JPH0342804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high frequency amplification device used in television receivers and the like.

BACKGROUND ART In recent years, with the development of the CATU band, an increasing number of high-frequency amplification devices are used in two or more frequency bands.

An example of a conventional high frequency amplification device will be described below with reference to the drawings.

FIG. 2 shows a conventional high frequency amplification device. In FIG. 2, 2A and 2B are input terminals for different bands. 201 and 202 are high frequency amplifiers, each with a different band (here VHF
band, UHF band) signal. 203,
A switching diode 204 is connected in series to the drains (or collectors) of the FET (or bipolar) transistors in the high frequency amplifiers 201 and 202 for high frequency amplification.

The supply of each signal to the subsequent stage is turned on/off. 205 and 206 are Chiyoke coils,
Switching diodes 203 and 204 respectively
It is connected to the drains (or collectors) of FET (or bipara) transistors of the high frequency amplifiers 201 and 202 via. 2C, 2D
are the respective power supply terminals, for example
When receiving VHF, terminal 2C becomes high level and terminal 2D becomes low level, and when receiving UHF, conversely, terminal 2D becomes high level and terminal 2C becomes low level. 207 is a coupling capacitor, which supplies one signal selected from among the signals of different bands as described above to the next stage from the output terminal 2E. 20
8,209 indicates stray capacitance existing in the circuit.

The operation of the high frequency amplification device configured as described above will be explained below.

First, when receiving the first band (here, the VHF band), terminal 2C is set to a high level power supply voltage and terminal 2D is set to a low level power supply voltage.
The high frequency amplifier 201, the switching diode 203, the choke coil 205, and the signal path supplied from the terminal 2A are turned on, and the signal path supplied from the terminal 2B is turned off. This results in
Only the VHF band signal is amplified, and the coupling capacity is 7
The signal is supplied from the terminal 2E to the next stage via the terminal 2E. At this time, the switching diode 204 becomes reverse biased to prevent the VHF band signal from being attenuated.
When receiving the second band (UHF band), contrary to the above case, terminal 2D is set to a high level power supply voltage, terminal 2C is set to a low level power supply voltage,
The signal of the UHF band system is amplified, and the terminal 2E
It is then supplied to the next stage. (For example, JP-A-59-
(Refer to Publication No. 36431) Problems to be Solved by the Invention However, in the above configuration, when the stray capacitances 208 and 209 are about 0.5 to 1 PF, the stray capacitance is twice that of a single amplifier system. ,
There was a problem that the gain in the high frequency UEF band was degraded by 3 to 4 dB.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a device that can switch signals in two bands and combine them into a single path without causing gain deterioration in high frequency bands. be.

Means for Solving the Problems In order to solve the above problems, the high frequency amplification device of the present invention uses FET (or biparallel) used in two high frequency amplifiers that amplify different bands.
The drain (or collector) of the transistor is connected to the power supply via a switching diode and a choke coil for signals in a low frequency band, and connected to the power source via a switching diode, a coupling coil, and a choke coil for signals in a high frequency band. , the intersection of the coupling coil and the switching diode is coupled to the intersection of the switching diode in the low frequency band signal path and the coupling capacitance (or the coupling capacitance and series resistance), and the coupling coil and the switching diode are connected to each other. The signal is extracted from the intersection of . Here, for signals in a low frequency band, the resonance frequency of the coupling capacitance and coupling coil becomes a peaking circuit within that band, and for signals in a high band, the coupling coil becomes a peaking coil, and the coupling coil becomes a peaking circuit in the low frequency band path. Create a configuration that reduces the effects of existing stray capacitance.

Effects The present invention has the above-described configuration, and when trying to receive a high frequency band, the influence of stray capacitance generated in the low frequency band path or chiyoke coil, which conventionally causes gain deterioration, is achieved. can be reduced by the coupling coil, and deterioration in gain when receiving signals in a high frequency band can be reduced.

Embodiment Hereinafter, a high frequency amplification device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit of a high frequency amplification device according to an embodiment of the present invention. In Figure 1, 10
1 and 102 are high frequency amplification devices using FET (or bipara) transistors 103 and 104 are switching diodes connected to their respective drains (or collectors), 105 and 106
are the respective switching diodes 103,1
04 and a power supply terminal; 107 is a coupling capacitance; 108 and 109 are stray capacitances existing in the circuit; 110 is a coupling inductance; and 111 is a damping resistor. 1A is the input terminal for the signal in the first band of low frequency (here, VHF band), 1B is the input terminal for the signal in the second band of high frequency (here, UHF band), and 1C is the input terminal for the signal in the second band of high frequency (here, UHF band).
A power supply (VHF power) terminal that has a high level when receiving the VHF band and a low level when receiving the UHF band,
1D becomes low level when receiving UHF band and VHF
Power supply that becomes high level when receiving band (UHF power supply)
Terminal 1E is a signal output terminal.

A VHF band signal is amplified through a system in which a high frequency amplifier 101, a switching diode 103, and a choke coil 105 are connected in series. The UHF band signal is transmitted to a high frequency amplifier 102,
The signal is amplified through a system in which a switching diode 104 and a choke coil 106 are connected in series. A coupling capacitor 107 and a resistor 1 are connected from the intersection of the switching diode 103 and the choke coil 105.
11 to the terminal opposite to the power source of the chiyoke coil 106, and from the intersection point the coupling coil 1
10 to a switching diode 104. 108 and 109 are stray capacitances existing in the circuits of each path.

The operation of the high frequency amplification device configured as described above will be explained using FIG. 1.

First, a VHF band signal is supplied to the high frequency amplifier 101 from the terminal 1A. High frequency amplifier 10
1 is constructed using a FET or a bipolar transistor, and its drain (or collector) is connected to a chain coil 105 via a switching diode 103. When power terminal 1C becomes high level, current flows through this circuit and VHF
The signal is amplified and the switching diode 103
A VHF signal is output at the intersection between the signal and the chiyoke coil 105. This signal is transmitted to the output terminal 1 via a coupling capacitor 107, a resistor 111, and a coupling coil 110.
E is supplied to the next stage. At this time, by selecting the resonant frequency of the series resonant circuit consisting of the coupling coil 107, the coupling coil 110, and the resistor 111 within the VHF band, the signal in the VHF band can be supplied to the next stage from the terminal 1E without attenuation. .

At this time, since terminal 1D is at a low level, switching diode 104 is reverse biased, and the signal attenuation at output terminal 1E is due to the parallel capacitance of stray capacitances 108 and 109, but the capacitance value is Since it is small and the frequency is low in the VHF band, the amount of attenuation due to the parallel capacitance is not a problem.

On the other hand, when receiving UHF band signals,
Since the power supply terminal 1D is at a high level and the terminal 1C is at a low level, the high frequency amplifier 102, the switching diode 104 and the choke coil 106
A current flows through the switch diode 104 and the switch coil 1, and the UHF band signal is amplified.
It is output at the intersection with 06. In this case, the UHF band signal is affected by the stray capacitance 109, but since the inductance of the coupling coil 110 is sufficiently large for the UHF band signal, the stray capacitance 108 is cut off from the signal path, and the stray capacitance is 1
The influence of 08 can be extremely reduced.

By using a 22PF capacitor as the coupling capacitor 107, a 7-turn coil with a diameter of 3 mm as the coupling coil 110, and a 2.2KΩ resistor 111, the gain in the UHF band (470 to 770MHz) can be improved by 3 to 4 dB. was completed.

In particular, the improvement effect was large when coupling by high impedance.

Although the above embodiments have been described for the VHF/UHF band, the present invention can also be applied to the VHF/UHF band.
This can be implemented for an amplifier circuit for two or more bands with a large difference in frequency.

Effects of the Invention As described above, according to the present invention, a series resonant circuit is configured for a low frequency band (such as the VHF band), and a chiyoke coil is configured for a high frequency band (such as the UHF band). By inserting and connecting a series circuit of inductance and capacitance that are set to work, it is possible to simultaneously improve the gain in the high frequency band without losing the gain in the low frequency band. It is something.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a high frequency amplification device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional high frequency amplification device. 101,102...High frequency amplifier, 103,1
04...Switching diode, 105,10
6...Chiyoke coil, 107...Coupling capacitance, 1
10...Coupling coil, 111...Coupling resistance.

Claims (1)

[Claims] 1 From the drain (or collector) of each FET (or bipolar) transistor that amplifies two systems of signals with different frequency bands, the low frequency band signal is connected to the power supply terminal via a switching diode and a choke coil. The signal in the high frequency band is connected to the power supply terminal via the switching diode, the coupling coil, and the coupling coil, and the intersection of the switching diode and the coupling coil in the signal path in the low frequency band is connected to the coupling capacitor or coupling capacitor. and a resistor to the intersection of the high-frequency signal path's high-frequency signal path and the coupling coil, and the output signal is taken out from the intersection of the high-frequency signal path's switching diode and the coupling coil, and
A high frequency amplification device characterized in that the resonance frequency of the series resonant circuit constituted by the coupling coil and the coupling capacitance is selected within a low frequency band.