Amplification equipment

Abstract

To reduce waveform distortion in an amplifying device.SOLUTION: An amplifying device according to the present invention comprises a pulse signal acquisition unit, a dummy signal generation unit, a compositing unit, an amplifier, and a separation unit. The pulse signal acquisition unit acquires the desired signal, which is a pulse signal to be amplified. The dummy signal generation unit generates a dummy signal. The compositing unit composites dummy signals before and after the desired signal, and outputs a composited signal. The amplifier amplifies the composited signal, and outputs an amplified composited signal. The separation unit extracts and outputs an amplified desired signal, which is a signal obtained by amplifying the desired signal, from the amplified composited signal. The power of the composited signal is the power at which the amplification unit operates nonlinearly. The power of the composited signal is constant in the time range obtained by adding a predetermined time to the time when the desired signal is present.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a high-output amplifier for amplifying a pulse signal, and a transmission / reception system using the amplifier. [Background technology]

[0002] As a high-output amplifier for amplifying a pulse signal, an amplifier that generates a transmission signal for a radar is known as a conventional technology. For example, many radars using semiconductor amplifiers use a chirp signal in which the frequency is linearly changed within the pulse signal section as the transmission signal, and perform pulse compression processing on the receiving side to obtain detection distance performance comparable to that of an electron tube. For semiconductor amplifiers, GaN (Gallium Nitride) is often used, which has excellent thermal conductivity, band gap, and pressure resistance, and can handle large power even with a size equivalent to GaAs. Literature on such amplifiers using GaN includes Non-Patent Documents 1 to 4.

[0003] Also known is the technology of a pulse transmission device, disclosed in Patent Document 1, which shows that a dummy pulse is inserted into the gap between pulses in a pulse train or immediately before the first pulse, or both, in order to reduce amplitude and phase distortion of the pulses. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-116769 [Non-patent literature]

[0005] [Non-Patent Document 1] SC Cripps, RF Power Amplifiers for Wireless Communications. Artech House, Boston, London, 2006. [Non-Patent Document 2] H. Chen, LJ Jiang, XF Ji, YX Zhang, “Design of an X-band pulsed SSPA based on a cascade technique”, Proc. IEEE Int. Conf. Microw. Technol. Comput. Electromagn, pp. 152-155, May 2011. [Non-Patent Document 3] CK Chu, HK Huang, HZ Liu, CH Lin, CH Chang, CL Wu, CS Chang, YH Wang, “An [Non-Patent Document 4] C. Wang, Y. Xu, X. Yu, C. Ren, Z. Wang, H. Lu, T. Chen, B. Zhang, and R. Xu, “An electrothermal model for empirical large-signal modeling of AlGaN / GaN HEMTs including self-heating and ambient temperature effects,” IEEE Trans. Microwave Theory Tech., vol. 62, no. 12, pp. 2878-2887, Dec. 2014. Summary of the Invention [Problem to be solved by the invention]

[0006] However, in semiconductor amplifying elements using GaN, the gain and efficiency change according to the output power (see Non-Patent Document 1). The high-power operation characteristic of GaN amplifiers is in the non-linear region, and it is not uncommon for the gain to decrease by 3 dB or more at maximum power output compared to the linear region (see Non-Patent Documents 2 and 3). In addition, changes in power efficiency result in changes in the amount of heat generated around the device. This temperature change is determined by the structure of the semiconductor device and does not match the envelope of the RF signal. Therefore, hysteresis occurs in GaN amplifiers, which is called the memory effect and affects the linearity of the output signal (see Non-Patent Document 4). It is believed that individual differences between elements in the operation of multiple elements, as well as changes in signal specifications and ambient temperature, also affect these characteristics.

[0007] Furthermore, since an amplifier that handles high output power generates a large amount of heat, inserting a dummy signal entirely between the pulses would result in a serious heat generation problem, making the technology of Patent Document 1 unusable.

[0008] An object of the present invention is to reduce waveform distortion in an amplifier that amplifies a pulse signal in a nonlinear region. [Means for solving the problem]

[0009] The first amplifying device of the present invention includes a pulse signal acquiring unit, a dummy signal generating unit, a combining unit, an amplifier, and a separating unit. The pulse signal acquiring unit acquires a desired signal, which is a pulse signal to be amplified. The dummy signal generating unit generates a dummy signal. The combining unit combines dummy signals before and after the desired signal, and outputs a combined signal. The amplifier amplifies the combined signal, and outputs an amplified combined signal. The separating unit extracts and outputs an amplified desired signal, which is a signal obtained by amplifying the desired signal, from the amplified combined signal. The power of the combined signal is the power at which the amplifying unit operates nonlinearly. Also, the power of the combined signal is constant in a time range obtained by adding a predetermined time to the time when the desired signal is present.

[0010] The second amplifying device of the present invention includes a pulse signal acquiring unit, a dummy signal generating unit, a combining unit, and an amplifier. The pulse signal acquiring unit acquires a desired signal, which is a pulse signal to be amplified. The dummy signal generating unit generates a dummy signal. The combining unit combines dummy signals before and after the desired signal, and outputs a combined signal. The amplifier amplifies the combined signal, and outputs an amplified combined signal. The dummy signal is a signal that can be separated from the desired signal. The power of the combined signal is the power at which the amplifying unit operates nonlinearly. Furthermore, the power of the combined signal is constant in a time range obtained by adding a predetermined time to the time when the desired signal is present. Effect of the Invention

[0011] According to the amplifier device of the present invention, a dummy signal is placed in a portion where the shape of a pulse signal is affected by nonlinearity and transient response, and the dummy signal is removed after amplification, thereby enabling amplification with reduced distortion of the pulse signal. [Brief description of the drawings]

[0012] [Figure 1] 13 is a graph showing experimental results of input / output characteristics when a pulse signal is input to an amplifier. [Diagram 2] FIG. 2 is a graph showing the results of measuring the output when a pulse signal is input to an amplifier having the characteristics shown in FIG. [Diagram 3] A diagram showing the rise and fall parts of Figure 2 enlarged on the horizontal axis. [Figure 4] A diagram showing the difference between the simulation considering only nonlinearity and the experimental measurement results. [Diagram 5] FIG. 3 shows the experimental results of pulse compression performed on the signal in FIG. 2. [Figure 6] FIG. 2 is a diagram showing an example of the functional configuration of the amplifier device according to the first embodiment. [Figure 7] FIG. 2 is a diagram showing an image of the operation of the amplifier device of the present invention. [Figure 8] FIG. 4 is a diagram showing the result of amplifying a pulse signal using the amplifier device of the present invention. [Figure 9] A diagram showing an enlargement of the horizontal axis of the rising and falling parts of Figure 8. [Figure 10]FIG. 9 is a diagram showing the difference between before (FIG. 3) and after (FIG. 9) application of the present invention. [Figure 11] FIG. 9 shows the experimental results of pulse compression performed on the signal in FIG. 8. [Figure 12] FIG. 11 is a diagram showing an example of the functional configuration of a transmission / reception system according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail. Note that components having the same functions are given the same reference numbers and duplicated explanations will be omitted. EXAMPLES

[0014] <Analysis> Figure 1 shows the experimental results of the input / output characteristics when a pulse signal is input to the amplifier. The horizontal axis is the power of the input signal, and the vertical axis is the power of the output signal. In the experiment, the preamplifier was a GaAs amplifier, and the driver amplifier and power amplifier were GaN amplifiers, and the amplifier was configured with these amplifiers connected in series in three stages. The pulse signal had a center frequency of 9.41 GHz, a pulse width of 4 μs, a sweep frequency width of 15 MHz, a repetition frequency of 2600 Hz, and a rise and fall time of 0.4 μs. When the input power was -23 dBm, the output power was 43 dBm and the gain was 66 dB. It can be seen that the amplifier operates linearly in this vicinity. When the input power was -15 dBm, the output power was 50 dBm and the gain was 65 dB. When the input power was -10 dBm, the output power was 51 dBm and the gain was 61 dB. It can be seen that the amplifier operates nonlinearly in this vicinity. At an input power of -10 dBm, the gain is reduced by 5 dB compared to operation in the linear region.

[0015] Figure 2 shows the actual measurement results of the output when a pulse signal is input to an amplifier with the characteristics of Figure 1. The horizontal axis shows time, and the vertical axis shows normalized amplitude (amplitude with the maximum value of the signal taken as 0 dB). The thin dotted line (shown as "Amp In" in the figure) shows the envelope of the input signal. The long dotted line (shown as "Out (50 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal is 50 dBm. The solid line (shown as "Out (51 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal is 51 dBm. In the following explanation, the term "envelope" may be omitted, but the shape of the signal refers to the shape of the envelope, and the distortion of the signal refers to the distortion of the envelope. Figure 3 shows the horizontal axis of the rising and falling parts of Figure 2 enlarged. Figure 3(A) shows the rising part, and Figure 3(B) shows the falling part. It can be seen that the change in amplitude is steep at the rising and falling edges. In addition, the pulse width at an amplitude 6 dB smaller than the maximum amplitude is widest when the output signal power is 51 dBm. In other words, it can be seen that when operating in the nonlinear region, the amplifier behaves in such a way that the pulse width becomes wider.

[0016] Figure 4 shows the difference between the simulation considering only nonlinearity and the experimental measurement results. The horizontal axis is time, and the vertical axis is normalized amplitude. The fine dotted line (shown as "Amp In" in the figure) shows the envelope of the input signal. The dashed line (shown as "Out (43 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal is 43 dBm. The long dotted line (shown as "Out (50 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal is 50 dBm. Figure 4(A) shows the simulation result considering only the nonlinearity characteristics shown in Figure 1. Figure 4(B) shows the analysis of the rise characteristics shown in Figure 3(A). Note that in Figure 4(A), the envelope of the input signal (fine dotted line) overlaps with the envelope of the output signal (dashed dotted line) when the power of the output signal is 43 dBm, and cannot be recognized. In order to explain the effects of nonlinearity and the transient response, Figure 4(B) only shows the envelope of the input signal (fine dotted line) and the envelope of the output signal when the power of the output signal is 51 dBm (solid line). If only the effects of nonlinearity are considered, as the output power increases, the rise of the amplitude becomes steeper and the pulse width tends to become wider. However, no delay occurs with respect to the input signal. On the other hand, if only the delay is taken into consideration, the phenomenon of the pulse width becoming wider cannot be explained. It is believed that the measurement results shown in Figure 4(B) are the result of the effects of both nonlinearity and the transient response.

[0017] Figure 5 shows the experimental results of pulse compression of the signal in Figure 2. For pulse compression, a mismatched filter based on Reference 1 (JE Cilliers, JC Smit, “Pulse Compression Sidelobe Reduction by Minimization of Lp-Norms”, IEEE Trans. AERO, Vol. 43, No. 3, pp. 1238-1247, July 2007.) was used. In the case of radar, pulse compression is a process performed by the receiver. Distortion of the pulse waveform caused by the amplifier deteriorates the signal-to-noise ratio (SNR) of the pulse compression output. In the example in Figure 5, the SNR is about 45 dB. It was also found that in the nonlinear region, the greater the power of the input signal, the greater the deterioration.

[0018] <The present invention> Fig. 6 shows an example of the functional configuration of the amplifying device of the present invention. Amplifying device 100 includes pulse signal acquiring section 110, dummy signal generating section 120, combining section 130, amplifier 140, and separating section 150. Fig. 7 shows an image of the operation of the amplifying device of the present invention. In the waveforms shown in the figure, the horizontal axis is time, and the vertical axis is amplitude normalized by the maximum value. In the waveforms in the figure, the solid line represents the desired signal or amplified desired signal, the fine dotted line represents the dummy signal or amplified dummy signal, and the dashed line represents the combined signal or amplified combined signal. However, in the amplified signal and the separated signal, the desired signal input as reference information is shown by the two-dot dashed line.

[0019] The pulse signal acquiring unit 110 acquires a desired signal, which is a pulse signal to be amplified. The term "acquire" means that the desired signal may be acquired by some method, and includes both the pulse signal acquiring unit 110 receiving a desired signal from the outside and the pulse signal acquiring unit 110 generating a desired signal.

[0020] The dummy signal generating unit 120 generates a dummy signal. The dummy signal is a signal that can be separated even when combined with a desired signal. For example, the dummy signal may be a signal whose frequency is sufficiently different from that of the desired signal. In this case, the desired signal alone can be extracted (separated from the dummy signal) from the combined signal of the desired signal and the dummy signal by using a low-pass filter or a high-pass filter. The modulation method may be different between the desired signal and the dummy signal. For example, the desired signal may be modulated by the orthogonal frequency division multiplexing (OFDM) modulation method, and the dummy signal may be modulated by quadrature phase shift keying (QPSK). In this case, the desired signal can be extracted (separated from the dummy signal) from the combined signal of the desired signal and the dummy signal by using the orthogonal frequency division multiplexing modulation method.

[0021] The combiner 130 combines dummy signals before and after the desired signal and outputs a combined signal. The power of the combined signal is the power at which the amplifier 140 operates nonlinearly. In addition, the power of the combined signal is constant in a time range obtained by adding a predetermined time to the time when the desired signal exists. In other words, the dummy signal generator 120 generates a dummy signal so that the power of the combined signal is constant at timings arranged before and after the desired signal. For example, the timing at which the pulse signal acquirer 110 acquires the desired signal and the power of the desired signal are determined in advance, and the dummy signal generator 120 generates a dummy signal based on the timing and power. Note that it is sufficient that the power is constant to the extent that the distortion reduction requirement required of the amplifier 100 is satisfied. The combined signal (dash line) on the input side of the amplifier 140 in FIG. 7 has a constant power in a range wider than the time when the desired signal exists. For example, in the amplifier whose characteristics are shown in FIG. 1, the power of the desired signal is about -10 dBm (nonlinear region), and by adding dummy signals before and after it, a composite signal is generated so that it is -10 dBm over a wide range.

[0022] The amplifier 140 amplifies the composite signal and outputs an amplified composite signal. In the amplified composite signal (dash-dotted line) at the output side of the amplifier 140 in FIG. 7, distortion as shown in FIG. 3 occurs at the rising and falling parts. The part where this distortion occurs is the amplified dummy signal part where the dummy signal is amplified. On the other hand, even if the signal is amplified in the nonlinear region, distortion does not occur in the part where the power is constant because the gain and the amount of heat generated are constant. Therefore, distortion does not occur in the range where the desired signal exists. The above-mentioned "predetermined time" added to the time when the desired signal exists is sufficient to be a time that prevents the desired signal from being affected by nonlinearity and transient response, and may be set appropriately. For example, in the case of the example of FIG. 3, the "predetermined time" is sufficient to be about 1 μs. In this way, the "predetermined time" may be a time added to stabilize the nonlinear operation of the amplifier 140. If the predetermined time is set to be a time added to stabilize the nonlinear operation of the amplifier 140, it also has the effect of reducing the heat generated by the amplifier 140 to amplify the dummy signal. Although a semiconductor amplifying element may be used for the amplifier 140, if a GaN amplifier is used, it is easy to output a high-power pulse signal by utilizing the nonlinear region. Note that a "GaN amplifier" refers to an amplifier that includes a GaN amplifying element. For example, an amplifier in which the preamplifier used in the experiment is a GaAs amplifying element, the driver amplifier and the power amplifier are GaN amplifying elements, and these are connected in series in three stages is included in the "GaN amplifier".

[0023] The separator 150 extracts an amplified desired signal, which is a signal in which the desired signal is amplified, from the amplified composite signal, and outputs the amplified desired signal. When the frequency of the dummy signal is higher than the frequency of the desired signal, the separator 150 may be a low-pass filter. When the frequency of the dummy signal is lower than the frequency of the desired signal, the separator 150 may be a high-pass filter. When the desired signal is modulated, the separator 150 may extract the amplified desired signal according to the modulation method.

[0024] According to the amplifier device of the present invention, a dummy signal is placed in a portion where the shape of a pulse signal is affected by nonlinearity and transient response, and the dummy signal is removed after amplification, thereby enabling amplification with reduced distortion of the pulse signal.

[0025] <Demonstration experiment> FIG. 8 is a diagram showing the result of amplifying a pulse signal with the amplifier of the present invention. The horizontal axis shows time, and the vertical axis shows normalized amplitude (amplitude with the maximum value of the signal taken as 0 dB). The thin dotted line (shown as "Amp In" in the diagram) shows the envelope of the input signal. The long dotted line (shown as "Out (50 dBm)" in the diagram) shows the envelope of the output signal when the power of the output signal is 50 dBm. The solid line (shown as "Out (51 dBm)" in the diagram) shows the envelope of the output signal when the power of the output signal is 51 dBm. In the experiment, an amplifier having the characteristics of FIG. 1 was used as the amplifier 140, and the pulse signal acquisition unit 110 acquired the same pulse signal as in the analysis experiment shown in FIG. 2. In this experiment, an unmodulated pulse signal with a center frequency different from that of the desired signal was used as the dummy signal, and the separation unit 150 removed the dummy signal using a bandpass filter. FIG. 9 is a diagram in which the horizontal axis of the rising and falling parts of FIG. 8 is enlarged. FIG. 9(A) shows the rising portion, and FIG. 9(B) shows the falling portion.

[0026] FIG. 10 shows the difference between before (FIG. 3) and after (FIG. 9) application of the present invention. FIG. 10(A) shows the rising portion, and FIG. 10(B) shows the falling portion. The thin dotted line (shown as "Amp In" in the figure) shows the envelope of the input signal. The long dotted line (shown as "Before (51 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal in FIG. 3 is 51 dBm. The solid line (shown as "Proposed (51 dBm)" in the figure) shows the envelope of the output signal when the power of the output signal in FIG. 9 is 51 dBm. It can be seen that when the present invention is applied, the change in amplitude is close to the input signal, both in the rising and falling portions.

[0027] Figure 11 shows the experimental results of pulse compression of the signal in Figure 8. For pulse compression, we used a mismatched filter based on Reference 1, as in the analysis. In the example in Figure 11, the SNR is about 50 dB, which is an improvement of about 5 dB compared to the example in Figure 5.

[0028] Experiments have also demonstrated that the present invention enables amplification with reduced distortion of the pulse waveform. The present invention does not require any changes or additions to the configuration of the amplifier itself. Furthermore, even if there are changes in the signal specifications or the ambient temperature, there is no need to change the configuration of the present invention. These are also advantages of the present invention.

[0029] [Variation 1] In the first embodiment, it is assumed that the power of the desired signal is determined in advance. In this modification, the desired signal is a continuous pulse signal with a time interval. The power of the pulse signal changes slightly due to temperature changes, etc. Therefore, the amplifying device 100 of this modification also includes a power detection unit 160. The power detection unit 160 detects the power of the desired signal. The dummy signal generating unit 120 may generate a dummy signal based on the power detected by the power detection unit 160. For example, the dummy signal generating unit 120 may generate a dummy signal by adjusting the power based on the power of a predetermined number of the most recent desired signals. In this way, based on the power of the most recent desired signal, it is possible to respond to a gradual change in power, such as a change in power due to a temperature change.

[0030] [Variation 2] In the first embodiment, the amplifier 100 includes the separator 150. However, in the case where there is a transmitter and a receiver like a radar, the receiver may include the separator. FIG. 12 shows an example of a functional configuration of a transmission / reception system of the second modification. The transmission / reception system 230 includes a transmitter 210 and a receiver 220 like a radar. The transmitter 210 includes an amplifier 101 and a transmitter 180. The receiver 220 includes a receiver 190 and a separator 150. The amplifier 101 includes a pulse signal acquirer 110, a dummy signal generator 120, a combiner 130, and an amplifier 140. The pulse signal acquirer 110, the dummy signal generator 120, the combiner 130, and the amplifier 140 are the same as those in the first embodiment. The transmitter 180 transmits an amplified composite signal. The receiver 190 receives the amplified composite signal. In the case of a radar, the receiver 190 receives the reflected amplified composite signal. The separator 150 extracts the signal to be amplified from the received amplified composite signal. Note that the processing before the pulse signal acquirer 110 acquires the desired signal and the processing after the separator 150 extracts the signal to be amplified may be processing specific to each transmission / reception system as appropriate. Therefore, the configuration for performing such processing is not shown in FIG. 12. Also, it may be combined with the first modification.

[0031] In this modified example, a dummy signal is placed in a portion where the shape of the pulse signal is affected by the effects of nonlinearity and transient response, and the dummy signal is removed after amplification, so that the pulse signal can be amplified with reduced distortion. [Explanation of symbols]

[0032] 100, 101 Amplification device 110 Pulse signal acquisition unit 120 Dummy signal generating section 130 Synthesis section 140 Amplifier 150 Separation section 160 Power detection unit 180 Transmitter unit 190 Receiving section 210 Transmitting device 220 Receiving device 230 Transmitting / receiving system

Claims

1. a pulse signal acquiring unit that acquires successive pulse signals having a time interval as a desired signal to be amplified for each pulse signal; a dummy signal generating unit that generates a dummy signal; a combining unit that combines the dummy signal before and after the desired signal and outputs a combined signal; an amplifier that amplifies the composite signal and outputs an amplified composite signal; a power detection unit that detects the power of the desired signal; Equipped with the dummy signal is a signal whose frequency is sufficiently different from that of the desired signal, the power of the composite signal during the time when the desired signal is present is the power at which the amplifier operates nonlinearly; The dummy signal generating unit generates a dummy signal based on the power detected by the power detecting unit so that the power of the composite signal is constant during a time range obtained by adding a predetermined time before and after the time during which the desired signal is present.

1. An amplifier device comprising:

2. 2. The amplifier according to claim 1, The amplifier is a GaN amplifier.

1. An amplifier device comprising:

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