JPS5915336A - Receiving device - Google Patents

Abstract

PURPOSE:To minimize the disturbance given from the broadcast waves excluding a desired one, by selecting the frequency of an intermediate frequency signal at a prescribed level when satellite broadcast waves are received. CONSTITUTION:The 1st intermediate frequency amplifier IF8 is connected to a receiving device via an outdoor unit and a coaxial cable 7. The output of the IF8 is applied to the input terminal at one side of a 90 deg./3dB coupler 18. At the coupler 18, an IF signal is applied to a terminal 20 and output signals are extracted from terminals 22 and 23. These outputs are set at 1/2 electric power compared with an input IF signal wth phases different by 90 deg. from each other. These output signals are applied to mixers 10A and 10B, and the local oscillating output of a local oscillator 11 is supplied to each mixer via a power distributor 24. The output of each mixer is supplied to a coupler 27 (same as the coupler 18) via LPF25 and 26. An addition output of outputs of the LPF25 and 26 with a 90 deg. phase shift is extracted at an output terminal 30 of one side, and at the same time the opposite addition output is extracted at an output terminal 31 of the other side. Then a desired signal emerges at one of these terminals 30 and 31; while an image signal emerges at the other terminal. These signals are applied to a switch circuit 32.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device applied to reception of satellite broadcasting, and its purpose is to select the frequency of an intermediate frequency signal to a predetermined value to prevent broadcast waves other than desired waves from being transmitted. The goal is to minimize interference with

A general double superheterodyne satellite broadcasting receiver has a configuration shown in FIG.

In FIG. 1, reference numeral 1 indicates an antenna composed of a parabolic main reflector, a sub-reflector, and an electromagnetic horn. A circularly polarized wave generator 2 is connected to the electromagnetic horn of the antenna 1.

For example, the circularly polarized wave generator 2 has a polarization plane of linearly polarized wave Il, ! in a circular waveguide. The structure is such that the dielectric material is inserted at an angle t0. The circularly polarized wave received by the antenna 1 is converted into a linearly polarized wave by the circularly polarized wave generator 2,
(not shown), the transmission path is changed from a rectangular waveguide to a coaxial cable. And the received signal is SHF
The signal is supplied to a mixer 4 via an amplifier 3. This mixer 4
is supplied with a local oscillation signal from a first local oscillator 5, and a first intermediate frequency signal appears at the output of the mixer 4. The output of this mixer 4 is supplied to a first intermediate frequency amplifier 6. The device from this antenna 1 to the first intermediate frequency amplifier 6 is as follows:
Installed outdoors.

This outdoor unit is coupled to the indoor unit via a coaxial cable 7. Reference numeral 8 indicates a first intermediate frequency amplifier of the indoor unit, and its output is passed through a variable bandpass filter 9 to select a desired wave, which is then sent to the mixer 0.
You will be given one salary. This mixer 0 is supplied with a local oscillation signal from a second local oscillator 11, and a second intermediate frequency signal is obtained as its output. This intermediate frequency signal is supplied to an FM demodulator 15 via a second intermediate frequency bandpass filter 2, a second intermediate frequency amplifier 13, and a limiter 14. A composite color television signal appears at the output of this FM demodulator 15 and is supplied to a video signal circuit 16 and an audio signal demodulation circuit 1T.

According to the plan decided at the World Conference of Radio Administrators held in Geneva in 7977, the center frequency of the 72 GHz band satellite broadcasting channel is the first channel //, 727
'1gGHz to 4th channel/:1. ll
7g! ; up to OGHz/9. /g■It is set every 2. The frequency of the first local oscillator 5 is /0
．． If you select g GHz, the center value of the first intermediate frequency is 1F.
As shown in FIG. 2, 927. lIg MHz! From (1st channel)/Otori! ; , left OMHz (
4th channel).

In the case of selection, both the center frequency of the variable bandpass filter 9 and the local oscillation frequency of the second local oscillator 110 are changed to obtain a U-th intermediate frequency signal having a constant frequency. However, like the satellite broadcasting in the /2 GHz band mentioned above, lI from a wide band of g 00 MHz
When selecting the O channel, the center frequency of the pass band of the variable bandpass filter 9 (27 M) (This has the drawback that the range of z must be changed, which makes the design very complicated and difficult to implement. In other words, in the case of a mechanical channel selection device, there are lIg bandpass filters and lIg sets of local filters.) Components surrounding the oscillator are required, and the amount of components becomes enormous.Furthermore, in an electronic tuning device using a voltage variable capacitance element, both the variable bandpass filter 9 and the second local oscillator 11 are Since the width is large, it is difficult to achieve this with the currently available Paris Cage, and tracking both is extremely difficult.

An object of the present invention is to realize a receiving device in which the frequency change width of the local oscillator is narrower than υ and the above-mentioned problems are solved.

An embodiment of the present invention will be described below with reference to FIG. Similar to the receiving device shown in FIG. 1, a first intermediate frequency amplifier 8 is connected to the outdoor unit via a coaxial cable T. The output of the first intermediate frequency amplifier 8 is supplied to one input terminal of a 90°/3 dB cazola 18 without passing through a variable bandpass filter.

As shown in FIG. 7, this 90°·3d13 cazola 18 has a square shape with one side of the microstrip line having a length of 〒(λ: double signal/wavelength). Then, the first intermediate frequency signal is supplied to the terminal 20, and the terminal 21
Resistance between and ground,! i0Ω (characteristic impedance of the line) is connected, and output signals are taken out from terminals 22 and 23, respectively. The first intermediate frequency signals appearing at the terminals 22 and 23 are earth power and have phases different from each other by 90°.

The first intermediate frequency signals whose phases are different by qθ° are supplied to mixers IOA and 10B. Further, the local oscillation output of the second local oscillator 110 is passed through the power divider 24, so that it is divided into two parts and supplied to the mixers 10A and 10B. A specific example of the power divider 24 is a resistive voltage divider circuit. The outputs of mixers 10A and 10B are passed through low-pass filters 25 and 26, respectively, to 900.
It is applied to two input terminals 28 and 29 of a 3 dB coupler 27. The low-pass filters 25 and 26 are for removing unnecessary signal components.

This qOo・3 dB Casola 2T has the same configuration as that shown in Fig. 2, and the output of the low-pass filter 25 and the output of the low-pass filter 26, which are transferred and summed by 9θ0, and the sum output are output from one output terminal 30. The sum of the output of the low-pass filter 26 and the output of the low-pass filter 25 phase-shifted by θ0 is output to the other output terminal 31. A desired signal appears at one of these output terminals 30 and 31, and an image signal appears at the other.

These output terminals 30 and 31 are connected to two input terminals of a switch circuit 32. One of the two output terminals of this switch circuit 32 is connected to the second intermediate frequency band pass filter 1.
2 input terminal, and the other side is a 500Ω resistor 33
is terminated by The switch circuit 32 has a first connection that connects the output terminal 30 of the 90° 3 dB coupler 27 to the intermediate frequency band pass filter 12 and connects the output terminal 31 to the resistor 33, as shown by the solid line. and a first connection state in which these connection relationships are switched, as shown by the broken line, and can be switched by a control signal from the terminal 34. This control signal is generated in conjunction with channel switching.

In one embodiment of the invention described above, 900·3 dB
The manner in which the desired signal and the image signal are separated and taken out from the output terminals 30 and 31 of the coupler 27 will be explained below.

First, the output terminal 22 of the 900.3 dB oak 218
The input signal S1 appearing in is expressed by the following formula.

Sl-cos (ωRt+φR-900)=sin(ω
Rt + φR) Here, ω and φ2 are the angular frequency and phase of the input signal S. j, the input signal S appearing at the output terminal 23
2 is expressed as S2=cos (ωRt+φR). Local oscillation output S3 of second local oscillator 11
If the angular frequency and phase are ω and φ1, then S3=cos (ωL t+φL). Therefore, the signal obtained from the mixer IOA after frequency conversion is Sl・S3=5in(ωRt+φR)・cos(ωL
+φL)=T-(5in((ωR+ωL)t+φR+φ
L)+5in(ωR-ωL)t+φR-φI7)
], and the component in the previous term is attenuated by the low-pass filter 25. Moreover, the signal obtained from the mixer 10B after frequency conversion is Sz・Ss□=cos(ωRt+φR)・cos(ω
L+φL)−−7(cos((ω2+ωL)t+φR+
The above component is attenuated by the low-pass filter 26. Then, we set (ωR−ω,,)1ω■, and (φR
-φL) is set as φ1, the signal sA taken out at the output terminal 30 of 900·, 3 dB force y' is expressed by the following equation.

sA=5in(ωIt-1-φl-90°) +co
s(ω■ to 1φ■) ==-cos(ωIt+φ0 10c
os (ωT1+φT)−〇・ Also, 9θ0・,? dB coupler 27 output terminal 3
1, the signal s8 taken out at
ωt+φI)-sin(ωIt+φ1)+5in(ω
It+φI)=, 2 sin (ω■t+φ■). As described above, when the local oscillation frequency is lower than the frequency of the input signal (ω > ω), the desired signal is extracted to the output terminal L terminal 31. Also, (ωR〈ωL
, ωL-ωR-ωI) appears at the output terminal 3o. Therefore, (ω2〉ωL)
In this case, the switch circuit 32 is in the λ-th connection state indicated by the broken line.

Further, when receiving a desired signal having the relationship (ωR<ωL), the desired signal appears at the output terminal 30, and the desired signal appears at the output terminal 30.
Since the image signal appears at 1, the switch circuit 32 is in the first connection state shown by the solid line.

Furthermore, to describe in detail an embodiment in which the present invention is applied to reception of satellite broadcasting, the local oscillator frequency f of the first local oscillator 11
L is the difference in center frequency between channels (/9.7
g MHz), and the value of the center value IF of the first intermediate frequency is the frequency change width (g00■1.z
) shall be considered to be greater than or equal to -. As described above, by selecting the frequency of the second local oscillator 11, the image frequency is completely terminated to coincide with the center value of the other channels.

- As an example, local oscillation frequency &3 (//;Ig,za7
M)tz~/4t93.29MEIz) When changed in steps of /9, /gPJfi■z, it corresponds to the signals from the 1st channel to the 20th channel ( IF=20
7.39 The intermediate frequency signal of M)(z) is θ0・
3 dB is obtained at the output terminal 30 of the coupler 21.

Also, the local oscillation frequency f is C/109. A7MHz
~/'I7'1. / / MHz) in the range /
When varied in steps of 9.7 g MHz, the second
The intermediate frequency signal corresponding to the signals from the 7th channel to the 10th channel is 900.3 dB coupler 27
is obtained at the output terminal 31 of.

That is, when receiving from the first channel to the 20th channel, the switch circuit 32 is in the connected state shown by the solid line (see Figure 13), and the switch circuit 32 is in the connected state shown by the solid line (see Figure 13)
When receiving up to the channel, the switch circuit 32
is in the connected state shown by the broken line (see FIG. 3). - As an example, the 10th channel (IF, -/ / 00./
θMHz), the terminal 30 is connected to the intermediate frequency band pass filter 12 via the switch circuit 32.
The terminal 31 is terminated with a resistor 33.

Then, it was designated as (fL-130/, Hiro9MH2), and the first
A third intermediate frequency signal corresponding to the signal of the θ channel appears at the terminal 30, and a third intermediate frequency signal corresponding to the image signal of the first O channel (IF, =/502.g MHz).
) is input, the Cth intermediate frequency signal is terminated at the terminal 31 and does not interfere with the 70th channel.

As understood from the above description of the embodiment, according to the present invention, the desired signal and the image signal can be extracted separately, so there is no need to provide a variable bandpass filter as in the conventional case. There's no need.

This invention makes it possible to narrow the frequency variation range of the local oscillator. Therefore, according to the present invention, the circuit configuration of the channel selection device can be greatly simplified.

It should be noted that the present invention can also be applied to receiving devices other than satellite broadcasting to achieve similar effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of a satellite broadcasting receiver to which the present invention can be applied, FIG. 2 is a route map showing an example of the value of the first intermediate frequency of satellite broadcasting, and FIG. A block diagram showing the configuration of an embodiment of the invention, Fig.
FIG. 2 is a plan view showing a specific configuration of a coupler. 8......First intermediate frequency amplifier, 9...
Song: Four variable bandpass filters, 11...Song...
...Second local oscillator, 12...No.2
Intermediate frequency band pass filter, 18.27...
...qOo・3 dB coupler, 32...switch circuit. Agent Masatomo Sugiura

Claims (1)

[Claims] The input signal is divided into two signals having a phase difference of 9 degrees from each other, frequency converted by a common local oscillation signal, and 2 of the frequency components of the difference between this local oscillation frequency and the input frequency.
One of the frequency-converted signals is phase-shifted by 90 degrees and combined with the other to obtain a seventh output signal, and the other signal is phase-shifted by 90 degrees and combined with one. A receiving device which obtains a first output signal by extracting one of the first and second output signals as an output signal and suppressing the other in conjunction with the operation of a channel selection means.