JPH04105417A - High frequency switching circuit - Google Patents

Abstract

PURPOSE:To make a high frequency switching circuit small in a semiconductor integrated circuit by employing a resistor causing an insertion loss of a field effect transistor(TR) for a component of an attenuator in the high frequency switching circuit so as to provide a function of a matching circuit to the high frequency switching circuit. CONSTITUTION:A high frequency signal inputted from a high frequency input terminal passes through a field effect TR(FET) Q1 in the on-state and is reflected in a FET Q3 in the OFF-state and outputted to a high frequency output terminal A. On the other hand, since the FET Q2 is in the OFF state, the inputted high frequency signal is reflected entirely by the FET Q2 and not outputted at a high frequency output terminal B. In this case, an insertion loss is caused by an ON resistor R of the FET Q1. The resistor R is regarded as part of the attenuator and a resistor RA is connected in parallel with the high frequency input terminal and the high frequency output terminal respectively so that the impedance when viewing the high frequency input terminal is in matching with a load impedance (50ohms). Thus, when the circuit is realized by the semiconductor integrated circuit, the circuit constitution is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to high frequency switching circuits, and in particular to microwave integrated circuits.

2. Description of the Related Art Conventionally, this type of high-frequency switch circuit consists of field effect transistors Q++ to QI4 as shown in FIG. 3, an input-side matching circuit 1, an output-side matching circuit 2.3, and a control terminal C0NT.
II, C0NT12. In this circuit, when a high frequency is input from the high frequency input terminal, it passes through the input side matching circuit 1. The high frequency that passed through the input matching circuit 1 is
With the control terminals C0NTII and C0NIT12, the signal passes through Q++ or Q12 connected in series, passes through the output side matching circuit 2 or 3, and is outputted to an arbitrary high frequency output terminal.

Problems to be Solved by the Invention However, in this conventional high frequency switch circuit, a matching circuit is inserted at the input and output terminals for the purpose of matching, resulting in a large circuit configuration. Furthermore, since matching circuits are inserted at the input and output terminals, there is a drawback that matching must be achieved using each matching circuit.

The present invention has been made in view of the above-mentioned conventional situation,
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel high-frequency switch circuit that makes it possible to eliminate the above-mentioned drawbacks inherent in the conventional technology.

Means for Solving the Problems In order to achieve the above object, the high frequency switch circuit according to the present invention has an attenuator for the insertion loss of the field effect transistor constituting the high frequency switch by connecting a resistor in parallel to the high frequency switch circuit. The high frequency switch circuit has the function of a matching circuit.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

Referring to FIG. 1, in one embodiment of the present invention, a high frequency input terminal and a high frequency output terminal A=H each have a resistor R.
A is connected. Here, the field effect transistor Q2 is controlled by the control terminal C0NTl of the field effect transistor.
, Q3 are in the OFF' state, and the field effect transistors Q1 and Q4 are in the OFF state by the control terminal C0NT2.

The high frequency input from the high frequency input terminal passes through the field effect transistor Ql which is in the ON degree state, is reflected by the field effect transistor Q3 which is in the 'OFF' state, and is output to the high frequency output terminal A.

On the other hand, since the field effect transistor Q2 is in the "OFF" state, all of the input high frequency is reflected by the transistor Q2 and is not output to the high frequency output terminal B.

At this time, the high frequency is ON° of the field effect transistor Q1.
Resistance R causes insertion loss. Regarding this resistor R as a part of the attenuator, a resistor RA is connected in parallel to the high frequency input end and the high frequency output end, respectively, so that the impedance seen from the high frequency input side matches the load impedance (50Ω). Make an equivalent circuit to the π-type attenuator shown in Figure 2.

If the above circuit configuration is realized on a semiconductor integrated circuit, not only will the circuit configuration be made smaller, but even if matching is not achieved, the value of the resistor RA can be changed by wiring. It is possible to achieve sufficient matching and has a large degree of freedom.Also, in terms of process, matching can be achieved with wiring, which is quite beneficial, such as shortening the process period.

In this embodiment described above, the field effect transistor Q1
．． Q4 is in the "ON" state, field effect transistor Q2.
Although Q3 is set in the "OFF" state, the same explanation can be made by setting the transistors Q2 and Q3 in the "ON" state and the transistors Q3 and Q4 in the 'OFF' state.

In addition, the present invention provides 1-input, 3-output or n-output (multi-output) circuits when there are three or n circuits including the series transistor Ql or Q2 and the parallel transistor Q or Q4 shown in FIG. It can be expanded to a switch circuit, and if the number of inputs is two or more, it can also be expanded to a multi-input, multi-output switch circuit.

As described in detail, according to the present invention, by using the insertion loss of a field effect transistor in a high frequency switch circuit as a component of an attenuator, the high frequency switch circuit can perform the function of a matching circuit in addition to the original function of a switch. Additionally, it is possible to reduce the size of the high frequency switch circuit on the semiconductor integrated circuit.

Further, according to the present invention, since there is a high degree of freedom in matching, it is possible to obtain the effect of shortening the process period.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram showing an embodiment of the high frequency switch circuit according to the present invention, Figure 2 is an equivalent circuit diagram when high frequency is input in Figure 1, and Figure 3 is the configuration of a conventional high frequency switch circuit. It is a diagram. Qr, Q2. Ql, Q4. Ql + , Ql2. Ql
3. Ql4...Field effect transistor, Rg...Resistance for gate bias of field effect transistor, C0NT
l , C0NT2, C0NTl 1 , C0NT12
... Control terminal of field effect transistor, RA ... Insert resistance for attenuator configuration, R ... Resistance in "ON" state of field effect transistor, 1.2.3 ... Matching circuit Q1
~Q, a: Field effect transistor Rg: Li field effect transistor gate bias Fa anti-C0NTl,
C0NT2: Control terminal of field effect transistor Fig. 1 Patent applicant: NEC Co., Ltd. Representative Patent attorney: Yutabe Kumagai RA, Kaminari coffin for constructing a shield R: Responsible for ON-state dragon of electric field effect transistor anti-diagram 2

Claims (2)

[Claims] (1) The drains of the first and second field effect transistors are connected to form one high frequency input terminal, and
The third and fourth transistors are connected to the sources of the field effect transistors, respectively.
a first control terminal that connects the drains of the field effect transistors in parallel to form two high frequency output terminals, and applies a voltage in common to the gates of the first and fourth field effect transistors; 1 input 2 with a second control terminal that commonly applies a voltage to the gates of the third field effect transistors;
In the high frequency switch circuit at the output end, the first field effect transistor is turned on, and the insertion loss when the high frequency input from the input end passes between the drain and source of the first field effect transistor is attenuated. A first resistor connected in parallel to the high-frequency input terminal and a second resistor connected in parallel to the high-frequency output terminal constitute a π-type attenuator, and a matching circuit is included in the high-frequency switch circuit. A high frequency switch circuit featuring: (2) The second field effect transistor is turned on instead of the first field effect transistor, and the high frequency input from the input terminal passes between the drain and source of the second field effect transistor. Considering the insertion loss at the time as a component of the attenuator, the first resistor connected in parallel to the high frequency input terminal and the third resistor connected in parallel to the high frequency output terminal constitute a π-type attenuator, and the high frequency The high frequency switch circuit according to claim 1, further comprising a matching circuit in the switch circuit.