JPS5947814A - Rf modulator - Google Patents

Abstract

PURPOSE:To decrease high frequency loss by constituting a balanced transformer with a pickup lead and a coaxial line so as to save a balanced transformer. CONSTITUTION:A UHF oscillator 1 consists of the coaxial line 2, an oscillating transistor(TR)3, a terminating capacitor 4, a variable capacitor 5 and the pickup lead 6. The middle point of the lead 6 is grounded via a bypass capacitor 10 and a bias voltage is applied from a bias control terminal 11 via a choke coil 19. Since the middle point of the lead 6 is grounded, the lead 6 constitutes the balanced transformer together with the line 2.

Description

[Detailed description of the invention] The present invention is an RF' modulator used in the LJHF band.

In particular, in a balanced type RF modulator, it is possible to eliminate the balanced transformer by grounding the midpoint of the pickup conductor in the carrier wave generation circuit and making it function in the same way as if a balanced transformer were installed in a cylinder. This invention relates to an RF modulator that is capable of reducing high frequency loss and cost.

Conventionally, a balanced 1ζF modulator as shown in FIG. 1 has been known. The illustrated variation K in FIG. 1 is (J, [-IF'
The carrier wave is modulated by, for example, a video modulation signal. That is, the UHF oscillator 1 that generates a UHF carrier wave consists of a coaxial line 22, an oscillation transistor 3. It is composed of a termination capacitor 4, a variable capacitor 5, and a pickup lead 6, and the UHF carrier wave is outputted by the pickup lead 6.

The UHF carrier wave outputted by the pickup lead 6 is applied to modulation diodes 8 and 9 via a balanced transformer 7, and a video signal input from a modulation signal input terminal 12 via a signal attenuation resistor 13. is subjected to carrier suppression width modulation. The amplitude-modulated video modulation wave is a transport wave +r, (passes through a 1/ti1 capacitor 14, is further made to an appropriate level by an attenuator consisting of resistors 15, 16, and 17, and is output from a modulated wave output terminal 18. Note that the midpoint of the secondary line of the balanced transformer 70 is connected to the ground at high frequency by the high-frequency conductor 910.Bias control terminal 1
A bias voltage is applied via 1.

The balanced transformer 7 used in the conventional G1U11 shown in FIG.
It is necessary to increase the output of for that purpose.

Not only does it lead to higher costs because it is necessary to increase the power of the oscillation transistor 3, but also the above 11.
[i By increasing the output of F oscillator 1,
Undesirable problems such as waveform distortion and spurious waves are likely to occur. Moreover, the above-mentioned balance transformer 7 is.

It goes without saying that it is desirable to have a transformer with as good a balance as possible, but it is extremely difficult to manufacture a transformer with a good balance If in the UHF band, which results in high costs.

The present invention aims to solve the above problems,
By grounding the midpoint of the pickup conductor in the transmission circuit and making it function equivalently to a balanced transformer, it is possible to eliminate the balanced transformer.

Lt that can reduce high frequency loss and reduce costs
The aim is to provide an F modulator.

This will be explained below with reference to the drawings.

FIG. 2 shows one embodiment of the circuit 1z1. FIG. 3 shows a circuit diagram of another embodiment of the present invention. Codes 1 to 6 and 8 to 18 in the figure correspond to 21) 1, and 1
9 and 20 are choke coils.

21 and 22Fi capacitors are represented.

In the embodiment shown in FIG.
The midpoint of lead 6 is connected to high frequency ground via the bypass, capacitor], 0, and the bias "conductor".
A bias voltage is applied through the Yoke coil 19 to the K terminal 11. That is, by grounding the middle point of the pickup lead 6, the pickup lead 1-"6r:1 : Together with the coaxial line 2, it essentially constitutes a balanced transformer. Accordingly, in the illustrated embodiment of FIG.

There is no need to install another independent balancing transformer, and the problem 111 caused by providing a vertical balancing transformer can be solved. .

The amplitude modulation for the U IIF 12> transmitted wave output from 6 is performed based on the 1 central image signal input from the modulation signal input terminal 12 (as in the conventional example shown in FIG. 1).
1 and 9 are similar. The impedance of the choke coil [9] is set to i+i:j such that the impedance of the choke coil 9 is i+, higher than the frequency of the UHF carrier wave, and lower with respect to the modulation signal.

The conventional example shown in FIG. 1 is basically f:r, and FIG. 2 is the same as the first non-embodiment. Since, together with the coaxial line 2, substantially constitutes a balanced lance, there is no λ obtained by the balanced transformer 4. In the embodiment shown in FIG. 3, as shown in FIG. and 22 are also provided, and choke coils 19 and 20 are provided in the fourth.

Connection between the choke coils 19 and 20: I:
, are grounded via a bypass capacitor 10, and a bias voltage is applied via a bias control terminal 11. Naka, top, i12 choke-impedance of coils 19 and 20 +-4;

U HF I & 4 transmitter's frequency, therefore -CI/Yellow, and 4 is set so as to be small for the modulation signal.

As explained above, according to the present invention, i+J'', 217
-'i It becomes possible to delete the short transformer 4
Shut up.

It is possible to provide a balanced type tt 1i'' converter that can reduce high frequency loss and contribute to cost reduction.

[Brief explanation of drawings]

FIG. 1 (is a conventional circuit ll!3 configuration, the second diagram is a configuration of an embodiment of the present invention, and FIG. 3 is a (ll1'-,
1M/41 cases + 1 yen composition is shown. In the figure, 1 is U HF oscillator, 1' is U, ) I li'
The oscillator body, 2 is the coaxial line, and 3 is the oscillator transistor. 4 is a termination capacitor, 5 is a variable capacitor, 6 is a pickup lead, 8 and 9 are modulation diodes, 10
1 is a pass capacitor, 1 is a bias control terminal, 12 is a modulation signal input terminal, 13 is a signal attenuation resistor, ], 4 is a general, and 5 is a pass capacitor.
17 to 17 are resistors, 18 is variable' = F4 is the output terminal,
19 and 20 represent choke coils, 21 and 22 represent content. Patent applicant Alps Electric Co., Ltd.

Claims (1)

[Claims] A balanced RF modulator comprising a carrier wave generation circuit that generates a carrier wave in the UHF band, and a balanced modulation circuit that modulates the carrier wave output from the pickup conductor portion of the carrier wave generation circuit with a modulation signal, the carrier wave generation circuit as described above. An RF modulator characterized in that the center point of the big up conductor section is grounded.