JPH11317606A - Pin diode switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type PIN diode switch that has high isolation. SOLUTION: First and second terminals T1 and T2 of a 3dB coupler 3 are connected via capacitors C1 and C2 between an input terminal 1 and an output terminal 2, 1st and 2nd matching circuits 7 and 8 are connected to 2nd and 3rd terminals T2 and T3 of the coupler 3 and PIN diodes D1 and D2 are connected to them. The diodes D1 and D2 are provided with bias circuits 4 and 5 respectively, they are connected to a bias voltage feeding terminal 6 and a bias voltage is fed. The lengths of the circuits 7 and 8 are selected, so that the phase of a high frequency leak component from the terminal T1 of the coupler 3 to the terminal T4 can be opposite to the phase of a reflection component of a high frequency signal, which is reflected from the PIN diode and is outputted to the terminal T4 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a PIN diode switch, and more particularly to a reflection type PIN diode switch.

[0002]

2. Description of the Related Art A PIN diode has a property that a high frequency resistance changes from a low resistance (0Ω) to a high resistance (several kΩ) by changing a flowing current by applying a bias. Or it is used to construct an attenuator.

FIG. 5 is a circuit diagram showing a basic form of a switch using a PIN diode. There are two types of switches using a PIN diode, one called a series connection type and one called a parallel connection type. The switch shown in FIG. 5A is called a series connection type, and the input terminal 4
A plurality of PIN diodes 43 between
Are connected in series to form a switch circuit.

In this circuit, an input terminal 41 and an output terminal 4
When no DC bias is applied between the first and second
Since the intrinsic semiconductor layer (i-layer) of the N diode 43 has a high resistance, it is difficult for a current to flow between the input terminal 41 and the output terminal 42, and the N diode 43 functions as a signal-off switch. When a direct current bias is applied between the input terminal 41 and the output terminal 42 in the forward direction, the intrinsic semiconductor layer (i-layer) of the PIN diode 43 has a low resistance. Current flows easily, and acts as a signal-on switch.

However, in this circuit, the input terminal 41 is short-circuited when functioning as a signal-off switch,
When used at high frequencies, there is a moment when the potential becomes extremely high because impedance mismatching occurs and reflection occurs in the signal, and there is a coupling between the input terminal 41 and the output terminal 42 by jumping over the PIN diode 43 and having sufficient coupling. There is a problem that isolation cannot be obtained.

On the other hand, the switch shown in FIG. 5B is called a parallel connection type, and a plurality of PIN diodes 44 are connected in parallel between an input terminal 41 and an output terminal 42 to constitute a switch circuit.

In this circuit, when a negative voltage is applied to the input terminal 41 and a direct current bias is applied in the forward direction, the intrinsic semiconductor layer of the PIN diode 44 is turned on because all the intrinsic semiconductor layers have low resistance, and the PIN diode 44 serves as a short-circuit element. Working, this circuit acts as a signal off switch.

On the other hand, when no DC bias is applied between the input terminal 41 and the output terminal 42, the PIN diode 44 has a high resistance, works as an open element, and a current flows between the input terminal 41 and the output terminal 42. , Works as a signal-on switch.

However, also in this circuit, when the input terminal 41 functions as a switch for turning off the signal, the input terminal 41 is short-circuited.
There is a problem that a signal jumps and is transmitted between the four and sufficient isolation cannot be obtained.

FIG. 6 is a circuit diagram of a first example of a conventional switch using a PIN diode. This is disclosed in
FIG. 5 is a circuit disclosed in US Pat.
This is an improvement of the isolation of the series switch shown in FIG. This circuit includes a plurality of Ps connected in series.
PIN diodes 52 and 53 are provided between the input terminal 41 and the output terminal 42 of the IN diode 43 and the ground 45, respectively.
And the termination resistance 54 and the capacitance 57, and further, the connection points 50, 5 and 5 of the termination resistance 54 and the capacitance 57.
1 are connected by an inductance 58 to separate the connection points 50 and 51 in terms of high frequency.

In this circuit, when a DC bias for turning on the PIN diodes 52 and 53 is applied between the input terminal 41 and the output terminal 42, the PIN diode 43 is turned off and the PIN diodes 52 and 53 become low resistance. Therefore, this circuit works as a signal-off switch. Further, since the input terminal 41 is in a state of impedance matching, the potential of the input terminal 41 or the output terminal 42 becomes constant.

As a result, coupling over the PIN diode 43 is eliminated, and the isolation can be improved. Conversely, when a DC bias that turns off the PIN diodes 52 and 53 is applied between the input terminal 41 and the output terminal 42, the PIN diode 4
3 turns on and acts as a signal on switch.

However, in this circuit, the inductance 5
Since the connection points 50 and 51 are separated at a high frequency at 8, the isolation depends on the frequency, and the lower the frequency, the lower the isolation.

FIG. 7 is a circuit diagram showing a first basic form of an attenuator using a PIN diode. A PIN diode 63 is connected between the input terminal 61 and the output terminal 62,
Capacitors C12 and C13 on both sides of the IN diode 63
Connect. The capacitors C12 and C13 are for blocking direct current. A resistor R1 is connected to both sides of the PIN diode 63.
2 and R13, and the terminal Ib of the resistor R15 is connected to the PIN.
A bias current flows through the diode 63 to the ground.

In this circuit, the amount of attenuation of the high-frequency signal input from the input terminal 61 is determined by the impedance of the PIN diode 63. Also, the PIN diode 63
Since the impedance becomes small when the bias current is large and becomes large when the bias current is small, a variable attenuator whose attenuation can be changed by changing the bias current is obtained.

However, in this circuit, when the impedance increases, the input impedance of the input terminal 61 becomes different from the load impedance, so that matching cannot be achieved, and there is a problem that the phase characteristics are deteriorated.

FIG. 8 is a circuit diagram of a first example of an attenuator using a conventional PIN diode. This is a circuit disclosed in Japanese Unexamined Patent Publication No. 61-274507, in which the attenuator shown in FIG. 7 has improved matching and phase characteristics. In this circuit, the input side of the resistor R12 and the resistor R
13 are provided at the output side with amplifiers 64 and 65, respectively.
Since the matching is achieved, the phase characteristics are improved.

FIG. 9 is a circuit diagram showing a second basic form of an attenuator using a PIN diode. This attenuator is configured by connecting a PIN diode 85 in parallel to a transmission line having a characteristic impedance of 50Ω constituted by distributed constant lines 81 to 84. In this attenuator, P
When a forward bias is applied to the IN diode 85 to energize it, as shown in FIG.
Acts as a resistance of several ohms and the signal is reflected. At the time of reverse bias, as shown in FIG. 9 (c), the PIN diode 85 functions as a capacitor, and the signal passes only by loss due to mismatch. However, this attenuator has a problem that the isolation cannot be improved without changing the characteristic impedance because the isolation is determined by the characteristic impedance.

FIG. 10 is a circuit diagram of a second example of a conventional attenuator using a PIN diode. This is disclosed in
-49412 discloses a circuit in which the isolation is improved without changing the characteristic impedance of the attenuator shown in FIG.

In this attenuator, the PI of the attenuator shown in FIG.
Matching circuits 86 to 89 having a length of 波長 wavelength and an impedance of 61Ω are provided on the transmission lines on the input side and output side of the N diode 85, respectively.

With this configuration, the impedance seen from the input side and the output side from the PIN diode 85 becomes 75Ω due to the impedance transformation action, and the impedance seen from the input side and the output side outside the matching circuits 86 to 89 becomes 50Ω.
It remains at Ω. As described above, by increasing the impedance when the input side and the output side are viewed from the PIN diode 85, the isolation can be improved. However, the insertion loss increases slightly.

FIG. 11 is a circuit diagram of a second example of a conventional switch using a PIN diode. This switch is called a reflection PIN diode switch, and is devised as an ideal switch (attenuator) in which the maximum attenuation becomes infinite when there is no reflected wave at an arbitrary bias value.

This circuit uses a coupler generally called a duplexer coupler or a hybrid coupler. Here, a case where a 3 dB coupler is used as a duplexer coupler will be described.

This circuit comprises an input terminal 1, a 3 dB coupler 3 to which a first terminal (input terminal) T1 is connected to the input terminal 1 via a first capacitor C1,
A first PIN diode D1 connected to a second terminal (coupling terminal) T2 of the coupler 3, a second PIN diode D2 connected to a third terminal (output terminal) T3 of the 3dB coupler 3, and a fourth terminal of the 3dB coupler 3 (Output terminal) T
4 includes an output terminal 2 connected via a second capacitor C2, and bias circuits 4 and 5 provided in the first and second PIN diodes D1 and D2, respectively.

Here, each of the bias circuits 4 and 5 includes inductances L1 and L2, resistors R1 and R2, and capacitors C3 and C4, and a bias voltage is supplied from a bias voltage supply terminal 6. The capacitor C
Reference numerals 1 and C2 are used to cut off the DC components of the high-frequency signal input from the input terminal 1 and the high-frequency signal output from the output terminal 2.

Next, the operation of the PIN diode switch will be described. The high-frequency signal input to the input terminal 1 passes through the first terminal T1 of the 3 dB coupler 3 to the second terminal.
The signal is distributed to the terminal T2 and the third terminal T3 at a signal level about 3 dB lower, and the first and second PIN diodes D1 and D3 are distributed.
2 is input.

A bias voltage is supplied to the PIN diodes D 1 and D 2 from the bias voltage supply terminal 6 through the bias circuits 4 and 5. PIN diodes D1, D2
When a bias voltage is applied to the PIN diode, the high-frequency resistance of the PIN diode changes from a low resistance (about 0Ω) to a high resistance (about several kΩ) depending on the current flowing through the PIN diode. By utilizing this, when a bias is applied so that the high-frequency resistance of the PIN diode becomes approximately 50Ω, the PIN diode switch is turned on.

At this time, the PIN diodes D1, D2
Most of the high-frequency signals input to the terminals are terminated by the high-frequency resistors of the PIN diodes D1 and D2, but the remaining few high-frequency signals are transmitted to the PIN diodes D1 and D2.
, And is output to the fourth terminal T4 through the second terminal T2 and the third terminal T3 of the 3 dB coupler 3.

A high-frequency signal flowing from the first terminal T1 to the fourth terminal T4 of the 3 dB coupler 3 becomes a leak component. A composite component of this leak component and the reflected wave components from the PIN diodes D1 and D2 is output to the output terminal 2. Appearance reduces isolation.

FIG. 12 is a diagram showing the isolation characteristics of the switch of FIG. As the bias voltage is increased, the resistance of the PIN diodes D1 and D2 gradually decreases from a high value, and the isolation (dB) increases with the resistance. When the resistance value is 50Ω, the isolation is maximized. And the isolation voltage decreases when the bias voltage is further increased. The maximum isolation value is about 20 dB. The maximum value of the isolation at about 20 dB is due to the above-mentioned reason.

FIG. 13 is a vector diagram of output components at the maximum isolation value of the switch of FIG. 3
A composite vector of the leak component 101 from the first terminal T1 to the fourth terminal T4 of the dB coupler 3 and the reflected wave component 102 from the PIN diodes D1 and D2 becomes a signal component 103 appearing at the output terminal 2.

However, the conventional switch shown in FIG. 11 has been devised as an ideal switch, but has a problem that a maximum isolation value of only about 20 dB can be obtained. This is because the first and second PIN diodes D1
, D2, and 3d
This is because the combined vector appears at the output terminal 2 because there is a leak component from the first terminal T1 to the fourth terminal T4 of the B coupler 3.

Therefore, the present invention has been made in view of the problems in the above-described conventional PIN diode switch and the like, and is directed to a reflection type PI having high isolation.
An object is to provide an N diode switch.

[0034]

According to the first aspect of the present invention,
An input terminal, a duplexer coupler connected to the input terminal via a first capacitor via a first capacitor, a first PIN diode connected to a second terminal of the duplexer coupler, and a second A second PIN diode connected to three terminals, an output terminal connected to a fourth terminal of the duplexer via a second capacitor, and a bias circuit provided in each of the first and second PIN diodes. A first matching circuit connected between the second terminal of the duplexer coupler and the first PIN diode; a third terminal of the duplexer coupler;
A second matching circuit connected between the IN diode and the IN diode is provided.

According to a second aspect of the present invention, the matching circuit includes:
The reflected wave component from the PIN diode is set to have a length such that the phase is opposite to that of the leak component from the first terminal to the fourth terminal of the duplexer coupler.

According to a third aspect of the present invention, the matching circuit includes:
It is characterized by comprising a variable capacitor and an inductance connected in series to the variable capacitor.

According to a fourth aspect of the present invention, the matching circuit includes:
It is characterized by comprising a phase shifter.

According to the first aspect of the present invention, the leak of the signal flowing from the first terminal to the fourth terminal of the duplexer coupler and the reflected waves from the first and second PIN diodes are matched by the matching circuit. A PIN diode switch that can cancel each other and has high isolation can be obtained. Further, it is only necessary to add two matching circuits, and a reflection type PIN diode switch having a simpler circuit configuration than other conventional circuits can be obtained.

According to the second aspect of the invention, the phase of the reflected wave component from the PIN diode is opposite to the phase of the leak component of the signal flowing from the first terminal to the fourth terminal of the duplexer coupler. Since the matching circuit is set to have a length, the leak component can be canceled, and high isolation can be obtained.

According to the third aspect of the present invention, the matching circuit can be constituted by a simple circuit of a variable capacitor and an inductance connected in series with the variable capacitor, and by adjusting the impedance, the phase of the reflected wave component and the phase of the leak component can be adjusted. Can be adjusted so as to have opposite phases to each other, so that the leak component can be canceled and high isolation can be obtained.

According to the fourth aspect of the present invention, the matching circuit can be constituted by a single phase shifter, and the phase of the reflected wave component and the phase of the leak component can be easily adjusted so as to be opposite to each other. The components can be offset and high isolation can be obtained.

[0042]

Next, a specific example of an embodiment of a PIN diode switch according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a PIN diode switch according to an embodiment of the present invention. In this embodiment, a 3 dB coupler is used as a duplexer coupler. In the present embodiment, the first matching circuit 7 connected between the second terminal T2 of the 3 dB coupler 3 and the first PIN diode D1 in the PIN diode switch shown in FIG.
The second matching circuit 8 is provided between the third terminal T3 of the dB coupler 3 and the second PIN diode D2. Except for this, it is the same as the PIN diode switch shown in FIG.

FIG. 2 is a circuit diagram showing an example of the matching circuit of the embodiment of FIG. FIG. 2A shows an example in which the matching circuits 7 and 8 are configured by a variable capacitor CV and an inductance L connected in series to the variable capacitor CV. When the frequency is low (less than 2 GHz), it can be constituted by lumped constant circuit components, but when the frequency is high (2 GHz or more), it is constituted by a distributed constant circuit.

FIG. 2B shows an example in which the matching circuits 7 and 8 are constituted by a phase shifter 9. When using a phase shifter, there is a problem that the entire circuit becomes large.However, the phase shifter has a transfer function in which only the amount of phase changes with respect to the frequency and the amount of attenuation does not change. There is.

Next, the operation of the PIN diode switch of this embodiment will be described. The high-frequency signal input to the input terminal 1 is distributed through the first terminal T1 of the 3 dB coupler 3 to the second terminal T2 and the third terminal T3 at a signal level lower by about 3 dB, and the first and second matching circuits are provided. 7 and 8 are input to the first and second PIN diodes D1 and D2.

A bias voltage is supplied to the PIN diodes D 1 and D 2 from the bias voltage supply terminal 6 through the bias circuits 4 and 5. PIN diodes D1, D2
Bias before the high-frequency resistance becomes about 50Ω, that is, 5
When 0Ω + αΩ is applied, the PIN diode D1
, D2 are output to the fourth terminal T4 through the second terminal T2 and the third terminal T3 of the 3 dB coupler 3.

When the impedance is set to 50Ω + αΩ, the reflected wave component 13 has the same size as the leak component 11. On the other hand, the first terminal T1 to the fourth terminal T4 of the 3 dB coupler 3
Is also output to the fourth terminal T4. Then, the vector composite value of these signals is output to the output terminal 2.

Here, the first terminal T1 of the 3 dB coupler 3
From the first terminal T4 to the fourth terminal T4 and the reflected component of the high-frequency signal reflected from the PIN diode and output to the fourth terminal T4 so as to have a phase difference of 180 [deg.] (The opposite phase). If the length of the second matching circuit 7 and the length of the second matching circuit 8 are selected, the two high-frequency signals are canceled out and no high-frequency signal is output from the fourth terminal T4, so that high isolation is obtained.

FIG. 3 is a diagram showing the isolation characteristics of the switch of FIG. As you increase the bias voltage,
The resistances of the PIN diodes D1 and D2 gradually decrease from a high value, and the isolation (d
B) is getting bigger. PIN diodes D1, D
2 when the bias before the high-frequency resistance becomes about 50Ω is applied, the reflected signals from the PIN diodes D1 and D2 pass through the second terminal T2 and the third terminal T3 of the 3 dB coupler 3 to the fourth terminal T4. Is output.

The first and second matching circuits 7 and 8 are 3 dB
The leak component from the first terminal T1 to the fourth terminal T4 of the coupler 3 and the reflected wave component from the PIN diode have a phase of 1
Since the length is adjusted so as to differ by 80 ° (become out of phase), the isolation becomes extremely large at a bias value (high-frequency resistance value of 50Ω + αΩ) before the high-frequency resistance becomes about 50Ω.

FIG. 4 is a vector diagram of output components at the maximum isolation value of the switch of FIG. Reference numeral 11 denotes a leak component from the first terminal T1 to the fourth terminal T4 of the 3 dB coupler 3, reference numeral 12 denotes a reflected wave component from the PIN diode when the impedance of the PIN diode is 50Ω, and impedance of the PIN diode is 50Ω.
The reflected wave component from the PIN diode at + αΩ is represented by reference numeral 13.

The reason for setting the impedance to 50Ω + αΩ is to make the reflected wave component 13 the same size as the leak component 11. The phase of the reflected wave component 13 differs from that of the leak component 11 by 180 ° due to the matching circuits 7 and 8 (opposite phase).
It is converted to a signal component 14. Therefore, the leak component 11
The resultant vector of the signal and the signal component 14 is 0, and no high-frequency signal is output to the output terminal 2.

As described above, the matching circuits 7 and 8 use the PI
The reflected wave components from the N diodes D1 and D2 are 3 dB
By adjusting the leak component from the first terminal T1 to the fourth terminal T4 of the coupler 3 to a signal that is 180 ° out of phase (has an opposite phase), the leak component is cancelled, and a high-frequency signal is not output to the output terminal 2. To increase the isolation.

The above description is based on the assumption that the demultiplexer coupler is 3 dB.
Although an example using a coupler has been described, the present invention is not limited to a 3 dB coupler but is applied to a general duplexer coupler.

[0055]

As described above, according to the first aspect of the present invention, the leak component of the high-frequency signal flowing from the first terminal to the fourth terminal of the duplexer coupler and the first and second PIN diodes are used. The output of the output terminal 2 can be made 0 by providing a matching circuit for canceling the reflected wave of the above, and a PIN diode switch having high isolation can be provided. In addition, it is only necessary to add two matching circuits, and it is possible to provide a PIN diode switch having a simpler circuit configuration than other conventional circuits requiring a large number of circuit components.

According to the second aspect of the present invention, the reflected wave component from the PIN diode is converted into a phase having a phase opposite to that of the leak component of the signal flowing from the first terminal to the fourth terminal of the duplexer coupler. Since the matching circuit is set so as to have a high level, the leak component can be canceled out, and a PIN diode switch having high isolation can be provided.

According to the third aspect of the present invention, the matching circuit can be composed of a simple circuit of a variable capacitor and an inductance connected in series with the variable capacitor, and the phases of the reflected wave component and the leak component can be mutually adjusted by adjusting the impedance. Since the phase can be adjusted to have the opposite phase, the leak component can be canceled out, and a PIN diode switch having high isolation can be provided.

According to the fourth aspect of the present invention, the matching circuit can be constituted by one phase shifter, and the phase of the reflected wave component and the phase of the leak component can be easily adjusted so as to be opposite to each other. A PIN diode switch that can cancel and has high isolation can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a PIN diode switch according to the present invention.

FIG. 2 is a circuit diagram showing an example of a matching circuit of the PIN diode switch of FIG. 1;

FIG. 3 is a diagram illustrating an isolation characteristic of the PIN diode switch of FIG. 1;

FIG. 4 is a vector diagram of an output component at a maximum isolation value of the PIN diode switch of FIG. 1;

FIG. 5 is a circuit diagram showing a basic form of a switch using a PIN diode.

FIG. 6 is a circuit diagram of a first example of a conventional switch using a PIN diode.

FIG. 7 is a circuit diagram showing a first basic form of an attenuator using a PIN diode.

FIG. 8 shows a first example of an attenuator using a conventional PIN diode.
It is a circuit diagram of the example of FIG.

FIG. 9 is a circuit diagram showing a second basic form of an attenuator using a PIN diode.

FIG. 10 is a circuit diagram of a second example of a conventional attenuator using a PIN diode.

FIG. 11 is a circuit diagram of a second example of a conventional switch using a PIN diode.

FIG. 12 is a diagram illustrating isolation characteristics of the switch of FIG. 11;

FIG. 13 is a vector diagram of output components at the maximum isolation value of the switch of FIG. 11;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 input terminal 2 output terminal 3 3 dB coupler 4, 5 bias circuit 6 bias voltage supply terminal 7 first matching circuit 8 second matching circuit 9 phase transmitter

Claims (4)

[Claims] An input terminal, a duplexer coupler connected to the input terminal via a first capacitor via a first capacitor, a first PIN diode connected to a second terminal of the duplexer coupler, The second PI connected to the third terminal of the wave coupler
A PIN diode switch comprising: an N diode; an output terminal connected to a fourth terminal of the duplexer coupler via a second capacitor; and a bias circuit provided in each of the first and second PIN diodes. , A first matching circuit connected between a second terminal of the duplexer coupler and a first PIN diode; and a second matching circuit connected between a third terminal of the duplexer coupler and a second PIN diode. A PIN diode switch comprising: 2. The matching circuit converts a reflected wave component from the PIN diode into a length having a phase opposite to that of a leak component from a first terminal to a fourth terminal of the duplexer coupler. The PIN diode switch according to claim 1, wherein the PIN diode switch is set. 3. The PIN diode switch according to claim 1, wherein the matching circuit includes a variable capacitor and an inductance connected in series to the variable capacitor. 4. The PIN diode switch according to claim 1, wherein said matching circuit comprises a phase shifter.