JPS5820040A - Tuner - Google Patents

Abstract

PURPOSE:To ensure stable channel selection for a TV picture receiver of a double superheterodyne system, by converting a receiving frequency into the 1st intermediate frequency with the frequency obtained by mixing the frequencies of a variable oscillator and a fixed oscillator through a mixer. CONSTITUTION:The oscillating frequency F2 of a fixed oscillator 7 and the oscillating frequency F1 of a variable frequency oscillator 11 are fed to a mixer 12 to produce a frequency F3=F2-F1. This frequency F3 is supplied to the 1st mixer 4. The mixer 4 mixes receiving frequencies f0 and F3 to produce the 1st intermediate frequency 1Ff1=f0+F3. The frequency f1 is amplified by the 1st IF amplifier 6 via a filter 5 and applied to the 2nd mixer 8. The mixer 8 mixes the f1 and F2 to obtain the 2nd IFf2=F1-f0, and f2 is amplified by the 2nd IF amplifier 9 to be delivered. The 2nd IFf2 contains no F2 and receives no effect of drift caused by the temperature change, the secular change, etc. of the oscillator 7. Then the oscillator 11 is controlled by a PLL circuit using a reference signal source. In such a way, a stable channel selection is possible with no shift of frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a double superheterodyne television set.
Regarding frequency conversion means in a chainer such as a receiver,
! It is one thing.

A conventional example of this type of island is shown in FIG. In the figure, 1 is an antenna, 2 is a wideband amplifier, 3 is a variable frequency oscillator, number is a first mixer, 5 is a bandpass filter, and 6
Fi is the first intermediate frequency amplifier (hereinafter, the intermediate frequency is abbreviated as F), F is the fixed station wave number oscillator 1.8 is the M22 mixer, e
Fi 211P amplifier, 10 is an output terminal, a wide band amplifier 2 amplifies the received signal of frequency f0 which has been inputted from the antenna 1, and the oscillation of usable frequency oscillator 3 - wave number F is used to produce FIIFf at the first mixer number. , is frequency-converted to 1xv, which is passed through a narrowband bandpass filter 6, amplified by the first A signal Ff (normal intermediate frequency of a movie theater) is generated, amplified by the 21' IP amplifier 9, and multiple outputs are output from the output terminal 10.

In order to process these 6 double superhetero gain system electronic channels all at once on TV 2-run receivers (50 to 900 MH2), the 3G Hy
s, and the variable oscillation frequency 21 and fixed oscillation frequency F are high frequencies of 2 to 3 GHz. Therefore, there is a problem in that the oscillator has a large wave number drift due to fluctuations in mountain passes, humidity, temperature, etc., making it impossible to perform regular channel selection operations.

It is an object of the present invention to eliminate the drawbacks of the prior art described above, and to provide a double super helical rodine system that reduces the frequency drift F of the oscillator and enables stable tuning operation*8 using a simple circuit configuration. Our goal is to provide electronic chips for television receivers.

The configuration of the present invention includes a WJl oscillator with 11 wave numbers, an IR2 oscillator for frequency identification, a #11 mixer for converting the received signal into a first signal, and a 1st IF
a second mixer that converts the frequency of the signal into a second signal;
It is equipped with a 11g3 mixer that mixes the output signal of the first oscillator and the output signal of the second 1# oscillator, mixes it in the third mixer, and excites the first mixer with a good signal. Toto411C,I
I! , 2 mixers are excited by the output signal of the second oscillator.
This book is characterized by b.

In order to specifically explain the present invention using an example shown in figure gg,
In the figure, books having the same functions as those in FIG. 1 are given the same numbers, and explanations of their operations will be omitted. In Figure 2, h
11 is a variable frequency oscillator; 12 is a third mixer; It is added to the container 12.

At the same time, the output signal of the oscillator 11 is added to the third mixer 12, and the b mixed signal generated by the third mixer 12 is added to the mixer 4 of 91. The received signal frequency f, is converted into the first signal, Ff.The mixed signal of the difference generated in the third mixer 12 -〇i
! How many ilN? , then % 'a is the following formula % formula % (1) Also, % 'j and f are as the following formula.

10F to fl-, ・4・・・・・・・・・・・・・
・・・・・・・・・(2) f 佳P −F 〜・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
(3) t I I Substitute formula (1) into formula (2) [2, and then replace formula (2) with formula (3)
)2- Substituting, 'v is expressed as the following equation.

f, -'ll1-f, ・・・・・・・・・・・・
...River...River... (4) As is clear from equation (4), the second construction! The frequency F of the variable oscillator 12,
and the frequency ff number of the received signal! - Determined by ``1'', which is not affected by the frequency drift of the fixed oscillator. Therefore,
Pub using a stable external reference signal source for the variable oscillator 11
If controlled by a (phase synchronized circuit) or the like, an accurate I frequency conversion signal can be obtained, and a stable channel selection operation can be performed.

Further, equation (4) can be expressed in the form of the following equation.

A, -f, +f, ・・・・・・・・・・・・・・・
・・・・・・・・・・・・(5) In general, the television signal frequency is 900MHg or less, and more! Since ν is less than 60 MHg, the frequency F of the variable oscillator 110 is 1011
For example, in the case of the Japanese channel, the received signal is 90~fufu OMHm, and the second rainbow is 57M1I cod, so 1. becomes 14'/~82fMHtx, and 1. is the same as the frequency of the variable oscillator of a conventional single superhetero gain type television set.

Furthermore, 9,1G
Since it is less than Hg, it is possible to suppress the frequency drift well. Therefore, the channel selection circuits of the television set 1 used in the conventional single superheterodyne system electronic channels, such as the Volley-5 channel selection circuit, the voltage synthesizer channel selection circuit, the PL+L synthesizer channel selection circuit, and the 8-channel W ( There is an advantage that a channel selection circuit using a surface acoustic wave (surface acoustic wave) device can be used.

In this example, F, F, and ? , but it goes without saying that the same effect can be obtained by using the sum of the image frequencies.

DI As mentioned above, according to the present invention, it is possible to eliminate the influence of frequency drift of a fixed oscillator, which has been a problem in the past. Furthermore, in the past, the variable oscillator was 2 to 3G11
It was difficult to stably vary the frequency and oscillate with a high hmtrt number of 1x, but according to the present invention, the variable oscillation frequency is 1 GHz or less, so stable oscillation can be obtained and stable channel selection operation is possible. said Naru. Therefore, since the conventional single superhetero gain type electronic channel selection device can be used, a highly versatile channel can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional example of a chainer for a double superhetero gain type telephony receiver, and FIG. 2 is a block diagram of an embodiment of the present invention. 4=First mixer F: Fixed oscillator (second oscillator), 8: Second mixer 11: Flexible oscillator (first oscillator) 12: Third mixer Agent Patent attorney Fumio Watanabe 11fl'!

Claims (1)

[Claims] In a double super-hetero gain type television receiver system, a first oscillator that can use a frequency, a second oscillator that has a fixed frequency, and a first intermediate frequency signal Kll wave number conversion for a received signal are used. a first mixer for frequency converting the first intermediate frequency signal into a second intermediate frequency signal; and a first mixer for converting the frequency of the first intermediate frequency signal into a second intermediate frequency signal; a third mixer;
When the first mixer is excited with the output signal of the mixer of 4%, the second mixer is excited with the output signal of the oscillator of IIE2. ! It's moldy and b-chi-su.