JPH052005B2 - - 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,
Amplify signals in the VHF band and UHF band. 20
3 and 204 are switching diodes, which are connected in series to the drains (or collectors) of the FET (or bipolar) transistors in the high-frequency amplifiers 201 and 202 upstream, and are used to supply each high-frequency amplified signal to the subsequent stage. Turning the supply on and off. Reference numerals 205 and 206 are chain coils, and switching diodes 203 and 2, respectively.
of high frequency amplifiers 201 and 202 via
Connected to the drain (or collector) of a FET (or bipolar) transistor. 2
C and 2D are the respective power supply terminals. For example, when receiving VHF, terminal 2C is at high level and terminal 2D is at low level, and when receiving UHF, terminal 2D is at high level and terminal 2C is at low level. Becomes a 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. 208 and 209 indicate stray capacitances 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.
High frequency amplifier 201, switching diode 2
03, the signal path supplied from the chiyoke coil 205 and the terminal 2A is 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 (here, the UHF band), contrary to the above case, the terminal 2
D is set to high level, terminal 2C is set to low level power supply voltage, and the signal of the UHF band system is amplified.
The signal is supplied to the next stage through terminal 2E.

(For example, see Japanese Patent Application Laid-Open No. 59-36431.) 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, it is difficult to solve the problem compared to a single system amplifier. The problem was that the stray capacitance doubled and the gain in the high frequency UHF band deteriorated 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 connects the drains or collectors of elements used in two high frequency amplifiers that amplify different bands via a switch diode. Signals in a low frequency band are connected to the power supply via a chiyork coil, and signals in a high frequency band are connected to the power supply through a coupling coil and chiyork coil whose ends are connected by a damping resistor. The intersection point and the intersection point between the switch diode and the switch diode in a low frequency band are coupled by a coupling capacitance, and a signal is extracted from the intersection point between the coupling coil and the switch diode. Here, for signals in a low frequency band, a peaking circuit whose resonance frequency due to the coupling capacitance and coupling coil is within that band is used, and for signals in a high band, the coupling coil becomes a chiyoke coil, and the low frequency band path becomes a peaking circuit. The structure should be designed to reduce the influence of stray capacitance that exists in .

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. 10 in Figure 1
1 and 102 are high frequency amplifiers using FET (or bipolar) transistors, 103 and 104 are switching diodes connected to their respective drains (or collectors), and 105 and 106.
are the respective switching diodes 103,1
04 and the power supply terminal, a coupling capacitance 107, stray capacitances 108 and 109 existing in the circuit, 110 coupling inductance,
111 is a damping resistor. 1A is the input terminal for the signal of the first low frequency band (here, VHF band), 1B is the input terminal for the signal of the second high frequency band (here, UHF band), and 1C is the input terminal for the signal of the second band of high frequency (here, the 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. The intersection of the switching diode 103 and the switch coil 105 is connected to the terminal on the side opposite to the power supply of the switch coil 106 via a coupling capacitor 107, and the switching diode 104 is connected from the intersection via a coupling coil 110 with damping resistors connected to both ends. It is connected to the. 108,1
09 is a stray capacitance existing in the circuit 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, the FET is usually constructed using a bipolar transistor, the drain (or collector) of which is connected to a chain coil 105 via a switching diode 103. When power supply terminal 1C becomes high level, current flows through this system.
VHF signal is amplified and switch diode 10
A VHF signal is output at the intersection of the coil 105 and the coil 105. This signal is supplied to the next stage from the output terminal 1E via a coupling capacitor 107 and a coupling coil 110 having damping resistors 111 connected to both ends thereof. At this time, by selecting the resonance frequency of the series resonant circuit consisting of the coupling capacitor 107 and the coupling coil 110 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 the terminal 1D is at a low level, the switch diode 104 is reverse biased, and the signal attenuation at the output terminal 1E is due to the stray capacitance 1.
Attenuation occurs due to the parallel capacitance of 08 and 109, but since the capacitance value 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 108 is The influence of the capacitance 108 can be extremely reduced.

By using a 22 pF capacitor as the coupling capacitor 107, a 7-turn coil with a diameter of 3 mm as the coupling coil 110, and a 2.2 kΩ resistor 111, the gain in the UHF band (470 to 770 MHz) 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 an inductance and a capacitance that are set to act as an inductor, it is possible to simultaneously improve the gain in the high frequency band without losing the gain in the low frequency band. It is possible.

[Brief explanation of the drawing]

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...damping resistance.

Claims (1)

[Claims] 1 Each FET (or bipolar) that amplifies two systems of signals with different frequency bands
Signals in a low frequency band are connected to the power supply terminal from the drain (or collector) of the transistor through a switching diode and a chain coil, and signals in a high frequency band are connected to a power supply terminal via a switching diode, a coupling coil, and a chain coil. The coupling coil is connected to the power supply terminal, and the intersection of the switching diode and the coupling coil in the low frequency band signal route is connected to the intersection of the coupling coil and the coupling coil in the high frequency signal route via a coupling capacitor. A damping resistor is inserted and connected between both ends of the , so that the output signal is taken out from the intersection of the switching diode of the high frequency signal path and the coupling coil, and the series resonance formed by the coupling coil and the coupling capacitance is A high frequency amplification device characterized in that the resonant frequency of the circuit is selected within a low frequency band.