KR100611107B1 - Absorptive rf switch with the performance of high power and high isolation - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an absorption type RF switch having high power and high isolation characteristics.

2. The technical problem to be solved by the invention

An object of the present invention is to provide an RF switch that simultaneously satisfies high power, high isolation and input / output impedance matching characteristics by connecting a plurality of transistors in parallel ground and inserting a resonator between the transistors.

3. Summary of Solution to Invention

The present invention provides an RF switch comprising: a plurality of transistors connected in parallel ground to a radio frequency (RF) transmission line; And a plurality of resonators connected between the plurality of transistors to form an open circuit between input and output terminals when the transistor is shorted to increase insertion loss.

4. Important uses of the invention

The present invention is used in the communication device of the ultra-high frequency and microwave band.

 RF Switches, High Power, High Isolation, Transistors, Resonators

Description

Absorptive RF Switch With the performance of High Power and High Isolation

1 is a diagram illustrating an RF switch using a general parallel grounded FET transistor;

2 is a diagram illustrating a high power RF switch in which the structure of the RF switch of FIG. 1 is modified;

3 is a configuration diagram of an embodiment of an RF switch according to the present invention;

4 is a configuration diagram of another embodiment of an RF switch according to the present invention;

5 is a graph illustrating an embodiment of insertion loss and return loss characteristics in an RF path connection state of an RF switch according to the present invention;

FIG. 6 is an embodiment graph showing isolation and return loss characteristics in an RF path switching state of an RF switch according to the present invention; FIG.

7 is a graph showing an embodiment of a third order intermodulation distortion (IMD3) characteristic of an RF switch according to the present invention;

FIG. 8 is a diagram illustrating a manufacturing layout of a 3 GHz band RF switch MMIC designed with the structure of FIG. 4.

* Explanation of symbols for the main parts of the drawings

312, 332: ground resistance 340, 350: resonator

360: RF transmission line

The present invention relates to an RF switch used in communication equipment and components of ultra-high frequency and microwave bands, and more particularly, to an RF switch capable of connecting or switching an RF signal path using a transistor semiconductor of a kind similar to an FET. will be.

The RF switch using a general transistor has a structure in which a transistor is connected in series in the middle of a transmission line constituting an RF path or a transistor is connected in parallel ground. In the case of such an RF switch, the RF path is connected or isolated by adjusting the bias of the transistor to turn the transistor ON or OFF.

FIG. 1 is a diagram illustrating an RF switch using a general parallel grounded FET transistor. In the RF switch illustrated in FIG. Connect or switch over.

The RF switch having the structure of FIG. 1 has a maximum power characteristic determined according to the size of the transistor, so that the larger the RF power that the RF switch is to handle, the larger the transistor should be used. In this case, the isolation degree in the RF path switching state Properties may be degraded.

In addition, if the use frequency is increased for a transistor having a constant size due to the characteristics of the transistor, the isolation characteristic is exponentially reduced. In the structure of FIG. 1, the RF switch input / output impedance in the RF path switching state becomes 0 ohm and all RF power input and output are reflected.

FIG. 2 is a diagram illustrating a high power RF switch in which the structure of the RF switch of FIG. 1 is modified, in which a transistor is added to the RF switch of FIG. 1 in series.

Although the RF switch illustrated in FIG. 2 has a structure in which the maximum voltage that the switch can handle increases by the number of transistors to increase the maximum operating power, isolation characteristics are deteriorated. Also, like the RF switch shown in FIG. 1, impedance matching cannot be achieved in the RF path switching state.

As described above, conventional RF switches using transistors improve the isolation and RF power of RF switches by utilizing the characteristics of a single transistor or by simply connecting several transistors in series or in parallel.

However, the above-described conventional RF switch has a problem that the isolation characteristic of the RF switch is determined according to the performance of a single transistor, and in particular, the isolation characteristic is significantly reduced as the use frequency is increased. In addition, there is a problem that the isolation is degraded when multiple transistors are connected in series to parallel ground to increase the maximum power.

That is, in the development of the RF switch using a transistor, there was an effort to improve only one of the high power characteristics, the high isolation characteristics, and the input / output impedance matching characteristics that the RF switch should have. Not at all.

The present invention has been proposed to solve the above problems, and provides an RF switch that simultaneously satisfies high power, high isolation, and input / output impedance matching characteristics by connecting a plurality of transistors in parallel ground and inserting a resonator between the transistors. The purpose is.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The present invention for achieving the above object, the RF switch, a plurality of transistors connected in parallel ground to the RF (Radio Frequency) transmission line; And a plurality of resonators connected between the plurality of transistors to increase an insertion loss by forming an open circuit between input and output terminals when the transistor is shorted.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a configuration diagram of an embodiment of an RF switch according to the present invention.

The RF switch according to the present invention shown in FIG. 3 includes three parallel grounded transistors Q1, Q2 and Q3 and resonators 340 and 350 inserted into the transistor connection portion, and three parallel grounded transistors ( Two transistors Q1 and Q3 connected to the input / output terminals among Q1, Q2, and Q3 include ground resistors 312 and 332 at a source terminal.

In the RF switch of FIG. 3, the transistors Q1 and Q3 connected to the input / output terminals do not contribute much to isolation, but when the transistors are shorted, an open circuit is formed between the input / output terminals by resonators 340 and 350 inserted between the transistors. This increases insertion loss and improves isolation. In this case, the resonators 340 and 350 may be configured using only the microstrip transmission line, the inductor and the capacitor, or the microstrip transmission line, the inductor and the capacitor according to the frequency band used or the size of the RF switch. It is constructed using together.

In addition, when the transistors Q1 and Q3 having the ground resistors 312 and 332 connected to the input / output terminals are shorted, the ground resistors 312 and 332 are seen when viewed from the input / output terminals. Therefore, when the ground resistance is selected in consideration of the short-circuit resistance of the transistor, the input and output impedance matching can be achieved.

In addition, the RF switch of FIG. 3 has three transistors Q1, Q2, and Q3 in parallel ground with respect to the RF path, so that the transistors Q1, Q2, and Q3 all act as open circuits in the RF path connection state. . Therefore, the RF power that the transistor can handle in the RF path connection state becomes larger than when the transistor is shorted, and also the amount of RF power that can be handled by the number of transistors connected in parallel ground.

4 is a configuration diagram of another embodiment of an RF switch according to the present invention.

The RF switch shown in FIG. 4 uses four parallel ground transistors Q1, Q2, Q3, Q4 as an extension of the FIG. 3 structure. The operation of the switch is similar to that of FIG. 3, and by adding one parallel ground transistor and a resonator in the middle, it is possible to improve the isolation and the maximum operating power. Also, impedance matching in the RF path switching state of the switch can be achieved by transistors Q1 and Q4 having ground resistors 412 and 442 connected to the input and output terminals.

Hereinafter, a measurement result after fabrication of an RF switch operating in the 3 to 4 GHz band having the structure of FIG. 4 will be described. At this time, the RF switch of FIG. 4 is manufactured under the following conditions.

A) The four transistors (Q1, Q2, Q3, Q4) used are all the same and the specifications are as follows.

0.15um gate length

-4 Fingers

200 um gate width

-GaAs PHEMT

B) The resistors 411, 421, 431, and 441 connected to the gates of the transistors are all the same and have a resistance of 425 Ohms.

C) The resonators 450, 460, and 470 connected to the transistors are designed as microstrip spiral inductors and MIM type capacitors, and operate in the 3 ~ 4GHz band. The resonators 450, 460, and 470 interact with the short-state impedances of the transistors Q1, Q2, Q3, and Q4 and generate resonance.

D) The ground resistors 412 and 442 are all the same and have a resistance value of 50 Ohm.

5 is a graph illustrating an embodiment of insertion loss and return loss characteristics of an RF path connection state of an RF switch according to the present invention.

The insertion loss 501 of the switch and the reflection loss 502 at this time are measured when the gate control voltage of VG = -2.0V is applied to the RF switch of FIG. As shown in FIG. 5, the fabricated RF switch has an insertion loss characteristic of 2 dB or less in the 3 to 4 GHz band, and a return loss characteristic of 13 dB or more in the same band.

FIG. 6 is an exemplary graph illustrating isolation and return loss characteristics in an RF path switching state of an RF switch according to the present invention. FIG.

4 shows the isolation loss 601 and the reflection loss 602 at this time, which are the insertion loss of the switch measured when the gate control voltage of VG = 0V is applied to the RF switch. As shown in FIG. 6, the fabricated switch has a isolation characteristic of 63 dB or more in the 3 to 4 GHz band and a return loss characteristic of 22 dB or more in the same band.

7 is a graph illustrating an embodiment of a third order intermodulation distortion (IMD3) characteristic of an RF switch according to the present invention.

FIG. 4 shows the third order intermodulation distortion (IMD3) characteristic 701 of the switch measured when a RF voltage of VG = -2.0V is applied to the RF switch. The input signal for measurement is two RF signals with frequencies of 3.4 GHz and 3.41 GHz, with each RF signal being input at a power of +2 dBm. The output power is 0 dBm, respectively, and the measured third-order intermodulation distortion characteristic is 64 dBc as shown in FIG. 7.

FIG. 8 is a diagram illustrating a manufacturing layout of a 3 GHz band RF switch MMIC designed with the structure of FIG. 4.

8 is an input RF transmission line corresponding to 480 of FIG. 4, and 850 of FIG. 8 is a resonator corresponding to 450, 460, and 470 of FIG. 4 and is an integrated L-C resonator in consideration of transistor arrangement.

In addition, 810 of FIG. 8 corresponds to transistor Q1 on the input terminal side of FIG. 4, and 820 and 830 of FIG. 8 correspond to transistors Q2 and Q3 in the switch center of FIG. 4, respectively. 840 in FIG. 4 corresponds to transistor Q4 on the output terminal side of FIG.

In addition, 811, 821, 831, and 841 of FIG. 8 correspond to 411, 421, 431, and 441 of FIG. 4, respectively, and are resistors on the bias supply line of the transistor, and 812 and 842 of FIG. Parts respectively corresponding to 442 are ground resistances of the input / output terminal side transistors Q1 and Q4.

8, 890 of FIG. 8 is a terminal corresponding to 490 of FIG. 4, and is a terminal for applying a transistor bias voltage capable of adjusting connection and switching of an RF switch.

The MMIC characteristics of FIG. 8 are the same as those of FIGS. 5 to 7 described above.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention can achieve input / output matching even in an RF path switching state while having high power and high isolation characteristics in an ultra high frequency band.

In addition, the present invention has a low insertion loss in the RF path connection state in which the transistor operates in an open circuit since the transistors are all connected to parallel ground.

Claims (5)

A plurality of transistors connected in parallel to a radio frequency (RF) transmission line; And A plurality of resonators connected between the plurality of transistors to increase an insertion loss by forming an open circuit between input and output terminals when the transistor is shorted; RF switch comprising a. The method of claim 1, The transistor connected to the input and output terminals of the plurality of transistors is a resistor connected to the source terminal to match the input and output impedance, the remaining transistor is characterized in that the source terminal is directly grounded. The method of claim 1, The resonator, An RF switch constructed using a microstrip transmission line and generating resonance by interacting with a short-state impedance of the transistor. The method of claim 1, The resonator, An RF switch constructed using an inductor and a capacitor and interacting with the short-state impedance of the transistor to generate resonance. The method of claim 1, The resonator, An RF switch constructed using a microstrip transmission line, an inductor, and a capacitor and interacting with a short-state impedance of the transistor to generate resonance.

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