Communication semiconductor integrated circuit, a wireless communication apparatus, and a loop gain calibration method

• US 20040198257A1
• Filed: 02/26/2003
• Published: 10/07/2004
• 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: Wurm, Patrick, Takano, Ryoichi, Toyota, Kenji, Freeborough, David, Henshaw, Robert Astle
• Granted Patent: US 7,082,290 B2
• Time in Patent Office: Days
• US Class Current: 455/108
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A polar-loop wireless communication apparatus includes, on a forward path between an amplitude detector and a power amplifier which constitute an amplitude control loop, a variable gain amplifier and a switch to change characteristics of a loop filter to output a frequency bandwidth of the amplitude control loop to an order less than an order for normal operation. The system is operated with the characteristics set to the lower order to measure outputs from the power amplifier to calibrate the output power of the power transmitter, and the register is operated with the characteristics set to the higher order to measure the open loop gain of the amplitude control. According to results of the calculation, data to correct gain characteristics of the variable gain amplifier with respect to an output control signal is stored in a nonvolatile memory of a baseband circuit.

Claims

1. A transmitter comprising:

a phase loop to control a phase of a carrier signal outputted from a transmitting oscillator;

an amplitude loop to control an amplitude of a transmitter output signal outputted from a power amplifier;

a first variable gain amplifier circuit on a feedback path from a transmitter output level detection means to an amplitude detector;

a second variable gain amplifier circuit on a forward path from the amplitude detector to the power amplifier; and

a nonvolatile memory to store data to vary gain characteristics to an output control signal of the first and second variable gain amplifier circuits to correct gain variations in the loop gain and variations in the power amplifier.

2. A transmitter, comprising:

an integrated circuit for modulation including a baseband circuit for generating I and Q signals according to transmitting data;

a transmitting oscillator for generating a carrier signal;

a power amplifier for amplifying the carrier signal outputted from the transmitting oscillator;

a transmitting output level detection means for detecting a level of an output signal outputted from the power amplifier; and

a modulating semiconductor integrated circuit, said modulating semiconductor integrated circuit comprising;

a quadrature modulator for modulating the I and Q signals at a specified frequency,

a phase loop for controlling a phase of the carrier signal outputted from the transmitting oscillator,

an amplitude loop for controlling an amplitude of a transmitting output signal outputted from the power amplifier,

a first variable gain amplifier circuit on a feedback path from the transmitting output level detection means to amplitude detection means, and

a second variable gain amplifier on a forward path from the amplitude detection means to the power amplifier, wherein

said baseband circuit comprises a nonvolatile memory to store correction data to vary gain characteristics to an output control signal of the first and second variable gain amplifier circuits to correct gain variations in the loop gain and variations in the power amplifier.

3. A transmitter according to claim 2, wherein:

said integrated circuit for modulation has registers to store the correction data; and

the data is read, at start-up of operation of the circuit, from the nonvolatile memory and is fed from the baseband circuit to the integrated circuit to be written in the registers.

4. A transmitter comprising:

a phase loop to control a phase of a carrier signal outputted from a transmitting oscillator;

an amplitude loop to control an amplitude of a transmitter output signal outputted from a power amplifier;

a first variable gain amplifier circuit on a feedback path from a transmitter output level detection means to an amplitude detector; and

a second variable gain amplifier circuit on a forward path from the amplitude detector to the power amplifier, wherein;

gain of the first variable gain amplifier circuit is reduced to increase output power from the power amplifier according to an output control signal;

the gain of the first variable gain amplifier circuit is decreased to reduce the output power from the power amplifier according to the output control signal;

the second variable gain amplifier responds to a common output control signal in opposite senses; and

if there is variation in output power characteristic of the power amplifier to the output control signal, the gain characteristic of the second variable gain amplifier is adjusted in order to control the variation.

5. A transmitter according to claim 4, further comprising a register for storing correction data for correcting the variation in the output power characteristic of the power amplifier and a gain control circuit for generating a bias current for the second variable gain amplifier circuit according to the correction data stored in the register.

6. A transmitter according to claim 4, wherein the correction data includes information to adjust gain offset.

7. A transmitter according to claim 4, wherein the correction data stored in the register includes:

corrective data to correct slope of gain characteristics of the second variable gain amplifier circuit with respect to the output control signal; and

corrective data to correct gain offset of gain characteristics of the second variable gain amplifier circuit with respect to the output control signal.

8. An integrated circuit for wireless communication, comprising a polar loop configuration comprising a phase control loop for controlling a phase of a carrier signal from a transmitting oscillator and an amplitude control loop for controlling amplitude of a transmitting output signal from a power amplification circuit, comprising:

a first variable gain amplifier on a feedback path from transmitting output detection means to an amplitude detection circuit;

a second variable gain amplifier on a forward path from said amplitude detection circuit to a power amplifier; and

a re-configurable register to change and to correct gain characteristics with respect to an output control signal of the firs and second variable gain amplifiers.

9. A transmitter, comprising:

a modulation circuit for phase modulation and amplitude modulation;

a phase detection circuit for detecting a phase component from a modulated signal modulated by the modulation circuit;

an amplitude detection circuit for detecting an amplitude component from a modulated signal modulated by the modulation circuit;

a power amplification circuit for amplifying and outputting a transmitting signal;

a feedback path for giving a feedback signal depending on an output level of the power amplification circuit to the amplitude detection circuit;

a variable gain amplifier disposed on a forward path between the amplitude detection circuit and the power amplification circuit for generating a control voltage for amplitude control;

a loop filter for defining a loop bandwidth for an amplitude control loop including the feedback path and the forward path; and

switching means for reducing an order of loop characteristics of the loop filter to an order thereof for normal operation.

10. A method of calibrating gain variation such as may be used in a transmitter comprising a phase control loop for controlling a phase of a carrier signal from a transmitting oscillator and an amplitude control loop for controlling amplitude of an output from a power amplifier, a variable gain amplifier on a forward path from an amplitude detection circuit to the power amplifier, and selectable means to switch a loop order of the amplitude control loop, said method comprising the steps of:

assessing gain variation of the amplitude control loop by setting by the selectable means a loop order less than a loop order for normal operation; and

calculating the gain variation according to a result of the assessment.

11. An apparatus for modulating a carrier signal, said apparatus including a loop for controlling said modulation, the loop comprising modulation generating means for producing a modulation signal, a forward path for delivering the modulation signal to modulation means for modulating the modulation signal onto the carrier signal and a feedback path returning the modulated carrier signal to the modulation generating means, wherein said loop is capable of operating in type I and II modes.

12. An apparatus according to claim 11, wherein the forward path is reconfigurable to select between the loop modes.

13. An apparatus according to claim 11, wherein the forward path comprises loop filter means that is reconfigurable to select between the loop modes.

14. An apparatus according to claim 11, wherein the loop contains first and second integrators and the first integrator can be selectively disabled and converted into an amplifier to transform the loop from the type II to the type I mode.

15. An apparatus according to claim 14, wherein the first integrator contains a capacitive element that can be selectively disabled and converted into an amplifier to transform the loop from the type II to the type I mode.

16. A method of calibrating an amplitude modulation loop such as may be used in a transmitter, the loop having type I and type II modes and comprising forward and feedback paths, each connecting modulation generating means with amplification means operating on a carrier signal, each path containing a loop amplifier and the loop amplifiers being arranged to respond to a common gain control signal in opposite senses, wherein the method comprises the steps of setting the loop to the type I mode, recording the output of the amplification means in response to variation of said common gain control signal, and compensating said recorded response to enable it to be used as calibration information for type II operation of said loop.

18. A method according to claim 16, wherein one of the loop amplifiers has a corrective gain offset and the method further comprises introducing a predetermined test modulation into the forward path and assessing the corrective effect of the offset by comparing sideband amplitude of the output of the amplification means at different frequencies of said test modulation.

21. A method according to claim 16, further comprising applying a direct control signal to the amplification means, assessing the output of the amplification means due to the direct control signal and using said assessment to control the operation of the amplification means by adjusting the operation of at least one of said loop amplifier.

22. A method according to claim 21, wherein the assessment in response to the direct control signal is used to determine a coefficient to be applied to the common gain control signal en route to one of said loop amplifiers, wherein said coefficient is deduced to maintain the loop bandwidth substantially constant in the operation of the modulating means.

17. A method of calibrating an amplitude modulation loop such as may be used in a transmitter, the loop comprising forward and feedback paths each connecting modulation generating means with amplification means operating on a modulated carrier signal, each path containing a loop amplifier, the loop amplifiers being arranged to respond to a common gain control signal in opposite senses and one of the loop amplifiers having a corrective gain offset, the method comprising introducing a predetermined test modulation into the forward path and assessing the corrective effect of the offset on loop operation by comparing sideband amplitude of the output of the amplification means at different frequencies of said test modulation.

19. A method according to claim 17, further comprising adjusting said offset and performing said assessment until said comparison achieves a desired result.

20. A method according to claim 17, wherein said test modulation is produced using a square wave of predetermined amplitude and frequency.