JPS6347015B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is an antenna in which a U/V mixed input antenna input can be connected without a duplexer using a changeover switch in an antenna terminal board having separate unbalanced input terminals for UHF and VHF. It is related to circuits.

Conventionally, in an antenna terminal board equipped with independent input terminals for UHF and VHF, when connecting a U/V mixed input antenna input, a U/V splitter 12 is installed near the terminal board 11 as shown in FIG. established,
It was split into UHF and VHF and connected to their respective terminals. However, it has drawbacks such as the installation work being troublesome.

The present invention improves this by providing an antenna circuit that eliminates the need for an external duplexer even in the case of U/V mixed input, and also enables connection to individual input terminals for individual UHF and VHF inputs. It provides: The present invention will be explained with reference to an embodiment shown in the figure below. 1 is a UHF input antenna terminal and U/
V mixed input antenna terminal, 2 is a VHF input antenna terminal. Insulating capacitors C ₁ and C ₂ are connected to the above antenna terminal 1, and the primary side of coupling loop 3 is connected to the capacitor C ₁ side. A UHF circuit Zo ₁ is connected to the secondary side via a connecting line 4. On the other hand, coupling capacitors C ₃ and C ₄ are connected to the antenna terminal 2 side, and inductances L _{2 and} C 4 are connected to the capacitor C ₃ side.
Connect L ₃ in series, connect capacitor C ₅ to the connection point of inductance L ₂ and L ₃ , and inductance
Inductance _L4 is connected to _L3 side via connection wire 5,
Connect the VHF circuit Zo ₂ . In addition, the above coupling loop 3
A switching diode _D1 is provided as a switching element connecting the two at one end of the primary side and the connection point between the capacitor _C3 and the inductance _L2 , and an inductance _L1 and a current limiting resistor R are provided on the anode side of the diode _D1 . ₁ and connect +B to the same resistor _R1 .
or -B voltage selection switch 6
A bypass capacitor _C6 is connected to the connection point between the inductance _L1 and the resistor _R1 .

In the above configuration, the coupling loop 3 is set so that the coupling loop length is approximately 1/4 wavelength with respect to the frequency near the center of the UHF band, as shown in FIG.
Furthermore, when the primary and secondary coupling loops are tightly coupled, the maximum amplitude of the standing wave appears at the tip of the open end because the primary side has an open end, and this relationship shows that the transmission path is If it is long enough, the conditions will be the same over the entire UHF band, resulting in a coupler with low transmission loss.

With the above configuration, first selector switch 6 is
When switched to the UHF side, that is, to the -B side, a reverse bias voltage is applied to the diode _D1 , and the diode _D1 is in a cut-off state. However
The UHF part and VHF part are separated. In this case, a UHF antenna and a VHF antenna can be connected to antenna terminals 1 and 2 independently, respectively. When a signal is input to the antenna terminal 1 on the UHF side, the coupling loop 3
The maximum output appears at the UHF output end.
Also, when a signal is input to antenna terminal 2 on the VHF side, inductance L ₂ , L ₃ and capacitor C ₅
The UHF component is attenuated by a low-pass filter called
The VHF component is transmitted to the VHF output end without attenuation.

Next, when the changeover switch 6 is switched to the VHF side, that is, the +B side, the diode _D1 is forward biased and turned on, and the UHF part and
The VHF part is in a coupled state. In this case, a U/V mixed input antenna can be connected to the antenna terminal 1 side. In other words, the equivalent circuit is as shown in Figure 2b, and when a UHF input signal is input to terminal 1,
The tip of the input side coupling loop 3 is connected to the above-mentioned low-pass filter, which is equivalent to an open state for UHF input, so the UHF input is transmitted without loss and the UHF output is Appears at the edge.
On the other hand, for VHF input signals, the UHF coupling loop 3 becomes part of the inductance of the low-pass filter,
The UHF signal is attenuated through a low-pass filter consisting of inductances L ₂ and L ₃ and capacitor C ₅ , and the VHF input is transmitted to the VHF output terminal.

As explained above, the switch elements are controlled by switching the changeover switch 6, whereby the antenna terminal 1 can be used both as a UHF input and as a U/V mixed input antenna terminal. Furthermore, since these are unbalanced inputs, they are easy to shield.
By accommodating the circuit configuration shown in FIG. 1 connected to the antenna terminals 1 and 2 in a shield case, it is possible to take measures against interference caused by direct waves. Note that the above switching element is not limited to the diode _D1 , and other switching elements may be used.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of an antenna circuit showing an embodiment of the present invention, FIG. 2 is an equivalent circuit for explaining the same,
FIG. 3 is an explanatory diagram of the coupling loop, and FIG. 4 is a front view of a conventional antenna terminal plate. In the figure, 1 is an antenna terminal, 2 is an antenna terminal, 3 is a coupling loop, 4, 5 are connection lines, C ₁ , C ₂ ,
C ₃ , C ₄ , and C ₅ are capacitors, L ₁ , L ₂ , L ₃ , and L ₄ are inductances, R ₁ is a resistor, and D ₁ is a diode.

Claims (1)

[Claims] 1. In an antenna circuit that has independent unbalanced input terminals for UHF and VHF, the UHF input terminal is coupled to one end of the primary coupling loop, and the secondary coupling loop coupled to the same coupling loop is
Combines the UHF circuit, while the VHF input terminal is connected to the VHF
Coupled to the circuit, approximately 1/4 of the center frequency of the UHF band
A switch element is connected to the other end of the primary side coupling loop consisting of a wavelength coupling circuit, and coupled to the VHF circuit via a low-pass filter that attenuates the UHF component, and the UHF signal and VHF signal are respectively transmitted from the antenna. When inputting to each of the input terminals, a reverse bias voltage is applied to the switch element to create a cut-off state, and the same UHF signal is sent to the UHF circuit, and the same VHF signal is input to the UHF circuit.
The signals are separately supplied to the VHF circuit, and the mixed UHF and VHF signals are sent from the same antenna to the VHF circuit.
By supplying forward bias voltage to the switch element when inputting through the UHF input terminal,
1. An antenna circuit characterized in that a VHF signal whose UHF signal component is attenuated by the filter from the mixed signal provided through the switch circuit is supplied to the VHF circuit.