JPS645398Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a band switching amplifier that switches and amplifies a signal received by an antenna of a television common listening facility between a Haitian channel and a Low channel.

Conventionally, single-channel amplifiers with an amplification band for each channel have been generally used as preamplifiers used in receiving equipment for antenna received signals, and the receiving equipment must be equipped with a large number of preamplifiers. Nakatsuta.

Therefore, in order to reduce the number of preamplifiers, it is possible to use an all-channel wideband amplifier, but it is generally difficult to achieve both high output and low noise in a wideband amplifier, so it is not practical. It is desirable to use amplifiers that are divided into low channel (90 to 108 MHz) and high channel (170 to 222 MHz).

By the way, if the preamplifier is divided into two models, one for the low channel and the other for the high channel, making the preamplifier exclusively for the low channel and the high channel will tend to be complicated in terms of manufacturing and product management. It has been proposed to be able to select low channel and high channel channels using a switch, and if the filter is to be changed by a switch, it is necessary to install a changeover switch before and after the amplifier to change the filter. Therefore, a band switching amplifier as shown in FIG. 1 has been considered.

In Fig. 1, 1 is an input terminal, 2 is an amplifier section,
Reference numeral 3 designates an output terminal, and selector switches 4a, 4b are provided before and after the amplifying section 2, and high-pass filters 5a,
5b or low pass filters 6a, 6b in the amplifying section 2
It is configured so that it can be switched and connected to.

However, as shown in FIG. 1, when two changeover switches 4a and 4b are provided separately,
When installing an amplifier, it is easy to make a mistake in setting one of the switches by forgetting to switch it to the specified band side. Therefore, it is possible to increase the number of switch contact circuits to form a single changeover switch, but since the input and output are close to each other, adverse effects such as jumps and oscillations occur in the changeover switch, which deteriorates the characteristics. There was a problem.

The present invention was developed by focusing on these conventional problems, and it is possible to switch the band of a band-switching amplifier that amplifies television signals by switching between high channel and low channel without impairing the characteristics. In order to make this possible with a changeover switch, a changeover switch is provided to switch between a low-pass filter or a high-pass filter either before or after the amplification section, and each of the low-pass filter and high-pass filter on the side where the changeover switch is not installed is installed.
The purpose of the present invention is to solve the above problem by connecting the PIN diode in parallel to the amplifier section via a PIN diode, and supplying DC bias to the PIN diode on the band side corresponding to the switching position of the changeover switch to make it conductive.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

First, to explain the configuration, 1 is an input terminal, 2 is an amplification section, and 3 is an output terminal, a changeover switch 10 is provided between the input terminal 1 and the amplification section 2, and the changeover switch 10 is a changeover terminal a ₁ , a ₂ and b ₁ , b ₂ , with switching terminals a ₁ and a ₂
A high-pass filter 5a having high-channel passage characteristics (170 to 222 MHz) for television signals between
A low-pass filter 6a having low channel passage characteristics (90 to 108 MHz) for television signals is connected between switching terminals _b1 and _b2 .

Furthermore, a high-pass filter 5b and a low-pass filter 6b are connected in parallel between the amplifier section 2 and the output terminal 3 via PIN diodes 12 and 14, and the high-pass filter 5b and low pass filter 6
A diode switch circuit is formed to switch b.

On the other hand, the output side linked to the changeover switch 10
The input terminal 1 and the changeover switch 10 serve as a bias circuit to conduct the PIN diodes 12 and 14.
A DC bias voltage +DC is applied to the television signal through an inductance _L1 having a high impedance between the switching switches 10 and 10.
When switching to the high-pass filter 5a side, the PIN
As a circuit that applies DC bias to the diode 12, an inductance L ₂ and a resistor are connected from the switching terminal A ₁ side.
A circuit is provided to supply a DC bias voltage to the anode side of the PIN diode 12 via _R1 ,
Also, as a bias circuit for making the PIN diode 14 conductive when the changeover switch 10 is switched to the low-pass filter 6a side, a bias circuit is connected from the switching terminal _b1 side to the anode side of the PIN diode 14 via an inductance _L3 and a resistor _R2 . A bias circuit is provided.

Incidentally, each of the capacitors C ₁ , C ₃ , C ₄ , C ₇ to C ₁₁ is connected to the input terminal 1, the high-pass filters 5a, 5b,
These are DC cut capacitors that cut off the supply of DC bias voltage to the low-pass filters 6a and 6b, the amplifier 2, and the output terminal 3, and the capacitors C ₂ , C ₅ , and C ₆ are connected to the PIN diodes 12 and 14, respectively. This is a capacitor for stabilizing the supplied DC bias voltage, and each of the inductances L ₂ to _{L 4} is an inductance for blocking the passage of a television signal in the DC bias circuit.

Next, the effect will be explained.

First, when using the preamplifier for the Haiti channel, the changeover switch 10 is switched to the changeover terminals a ₁ and a ₂ as shown in the figure. By switching this switch, the high-pass filter 5a is connected between the input terminal 1 and the amplifier section 2, and the Haiti channel signal (170-222MHz) of the television reception signal from the TV antenna inputted from the input terminal 1 is sent to the amplifier section 2. Now you can input.

On the other hand, by switching the changeover switch 10 to the terminals a ₁ and a ₂ side, the DC bias voltage +Dc changes from the inductance L ₁ to the changeover switch 10 (switching contact a ₁
side) is supplied to the anode of the PIN diode 12 provided on the output side of the amplifier section 2 via the inductance L ₂ and the resistor R ₁ , and the DC bias current flows through the PIN diode 12 and the inductance L ₄ , so that the PIN diode 12 becomes conductive, and due to the conduction of PIN diode 12, the amplifier section 2 and output terminal 3
During this period, a high-pass filter 5b is connected via the PIN diode 12, and the high-channel signal amplified by the amplifier section 2 is applied to the output terminal 3 through the high-pass filter 5b.

Next, if the changeover switch 10 is switched to the changeover terminals b ₁ and b ₂ side, the low-pass filter 6b is connected between the input terminal 1 and the amplification section 2, and at the same time, the inductance L ₁ and the changeover switch (the changeover terminal b ₁ side ),
A DC bias voltage is supplied to the anode of the PIN diode 14 via the inductance L ₃ and the resistor R ₂ , and the PIN diode 14 and the inductance L ₅
When a DC bias current flows through the PIN diode 14, the PIN diode 14 becomes conductive, and the low-pass filter 6a of the changeover switch 10 is connected between the amplifier section 2 and the output terminal 3.
In response to switching to the side, the low-pass filter 6b
are connected by the conduction of the PIN diode 14, and the low channel signal (90 to 108 MHz) of the television signal applied to the input terminal 1 is amplified and output from the output terminal 3.

In this way, in the band switching amplifier of the present invention, the PIN diode corresponding to the switching position of the switching switch 10 is made conductive by supplying DC bias according to switching of the switching switch, and is connected to a high-pass filter or a low-pass filter corresponding to the selected band of the switching switch. Since the filter can now be automatically switched, and only one switch is required, there is no need to make mistakes in setting the amplifier when installing the amplifier. Since the amplification characteristics can be separated from each other, the amplification characteristics will not be deteriorated due to jumping or oscillation.

Incidentally, in the embodiment shown in FIG.
A diode switch 10 is provided on the output side of the amplification section 2, and a PIN
A diode switch using a diode is installed,
A direct current bias may be supplied to the corresponding band side PIN diode on the input side in conjunction with a changeover switch on the output side to make it conductive.

As explained above, according to the present invention, in a band switching amplifier that amplifies a television signal by switching the band between a high channel and a low channel, a low pass filter or a high pass filter is installed either before or after the amplification section. At the same time, the low-pass filter and high-pass filter on the side where the changeover switch is not installed are connected in parallel to the amplifier section via a PIN diode, and the PIN on the band side corresponding to the switching position of the changeover switch is provided. Since DC bias is supplied to the diode to make it conductive, the low-pass filter and high-pass filter installed before and after the amplifier can be switched with a single switch. This simplifies the switching structure, and also simplifies the setting when installing the amplifier, ensuring a highly reliable band that can reliably prevent setting errors that would otherwise occur if two switch switches were installed. Switching amplifiers can be put into practical use.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing an example of a conventional device proposed by the inventors of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Input terminal, 2...Amplification section, 3...Output terminal, 5a, 5b...High pass filter, 6a, 6
b...Low pass filter, 10...Selector switch, 12, 14...PIN diode, _C1 to _C11 ...
...Capacitor, _L1 to _L5 ...Inductance.

Claims (1)

[Claims for Utility Model Registration] In a band switching amplifier that amplifies a television signal by switching to a high channel band or a low channel band, either one between the input terminal and the amplifying section or the amplifying section and the output terminal. a change-over switch provided in the converter for connecting a high-pass filter or a low-pass filter, and a PIN diode connected in series to each of the high-pass filter and low-pass filter connected in parallel to the input side or output side of the amplifier section where the changeover switch is not installed. , and a bias circuit that supplies a DC bias to a PIN diode on the band side corresponding to the switching position of the changeover switch to make it conductive, and the PIN diode corresponding to the changeover position of the changeover switch applies a DC bias according to the changeover of the changeover switch. What is claimed is: 1. A band switching amplifier characterized in that the high pass filter or low pass filter corresponding to the selected band of the selector switch is automatically switched by being made conductive by supplying the same.