JP3049083B2 - Double heterodyne signal selection circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to other information of the same specifications based on a first intermediate frequency band (BS-IF band) FM signal output from a satellite broadcasting receiver outdoor unit. A signal is added, and a single-channel signal according to the subscriber's request is selected by heterodyne frequency conversion from a multi-channel information service FM signal group arranged in a service band of an extremely wide frequency range including the BS-IF band by heterodyne frequency conversion. A double heterodyne signal selection circuit device such as a so-called demand access type CATV hub which supplies each satellite broadcast receiver indoor unit of a large number of subscribers, and particularly, a variable range of a local oscillation frequency required for double heterodyne signal selection. And reduce the number of frequency converters so that the circuit device can be economically constructed. It is obtained by way capable of reducing failure due to click.

(Summary of the Invention) The present invention provides a service band of an extremely wide frequency range including a BS-IF band obtained by frequency-converting a satellite broadcast from a 12 GHz band to a 1.3 GHz band, with the same frequency interval of 38.36M as that of satellite broadcast.
A demand access method in which a desired single channel signal is selected from a group of information service signals of many channels arranged in Hz, and the signal is frequency-converted to a BS-IF band and supplied to each subscriber's indoor unit of a satellite broadcast receiver. For signal selection by double heterodyne frequency conversion in CATV, etc., FM signals of many channels arranged in the same frequency interval as satellite broadcasting in the service band of a wide frequency range of 38.36 MHz in the mainline CATV are almost equally divided according to the carrier frequency. Then, the FM signal group in the higher half band has a frequency band substantially the same as that of each channel of the FM signal group in the lower half band, or a frequency band offset by almost half of a predetermined frequency interval. Frequency conversion to each conversion channel, and the FM signal group of the conversion channel and the corresponding channel of low half band to the high frequency switch After selectively switching, the FM signal of each desired channel is selected by the heterodyne method, the frequency variable width of the local oscillator used for selecting the desired channel is reduced by half, and the frequency converter is selected. Reduce the number and at the same time,
This is to prevent the occurrence of a failure due to crosstalk between channels due to switch switching.

(Prior Art) Only information signals corresponding to a subscriber's request from a trunk CATV information signal group in which FM signals having the same specifications as satellite broadcasting are arranged at the same frequency interval as satellite broadcasting are called hubs, Demand access type CATV which selects by the heterodyne method in the signal selection circuit device having the switching function and sends it to the subscriber system CATV in the BS-IF band etc.
This type of signal selection circuit device in a system is well known in the art. For example, in a conventionally proposed "FM multiplexed Hi-Vision optical CATV system using a demand access system" (IEICE Technical Report OCS89-51), transmission via a trunk line CATV is performed. When selecting a high-definition signal of a desired channel by heterodyne frequency conversion at a hub from a 34-channel MUSE system high-definition signal group, the local oscillator having the same frequency variable width as the bandwidth of the frequency band in which the input signals are arranged is used. Heterodyne signal selection is performed.

Also, the frequency band of the frequency-division multiplexed input signal is divided into two equal parts depending on the level of the frequency, and a signal group in one of the two equally divided frequency bands is frequency-converted into a signal group having the same frequency as the signal group in the other. A signal selection circuit device configured to select only one of the signals in the two equally divided frequency bands or a signal group by a high-frequency switch is also well known in the art. J69-B, No. 9, P. 904) has been proposed. In the signal selection circuit device proposed in the prior art, a component type HDTV signal having three carriers for each channel is composed of a group of 3FM signals corresponding to three signal components of a luminance signal and a two-color difference signal.
When transmitting one channel and selecting a 3FM signal for one channel from the HDTV signal group for two channels, a group of 3FM signals in one channel having a higher carrier frequency is converted to one group in a channel having a lower carrier frequency. After down-converting to the same frequency band as the 3FM signal, the 3FM signal in each channel is selected by switching with a high frequency switch.

However, when a desired transmission signal is selected by a heterodyne method from a transmission signal group of a main line CATV arranged at the same frequency interval as that of satellite broadcasting, the frequency band of the transmission signal group is divided into two equal parts, and one equal band is used. , And frequency-converts only the transmission signal group in the above to the other equally divided band, and selects the transmission signal of either group among the two transmission signals in the same equally divided band by the switch, and performs the desired transmission in the selected group. Conventionally, there has been no example of a signal selection circuit device configured to further select a signal by a heterodyne method.

(Problem to be Solved by the Invention) The heterodyne type signal selection circuit device used as a hub in the conventional demand access type CATV has the following two problems to be solved.

As a first problem, the frequency variable width of the local oscillator used for the heterodyne frequency conversion needs to be equal to the occupied band of all the channel signals to be serviced in the backbone CATV input to the frequency converter. . Generally, when the frequency of the converted output signal selected by the heterodyne frequency conversion is lower than the frequency of the input signal of the highest channel, the frequency conversion of the double heterodyne method is performed in order to avoid image interference at the time of the heterodyne frequency conversion. Perform Later, 1.3GHz band BS-
The FM signal selected by frequency conversion from the input FM signal group having a carrier frequency higher than the IF
When outputting to a band, the oscillation frequency of the first local oscillator in the double heterodyne frequency conversion is set to a value higher than the highest frequency of the input FM signal group. However,
In consideration of the characteristics of the frequency converter in double heterodyne frequency conversion, the manufacturing price, and the like, it is desirable to set the oscillation frequency of the first local oscillator to a value as low as possible. On the other hand, if the ratio band of the oscillation frequency variable width of the variable frequency oscillator such as a local oscillator to the center frequency is set to a low value of the local oscillation frequency, it will reach 50% or more. In addition, it is difficult to obtain substantially uniform oscillation output power over the entire wide frequency variable width, and there is a problem of a harmonic signal as described below.

That is, in a frequency variable oscillator having a fractional bandwidth of 50% or more, the frequency of the second harmonic component of the lowest frequency oscillation output becomes slightly higher than the highest oscillation frequency. Sufficient removal is not easy, and a low-pass filter having an extremely steep attenuation characteristic must be used in order to prevent power loss from occurring in the highest frequency oscillation output. Furthermore, in the case where such a wide frequency band variable frequency oscillator is configured using a frequency multiplier, removal of the fundamental frequency oscillation output component before multiplication must be considered, and a band for extracting only the multiplied frequency component is required. The configuration of the pass filter is not easy.

Next, as a second problem to be solved for the heterodyne type signal selection circuit device, as described above, when the highest frequency of the input signal group is higher than the conversion output frequency, the frequency conversion is performed twice and the double heterodyne type is selected. It is necessary to perform frequency conversion, and in a CATV system that outputs an input FM signal selected by frequency conversion to the BS-IF band, the number of transmission channels of a main system CATV that can be handled by single heterodyne frequency conversion is 26 channels or less. Is limited to

(Means for Solving the Problems) An object of the present invention is to solve the above-described various problems in the related art, and to input signals arranged in an extremely wide frequency band without setting the oscillation frequency of a local oscillator to be high. No need to increase the bandwidth. It is an object of the present invention to provide a heterodyne type signal selection circuit device for demand access CATV, which can selectively convert a signal into a desired frequency band without causing signal deterioration due to mixing of unnecessary signals.

According to the present invention, as a measure for compressing the fractional band of the local oscillator in the heterodyne signal selection circuit device, the occupied band of the input signal group is divided into two equal parts, the input signal group in one half band is subjected to frequency conversion, and In which the converted input signal group and the original input signal group in the same half band are switched by a high-frequency switch to select one of the desired input signals. If the carrier frequencies in the two groups completely match, the crosstalk between the input signals caused by the leakage of one group of input signals into the other group of input signals is caused by the carrier frequency in the input signals of both groups. Are shifted by half the frequency interval of the input signal array so that even if crosstalk occurs, the selected input signal is not substantially adversely affected. Than it is.

That is, the double heterodyne signal selection circuit device of the present invention selects a signal of a desired channel from an input signal group of a plurality of channels arranged at predetermined frequency intervals in a predetermined frequency band with a guard band secured between each channel, and outputs a desired frequency. A circuit device for converting the signal into a signal and outputting the signal, wherein the filtering and dividing means for dividing the input signal group of the plurality of channels into one and the other divided input signal groups of substantially the same plurality of channels according to the level of a frequency band; A frequency converter for converting an input signal of each channel in the one distributed input signal group into a distributed input signal group of a conversion channel, and a distributed input signal group of the converted channel which is an output signal of the frequency converter; High-frequency switching means for selectively switching between a distribution input signal group and the conversion switch which is a switching output signal of the high-frequency switching means. Double heterodyne signal selection circuit device comprising signal selection conversion means for selecting a signal of a desired channel from one of the distributed input signal group of the channel and the other distributed input signal group, converting the signal into an output signal of a desired frequency, and outputting the output signal. In the frequency converter, the input signal of each channel in the one distributed input signal group is substantially equal to the predetermined frequency interval with respect to the input signal of each channel in the other distributed input signal group. It is characterized by being converted into a distribution input signal group of a conversion channel having a sequentially shifted frequency band.

(Operation) Therefore, in the double heterodyne signal selection circuit device of the present invention, a large number of channels arranged in a wide band without deteriorating the signal quality by using an easily configured local oscillator that does not need to particularly widen the fractional band. From the input signal group, the input signal of the desired channel can be selectively converted into a frequency band that can be easily received and output, and is generated by a changeover switch unit that switches between the frequency-converted signal and the other signal. Crosstalk can be significantly reduced.

(Embodiments) The present invention will be described in detail below with reference to embodiments with reference to the drawings.

First, FIG. 1 shows a configuration example of a so-called hub in the demand access type CATV of the signal selection circuit device of the present invention, that is, a signal selection circuit device having an exchange function.
In the configuration example shown in FIG. 1, for simplicity of explanation, the number of transmission channels of the main system CATV is assumed to be 40, and the carrier frequency of the FM signal transmitted by those channels is set to the first frequency of the outdoor unit of the satellite broadcasting receiver outdoor unit. Intermediate frequency band or BS
Based on eight IF band (1.3 GHz band) channels, it is assumed that the array is arranged with the same frequency interval of 38.36 MHz as the satellite broadcast channel interval from the lowest frequency of 52.12 MHz. In addition, main line system
Of FM signal group to be transmitted in CATV, the carrier frequency of the FM signal transmitted by the K-th channel counted from the lower of the carrier frequency and f _K, to be represented by a frequency interval △ f.

Now, among the FM signal group 40 channels as described above, the higher of 20 channel FM signal groups having the carrier frequency f ₂₁ to f _40, lower 20 channel FM signal having a carrier frequency f ₁ to f ₂₀ of A description will be given of a configuration example shown in FIG. 1 in a case where each of the frequency bands is down-converted to a frequency band higher by half the frequency interval Δf, that is, by Δf / 2 than the group.

In the configuration example shown in FIG. 1, an FM signal group of 40 channels having the same specifications as that of the satellite broadcasting arranged at the same frequency interval of 38.36 MHz as that of the satellite broadcasting from the signal source 1 is guided to the two-way splitter 2.
The frequency band of the input FM signal group of 40 channels is divided into two equal parts according to the level of the frequency. Among the divided outputs of the two divider 2, the FM signal group for 20 channels in the lower frequency band is guided to one switching input terminal of the high-frequency switch 7 via the low-pass filter 3, and the higher frequency The FM signal group corresponding to 20 channels in the frequency band of (1) is guided to the frequency converter 5 via the high-pass filter 4, and the oscillation output of the local oscillator 6 having a local oscillation frequency f _LO = 1619.46 MHz is applied. The converted output FM signal group of the 20 channels is led to the other switching input terminal of the high frequency switch 7.

The FM signal group for each of the 20 channels guided to both switching input terminals of the high-frequency switch 7 as described above is the first signal.
Like the spectrum shown separately at the top and bottom of the figure,
All are arranged in the lower half-frequency band at the frequency interval 12 of the main system CATV, and in the upper spectrum, the lowest carrier frequency 13
(F ₁ = 52.12 MHz) to the 20th carrier frequency 14 (f ₂₀ = 7
80.96MHz) is 20 channel array up, in the spectrum of the lower, of the FM signal group of the mains system CATV, half the frequency interval than the minimum carrier frequency f ₁ 19.18MHz only high carrier frequency 15 (f _LO -f ₄₀ = 71.30MHz)
From the 20th channel, a carrier frequency 16 (f _{LO) that} is half the frequency interval 19.18 MHz higher than the _20th carrier frequency f ₂₀
20 channels up to the 21st channel converted to −f ₂₁ = 800.14 MHz) are arranged.

The switching output FM signal group of the high-frequency switch 7 that selects one of the two FM signal groups is guided to the frequency converter 8, and the oscillation output of the local oscillator 9 having a variable frequency is applied to the FM signal group. The FM signal of the desired channel is selected by the heterodyne method, and passed through a bandpass filter 10 having a bandwidth of 27 MHz corresponding to the desired channel in the BS-IF band.
Subscriber BS receiver indoor unit 11 as selected output FM signal
To supply.

The configuration example shown in FIG. 1 shows a case where only the desired one-channel FM signal of the selected output is supplied to the subscriber's BS receiver indoor unit. The number of channels that can be selectively received is such that, considering direct observation and recording of a back program by a VTR or the like, it is possible to simultaneously supply the FM signal of the heterodyne system selection output to a plurality of channels in the BS-IF band. It is desirable to make. In such a case, for example, it is suitable for use in a hub of a demand access type CATV, which is capable of selecting, for example, any desired four channels of FM signals from a multi-channel FM signal group in a trunk line CATV and simultaneously transmitting them. FIG. 2 shows a configuration example of the double heterodyne signal selection circuit device of the present invention. In the configuration example shown in FIG. 2, the indoor unit of the BS receiver of each subscriber is a BS-BS in the BS-IF band.
1 channel, BS-5 channel, BS-9 channel and BS
It is assumed that the frequency division multiplexing FM signal composed of four channels A to D of the subscriber CATV to which -13 channels are respectively allocated is selectively received, and the four systems of the selection circuit in the hub are respectively CH-A, CH-B, They will be represented as CH-C and CH-D.

The configuration from the signal source 1 to the output end of the low-pass filter 3 and the output end of the frequency converter 5 in the configuration example shown in FIG. 2 is exactly the same as in the configuration example shown in FIG. Thus, in the configuration example shown in FIG. 2, the low-pass filter 3 in the lower half frequency band is used.
The FM signal group for the original 20 channels from the frequency converter 5 is guided to the 4-divider 17, and the converted output FM signal group for the 20 channels from the frequency converter 5 is guided to the 4-divider 18. Note that these FM signal groups are arranged according to the spectrum shown in the upper and lower parts of FIG.

The output signals of the four dividers 17 and 18 are respectively guided in parallel to the respective switching input terminals of the four high-frequency switches 19 to 22, and the desired FM signal group is extracted as the switching output signal. , Four selected output transmission channels CH-A, CH-B, CH-C, CH in the above-described subscriber CATV.
The frequency converters 23, 26, 29, and 32 corresponding to −D respectively guide the FM signals of the desired channels in each input FM signal group by the local oscillation outputs of the variable frequency local oscillators 24, 27, 30, and 33. The selected output transmission channels are converted into CH-A to CH-D, respectively, and the BS-1 channel having a bandwidth of 27 MHz (1,049.48
MHz), BS-5 channel (1,126.20 MHz), BS-9 channel (1,202.92 MHz), and BS-13 channel (1,279.64 MHz) band-pass filters 25,28,31,34 in parallel with the four combiner 35 respectively. And the four transmission channels CH-A to D
And outputs the selected output FM signal to the indoor unit 11 of the subscriber's BS receiver as a subscriber system CATV signal.

FIG. 3 shows an example of a schematic configuration of a demand-access type optical CATV system using the signal selection circuit device of the present invention having the configuration shown in FIG. In the effect CATV system shown in FIG. 3, a service FM signal group for 40 channels from the signal source 1 in the head end 36 of the main line CATV is converted into a carrier optical signal by the electro-optical converter 37, and the main line CATV optical fiber The signal is guided to the photoelectric converter 39 via 38, and is returned to the FM signal group for 40 channels. The two dividers 2, the frequency converter 5 and the local oscillator 6 provide two groups of 20 channels each having 20 channels in the same half frequency band. The FM signals of each group are supplied in parallel to n subscriber hubs 40-1 to 40-n.

In each subscriber hub, for example, the hub 40-1, as shown, two groups of incoming FM signals are guided to two quadrants 17 and 18, respectively, to transmit the subscriber system CATV transmission channel CH-.
Four high-frequency switches 19 to 22 corresponding to A to D respectively
, And selectively fetches a desired group of FM signal groups for each transmission channel, and supplies them to the selection circuits 41 to 44, respectively. Each of the selecting circuits 41 to 44 selects the FM signal of the desired transmission channel from the incoming FM signal group by the heterodyne method, and respectively selects the BS-1, CH-5, BS-9, and BS-9 channels. The frequency is converted to an FM signal of -13 channels and supplied to the 4-combiner 35 in parallel. In the four combiner 35, the FM signals of the four transmission channels CH-A to CH-D are frequency-division multiplexed, guided to an electro-optical converter 45 for transmitting a down-link video signal, converted into a carrier light signal, and converted into a carrier signal. The signal is supplied to the subscriber BS receiver indoor unit 11-1 corresponding to the subscriber hub 40-1 via the CATV optical fiber 49-1. Each subscriber unit 11-1 ~
n, for example, in the subscriber unit 11-1, the incoming carrier optical signal is guided to the subscriber down-link video signal photoelectric converter 51 via the optical demultiplexer 50 as shown in FIG. The received signal is supplied to the 4-divider, and the divided output signal is supplied to the BS-1 channel receiving circuit 53, the BS-3 channel receiving circuit 54, the BS-9 channel receiving circuit 55, and the BS-13 channel receiving circuit. Supply to 56 respectively.

On the other hand, a program request signal from each of the subscriber units 11-1 to 11-n, for example, the subscriber unit 11-1, includes an encoder 57 and an electro-optical converter 58 for an uplink request signal, an optical demultiplexer 50, and a subscriber optical system. The fiber 49-1 is sequentially guided to the subscriber hub 40-1, and supplied to the request signal decoder 48 via the optical demultiplexer 46 and the uplink request signal photoelectric converter 47, and the decoded output thereof is provided. Each of the high-frequency switches 19 to 22 and each of the selection circuits 41 to 44 are controlled by signals to selectively transmit a program signal corresponding to a request for each of the transmission channels CH-A to CH-D.

Therefore, in the demand access type optical CATV system configured based on the present invention as shown in FIG.
To each subscriber unit, a program signal of any desired service channel can be simultaneously supplied according to each request without causing interference with each other.

In the signal selection circuit device according to the present invention which enables such a demand access type information service, for example, a signal array having a frequency interval of 38.36 MHz arranged in a frequency band including a BS-IF band is used.
Selectively frequency-convert FM signals of any desired four service channels from the frequency division multiplexed FM signals of the channels and perform BS-
Table 1 shows the local oscillator oscillation frequencies in the selection circuits 41 to 44 when transmitting to the predetermined four transmission channels CH-A to CH-D in the IF band.

The carrier frequency f _k of the k-th service channel from the lowest channel f ₁ in the service FM signal group of, for example, 40 channels in the trunk system CATV can be expressed by the following formula (1) if the frequency interval of each channel is Δf. ) Can be expressed as

f _k = f ₁ + (k−1) · △ f (1) However, a local oscillator for down-converting the carrier frequency f ₄₀ of the highest channel to a frequency 0.5 △ f higher than the carrier frequency f ₁ of the lowest channel. 6 oscillation frequency
f _lo is given by the following equation (2).

f _lo = 2 · f ₁ + (40−0.5) · Δf (2) Also, FM of 20 channels in the lower half frequency band
K-th from the lowest channel of the 20-channel FM signal group in the higher half-frequency band, which down-converts the carrier frequency f _k of the k-th channel from the lowest channel of the signal group to a frequency higher than the carrier frequency f _k by 0.5 △ f. The carrier frequency f _ck of the channel can be expressed by the following equation (3).

f _ck = f ₁ + (40−k + 0.5) · Δf (3) On the other hand, each transmission channel CH-A to
BS-1 channel, BS-5 channel, BS-9 corresponding to D
The center frequency of the channel and the center frequency of the BS-13 channel can be expressed by the following equation (4).

Therefore, for example, the transmission channel CH-A in the subscriber CATV, that is, the FM of any desired service channel selected by the heterodyne method on the BS-1 channel.
For sending a signal, the oscillation frequency f _v of the variable frequency local oscillator 24, when selected according to FM signal of the k th carrier frequency f _k from the lowest channel request in high and low half-frequency band, Each can be expressed as in the following equation (5).

When 1 ≦ k ≦ 20: f _v = 2 · f ₁ + ｛26+ (k−1)｝ · △ f (5) When 21 ≦ k ≦ 40: f _v = 2 · f ₁ + ｛40 + 26−k + 0 .5｝ · △ f In Table 1 above, the required frequency variable width in the frequency variable local oscillator for channel selection is shown in the form of a fractional band (%). Compared with the conventional signal selection circuit device using the double heterodyne frequency conversion in the same manner, the required band of the first frequency conversion output signal is arranged next to the first frequency converter in the double heterodyne frequency conversion of the conventional device. Are selectively passed through the center frequencies of the bandpass filters 1,865.88 MHz, 1,789.16 MHz, 1,764.56 MHz for the transmission channels CH-A to CH of the subscriber CATV, respectively.
Hz, 1,635.72M Hz, each fractional band is 56.12
%, 57.78%, 59.54%, 61.42%, and the corresponding fractional bandwidth of the device of the present invention is 42.4% as shown in Table 1.
From 9% to 49.72%, it can be seen that the fractional bandwidth of the device of the present invention is much narrower than before.

(Effects of the Invention) As is clear from the above description, according to the present invention, the oscillation frequency variable width or the ratio band of the local oscillator in the signal selection circuit device using the double heterodyne frequency conversion is much higher than in the past. In addition to being able to easily and inexpensively produce a frequency-variable local oscillator essential for signal selection,
Since the oscillation frequency of the local oscillator can be set low, it is possible to expect improvements in various characteristics such as isolation required for the frequency converter.
Since the use of an IC or the like becomes possible, the overall cost of the circuit device can be further reduced.

Furthermore, comparing the required number of frequency converters with the conventional device, the conventional signal selection circuit device shows that the trunk line CATV
If the number of service channels exceeds 27 and the FM signal group is arranged in a frequency band higher than the BS-IF band, it is necessary to perform double heterodyne frequency conversion as described above. Assuming that the number of subscribers to be serviced is N and each subscriber is provided with M channels, the minimum required number of frequency converters required for the conventional double heterodyne frequency conversion is (M + 1) · In contrast to N, 1 + M · N is sufficient in the device of the present invention, and the result is extremely large considering the miniaturization of the subscriber hub.

Note that, in the signal selection circuit device of the present invention, the frequency band in which the FM signal group is arranged is divided into two equal parts, high and low.
When performing frequency conversion of the signal group to the other half band, if the arrangement of the FM signal group in both half bands is shifted by half of the frequency interval, crosstalk between both half bands is significantly reduced, so that the crosstalk is large. It is possible to selectively switch between the two half bands using an inexpensive high frequency switch. That is, in satellite broadcasting, the signal bandwidth is 27 MHz.
Since the FM signal channels of z are arranged at a frequency interval of 28.36 MHz, the guard band between the channels is 11.36 MHz. If the arrangement of the two FM signal channels selected by switch switching is shifted from each other by half of the frequency interval of 38.36 MHz, even if the FM signals belonging to both channel arrangements have overlapping signal bands, the FM signal Regarding the distribution of signal power, since the majority of the signal power is concentrated in the frequency shift region near the carrier, a significant reduction in crosstalk disturbance to the FM signal of the channel selected by switching should be expected. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a signal selection circuit device of the present invention, FIG. 2 is a block diagram showing another configuration example of the signal selection circuit device of the present invention, and FIG. 3 is a signal selection circuit device of the present invention. FIG. 1 is a block diagram showing a schematic configuration of a demand-access type optical CATV system using a system. 1 FM signal source 2 Divider 3 Low pass filter 4 High pass filter 5,8,23,26,29,32 Frequency converter 6,9,24,27,30,33 ... Local oscillators 7,19-22 ... High-frequency switches 10,25,28,31,34 Band-pass filters 11,11-1 -n ... Subscriber BS receiver indoor units 17,18,52 ... 4 Distributor 35 4 Synthesizer 36 CATV bed end 37,45,58 Electro-optical converter 38,49-1 to n CATV optical fiber 39,47,51 Photoelectric converter 40-1 n Subscriber hub 41-44 Selection circuit 46, 50 Optical demultiplexer 48 Decoder 53-56 Receiver circuit 57 Encoder

────────────────────────────────────────────────── (5) Continuation of the front page (56) References JP-A-50-137019 JP-A-3-263905 JP-A-4-35230 JP-A-55-87051 (58) Fields investigated (Int. Cl. ⁷ , DB Name) H03D 7/16 H04B 1/26

Claims (1)

(57) [Claims] 1. A signal of a desired channel is selected from a group of input signals of a plurality of channels arranged at predetermined frequency intervals in a predetermined frequency band with a guard band secured between respective channels, and is converted into an output signal of a desired frequency and output. A circuit device, comprising: a filtering and two-distribution unit for distributing the input signal group of the plurality of channels into one and the other divided input signal groups of a plurality of substantially identical channels depending on the level of a frequency band; and the one divided input signal group And a frequency converter for converting the input signal of each channel into a distribution input signal group of a conversion channel, and selecting a distribution input signal group of the conversion channel and the other distribution input signal group which are output signals of the frequency converter. High-frequency switching means for selectively switching, a distribution input signal group of the conversion channel, which is a switching output signal of the high-frequency switching means, and the other distribution input A signal selecting and converting means for selecting a signal of a desired channel from any one of the force signal groups, converting the signal into an output signal of a desired frequency, and outputting the output signal. The input signal of the channel is, in the frequency converter, a conversion channel having a frequency band sequentially shifted by approximately 1/2 of the predetermined frequency interval with respect to the input signal of each channel in the other divided input signal group. A double heterodyne signal selection circuit device which is converted into a distributed input signal group.