KR20070043324A - Linearized microwave power module - Google Patents

Abstract

The present invention relates to a linearized microwave power module, and more particularly, to a power amplifier having a low noise characteristic and a high linearity by combining a solid state amplifier (SSA) and a predistortion linearizer with a traveling wave tube (TWT). It is about.

The linearized microwave power module according to an embodiment of the present invention has a gain distribution and a low noise figure of a final output stage, an SSA for driving the final output stage, and a gain and output signal phase of the final output stage connected to a rear end of the SSA. A predistortion linearizer having an inverse distortion characteristic opposite to the distortion characteristic of and improving the intermodulation distortion characteristic, and a TWT connected to a rear end of the predistortion linearizer and amplifying a signal of a final output terminal.

Linearized Microwave Power Module (LMPM), SSA, Predistortion Linearizer, TWT.

Description

Linearized Microwave Power Module

1 is a simplified block diagram of a linearized microwave power module according to an embodiment of the present invention;

FIG. 2 is a detailed block diagram of the linearized microwave power module shown in FIG. 1;

3 is a bias circuit diagram applied to the SSA shown in FIG.

4 is a circuit diagram of a 90 ° hybrid coupler provided in the variable phase displacement shown in FIG.

FIG. 5 is a block diagram illustrating the measurement equipment of the linearized microwave power module shown in FIG.

6A and 6B show the output spectrum before and after linearization

7A and 7B show the output spectrum before and after linearization at the 10 dB backoff point.

8A and 8B show the output spectrum before and after linearization at P1 dB point

9 is a noise figure graph of the linearized micro power module according to an embodiment of the present invention

10 is a gain and noise figure of the linearized micro power module according to an embodiment of the present invention

<Description of the symbols for the main parts of the drawings>

100: linearized microwave power module (LMPM) 200: SSA

300: predistortion linearizer 400: TWT

The present invention relates to a linearized microwave power module, and more particularly, to a power amplifier having a low noise characteristic and a high linearity by combining a solid state amplifier (SSA) and a predistortion linearizer with a traveling wave tube (TWT). It is about.

Microwave Power Module (MPM) technology has been growing in the telecommunications satellite market since the 1990s due to the rapid expansion of fixed and mobile communication, TV broadcasting, Internet and multimedia demand.

The MPM has been developed since 1991 for military electronic warfare in the United States and has been monopolizing technology in the United States, Europe and Japan.

The MPM consists of three element technologies: TWT technology, Integrated Electronic Power Conditioner (IEPC) technology, and SSA technology.

The MPM combines the high power, high efficiency and broadband characteristics of the TWT, and combines the low noise and signal processing capabilities of the SSA. The MPM is an advanced high-performance power amplifier module that combines the technical advantages of each by optimally distributing the gain between the TWT and the SSA.

The MPM is a compact, lightweight, high efficiency, low noise RF amplifier that can be used in a variety of high value-added industries such as military communications, military communications, and unmanned aerial communications, as well as satellite communications and satellite broadcasting. As high-speed data transmission is required, the relevant market is expected to expand further.

On the other hand, the main point in the design of the power amplifier is to ensure the linearity between the amplifier input and output signals.

In power amplifier operation, it is common to operate in the vicinity of a saturation region that has a non-linear characteristic to amplify to the maximum output level.

The power amplifier operating near the saturation region has distortions in which the amplitude ratio of the output signal and the conversion phase characteristic are not constant due to its nonlinear characteristics, and intermodulation when two or more carriers are input and amplified in common. Intermodulation Distortion signals are generated, and the intermodulation distortion signals operate in a cross talk.

When the signal to be amplified is a signal having a spread spectrum like the CDMA signal, the nonlinear characteristics of the amplifier cause noise in adjacent channels and also include a lot of noise in its own channel.

Therefore, if the input of the power amplifier having non-linear characteristics is backed off several dB to operate in a relatively linear region, intermodulation distortion noise can be reduced, but the output power is lowered and the output power is increased to the desired level. Since two power amplifiers must be connected and driven in parallel, the entire power amplifier is bulky, the power efficiency is low, and the stability is degraded by requiring a larger capacity power supply.

In addition, the TWT is a power amplifier with a wide band characteristic while having a stable high output in the ultra-high frequency band, but also has a disadvantage in that the linearity as well as noise characteristics are not good.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a microwave power module having a low noise characteristic and a high linearity by combining an SSA and a predistortion linearizer in a TWT.

The linearized microwave power module according to the embodiment of the present invention for achieving the above object has a gain distribution and a low noise figure of the final output stage, the SSA for driving the final output stage, and is connected to the rear end of the SSA and the final A predistortion linearizer having an inverse distortion characteristic opposite to the distortion characteristics of an output stage and an output signal phase and improving intermodulation distortion characteristics, and a TWT connected to a rear end of the predistortion linearizer and amplifying a signal of a final output stage. do.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a simplified block diagram of a linearized microwave power module according to an embodiment of the present invention, and FIG. 2 is a detailed block diagram of the linearized microwave power module shown in FIG.

As shown in FIG. 1, the linearized microwave power module 100 (LMPM) includes an SSA 200, a predistortion linearizer 300, and a TWT 400.

The SSA 200 is used as a driving amplifier of the TWT 400 while allocating the gain of the final output terminal TWT and having a low noise figure.

As shown in FIG. 2, the SSA 200 includes a low noise amplifier 202, a power divider 230, an equalizer 204a and 204b, and a power synthesizer 232.

The low noise amplifier 202 minimizes noise and amplifies gains.

As shown in Equation 1 below, when the amplifier is connected in multiple stages, the noise figure is found that the larger the gain and the smaller the noise figure are, the lower the overall noise figure is.

은 각 단의 증폭기 잡음지수이고,

은 각 단의 증폭기 이득을 나타낸다.here,

Is the amplifier noise figure of each stage,

Denotes the amplifier gain of each stage.

The power divider 230 is a three-port device having one input port and two output ports, and the phase difference between the two output ports is 0 °.

Since the power divider 230 is reversible, the power divider 230 may be used as a power synthesizer 232 having two input ports and one output port.

When power is applied to the input port of the power splitter 210 having a specific impedance (for example, 50 ohms), the power is divided into two parts with the same magnitude and phase of power, and the current is divided between the two output ports. Does not flow

Balanced amplifiers 204a and 204b, which are connected in parallel to the rear ends of the low noise amplifiers 202, are amplifiers for driving the TWT 400, and have good input / output voltage standing wave ratio (VRS) and may be installed in the system. When a single amplifier does not operate, it can secure a certain level of power and high reliability.

3 is a bias circuit diagram applied to the SSA shown in FIG.

As shown in FIG. 3, the bias circuit includes a regulator 210, 218, 220, a negative DC / DC converter 212, a comparator 214, and an AND gate 216.

The bias circuit is a sequential bias circuit that first applies a gate stage and then a drain stage to apply power to the SSA.

The regulators 210, 218, and 220 make the voltage stable and constant.

When an input voltage (for example, 10V) is applied to the regulator 210, it is converted into a predetermined voltage (for example, 6V) by the regulator 210 and separated into two outputs.

One of the predetermined voltages passes a negative DC / DC converter 212 to apply a negative power to the gate terminal.

The other voltage enters the comparator 214 which is a dual OP-AMP, and the signal compared in the comparator 214 enters the AND gate 214 again, and the output of the AND gate 214 is a Q signal to the regulator 220. Is applied.

The regulator 220 receiving the Q signal applies a voltage to the drain terminal.

As a result, after the negative power is first applied, the drain stage has an operation delay time while passing through the comparator 214 and the AND gate 216 to sequentially apply the bias of the gate and drain terminals.

In FIG. 1, the predistortion linearizer 300 has an inverse distortion characteristic opposite to that of the gain and output signal phase of the TWT 400 and is provided in front of the TWT 400 to improve intermodulation distortion characteristics.

The predistortion linearizer is divided into linear and nonlinear paths together, and delay lines 310 and 320, power dividers 340 and 342 as passive elements and power synthesizers 344 and 346, intermodulation signal generators 324 as active elements and variable phase displacements. 312, 326, variable attenuators 314, 328, and drive amplifiers 322, 332, 334.

The power dividers 340 and 342 are three-port devices having one input port and two output ports, and the phase difference between the two output ports is 0 °.

Since the power divider 340 is reversible, it can be used when synthesizing power, that is, the power synthesizers 344 and 346.

When power is applied to an input port with a specific impedance (for example, 50 ohms), the power is distributed in two parts with the same magnitude and phase, indicating that the two output ports do not have current flowing between the two output ports.

The driving amplifier 322 of the nonlinear path amplifies the input signal, and the intermodulation signal generator 324 generates the intermodulation signal by using the nonlinear characteristics of GaAs.

The variable phase transformers 312 and 326 adjust and output a phase through a control voltage while maintaining a constant level without changing the amplitude of the input signal.

In the present invention, a reflective variable phase shifter is realized by using a 90 ° hybrid coupler using a characteristic in which capacitance changes according to a bias voltage under a reverse bias condition using a varistor diode.

4 is a circuit diagram of a 90 ° hybrid coupler provided in the variable phase displacement shown in FIG.

A 90 ° hybrid coupler is a coupler where a phase difference of 90 ° occurs between the pass port and the output of the coupling port.

The 90 ° hybrid coupler is composed of a strip line or a microstrip line. When all ports are matched, the power input to input port 1 is divided into two with 90 ° phase difference between output port 2 and output port 3, This is not combined.

The output ports 2, 3 are always opposite to the registration from the input port and the separation port 4 is located on the same side as the input port 1.

The 90 ° hybrid coupler has good symmetry because all ports can be used as input ports.

The variable attenuators 314 and 328 may be generally implemented using a PIN diode or a GaAs FET. In the present invention, a variable variable attenuator is implemented using a PIN diode.

The PIN diode is a structure in which an I region is inserted between a P and an N region, and has a property in which a resistance value is electrically changed.

In other words, the electrically changing resistance value represents a very high resistance of several thousand Ohms before the bias is applied, but the resistance value decreases with a certain period by the bias applied.

The PIN diode is reduced in gain as the bias voltage changes.

A driving amplifier is provided to raise the power level of the intermodulation signal generated by the intermodulation signal generators 332 and 334 and to maintain a sufficient power level of the intermodulation signal even in a region where the input power is low.

The driving amplifier generates a mixed modulation signal at a sufficient power level even at a low input regardless of input power, and maintains the same power level even in a saturated region. The power level of the modulated signal can be maintained to maintain sufficient power to improve linearity.

The driving amplifier includes a MMIC (Monolithic Microwave IC) amplifier 332 and a GaAs FET amplifier 334 connected in series.

Referring to the operation according to the configuration of the predistortion linearizer 300, the first input RF signal is divided into a linear path and a non-linear path by the power divider 340.

The signal input through the linear path is adjusted through the delay line 310 and the phase and power level through the variable phase shifter 312 and the variable attenuator 314. The signal input into the nonlinear path is divided into sub-paths. A nonlinear component is generated by the intermodulation signal generator 324, and the generated signal is inverted in phase by the variable phase transformer 326, and the power level is adjusted by the variable attenuator 328.

Then, the carrier signal is removed by inputting the power synthesizer 344 together with the signal passing through the delay line 320, which is another subpath, and only the intermodulation signal is inputted to the carrier signal and the power synthesizer 346 that were introduced through the first linear path. The final signal amplified by the driving amplifiers 332 and 334 is input to the TWT 400, which is a target amplifier.

In FIG. 1, the TWT 400 converts the kinetic energy of the electrons into electromagnetic wave energy while amplifying the free electrons accelerated by the potential difference.

Referring to the overall operation according to the configuration of Figure 2, the first input signal is a signal having a low noise figure via the SSA (200) is divided into a linear path and a non-linear path of the predistortion linearizer 300.

 The signal input through the linear path is output to the power synthesizer 346 through the delay line 310, the variable phase transformer 312 and the variable attenuator 314, and the signal input through the nonlinear path passes through the sub path again. The intermodulation signal generator 324 has a nonlinear characteristic.

The intermodulation signals are phase inverted by the variable phase shifter 326 and the output power level is adjusted by the variable attenuator 328.

The inverted signal is combined with the linear outputs of the other subpaths to leave only the phase inverted nonlinear components, which are then combined with the signals of the linear paths and input to the drive amplifiers 332 and 334. The driven signal is used as an input signal of the TWT 400, which is the final output stage amplification, so that the TWT 400 outputs a signal having low noise characteristics and high linearity.

FIG. 5 is a block diagram illustrating the measurement equipment of the linearized microwave power module shown in FIG.

In order to measure (simulate) the linearized output signal of the linearized microwave power module according to an embodiment of the present invention, a signal generator 502, a power supply 504, 506, 508, a spectrum analyzer 512, and an attenuator 510 are provided. .

6A and 6B are output spectra before and after linearization.

5 shows the spectrum before linearization and the spectrum after linearization at a ton interval of 5 MHz at a center frequency of 9.5 GHz as a result of simulation using the measuring equipment of FIG. 5.

7A and 7B show the output spectrum before and after linearization at the 10 dB backoff point.

The back-off refers to operating in a linear region that can allow the degree of distortion by lowering the input level in the power amplifier due to the nonlinear nature of the transistor.

In FIG. 7A, an output characteristic of 19 dBc is shown before linearization at 10 dB backoff point, and in FIG. 7B, an output characteristic of 52.5 dBc is shown after linearization at 10 dB backoff point.

8A and 8B show the output spectra before and after linearization at the P1 dB point.

FIG. 8A shows an output characteristic of 12 dBc at the P1 dB point (1 dB compression point) as the output spectrum before linearization, and FIG. 8B shows an output characteristic of 34 dBc at the P1 dB point as the output spectrum after linearization. .

9 is a noise figure graph of the linearized micro power module according to an embodiment of the present invention.

9 has a noise figure of 27 dB at the center frequency of 9.5 GHz when only the TWT 400 is used, and has a noise figure of 10 dB when the SSA 200 and the TWT 400 are interlocked. In the microwave power module 100 including the distortion linearizer 300 and the TWT 400, a noise figure of 2.2 dB may be measured.

10 is a gain and noise figure of the linearized micro power module according to an embodiment of the present invention.

The total gain of 63dB and the noise figure of 2.2dB are measured, and the calculated value by the cascade noise equation of Equation 1 is 2.25dB at 9.5GHz, which is in agreement with the 2.2dB measured value.

Embodiments of the present invention are disclosed in the drawings and the detailed description, and the specific terms used above are used only for the purpose of describing the present invention, and are used to limit the scope of the present invention as defined in the meaning or claims. It is not.

Therefore, those skilled in the art can be various modifications and other equivalent embodiments from this, and the true technical protection scope of the present invention should be determined by the technical spirit of the claims.

As described above, according to the present invention, the SSA and the predistortion linearizer are combined with the TWT to have low noise characteristics and high linearity.

In addition, according to the present invention, by securing the technology of the microwave power module that combines only the advantages of the vacuum power amplifier TWT and semiconductor power amplifier SSA, and applying a linearization technology to improve the TWT linearity in the microwave power module technology in the future It can be used in various ways in the development of new technologies that combine power amplifier technology and semiconductor technology.

Claims (11)

A solid state amplifier (SSA) which drives a final output stage and has a gain distribution and a low noise figure of the final output stage; A predistortion linearizer connected to a rear end of the SSA and having an inverse distortion characteristic opposite to a distortion characteristic of a gain and an output signal phase of the final output terminal and improving intermodulation distortion characteristics; And And a traveling wave tube (TWT) connected to a rear end of the predistortion linearizer for amplifying a signal of a final output terminal. The method of claim 1, The SSA includes a low noise amplifier for minimizing noise and amplifying a gain, and a balanced amplifier for driving the TWT. The method of claim 2, The balanced amplifier is a linearized microwave power module, characterized in that the two amplifiers are connected in parallel to the rear end of the low noise amplifier outputs a predetermined level or more power. The method according to any one of claims 1 to 3, Linearized microwave power module, characterized in that to apply a bias to the drain stage after applying a bias to the power supply to the SSA. The method according to any one of claims 1 to 3, The predistortion linearizer includes a linear path in which a signal is delayed and phase and power levels are adjusted; Linearized microwave power module characterized in that it is divided into a non-linear path having a first sub-path delayed signal, and a second sub-path for generating a signal of a non-linear component and the phase and power level of the generated signal is adjusted. . The method of claim 5, The linear path includes a delay line for delaying an input signal; A variable phase shifter that maintains a constant amplitude of the input signal and outputs a phase adjusted through a control voltage; The linearized microwave power module, characterized in that the variable attenuator for adjusting the power level by reducing the resistance value for a certain period by the bias applied. The method according to claim 5 or 6, A second modulated signal generator for generating a mixed modulated signal of a nonlinear component in a second sub path of the nonlinear path; A variable phase shifter that maintains a constant level of the intermodulation signal and outputs an inverted phase through a control voltage; Linearized microwave power module, characterized in that the variable attenuator for adjusting the power level by reducing the resistance value for a certain period by the bias applied. The method of claim 7, wherein And a driving amplifier at a rear end of the linear path and the nonlinear path to amplify the power level of the intermodulation signal to maintain a sufficient power level of the intermodulation signal even in a region where the input power is low. The method of claim 8, The driving amplifier is a linearized microwave power module, characterized in that the MMIC amplifier and the GaAs FET amplifier is connected in series. The method of claim 5, The linear path and the nonlinear path, or the first sub path and the second sub path, are three-port elements having one input port and two output ports, and the signal is generated by a power divider having a phase difference of 0 ° between the two output ports. Linearized microwave power module, characterized in that the distribution. The method of claim 10, The linearized microwave power module, characterized in that the output of the linear path and the non-linear path or the output of the first sub path and the second sub path is synthesized by a power synthesizer.

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