KR20010056861A - Dual band rf switch module - Google Patents

Abstract

PURPOSE: A high frequency switch for dual band is provided to improve the transmission capacity by improving the isolation capacity between the transmission end and the receiving end. CONSTITUTION: In the high frequency switch for dual band, a low band pass filter(21), connected to the antenna, filters the first and second bandwidth frequency signals. A duplexer(22) receives the received signals from the low bandwidth pass filter(21), divides the signals into the first bandwidth and second bandwidth signals, and passes the divided signals. The duplexer(22) also sends the transmitting signals from the first and second bandwidths to each low bandwidth pass filter(21). The first switching unit(23) selects between the transmission and the receiving modes responding to the first switching voltage and transceives the signals between the duplexer(22) and the antenna. The second switching unit(24) selects between the transmission and the receiving modes responding to the second switching voltage and transceives the signals between the duplexer(22) and the antenna.

Description

Dual band high frequency switch {DUAL BAND RF SWITCH MODULE}

The present invention relates to a dual band high frequency switch, and more particularly, to a dual band high frequency switch used in a mobile terminal, in which a transmission (TX) mode is used to improve the isolation (Isolation) characteristics between the transmitting and receiving ends. It relates to a high frequency switch for.

In general, a mobile terminal such as a mobile phone is a terminal capable of receiving a communication service of a specific channel (band). By using a communication service, there are GSM (TX: 890 ~ 915MHz, RX: 935 ~ 960MHz) and CT-2 (TX: 900MHz, RX: 300MHz) terminals. The other is to provide a communication service using a frequency band of approximately 1.8 GHz, such as DECT (Digital Europe Cordless Telephone), PCS (Personal Communication System), DCS-1800 (TX (1.71 ~ 1.785GHz, RX: 1.805 ~ 1.88GHz)

In order to receive the two communication services, the mobile terminal must be designed to operate in the dual mode. A mobile terminal capable of receiving the two communication services is called a dual mode mobile terminal. The dual mode mobile terminal includes a dual band high frequency switch for selecting two communication services and transmitting and receiving a selected communication service. Such a dual band high frequency switch is modularized to the terminal. It is built.

1 is a schematic system configuration diagram of a conventional dual band high frequency switch, and FIG. 2 is a circuit diagram of a conventional dual band high frequency switch. As shown in FIGS. 1 and 2, the conventional dual band high frequency switch includes a low pass filter 10 for passing a first band (channel 1) and a first band and a first band of the frequency band through the low pass filter 10. A duplexer filter (11) for separating and passing two bands and providing transmission signals of a first band and a second band to the low pass filter (10), and a first through the duplexer (11) according to a first switching voltage A first switching circuit part 12 for selectively switching a reception signal and a transmission signal of a band, and a second switching circuit part for selectively switching a reception signal and a transmission signal of a second band through the duplexer 11 according to a second switching voltage. (13) is provided.

In such a configuration, in the conventional dual band high frequency switch, the transmission operation is performed when the first and second switching voltages are high, and the reception operation is performed when the first and second switching voltages are low. As an example, the operation in the first band will be described in detail. When the first switching voltage is high, the first diode D1 and the second diode D2 are turned on to transmit data from the transmission output terminal of the first band. The first diode D1 and the coupling capacitor CC1 are output to the antenna ANT through the duplexer 11 and the low pass filter 10. On the other hand, when the first switching voltage is low, the first diode D1 is turned off and only the second diode D2 is turned on so that the signal received through the antenna passes the low pass filter 10, the duplexer 11, and the inductor. It is input to the receiving input terminal of the first band.

However, in the conventional dual band high frequency switch, parasitic inductor components of 1 nH or less are generated when the first to fourth diodes D1 to D4 are on, and parasitic capacitor components of 1 pF or less are generated when the first to fourth diodes D1 to D4 are turned off. Therefore, since the second diode D2 is turned on during the transmission operation and the parasitic inductor component caused by the parasitic inductor component does not short the receiving end, the isolation characteristic is deteriorated and thus the insulation characteristic is deteriorated. There was a problem of poor performance.

Similarly, in the case of the transmission operation of the second band, a parasitic inductor component generated by turning on the fourth diode D4 causes a problem in that the insulation performance between the transmission and reception terminals of the second band is deteriorated, thereby degrading transmission performance.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, the purpose of which is to improve the transmission performance by improving the insulation characteristics between the transmitting and receiving end in the dual-band high-frequency switch used in the mobile terminal It is to provide a high frequency switch.

1 is a schematic system configuration diagram of a conventional high-frequency switch for dual band.

2 is a circuit diagram of a conventional dual band high frequency switch.

3 is a configuration diagram of a high frequency switch for dual band according to the present invention.

FIG. 4 is an equivalent circuit diagram of FIG. 3 when transmitting a first band.

FIG. 5 is an equivalent circuit diagram of FIG. 3 when transmitting a second band.

6 is an equivalent circuit diagram of a dual band high frequency switch according to the present invention in a receiving operation.

Explanation of symbols on the main parts of the drawings

21 low pass filter, 22 duplexer,

23 ... first switching circuit section, 24 ... second switching circuit section.

In order to achieve the above object, the dual-band high-frequency switch according to the present invention is connected to the antenna and the low pass filter for passing the frequency signals of the first band and the second band,

A duplexer configured to pass the received signal input through the low pass filter into one band and a second band according to the frequency band and to output the transmission signal output from the first band and the second band to the low pass filter, respectively; ,

A first switching circuit unit for selectively switching a reception signal and a transmission signal of a first band according to a first switching voltage to input / output an antenna through the duplexer;

And a second switching circuit unit configured to selectively switch the reception signal and the transmission signal of the second band according to the second switching voltage to input / output through the duplexer.

Hereinafter, with reference to the accompanying drawings the configuration and effect of the dual-band high-frequency switch according to the present invention will be described in detail.

Figure 3 shows the configuration of a dual band high frequency switch in accordance with the present invention. As shown in FIG. 3, the dual band high frequency switch according to the present invention has a low pass filter 21 connected to an antenna ANT to pass a use frequency band, and a frequency band through the low pass filter 21. The first band and the second band are separated from each other, and the duplexer 22 which transmits the transmission signals of the first band and the second band to the low pass filter 21 and the first switching voltage Vc1 are used. The first switching circuit unit 23 for switching the selection of the reception signal and the transmission signal of the first band through the duplexer 22 and the reception signal and the transmission signal of the second band are selected according to the second switching voltage Vc2. A second switching circuit unit 24 is switched to input / output through the duplexer 22.

In this configuration, the low pass filter 21 sets the pass frequency to pass through the frequencies of both the first band and the second band using at least one capacitor C1 and the inductor L1, wherein One band is a frequency band for providing one communication service (for example, TX: 890 to 915 MHz, RX: 935 to 960 MHz), and the second band is another communication using a frequency different from the communication frequency of the first band. The frequency band in which the service is provided (eg TX: 1.71 ~ 1.785GHz, RX: 1.805 ~ 1.88GHz).

The duplexer 22 includes a low pass filter 22-1 for passing the first band (channel 1) and a high pass filter 22-2 for passing the second band (channel 2). The low pass filter 22-1 of the first band is configured to pass a frequency band for receiving an applied communication service. For example, as shown in FIG. 3, the low pass filter 22-1 includes a capacitor C2 to C4 and an inductor L2. Can be. In addition, the high pass filter 22-2 is configured to pass a frequency band for receiving another applied communication service. For example, the high pass filter 22-2 includes a capacitor C5 and an inductor L3 and L4. can do.

The first switching circuit unit 23 is formed of a microstrip line having a length of 1/4, that is, λ / 4, and a resistance of approximately 50 Ω of a first frequency reception wavelength λ of the first band, and one end of the coupling capacitor ( An inductor L5 connected to the output terminal of the low pass filter 22-1 of the duplexer through CC1) and the other end connected to the first band receiving input terminal of the RF circuit unit through a coupling capacitor CC2, and the inductor L5. A first diode D1 connected to a cathode terminal at one end of the first terminal and connected to the first band transmission output terminal of an RF circuit unit (not shown) through a coupling capacitor CC3 and the inductor L5. A cathode is connected to the intermediate terminal of the capacitor CC2 and the anode terminal of the second diode D2 grounded through the capacitor C6 and the second diode D2 for switching the second diode D2. First switching voltage Vc1 connected to the anode terminal via resistor R1 And a.

In addition, the second switching circuit part 24 is formed of a microstrip line having a length of 1/4, that is, λ / 4, and a resistance of approximately 50 Ω of the reception frequency wavelength λ of the second band, and one end of the coupling capacitor ( An inductor L7 connected to the output terminal of the high pass filter 22-2 of the duplexer through the CC4) and the other end connected to the second band receiving input terminal of the RF circuit unit through a coupling capacitor CC5, and the inductor L7. A third diode D3 connected to a cathode terminal at one end of the terminal and an anode terminal connected to a second band transmission output terminal of an RF circuit unit (not shown) through a coupling capacitor CC6 and the inductor L7. A cathode is connected to the intermediate terminal of the capacitor CC5, and the anode terminal of the fourth diode D4, which is grounded through the capacitor C7, and the fourth diode D4 for switching the fourth diode D4. The second switching voltage Vc2 connected to the anode terminal via the resistor R2 is applied. Equipped.

Hereinafter, with reference to the accompanying drawings the operation and effect of the dual-band high-frequency switch according to the present invention will be described in detail.

Figure 4 shows the equivalent circuit diagram of Figure 3 in the transmission mode of the first band, the equivalent circuit of the dual band high frequency switch in the transmission operation in the first band according to the present invention is the first switching voltage of FIG. It is an equivalent circuit diagram when the first and second diodes are both turned on when the voltage is high and the second switching voltage is low. That is, in the transmission mode of the first band, when both the first and second diodes D1 and D2 are turned on as the first switching voltage becomes high, the first band has a frequency band of about 900 MHz as in the GSM terminal. An antenna ANT is transmitted through the low pass filter 22-1 and the low pass filter 21 of the duplexer 22 via the coupling capacitor CC1 through the first switching unit 23 through the first switching unit 23. Is output.

FIG. 5 shows the equivalent circuit diagram of FIG. 3 in the transmission mode of the second band, and as an example of the second band according to the present invention, DECT, PCS, DCS1800 (TX: 1.71 to 1.785 GHz, RX: 1.805 to 1.88 GHz). As described above, the equivalent circuit of the dual band high frequency switch in the transmission operation in the frequency band of about 1.8 GHz has the first switching voltage is low and the second switching voltage is high, that is, the first and second diodes D1 ( D2) is off and the third and fourth diodes D3 and D4 are turned on. In other words, when the third and fourth diodes D3 and D4 become conductive as the second switching voltage becomes high in the transmission mode of the second band, the transmission signal of the second band may cause the second switching circuit unit 24 to fail. The high pass filter 22-2 and the low pass filter 21 of the coupling capacitor CC4 and the duplexer are output to the antenna ANT.

4 and 5, in the dual band high frequency switch according to the present invention, the second and fourth diodes D2 and D4 are generated when the first band and the second band are transmitted. The parasitic inductor component is removed by LC series resonance to achieve an ideal short at the receiving end. Therefore, the insulation characteristic, which was about 20 dB in the first band transmission operation, can be improved to about 29 dB, and the conventional 16 dB in the second band transmission operation can be improved to about 25 dB or more.

6 shows the equivalent circuit diagram of FIG. 3 in the reception operation according to the present invention. In the reception operation, the mode first switching voltage and the second switching voltage are low level in the first band and the second band. All of the first to fourth diodes D1 to D4 are turned off. Thus, for example, in the case of the reception operation of the first band, the first band frequency signal received through the antenna ANT includes a low pass filter 21, a low pass filter 22-1 of the duplexer 22, and a coupling capacitor ( CC1) and the inductor L5 are input to the receiving input terminal of the first band RF circuit portion. The same is true for the reception operation of the second band.

In the case of the reception operation of the first band and the second band, as the first and second switching voltages become low, all of the first to fourth diodes D1 to D4 should ideally operate open. Since parasitic capacitors exist in the diode, it is better to select a diode with less parasitic capacitor when the diode is turned off to reduce the insertion loss.

The dual band high frequency switch according to the present invention is not limited to the above-described embodiment, and may be variously modified and implemented within the range allowed by the technical idea of the present invention.

As described above, the dual band high frequency switch according to the present invention is an LC series in a case where a diode is connected by connecting a capacitor in series with a diode formed at a receiving signal input terminal in a dual band high frequency switch used in a mobile terminal. The resonance is generated to remove the parasitic inductor component generated when the diode conducts. Therefore, the insulation characteristic is prevented from being deteriorated due to the parasitic inductor component generated by the conduction of the diode of the receiver during the transmission operation, thereby improving the insulation characteristics as compared with the conventional art.

Claims (3)

In the dual band high frequency switch, A low pass filter connected to the antenna to pass frequency signals in the first band and the second band; A duplexer configured to pass the received signal input through the low pass filter into one band and a second band according to the frequency band and to output the transmission signal output from the first band and the second band to the low pass filter, respectively; , A first switching circuit unit for selectively switching a reception signal and a transmission signal of a first band according to a first switching voltage to input / output an antenna through the duplexer; And a second switching circuit unit configured to selectively switch the reception signal and the transmission signal of the second band according to a second switching voltage to input / output through the duplexer. The method of claim 1, The first switching circuit part is formed of a microstrip line having a length of 1/4 of a reception frequency wavelength λ of a first band and a resistance of a predetermined value and one end of the low pass filter of the duplexer through the coupling capacitor CC1. An inductor L5 connected to the output terminal and the other end connected to the first band receiving input terminal of the RF circuit unit through a coupling capacitor CC2; A first diode D1 having a cathode end connected to one end of the inductor L5 and an anode end thereof connected to a first band transmission output end of the RF circuit unit through a coupling capacitor CC3; A second diode D2 grounded via a capacitor C6 and a cathode connected to an intermediate end of the inductor L5 and the coupling capacitor CC2; A dual band high frequency switch comprising a first switching voltage Vc1 connected to the anode terminal of the second diode D2 via a resistor R1 to switch the second diode D2. . The method of claim 1, The second switching circuit part is formed of a microstrip line having a length of 1/4, that is, λ / 4, and a resistance of a predetermined value of the reception frequency wavelength λ of the second band, and one end of the second switching circuit part is coupled to the coupling capacitor CC4. An inductor L7 connected to the output terminal of the high pass filter of the duplexer and the other end connected to the second band receiving input terminal of the RF circuit unit through a coupling capacitor CC5; A third diode D3 having a cathode end connected to one end of the inductor L7 and an anode end thereof connected to a second band transmission output end of the RF circuit unit through a coupling capacitor CC6; A fourth diode D4 having a cathode connected to an intermediate end of the inductor L7 and the coupling capacitor CC5 and the anode end of which is grounded through a capacitor C7; A dual band high frequency switch comprising a second switching voltage Vc2 connected to the anode terminal of the fourth diode D4 via a resistor R2 to switch the fourth diode D4. .