KR20080078937A - Amplifier device - Google Patents

Abstract

An amplification device is provided to improve the transmit/receive sensitivity of a communication system by preventing the distortion of a signal. An amplification device includes a coupling unit(110), a signal limiter(120), a detection unit(130), a comparison unit(140), an attenuation unit(150), and an amplifying unit(160). The coupling unit couples a signal. The signal limiter limits a larger signal part than the power level of the coupled signal. The detection unit detects the power level of the coupled signal and generates a detection signal. The comparison unit compares the detection signal of the detection unit with an output signal of the signal limiter, and then generates a control signal. The attenuation unit attenuates the signal outputted from the coupling unit in response to the control signal. The amplifying unit amplifies the signal outputted from the attenuation unit.

Description

Amplifier device

1 is a diagram schematically illustrating a general amplification module amplifying an OFDM signal.

2 is a block diagram schematically illustrating the components of an amplifying apparatus according to an embodiment of the present invention.

Figure 3 is a circuit diagram schematically showing the components of the signal limiting portion of the amplifying apparatus according to the embodiment of the present invention.

4 is a graph schematically illustrating a form in which coupling signals processed by an amplifying apparatus according to an embodiment of the present invention are compared.

<Explanation of symbols for main parts of drawing>

100: amplification device 110: coupling unit

120: signal limiter 130: detector

140: comparison unit 150: attenuation unit

160: amplifier 200: modulator

300: up-converter 320: local oscillation circuit

The present invention relates to an amplification device.

Currently, communication systems such as mobile phones, personal digital assistants (PDAs), digital multimedia broadcasting (DMB) transceivers, and wireless local area network (WLAN) devices have been developed in various platforms to provide various services. .

Such a communication system transmits data using various signal standards such as code division multiple access (CDMA), orthogonal frequency division multiplexing (OFDM), global systems for mobile communication (GSM), and the like, and is a kind of multicarrier modulation technology. OFDM technology is used in mobile communication technology such as WLAN, DMB technology, etc. due to the following advantages.

First, since the duration of a unit transmission symbol is longer than that of a single carrier method, when a guard interval is added on the time axis, deterioration of transmission characteristics is reduced even if the multipath is increased.

Second, since data is distributed and transmitted throughout the transmission band, even if an interference signal exists in a specific frequency band, it is limited to some data bits, and using interleave and error correction codes makes it easy to recover data. Can be.

Third, due to the orthogonal characteristics, the utilization efficiency of the frequency band is high, various communication systems can be configured using a single frequency, and modulation and demodulation processing by FFT (Fast Fourier Transform) is possible.

However, since the OFDM technology processes the frequency and magnitude of the signal at the time of modulation and demodulation, spurious phenomenon, interference between adjacent channels, and signal distortion may occur when amplifying the signal.

FIG. 1 is a diagram schematically illustrating a form in which a general power amplifier module (PAM) 20 amplifies an OFDM signal.

Referring to FIG. 1, the modulator 10 of the communication system modulates a digital signal in the form of an analog signal according to the OFDM signal standard, and the modulated signal is transmitted to the amplification module 20.

The amplification module 20 sufficiently amplifies the modulated signal to a transmittable size, and the filter 30 removes the signal of the noise component generated during the amplification and transmits the signal to the antenna stage. The OFDM signal is momentarily high on the time axis. The characteristic that power signal is generated, that is, "Peak to Average" has a large characteristic (see waveform "A").

The amplification module 20 has a limitation in the dynamic range of the amplification operation. Therefore, when the OFDM signal is amplified (B), a signal region C having a high power is saturated without being sufficiently amplified.

That is, according to the electric field strength, there is a problem in that the characteristics of the active elements constituting the communication system are deteriorated, and the linearity of the amplification module 20 may be distorted according to the characteristics of the OFDM signal. The transmission and reception sensitivity of the system is reduced.

In the frequency domain, the saturation occurs during amplification. The difference between the EVM (Error Vector Magnitude) between the reference waveform and the measured waveform is the IQ 'of the modulated symbol in relation to the M-ary I / Q modulation scheme. The linearity of the power amplifier is reduced due to the poor characteristics shown on the "Plot" plot, and the ACP (Adjacent Channel Power) generation of intermodulation in the bandwidth of the channel signal with multiple frequencies and intrusion into adjacent channel frequencies to form unnecessary energy. This incomplete phenomenon occurs).

According to an embodiment of the present invention, when amplifying a signal having a "Peak to Average" characteristic such as an OFDM signal, a signal having a high power value is instantaneously amplified without saturation, thereby providing an amplification apparatus for preventing a distortion of the signal do.

Amplifying apparatus according to the present invention comprises a coupling unit for coupling a signal; A detector configured to detect a power level of the coupled signal to generate a detection signal; A signal limiter for limiting a portion of the coupled signal that is greater than a predetermined power level; A comparator configured to generate a control signal by comparing the sensed signal of the detector and an output signal of the signal limiter; An attenuation unit attenuating the signal output from the coupling unit according to the control signal; And an amplifier configured to amplify the signal output from the attenuator.

Hereinafter, an amplifier according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In describing an embodiment of the present invention, the amplifying device includes a communication system using an Orthogonal Frequency Division Multiplexing (OFDM) signal, For example, it is assumed that it is configured at the transmission path end of the WLAN communication system.

2 is a block diagram schematically illustrating the components of an amplifying apparatus 100 according to an embodiment of the present invention.

Referring to FIG. 2, the amplification apparatus 100 according to the embodiment of the present invention includes a coupling unit 110, a signal limiter 120, a detector 130, a comparator 140, and attenuation. A unit 150, the amplifier 160, and the transmission path stage of the WLAN communication system is a modulator 200, up-converter (300), local oscillator (320) ).

The modulator 200 receives a digital signal from a controller (not shown) and modulates the digital signal into an analog signal to conform to the OFDM signal standard. In this case, a symbolized signal is transmitted by using an OFDM modulation scheme. Modulate with.

According to the OFDM signal standard, a signal standard is defined according to a time division technique, a frequency division technique, a space division technique, a symbolization, a data frame structure, and the like.

Briefly, the OFDM signal is composed of k test frames (T _F ), and the test frame is composed of N time slots (T _S ). In addition, a null time region exists between the test frames T _F , and a time frequency phase reference (TFPR) block follows the null time region.

The TFPR block distinguishes test frames, contains information about the test frame, and is located next to the TFPR block, which symbolizes data.

Such an OFDM signal can carry a plurality of data in a carrier signal of an orthogonal component, and has a characteristic of "Peak to Average" because modulation is processed in the magnitude and frequency of the signal.

Therefore, when a transmission signal is directly input to the amplifying unit 160 after crossing the modulator 200 and the upconverter 300, a signal region having a high power value instantaneously (hereinafter, referred to as a “high power signal”) Saturation can be reached and thus a situation in which the signal is difficult to recover properly can occur.

For this reason, the amplifying apparatus 100 according to the embodiment of the present invention couples the transmission signal processed by the modulator 200 to determine whether a high power signal exists, and if a high power signal exists, a corresponding signal section. By attenuating the power, the signal is prevented from saturation during amplification.

The coupling unit 110 is coupled between the modulation unit 200 and the up-converter 300 of the transmission path, and coupled to the modulated transmission signal transmitted to the signal limiting unit 120 and the sensing unit 130 do.

The coupling unit 110 may be configured using a coupling capacitor or a directional coupler. For example, in the case of a coupling capacitor, a dielectric having a predetermined dielectric constant is provided, thereby losing the original RF signal. The transmission signal can be coupled without giving.

In addition, when using a directional coupler, a waveguide having an input port, a through port, an output port, an isolation port, and four ports may be used, and the isolation port is connected to the ground terminal through the resistor 112.

The signal limiter 120 performs a function of cutting a predetermined signal region of the transmission signal transmitted from the coupling unit 110. The signal region to be cut refers to the high power signal region described above (that is, high power). Signal can be artificially saturated).

3 is a circuit diagram schematically showing the components of the signal limiting unit 120 of the amplifying apparatus 100 according to the embodiment of the present invention.

Referring to FIG. 3, the signal limiter 120 includes two transistors Q1 and Q2, three capacitors C1, C2 and C3, and a coupled diode D.

The two transistors Q1 and Q2 determine the range of the frequency domain to be preserved without cutting out, whereby the range can be precisely adjusted by the capacitors C1, C2 and C3. The coupled diode D performs a function of cutting (removing) a signal exceeding a range of the frequency domain to be preserved, that is, a signal determined to be a high power signal.

The detector 130 generates a detection signal by detecting a power level of the coupled transmission signal, and may be configured as a circuit including a log amplifier.

The comparator 140 compares the output signal of the detector 130, that is, the output signal of the signal limiter 120, that is, the output signal of which the high power signal is limited, and detects to match the reference level of the two signals. Resistors 132 and 134 are connected to the output terminal of the unit 130.

4 is a graph schematically illustrating a form in which coupling signals processed by the amplifying apparatus 100 according to an exemplary embodiment of the present invention are compared.

Referring to FIG. 4, the graph “V1” is a graph measuring the sensing signal of the sensing unit 130, and the graph “V2” is a graph measuring the output signal of the signal limiting unit 120.

The graph "Vo" is a graph measuring the signal output from the comparator 140 after comparing the output signal of the detector 130 with the output signal of the signal limiter 120.

For example, the comparator 140 may include an OP amplifier.

The comparison unit 140 may have a first comparison signal (a voltage range of about 0V or more and less than 0.5V) in a signal section where the output signal of the detector 130 and the output signal of the signal limiter 120 coincide. And a second comparison signal (which may have a voltage range of about 0.5V or more and less than 1V) in a signal period where the two signals do not coincide.

Referring to the "Vo" graph of FIG. 4, the comparison unit 140 outputs a 0 V digital signal as a first comparison signal and a 1 V digital signal as a second comparison signal. The two comparison signals are transmitted to the attenuation unit 150 and used as control signals.

Accordingly, the attenuator 150 is not operated in the sections D and F of the first comparison signal, and the attenuator 150 is operated in the section E of the second comparison signal.

On the other hand, the up-converter 300 may be configured using a mixer element, and receives the oscillation frequency signal from the local oscillation circuit 320 and synthesizes a transmission signal passing through the coupling unit 110 into a high frequency signal.

For example, assuming that the signal modulated by the modulator 200 is a signal of about 100 MHz band, the signal synthesized by the upconverter 300 has a high frequency band of about 2.3 GHz.

The attenuator 150 is connected to the up-converter 300 to form part of the transmission path end, and is connected to the comparator 140 to receive a control signal (comparative signal).

The attenuator 150 is not operated when the control signal is the first comparison signal (0V digital signal), but is operated when the control signal is the second comparison signal (digital signal of 1V) to attenuate the power of the high frequency processed transmission signal. Let's do it.

The amplification unit 160 receives the transmission signal from the attenuation unit 150 and performs an amplification operation. As described above, the amplification unit 160 receives the attenuated signal in the high power signal section E, and thus, other signal sections D and F. Even if the amplification operation is performed in the same manner as in (), it is possible to prevent the saturation of the high power signal.

In general, in the case of the communication module provided in the WLAN system, the transmission power is also maintained to the maximum in order to maximize the transmission / reception distance, and the transmission power has a limitation in amplifying.

This is in accordance with the Adjacent Channel Power Ratio (ACPR) standard defined in the IEEE 802.11 standard. The ACPR is a standard for defining a linear characteristic of a power amplifier.

That is, the channel signal is amplified within a predetermined frequency bandwidth, but according to the ACPR regulations, intermodulation occurs in the bandwidth of a channel signal in which several frequencies are concentrated, and this phenomenon invades adjacent channel frequencies to form unnecessary energy.

However, according to the present invention, the phenomenon of saturation of the high power signal can be prevented, so that the linearity of the amplifier 160 can be stably maintained and the increase in the ACP value can be suppressed.

In addition, the EVM value that changes as the power of the amplifier 160 increases may be displayed in the form of polar coordinates, where two polar coordinate points, that is, a theoretical signal point and an actual measured signal point required by the communication system are displayed. This may be represented as an error vector between two signals (for reference, two or more polar points may also be represented).

According to the present invention, since the signal distortion during amplification can be greatly reduced, the separation distance between the two points is reduced, which is interpreted as maintaining the linearity so that the signal amplified by the amplifier 160 is close to the theoretical signal. Can be.

Although the present invention has been described above with reference to the embodiments, these are only examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains may have an abnormality within the scope not departing from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not illustrated. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to the amplifying apparatus according to an embodiment of the present invention, when a signal having a high power value is amplified at an instant relative to the average signal power, the signal may be prevented from saturating, thereby preventing the occurrence of ACP. And has the effect of improving EVM.

In addition, according to an embodiment of the present invention, when the signal is amplified, it is possible to stabilize the linear characteristics of the signal and to prevent the signal from being distorted, thereby improving the transmission and reception sensitivity of the communication system.

Claims (8)

A coupling unit coupling a signal; A detector configured to detect a power level of the coupled signal to generate a detection signal; A signal limiter for limiting a portion of the coupled signal that is greater than a predetermined power level; A comparator configured to generate a control signal by comparing the sensed signal of the detector and an output signal of the signal limiter; An attenuation unit attenuating the signal output from the coupling unit according to the control signal; And And an amplifier for amplifying the signal output from the attenuator. The method of claim 1, wherein the coupling portion An amplifier device electrically connected to the output terminal of the modulator. The method of claim 1, wherein the comparison unit And a result of comparing the detection signal with the output signal, and outputting a first comparison signal in a section where the signals match and outputting a second comparison signal in a section where the signals do not match. The method of claim 3, The first comparison signal is a signal having a voltage of 0V to 0.5V, The second comparison signal is an amplifier having a voltage of 0.5V to 1V. The method of claim 3, wherein the attenuation portion Electrically connected to the coupling part and the comparison part; And an amplifying device operating when a control signal corresponding to the second comparison signal is transmitted. The method of claim 1, And an up-converter for raising a transmission signal to a high frequency band in a line section between the coupling part and the attenuation part. The method of claim 1, wherein the comparison unit An amplifier comprising an op amp. The method of claim 1 wherein the signal is An amplifying device which is an orthogonal frequency division multiplexing (OFDM) signal.

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