JP3105820B2 - Intermodulation distortion reduction circuit for wireless device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermodulation distortion reducing circuit, and more particularly to a circuit for reducing intermodulation distortion generated by interference between a plurality of transmitting units in a radio apparatus.

[0002]

2. Description of the Related Art Normally, when a plurality of interfering signals are applied to a semiconductor transistor or the like of an active element, a new frequency component is generated due to a combination of signals on an input side due to nonlinearity of a transistor circuit. This phenomenon is called intermodulation distortion or simply intermodulation. Generally, VHF or U
In the HF, frequencies are allocated at equal intervals in the same area, and thus are susceptible to this intermodulation interference.

[0003] In recent years, there has been an increasing number of cases where a mobile radio and a base station corresponding to the mobile radio are integrally combined with a receiving unit and a transmitting unit using a common antenna. Such a prior art is disclosed in Japanese Patent Application Laid-Open No. 2-94.
No. 821. In this publication, since the output from the transmission unit is input to the reception unit as an interference wave and the characteristics of the reception unit deteriorate, the interference is removed by the configuration shown in FIG. This publication describes a circuit that reduces interference of a transmission signal with a reception unit in a wireless device. In FIG. 6, an input terminal 71 from the modulator MOD,
The transmission side is composed of a transmission IF panel 72, an up-converter 73, a high-frequency amplifier 74, and a transmission band-pass filter 75, and a reception-side band-pass filter 77, a down-converter 78, a reception IF panel 79, and an output terminal 80 to a demodulator DEM. Constitute the receiving side. in addition,
The signal is branched to the output side of the transmission band-pass filter 75 by the signal branching coupler 81, passes through the band-pass filter 77 a, the variable resistance attenuator 82, and the phase shifter 83, and is combined with the reception signal by the signal combining coupler 84. A fork is formed. The bandpass filter 77a has the same frequency characteristics as the transmission bandpass filter 75,
The amount of leakage of the transmission output that enters around 6 is
This has the same frequency characteristics as the interference wave that has passed through the reception-side bandpass filter 77. The principle of the interference wave elimination by the above configuration is that the transmission signal is detected by the coupler 81, passed through the band-pass filter 77a, and then the phase-shifted signal is shifted by the phase shifter 83 to the signal combining coupler 84.
A method of combining the received signal with the received signal and canceling the transmitted signal that has interfered is adopted. In this case,
This is an interference reduction circuit between the transmitting and receiving units. Therefore, although it is similar in principle to the present example for the purpose of reducing interference between transmitting units, its purpose and application are different.

[0004] In addition, a general circuit method will be described. For example, in the case of transmitting in all directions as space diversity, in a radio apparatus having a plurality of transmission units, a plurality of transmission signals are output from the same antenna. In this case, each transmission signal may wrap around to other transmission units, causing intermodulation distortion.To prevent this, back isolation is performed by a transmission signal combining circuit or isolator to attenuate other transmission interference signal levels. I was letting it.

[0005]

However, each of the transmission signals output from the plurality of transmission units goes to the power amplifiers of the other transmission units and interferes with each other. Is deteriorated.

[0006] Further, the wraparound level of other transmission signals depends on the back isolation of the transmission wave synthesis circuit and the isolator, and is affected by the characteristics of the components themselves.
The inter-modulation distortion characteristics vary and the transmission characteristics are not stable.

From the above, it is an object of the present invention to stably obtain good intermodulation distortion characteristics irrespective of variations in component characteristics, that is, to reduce intermodulation distortion.
Further, the object of the present invention is to reduce the cost of components because the ratio of relying on component characteristics is reduced and component standards can be relaxed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and combines two transmission signals output from two transmission units, A and B, using an output combiner to form one transmission signal. In an intermodulation distortion reduction circuit of a wireless device output from an antenna end, a phase shifter and a level shifter that have a coupler in front of a power amplifier of the instep A transmission unit and that phase-shifts a part of the instep transmission signal detected from the coupler A variable attenuator that performs a phase shift and a level adjustment of a part of the transmission signal, and inputs the phase-shifted and level-adjusted part of the transmission signal to the second synthesis unit. It is characterized in that it is overlapped with a transmission signal and amplified by a power amplifier.

Further, in the intermodulation distortion reducing circuit of the wireless device, the output combiner for combining the transmission signals of the first and second parties and the first transmission signal component circulating from the first transmission section output circuit are used by the second party power amplifier. And the intermodulation distortion generated by the transmission signal of the party A and the transmission signal of the party B is reduced.

Further, in the mutual distortion reduction circuit of the wireless device, each of the first and second transmitting units detects the signal from the combiner, the coupler, and the coupler at a stage preceding the first and second power amplifiers. A phase shifter for shifting the phase of the signal and a variable attenuator for adjusting the level are provided.

Further, in an intermodulation distortion reduction circuit of a radio apparatus which combines a plurality of transmission signals output from a plurality of transmission units with an output combiner and outputs the signals from one antenna end, each of the plurality of transmission units has a power A power amplifier to amplify,
At the preceding stage, respectively, a combiner, a coupler, a phase shifter for phase-shifting a part of the transmission signal detected from the coupler, a variable attenuator for adjusting the level, and a phase combiner at the preceding stage of each power amplifier. A part of each of the plurality of shifted and level-adjusted transmission signals is input to the combiner, and is overlapped with a main transmission signal of each transmission unit and amplified by each power amplifier.

A phase shifter for shifting the phase of a signal detected from the coupler and a variable attenuator for level adjustment are provided before the power amplifier of each transmission unit in the order of a coupler and a combiner. And

[0013] Intermodulation distortion generated in the power amplifier can be reduced by inverting the phase of the same signal as the other transmission signal coming from the output terminal of the power amplifier and overlapping it with the input signal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, the present embodiment is an example in which two transmission units are provided, and each transmission signal is combined and output from one antenna 1.

The frequencies of the transmission signals in the two transmission units are f ₁ and f ₂ . The frequency f ₁ is output to the antenna 1 through the power amplifier 5, the isolator 3, and the combiner 2. Similarly, the frequency f ₂ is output to the antenna 1 through the power amplifier 6, the isolator 4, and the combiner 2.
As the power amplifiers 5 and 6, GaAs power FETs or the like are used, and a tuned high-frequency amplifier circuit is generally employed. The isolators 3 and 4 are irreversible two-aperture passive elements that transmit radio waves in only one direction and hardly transmit in the reverse direction. A circulator may be used, and a waveguide isolator or a coaxial isolator using ferrite, etc. Is used. As the combiner 2, a waveguide, a coaxial coupler, or simply a resistance coupler is used. The combiner 2 performs impedance matching and is supplied to the antenna 1.

Here, the frequencies f ₁ and f ₂ , as indicated by the dotted lines, enter the power amplifiers 5 and 6 of the other transmission units as the frequencies f ₁ ′ and f ₂ ′, respectively, and transmit their own transmission signals f ₁ and f ₂ . f ₂ and intermodulation distortion occurs. The intermodulation wave shown in FIG. 2 is generated for reference.

To solve this, the frequencies f ₁ , f ₂
Are transmitted to couplers 9 and 10 respectively.
, The phase is shifted by the phase shifter 11 and the phase shifter 12, and the level is adjusted by the variable attenuator 13 and the variable attenuator 14.
And the combiner 8, the other output power amplifiers 5, 6
To the input signal of Here, the couplers 9 and 10 have a function of extracting a part of a signal component without affecting a signal line, and a directional coupler, a capacitive coupling, an inductive coupling, a resistance coupling which extracts by a spatial coupling. Any of coupling and the like may be used.
Further, the phase shifters 11 and 12 are phase-delayed, so that a varicap and a capacitor are used to form a T-type or π-type circuit in an analog manner, or an inductor and a capacitor circuit are used in a digital manner. , The signals from the couplers 9 and 10 are stored in a shift register or FIFO,
The phase can be shifted by changing the read timing. Further, the variable attenuators 13 and 14 can be easily achieved by the amount of resistance attenuation, and a configuration is used in which the conduction resistance value of the FET or transistor can be varied by the voltage or current level to the gate or base. Furthermore, the combiners 7 and 8 simply use a combiner such as a resistor combiner, a combiner with an operational amplifier, a hybrid combiner of 3 dB loss, or a combiner with a strip line.

Thus, the frequency f₁Is Δf_TwoIs duplicated
And f_TwoIs Δf₁Are overlapped, respectively, power amplification
In units 5 and 6, power is amplified. Power amplifiers 5 and 6
The other transmission signal f_Two', F₁′ Is around the output terminal
Come in, f_Two′ Is Δf _TwoGives f₁′ Is Δf₁
, Resulting in f₁And f_Two', F
_TwoAnd f₁'The phase that occurs when two transmitted signals interfere with each other
Intermodulation distortion can be reduced.

Next, the operation of the present invention will be described with reference to FIGS.

A plurality of transmission signals are two in this embodiment.
In the case of the transmission signal, the frequency f
₁, F_TwoAnd For multiple transmission signals, the transmission frequency
f₁To f_nAnd input to the synthesizer. Frequency f₁Is
As shown by the dotted line in the figure, the combiner 2 and other
Pass through the isolator 4 (to be exact,
The frequency f)₁′ As power of other transmitter
The signal is input to the output terminal of the amplifier 6. Similarly, the frequency f_Two
Is the frequency f from the output terminal of the other power amplifier 5._TwoAs'
Embed. Each of the power amplifiers 5 and 6 has a nonlinear characteristic.
Have other signals (other than your own)
Frequency) is input, the frequency component
The generated intermodulation distortion occurs. Basically, the frequency
Component f ₁'And f_Two′ Is the frequency f₁, F_TwoAnd that
Frequency components of the intermodulation distortion
Is basically 2f, as shown in FIG.₁−f_Two, And 2f
_Two−f₁And other fourth, fifth and so on. here
Therefore, the third-order distortion component generated in the band becomes the most problematic. Immediately
In the transmission characteristics, except for the third-order distortion intermodulation frequency, use
It is less likely to occur outside the band and cause interference.

In the power amplifier 5, intermodulation distortion occurs due to the frequencies f ₁ and f ₂ ′, and in the power amplifier 6 due to the frequencies f ₂ and f ₁ ′.

To solve this, the input signal f ₁ of the power amplifier 5 is shifted by 180 ° from the phase of the frequency f _2.
By overlapping f ₂ , the frequency f ₂ ′ wrapping around from the output end can be canceled or reduced, and the occurrence of intermodulation distortion can be suppressed. At this time, the phase shift is performed by the phase shifter 12 and the level adjustment is performed by the variable attenuator 14.
Done by

The same applies to the power amplifier 6, Δf
_The signal f ₁ ′ wrapped around by _one signal can be canceled or reduced, and the occurrence of intermodulation distortion can be suppressed. In this way, instead of applying feedback only at the output section where intermodulation distortion occurs and reducing it, a coupler is provided at the input section of the power amplifier and feedback is applied to reduce the generated intermodulation waves. There is an effect that the signal level is small and the configuration is simplified.

[Second Embodiment] In order to solve the above-mentioned disadvantages of the prior art, in the present embodiment, the same signal as the circulating signal, that is, a signal whose phase is shifted by 180 ° is added to the input, and the distortion is added in advance. By doing so, they cancel each other, and consequently reduce spurious components output from the antenna. FIG. 3 shows an embodiment of the present invention. This is a case where there are two circuits of the transmission unit. FIG.
, The components of the frequencies f ₁ and f ₂ output from the frequency converter (not shown) are partially extracted by the couplers 29 and 30, and the main signal components are
₁ and the frequency f _2, f ₁ corresponding to each other and components of f ₂ were synthesized, and power amplified by the power amplifier 25 and 26, to prevent the intrusion from the output side isolator 23 and 24, the synthesizer 2
The signals are combined at 2 and converted to radio waves by the antenna 21 and output. Also, some components extracted by the couplers 29 and 30 are converted into components that are phase-shifted by the phase shifters 31 and 32 and supplied to the combiners 27 and 28. Then, for example, a coupler is provided between the combiner 22 and the antenna, and the output of the coupler is observed with a spectrum analyzer for the frequency and the level of the signal component.
Other than the frequency f ₁ and f ₂ components shown in, so as to particularly reduce the levels of intermodulation wave, phase shifters 31 and 32
Is adjusted by displacing the phase.

Transmission signal f₁And f_TwoIs to convert each circuit
And is output from the antenna 21. Place
Is an isolator between the isolators 23 and 24 and the combiner 22.
The transmission is about 15dB and 20d at most.
f₁And f_TwoIs about -35 dB in total.
The -35 dB signal of each transmission signal leaks to the other.
And third-order distortion occurs in power amplifiers (PA) 25 and 26
I do. The third-order distortion component, as shown in FIG.₁, F
_Two, And coming into the band as 2
f_Two−f₁And 2f₁−f_TwoAnd the out-of-band fourth-order component 3
f_Two−f₁And 3f ₁−f_TwoIs not a problem. this
Input to PAs 25 and 26 in advance to prevent
Input the same signal and shift the phase by 180 °
Signal from the output side of PA25, 26
Signal can be canceled and the third-order distortion component can be suppressed.
You.

As a result, the spurious characteristics can be improved, so that the performance as an apparatus is enhanced. In addition, it is not necessary to make the isolation standards of the isolators 23, 24 and the combiner 22 strict, and the cost can be reduced. .

[Third Embodiment] In this embodiment, a case where a plurality of transmission signals are combined and a plurality of frequency components are transmitted from an antenna will be described. 5, the frequency of the transmission signal in three transmission portions f _1, f _2, and f ₃
And The frequency f ₁ is output to the antenna 41 through the power amplifier 46, the isolator 43, and the combiner 42. Similarly, the frequency f ₂ is output to the antenna 41 through the power amplifier 47, the isolator 44, and the combiner 42. Furthermore, the frequency f ₃ is output to the antenna 41 through the power amplifier 48 and the isolator 45 and combiner 42. The power amplifiers 46 to 48 are GaAs power FEs.
T or the like is used, and a tuning type high frequency amplifier circuit is generally employed. The isolators 43 to 45 are irreversible two-aperture passive elements that transmit radio waves only in one direction and hardly transmit in the reverse direction. A circulator may be used, and are arranged to prevent other transmission frequencies from wrapping around. Is done. But,
It is extremely difficult to make this wrap around zero. The combiner 42 uses a strip line or the like as a hybrid combiner, performs impedance matching, and supplies the antenna 41 to the antenna 41. The output of the antenna 41 differs between the mobile phone system and the PHS system, and the output power of the power amplifier may be several W to several hundred W in consideration of antenna efficiency and the like.

Here, the frequency f₁, F_Two, And f_ThreeIs
Same frequency f₁'And f_Two', F_Three’
The signal goes to the power amplifiers 46 to 48, and the own transmission signal f₁, F
_Two, F _ThreeCauses intermodulation distortion.

To solve this, the frequencies f ₁ ,
The transmission signals of f ₂ and f ₃ are respectively coupled to couplers 52 to
54, the phase is shifted by the phase shifters 55 to 57, the level is adjusted by the variable attenuators 58 to 60, and the level is adjusted by the hybrid synthesizers 49 to 51.
It overlaps with the input signals of the other transmitter output power amplifiers 46-48. Here, the couplers 52 to 54 have a function of extracting a part of the signal component without affecting the signal line, and a directional coupler, a capacitive coupling, an inductive coupling, and a resistance which are extracted by spatial coupling. Bonding or the like can be used. The combiners 49 to 51 use a combining means such as a resistor combiner, a combiner using an operational amplifier, a hybrid combiner, or a combiner using a strip line.

In the present embodiment, an example of three transmitting units has been described. However, even when transmitting a plurality of transmission frequencies in a base station such as a portable telephone transmitting two or more transmission frequencies, a similar configuration is employed. Intermodulation distortion can be reduced.

[0031]

According to the present invention, it is possible to cancel or reduce a transmission signal wrapping around from another transmission unit, so that it is possible to suppress the occurrence of intermodulation distortion and reduce the deterioration of radio characteristics. Can be.

Further, since the ratio depending on the characteristics of components such as a synthesizer and an isolator is greatly reduced, the standard of the characteristics of the components can be relaxed, so that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram according to an embodiment of the present invention.

FIG. 2 is an example of intermodulation distortion (third-order distortion occurs in the vicinity) explaining the present invention.

FIG. 3 is a configuration block diagram according to an embodiment of the present invention.

FIG. 4 is an example of intermodulation distortion (third-order distortion occurs in the vicinity) for explaining the present invention.

FIG. 5 is a configuration block diagram according to an embodiment of the present invention.

FIG. 6 is a configuration block diagram of a conventional wireless transceiver.

[Explanation of symbols]

 1,21 antenna 2,22 combiner 3,4,23,24 isolator 5,6,25,26 power amplifier 7,7,27,28 combiner 9,10,29,30 coupler 11,12,31,32 Phase shifter 13,14 Variable attenuator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/02-1/04 H04B 1/38-1/58 H04B 1/10-1/14 H04B 15 / 00-15/06 H04B 7/02-7/12

Claims (4)

(57) [Claims] 1. A wireless device that combines two transmission signals output from two transmission units, A and B, and outputs the combined signal from one antenna end, wherein a coupler is provided before a power amplifier of the A transmission unit. Having a phase shifter and a variable attenuator for adjusting the level of a part of the transmission signal detected from the coupler, and a power combiner in the previous stage of the power amplifier of the power transmission unit, An intermodulation distortion reduction circuit for a wireless device, characterized in that a part of the transmission signal having been subjected to the phase shift and the level adjustment is input to the second synthesizer, and is overlapped with the second transmission signal and amplified by the second power amplifier. 2. An instep power amplifier which cancels out the instep transmission signal component circulating from the output combiner for synthesizing the step A and step B transmission signals and the step S transmission unit output circuit,
2. The intermodulation distortion reduction circuit for a wireless device according to claim 1, wherein intermodulation distortion generated by the first and second party transmission signals is reduced. 3. The intermodulation distortion reduction circuit of a wireless device according to claim 1, wherein said combiner in a stage preceding said power supply amplifier and said power supply amplifier in each of said first and second transmission units. A mutual distortion reduction circuit for a wireless device, comprising: a coupler; and a phase shifter for phase-shifting a signal detected from the coupler and a variable attenuator for level adjustment. 4. A wireless device that combines a plurality of transmission signals output from a plurality of transmission units with an output combiner and outputs the signals from one antenna end, wherein the plurality of transmission units each include a power amplifier that amplifies power, At the preceding stage, respectively, a combiner, a coupler, a phase shifter for phase-shifting a part of the transmission signal detected from the coupler, a variable attenuator for adjusting the level, and a phase combiner at the preceding stage of each power amplifier. A part of each of the plurality of shifted and level-adjusted transmission signals is input to the combiner, and is overlapped with a main transmission signal of each transmission unit and amplified by each power amplifier. Reduction circuit.