Apparatus for radio telecommunication system and method of building up output power

• US 20030224743A1
• Filed: 02/26/2003
• Published: 12/04/2003
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.), TTPCom Ltd. (Motorola Solutions, Inc.)
• Original Assignee: Renesas Technology Corporation (Renesas Electronics Corporation)
• Inventors: Okada, Kazuhisa, Wurm, Patrick, Hikasa, Kazuhiko
• Granted Patent: US 7,209,717 B2
• Time in Patent Office: Days
• US Class Current: 455/127.2
• CPC Class Codes: H03F 1/0205 in transistor amplifiers
• CPC Class Codes: H03F 1/30 Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in differential amplifiers H03F3/45479
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/513 the amplifier being made for low supply voltages
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2017 in which the phase changes are non-linear, e.g. generalized and Gaussian minimum shift keying, tamed frequency modulation H04L27/201 takes precedence
• CPC Class Codes: H04L 27/2071 in which the data are represented by the carrier phase, e.g. systems with differential coding
• CPC Class Codes: H04L 27/361 Modulation using a single or unspecified number of carriers, e.g. with separate stages of phase and amplitude modulation

Abstract

A polar loop based radio telecommunication apparatus which has a phase control loop for controlling the phase of a carrier outputted from an oscillator for transmitter, and an amplitude control loop for controlling the amplitude of a transmission output signal outputted from a power amplifier circuit, wherein precharge means is provided on a forward path from a current source, through the power amplifier circuit, to a detection circuit, forming the amplitude control loop, for rapidly increasing a control voltage for the power amplifier circuit to a power threshold upon starting transmission.

Claims

1. An apparatus for a radio telecommunication system comprising:

a modulation circuit for performing phase modulation and amplitude modulation;

a phase detection circuit for detecting a phase component of a signal modulated by said modulation circuit;

an amplitude detection circuit for detecting an amplitude component of the signal modulated by said modulation circuit;

a power amplifier circuit for amplifying power of a transmission signal and outputting the amplified transmission signal;

a feedback path for feeding a signal corresponding to an output level of said power amplifier circuit back to said amplitude detection circuit;

a variable gain amplifier circuit provided on a forward path between said amplitude detection circuit and said power amplifier circuit for generating a control voltage for amplitude control of said power amplifier circuit;

a loop filter for setting a frequency bandwidth of an amplitude control loop, said amplitude control loop including said feedback path and said forward path; and

precharge means for rapidly raising an output power of said power amplifier circuit from a low power level to a power threshold for building up output power of said power amplifier circuit.

2. An apparatus according to claim 1, further comprising level detecting means for detecting the level of a signal fed back through said feedback path, wherein said precharge means includes a current source and switch means connected in series with said current source, said switch means being configured to be turned on when building up the output power of said power amplifier circuit, and turned off based on the level detected by said level detecting means.

3. An apparatus according to claim 1, wherein said variable gain amplifier circuit is configured such that an inverting input terminal and a non-inverting input terminal are short-circuited while an output is opened during a precharge operation, and said inverting input terminal and said non-inverting input terminal are opened while the output is short-circuited in response to termination of the precharge operation.

4. An apparatus according to claim 1, further comprising:

a charge pump circuit provided on said forward path, said charge pump circuit including a capacitor, a current source for charging said capacitor, and a current sink for discharging a charge on said capacitor, said charge pump circuit configured to operate said current source and said current sink in response to an output of said variable gain amplifier circuit to accumulate a charge on said capacitor,

wherein said precharge means is controlled to charge said capacitor to the power threshold when building up the output power of said power amplifier circuit.

5. An apparatus according to any of claim 1, further comprising a timer circuit, wherein said precharge means is forced to terminate a precharge operation at an earlier one of timing of detection of lapse of a predetermined time measured by said timer circuit after said precharge means starts the precharge operation, and timing of detection, by said level detecting means, of a level of the signal fed back by said feedback path.

6. An apparatus according to claim 1, wherein said current source is turned off when said timer circuit forces said precharge means to terminate the precharge operation.

7. An apparatus according to claim 2, further comprising a first precharge means and a second precharge means having a precharge rate lower than that of said first precharge means, wherein said first precharge means and said second precharge means are configured such that after said first precharge means starts a precharge operation for building up the output power of said power amplifier circuit, said first precharge means is forced to stop the precharge operation while said second precharge means is forced to start a precharge operation, and said second precharge means is turned off based on the detection of said level detecting means.

8. An apparatus according to claim 2, further comprising a first precharge means and a second precharge means, wherein said first precharge means and said second precharge means are configured such that after said first precharge means and said second precharge means start a precharge operation for building up the output power of said power amplifier circuit, said first precharge means is forced to stop the precharge operation while said second precharge means continues the precharge operation, and said second precharge means is turned off based on the detection of said level detecting means.

9. An apparatus according to claim 7, wherein said first precharge means includes a regulated voltage source, and switch means connected between said regulated voltage source and said capacitor.

10. An apparatus according to claim 9, further comprising:

a level shift circuit connected behind said charge pump circuit for outputting an input voltage shifted in a negative direction; and

a regulated voltage source for setting a shift amount in said level shift circuit, said regulated voltage source being used in common with said regulated voltage source which forms part of said first precharge means.

11. An apparatus according to claim 1, further comprising a second variable gain amplifier circuit provided on said feedback path for amplifying a signal indicative of a detected output level of said power amplifier circuit,

wherein the gain of said second variable gain amplifier circuit is reduced when the output power of said power amplifier circuit needs to be increased based on an output control signal, and the gain of said second variable gain amplifier circuit is increased when the output power of said power amplifier circuit needs to be decreased based on the output control signal, and

wherein said second variable gain amplifier circuit and said variable gain amplifier circuit on said forward path are controlled such that their gains change in reverse directions to each other in response to the output control signal.

12. An apparatus according to claim 1, further comprising:

an oscillator for transmitter operative in response to an output of said phase detection circuit for feeding a signal in accordance with an output of said oscillator back to said phase detection circuit, said phase detection circuit being configured to compare the phase of a modulated signal from said modulation circuit with the phase of said feedback signal to output a signal in accordance with a phase difference,

wherein said precharge means is configured to precharge after said phase control loop is started and stabilized.

13. A method of building up output power in a radio telecommunication apparatus having a phase control loop for controlling the phase of a carrier outputted from an oscillator for transmitter, and an amplitude control loop for controlling the amplitude of a transmission output signal outputted from a power amplifier circuit, said method comprising the steps of:

starting first said phase control loop;

opening said amplitude control loop after said phase control loop is stabilized to perform a precharge for raising the control signal of the power amplifier so that the output power rises up to a power threshold;

terminating said precharge when said forward path reaches the power threshold; and

closing said amplitude control loop to build up the output power of said power amplifier circuit.

14. An apparatus for controlling a power amplifier operating on a carrier signal, the apparatus comprising a feedback path for conveying a sample of the output of the power amplifier to comparison means arranged to output an amplitude control signal related to the difference in amplitude of said sampled amplifier output and a modulation signal to be amplitude-modulated onto the carrier signal, and a forward path for conveying the amplitude control signal to an input of the power amplifier to control the power amplification, wherein the forward path includes control means which operates at start up of the power amplifier under low power conditions to remove the amplitude control signal from the input and apply a ramping voltage to the input to increase the speed with which the output of the power amplifier reaches a power threshold, at which the ramping voltage is terminated and the amplitude control signal is re-applied to the input of the power amplifier.

15. An apparatus as claimed in claim 14, in which the forward path includes a loop filter comprising a capacitor, and in which the control means comprises a current source which is connected to the capacitor to generate said ramping voltage.

16. An apparatus as claimed in claim 14, in which the amplitude control signal is removed from the input of the power amplifier by tri-stating a device in the forward path.

17. An apparatus as claimed in claim 14, in which the forward path includes a variable gain amplifier, and the control means short-circuits the inputs of the variable gain amplifier to retain the reference voltage from the comparison means when the amplitude control signal is removed from the power amplifier.

18. An apparatus as claimed in claim 14, including detector means to detect the amplitude peak signals at the inputs of the comparison means that receive said sampled amplifier output and modulation signal, respectively, the detector means being adapted to produce a control signal that disconnects the predetermined voltage signal from the power amplifier and reconnects the amplitude control signal.

19. An apparatus as claimed in claim 18, in which the detector means produces said control signal when the sampled amplifier output equals or exceeds said modulation signal.

20. An apparatus as claimed in claim 14, in which the control means includes a timer that operates to ensure that the ramping voltage is terminated and the amplitude control signal is re-applied to the power amplifier a predetermined maximum time after the ramping voltage is applied to the input.

21. A mobile telecommunications terminal incorporating apparatus as claimed in claim 14.