JPH03218124A - Antenna mixer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an antenna mixer adapted to the field of video equipment including VTRs. BACKGROUND ART FIG. 2 shows a circuit diagram of a conventional antenna mixer.

To simplify the explanation, only the signal transmission circuit and high-pass circuit will be shown. An external input signal input from the input terminal RF-IN is amplified by the transistor Q2, and one of the signals is outputted from the output terminal VTR-OUT by the distribution transformer T3. The other signal is combined with the output signal of the RF modulator 1 by the matching transformer T4 via the transistor Q3, and output to the output terminal RF-OUT.
It is output from This circuit has a 10B circuit that operates the transistor Q2 and a BS1 circuit that turns the transistor Q3 on and off.

The BS1 circuit sets OV and 12V to switch between TV mode and VTR mode.

A voltage inverting circuit transistor Q4 is added to the BS1 circuit, and the voltage BS2 applied to the anode part of the switching diode D3 and the voltage BS3 applied to the cathode part of the switching diode D3 are switched, and BS1=O/12.
At V, B S 2 =12/O V. When BS1=OV, BS2=12V, and the switching diode D3 is connected to the resistor R1 for TV mode setting.
The transistor Q3 is turned on via the input terminal RF-IN, and the transistor Q3 is activated, and the signal inputted from the input terminal RF-IN is outputted to the output terminal RF-OUT without loss.

On the other hand, when BS 1 = 12V, BS2 becomes OV,
Set to VTR mode. This means that the cathode voltage of switching diode D3 becomes 12V, and BS2 becomes Ov.
Therefore, the switching diode D3 is turned off and the transistor Q3 becomes inactive, the input signal from the input terminal RF-IN is attenuated, and the output signal from the RF modulator 1 is interfered with by the external input signal. I try not to.

Here, the reason why the input signal is attenuated when setting the VTR mode is as follows. This is to avoid interference such as beats from occurring in the vicinity of the output signal frequency (591.25±32 MHz) of the RF converter I in special areas, where there is an external interference signal near the output signal frequency (591.25±32 MHz) of the RF converter I. In other words, when transistor Q3 is inactive, the interelectrode capacitance of switching diode D3, capacitor C2, and coil L2
The parallel resonant trussop configuration according to the present invention provides a circuit configuration that satisfies attenuation characteristics of a minimum of 40 dB.

Problems to be Solved by the Invention However, with such a conventional circuit configuration, a complicated circuit configuration is required to obtain an attenuation characteristic of about 40 dB for the interference signal, which increases the cost and does not meet the current market requirements. It has become impossible to respond to this.

Means for Solving the Problem In order to solve this problem, the antenna mixer of the present invention has the following features:
An on/off circuit consisting of a switching diode is inserted in the signal transmission path from the antenna input terminal to the output terminal.
The feature is that an LC series resonant circuit is added to the switching diode. According to the present invention, by setting the resonant frequency of the LC series resonant circuit to the interference frequency, it is possible to ensure attenuation characteristics of the interference signal from the antenna input terminal to the output terminal at a minimum of 40 dB when the VTR mode is set. It is possible to significantly reduce the number of circuit elements and create an antenna mixer with a simple circuit configuration that has interference rejection capabilities equal to or better than conventional ones.
Its industrial value is extremely high.

Embodiment 1 The first embodiment is a circuit diagram of an antenna mixer showing an embodiment of the present invention, in which an input signal to the input terminal RF-IN is amplified by a transistor Q1 and applied to a distribution transformer Tl. The transistor Q1 becomes operational when a bias voltage of 12V is supplied to the 10B terminal. In the above distribution transformer TI, one of them is the output terminal VTR-O
Output to UT. The other signal is applied to the synthesis transformer T2 via the diode D1, and is combined with the output signal from the RF modulator 1 and output to the output terminal RF-OUT. A switching diode D2 is connected to the cathode of the diode D1, and the anode of the diode D2 is grounded via a series resonant circuit of a coil L1 and a capacitor C1. The switching diode D2 is turned on and off by a bias voltage applied to the PS terminal.

Now, when BS=12V, the VTR mode is set, the switching diode D2 is turned on via the resistor Rl, and the potential of the cathode example of the switching diode D1 is determined by the forward voltage of the switching diode D2 and the resistor R.
1 causes a decrease of 0.7V, resulting in a value of 11.3V. Further, the anode voltage of the switching diode D1 corresponds to the collector voltage of the transistor Ql, and the voltage is set to about 7V, so the switching diode DI is turned off.

By setting the resonance frequency of the series resonant circuit of the coil L1 and capacitor CI, which are configured in series with the switching diode D2, to the interference signal frequency, when the switching diode D2 is on, the interference signal is trapped by the series resonant circuit. .

Due to the off characteristics of the switching diode DI and the trap characteristics via the switching diode D2, the interference signal is attenuated by 40 dB or more, and the output signal of the RF modulator 1 is output without interference such as beats caused by the interference signal. , which corresponds to the characteristic contents explained in the conventional example.

Note that the coil L1 may be formed by a pattern on a printed circuit board.

On the other hand, when BS=OV, TV-E-}' occurs, and due to the reverse operation described above, the switching diode D1 is grounded through the resistor R1 and turns on, and the switching diode D2 becomes a reverse voltage and turns off. becomes. That is, the switching diode D1 is turned on and the switching diode D2 is turned off, and the input signal is output from the output terminal RF-OUT without loss.

Effects of the Invention As described above, according to the present invention, characteristics equivalent to those of the conventional example can be realized with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an antenna mixer according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional antenna mixer. Q1...Transistor, Tl, T2...
・Distribution coupling transformer, DI, D2... Switching diode, R1... Resistor, C1... Capacitor, L1... Coil.

Claims (1)

[Claims] An on/off circuit consisting of a switching diode is inserted in the signal transmission path from the antenna input terminal to the output terminal.
This diode has a resonant frequency set to the interference frequency.
An antenna mixer characterized by adding a C series resonant circuit.