JPH08307101A - Antenna changeover rf switch - Google Patents

Abstract

PURPOSE: To secure suitable isolation by reducing an undesired inductance of a grounding position of a diode bypassing a high frequency signal to ground. CONSTITUTION: An RF switch is made up of a diode controlling transmission of a transmission signal to an antenna and a diode D3 forming a conduction path of a control current of the diode and bypassing a reception signal received by the antenna to ground in the case of transmission. A cathode terminal T1 of the diode D3 connects to ground being an ground electrode 52 formed a board rear side by a throughhole 6 provided to the inner side of the diode D3 from the connection position of the cathode terminal T1 of a printed circuit board 5 on which the RF switch is formed. A distance (d) between the throughhole 6 and the cathode terminal T1 is reduced as less as possible by providing the throughhole 6 in this position relation with respect to the cathode terminal T1 of the printed circuit board 5 thereby reducing an undesired inductance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna switching RF switch using a diode for sharing one antenna with a transmitting antenna and a receiving antenna, and more particularly to a diode for bypassing a high frequency to ground. It relates to a grounding structure.

[0002]

2. Description of the Related Art Conventionally, an antenna connected between an antenna input terminal and a filter for transmission and a filter for reception is switched to connect an antenna terminal to a filter for transmission and a filter for reception, and an antenna connected to the antenna terminal is used for transmission and reception. RF switches are known that use a diode to switch between the two.

FIG. 6 is a circuit diagram of an antenna duplexer using a conventional RF switch.

The antenna duplexer 100 shown in FIG. 1 is provided with an antenna switching RF switch 103 for switching the antenna ANT between transmission and reception between the antenna terminal ant and the transmission filter 101 and the reception filter 102. .

The RF switch 103 includes two diodes D10 and D20 which are PIN diodes, a λ / 4 phase circuit 104 which blocks a transmission signal, and a choke coil RF.
It is composed of C. The diodes D10 and D20 are switch circuits that control the connection between the antenna ANT and the transmission filter 101 and the reception filter 102, and are turned on / off by a control signal input from the control terminal CONT.
F (opening and closing) is controlled.

When a high level control signal is input to the control terminal CONT, the diodes D10, D20 and λ / 4 are input.
Forward current flows through the phase circuit 104, and the diode D1
0 and D20 are turned on, the transmission filter 101 and the antenna terminal ant are circuit-connected, and the transmission signal output from the transmission filter 101 is the diode D10.
And is guided to the antenna ANT via the capacitor C1,
It is radiated in the air.

On the other hand, when a low level control signal is input to the control terminal CONT, the diodes D10 and D20 are reverse biased, the diodes D10 and D20 are turned off, and the circuit between the transmission filter 101 and the antenna terminal ant is provided. Be shut off. Further, the output end of the λ / 4 phase circuit 104 is opened in a circuit manner, and the received signal transmitted through the λ / 4 phase circuit 104 is guided to the receiving filter 102 side.

As described above, the conventional RF switch 103
Is a diode D10 that controls the transmission of the transmission signal to the antenna ANT, and a conduction path for the control current of the diode D10. By bypassing the reception signal to the ground, the reception signal is transmitted to the receiving filter 102 side. It is composed of a diode D20 which controls transmission.

The diode D20 bypasses the received signal to the ground at the time of transmission to ensure isolation.
In component mounting, it is necessary to consider as much as possible so that unnecessary inductance does not occur at the grounding point, and the grounding of the cathode is usually connected to the ground electrode formed on the backside of the board using a through hole. There is.

FIG. 7 is a cross-sectional view of an essential part showing a method of grounding the diode D20 of the RF switch 103.

As shown in the figure, the cathode terminal 105 of the diode D20 is connected by soldering to an electrode 106 having a through hole 107 formed on the component mounting surface, and the back surface of the substrate is connected via this electrode 106 and the through hole 107. Of the earth electrode 108.

[0012]

[Problems to be Solved by the Invention] Conventional RF switch 1
In order to reduce unnecessary inductance, it is preferable that the distance D between the cathode terminal 105 and the through hole 107 of the diode D20 that bypasses the high frequency in 03 to the ground is as short as possible.
07 is provided outside the position where the cathode terminal 105 of the electrode 106 is placed by a predetermined dimension in order to prevent the solder flow into the through hole 107 during the soldering process of the cathode terminal 105 to the electrode 106. Therefore, the cathode terminal 105 and the through hole 10 must be
There is a certain limit to the reduction of the distance d between 7 and a limit to ensuring the isolation.

The present invention has been made in view of the above problems, and reduces an unnecessary inductance at a ground point of a diode that bypasses a high frequency to the ground, and can secure a suitable isolation. The purpose is to provide.

[0014]

According to the present invention, there is provided a first diode provided between a transmission terminal to which a transmission signal is input and an antenna terminal to which an antenna is connected, for controlling transmission of the transmission signal to the antenna. A switch member, a filter member that is provided between the antenna terminal and a reception terminal that outputs a reception signal received by the antenna, blocks a transmission signal from the transmission circuit, and transmits the reception signal to the reception terminal. Is provided between the output end of the filter means and the ground, constitutes a conduction path of a control current of the first diode switch member input from the transmission terminal, and the ON period of the first diode switch member is An RF switch circuit including a second diode switch member that bypasses the received signal to the ground is provided, and a ground electrode is formed on one surface. In the antenna switching RF switch mounted on the other surface of the printed circuit board, the cathode of the second diode switch member is located inside the second diode switch member from the connection position of the cathode of the printed circuit board. Is grounded to the ground electrode through a through hole provided in.

[0015]

According to the present invention, the through hole for connecting the cathode of the second diode switch member to the ground electrode formed on the back surface of the printed circuit board is
Since it is provided inside the second diode switch member from the connection position of the cathode, the cathode prevents the solder from flowing into the through hole during the soldering process of the cathode.

As a result, the distance between the cathode connection position of the second diode switch member and the through hole can be shortened as much as possible, unnecessary inductance at this ground position can be reduced, and suitable isolation can be ensured. become.

[0017]

1 is a circuit diagram of an embodiment of an antenna duplexer to which an antenna switching RF switch according to the present invention is applied.

The antenna duplexer 1 is used, for example, in a wireless communication device such as a car telephone, and is particularly applicable to a wireless device in which space diversity reception is performed by using two antennas.

The antenna duplexer 1 includes a transmission filter 2,
It is composed of a receiving filter 3 and an RF switch circuit 4 using a PIN diode. The antenna duplexer 1 has an antenna terminal ant to which the antenna ANT1 is connected.
1. Antenna terminal ant to which antenna ANT2 is connected
2. Tx terminal to which a transmitter circuit (not shown) is connected, Rx terminal to which a receiver circuit (not shown) is connected, the antenna ANT
1 and a control signal for controlling the connection between the receiving filter 3 and the first control terminal CONT1 to which a control signal for controlling the connection between the transmitting filter 2 and the antenna 1 is input. Second control terminal CONT
2 are provided.

Antenna ANT1 and antenna ANT2
Is an antenna provided for diversity reception, and the antenna ANT1 is also used as a transmission antenna.

The transmission filter 2 is a filter including an LPF (Low Pass Filter) for limiting the transmission signal from the transmission circuit input from the Tx terminal to a signal in a predetermined transmission band. Capacitor C3
It is composed of a ladder type circuit of C4 and C5. The capacitor C0 is a DC cutting capacitor.

The reception filter 3 is a filter such as a BPF (Band Pass Filter) for limiting the reception signal received by the antenna ANT1 or the antenna ANT2 to a signal in a predetermined reception band, and is, for example, an integrally molded dielectric filter. Composed.

The RF switch circuit 4 includes three diodes D1 to D3 (diode switch members) made of PIN diodes, two filter circuits 41 and 42 (filter members), two high frequency choke coils RFC1 and RFC.
2 and resistors R1 and R2, which are connected as follows.

That is, the anode (point a) of the diode D1 is connected to the output end of the transmission filter 2 and is also connected to the first control terminal CONT1 via the high frequency choke coil RFC1 and the resistor R1.
The cathode of No. 1 is connected to the input terminal (point b) of the filter circuit 41 and is also connected to the antenna terminal ant1 via the capacitor C1.

The output terminal of the filter circuit 41 (point c)
Is connected to the output end of the filter circuit 42, and a diode D3 is connected between this point c and ground.

The cathode of the diode D2 is connected to the input terminal (point d) of the filter circuit 42, the anode of the diode D2 is connected to the antenna terminal ant2 via the capacitor C2, and the high frequency choke coil RFC2 and the resistor are connected. The second control terminal CONT via R2
Connected to 2.

Incidentally, the diode D1 and the transmission filter 2
The connection point a with and corresponds to the transmission terminal of the RF switch circuit according to the present invention, and the connection point d between the diode D2 and the receiving filter 3 corresponds to the reception terminal of the RF switch circuit according to the present invention.

The filter circuit 41 blocks the transmission of the transmission signal output from the transmission filter 2 to the diode D3 side. In addition, the filter circuit 42 includes the antenna A
This is to prevent the reception signal received by NT2 from being transmitted to the diode D3 side.

The filter circuit 41 is, for example, an air-core coil L.
3 and the capacitors C6 and C6 'are formed in a π-type circuit,
The filter circuit 42 is also composed of a π-type circuit including an air-core coil L4 and capacitors C7 and C7 '. The circuit constants of the filter circuits 41 and 42 are set so that, when the diode D3 is in the ON state (short-circuited state), the impedance when the diode D3 side is seen from the input end becomes extremely large in the frequency band to be blocked.

The diode D1 is a switch circuit for controlling the connection between the antenna ANT1 and the transmission filter 2, and ON / OFF (opening / closing) is controlled by the control signal S1 input from the control terminal CONT1. The diode D2 is a switch circuit that controls the connection between the antenna ANT2 and the reception filter 3, and the control terminal CONT.
ON / OFF (opening / closing) is controlled by a control signal S2 input from 2. The diode D3 constitutes an energization path for flowing a control current (DC current) to turn on the diodes D1 and D2, and bypasses the transmission signal or the reception signal to the ground.

The capacitors C1 and C2 are coupling capacitors that cut the inflow of the control current to the antenna side and couple only high frequencies. The high frequency choke coil RFC1 prevents the transmission signal from flowing out to the control terminal CONT1, and the high frequency choke coil RFC2 controls the reception signal received by the antenna ANT2.
It prevents the outflow to the NT2 side.

The control signals S1 and S2 are high-level or low-level state signals, which are control signals S1 and S2.
The connection state of the antenna ANT1 and the antenna ANT2 is controlled as shown in Table 1 below according to the combination of the level states.

[0033]

[Table 1]

Here, the switching operation of the RF switch circuit 4 in each control mode of Table 1 will be briefly described.

(1) Control Mode 1 In the control mode 1, the diodes D1 and D3 are in the ON state (closed state), the diode D2 is reverse biased and OF
In the F state (open state), the transmission filter 2 and the antenna terminal ant1 are circuit-connected, and the transmission signal output from the transmission circuit through the transmission filter 2 is transmitted through the diode D1 and the capacitor C1 to the antenna ANT1. And is radiated into the air.

At this time, the transmission signal is the filter circuit 4
The signal received by the antenna ANT1 is bypassed to the ground through the filter circuit 41 and the diode D3 and is not transmitted to the receiving filter 3 side.

The circuit between the antenna terminal ant2 and the receiving filter 3 is cut off, and the received signal received by the antenna ANT2 is not transmitted to the receiving filter 3 side. Therefore, in the control mode 1, only the antenna ANT1 operates as a transmitting antenna.

(2) Control Mode 2 In the control mode 2, the diodes D2 and D3 are in the ON state (closed state), and the diode D1 is reverse-biased and OF
In the F state (open state), the transmission filter 2 and the antenna terminal ant1 are electrically cut off, and the transmission signal output from the transmission circuit via the transmission filter 2 is transmitted to the antenna A.
Not transmitted to NT1. On the other hand, the received signal received by the antenna ANT1 is the filter circuit 41 and the diode D3.
It is bypassed to the ground via the and is not transmitted to the receiving filter 3 side.

Further, the antenna terminal ant2 and the receiving filter 3 are connected in a circuit manner, and the reception signal received by the antenna ANT2 is transmitted to the receiving filter 3 side. At this time, the received signal is blocked by the filter circuit 42 and is not bypassed to the ground via the diode D3. Therefore, in the control mode 2, the antenna ANT2
Only acts as a receiving antenna.

(3) Control mode 3 In the control mode 3, all the diodes D1 to D3 are in the OFF state (open state), and between the transmission filter 2 and the antenna terminal ant1 and between the reception filter 3 and the antenna terminal ant.
The two are electrically cut off, the transmission signal output from the transmission filter 2 is not transmitted to the antenna ANT1, and the reception signal received by the antenna ANT2 is not transmitted to the reception filter 3.

On the other hand, the reception signal received by the antenna ANT1 is transmitted to the reception filter 3 via the filter circuits 41 and 42 without being bypassed to the ground via the diode D3. Therefore, in the control mode 3, only the antenna ANT1 operates as a receiving antenna.

FIG. 2 is a plan view showing a component mount of the antenna duplexer 1. This figure shows a state in which the circuit components of the antenna duplexer 1 shown in FIG. 1 are mounted on the mounting surface of the printed circuit board 5, and the same members as those shown in FIG. 1 are designated by the same reference numerals.

The antenna duplexer 1 shown in the figure is of a surface mounting type, and includes an Rx terminal, a Tx terminal and an antenna terminal ant.
1, ant2 and control terminals CONT1, CONT2 are
A concave portion is formed at a predetermined position on the side surface of the substrate, and an electrode (side electrode) is formed in this concave portion. Further, the mounting surface side of the printed circuit board 5 is shielded by a metallic case, and the rear surface side is a ground electrode 52 (see FIG. 4) on a portion of the rear surface of the printed circuit board 5 excluding the electrodes of the terminal portions. Is formed and shielded.

The stippled portion of the printed circuit board 5 shows an electrode pattern, and the ground electrode 51 on the mounting surface side is an electrode formed on the side surface of the printed circuit board 5 and the ground electrode 5 on the back surface side.
Connected to 2.

Further, as shown in FIG. 5, the receiving filter 3 is an integral molding type in which electrodes are formed on the outer and inner circumferences of a rectangular parallelepiped dielectric body having a pair of through holes 31 parallel to the axis. It is composed of a dielectric filter. Reception filter 3
Form an input / output electrode 32 that is capacitively coupled (corresponding to capacitors C8 and C9) on the side surface of the dielectric, and form the input / output electrode 32 and the ground electrode 33 formed on the side surface of the dielectric on the mounting surface of the printed circuit board 5. They are attached to the input and output electrodes and the ground electrode (not shown).

Next, the ground structure of the diode D3 for bypassing the high frequency of the RF switch 4 according to the present invention to the ground will be described.

FIG. 3 is a plan view of an essential part showing a mounting electrode pattern of the diode D3, and FIG. 4 is a sectional view taken along line AA of FIG.

The diode D3 has a horizontally long rectangular parallelepiped shape, and two L-shaped terminals T1 to T4 are respectively projected from both side surfaces in the longitudinal direction of the package. The terminals T1 and T4 are cathode terminals, and the terminals T2 and T3 are anode terminals, which are respectively connected to the cathode and anode of the diode D3 inside the package.

At the mounting positions of the anode terminals T2 and T3 on the mounting surface of the printed circuit board 5, connection electrodes 53 and
54 is formed, and the anode terminal T2 is connected to the coil L3 of the filter circuit 41 via the connection electrode 53,
The anode terminal T3 is connected to the coil L4 of the filter circuit 42 via the connection electrode 54. Further, a ground electrode 51 is extended at the mounting position of the cathode terminals T1, T4 on the mounting surface of the printed circuit board 5 to form a connection electrode for grounding, and the anode terminals T1, T4 are grounded via the ground electrode 51. The electrode 52 is connected.

The ground electrode 51 is connected to the ground electrode 52 on the back surface by the side electrode of the printed circuit board 5, and
The through hole 6 is provided in the vicinity of the inside of the diode D3 from the connection position of the cathode terminal T1 of the printed circuit board 5, and is provided in the vicinity of the outside of the diode D3 from the connection position of the cathode terminal T4 of the printed circuit board 5. It is connected to the ground electrode 52 by the through hole 6 '.

Since the diode D3 forms a bypass of the received signal to the ground as described above, the through holes 6 and 6'shorten the line length between the cathode of the diode D3 and the ground, and occur in this bypass line. This is to reduce unnecessary inductance as much as possible.

The through hole 6 is connected to the cathode terminal T1.
The through hole 6 and the cathode terminal T1 are provided in the vicinity of the inside of the diode D3 from the connection position of
This is because the distance d from the connection point can be minimized, and thus suitable isolation can be secured.

That is, when it is provided outside the diode D3, the solder unnecessarily flows into the through hole 6 in the soldering process of the cathode terminal T1 and the ground electrode 51 and flows out to the back surface side of the printed circuit board 5. Since the flatness of the back surface is deteriorated, in order to prevent this, the distance d between the through hole 6 and the connection point of the cathode terminal T1 needs to be a certain dimension or more. However, when the distance d is provided inside the diode D3, , The solder outside the cathode terminal T1 is prevented from flowing into the through hole 6 side by the cathode terminal T1, and the problem of the solder inflow into the through hole 6 is less than that in the case where the solder is provided outside the diode D3. This is because d can be made shorter.

Further, when the through hole 6 is provided inside the diode D3, the lower position of the package of the diode D3 on the printed circuit board 5 is effectively used, and the through hole 6 is provided outside the diode D3. In comparison, the dead space of the electrode pattern is also reduced.

In this embodiment, since the through hole 6 is provided inside the diode D3, the through hole 6'is provided outside the diode D3, but the through hole 6'is also provided in the diode D3. It is better to provide it inside.

As described above, since the through hole 6 is provided inside the diode D3 with respect to the connection position of the cathode terminal T1 and the distance d between the through hole 6 and the cathode terminal T1 is made as short as possible, the diode D3 is not connected. Unnecessary inductance at the cathode terminal T1 is reduced,
A desired isolation can be secured.

In the present embodiment, an antenna duplexer compatible with a radio device in which space diversity reception is performed using two antennas has been described as an example, but in FIG. 1, the antenna terminal ant2 and the second control terminal are used. CONT2,
If the circuits of the resistor R2, the high frequency choke coil RFC1 and the thyroid switch D2 are removed, it becomes a normal antenna duplexer that switches one antenna between the transmitting antenna and the receiving antenna.
The present invention can also be applied to the F switch.

In the above embodiment, the case where the present invention is applied to an antenna duplexer has been described, but the present invention can also be applied to an RF switch built-in radio device and an RF switch built-in antenna.

[0059]

As described above, according to the present invention,
A first diode switch member for controlling transmission of a transmission signal to the antenna and an energization path of a control current of the first diode switch member are formed, and the antenna is received during the ON period of the first diode switch member. In an antenna switching RF switch comprising a second diode switch member for bypassing the received signal thus received to the ground, the cathode of the second diode switch member is connected to the cathode of the printed circuit board on which the RF switch is connected. Further, since the ground electrode formed on the back surface of the printed circuit board is grounded by the through hole provided inside the second diode switch member, the connection position of the cathode of the second diode switch member and the through hole are formed. The distance between holes can be shortened as much as possible, Unnecessary inductance becomes possible to ensure a suitable isolation is reduced in.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of an antenna duplexer to which an antenna switching RF switch according to the present invention is applied.

FIG. 2 is a plan view showing a component mount of an antenna duplexer to which the antenna switching RF switch according to the present invention is applied.

FIG. 3 is a plan view of a principal part showing a mounting electrode pattern of a diode that bypasses a high frequency to ground.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a perspective view showing an integrally molded dielectric filter.

FIG. 6 is a circuit configuration diagram of an antenna duplexer using a conventional RF switch.

FIG. 7 is a cross-sectional view of an essential part showing a method of grounding a diode in which a high frequency of a conventional RF switch flows.

[Explanation of symbols]

 1 Antenna Duplexer 2 Transmission Filter 3 Reception Filter 4 RF Switch Circuit 41,42 Filter Circuit 5 Printed Circuit Board 51,52 Earth Electrode 53,54 Connection Electrode 6,6 'Through Hole ANT1, ANT2 Antenna ant1, ant2 Antenna Terminal CONT1 1st control terminal CONT2 2nd control terminal C0-C9 capacitor D1-D3 diode L1-L4 coil R1, R2 resistance T1, T4 cathode terminal T2, T3 anode terminal Rx, Tx transmission / reception terminal

Claims (1)

[Claims] 1. A first diode switch member provided between a transmission terminal for inputting a transmission signal and an antenna terminal to which an antenna is connected, for controlling transmission of the transmission signal to the antenna, and the antenna terminal. A filter member that is provided between reception terminals that output a reception signal received by the antenna, blocks a transmission signal from the transmission circuit, and transmits the reception signal to the reception terminal; and an output end of the filter means. It is provided between grounds and constitutes a conduction path for the control current of the first diode switch member that is input from the transmission terminal, and bypasses the received signal to ground during the ON period of the first diode switch member. RF comprising a second diode switch member
In an antenna switching RF switch in which a switch circuit is mounted on the other surface of a printed circuit board having a ground electrode formed on one surface thereof, the cathode of the second diode switch member has a connection position of the cathode of the printed circuit board. An antenna switching RF switch, characterized in that it is grounded to the ground electrode through a through hole provided inside the second diode switch member.