JPS6273821A - High frequency amplifier device - Google Patents

Abstract

PURPOSE:To attenuate the vicinity of frequencies higher than a desired frequency by inserting the 3rd inductance as a tuning coil in series with a varactor diode of a tuning type input filter. CONSTITUTION:An input signal is fed from a terminal 1A and the vicinity of the desired frequency is turned selectively by a tuning type input filter 11. In this case, two times or so of the desired signal frequency is attenuated by a tuning trap circuit 13 having the resonance point in the vicinity of twice the desired signal frequency and the result is amplified by a high frequency amplifier circuit 12 but the twice of the desired frequency is attenuated sufficiently. Thus, the constitution is simplified and the quantity of the secondary distortion is suppressed to a detection limit or below.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a high frequency amplification device used in CATV converters, Duplexes, etc.

BACKGROUND OF THE INVENTION In recent years, with the development of new media such as CATV and SHF, high frequency amplification devices are being used in a variety of applications.

Fig. 3, gi54, and Fig. 5 show conventional high frequency amplification devices, and in Fig. 3, 31 is a tuned input Jy filter;
2 is a high frequency amplification circuit. The high frequency signal input from input terminal 3△ is in IjJ tone! Select around the desired frequency using the 5° one-person filter and tune to JR. This signal is amplified by the high frequency amplifier circuit 32 and supplied to the next stage from the output terminal 3B.

FIG. 4 shows a specific example of the tunable input filter J1, ・1
1.42 is a tuning coil, 43.45 is a coupling capacitance, 44 is a variable capacitance diode, and 46 is a bias resistor for transmitting a tuning potential. 4A is the input terminal, /IQ is the output terminal, 4C
is the tuning potential terminal. The signal given from the input terminal 4A is sent to the tuning coil 41, 42 and the variable capacitance diode 44.
Resonant tuning is performed using the reverse bias capacitance of , and frequencies around the desired frequency are selectively passed. Input signal is tuning coil, 11.42
The resonance impedance can be increased by giving it from the inside.

A tuning potential is applied to the variable capacitance diode 44 from the terminal 4C via the bias resistor 4G. The tuned signal is supplied to the next stage high frequency amplification circuit 32 from the output terminal 4B via the coupling capacitor 45.

FIG. 5 shows a specific example of the high frequency amplification circuit 32, and 51 is an F
ETt-transistor, 52 is a bias resistor, 53 is a bias potential, 51 is a jog coil, and is connected between the train of the FET transistor 51 and the power supply terminal 5D. 55 is a coupling capacitor, 5B is a second gate terminal, 5C is an output terminal, and 5D is a power supply terminal.

The input signal is supplied to the first gate terminal 5A, is amplified by the transistor 51, and the amplified output is outputted from the output terminal 5C via the coupling capacitor 55. The second gate 1 terminal 5B functions as an AGC terminal that controls the gain of the transistor 51. (For example, JP-A-58-210
(Refer to No. 711) The problem that Komei is trying to solve With the conventional configuration like this, high frequency gain can be achieved, but when receiving signals with uniform levels on as many as 6 channels out of dozens of waves such as CATV, This is because the tuning characteristics of the input filter are insufficient and the signals that cause second- and third-order distortions cannot be dropped sufficiently, and even if the gain is reduced by the AGC voltage at the second gate terminal 5B, the multiwave type will hardly be improved. However, due to the combination of distortion caused by multiple waves, it was not possible to sufficiently eliminate interference. Among them, the difference between the desired frequency and the frequency twice the desired frequency falls within the band of the desired signal, and the difference between the second harmonic of the signal that is half the desired frequency and the frequency twice the desired signal falls within the band of the desired signal. There was a problem in that the interference level of the falling objects could not be sufficiently avoided.

An object of the present invention is to provide a high frequency amplification device that can reduce the above-mentioned interference.

Means for Solving the Problem The high frequency amplification device of the present invention includes a tunable input filter provided at the front stage of the high frequency amplification circuit, and the tunable input filter is connected to a first inductance, a second inductance, and a variable inductance. A high frequency input signal is supplied to the connection point of the first and second inductances on the right side of the parallel resonant circuit consisting of a capacitive diode,
A third inductance is inserted in series with the variable capacitance diode and the ground t81, and the third inductance is set at a frequency higher than the resonant frequency due to the reverse bias capacitance of the variable capacitance diode and the first, second, and third total inductances. The resonance point between the reverse bias capacitance of the variable capacitance diode and the reverse bias capacitance of the variable capacitance diode comes to J: Send the value of the third inductance to
The reverse bias potential applied to the variable capacitance diode can be varied by 8t using external means! J: Structure 1 - Characterize the thing.

According to the second configuration, the third inductance as a tuning coil is inserted in series with the variable capacitance diode of the Atal type input filter, so the series resonant circuit of the variable capacitance diode and the third inductance becomes a tuning trap circuit. Therefore, it is possible to attenuate the vicinity of frequencies higher than the desired frequency.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a configuration diagram of the high frequency amplification device of the present invention. 11
12 is a tunable input filter, 12 is a high frequency amplifier circuit, 13 is a tunable trap circuit, 1A is an input terminal, and 1B is an output terminal. FIG. 2 shows a specific example of the tuned input filter 11 and the tuned trap circuit 13 in FIG. 1, where 21.22 is a tuning coil, 23.25 is a coupling capacitance, 24 is a variable capacitance diode, and 27 is a tuning coil. It is. 2A is the input terminal, 2
B indicates an output terminal, and 2C indicates a tuning potential application terminal. In FIG. 1, an input signal is supplied from a terminal 1A, and a tunable input filter 11 selectively tunes around a desired frequency. At this time, the tuning trap circuit 13 having a resonance point near the desired signal frequency 21& is attenuated near the desired frequency 2&8, and the high frequency amplification circuit 12 is attenuated (j('1), Since twice the desired frequency is sufficiently attenuated (), the disturbance (J) appearing at the output terminal 11'3 is below the detection limit.

Figure 2 C' shows I right circular liquid filling signal is input terminal 2 A,)
, p, can be found at the midpoint of 21.22. The resonant circuit is resonant due to the tuning = Ile 21, 22, 27 and the reverse bias capacitance of the variable capacitance diode 24.
The wave number is determined, but the point at which the tuning signal is taken out is the coupling capacitance 1fi.
d5 at the intersection of the variable capacitance diode 23 and the variable capacitance diode 24, a series resonant circuit constituted by the variable capacitance diode 24 and the tuning coil 27 becomes the tuned trap circuit 13. This 1T
By selecting the resonance frequency of the IL key 1 to the wrap circuit 13 to be approximately twice the desired RJ wave number, the conventional problems can be completely reduced. The desired frequency tuned by 1!7 in this way is supplied from the output terminal 2B to the high p-wave, j-wave amplifier circuit 12 shown in FIG. 1 via the coupling capacitor 25.

In this way, the input signal is supplied to the inductance dividing point where the impedance becomes low in the tuning circuit, the impedance at the resonance point is increased, and the variable capacitor GUI-4-1 is used as a capacitor.
By inserting an ingetatance 27 in series with 24, the frequency twice the desired tuning frequency can be attenuated (
', Quadratic; Can you reduce f?

1) Column resonance of the first and second inductances that constitute the tuned input filter and the variable 8-hung die A-dobe. By inserting a third inductance in series with the variable capacitance diode of the circuit, the variable eight-hung diode and the third inductance act as a tuned one-wrap circuit. By attenuating frequencies around twice the desired frequency, it is possible to suppress the rise of second-order distortion generated in R to above the detection limit. .

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of Kibenmei's high frequency amplification device, Fig. 2 is a circuit diagram showing a specific example of the tunable input filter and tunable trap circuit of Fig. 1, and Fig. 3 is a circuit diagram of a conventional right circular FIG. 4 is a block diagram of a wave crest/trough device, FIG. 4 is a circuit diagram of a conventional tunable input filter, and FIG. 5 is a circuit diagram of a conventional high frequency J-width circuit. 11... Tunable input filter, 12... High frequency amplifier circuit, 13... Wrap circuit to tuning 1, 21.22...
・For tuning = j coil 1st and 2nd inductance), 2
4... Variable capacitance diode, 27... Tuning m:] Ile (third □' inductance) Agent Yahiro Morimoto Figure 1, ・'2 in Figure 2 Zl--pJQηm fill cyno I, Rishiotasis];
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Claims (1)

[Scope of Claims] 1. A tunable input filter is provided before the high-frequency amplifier circuit, and the tunable input filter is provided with a parallel resonant circuit including first and second inductances and a variable capacitance diode, and a first , a high frequency input signal is supplied to the connection point of the second inductance, a third inductance is inserted in series between the variable capacitance diode and the ground, and the reverse bias capacitance of the variable capacitance diode and the first, second, and third inductances are connected to each other. The value of the third inductance is set so that the resonance point between the third inductance and the reverse bias capacitance of the variable capacitance diode is at a frequency higher than the resonance frequency due to the total inductance of the variable capacitance diode, and A high frequency amplification device configured to vary the applied reverse bias potential. 2. The high frequency amplification device according to claim 1, wherein the resonance point of the variable capacitance diode and the third inductance is set at approximately twice the tuning frequency.