JPH07193443A - High frequency circuit - Google Patents

Abstract

PURPOSE:To obtain a high frequency circuit such as a high frequency amplifier circuit and a high frequency mixer circuit of low distortion at the time of low voltage operation. CONSTITUTION:Side bandpass filters 102, 104, 101, and 104 where the center bandpass filter 103 of a center frequency fo and the center frequency increases and decreases by n times, (N+1) times,..., as many as an inter-channel frequency for fo are arranged on an input terminal 100. The output of each bandpass filter 101 to 105 is finally added to one output by a multistage mixer where a power distributor, a power mixing device and a phase device are combined. At the time, inter-modulation distortion of nth order, (n+1)th order,... is eliminated, adjusting phases. Also at the time of a low voltage operation, inter- modulation distortion over plural orders can be simultaneously suppressed without suppressing necessary signals. In particular, a high frequency signal amplifier and a high frequency mixer having low distortion characteristic can be composed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency circuit having active elements such as an amplifier and a mixer used in digital microwave communication, and more particularly to a measure for eliminating intermodulation distortion.

[0002]

2. Description of the Related Art Conventionally, a negative feedback system or a predistortion system has been used to suppress the occurrence of intermodulation distortion or the like that occurs in a high frequency circuit and realize a low distortion high frequency circuit. The negative feedback method is a method for constructing a low distortion high frequency circuit by lowering the input impedance or the gain. On the other hand, as shown in FIG. 7, the predistortion type high frequency circuit includes a predistortion circuit 500 connected to the high frequency input terminal 100 and an amplifier 110 connected to the output side of the predistortion circuit 500.
And an output terminal 190. That is,
The predistortion circuit 500 pre-creates a distortion opposite to the distortion generated by the amplifier 110, and the amplifier 11
This is a method for constructing a high-frequency circuit with low distortion by injecting it into an input signal of 0 and canceling the distortion.

[0003]

However, when the negative feedback method is adopted, the distortion component is suppressed, but the necessary signal component is also suppressed together with the distortion component, so that the required signal is suppressed during low voltage operation. The gain will decrease.
Further, in the negative feedback method, when the power supply voltage is low, the third-order intermodulation distortion is not sufficiently improved even if a large amount of current is passed.

On the other hand, in the predistortion system, the non-linearity of the predistortion circuit 500 is due to the amplifier 11
It is a condition for realizing good distortion suppression that the two nonlinearities are well matched so that the nonlinearity of 0 cancels out the inverse nonlinearity. However, in practice, it is difficult to make the predistortion circuit 500 having an inverse nonlinearity that accurately corresponds to the nonlinearity of the amplifier 110. Further, in addition to the necessary reverse distortion, another distortion generated by the predistortion circuit 500 may be input to the amplifier 110, and there is a fear that the distortion suppression as a whole may not be sufficiently realized. This becomes remarkable as the voltage becomes lower. In addition, it is quite difficult to simultaneously suppress intermodulation distortion over a plurality of orders.

As described above, the conventional technique has a problem that the third-order intermodulation distortion and the intermodulation distortion extending over a plurality of orders cannot be sufficiently suppressed, especially at a low voltage.

The present invention has been made in view of the above problems, and an object thereof is to provide a high frequency input with an integral multiple of the inter-channel frequency with respect to the center frequency of the center band pass filter and the center band pass filter. By arranging a demultiplexer composed of one or more pairs of side bandpass filters having increasing and decreasing center frequencies, and providing a means for synthesizing the outputs from each bandpass filter while adjusting the phase, An object of the present invention is to provide a low-distortion high-frequency circuit capable of effectively removing intermodulation distortion such as third-order intermodulation distortion even in a low voltage state.

[0007]

Means for Solving the Problems To achieve the above object, the means of the present invention as set forth in claim 1 is, as shown in FIG. 1, an input section for receiving a high frequency signal and an output of the input section as a high frequency circuit. A central bandpass filter connected to the side and having a predetermined center frequency as a median value, and a center frequency that increases or decreases by n times the inter-channel frequency (n is a positive integer) with respect to the median value. A demultiplexer composed of a pair of lateral bandpass filters, and three active filters that are connected to the output side of each bandpass filter of the demultiplexer and that actively act on the output signal of each bandpass filter. Element, three phase shifters connected to the output side of each active element, and a power combiner connected to the output side of each phase shifter to combine the output of each phase shifter to generate one signal And output from the above power combiner It is obtained by a configuration in which an output section for outputting a signal to the outside.

The means taken by the invention of claim 2 is the invention of claim 1 in which n is 3.

According to a third aspect of the present invention, as shown in FIG. 4, a high frequency circuit is connected to an input section for receiving a high frequency signal and an output side of the input section, and a predetermined center serving as a median value. A center bandpass filter having a frequency and a plurality of pairs of sideways having a center frequency that increases or decreases by n times (n is a positive integer), (n + 1) times, ... A demultiplexer consisting of a bandpass filter and the same number as the number of the bandpass filters connected to the output side of each bandpass filter of the demultiplexer and actively acting on the output signal of each bandpass filter. Connected to the output side of each active element and the plurality of power distributors, phase shifters, and power combiners in multiple stages, and output signals of the active elements are gradually combined to output one signal. A multistage combining unit configured, in which a configuration in which an output section for outputting a signal outputted from the multistage combining unit to the outside.

According to a fourth aspect of the present invention, in the above-mentioned third aspect of the present invention, the lateral bandpass filter is provided.
The pair of side bandpass filters are arranged so that each pair of lateral bandpass filters has a center frequency that differs from the center frequency of the center bandpass filter by three and four times the interchannel frequency.

According to a fifth aspect of the present invention, in the above first, second, third or fourth aspect of the present invention, the center frequency and passband attenuation of each bandpass filter and the phase amount of each phaser are set. It is provided with a microprocessor for controlling.

According to a sixth aspect of the present invention, in the above first, second, third, fourth or fifth aspect of the invention, the active element is an amplifier.

According to a seventh aspect of the present invention, in the invention of the first, second, third, fourth or fifth aspect, the active element is constituted by a mixer.

[0014]

With the above construction, in the first aspect of the invention, the phases of the outputs from the respective bandpass filters are appropriately adjusted by the respective phase shifters and are combined by the power combiner. In that case, even when operating at a low voltage, the necessary signal is not suppressed, and only the nth-order intermodulation distortion can be suppressed.

According to the second aspect of the invention, third-order intermodulation distortion, which is a problem particularly in a high frequency circuit, is eliminated.

In the invention of claim 3, the nth order, (n + 1)
It is possible to simultaneously suppress intermodulation distortion over multiple orders and ...

According to the fourth aspect of the invention, it is possible to remove the third-order intermodulation distortion and the fourth-order modulation distortion, which are especially problematic in a high frequency circuit.

According to the fifth aspect of the invention, the center frequency of each bandpass filter, the amount of attenuation in the pass band, and the amount of phase of each phaser are controlled by the microprocessor, so that a high-frequency wave with low distortion for an arbitrary reception frequency is obtained. It becomes possible to configure a circuit.

According to the sixth aspect of the invention, the intermodulation distortion generated when the high frequency signal is amplified by the amplifier is removed.

According to the seventh aspect of the invention, the intermodulation distortion generated when the high frequency signal is mixed by the mixer is removed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 First, Example 1 will be described. FIG. 1 shows the configuration of a high frequency amplifier circuit according to the first embodiment. As shown in the figure, the high frequency amplifier circuit includes an input terminal 10 as an input section for receiving a high frequency signal.
0 and an output terminal 1 as an output section for outputting a signal to the outside
90, a demultiplexer including three bandpass filters 101 to 103 connected in parallel to the input terminal, and an active element connected to the output side of each bandpass filter 101 to 103, respectively. Amplifiers 111 to 1
13, the phase shifters 121 to 123 connected to the output sides of the amplifiers 111 to 113, and the phase shifters 10 respectively.
A power combiner 180 that combines the outputs of 1 to 103 is provided. Here, each of the bandpass filters 101 to 103 of the demultiplexer has a predetermined center frequency f as a median value.
A central bandpass filter 102 having o and center frequencies fo '(fo -3 × Δf) and fo ″ (fo + 3 ×).
Δf) a pair of lateral bandpass filters 101,1
03 (where Δf is the inter-channel frequency).
That is, the pair of lateral bandpass filters 101, 1
03 denotes the inter-channel frequency Δf with respect to the center frequency (median value) fo of the center band-pass filter 102.
It has center frequencies fo ′ and fo ″ that are increased or decreased by three times.

Next, the operation of the high-frequency signal amplifier configured as above will be described with reference to FIGS. FIG. 2 shows frequency characteristics of gain including a bandpass filter per amplifier, in which 300 is an amplifier 1.
A frequency characteristic of gain including a band-pass filter per unit, 301 is a multichannel input signal spectrum of equal frequency intervals input to the amplifier. Further, in FIG. 3, as described above, the center bandpass filter 102 having the center frequency fo and the center frequency (median value) fo of the center bandpass filter 102 is 3 × Δf (Δf is an inter-channel frequency). Different center frequencies fo'and f
The total frequency characteristic is shown by the side bandpass filters 101 and 103 having o ″. That is, 300 is the frequency characteristic of the gain including the bandpass filter of the amplifier 112 connected to the central bandpass filter 102, 301,
Reference numeral 303 denotes the side bandpass filters 101, 1 respectively.
The frequency characteristics of the gain including the bandpass filters of the amplifiers 111 and 113 connected to the amplifier 03. Hereinafter, the frequency characteristics of the amplifiers include those including the frequency characteristics of the bandpass filter in the preceding stage of each amplifier.

When it is desired to receive a signal of frequency fo, (fo
−Δf) and (fo −2 × Δf), and further (fo + Δ
f) and the third-order intermodulation distortion frequency of the frequencies of (fo + 2 × Δf) coincide with fo. Here, the amplifier 11
If the pass band characteristics including the band pass filters 1 to 113 are the same, as shown in FIG. 3, the frequency value (fo −Δ
f) and each amplifier 111, 1 at (fo −2 × Δf)
The 12 gains are the same. In addition, the frequency value (fo + Δ
f) and each amplifier 112,1 at (fo + 2 × Δf)
The gain of 13 is also the same. Therefore, three amplifiers 111
When the phases of the outputs of the to 113 are appropriately adjusted by the phase shifters 121 to 123 and combined by the power combiner 180,
Unwanted third-order intermodulation distortion at the frequency fo can be removed. Moreover, the bandpass filter here needs only to have the same passband characteristics of the three amplifiers, and no special steepness is required.

The above is the case of suppressing the third-order intermodulation distortion. However, in the case of suppressing the nth-order intermodulation distortion, the center frequencies of the side bandpass filters 101 and 103 are set to the center bandpass filter. It suffices that the center frequency fo of 102 differs by n × Δf (Δf is a frequency between channels). Therefore, the invention of claim 1 is
The present invention is not limited to the above-mentioned first embodiment.

(Second Embodiment) Next, a second embodiment will be described. FIG. 4 shows the configuration of the high-frequency signal amplifier according to the second embodiment, in which five bandpass filters 101 to 105 are arranged for the input terminal 100. Here, in the second embodiment, each of the bandpass filters 101 to 1
The center frequency (fo −4) of the center bandpass filter 103 having the center frequency (median value) fo
× Δf) and (fo + 4 × Δf), the side bandpass filters 101 and 105, and the center frequency (fo), respectively.
The lateral bandpass filters 102 and 104 having −3 × Δf) and (fo + 3 × Δf) are arranged. That is, the side bandpass filters 102 and 104 are a pair of bandpass filters having a center frequency that is increased or decreased by n times the interchannel frequency Δf with respect to the center frequency (median value) fo of the center bandpass filter 103. The side bandpass filters 101 and 105 are a pair of bandpass filters having a center frequency that is different from the median value fo by (n + 1) times the interchannel frequency.

Further, in FIG. 4, the high frequency signal amplifier is provided with amplifiers 111 to 115 which are connected to the output sides of the band pass filters 101 to 105 and which are active elements for amplifying the output signals. At the same time, a multi-stage combining unit is provided on the output side of the amplifier.

The first stage of the multi-stage combining section is connected to a power distributor 121 which receives the outputs of the amplifiers 111 to 115 and distributes the power in two directions, and the output side of both ends thereof. Terminators 131a and 135b, and first-stage phase shifters 131b and 132a connected to the output side excluding both ends.
, 134b, 135a are provided. That is, in the first stage, the power distributors 121, 1 at both ends are
25 are respectively distributed to the terminators 131a and 135b and the first-stage phase shifters 131b and 135a, and each of the power splitters 122 to 124 excluding the ones at both ends respectively includes two first-stage phase shifters 132a and 132b to 134a. 134
It is designed to be distributed to each b. Further, in the second stage, two phase shifters 131b, 132a to 134 adjacent to each other among the phase shifters 131b to 135a in the first stage.
power combiner 14 for combining the outputs of b and 135a, respectively
1 to 144 and a phase shifter 151 connected to the output side of the power combiners 141 to 144 are arranged. And, in the third stage, two phase shifters 151 and 152, 153 and 15 which are adjacent to each other among the phase shifters 151 in the second stage.
Power combiners 161, 162 for combining the four outputs into one
And phase shifters 171 and 172 connected to the output sides of the power combiners 161 and 162. And
At the final stage, the two phase shifters 171 and 17 of the third stage are provided.
A power combiner 180 that combines the two outputs into one is provided.

That is, the multi-stage combiner is configured to combine a plurality of power dividers, phase shifters, and power combiners to gradually combine the output signals of the amplifiers 121 to 125 to output one signal. ing. However, the configuration of the multistage synthesizing unit according to claim 3 is not limited to this embodiment, and, for example, a configuration in which the power distributor is arranged in the second stage is also possible. In addition, the functions of the terminators 131a and 135b are correctly assigned to the power distributors 121 and 125, respectively.
The terminator may be replaced with another element, although it is intended to perform a distribution operation.

Next, the operation of this high frequency signal amplifier will be described. Similar to the operation principle of the circuit shown in FIG. 1 described above, the characteristics of the phase shifters 131b to 135a are appropriately adjusted, and the output signals are combined by the power combiners 141 to 144 to output the outputs of the power combiners 141 to 144. Phase the phase shifter 151 to 1
The output phases adjusted by 54 and combined by the power combiners 161 and 162 are adjusted again by the phase combiners 171 and 172 and combined by the power combiner 180 and output, that is, while adjusting the phase by each phaser. By finally combining the output signals into one output signal by the power combiner, the third-order intermodulation distortion and the fourth-order intermodulation distortion can be suppressed simultaneously. The third-order intermodulation distortion is suppressed by the power combiners 142 and 143, and the fourth-order intermodulation distortion generated by the amplifier 113 is suppressed by the amplifier 11.
1, 115, phase shifters 131b 135b, and power combiner 14
1-144, phase shifters 151-154, and power combiner 16
1, 162 are suppressed. The fourth-order intermodulation distortion generated in the amplifiers 112 and 114 is suppressed by the phase shifters 171 and 172 and the power combiner 180.

In the above description, third-order intermodulation distortion and 4
In the case of simultaneously suppressing the next intermodulation distortion, it is possible to suppress the intermodulation distortion over multiple orders at the same time by further increasing the number of parallel connections.
The invention of claim 3 is not limited to the second embodiment.

Further, by controlling the center frequency of each bandpass filter, the amount of attenuation in the pass band, and the amount of phase of the phase shifter by the microprocessor, at any reception frequency,
Intermodulation distortion over a plurality of orders can be suppressed at the same time.

In each of the above-described embodiments, an example in which the present invention is applied to a high frequency signal amplifier including an amplifier as an active element of a high frequency circuit has been described, but the active element of the present invention is limited to such an embodiment. Even in the case where other active elements are arranged, the intermodulation distortion can be removed when the active action is applied to the high frequency signal to cause the intermodulation distortion.

For example, FIGS. 5 and 6 show modifications of the first and second embodiments (see FIGS. 1 and 4), respectively. In each drawing, the elements denoted by reference numerals 200 to 290 all correspond to the elements denoted by reference numerals 100 to 190 in FIGS. 1 and 4 above. However, in this modification, the amplifiers 111 to 111
Instead of 115, mixers 211 to 215 and an LO signal input terminal 219 are provided. Also in this case, the intermodulation distortion is removed by the same operation as described in each of the above embodiments.

[0035]

As described above, according to the first aspect of the present invention, as a high frequency circuit, a center bandpass filter having a center frequency that is a median value for an input section and an inter-channel for a median value are provided. A demultiplexer consisting of a pair of lateral bandpass filters having a center frequency increased and decreased by n times the frequency is connected, and three active elements and three phases are provided on the output side of each bandpass filter. Since the power supply, the power combiner, and the output section are arranged, only the nth-order intermodulation distortion can be suppressed without suppressing a necessary signal even at the time of low voltage operation.

According to the invention of claim 2, in the invention of claim 1, the difference between the center frequencies of the center-side bandpass filters is set to be three times the inter-channel frequency, which is a problem particularly in a high frequency circuit. Third-order intermodulation distortion can be effectively removed.

According to the third aspect of the present invention, as the high frequency circuit, the central bandpass filter having the central frequency which is the central value and the central value are n times, (n + 1) times the inter-channel frequency, and ... is provided with a demultiplexer composed of a plurality of pairs of side bandpass filters having a center frequency increased or decreased, and the output of this demultiplexer is connected to a power distributor, a power combiner, and a phaser. Since the multi-stage synthesizing unit connected in multiple stages finally synthesizes one output, it is possible to simultaneously suppress inter-modulation distortion over multiple orders such as nth order, (n + 1) th order ,.

According to the invention of claim 4, in the invention of claim 3, two pairs of side bandpass filters are arranged,
Since the frequency difference with respect to the median of the center frequencies of the side bandpass filters of each pair is set to be 3 times and 4 times the inter-channel frequency, respectively, the 3rd-order intermodulation distortion and the 4th-order modulation distortion, which are particularly problematic in the high frequency circuit, are generated. Can be suppressed at the same time.

According to the invention of claim 5, the upper claim 1,
In the second, third, or fourth invention, since the microprocessor controls the center frequency of the bandpass filter, the passband attenuation, and the phase amount of each phaser, it has a low distortion characteristic for any reception frequency. A high frequency circuit can be configured.

According to the invention of claim 6, the above-mentioned claim 1,
Since the active element in the invention of 2, 3, 4 or 5 is an amplifier, it is possible to effectively suppress intermodulation distortion that occurs when amplifying a high frequency signal.

According to the invention of claim 7, the above-mentioned claim 1,
Since the active element in the invention of 2, 3, 4 or 5 is a mixer, it is possible to effectively suppress the intermodulation distortion that occurs when mixing a high frequency signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a high frequency signal amplifier according to a first embodiment.

FIG. 2 is a frequency characteristic diagram of one amplifier including a bandpass filter in the first embodiment.

FIG. 3 is a frequency characteristic diagram of three amplifiers including a bandpass filter according to the first embodiment.

FIG. 4 is a block diagram showing a configuration of a high frequency signal amplifier circuit according to a second embodiment.

FIG. 5 is a block diagram showing a configuration of a high frequency signal mixing circuit according to a modification of the first embodiment.

FIG. 6 is a block diagram showing a configuration of a high frequency signal mixing circuit according to a modification of the second embodiment.

FIG. 7 is a block diagram showing a predistortion method which is a conventional example.

[Explanation of symbols]

 100 input terminal (input part) 101-105 bandpass filter 111-115 amplifier 121-125 power distributor 131a, 135b terminator 131b-135a phaser 141-144 power combiner 151-154 phaser 161,162 power combiner 171, 172 Phaser 180 Power combiner 190 Output terminal (output section)

Claims (7)

[Claims] 1. An input unit for receiving a high frequency signal, a center bandpass filter connected to the output side of the input unit and having a predetermined center frequency as a median value, and n times the inter-channel frequency with respect to the median value. (N is a positive integer) A demultiplexer composed of a pair of side bandpass filters each having a center frequency that increases or decreases, and is connected to the output side of each bandpass filter of the demultiplexer. Three active elements that perform an active action on the output signal of the bandpass filter, three phase shifters connected to the output side of each active element, and connected to the output side of each phase shifter, A high-frequency circuit comprising: a power combiner that combines the outputs of the respective phase shifters to generate one signal; and an output unit that outputs the signal output from the power combiner to the outside. 2. The high frequency circuit according to claim 1, wherein n is 3. 3. An input section for receiving a high frequency signal, a central bandpass filter connected to the output side of the input section and having a predetermined center frequency as a median value, and n times the inter-channel frequency with respect to the median value. (N is a positive integer),
(N + 1) times, ... A demultiplexer composed of a plurality of pairs of lateral bandpass filters having center frequencies that increase and decrease respectively, and connected to the output side of each bandpass filter of the demultiplexer, The same number of active elements as the number of the band pass filters that actively act on the output signal of the pass filter, and a plurality of power dividers, phase shifters, and power combiners connected to the output side of each active element are provided. A multi-stage combining unit configured to be combined in multiple stages and gradually combine output signals of active elements to output one signal, and an output unit for outputting the signal output from the multi-stage combining unit to the outside A high-frequency circuit characterized by that. 4. The high frequency circuit according to claim 3, wherein two pairs of the lateral bandpass filters are arranged, and the lateral bandpass filters of each pair are between channels with respect to a center frequency of the central bandpass filter. A high frequency circuit having center frequencies that differ by three and four times the frequency. 5. The high frequency circuit according to claim 1, 2, 3 or 4, further comprising a microprocessor for controlling a center frequency and a passband attenuation amount of each bandpass filter and a phase amount of each phase shifter. A high-frequency circuit characterized by that. 6. The high frequency circuit according to claim 1, 2, 3, 4 or 5, wherein the active element is an amplifier. 7. The high frequency circuit according to claim 1, 2, 3, 4 or 5, wherein the active element is a mixer.