JPH0358604A - Satellite broadcast transmitter and receiver input circuit - Google Patents

Abstract

PURPOSE:To avoid disturbance of a satellite broadcast due to a harmonic wave of a television signal onto a 1st intermediate frequency signal by providing a high pass filter(HPF) attenuating the television signal. CONSTITUTION:A resonance circuit comprising a 1st coil 13 and a 1st capacitor 12 forming an HPF 2 and a 2nd coil 11 has a resonance frequency at nearly 500MHz being a half of nearly 1GHz being a lower limit of a 1st intermediate frequency. Moreover, a resonance circuit comprising a 3rd coil 16 and a 5th capacitor 15 has a resonance frequency at nearly 650MHz being a half of nearly 1.3GHz being an upper limit of the 1st intermediate frequency. Thus, since a signal having a frequency ranging from the minimum frequency signal to a half the 1st intermediate frequency of the satellite broadcast among television signals applied to the 1st intermediate signal input terminal 1 of a satellite broadcast receiver is sufficiently attenuated by the HPF 2, no harmonic wave of the television signal is caused. Thus, the disturbance resulting from overlapping the 1st intermediate frequency signal and its harmonic wave of the satellite broadcast is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a first intermediate frequency input circuit for a satellite broadcast receiver.

Conventional technology In order to receive satellite broadcasting, radio waves in the 12 GHz band radiated from a geostationary satellite are received by an antenna, and then frequency converted into a first intermediate frequency signal in the IGH 2 band by a low-noise downconverter. and input the signal to the indoor satellite receiver via cable. In a satellite broadcasting receiver, after selecting one of several channels of signals, FM demodulation is performed to obtain video signals and audio signals.

A conventional example will be described below with reference to the drawings. FIG. 4 shows a part of a block diagram of a conventional LJ satellite broadcasting receiver and the configuration of one input circuit.

In FIG. 4, 1 is an input terminal for the first intermediate frequency signal, and an F connector is used. 3 is 1.5V to the outdoor downconhark.
This is a power supply terminal that provides DC power.

2 comprises a Takagi pass filter (Hl)F).

4 is a preamplifier circuit, which is necessary in order to improve the NF at the receiver input terminal 1 since the NF of the image filter 5, Mikuna 6, etc. following the subsequent stage is poor.

Reference numeral 7 denotes a local oscillator, which, together with the mixer 6, has a channel selection function. Reference numeral 8 denotes a Han 1-pass filter (B P F), which serves to select only one wave to be demodulated by the demodulator 9 and remove noise and interfering IS signals.

Now, an example of the characteristics of I-{P F 2 is shown in FIG.

This figure shows the frequency characteristics from the input terminal 1 to the input end of the preamplifier circuit 4. It is designed to have an attenuation of about 20 db at 403 MHz, which is the second intermediate frequency. This is to prevent noise and interference from occurring in the second intermediate frequency after frequency conversion if the fee through characteristics (isolation characteristics) of ξ Kuza 6 are poor (References: Satellite broadcast reception Machine Part 1 Target Rating (Published by Radio Technology Association).

Problems to be Solved by the Invention However, in recent years, it has become common practice to mix the terrestrial-to-hire television broadcasting signal and the first intermediate frequency signal of satellite broadcasting near an outdoor antenna, lead it outdoors via a single cable, and then distribute it. Since then, a form has emerged in which the television signal and the first intermediate signal of the TV broadcasting are divided and each of them is received. If the splitter used in this case does not have sufficient demultiplexing ability, or if the television signal is strongly amplified by a booster, etc., the input section of the satellite broadcast receiver may In some cases, the input level of the television broadcast signal is much higher than the input level of the first intermediate frequency signal.

In such a case, the satellite broadcast receiver will
One wave is selected from the intermediate frequency signals to create a second intermediate frequency signal, which is detected and compared with the reference. Since the 80C (automatic gain control circuit) is activated, even if there is no gain in the first intermediate frequency band. Even if it has a control function, the front end Doso width circuit and the mixer concave circuit of the first intermediate frequency band will cause excessive input to television broadcast signals. Therefore, harmonics of the television broadcast signal occur in the preamplifier circuit and the mixer circuit. If some of the harmonics overlap with the first intermediate frequency signal of satellite broadcasting, there is a problem in that an interference phenomenon occurs.

In view of the problem described in -L, the present invention provides that the television signal level is the first level of the satellite broadcast at the input terminal of the satellite broadcast receiver.
Good input V in the first intermediate frequency band, which is broadband and does not cause interference even when the level is equal to or higher than the intermediate frequency signal level.
A satellite broadcast receiver input circuit with SWR is proposed.

Means for Solving the Problems - In order to solve the problems listed in item L, the satellite broadcast receiver input circuit of the present invention includes a first coil and a first capacitor connected in series to the first intermediate frequency signal input terminal. A resonant circuit consisting of the connection is connected, and a power supply terminal grounded at the second capacitor is connected to the connection point between the first coil and the first condenser via the second coil. , the input terminal and the first
A resonant circuit consisting of a third coil and a fifth capacitor connected in series is provided at a connection point between the third and fourth capacitors connected in series between the input parts of the intermediate frequency amplification circuit.

According to the above-described configuration, the resonant circuit including the first coil, the first capacitor, and the second coil has a resonant frequency of about 500 MHz, which is half of the lower limit of the first intermediate frequency, about I GHz. , and the resonant circuit consisting of the third coil and the fifth capacitor →
A high-pass filter with a resonance frequency of −f1 at 0 MHz is formed.

Therefore, among the television signals applied to the first intermediate wave signal input terminal of the satellite broadcasting receiver, signals having frequencies from the most even frequency signal to half of the first intermediate frequency of the satellite broadcasting are Since the signal is sufficiently attenuated by the Takagi pass filter in the front stage of the preamplifier circuit, the preamplifier circuit and the circuits in the subsequent stages will not receive excessive input. Therefore, harmonics of the television signal are not generated, so there is no possibility that the first intermediate frequency signal of satellite broadcasting and its harmonics will overlap and cause harmonics.

In addition, U higher than half of the first intermediate frequency of satellite broadcasting
H l? Even if harmonics are generated in the band television signal due to excessive input, the frequency will be higher than the first intermediate frequency, so no interference will occur.

It is also possible that some harmonics of the television signal may cause interference in the image frequency band of the first intermediate frequency signal, but this is sufficiently suppressed by the image filter so that no interference occurs.

Embodiment Hereinafter, a satellite broadcasting receiver according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a processing diagram and an input circuit of a satellite broadcasting receiver according to a first embodiment of the present invention.

In FIG. 1, ] L1 first intermediate frequency input terminal, 2 Takagi pass filter (HPF), 3 downconverter power supply terminal, 4 ITIJ position amplifier circuit, 5 image filter, 6 BA MIKU 7, 7 is VCO (voltage controlled oscillator), 8
9 is an FM demodulator, and 10 is a Hann L bus filter. 1
2, 14. 15. 17 is a capacitor constituting HPF2, 11, 13. 1.6 is the same H P F
This is an air-core coil consisting of 2 parts. Specifically, a resonant circuit consisting of a series connection of the first coil 13 and the first capacitor 12 is connected to the input terminal l, and the second capacitor]0
A power supply terminal 3 grounded at The third and fourth circuits are connected in series between the input end of the width circuit 4.
capacitor]4. 3rd coil at connection point of 17〕6
and the fifth capacitor 15 are connected in series to form a resonant circuit.

Incidentally, since the air-core coil does not require a very high Q, it is also possible to construct it in a strinoplane pattern with a pudding 1 pattern. FIG. 2 shows a circuit diagram of an embodiment using a strip line.

In FIG. 2, 1 to 17 are the same as in FIG. 1, and coils +1. 13. 16 is Strinopurine 11 1
It has been replaced with 316. The preamplifier circuit 4 is shown as an example having two stages of transistors, with a strino prine 54. By incorporating a frequency characteristic correction circuit such as 60, the preamplifier circuit 4 obtains gain flatness in the first intermediate frequency band.

The operation of the satellite broadcasting receiver configured as described above will be explained. l-+ P F 2 is a Czesev-type H P F with two poles. An example of the gain and input return loss from the input terminal 1 to the preamplifier circuit output terminal 68 is shown in FIG. As shown in the figure, the double harmonic is the first intermediate frequency band (].04 to 1.33
502MHz ~ 660MHz
The Z band has an attenuation amount of 30 db or more compared to the first intermediate frequency band, and at frequencies where the other 3 and 4 times higher harmonics are in the first intermediate frequency band (500 MHz or less), the attenuation amount is about 20 db.
It has an attenuation amount of db. In general, in amplifiers such as 1 transistors, when the order of harmonics increases to 1, the generation level becomes low, so a large amount of attenuation is required to make it difficult to generate harmonics of the lowest order, 2 (f'j). For this purpose, an H having a lamp as shown in FIGS.
PF is effective because the number of stages (number of elements) can be reduced.

Further, as shown in FIG. 3, the input return loss at the input terminal can have a good value of 10 db or more in the first intermediate frequency band.

If H I) F2 with such characteristics is used, interference will not be detected even if the television signal is approximately 30 db higher than the first intermediate frequency signal of satellite broadcasting. If this is done, it is thought that there will be no practical problems.

4 In this example, the first intermediate frequency band of the BS is
=Ge-(Explanation 1-, f) CS that has been studied in recent years (
Di on iJ1 {f1 satellite - one system]. ．． 8G
It appears that frequencies as high as Hz are used as the first intermediate frequency band. , in the second case (J, −) −
A high-pass filter whose attenuation range is from the highest chill of the F band to the highest chill of the UHF 4ir for L/Vino 41 broadcasting, and whose pass band is the first intermediate frequency band. There is a necessary soda to use.

Effects of the Invention As described in Section 2, according to the present invention, by providing a high-pass filter that attenuates the television signal at the input stage of the satellite broadcasting receiver, the high-gI81 wave of the television signal can be transmitted to the satellite. It is possible to eliminate interference with the first intermediate frequency signal of broadcasting.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a satellite broadcasting receiver including an input circuit according to an embodiment of the present invention, and FIG. l'i in the example
l1 route map, Figure 3 is the H l of Figure 1.
11 Frequency characteristics diagram, Fig. 4z, 1. The frequency characteristic of the conventional satellite broadcasting receiver is 1:1 [2I. 5th {71 T:t,
The frequency characteristics of the input concave path compared to the conventional example are ``Me''. 1... At the input end, 2... - Takagi pass filter,
4... Preamplification channel, 10, 12, 1.4
, 15. 17...: I indensa, II. , !
3. 16... Coil.

Claims (3)

[Claims] (1) A first resonant circuit consisting of a series connection of a first coil and a first capacitor is connected to the input terminal, and a power supply terminal grounded by a second capacitor is connected to the power supply terminal via the second coil. A third coil and a fifth capacitor are connected to a connection point between the first coil and the first capacitor, and a third coil and a fifth capacitor are connected to the connection point of the third and fourth capacitors connected in series between the input terminal and the input section of the amplifier circuit. A satellite broadcasting receiver input circuit comprising a second resonant circuit connected in series with a capacitor. (2) The first resonant circuit has a first resonant frequency approximately half of the lower limit frequency of the satellite broadcast first intermediate frequency signal applied to the input terminal, and the second resonant circuit has a first resonant frequency that is approximately half the lower limit frequency of the satellite broadcast first intermediate frequency signal applied to the input terminal. 2. The satellite broadcast receiver input circuit according to claim 1, wherein the second resonant frequency is approximately half of the upper limit frequency of the input circuit. (3) The first signal outputted from the means for demultiplexing the mixed terrestrial television signal and the first satellite broadcast intermediate frequency signal.
a first resonant circuit consisting of an input terminal that receives an intermediate frequency signal, a series circuit of a first coil and a first capacitor inserted between this input terminal and ground; A series circuit of a second coil and a second capacitor in which one end of a second coil is connected to the connection point of the capacitor and the other end of the second capacitor is grounded, and the input terminal and the input terminal of the amplifier circuit. a series circuit of a third capacitor and a fourth capacitor inserted between the third capacitor and the fourth capacitor, and a third coil and a fifth capacitor inserted between the connection point of the third capacitor and the fourth capacitor and the ground. The second circuit consists of a series circuit of
a resonant circuit, and a power supply terminal is connected to a connection point between the second coil and the second capacitor.