transmitter comprises a converting device (5) PCH, an amplifier control device (8) PAC, a power detector (13) and a power amplifier (2). Examples of the problems solved by the present invention are difficulties in reducing the power consumption, non-linearities in the output signal when using non-linear amplifiers in radio transmitters, and achieving a high signal-to-noise ratio in the output signal without connecting filter arrangements after such an amplifier. The solution according to the inventive method and device utilizes an information signal which has in earlier steps been divided in its polar components: a phase reference component signal (E_phr) and an amplitude component signal (A_amp). The phase reference component phase modulates a low noise high power signal source which has a constant amplitude. The amplitude of the obtained signal is then formed in an amplifier, which is controllable with the amplitude component signal (A_amp). Its current consumption is registered and compared to a control value for the current. The amplifier is controlled towards this control value.

Claims

1. A radio transmitter for transmission of an information signal over a radio channel, said transmitter comprises a transmitter stage comprising:

a power amplifier with a current supply and at least one input for a phase modulated signal and a control input, and an aerial signal output for emission of an aerial signal to an aerial;

a conversion device for phase locking and frequency conversion, said conversion device comprising;

a phase signal input terminal for receiving a phase reference component signal, said phase reference component signal is a component of said information signal, and

an RF signal output terminal for the emission of the phase modulated RF signal to the input terminal of said power amplifier; and

an amplifier control device for signal processing and output power control comprising;

an amplitude input terminal for receiving and amplitude component signal which is a component signal of said information signal,

a control value input terminal for receiving a control value signal which indicates the desired output power from the power amplifier,

a true value input terminal for receiving a true value which is a measure of the output power of said power amplifier, and

an output terminal connected to said control input of said power amplifier,

wherein a power detector is connected to said current supply of said power amplifier to register the current consumption, to form said true value signal and to emit said true value signal to said amplifier control device where an amplifier control signal is generated as a function of the amplitude component signal, the true value signal and said control value and is emitted to the control input of said power amplifier.

2. A radio transmitter for transmitting an information signal over a channel according to claim 1, wherein said power amplifier, said power detector and said amplifier control device form a closed loop.

3. A radio transmitter according to claim 1, wherein said conversion device for phase locking and frequency conversion further comprises a low-noise high-power voltage controlled oscillator.

4. A radio transmitter according to claim 1, wherein said amplifier control device for signal processing and output power control further comprises a D/A converter.

5. A radio transmitter according to claim 1, further comprising;

a frequency synthesizer which generates a frequency reference signal.

6. A radio transmitter according to claim 1, wherein said radio transmitter transmits on a radio channel for mobile telephones.

7. A radio transmitter according to claim 1 wherein said conversion device for phase locking and frequency conversion further comprises;

a combination circuit for combining a signal branched from the input of said power amplifier and a signal branched from said output of said power amplifier to a feedback signal.

8. A radio transmitter according to claim 1, wherein said amplifier control device further comprises a table unit.

9. A radio transmitter according to claim 1, wherein said amplifier control device further comprises a compensation circuit.

10. A radio transmitter according to claim 1, wherein said conversion device for phase locking and frequency conversion obtains a frequency reference signal from a source arranged outside said conversion device.

11. A method in a transmitter stage of a radio transmitter to modulate and amplify and information signal to an aerial signal for further transmission, wherein said information signal is split into a phase reference component signal and an amplitude component signal, said method comprising:

adding said amplitude component signal and a control value signal to form a first signal;

converting said first signal in a digital/analog converter to an analog signal;

compensating for a non-linear connection between a supply current and an output power in said aerial signal with a compensation function implemented in a compensation circuit which corrects said analog signal to an amplitude control value signal which is proportional to the output power from said amplifier;

detecting a supply of current to said power amplifier;

generating a true value signal in a power detector;

comparing said amplitude control value signal to said true value signal by means of an amplituded controller;

generating an error signal based upon said comparing step;

filtering said error signal and generating and amplifier control signal so that an aerial signal is generated; and

connecting said aerial signal to an aerial for further transmission through said radio channel.

12. A method according to claim 11, further comprising the step of;

adjusting a new binary encoded signal using a table value unit of a look-up-table type.

13. A method according to claim 11, further comprising the step of;

compensating for phase distortion in said aerial signal.

14. A method according to claim 13, further comprising the steps of;

phase locking a voltage controlled oscillator located in said conversion device, said oscillator generating a phase modulated RF signal;

compensating for phase distortion in said aerial signal by carrying out the phase locking in said conversion device before the output power of the power amplifier is changed.

15. A method according to claim 14, further comprising the step of;

combining a signal branched from the input of the power amplifier with a signal branched from the output of the power amplifier to form a feedback signal.

16. A method according to claim 15, further comprising the step of;

transitioning between the mutual share of the branched signals and their dominance in the feedback signal.

17. A method according to claim 11, further comprising the step of;

compensating for the non linear connection between the supply current and the output power with an exponential compensation function implemented in said compensation circuit which corrects the analog signal to an amplitude control value signal.

18. A radio transmitter for transmission of an information signal over a radio channel, said transmitter has a transmitter stage having a power amplifier with a current supply, a conversion device and an amplifier control device, said transmitter also comprising;

a power detector;

said power detector connected to the current supply of the power amplifier to register the current consumption, to form a true value signal and emit the true value signal to said amplifier control device;

said amplifier control device generating a control signal as a function of the true value signal, an amplitude component signal which is a component of an information signal and a control value indicating the desired output power from the power amplifier.

19. A radio transmitter for transmitting an information signal over a channel according to claim 18, wherein said power amplifier, said power detector and said amplifier control device form a closed loop.

20. A radio transmitter according to claim 18, wherein said conversion device for phase locking and frequency conversion comprises a low-noise high-power voltage controlled oscillator.

21. The radio transmitter according to claim 18, wherein the power amplifier is non-linear.