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Audio Signal Processing

Power-control-method-for-a-voltage-controlled-power-amplifier-and-circuitry-used-in-the-method

Phase logic demodulator

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Portable radio communication equipment

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Power control method for a voltage controlled power amplifier and circuitry used in the method

Details

Inventors: Vaisanen, Risto;
Assignee: Nokia Mobile Phones Ltd. (Salo, FI)
Primary Examiner: Mottola; Steven
Assistant Examiner:
Attorney, Agent or Firm: Darby & Darby

In a digital radio telephone transmitter an output pulse with e.g. cos.sup.2 -shaped edges is produced by a voltage controlled power amplifier (4). When known control loop circuitry is used, the power (Pout) of the output pulse will rise almost step-wise at the beginning of the pulse, which leads to the spreading of the spectrum and to rise time delays of the output pulse with respect to the control pulse (TXC) at different power levels. According to the invention a good cos.sup.2 -shape of the output pulse (Pout) and its tracking of the control pulse (TXC) almost without delay is achieved so that a squarewave pulse (V.sub.p) is added to the control voltage (V2) of the power amplifier (4), the pulse (V.sub.p) starting and ending substantially at the same time as the control pulse (TXC). In a preferred embodiment the squarewave pulse (V.sub.p) is added to the control voltage (V2) only during that time when the control voltage (V2) is below that value, at which the control loop begins to operate.

DETAILED DESCRIPTION I claim: 1.
A method for controlling the rising and falling edges of an output pulse of a voltage controlled power amplifier (4) to track a waveform of a control pulse (TXC) when the power amplifier is controlled with a control loop producing a control voltage (V2) with the aid of a voltage (V1) proportional to the output pulse power (Pout) and with the aid of a control pulse (TXC), whose rising and falling edges are e.
g.
cos.
sup.
2 -shaped, wherein a square wave pulse (Vp) is added to the control voltage (V2) of the power amplifier, the pulse (Vp) starting and ending substantially at the same times as the control pulse (TXC).
2.
A method according to claim 1, wherein the voltage level of the squarewave pulse (Vp) is approximately the same as that value of the control voltage (V2), at which the control loop begins to operate.
3.
A method according to claim 1 or 2, wherein the squarewave pulse (Vp) is added to the control voltage (V2) only during a time when the control voltage (V2) is below that value (V3) at which the control loop begins to operate.
4.
Circuitry to control the rising and falling edges of an output pulse of a voltage controlled power amplifier (4) to track a waveform of a control pulse (TXC) when the power amplifier is controlled with a control loop producing a control voltage (V2) with the aid of a voltage (V1) proportional to the output pulse power (Pout) and with the aid of a control pulse (TXC), whose rising and falling edges are e.
g.
cos.
sup.
2 -shaped, comprising a summing circuit, in which a squarewave pulse (Vp) is added to the control voltage (V2) of the power amplifier, the pulse (Vp) starting and ending substantially at the same time as the control pulse (TXC).
5.
Circuitry according to claim 4, and further comprising a switching means (5) for disconnecting the squarewave pulse (Vp) from the summing circuit during that time when the control loop is operating.
6.
Circuitry according to claim 5, wherein the switching means (5) is a transistor circuit

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