KR101065874B1 - High-Efficiency Linear Power Amplifier Using Injection Locked Oscillator - Google Patents

Abstract

The present invention relates to a high efficiency linear power amplifier using an injection locked oscillator (ILO).

In the present invention, the input signal is converted into a Pulse Width Modulation (PWM) signal, and the converted PWM signal is applied to an Injection Locked Oscillator to turn the Injection Synchronous Oscillator ON / OFF. After this, it is proposed to recover the input signal by passing it through a band-pass filter.

According to the present invention, since the power device is used only in the ON / OFF region by PWM, high efficiency can be obtained, and linear amplification is possible by controlling the ON time and the OFF time of the pulse.

According to the present invention, since the PWM signal is applied directly to the synchronous oscillator, a mixer, a drive amplifier, a limiter, a class E / F power amplifier, or the like is used. The conventional complex high efficiency linear power amplifier structure constructed can be simplified. In addition, there is an advantage that can eliminate the power loss and non-linearity caused by using the conventional elements.

Linear Power Amplifier, Pulse Width Modulation, Injection Locked Oscillator

Description

High-Efficiency Linear Power Amplifier Using Injection Locked Oscillator

1 is a diagram showing the configuration of a high efficiency linear power amplifier using a conventional pulse width modulation (Pulse Width Modulation).

2 is a first embodiment of a high efficiency linear power amplifier according to the present invention;

3 is a diagram simulating the waveform in the time domain when the synchronous oscillator is ON in the high efficiency linear power amplifier according to the present invention.

4 is a second embodiment of a high efficiency linear power amplifier in accordance with the present invention;

(Explanation of symbols for the main parts of the drawing)

23: Coupler 24: Injection Synchronous Power Oscillator

25: envelope detector 26: pulse width modulator

27: bandpass filter

The present invention relates to a high efficiency power amplifier system using pulse width modulation (PWM).                         

As various mobile communication services are provided, efficiency of mobile communication terminals has emerged as an important problem. Due to the limited capacity and size of portable batteries, it is necessary to design mobile communication terminal circuits at low power. Currently, the most power-consuming component in a mobile communication terminal is a power amplifier, and the efficiency of the CDMA terminal is about 10%. The reason for the low efficiency of the CDMA terminal is that the envelope of the CDMA signal changes in time. If the envelope of the signal is not constant, a linear amplifier is required to amplify the signal. In general, a linear amplifier is biased in class A or AB, which causes a lot of power loss.

One way to efficiently amplify a signal whose envelope changes in time is a power amplifier using PWM. A power amplifier using PWM converts an input signal into a PWM signal, applies it to the input of an E or F class power amplifier, amplifies it, and passes the band-pass filter to restore the input signal. Since the power amplifier uses an E-class or F-class power amplifier as a power device, the efficiency is good, and the linearity is excellent because the signal modulated by the bandpass filter can be accurately recovered.

1 is a diagram illustrating a configuration of a high efficiency linear power amplifier using PWM that is conventionally used. The high efficiency linear power amplifier has a coupler 103 for separating the input signal 101 into the envelope information 111 and the phase information 112, a limiter 104 which makes a signal of a constant size, A drive amplifier 105 for driving the power amplifier 109, an envelope detector 107 for detecting the envelope of the input signal, and a pulse width modulator for converting the detected envelope into a pulse width modulation (Pulse Width Modulator) 108, Mixer 106 for mixing the pulse width modulated signal and phase information, Class E / F power amplifier for amplifying the mixed signal (class E / F) power amplifier 109, and a band-pass filter 110 for restoring the original signal from the amplified signal.

The operation principle of high efficiency linear power amplifier using PWM is as follows. In order to increase the efficiency of the amplifier, the input signal 101 is separated into phase information 112 and envelope information 111 using the coupler 103. The separated phase information is converted into a signal having a predetermined size using the limiter 104 and amplifies the signal to the extent that the power amplifier 109 can be operated through the driving amplifier 105. On the other hand, the envelope information is modulated into a rectangular wave to increase the efficiency of the power amplifier, and the pulse width is modulated in a pulse width modulation scheme that allows the width of the pulse to have information of the envelope. The signal amplified as described above and modulated with a pulse width is mixed through the mixer 106 and applied to a class E or F power amplifier. At this time, the input of power amplifier is square wave and it is theoretically 100% efficient because it is amplified by class E or class F amplifier. The condition to obtain such high efficiency is when the class E or F power amplifier operates in saturation mode, and the elements used to satisfy the above conditions are the limiter 104 and the mixer 106. .

Finally, since the signal amplified by the class E or F power amplifier passes through the band pass filter 110, the harmonic frequency generated by the pulse width modulation is filtered, thereby restoring the original input signal.                         

As mentioned above, the high efficiency linear power amplifier using PWM can theoretically amplify linearly with 100% efficiency, but since it is composed of several devices, the system is complicated and efficiency and linearity are not There is a problem of deterioration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended to simplify a high efficiency linear power amplifier using a complex PWM composed of several devices, and at the same time, to improve the efficiency and linearity of the entire system.

In order to achieve the above object, the present invention simplifies the structure of a high efficiency linear power amplifier using a conventional PWM using a class E or F injection locked oscillator.

Injection locked oscillator (Injection Locked Oscillator) is a PLL (Phase Locked Loop), a circuit that obtains a stable signal by applying an input signal to a free-running oscillator. The free-running signal is shaken by the noise of the external environment or the active element, but when a stable signal is input from the outside, the free-running signal is synchronized by the external signal regardless of the noise. That is, the oscillation frequency is the same as the input signal frequency applied from the outside, the synchronous oscillator as described above has a high gain, it is characterized by operating in the saturation mode (saturation mode).                     

The present invention is applied to a high efficiency linear amplifier using the characteristics that the injection synchronous oscillator has a high gain and the efficiency is high because it operates in the saturation mode. Since the injection synchronous oscillator itself has a high gain, it can take the role of the driving amplifier 105 in the high efficiency linear amplifier using the conventional PWM, and in the saturation mode, the conventional limiter 104 and the mixer 106 and It may take the role of the E-class power amplifier 109. Looking at the configuration of the present invention.

According to the present invention, a coupler for separating an input signal into envelope information and phase information, an envelope detector for detecting an envelope of an input signal, a pulse width modulator for modulating the detected envelope to a pulse width, and a signal width modulated to a pulse width modulated signal are turned on. It consists of an injection synchronous oscillator with ON / OFF operation and a band pass filter for recovering a desired input signal from the output of the injection synchronous oscillator.

Hereinafter, a high efficiency linear power amplifier using an injection synchronous oscillator according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a first embodiment of a high efficiency linear power amplifier using an injection synchronous oscillator according to the present invention.

According to the present invention, when the input signal 21 is input, the 29 is separated into the envelope information 28 and the phase information through the coupler 23. The reason for separating the two signals is that although the input signal can be amplified with high efficiency. This is because separate envelope signals and phase signals can be amplified with high efficiency. In this case, the separated envelope signal is detected by the envelope detector 25 and modulated by the pulse width modulator 26. The reason for the pulse width modulation of the envelope signal is to control the time for which the injection synchronous power oscillator 24 is turned on in proportion to the pulse width. That is, when the pulse is '1', the injection synchronous power oscillator is ON. When the pulse is '0', the injection synchronous power oscillator is OFF. Meanwhile, the separated phase information 29 is directly applied to the injection synchronous power oscillator to synchronize the frequency of the injection synchronous power oscillator to the phase information signal.

The injection synchronous power oscillator operates in saturation mode like other general oscillators, so the efficiency is good. If it is designed as E or F class, the efficiency can be more than 80%. Since the output of the injection synchronous power oscillator has a signal component modulated with a pulse width, a band pass filter 27 is used to recover the original input signal. At this time, the center frequency of the bandpass filter is the same as the frequency of the input signal, the bandwidth is exactly demodulated when the frequency of the pulse train for pulse width modulation.

Figure 3 is a simulation result of the waveform in the time domain when the injection synchronous power oscillator according to the present invention (On). The simulation used Agilent Technology's ADS (Advanced Design System), and NEC's transistor NE32484A was used as the active device. The oscillation frequency is 10GHz.

As a result of the simulation, the time taken for the oscillator to be turned on because the pulse waveform modulated by PWM becomes '1' is about 0.5ns. If the period of the pulse train for pulse width modulation is 50 ns, the time taken for the oscillator to reach a steady state (0.5 ns) is relatively small (1%) compared to the pulse train period (50 ns). Therefore, when the synchronous power oscillator is turned on and off, the output of the power oscillator can be seen as a substantially rectangular waveform. In this case, since the period of the pulse train is 50 ns, the frequency of the pulse train is 1/50 ns = 20 MHz, which is a bandwidth large enough to process baseband information.

Therefore, when the injection synchronous power oscillator is turned on and off as in the present invention, a square wave carrying the desired information can be made, and if it is passed through the band pass filter, the desired information can be easily restored.

4 shows a second embodiment of a high efficiency linear amplifier using an injection synchronous oscillator according to the present invention. Instead of the injection synchronous power oscillator 24 of the first embodiment, a small power injection synchronous oscillator 43 and an E-class or F The power supply amplifier 46 is used in combination.

When the output synchronous power oscillator 24 has a very large output power, the time taken when the pulse waveform is '1' and turned on becomes long. However, if a small power injection synchronous oscillator 43 is used instead of the injection synchronous power oscillator, the steady state can be reached in a short time. At the same time, an additional Class E or F power amplifier 46 is used to obtain a large output power. That is, when the injection synchronous power oscillator is divided into a small power injection synchronous oscillator and an E or F class power amplifier, linearity and efficiency are further improved since the time for reaching the steady state is increased while maintaining the output.

The present invention is not limited to the above embodiments and may be variously modified and changed by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

According to the present invention, since a PWM signal is directly applied to an injection locked oscillator in a high efficiency linear power amplifier using a conventional PWM, a mixer, a drive amplifier, a limiter, an E-class Or it has the effect of simplifying the conventional complex linear power amplifier structure composed of a class E power amplifier (class E power amplifier). In addition, the problem of power loss and nonlinearity caused by using the above-described elements can be solved.

Claims (3)

delete Coupler 23 for separating input signal 21 into phase information 29 and envelope information 28, and injection locked power oscillator for amplifying the phase information in the form of saturation mode. Oscillator 24, an envelope detector 25 for detecting the envelope of the separated envelope information, a pulse width modulator 26 for modulating the detected envelope into a pulse width, and an output of the injection synchronous power oscillator A band pass filter 27 for demodulating an input signal, The phase information is directly applied to the injection synchronous power oscillator to synchronize the injection synchronous power oscillator, and the signal modulated by the pulse width modulator is turned on or off of the injection synchronous power oscillator. In the high efficiency linear power amplifier, characterized in that The injection synchronous power oscillator is a high efficiency linear power amplifier, characterized in that operating in class E or F (Class E or F). Coupler 42 for separating input signal 41 into phase information 49 and envelope information 48, and a low power injection locked oscillator for amplifying the phase information in saturation mode. (43), an envelope detector (44) for detecting the envelope of the separated envelope information, a pulse width modulator (45) for modulating the detected envelope into pulse widths, E connected to the output of said small power injection synchronous oscillator A band pass filter 47 connected to the output of the class or F class power amplifier 46 and the output of the class E or F class power amplifier to demodulate an input signal, The phase information 49 is directly applied to the small power injection synchronous oscillator to synchronize the small power injection synchronous oscillator, and the pulse width modulated signal through the pulse width modulator turns on the small power injection synchronous oscillator. High efficiency linear power amplifier, characterized in that (ON) -OFF (OFF).

Images