TW507375B - A millimeter-wave passive FET switch using impedance transformation networks - Google Patents

Abstract

The present invention provides a millimeter-wave passive FET switch by using impedance transformation network to transfer the effective capacitor seen from the drain to source of an FET at off-state to low impedance, while transfer low impedance seen at on-state to high impedance. Since both on-state and off-state are transferred to high impedance and low impedance respectively, a high-performance switch can be achieved. Since the size of the transformation network is small, the performance of the switch can be promoted with low cost.

Description

/ 375 V. Description of the invention (1) The present invention relates to a signal switcher circuit, in particular to a millimeter wave band passive field effect transistor signal switcher circuit designed with an impedance switching circuit. In millimeter-wave radio communication systems, high-frequency switches are one of the most important components. When designing high-frequency circuits, the efficiency of the circuit is often limited by the characteristics of the components. For millimeter-wave high-frequency switches, the characteristics of the components limit the isolation of the switch in the on / off state (13〇1 &1; 丨 〇11), because at high frequencies, when used in the field When the effective transistor is in the off state, the transistor's electrode and source can be regarded as an equivalent capacitor and present a low impedance instead of a high impedance, thereby affecting the performance of the entire circuit. In addition, in high-frequency circuits, signals often produce coupling effects between adjacent transmission lines, thus affecting the performance of the circuit. This is the reason why the switcher's isolation impedance performance in the high frequency band is not ideal.

Single-crystal microwave switches made using PI N diodes have good switching characteristics in the millimeter wave band. However, p I N diodes cannot be manufactured in the process of MMIC (Monolithic Microwave Integrated Circuit) of η e MT (High Electron Mobility Transistor, a kind of FET), so the use of HEMT to manufacture microwave switches is still popular. When using high-power passive HEMT (FET), it also has better linearity than the diode, and can be combined with other transceiver modules (T / R) in the communication system on one chip. For the frequency range below 20GHz, it can be made into a device through parallel or series connection of the FET and the transmission line.

Switcher 'But for higher frequencies, the performance of the switcher will be greatly improved due to the capacitive effect between the electric two IS i; so most of the infra-wave switchers use inductors and transistors $: pole source The capacitor resonates', but even so, the switch is isolated; the effect is still less than 30dB (see references [丨] — [4]). In order to increase the isolation of the switch, a quarter-wave transmission line can be used to increase the distance between the component and the signal transmission line, thereby greatly reducing the coupling effect of the component ^ signal transmission line, which greatly improves the isolation of the switch (please, (See reference [5]). This method successfully produced a 44GHz switch, but the ministry significantly increased the size of the switch and increased production costs. In addition to the above method, it can also be made using the phase cancellation method of the Lange coupler to obtain good isolation (see reference [6 D. However, this method uses several 90 ° Lange couplers, so the layout area is still It is a major disadvantage. In recent years, there is a method in the literature to design a switch using HJFET MMIC. Its operating frequency range is DC ~ 60GHz, and it has good isolation performance (see references [7]-[8]). But this The method must adopt a special process and layout method to achieve ohmic electrode sharing technology for HEMT components. References [1] M · J · Schindler and A · Morris, '丨 DC-40 GHz and 20- 40 GHz MMIC SPDT switches, M IEEE Trans, on 507375 5. Invention Description (3)

Microwave Theory Tech., Vo1. MTT-35, no. 12, pp. 1486-1493, Dec. 1987.

[2] P. Bermkopf, M. Schindler, and A. Bertrand, nA high power K / Ka-band monolithic T / R switch, " in 1991 IEEE Microwave & Millimeter-wave Monolithic Circuits Symposium Digest, pp.15- 18, June 1991.

[3] G · L. Lan, D · L. Dunn, JC Chen, C · K. Pao and DC Wang. &Quot; A high performance V-Band monolithic FET transmi t-rece i ve switch,!? In 1988 IEEE Microwave & Millimeter-wave Monolithic Circuits Symposium Digest, pp. 99-101, June 1988.

[4] M. Aust, H. Wang, R. Carandang, K. Tan, C. H, Chen, T. Trinh, R. Esfandiari and HC Yen, " GaAs monolithic components development for Q-Band phased array application, ”In 1992 IEEE MTT-S International Microwave Symposium Digest, vol. 2, pp.703-706, June 1991.

[5] DL Ingram, K. Cha, K. Hubbard, and R. Lai, “Q-band high isolation GaAs HEMT switches,” in 1996 IEEE GaAs IC Symp, Dig., Orlando, FL, pp. 289-282, Nov. 1996 · [6] D. C. W. Lo, H. Wang, Barry R. Allen, G. Dow, Kwo Wei Change Michael Biedenbender, Richard Lai, Sian Chen, Daniel Yang, " Novel monolithic

Page 7 507375 V. Description of the invention (4) multi functional balanced switching low-noise amplifiers, " IEEE Trans · on Microwave Theory and Tech ·, vol. 42, no · 12, pp · 2629-2634, Nov · 1998 · [7] H. Mizutani, N. Funabashi, M. Kuzuhara, Y.

Takayama, " Compact DC-60-GHz HJFET MMIC switches using ohmic electrode-sharing technology, "IEEE Trans. On Microwave Theory and Tech., Vol. 46, no · 11, pp. 1597-1603, Nov. 1998.

[8] Kenichi Maruhash i, Hiroshi Mizutani, Keiichi Ohata, "Design and performance of a Ka-band monolithic phase shifter utilizing nonresonant FET switches, 11 IEEE Trans, on Microwave Theory and Tech., Vol. 48, no. 8, pp 1313-1317, Aug. 2000.

[9] Yu ~ Jiu Wang, Kun-You Lin, Dow-Chih Niu, and Iluei Wang,, fA V ~ band MMIC SPDT passive IIEMT switch using impedance transformation networks, 11 in 2 0 0 1 IEEE MTT-S International Microwave Symposium Digest., Phoenix, vol. 1, pp. 253-256, May, 2001. Purpose of the invention The purpose of the present invention is to design a millimeter wave band passive field effect transistor signal switcher using an impedance conversion circuit, utilizing the standard manufacturing process of HEMT, Reduce the layout size of the chip and increase the efficiency of the high frequency switch.

ju / 375 V. Description of the invention (5) It is stated clearly that the microwave switch is usually designed in series or in parallel with a transistor or diode on the signal line. The voltage or resistance of the transistor or diode is controlled by the voltage. The switching diagram is shown in parallel with a field effect transistor (FET) T1 on the side of the signal line SL, where the -gate G of the transistor T1 is connected to a control voltage v to control the field effect transistor. The switching resistance between the drain D and the source S, and the drain D and the source s are connected in parallel with the signal line SL and grounded. In the lower frequency band, because the characteristics of the field effect transistor (FET) Tl are good, this method of parallel circuit elements is very suitable. However, for the millimeter-wave frequency band, the characteristics of the FET element are aliased. When the voltage is controlled, the FET cannot be completely opened. This is because the capacitor d between the drain d and the source S of the field effect transistor n shows a capacitor effect Therefore, it becomes a low-impedance impedance at high frequencies, which makes the isolation (is〇 〖ati 〇n) of the entire switcher poor. In order to make the switching characteristics of the component good, the present invention adopts an impedance conversion circuit connected in parallel to the signal line, as shown in the second figure, where the specific impedance seen at point A is shown on the Smith Chart in the third figure. The off states are points A (on) and A (0ff). At this time, no impedance matching circuit has been added, as shown in the first figure. At this time, the equivalent of point B_on and off states are equivalent to the point of C. The on and off states are respectively first connected in series with the first transmission line Step 1. The impedance is shown on the Smith Chart in the third figure Points B (on) and B (off). Next, connect the second transmission line Step 2 in parallel. The impedance is shown on the Smith Chart in the third figure.

Page 9 ^ 7375 5 Description of the invention (6) is C (on) and C (off) points. Finally, the third section of the transmission line Step 3 is connected in series. At this time, the equivalent impedance seen at point D is shown on the it chart in the second figure. The on and off states are points D (on) and D (off), respectively. After the conversion of the second segment of the transmission line, it can be clearly seen from the gmi chart that the equivalent switching impedance seen by the signal for the transistor and the impedance conversion circuit has been changed from points A (on) and A (〇ff) to the ideal D (On), D (Off) points. This proves that when the transistor and the impedance conversion circuit are connected in parallel to the signal line, they can exhibit excellent switching functions. Point D (on) actually becomes an open circuit, and point D (o f f) becomes a short circuit. The fourth figure is a schematic diagram of a complete single pole double throw switch. According to the above method of the present invention, two single crystal microwave integrated circuits were successfully manufactured. After measurement, it was confirmed that the performance was excellent, and its size was only 1% 2mm2 (see reference [9]), which is much smaller than the general 2 X 5mm2 ( (See reference [5]). In the above special case, the way that the field effect transistor (FET) T1 and the impedance conversion circuit are connected by 叩 1, Step 2, Step 3 and then connected in parallel with the signal line SL can also be changed to a series connection with the ring line SL. . The spirit and scope of the present invention are limited only by the scope of the following patent applications, and are not limited by the above-mentioned special cases. Page 10 507375 Brief description of the diagram The first diagram is the circuit diagram of a general microwave switcher. The second figure is a circuit diagram of a microwave switcher equipped with an impedance conversion circuit according to the present invention. The third figure is a schematic diagram of a Smith Chart impedance change of the microwave switch of the present invention. The fourth figure is a complete single-pole double-throw switch circuit diagram of the present invention. Φ

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Claims (1)

507375 VI. Application for patent scope 1. A millimeter wave band passive field effect transistor signal switcher, including a signal line, a field effect transistor, and an impedance conversion circuit, wherein a closed pole and a control voltage of the field effect transistor The resistance and source connected between the drain and source of the field effect transistor are connected in series with the impedance conversion circuit, and then formed in parallel or connected with the signal line. 2 · The switcher according to item 1 of the patent application range, wherein the impedance conversion circuit is a combination of transmission lines. 3. If the scope of the patent application is No. 2 and the switch of item 2, the impedance conversion circuit is designed so that the equivalent switching impedance of the switch circuit does not contain capacitive or inductive reactance as much as possible. 4 · The switcher as claimed in item 3 of the patent scope, wherein the design of the impedance conversion circuit enables the equivalent capacitance presented by the off-state (0f f-State) of the field effect transistor at high frequency via the impedance conversion circuit Into a low impedance; and the low impedance presented by its on-state is converted into a high impedance through an impedance conversion circuit, so a switch with good performance is formed.