JPS62230228A - Two-frequency band reception system - Google Patents

Abstract

PURPOSE:To use a main converter at two frequency bands by using an additional converter so as to convert the 1st frequency band into the 2nd frequency band in a system receiving the two frequency bands using one antenna. CONSTITUTION:In case of the reception of 4GHz band, a signal from a satellite is convered into an IF signal in IGHz by a low noise converter 21 aud fed to an indoor receiver via a cable 24. On the other hand, in case of the reception of 12GHz band, the signal from the satellite is converted into a 4GHz band signal by a 12GHz low noise converter 22. The converted 4GHz band signal is resent toward the antenna 23 via a primary field 225. The signal reflected in an antenna 23 is converted into a lGHz band IF signal by the 4GHz band converter 21. Thus, a signal in 12GHz band is received by using the 4GHz band converter 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a satellite broadcast receiving system, and particularly to a dual frequency band receiving system that receives radio waves in two different frequency bands.

(Prior art) As is well known, in North America, CATV is used in the 4 [GIIz] band.
(Cable Television System) Television signals are sent from satellites in geostationary orbit for transmission.

In this case, there are actually more than 100 channels of television signals transmitted from more than a dozen satellites. In ordinary households,
The television signal is received by a receiving system consisting of a parabolic antenna with a diameter of about 3 m, a low-noise converter, and a receiver. In this receiving system, the direction of the antenna is changed using an actuator, and the directivity of the antenna is controlled so that it scans the geostationary satellite orbit with respect to the dozens of satellites.

By the way, in contrast to the above-mentioned 4 [GHzl band] television reception, D
BS (direct satellite broadcasting) is about to begin.

This DBS is intended for reception by ordinary households, and the transmitting power of the satellite is increased and the diameter of the receiving antenna is reduced.

When receiving both of these 4 [GHzl band signals and 12 [G11zl band signals], it is generally necessary to connect both receiving devices, that is, antennas, low-noise converters, receivers, and the outdoor low-noise converter and indoor receiver. Prepare two sets of cables. In contrast, an inexpensive system is being considered in which a low-noise converter capable of dual-band reception is created by sharing an antenna and connected to an indoor receiver using a single cable. As the above-mentioned low noise converter for two-band reception, the ones shown in FIGS. 3 and 4 have been considered.

The converter shown in Fig. 3 is designed with emphasis on performance;
[GHz band borrowing reception feeds 111 and 12 [HG
z]] for the two bands obtained by the second-order feed 11, low noise amplifiers 121, 122, mixer 131, LH, local oscillators 141, 142,
It has independent IF (intermediate frequency) amplifiers 151 and 152, and after converting each signal to IF times, the cable is selected by a switching path 16 and further connected to an indoor receiver via an IF amplifier 17. (not shown).

On the other hand, the converter shown in FIG. 4 places emphasis on price. This converter is an improved version of the converter shown in FIG.
[Convert to GHzl band signal and switch to 4 in switching circuit 18
[This is designed to switch and derive signals in the GHz band. In this converter, if the gain of the 4 [Gtlzl band receiver is sufficient, the 12 [GHzl band low noise amplifier 122 and 12 [G11zl band
Since there is no need to increase the gain of the converter section (mixer 1322 and local oscillator 142) that converts the signal into a high frequency band, the number of amplification stages can be reduced, and the cost can therefore be reduced.

However, the low noise converters shown in FIGS. 3 and 4 have the following problems.

In the converter shown in Figure 3, in order to increase reception sensitivity,
The first-stage IF amplifiers 151 and 152 are low-noise amplifiers 121 . , 122 , mixer 1
31, 132, local oscillators 141, 142, and the signal can be switched using the IF that has the least effect on reception sensitivity.
This is performed after the first stage of amplifiers 151 and 152.

Generally, reception sensitivity is expressed by the noise temperature Te of the receiver.

Influence ΔT on receiver reception sensitivity due to rear stage noise temperature Te-
e is expressed by the following formula.

Here, G is the power gain up to the subsequent stage. Therefore, it is better to provide the switching circuit 16, which has a high noise temperature, as late as possible to reduce the decrease in reception sensitivity.

For this reason, the converter shown in FIG.
A switching circuit 16 is provided after 51 and 152 to minimize the influence (deterioration) on the reception sensitivity of the receiver. However, with such means, a considerable amount of amplification is required to obtain the necessary amplification degrees for receiving two signals, which is very disadvantageous in terms of cost.

On the other hand, the converter shown in Figure 4 has fewer overlapping parts than the converter in Figure 3, so it has an advantage in terms of price, but in reality, the deterioration of reception sensitivity is large and it is not practical. There's a problem. In particular, since signals from satellites in the 4 [GHz] band are extremely weak, deterioration in receiving sensitivity is a fatal problem.

(Problems to be Solved by the Invention) This invention proposes that if a conventional two-frequency band receiving system emphasizes performance, the configuration becomes complicated and expensive, and if it is simplified, the performance deteriorates and becomes impractical. It has a simple configuration and has little deterioration in reception sensitivity2.
The purpose is to provide a frequency band reception system.

[Structure of the Invention] (Means for Solving the Problems) That is, the dual frequency band receiving system according to the present invention has the following features:
A first low-noise converter section that receives signals in the first frequency band and converts them into intermediate frequency signals; receiving a signal in a second frequency band to
and a second low-noise converter unit that converts the frequency band into a frequency band of 1 and transmits the frequency band to the antenna in a form similar to a plane wave.

(Operation) In other words, in the dual frequency band reception system with the above configuration, after receiving a signal in the second frequency band by the second converter section and converting it to the first frequency band, the signal is sent to the antenna in a form close to a plane wave. The first low-noise converter unit receives the converted first frequency band signal.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

Figure 1 shows its configuration, and 21 in the figure is 4 [GHz
] The second part of the low-choice, low-noise converter for the 12 [GHz] band is a parabolic antenna.

4 [The GHzl band converter unit 21 has a receiving primary feed 211, and its circuit configuration is as shown in FIG.
2, the signal is mixed with the oscillation signal from the local oscillator 213 in a mixer 213 to convert the signal into an IF multiplied signal, and is transmitted via an IF cable 24 to an indoor receiver (not shown).

The converter unit 22 for the 12 [GHz] band has a second feed for transmission 225 in addition to a second feed for reception 221, and its circuit configuration is shown in FIG. 2(b). That is, the output of the second order feed 221 for reception is amplified by the low noise amplifier 222, and the output of the second order feed 221 for reception is amplified by the low noise amplifier 222, and the output is amplified by the local oscillator 2 by the mixer 223.
After being mixed with the frequency signal from 24, it is sent out to the parabolic fist antenna 23 by a transmission feed 225.

Note that a bias circuit 25 is provided at the connection portion between the IF cable 24 and the converter sections 21 and 22. This bias circuit 25 connects the indoor receiver to the IF cable 2.
The power output sent through 4 is sent to each converter section 21.
．． 23.

The operation of the above configuration will be explained below.

First, in the case of 4 [GHz] band reception, the signal from the satellite is reflected by the parabolic antenna 23,
'4 [GHzl band - next feed 2] installed at the focal point
It is focused on 11. The focused signal here is 4 [GH
The low noise converter section 21 for the zl band converts the signal into an IF signal for the GIlzl band, and sends it to the indoor receiver via the ■F cable 24. Power for this 4 [GHzl band low noise converter unit 21 is supplied from the receiver through the IF cable 24.

In the case of reception in the 12 [GHz] band, the signal from the satellite is similarly reflected by the parabolic antenna 23 and transmitted in the 12 [GHz] band.
HZ] is focused on the primary feed 221 for the band. At this time, as shown in FIG. 1, if the primary feed 211 for the 4 [GHz] band and the primary feed 221 for the 12 [GHzl band are installed at different positions, A and B in the figure
As shown in , the directions of arrival of the radio waves to be focused are slightly different. Above 12 [GHz] Band-Next Feed 22
The signal received at 1 is amplified by a low-noise amplifier 222, and then frequency-converted by a mixer 223 to a signal in the 4 GHz band.

Therefore, the local oscillator 224 may be a fixed oscillator of 8 [GHz] band or 16 [GHz] band. Note that it is easier to create an oscillator if the oscillation frequency of this local oscillator 224 is set to the 8 [GHz] band, but if the oscillation frequency is set to the 8 [GHz] band,
[Since the frequency is generally inverted during GIIzl band reception, a polarity inversion circuit is required on the receiving side. 1 B CG)
Although this does not occur with frequencies in the [Iz] band, it has the disadvantage that it is difficult to make an oscillator and frequency fluctuations are large.

The band signal is retransmitted to the parabolic antenna 23 on a transmitting feed 225. At this time, for sending -
If the next feed 225 is transmitted in a state close to a plane wave as shown in C in the figure, the transmitted signal is highly efficient < 4 [GHzl
It is transmitted to the band-next feed 211.

The received signal is 4 [4 [1' in the GHzl band low noise converter section 21 as in the case of GHzl band reception] [
The signal is converted to an IF signal in the GHzl band and transmitted to an indoor receiver via an IP cable 24. This 12 [GHz
] Power for the band low noise converter section 22 is also supplied from the indoor receiver through the IF cable 24.

Next, reception sensitivity will be explained.

4'[6Hz'] band reception, 12 [GHz]
If the band converter unit 22 is not operating, the receiving method is no different from the original receiving method, so the receiving sensitivity hardly deteriorates. However, 12 [GHzl band reception converter section 2]
Although there is an influence of the portion where the parabolic antenna 23 is shaded by the parabolic antenna 23, it can be practically ignored in practice. However, when the 12 [GHzl band router unit 22 is operating, the reception sensitivity is slightly degraded.

12 [The noise temperature of the GHz part 22 is T
e 12.12 [The antenna noise temperature for the GHzl band is T a 12.12
] If the transmission loss up to the next feed 211 for band reception is L, then (T e12 + T a12) ・G12/L
is the noise increase when receiving in the 4 [GHz] band. Therefore, when the noise temperature of the antenna unit 21 for the 4 [GHz] band is Te4, and the antenna noise temperature for the 4 [GHzl band is Ta4, Te4 + Ta4''> (Te12+
T a 12) - If G/L is satisfied, reception sensitivity will hardly deteriorate.

Furthermore, even if the above formula is not satisfied, 12 [GHz
] If a method such as stopping the power supply to the borrowed converter section 22 is used, the reception sensitivity does not deteriorate.

Further, the increase in the noise temperature during reception in the 12 GHz band is (T a4 +T e4 ) L/G12 due to the antenna temperature Ta4 in the 4 GHz band and the receiver noise temperature Te4. From the above, the conditions for preventing noise sensitivity deterioration when receiving the 4 [GHz] band are G12<L, and the conditions when receiving the 12 [GHz] band are G12)L, which are contradictory to each other. Therefore, from the viewpoint of reception sensitivity, it is actually necessary to set G12>L and turn off the power to the 12 [GHz] band router unit 22 when receiving the 4 [GHz] band.

Therefore, the two-frequency band receiving system configured as described above includes two low-noise low-noise converters for the 12 [GHz] band in addition to the conventional 4 [GIlzl band satellite signal receiving system], and the frequency-converted 4 By retransmitting the [GHz] band signal toward the antenna, it is possible to receive signals in both bands. In this case, 12
Since the low-noise converter for the [GHz] band requires only two simple configurations, there are few parts that overlap with the low-noise converter for the 4[0)1zl band, and it can be manufactured at low cost. In addition, by appropriate design, 4 [GHz] band, 12 [GHz] band
It is also possible to minimize the deterioration of reception sensitivity in both [GHz] bands.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a two-frequency band reception system that has a simple configuration and has little deterioration in reception sensitivity.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a two-frequency band receiving system according to the present invention, FIG. 2 is a block diagram showing the configuration of main parts of the same embodiment, and FIGS. 3 and 4 are respectively conventional FIG. 2 is a block diagram showing the configuration of a low-noise converter used in the reception system of FIG. 21...4 [GHz] band low-choice low-noise converter 2
Part 1...4 [GHzl band reception - next feed, 21
2...Low noise amplifier, 213...Mixer, 214...
...Local oscillator, 215...IF amplifier, 22...
12 [G11z] band low noise converter section, 221・
・・12 [GHzl band reception - next feed, 222・
...Low noise amplifier, 223...Mixer, 224...
Local oscillator, 225...12 [For GHzl band transmission-
Next feed, 23... Parabolic antenna, 24...
・IF cable, 25...bias circuit.

Claims (1)

[Claims] In a two-frequency band reception system that receives signals in first and second frequency bands using one antenna, the first
a first low-noise converter section that receives a signal in a frequency band and converts it into an intermediate frequency signal; a first low-noise converter section that receives a signal in the second frequency band and converts it into the first frequency band; A dual frequency band receiving system comprising: a second low-noise converter section that transmits in a form similar to a plane wave.