JPH11317605A - Attenuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an attenuator which reduces insertion loss and signal distortion with low poser consumption. SOLUTION: This attenuator is provided with a transmission line 2, that transmits a microwave signal, a PIN diode 6 which is connected at a place that is separated inwardly from input and output ends of the transmission line respectively by a 1/4 wavelength in a shunt shape, a drive means which applies voltage to the diode 6 and a ground terminal, which grounds the microwave signal output end of the diode 6 via a capacitor 8. A signal inputted to the transmission line can be continuously attenuated because the microwave resistance value of the microwave variable resistance element (PIN diode) 6 can be controlled continuously by continuously controlling the voltage applied to the element 6 from the drive means. Also, it is possible to reduce both the insertion loss and signal distortion at the time of minimum attenuation, since the element 6 is connected to the signal transmission line in a shunt form and is not serially inserted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency variable attenuator suitable for mobile communication equipment such as portable telephones, measuring equipment, and other high-frequency and microwave band electric equipment, and more particularly to a microstrip line and the like. The present invention relates to an attenuator using a transmission line.

[0002]

2. Description of the Related Art Generally, attenuators are used in mobile communication devices such as mobile phones, measuring devices, and other high-frequency and microwave band electrical devices. One example of such conventional attenuators is a signal line. (Transmission line)
There is a π-type or T-type variable attenuator (hereinafter referred to as Conventional Example 1) in which a plurality of microwave variable resistance elements such as PIN diodes are inserted in series and shunt, respectively.

Further, as another conventional variable attenuator, a microwave variable resistance element is connected in series between an open stub end of 伝 送 or 波長 wavelength of a transmission signal branched from a signal line and a ground plane. (Hereinafter referred to as Conventional Example 2).

[0004]

However, in such a conventional example 1, since a microwave variable resistance element such as a PIN diode is inserted in series to the signal line, the insertion loss is large and the microwave variable resistance is increased. The signal distortion is large due to the non-linearity of the resistance element. Therefore, in order to reduce the insertion loss, it is necessary to increase the applied current or use a low-resistance element for high power, and thus there is a problem that the efficiency is low or the cost is high.

[0005] In the conventional example 2, the input / output matching deteriorates as the amount of attenuation increases. Further, when the stub is in the released state at the time of the minimum attenuation of the transmission signal, the insertion loss due to radiation loss increases. In the case of the short-circuit state, there is a problem similar to that of the above-described conventional example 1.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an attenuator capable of reducing insertion loss and signal distortion with low power consumption.

[0007]

According to a first aspect of the present invention, there is provided a transmission line for transmitting a microwave signal; and a shunt at a point apart from the input and output ends of the transmission line by １ ／ wavelength of the transmission signal. A microwave variable resistance element connected in a shape;
Driving means for applying a voltage to the microwave variable resistance element;
A ground terminal for grounding a microwave signal output terminal of the microwave variable resistance element via a capacitor.

The microwave variable resistance element is an element capable of controlling a resistance value to a high-frequency (microwave) signal by controlling an applied voltage (current).
There are N diodes, FETs (field effect transistors), and the like.

According to the present invention, by continuously controlling the voltage applied from the driving means to the microwave variable resistance element, the microwave resistance value of the microwave variable resistance element can be continuously controlled. Therefore, the signal input to the transmission line can be continuously attenuated.

Further, since the microwave variable resistance element is connected to the signal transmission line in a shunt form and is not inserted in series, both the insertion loss at the time of minimum attenuation and the signal distortion can be reduced.

That is, at the time of the minimum attenuation of the transmission signal, the microwave variable resistance element shunt-connected to the transmission line becomes non-conductive (cut off). (Eg, 50Ω or 75Ω) (eg, 1KΩ).
Above). At this time, the current consumption by the microwave variable resistance element is zero, and the microwave variable resistance element is disposed on the shunt side with respect to the transmission line, so that the signal distortion can be reduced to a very small level.

According to a second aspect of the present invention, there is provided a transmission line for transmitting a microwave signal; and a first shunt-shaped connection from an input terminal to an output terminal of the transmission line at a point separated by 1/4 wavelength of the transmission signal. A microwave variable resistance element; a second microwave variable resistance connected in a shunt form at a point separated from the connection point between the transmission line and the first microwave variable resistance element by 1/4 wavelength of the transmission signal. An element; driving means for applying a voltage to the first and second microwave variable resistance elements; and a ground terminal for grounding the microwave signal output terminals of the first and second microwave variable resistance elements via a capacitor. An attenuator characterized by having;

According to the present invention, the voltage applied to the microwave variable resistance element from the driving means is continuously controlled in the same manner as in the first aspect of the invention, so that the microwave resistance value of the microwave variable resistance element is changed. Since the control can be continuously performed, the signal input to the transmission line can be continuously attenuated.

Further, according to the present invention, the attenuation of the transmission signal can be controlled doubly by the first and second two microwave variable resistance elements. Can be increased.

Further, similarly to the first aspect of the invention, the attenuation of the transmission signal is controlled by the first and second microwave variable resistance elements connected in a shunt manner to the transmission line. As in the present invention, both the insertion loss and the signal distortion can be reduced. In addition, the microwave variable resistance element is 2
By providing the above, the attenuation of the transmission signal may be further increased.

According to a third aspect of the present invention, the microwave variable resistance element is a PIN diode.
Or the attenuator according to 2.

According to the present invention, since the microwave variable resistance element according to the first and second aspects of the present invention has relatively small nonlinearity with respect to the microwave signal, it is possible to reduce the signal distortion over the entire attenuation range.

According to a fourth aspect of the present invention, a coupling capacitor is inserted in series at each of the microwave signal input and output terminals of the transmission line, and a microwave variable resistance element is formed in a shunt form from a connection point through a resistor. The attenuator according to any one of claims 1 to 3, wherein the attenuator is connected.

According to the present invention, by setting the resistance value appropriately, good input / output matching can be obtained over the entire attenuation range.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A description will be given based on FIG. In these figures, the same or corresponding parts are denoted by the same reference characters.

FIG. 1 is an electronic circuit diagram of an attenuator 1 according to a first embodiment of the present invention, and FIG. 2 is an ideal equivalent circuit diagram of the attenuator. The attenuator 1 forms a transmission line 2 such as a microstrip line, a coaxial line, a coplanar line, or the like to have a length of a half wavelength (λ / 2) of a microwave input signal RF to be transmitted by the transmission line 2. The input side IN end of the input signal RF and the output OU
A pair of left and right input and output coupling capacitors 3a and 3b are inserted in series at the T-side end.

The input and output terminals IN and OUT are connected to the anodes of the PIN diodes 4a and 4b, respectively, while the cathodes are grounded via the resistors 5a and 5b, respectively. The transmission line 2 has a total length of 1/4 wavelength (λ /
The cathode side of the PIN diode 6, which is a microwave variable resistance element, is connected at an equidistant location α when divided equally in 4). While driving means (not shown) is connected to the anode side of the PIN diode 6 via the control terminal 7,
It is grounded via a connected bypass capacitor 8. In FIG. 2, RL can be represented by the following equation (1).

[0023]

(Equation 1)

Next, the operation of the attenuator 1 will be described.

First, when controlling the amount of attenuation of the microwave signal RF input to the input terminal IN to a minimum, the PIN diode 6 is transmitted from the driving means (not shown) via the control terminal 7.
The DC control voltage applied to the anode of is set to zero. That is, no control voltage is applied to the control terminal 7.

Then, since the PIN diodes 4a, 4b and 6 are cut off (OFF), the connection points βa, βb and α of the PIN diodes 4a, 4b and 6 are opened. Therefore, the input signal RF is transmitted to the output terminal OUT through the transmission line 2 as it is. Therefore, the amount of attenuation of the input signal at this time is minimum.

The impedance when the PIN diodes 4a, 4b and 6 are shut off (OFF) is
Normal line impedance (eg, 50Ω or 75Ω).
Ω) (1 KΩ or more), and since the PIN diodes 4 a, 4 b, and 6 are disposed on the shunt side with respect to the transmission line 2, signal distortion can be extremely reduced.

On the other hand, when the attenuation of the microwave input signal RF is controlled to the maximum, the maximum control voltage allowed is applied to the anodes of the PIN diodes 4a, 4b and 6 from the driving means via the control terminal 7. At this time, the microwave resistance of the PIN diodes 4a, 4b and 6 is controlled to the minimum allowable value.

At this time, the microwave resistance of the PIN diode 6 becomes an extremely low value (for example, 5 Ω or less),
The connection point α of the N diode 6 is substantially grounded via the PIN diode 6 and the bypass capacitor 8. The impedance detected from the input and output terminals is 5
a or 5b plus a PIN diode 4a or 4b and a 1/4 wavelength short-circuit stub connected in parallel. However, when the latter is viewed from each connection point, it becomes almost open. The value is almost the former only.

When the control voltage applied to the PIN diode 6 is controlled continuously, the microwave resistance of the PIN diodes 4a, 4b and 6 can be controlled continuously from the maximum to the minimum. The amount of attenuation of the input signal RF can be continuously controlled from the minimum to the maximum according to the change.

At this time, the impedance viewed from the input and output terminals is maintained at a good value in the entire attenuation range.

FIG. 2 shows that the load impedance is equal to the transmission line specific impedance R ₀ and the PIN diode 4
If a, 4b and 6 are idealized with only resistance components,
FIG. 4 is an ideal equivalent circuit diagram of the impedance Z (R) when viewed from the input IN side of the attenuator 1, and the impedance Z (R) can be expressed by the following equation (2).

[0033]

(Equation 2)

Equation 2 can be derived by the following calculation. That is, in FIG. 2, generally pure resistance load R _L
If a transmission line having a length λg / 4 and a specific impedance R ₀ is connected in series, and the impedance seen from the input side is Z ₁ , this Z ₁ can be obtained by the following equation (3).

[0035]

(Equation 3)

When R is connected in parallel to the impedance Z ₁ , the impedance seen from the input side is Z ₂
Then, Z ₂ can be obtained by the following equation (4).

[0037]

(Equation 4)

Further, if a transmission line having a length λg / 4 and a specific impedance R ₀ is added in series, and the impedance seen from the input side is Z ₃ , this Z ₃ is given by the following equation (5). Can be obtained by

[0039]

(Equation 5)

When R + R ₀ is connected in parallel with this, and the impedance seen from the input side is Z (R), this Z (R) can be obtained by the above equation (2).

Thus, when Z (R) ≦ R ₀ , the reflection loss is maximized when Z (R) is minimized. The reflection loss can be obtained by the following equation (6).

[0042]

(Equation 6)

FIG. 3 is an electronic circuit diagram of an attenuator 1A according to a second embodiment of the present invention. This attenuator 1
A is a transmission line 2A such as a microstrip line, a coaxial line, or a coplanar line, and first and second PIN diodes 9, 1 as first and second microwave variable resistance elements.
The main feature is that the attenuation stage including 0 is added to one stage and formed into two stages.

That is, the transmission line 2A is formed to have a length three times as long as a quarter wavelength (λ / 4) of the microwave signal RF, and the transmission line 2A is formed to have a length of three times the quarter wavelength (λ / 4). The cathode side of the first PIN diode 9 is connected in parallel to the equally divided point on the input IN side when divided equally, and the cathode side of the second PIN diode 10 is connected in parallel to the equally divided point on the output OUT side. ing.

The anode side of the first PIN diode 9 is grounded via a bypass capacitor 11, and the first P
Anode of IN diode 9 and bypass capacitor 11
Is connected to the anode side of the second PIN diode 10 by a connection line 12, and this connection point is connected to the control terminal 13
, And a control voltage Vc is equally applied to the anodes of the first and second PIN diodes 9 and 10 from a driving means (not shown) connected to the control terminal 13.

Accordingly, when the control voltage applied from the driving means to the control terminal 13 is set to zero (no application), the first and second PIN diodes 9 and 10 and the PIN of the input / output section are set.
Since the resistance of the diodes 4a and 4b to the microwave is maximized, the input signal RF is substantially unchanged from the transmission line 2.
A is output to the output terminal OUT through A. Therefore,
At this time, the amount of attenuation of the input signal RF is minimum.

On the other hand, the control voltage Vc applied from the driving means to the control terminal 13 is equal to the first and second PIN diodes 9,
When the applied voltage reaches a predetermined maximum value, both the first and second PIN diodes 9 and 10 and the PIN diode 4 of the input / output section are applied.
The microwave resistance values of a and 4b become the minimum values.

Then, the input and output terminals IN of the transmission line 2A,
Since each position of １ ／ wavelength (λ / 4) from OUT is almost grounded via the first and second PIN diodes 9 and 10 and the bypass capacitor 11,
The input signal RF input to the input terminal 1N is grounded and attenuated in two stages through the first and second PIN diodes 9, 10. Therefore, while the attenuator 1 shown in FIG. 1 attenuates the input signal RF in one stage by one diode 6, the attenuator 1A of this embodiment has two attenuators.
Since the input signal RF is attenuated in two stages by the diodes 9 and 10, the amount of attenuation can be increased.

As in the case of the attenuator 1, the impedance of the first and second PIN diodes 9, 10 and the PIN diodes 4a, 4b of the input / output section when they are non-conductive (interrupted) is equal to the normal line of the transmission line 2A. The impedance can be set extremely higher (for example, 1 KΩ) than the impedance (for example, 50Ω or 75Ω), and the PIN diodes 9 and 10 and the PIN diodes 4a and 4
Since 4b is disposed on the shunt side with respect to the transmission line 2A, signal distortion can be extremely reduced.

Further, by continuously controlling the control voltage Vc, the amount of attenuation of the input signal RF can be continuously controlled.

The input and output impedances of the attenuator 1A are the same as those of the attenuator 1 described above.
By appropriately selecting the values of the resistors 5a and 5b, matching is automatically performed over the entire attenuation range. The number of attenuation stages including the second PIN diode 10 may be increased to three or more.

FIG. 4 is an electronic circuit diagram of an attenuator 1B according to a third embodiment of the present invention. This attenuator 1
B denotes each PIN diode 4 of the attenuator 1 shown in FIG.
a, 4b, 6 are FETs (field effect transistors) 1
There is a main feature in that each of 4, 15, and 16 is replaced. The basic operation mode is almost the same as that of the attenuator 1 except that the characteristic of the applied control voltage versus the attenuation is different.

[0053]

As described above, according to the first aspect of the present invention, by continuously controlling the voltage applied from the driving means to the microwave resistance element, the microwave of the microwave variable resistance element is controlled. Since the wave resistance can be controlled continuously, the signal passing through the transmission line can be continuously attenuated.

Further, since the microwave variable resistance element is connected to the signal transmission line in a shunt form and is not inserted in series, both the insertion loss at the time of minimum attenuation and the signal distortion can be reduced.

That is, at the time of the minimum attenuation of the transmission signal, the microwave variable resistance element connected to the transmission line in a shunt state becomes non-conductive (cut off), and the equivalent resistance is the normal line impedance of the microwave transmission line. (Eg, 50Ω or 75Ω) (eg, 1KΩ).
Above) can be set. At this time, the current consumption by the microwave variable resistance element is zero, and the microwave variable resistance element is arranged on the shunt side with respect to the transmission line, so that the signal distortion can be reduced to an extremely small level.

Further, according to the second aspect of the present invention, the voltage applied to the microwave variable resistance element from the driving means is continuously controlled in the same manner as in the first aspect of the invention, so that the Since the microwave resistance value can be continuously controlled, the signal input to the transmission line can be continuously attenuated.

Furthermore, according to the present invention, the attenuation of the transmission signal can be controlled doubly by the first and second two microwave variable resistance elements. Can be increased.

Further, similarly to the first aspect of the present invention, the attenuation of the transmission signal is controlled by the first and second microwave variable resistance elements connected to the transmission line in a shunt manner. As in the present invention, both the insertion loss and the signal distortion can be reduced. In addition, the microwave variable resistance element is 2
By providing the above, the attenuation of the transmission signal may be further increased.

According to the third aspect of the present invention, the microwave variable resistance element of the first and second aspects of the present invention has a relatively small nonlinearity with respect to the microwave signal, so that the signal distortion can be reduced over the entire attenuation range. Can be.

According to the fourth aspect of the present invention, by setting the resistance value appropriately, good input / output matching can be obtained over the entire attenuation range.

[Brief description of the drawings]

FIG. 1 is an electronic circuit diagram of an attenuator according to a first embodiment of the present invention.

FIG. 2 is an ideal equivalent circuit diagram of the attenuator shown in FIG.

FIG. 3 is an electronic circuit diagram of an attenuator according to a second embodiment of the present invention.

FIG. 4 is an electronic circuit diagram of an attenuator according to a third embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B Attenuator 2, 2A Transmission line 3a, 3b Coupling capacitor 4a, 4b PIN diode 5a, 5b Input / output matching resistor 6 PIN diode 7 Control terminal 8 Bypass capacitor 9 First PIN diode 10 Second PIN Diodes 14, 15, 16 FET

Continued on the front page (72) Inventor Toshiya Suzuki 4-3-1 Higashishinagawa, Shinagawa-ku, Tokyo Toshiba Lighting & Technology Corporation

Claims (4)

[Claims] A transmission line for transmitting a microwave signal;
Each one of the transmission signals goes inward from the input and output ends of the transmission line.
A microwave variable resistance element connected in a shunt shape at a location separated by / 4 wavelength; driving means for applying a voltage to the microwave variable resistance element; and a microwave signal output terminal of the microwave variable resistance element via a capacitor. An attenuator comprising: a ground terminal for grounding; 2. A transmission line for transmitting a microwave signal;
A first microwave variable resistance element connected in a shunt manner at a position separated by １ ／ wavelength of a transmission signal from an input end to an output end of the transmission line; and a transmission line and the first microwave variable resistance element. A connection point; a second microwave variable resistance element connected in a shunt shape at a location separated by １ ／ wavelength of a transmission signal from the connection point; driving means for applying a voltage to the first and second microwave variable resistance elements An attenuator comprising: a ground terminal for grounding the microwave signal output terminals of the first and second microwave variable resistance elements via a capacitor. 3. The attenuator according to claim 1, wherein the microwave variable resistance element is a PIN diode. 4. A coupling capacitor is inserted in series at each of the microwave signal input and output terminals of the transmission line,
The attenuator according to any one of claims 1 to 3, wherein a microwave variable resistance element is connected in a shunt manner from the connection point via a resistor.