JPH1093303A - Antenna changeover switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the antenna changeover switch with a small size, a light weight at a low cost that has excellent isolation and insertion loss characteristics through the constitution in which a diode is directly connected to a ground terminal that is formed at an extended part of a ground conductor. SOLUTION: A ground electrode De of a diode D2 connected in parallel with a transmission line is connected to a ground conductor G for grounding purpose with the shortest length to eliminate or reduce an inductive component of a roundabout grounding circuit conductor P. That is, the grounding electrode De of the diode D2 is connected to a ground terminal G1 formed at an edge of a board S via a side face of the board from a ground conductor G. Furthermore, the ground terminal G1 is used in common for a shield case ground terminal. Or the effect is unchanged even when a half-through configuration is adopted for the ground terminal G1 so as to avoid a contact with other devices such as a shield case. Through the constitution above, the inductive component due to a roundabout grounding circuit conductor P is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna changeover switch used for mobile communication equipment and the like.

[0002]

2. Description of the Related Art Generally, an antenna changeover switch has a plurality of electric elements such as a plurality of diodes and a coil. With reference to the drawings, a conventional antenna switch for transmission and reception will be described. FIG. 3 is a plan view of an example of a conventional antenna switch, and FIG.
FIG. 3 is a circuit diagram of an example of an antenna changeover switch.
In the example shown in FIG. 3, the antenna changeover switch is a changeover switch using two diodes, and includes diodes D1, D2, coil L1, coil L2, and capacitor C1.
To C5 and a resistor R, which are mounted on the substrate S. On the back surface of the substrate S, a ground conductor G is formed.

The diode D1 is connected to the circuit conductor P of the transmission line.
It is connected in series above. The diode D2 is
The electrodes De are connected in parallel, that is, the anode side of the electrode De is connected to the circuit conductor P of the transmission line, and the cathode side is connected to the circuit conductor PG for grounding. In addition, capacitors C1, C
Reference numerals 3 and C4 denote DC bias cut capacitors, which are connected to the transmission terminal T1, the antenna terminal A1, and the reception terminal R1, respectively, and to the circuit conductor P of the transmission line. L1 is a high frequency signal choke coil and capacitor C2
Is a capacitor for short-circuiting a high-frequency signal, R is a resistance for current control, and is connected in parallel to the transmission line. Further, at the time of transmission, since the connection point between the coil L2 and the capacitor C4 is connected to the ground as short as possible, the coil L2 and the capacitor C5 are
It is designed to resonate at the transmission frequency. The coil L2 is connected in series on the circuit conductor P of the transmission line. The capacitor C5 is connected to the circuit conductor P of the transmission line and to the circuit conductor PG for grounding. The circuit conductor PG for grounding has a conductor pattern continuous with the ground terminal G1.

Next, the operation of the antenna switch will be described. At the time of transmission, a voltage is applied to the bias terminal V1, and a control current flows through the diodes D1 and D2. At this time, since the connection point between the coil L2 and the capacitor C4 is short-circuited to the ground, the coil L2 and the capacitor C5 are short-circuited.
Resonates, the impedance at the other end of the coil L2 viewed from the antenna terminal A1 becomes extremely high. Therefore, the transmission signal is not output to the reception terminal, and the transmission terminal T1
Is output to the antenna terminal A1.

On the other hand, during reception, no voltage is applied to the bias terminal V1, so that the diodes D1, D2
, No control current flows, and the impedance between the anode and cathode electrodes De of these diodes becomes high. For this reason, the reception signal from the antenna terminal A1 is output to the reception terminal R1 and not output to the transmission terminal T1.

[0006]

At a high frequency to which the present invention is applied, when a diode is mounted on a substrate S or the like, the circuit conductors P and PG of the diode become inductor components, the impedance increases, and the diode characteristic increases. Was causing deterioration. In particular, in the case of the diode D2 connected in parallel to the transmission line used in the antenna changeover switch and grounded, the isolation characteristic of the antenna changeover switch, that is, the attenuation from the antenna terminal A1 to the reception terminal R1 is sufficiently high. There is a problem that it cannot be obtained.

If the isolation characteristic deteriorates, the insertion loss at the time of transmission also deteriorates. Although a sufficient isolation can be obtained by using a plurality of diodes, there is a problem that the volume of the antenna change-over switch increases and the manufacturing cost increases due to an increase in the number of components.

In addition, the distance to the ground changes depending on the arrangement of the diodes, that is, the impedance changes due to the increase and decrease of the inductor component of the circuit conductor, and the isolation characteristics differ. For this reason, there is a problem in that there is a limitation on the method of laying out the circuit conductors P and the arrangement of the circuit components, which limits the degree of freedom of design, and also hinders downsizing, weight reduction, and cost reduction.

[0009] That is, an object of the present invention is to provide an antenna changeover switch which is small in size, lightweight and low in cost, and has excellent isolation characteristics and insertion loss characteristics.

[0010]

According to the present invention, a grounded electrode De of the diode is connected to the back surface of the substrate S as means for connecting the diode in parallel to the transmission line and keeping the characteristics of the grounded diode constant. Is directly connected to the ground conductor G (not shown) without passing through the circuit conductor PG, that is, a diode is directly connected to a ground terminal G1 extending from the ground conductor G. As an extension path, a through hole can be used to directly ground the ground conductor G on the back surface of the substrate S. According to the above, an antenna changeover switch which is small, lightweight, and inexpensive and has excellent isolation characteristics and insertion loss characteristics can be obtained.

[0011]

FIG. 1 shows a transmission and reception antenna switch according to the present invention. In the present invention, by connecting the grounded electrode De of the diode D2 connected in parallel to the transmission line to the grounding conductor G with the shortest length and grounding, the inductor component for the routing of the grounding circuit conductor P is provided. Can be removed or reduced.

As a first embodiment, as shown in FIG. 1, a ground electrode De of a diode D2 is connected from a ground conductor G to a ground terminal G1 formed on an edge of the substrate S via a side surface of the substrate S. . The ground terminal G1 was also used as a ground terminal for the shield case. Even if a half-through is used for the ground terminal G1 so as not to come into contact with the shield case, other elements, devices and the like, the effect remains unchanged.

As a second embodiment, as shown in FIG. 2, a ground terminal G1 is connected to the ground conductor G on the back surface from the front surface of the substrate S by using a through hole H at the shortest distance. Since the electrode is located above the through hole H, the inductor component corresponding to the routing of the circuit conductor P for grounding is removed, and the degree of freedom of the diode arrangement can be increased.

[0014]

【Example】

(Embodiment 1) As Embodiment 1 of the present invention, as shown in FIG. 1, a ground terminal for a shield case is also used as a ground terminal G1, and an electrode De on the ground side of a diode D2 is connected via a circuit conductor PG for ground. Directly to the ground terminal G1. As compared with the conventional example, the inductor component of the routing pattern of the circuit conductor PG for grounding could be reduced. Other elements such as capacitors and coils, their constants, and other structures are the same as in the related art.

At the time of transmission, that is, when a transmission signal is output from the transmission terminal T1 to the antenna terminal A1, which is one of the main characteristics of this antenna changeover switch, the isolation characteristic, that is, the characteristic of the antenna terminal A1 to the reception terminal R1. The attenuation was about 21 dB from about 20 dB in the conventional example in the frequency band of about 900 MHz, which was improved by about 1 dB as compared with the conventional example.

Further, when a voltage is applied to the diode D2 and a control current is flowing, the ground point of the coil L2 and the capacitor C4 is connected to the ground in the shortest distance, so that the insertion loss of the diode D2 is smaller than that of the prior art. The reduction in the inductor component has been improved. As a result, the resonance peak of the coil L2 and the capacitor C5 and the impedance in the vicinity of the resonance peak are increased, so that the insertion loss at the time of transmission is also improved. In this embodiment, the transmission terminal T1 is connected to the antenna terminal A1.
From about 0.30 dB of the conventional example to about 0.28 dB.
B, which is about 0.02 dB improved as compared with the conventional example. Further, the insertion loss characteristics and the isolation characteristics were also improved during reception without applying a voltage.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIG. Electrode D on the ground side of diode D2
e is connected to the ground conductor G on the back surface of the substrate S via the through hole H without passing through the circuit conductor PG, and the diode D2
Could be connected to the ground conductor G with the shortest length. Since the connection terminal G1 is directly connected from the front surface of the printed circuit board S to the ground conductor G on the back surface by the through hole H, the through hole H is connected to the diode D
By forming it directly under the electrode De on the ground side of No. 2, it was possible to completely remove the inductor component in the routing of the circuit conductor P for grounding.

In the second embodiment of the present invention, the isolation characteristic at the time of transmission, that is, the attenuation from the antenna terminal A1 to the reception terminal R1 is about 20 dB to about 22 dB of the conventional example.
This is about 2 dB improved as compared with the conventional example. Also,
Also at the time of transmission, the insertion loss from the terminal T1 to the antenna terminal A1 is reduced from about 0.30 dB in the conventional example to about 0.26 dB, and is improved by about 0.04 dB as compared with the conventional example. Furthermore, by using the through hole H, the diode D2
Can be freely changed, and the empty space of the switch circuit can be utilized.

In the second embodiment, the capacitor C shown in FIG.
By using the empty space between 4 and C5, the substrate can be changed from the conventional (see FIG. 3) (vertical × horizontal) = 11 mm × 13 mm.
2 could be reduced to 11 mm × 12 mm.
About 10% reduction in area was achieved.

[0020]

According to the present invention, it is possible to obtain a small and lightweight antenna changeover switch having excellent isolation characteristics and insertion loss characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of an antenna switch according to a first embodiment of the present invention.

FIG. 2 is a plan view of an antenna switch according to a second embodiment of the present invention.

FIG. 3 is a plan view of an example of a conventional antenna switch.

FIG. 4 is an equivalent circuit diagram of an example of a conventional antenna changeover switch.

[Explanation of symbols]

 D1, D2 Diode De electrode L1, L2 Coil C1 to C5 Capacitor R Resistance S Substrate P Circuit conductor PG Grounding circuit conductor T1 Transmit terminal A1 Antenna terminal R1 Receive terminal V1 Bias terminal G1 Ground terminal H Through hole

Claims (3)

[Claims] 1. An antenna switch having at least one diode, wherein a ground conductor is formed on a back surface of the substrate, and an electric switch is provided on a surface of the substrate on which an electric element constituting the antenna switch is mounted. A circuit conductor for connecting the element and a ground terminal provided extending from the ground conductor are formed, and at least one electrode of the diode is directly connected to the ground terminal without passing through the circuit conductor. An antenna changeover switch characterized in that the antenna changeover switch is used. 2. An antenna changeover switch, wherein the ground terminal according to claim 1 is connected to a ground conductor formed on a back surface of the substrate through a through hole. 3. An antenna change-over switch, wherein the through-hole according to claim 2 is formed immediately below at least one electrode of the diode.