JPS6367009A - Transmission circuit - Google Patents

Abstract

PURPOSE:To switch whether a filter characteristic exists or not, by connecting four coils to a shape of a lattice, setting electrical angles between adjacent contacts to 90 degrees, respectively, and connecting a series resonance circuit, and a PIN diode to a prescribed contact. CONSTITUTION:Four coils 21, 22, 23 and 24 are connected to a shape of a lattice, and capacitors 41, 42, 43 and 44 are connected between its four connecting points 31, 32, 33 and 34 and an earth, respectively. Also, two connecting points 31, 34 opposed to each other become an input terminal 31, and an output terminal 34, respectively, series resonance circuits 45, 5, and a PIN diode 6 are connected between the connecting point 32 and an earth, and between the connecting point 33 and an earth, respectively, and electrical angles between adjacent connecting points are set to 90 degrees, respectively. When the PIN diode 6 is turned on, it becomes a trap filter circuit, and when it is turned off, a line of the connecting points 31, 33 and 34 becomes a bypass circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission circuit that can be switched between having and not having filter characteristics as required.

[Conventional technology]

Figure 4 (A) shows an example of the so-called trap characteristic (band elimination characteristic) that attenuates a signal at a predetermined frequency f0. nation filter) is generally known.

[Purpose of the invention]

However, depending on the application, it may be necessary to switch between a state with the above-mentioned filter characteristics and a state where the signal is passed in a wide band without having the filter characteristics, for example, as shown in FIG. 4(B). be.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a transmission circuit that can be switched between having and not having filter characteristics as necessary.

〔Example〕

FIG. 1 is a diagram showing a transmission circuit according to an embodiment of the present invention. In this embodiment, four coils 21-2
4 are connected in a grid pattern, and capacitors 41 to 44 are connected between the four connection points 31 to 34 and ground, respectively. That is, the four transmission lines between adjacent connection points 31 to 34 are each realized by a π-type LC lumped constant circuit, and the electrical angle at each is set to 90 degrees.

In addition, in the above case, between each connection point 31 to 34 and the ground,
Originally, two capacitors would be connected in parallel, but in Figure 1 this is realized with one capacitor to reduce the number of parts.

By the way, Z is the desired characteristic impedance and electrical angle of each transmission line. , θ, the inductance I7 and capacitance C of the π-type LC circuit corresponding to the transmission line are, as is well known, ωL = Z. sinθ, given by.

On the other hand, two of the four connection points 31 to 34 facing each other, 31.34, are used as input and output ends, respectively, and one of the remaining two connection points 32.33 is connected to the ground. A series resonant circuit consisting of a capacitor 45 and a resonator 5 is connected, and P is connected between the other connection point 33 and ground.
An rN diode 6 is connected. The resonator 5 is made of, for example, a dielectric coaxial resonator. Note that the DC bias circuit for the PrN diode 6 is not shown.

In the transmission circuit as described above, the connection points 31 to 32
The line running from the connection point 31 to 34 works as a so-called trap filter (band elimination filter) circuit, and the line running from connection point 31 to 33 and reaching 34 works as a so-called bypass circuit.

That is, when the PrN diode 6 is on, the connection point 3
1 and 34 are each grounded via a line having an electrical angle of 90 degrees, so that the impedance when the line is viewed from both connection points 31 and 34 is close to infinity. Therefore, in this case, the connection points 31 to 32
34, and that line is a so-called trap filter circuit, so that the signal is attenuated at a predetermined frequency where series resonance occurs between the capacitor 45 and the resonator 5, and as a result, for example, as shown in FIG. Filter characteristics as shown in (A) are obtained.

On the other hand, when the PrN diode 6 is off, the connection point 3
Since the line from 1 to 34 via 33 acts as a bypass circuit for the filter circuit, it is possible to pass signals in a wide band, and as a result, for example, as shown in Fig. 4 (
Flat characteristics as shown in B) can be obtained.

In this way, in the above transmission circuit, the switching action of the PrN diode 6 allows switching between a state with filter characteristics and a state without filter characteristics.

Moreover, in the above transmission circuit, since the transmission line is isometrically realized by an LC lumped constant circuit, there is an advantage that the circuit can be made smaller. A specific example of the circuit configuration is shown in FIG. In the figure, 7 is a substrate, 8 is a ground electrode, 91 to 95 are connection lands, and capacitors 41 to 45 are chip-shaped.

Furthermore, since lumped constants are used in the above transmission circuit, there is an advantage that the degree of freedom in design can be increased.

FIG. 3 is a diagram showing a transmission circuit according to another embodiment of the invention. To explain the difference from the embodiment shown in FIG. 1, in this embodiment, the coil 2 is connected between the connection point 32 and the ground.
5 is further connected. In this way, the parallel resonance (anti-resonance) between the resonator 5 and the coil 25 further provides the effect that the pass loss in the desired pass band can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to switch between having and not having filter characteristics as necessary. Moreover, since the transmission line is realized by an LC lumped constant circuit, the circuit can be made smaller and the degree of freedom in design is increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a transmission circuit according to an embodiment of the present invention. 2 is a schematic plan view showing a specific example of the configuration of the transmission circuit shown in FIG. 1. FIG. FIG. 3 is a diagram showing a transmission circuit according to another embodiment of the invention. FIGS. 4(A) and 4(B) each show examples of transmission characteristics. 21-25...Coil, 31-34...Connection point, 4
1 to 45... Capacitor, 5... Resonator, 6...
PTN diode.

Claims (1)

[Claims] (1) Connect the four coils in a grid pattern, connect a capacitor between each of the four connection points and the ground, use two of the four connection points facing each other as input and output ends, and A transmission circuit characterized in that a series resonant circuit is connected between one of the two connection points and the ground, and a PIN diode is connected between the other of the two connection points and the ground, and the electrical angle between the adjacent connection points is 90 degrees. .