JPH05259930A - Receiving device - Google Patents

Abstract

PURPOSE:To increase the band of the receiving frequency by applying both upper and lower heterodyne detection systems and switching these systems to each other according to the received signal frequency. CONSTITUTION:An image cancel mixer 25 receives the upper or lower band of the local oscillation signal inputted to the mixer 25 from a local oscillation circuit 17 and cancels the other band as an image signal. The one of both bands that should be canceled is decided by the control signal received from a switch signal generating circuit 203 which receives the channel selection data given through a terminal 29 and produces a switch signal. At the same time, a base band signal is outputted from a terminal 14 via a polarity switching circuit 20 so that the different polarities of the upper and lower bands are matched with each other. The switching of the mixer 25 links to the switching of the demodulation output of the circuit 20. Thus both upper and lower bands of the oscillation signal can be received in a wide frequency band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for receiving a wide band signal including many channels,
For example, the present invention relates to a receiver (broadband reception front end) that is convenient for receiving a wideband signal handled in an optical image distribution system or the like that transmits a multiwave signal using the FM-FDM system.

[0002]

2. Description of the Related Art Optical video distribution systems for transmitting multi-channel video signals and the like in the form of optical signals are known. Among them, the optical video distribution system using the FM-FDM system is an existing AM-FDM system. Compared to that of the system, it is strong against noise and distortion, and multi-channel transmission is possible,
Currently being actively researched (for example, the paper presented at the 1990 National Conference of the Institute of Electronics, Information and Communication Engineers, B-71).
Please refer to 4, Examination of optical image distribution system, etc.).

However, most of the research is related to the optimization of the optical modulation / demodulation system and the optical transmission system, and the broadband optical demodulation signal (20 to 1700 MHz, 500 to 23).
A wideband reception front-end device capable of selecting and demodulating a desired signal from (00 MHz, etc.) has not been sufficiently studied, and for example, an IC receiver as disclosed in Japanese Patent Laid-Open No. 3-27625 has been proposed. Like the front-end devices seen, the widening of the receiver was not considered.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a mixer circuit and a local part for receiving and selecting a wide band signal as a wide band receiving device capable of selecting and demodulating a desired signal from a wide band optical demodulation signal. An object of the present invention is to provide a wide band receiving device having a small size and a simple structure by simplifying an oscillator circuit and improving performance.

Further, in the optical image distribution system using the FM-FDM system, it is a wide band receiving device which can be used also as a front end device for receiving and demodulating a desired signal from a wide band optical demodulated signal, which is small in size. It is an object of the present invention to provide a simple structure.

[0006]

To achieve the above object, the present invention takes the following means. That is, in order to receive and select a wideband signal, the frequency range of the local oscillation signal supplied to the mixer circuit is inevitably wide, and one local oscillation circuit cannot cover the frequency range as it is, and a plurality of them may be required. Since it is large in size, measures have been taken so that only one local oscillator circuit is required.

The means are as follows. That is, in a super-heterodyne receiver as a wideband receiver, a method of arranging and receiving a local oscillation signal on the upper side of a received signal (upper heterodyne method) and a local oscillation signal on the lower side of the received signal are arranged. We decided to use the method of receiving the signal (lower heterodyne method) depending on the frequency of the received signal.

Accordingly, if the number of receiving channels is the same, the required bandwidth of the local oscillation signal is narrow, and if the required bandwidth of the local oscillation signal is the same, the number of receiving channels can be increased. In addition, an image cancel mixer that removes the image signal is used in the mixer circuit.When the signal is received by the upper heterodyne method, the signal on the upper side of the local oscillation signal is canceled, and conversely by the lower heterodyne method. When receiving the signal, the signal below the local oscillation signal is canceled.

Further, since the polarity of the demodulation output signal changes between when the lower side signal of the local oscillation signal is received and when the upper side signal is received, the lower side signal is received in order to receive this normally. It was decided to invert the polarity of the demodulated output signal depending on whether it was received or the upper signal was received.

[0010]

As an mixer circuit of the receiver, an image cancel mixer for removing the image signal is used. When selecting the lower side signal of the local oscillation signal, the upper side signal is canceled and vice versa. When the upper signal of the local oscillation signal is selected, the lower signal can be canceled to receive both the upper and lower signals of the oscillation signal. It is possible to receive a wider frequency band than a system in which only one of the two signals is received.

Further, when the modulation method of the received signal is FM modulation, the polarities of the detection output are reversed between the lower side reception and the upper side reception of the oscillation signal. To With this configuration, a receiver capable of wideband reception can be obtained with a simple and compact configuration.

[0012]

1 is a block diagram showing the structure of a first embodiment of the present invention. That is, it is a block diagram showing a configuration of a receiving device capable of wideband reception, which can be used also as a reception front-end device in a wideband signal transmission system such as an optical image distribution system.

In the figure, reference numeral 1 denotes an RF signal input terminal,
2 is a demultiplexer, 3a to 3d are switching circuits as image filters, 9 is an RF gain control circuit, 10 is a mixer circuit, 1
1 is a gain control circuit, 12 is a SAW filter, 13 is a demodulation circuit, 14 is an output terminal, 17 is a local oscillation circuit, 18 is a frequency dividing circuit, 20 is a polarity switching circuit, 28 is a tuning circuit, and 29 is tuning data. Input terminals, 201 and 202 are switching signal generating circuits, SW is a switch, INV is an amplitude inverting circuit,
Is.

Next, the circuit operation will be described with reference to FIG.
A wideband RF signal (for example, 0.
5 to 2.3 GHz) is demultiplexed into a plurality of bands by the demultiplexer 2, and the signals in the respective bands are input to the switching circuits 3a to 3d configured by the RF amplification circuit and the like.

In the switching circuits 3a to 3d, only one switching circuit is turned on by the switching signal generated by the switching signal generation circuit 201 according to the tuning data input from the tuning data input terminal 29, and the other switching circuits are turned on. It is turned off, and as a result, one band is selected from a plurality of output bands from the demultiplexer 2.

Here, when the output of the demultiplexer 2 is four, the four output bandwidths are, for example, 0.5 to 1.0 GH.
z (band 1), 1.0 to 1.5 GHz (band 2), 1.
5 to 2.0 GHz (band 3), 2.0 to 2.3 GHz
Set to about (band 4), and unnecessary waves such as image signals
It is assumed that this demultiplexer can sufficiently suppress.

Next, switching circuits (RF amplification circuits) 3a to 3d.
Are combined and input to the RF gain control circuit 9.
The signal gain-controlled by the RF gain control circuit 9 is mixed by the mixer circuit 10 with the oscillation signal input from the local oscillation circuit 17 and output as an intermediate frequency signal (for example, 402 MHz).

Here, the structure of the local oscillator circuit 17 will be described. For example, the mixer circuit 10 is 0.5 to 2.3 GH
In the case of a circuit that converts an RF input signal of z into an intermediate frequency signal of 402 MHz, the oscillation circuit that supplies a local oscillation signal to the mixer circuit 10 needs a frequency variable width of 0.9 to 2.7 GHz or more. Become.

Since it is very difficult to stably obtain a wide oscillation band by direct oscillation as described above, the present invention switches the upper heterodyne system and the lower heterodyne system according to the reception band to receive the oscillation band. The whole range between the lower limit and the upper limit of is set to be narrower than that in the other case.

For example, the above band 1 (0.5 to 1.0 G
Hz) and band 2 (1.0 to 1.5 GHz), the upper heterodyne system is used, and the local oscillation frequency variable width needs to be 0.9 to 1.9 GHz.
On the other hand, when receiving the signals in the band 3 (1.5 to 2.0 GHz) and the band 4 (2.0 to 2.3 GHz),
The lower heterodyne system is used, and the local oscillation frequency variable width needs to be 1.1 to 1.9 GHz.

Therefore, the oscillation frequency of the oscillation circuit 17 is set to 0.
If designed at 9 to 1.9 GHz, 0.5 to 2.3 GHz
Can receive all input RF signals of This has an effect of significantly reducing the variable width as compared with the conventional oscillation frequency variable width of 0.9 to 2.7 GHz using only the upper heterodyne method. In other words, with the same oscillation frequency variable width as in the conventional method, there is an effect that the reception band can be widened.

The configuration after the oscillation circuit and the mixer circuit in FIG. 1 will be described below. The oscillation signal from the oscillation circuit 17 is frequency-divided by a frequency dividing circuit (prescaler) 18, and the frequency-divided signal is input to a channel selection circuit 28 and a terminal 29.
The oscillating frequency of the local oscillating circuit 17 is controlled by the tuning data and the frequency-divided signal input from the tuning circuit 28 to the tuning circuit 28.

Next, the intermediate frequency signal output from the mixer circuit 10 is amplified and gain-controlled by the IF gain control circuit 11, then band-limited by the SAW filter 12, input to the FM demodulation circuit 13, and output to the base. After the FM demodulation into a band signal, it is input to the polarity switching circuit 20 of the base band signal.

Since the FM demodulation output has different polarities depending on whether the channel selection system is the upper heterodyne system or the lower heterodyne system, the polarity switching circuit 20 makes the polarities the same and outputs the baseband signal from the terminal 14. In the polarity switching circuit 20, the switch SW is switched by the switching voltage from the switching signal generating circuit 202 which receives the channel selection data input from the terminal 29 and generates the switching signal.
The polarity of the base band signal output from the switch 4 is switched.

The switching of the polarities is performed in conjunction with the above-mentioned reception band switching. F
A gain control voltage corresponding to the input signal level is output from the M demodulation circuit 13, and the RF gain control circuit 9 and the IF gain control voltage are output.
A gain control voltage is applied to the gain control circuit 11.

The present receiver is a system suitable for use as an IC. For example, the band switching circuits 3a to 3d are composed of RF amplifier circuits and the like, and GaAs is excellent in high frequency characteristics and distortion characteristics.
IC is formed using MES FET. Further, separately from that, by composing the RF gain control circuit 9, the mixer circuit 10, and the IF gain control circuit 11 on one IC, a small IC front end excellent in high frequency characteristics and distortion characteristics can be obtained. ..

According to the present invention, the upper heterodyne system and the lower heterodyne system are switched in accordance with the reception band to receive signals, so that a wide range input signal with a narrower oscillation frequency variable width than the conventional system is received. Can be received.

In the description of the present embodiment, the input signal band is divided into four, but the dividing method is not limited to this, and the same effects as those described above can be obtained with other dividing methods.

FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention. In the figure, the same parts as those in FIG. 1 and the corresponding parts are designated by the same reference numerals. In addition, 21 is a switching circuit.

This embodiment will be described below with reference to FIG. 2. The circuit operation is almost the same as that of the first embodiment previously performed with reference to FIG. The difference is that the local oscillator circuit 1
Since this is an operation related to No. 7, that point will be described below.

In the present embodiment, the oscillation signal obtained from the local oscillation circuit 17 is switched to the fundamental wave and the half frequency according to the received RF signal and used to cover a wide oscillation band.

For example, if the oscillation frequency of the local oscillator circuit 17 is designed to be 0.9 to 1.9 GHz, the band 1 (0.0
2 to 0.6 GHz), band 3 (1.2 to 1.8 GHz)
At the time of reception, the signal is divided into two bands (0.45 to 0.95 GHz) and the fundamental wave (0.9 to 1.9 GHz), and the band 2
(0.6 to 1.2 GHz), band 4 (1.8 to 2.3 GHz)
(Hz) can be received at the fundamental wave (0.9 to 1.9 GHz).

Therefore, the output of the local oscillator circuit 17 is input to the frequency divider 18 to divide the local oscillator circuit 17 and the frequency divider 1 into two.
The output of 8 is a switching voltage from a switching signal generation circuit 201 which generates a switching signal by receiving the tuning data input from the terminal 29, one of which is selected by the switching circuit 21 of the fundamental wave and the divided frequency. The fundamental wave or the dichotomized frequency output from the switching circuit 21 is input to the mixer circuit 10.

The oscillation signal from the oscillation circuit 17 is frequency-divided by a frequency dividing circuit (prescaler) 18, the frequency-divided signal is input to a channel selection circuit 28, and is input from a terminal 29 to the channel selection circuit 28. The oscillating frequency of the local oscillating circuit 17 is controlled by the tuning data and the frequency division signal.

The fact that this receiving apparatus is a system suitable for IC implementation is the same as in the first embodiment described with reference to FIG. In this embodiment, the local oscillator circuit has a fundamental wave,
By switching the halving frequency, it is possible to obtain an oscillation circuit having a wide oscillation frequency variable width with a simple configuration.

FIG. 3 shows that the upper side of the RF signal is selected as the upper heterodyne detection system or the lower frequency side, which is the point of the embodiment of the present invention described with reference to FIGS. 1 and 2. FIG. 6 is a diagram for explaining the principle of determining whether to use the lower side heterodyne detection method by selecting.

Referring to FIG. 3 (a), (b),
In (c), the horizontal axis represents frequency f and the vertical axis represents power P. FIG. 3A shows a general upper heterodyne reception method, and the reception signal band fs1 to fs1.
A variable width of the local oscillation frequency (fL2-fL1) for receiving the signal of fs2 and converting it to the intermediate frequency signal fif
Indicates that it is necessary to change only the reception bandwidth (fs2-fs1).

On the other hand, FIG. 3B shows that the lower heterodyne receiving system is used for the lower frequency and the lower heterodyne receiving system is used for the higher frequency. As a result, the variable range of the local oscillation frequency (fL2-
fL1) requires (fs2-fs1-2fif), and the oscillation frequency variable width can be reduced by 2fif as compared with the method of FIG.

However, in FIG. 3B, (fL2-fL
When 1) <2fif, the oscillation frequency variable width is fL with respect to the reception signal band fs3 as shown in (c) of FIG.
3 newly occurs on the right side higher than fL2, and fL
In some cases, it is necessary to oscillate up to 3 (fL3
-FL1) is required. Also in this case, the oscillation frequency variable width is smaller than that of the method of FIG.

As described above, according to the method of FIGS. 3B and 3C, which should be called the principle of the present invention, the required oscillation frequency variable width of the local oscillation circuit can be reduced.
This is an effective method for a broadband receiving system such as an optical CATV.

FIG. 4 is a block diagram showing the configuration of the third embodiment of the present invention. It goes without saying that this embodiment is also an embodiment of a wide band receiving device that can be used as a reception front end device in a wide band signal transmission system such as an optical image distribution system.

In FIG. 4, the same or corresponding parts as those in FIG. 1 are designated by the same reference numerals. others,
Reference numeral 24 is an amplifier circuit, 25 is an image cancel mixer circuit, and 203 is a switching signal generation circuit.

Hereinafter, this embodiment will be described in detail with reference to FIG. A broadband RF signal (for example, 0.5 to 2.3 GHz) input from the terminal 1 is amplified by the amplifier circuit 24, gain-controlled by the gain control circuit 9, and then input to the image cancel mixer 25. It

The image cancel mixer 25 receives either one of the upper side or the lower side of the local oscillation signal input from the local oscillation circuit 17 to the mixer 25 in the received signal band, and the other one. -Cancel as a signal. Which one of the upper side and the lower side of the local oscillation signal should be canceled determines whether the channel selection data input from the terminal 29.
Switching signal generating circuit 2 for receiving a switching signal and generating a switching signal.
It is controlled by a control signal (switching signal) from 03.

For example, received signal band 0.5 to 2.3 GH
z is 0.5 to 1.5 GHz (band 1) and 1.5 to 2.3.
It is divided into two bands of GHz (band 2), and when the reception signal band is 0.5 to 1.5 GHz, the local oscillation signal is arranged on the upper side of the reception signal band (upper heterodyne system) and the upper side of the local oscillation signal. Is canceled as an image signal by the mixer 25, while the received signal band 1.
In the case of 5 to 2.3 GHz, the local oscillation signal is arranged below the reception signal band (lower heterodyne system), and the signal below the local oscillation signal is used as an image signal to the mixer 25.
To cancel the image.

In this case, when the band 1 is received, the oscillation frequency variable width is 0.9 to 1.9 GHz (intermediate frequency 40
0 MHz) is required, and when the band 2 is received, the oscillation frequency variable width is 1.1 to 1.9 GHz. When the bands 1 and 2 are combined, the overall oscillation frequency variable width is 0.9 to It becomes 1.9 GHz.

When the above band of 0.5 to 2.3 GHz is received by the general upper heterodyne system, the oscillation frequency variable width needs to be as wide as 0.9 to 2.7 GHz. Effective for reduction. In other words, it can be seen that the reception band can be widened with the same oscillation frequency variable width as the conventional one.

The intermediate frequency signal output from the image cancel mixer 25 is input to the demodulation circuit 13 via the intermediate frequency filter 12 and demodulated into a baseband signal. The baseband signal output from the demodulation circuit 13 is
The band 1 reception (upper heterodyne system) and the band 2 reception (lower heterodyne system) have different polarities,
In order to match the polarities, the terminal 1 via the polarity switching circuit 20
4 outputs a baseband signal.

The switching control signal of the switching circuit 20 is a control signal (switching signal) from the switching signal generating circuit 202 which receives the tuning data input from the terminal 29 and generates a switching signal. The switching of the cancel mixer 25 and the polarity switching of the demodulation output in the switching circuit 20 are performed in conjunction with each other.

In order to control the oscillation frequency, the oscillation signal from the local oscillation circuit 17 is divided by the frequency dividing circuit 18, and this frequency divided signal is input to the channel selecting circuit 28 and is input from the terminal 29 to the channel selecting circuit 28. The oscillation frequency of the local oscillation circuit 17 is controlled by the input tuning data and the divided signal. Next, the FM demodulation circuit 13 outputs a gain control voltage according to the input signal level, and the gain control voltage is applied to the RF gain control circuit 9.

The present receiver is a system suitable for use as an IC. For example, the RF amplifier circuit 24, the gain control circuit 9, the image cancel mixer 25, the local oscillator circuit 17, etc. are excellent in high frequency characteristics and distortion characteristics. GaAs MES FET
By using the IC to make an IC, a small-sized IC front end having excellent high-frequency characteristics and distortion characteristics can be obtained.

According to this embodiment, an image cancel mixer is used in the mixer circuit, and either the upper side signal or the lower side signal of the local oscillation signal is canceled as an image signal according to the switching control signal. As a result, there is an effect that the oscillation frequency variable width can be reduced or the reception band can be widened, as compared with the conventional method of canceling only one specific one of the oscillation signals.

FIG. 5 is a block diagram showing the configuration of the fourth embodiment of the present invention. In the figure, the same parts as those in FIG. 4 and the corresponding parts are designated by the same reference numerals. Besides, 21 is a switching circuit.

This embodiment will be described below with reference to FIG. 5, but the circuit operation is almost the same as that of the third embodiment previously performed with reference to FIG. The difference is that the local oscillator circuit 1
Since this is an operation related to No. 7, that point will be described below.

The oscillation frequency variable width required in the receiver of this embodiment is 0.42 to 1.9 GHz, as already described.
However, in the present embodiment, the oscillation signal obtained from the local oscillation circuit 17 is switched to the fundamental wave and the half frequency according to the received RF signal and used to cover a wide oscillation band. ..

For example, if the oscillation frequency of the local oscillator circuit 17 is designed to be 0.8 to 1.9 GHz, a binary frequency (0.4 to 0.9) when the input RF signal is 0.02 to 0.4 GHz.
5 GHz) and the input RF signal is 0.4 to 2.3.
At the time of GHz, the fundamental wave can be received.

For this purpose, a switching circuit 21 for the fundamental wave and the divided frequency is arranged in the subsequent stage of the local oscillation circuit 17, and switching is performed by a switching control signal supplied from a switching signal generation circuit 202. The fundamental wave or the doubled wave output from the switching circuit 21 is input to the mixer circuit 25.

The oscillation signal from the local oscillation circuit 17 is frequency-divided by the frequency dividing circuit (prescaler) 18, the frequency-divided signal is input to the channel selecting circuit 28, and the terminal 29 selects the channel selecting circuit 2.
The oscillating frequency of the local oscillation circuit 17 is controlled by the tuning data and the frequency-divided signal input to the channel 8.

The fact that this receiving apparatus is a system suitable for use as an IC is the same as in the third embodiment described with reference to FIG. In this embodiment, the local oscillator circuit has a fundamental wave,
By switching the halving frequency, it is possible to obtain an oscillation circuit having a wide oscillation frequency variable width with a simple configuration.

FIG. 6 is a block diagram showing a concrete example of the image cancel mixer shown in FIGS. In FIG. 6, 17 is an oscillator, 102 is a first divider that divides the oscillation signal of the oscillator 17 into two, and 103 is a first 90-degree phase shifter that rotates the phase of one output signal of the divider 102 by 90 degrees. ,.

In addition, 104 is an input terminal, 105 is a second distributor that divides the signal input to the input terminal 104 into two, 106 is a first mixer (mixer), and 107 is a second mixer (mixer). ), 108 is a switching circuit, 23 is a terminal for applying a switching signal of the switching circuit 108, 110 is a second terminal for rotating the phase of one output signal of the first mixer 106 and the second mixer 107 by 90 degrees. The 90-degree phase shifter, 111 is a combiner, and 112 is an output terminal.

The operation for obtaining an intermediate frequency signal using an oscillation signal having a frequency higher than the input signal frequency will be described. The oscillation signal of the oscillator 17 is equally divided by the distributor 102, one output signal is input to the first mixer 106, and the other output signal is rotated by 90 degrees by the first 90-degree phase shifter 103. Input to the second mixer 107.

On the other hand, a desired signal is input from the input terminal 104, and is equally divided into two signals having the same phase or a phase difference of 180 degrees by the distributor 105, and the first mixer 106 and the second mixer 1 are connected.
Enter in 07. Hereinafter, the phase relationship of the signals mixed in the first mixer 106 and the second mixer 107 and appearing at the outputs (a) and (b) is divided equally by the second distributor 105 to obtain the desired signal. The case where the signals are in phase will be described with reference to FIG.

Desired signal fs and oscillation signal fos at this time
The frequency relationship between c and the image signal fim is as shown in FIG. 8A when the intermediate frequency signal frequency is fif. Therefore, as shown in FIG. 8C, the output (a)
Is the desired signal fs' converted to the intermediate frequency signal.
And the image signal fim appear in phase, and the desired signal fs "and the image signal fim" have a phase difference 180 at the output (b).
Appears in degrees.

Further, the desired signals fs 'and fim "appearing at the outputs (a) and (b), and the image signals fim' and fi are shown.
m ″ each have a phase difference of 90 degrees. The above phase relationship can be obtained even when the desired signal equally divided by the second distributor 105 has a phase difference of 180 degrees.

In FIG. 6, according to the control signal applied to the control terminal 23, the terminal 121 and the terminal 123, and the terminal 122 and the terminal 1
24 is connected. As a result, the signal appearing at the output (a) and the signal appearing at the output (b) that is 90 degrees phase-shifted by the second 90-degree phase shifter 110 are input to the combiner 111, and the image signal is canceled. In the meantime, only the desired signal can be taken out at the output terminal 112.

Next, the operation for obtaining an intermediate frequency signal using an oscillation signal having a frequency lower than the input signal frequency will be described. Desired signal fs and oscillation signal fos at this time
The frequency relationship between c and the image signal fim is as shown in FIG. 8B when the intermediate frequency signal frequency is fif. Therefore, as shown in FIG. The desired signal fs 'and the image signal fim' converted into the intermediate frequency signal appear in phase, and the desired signal fs "and the image signal fim" appear in the output (b) with a phase difference of 180 degrees.

The desired signals fs 'and fim "appearing at the outputs (a) and (b), and the image signals fim' and fi are shown.
m ″ each have a phase difference of 90 degrees. The above phase relationship can be obtained even when the desired signal equally divided by the second distributor 105 has a phase difference of 180 degrees.

According to the control signal applied to the control terminal 23 in FIG. 6, the terminals 121 and 124, and the terminals 122 and 12 are controlled.
Connect 5. As a result, the signal appearing at the output (b) and the signal appearing at the output (a) that is 90 degrees phase-shifted by the second 90-degree phase shifter 110 are input to the combiner 111, and the image signal is canceled. In the meantime, only the desired signal can be taken out at the output terminal 112.

As described above, in this example, the switching circuit 1
08, the signal appearing at the output (a) and the output (b)
Select either one of the signals appearing in
Since the signal can be input to the phase shifter 110, the image signal is used in both the receiving method using the oscillation signal higher than the desired signal and the receiving method using the oscillation signal having a frequency lower than the desired signal. Can be canceled out, and only the desired signal can be output.

By configuring the second 90-degree phase shifter 110 and the combiner 111 with the SAW filter 130,
There is an effect that the image signal canceling operation can be performed with a simple circuit configuration.

FIG. 7 is a block diagram showing another specific example of the image cancel mixer, and those having the same functions as those in FIG. 6 are designated by the same reference numerals.

Please refer to FIG. 7 and FIG. When the desired signal fs and the oscillation signal fosc have a relationship as shown in FIG. 8A, if the terminals 121 and 124 and the terminals 122 and 125 of the switching circuit 108 are connected, outputs (a) and (b) are output.
Desired signals fs' and fs "and an image signal fi
The phase relationship between m ′ and fim ″ is as shown in FIG.

Further, the desired signal fs and the oscillation signal fosc
Is in the relationship as shown in FIG. 8B, the terminals 121 and 123 of the switching circuit 108, and the terminals 122 and 1 of the switching circuit 108.
When 24 is connected, desired signals fs 'and fs "appearing at outputs (a) and (b) and image signals fim' and fim" are displayed.
The phase relationship of is as shown in (e) of FIG. For this reason,
The output (a) signal and the output (b) signal whose phase is rotated by 90 degrees by the second 90-degree phase shifter 110 are combined with each other by the combiner 1
By combining in 11, the same effect as that of FIG. 6 can be obtained.

FIG. 9 is a block diagram showing still another specific example of the image cancel mixer. In the figure, those having the same functions as those in FIG. 6 are designated by the same reference numerals. Reference numeral 113 is a third 90-degree phase shifter that rotates the phase of one signal from the distributor 105 by 90 degrees.

The desired signal fs and the oscillation signal fosc are shown in FIG.
(A), if the terminals 121 and 124 and the terminals 122 and 125 of the switching circuit 108 are connected, the desired signal f appearing at the outputs (a) and (b) is obtained.
The phase relationship between s ′ and fs ″ and the image signals fim ′ and fim ″ is as shown in FIG.

Further, when the desired signal fs and the oscillation signal fosc have a relationship as shown in FIG. 8B, the terminals 121 and 123, and the terminals 122 and 1 of the switching circuit 108.
When 24 is connected, desired signals fs 'and fs "appearing at outputs (a) and (b) and image signals fim' and fim" are displayed.
The phase relationship of is as shown in (e) of FIG.

Therefore, the output (a) signal and the second 90
By combining the signal of the output (b) whose phase is shifted by 90 degrees by the phase shifter 110 by the combiner 111, the same effect as that of FIG. 6 can be obtained.

FIG. 10 is a block diagram showing the fifth embodiment of the present invention. In the figure, those having the same functions as those in FIG. 4 are designated by the same reference numerals. Other 2
Reference numeral 05 is a switching signal generating circuit. This embodiment is an effective embodiment as a reception front-end device that can receive both a CATV system that transmits a wideband signal such as an optical video distribution system and a satellite broadcasting system.

The present embodiment will be described in detail below with reference to FIG. A wideband RF signal (for example, 0.5 to 2.3 GHz) input from the terminal 1 is input to the RF amplifier circuit 24. On the other hand, an intermediate frequency signal (for example, 1 to 1.3 GHz) of satellite broadcasting input from the terminal 1'is input to the RF amplification circuit 24 '.

The RF amplifier circuits 24 and 24 ′ are switching signals generated by the switching signal generating circuit 205 according to the tuning data input from the tuning data input terminal 29, and one RF signal.
The amplifier circuit is selected, the other RF amplifier circuits are turned off, and C
One band is selected from the ATV signal and the BSIF band. Outputs (either one) of the RF amplifier circuits 24 and 24 ′ are input to the RF gain control circuit 9.

The signal whose gain is controlled by the RF gain control circuit 9 is sent to the local oscillator circuit 1 by the image cancel mixer 25.
It is mixed with the oscillating signal inputted from 7 and outputted as an intermediate frequency signal (for example, 402 MHz). here,
The image cancel mixer 25 decides whether to cancel the upper signal of the oscillation signal as an image signal (upper heterodyne system) or the lower signal as an image signal (lower heterodyne system). The switching signal (control voltage) generated by the switching signal generation circuit 205 is controlled by the tuning data input from the tuning data input terminal 29.

For example, an RF input signal of 0.5 to 2.3 GHz is converted to 0.5 to 1.4 GHz (band 1), 1.4 to 2.
When dividing into two bands of 3 GHz (band 2) and receiving band 1, the upper heterodyne method is used and band 2
By using the lower heterodyne system when receiving the signal, the wideband signal can be received within a narrow range of the oscillation frequency variable width of 0.9 to 1.9 GHz.

Further, even when the satellite broadcast signal input from the terminal 1'is 0.95 to 2 GHz, the oscillation frequency variable width is 0 or less according to the present embodiment in which the upper heterodyne system and the lower heterodyne system are shared. It can be within 1.9 to 1.9 GHz.

The receiving apparatus of this embodiment is a system suitable for use as an IC. For example, the RF amplifier circuits 24 and 24 'are GaAs MES FETs excellent in high frequency characteristics and distortion characteristics.
To form an IC, and by further configuring the RF gain control circuit 9, the mixer 25, and the oscillator circuit 15 on one IC, the IC is small and excellent in high frequency characteristics and distortion characteristics.
A compliant front end is obtained.

According to the present embodiment, by sharing the upper and lower heterodyne systems, it is possible to receive a wideband signal with a narrow oscillation frequency variable width. In addition, a wide band optical image distribution system and a satellite broadcast receiving system can be selectively received by one receiver, and all can be shared except for the RF input circuit (input filter, RF amplification circuit). It is possible to obtain a small, high-performance, high-performance receiver.

[0087]

As described above, according to the present invention,
In a super-heterodyne receiver, a method of arranging and receiving a local oscillation signal above the received signal (upper side heterodyne detection method) and a method of arranging and receiving a local oscillation signal below the received signal (lower side) By using the heterodyne detection method) in combination and switching the detection method according to the reception signal frequency, it is possible to widen the reception frequency band.

Further, an image cancel mixer is used for the mixer circuit, and the image band to be canceled is switched according to the received signal band, so that a simple structure is obtained.
The reception frequency can be wide band.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a frequency diagram illustrating the operating principle of the present invention.

FIG. 4 is a block diagram showing a third embodiment of the present invention.

FIG. 5 is a block diagram showing a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a specific example of an image cancel mixer used in the present invention.

FIG. 7 is a block diagram showing another specific example of the image cancel mixer.

FIG. 8 is a frequency vector diagram for explaining the operation of the image cancel mixer.

FIG. 9 is a block diagram showing still another specific example of the image cancel mixer.

FIG. 10 is a block diagram showing a fifth embodiment of the present invention.

[Explanation of Codes] 2 ... Divider, 3 ... Switching Circuit, 9 ... Gain Control Circuit, 10 ...
Mixer, 11 ... Gain control circuit, 12 ... SAW filter,
13 ... FM demodulation circuit, 17 ... Local oscillation circuit, 18 ... Frequency divider circuit, 20 ... Polarity inversion circuit, 25 ... Image cancel mixer, 28 ... Channel selection circuit, 201, 202, 203, 2
05 ... Switching signal generation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toshio Nagashima, Toshio Nagashima, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Visual Media Research Laboratory, Hitachi, Ltd. (72) Masatoshi Ohsawa 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Incorporated company Hitachi Image Information System

Claims (5)

[Claims] 1. A demultiplexer that receives a received RF signal, demultiplexes it into a plurality of bands and outputs the demultiplexed signal, and a desired demultiplexing output from a plurality of demultiplexing outputs from the demultiplexer according to tuning data. A selection circuit for selecting, an RF gain control circuit that takes in the selected demultiplexed output and controls and outputs the gain, and a mixer circuit for converting the output of the gain control circuit into an intermediate frequency signal In a receiver for demodulating a desired signal according to the tuning data from an RF signal and outputting it as a baseband signal, a local oscillation signal supplied to the mixer circuit for tuning the desired signal according to the tuning data. The frequency of is selected to a higher frequency side than the received RF signal as the desired signal to be the upper heterodyne detection method, or to the lower frequency side to be the lower heterodyne detection method, according to the tuning data. , And the baseband signal after channel selection and demodulation, depending on the detection method determined by the detection method determination means, with its polarity inverted or not inverted. A receiving device comprising: a polarity inversion selection circuit for outputting. 2. A demultiplexer that receives a received RF signal, demultiplexes it into a plurality of bands, and outputs the demultiplexed signal, and a desired demultiplexer output from a plurality of demultiplexer outputs from the demultiplexer according to tuning data. A selection circuit for selecting, an RF gain control circuit that takes in the selected demultiplexed output and controls and outputs the gain, and a mixer circuit for converting the output of the gain control circuit into an intermediate frequency signal In a receiver for demodulating a desired signal according to the tuning data from an RF signal and outputting it as a baseband signal, a local oscillation signal supplied to the mixer circuit for tuning the desired signal according to the tuning data. The frequency of is selected to a higher frequency side than the received RF signal as the desired signal to be an upper heterodyne detection method, or to a lower frequency side to be a lower heterodyne detection method according to the tuning data. When the detection scheme determining unit and the fundamental frequency of the frequency of the local oscillation signal is determined whether the detection method and the lower heterodyne system or with the upper heterodyne system is supplied to the mixer circuit for determining a
A divide-by-two output circuit that creates and outputs a signal of the frequency divided by two, and selects the signal of the fundamental frequency as the local oscillation signal to be supplied to the mixer circuit, or Depending on the tuning data, the local oscillation signal selection circuit that decides whether to select a signal, the baseband signal after demodulation is selected depending on the detection method determined by the detection method determination means. And a polarity reversal selection circuit which outputs the polarity without or inverting the polarity. 3. An amplifier circuit for receiving and amplifying a received RF signal, outputting the same, an RF gain control circuit for taking in the received RF signal amplified by the amplifier circuit and controlling its gain, and outputting the same. In order to select a desired signal in a receiving device that is equipped with an image cancellation mixer circuit for converting the output of the above into an intermediate frequency signal, selects and demodulates the desired signal from the received RF signal, and outputs it as a baseband signal. In addition, the frequency of the local oscillation signal supplied to the image cancel mixer circuit is set to the reception RF as the desired signal according to the frequency of the desired signal.
Detection method determining means for deciding whether to select the higher frequency side than the signal for the upper heterodyne detection method or the lower frequency side for the lower heterodyne detection method, and the baseband signal after channel selection demodulation And a polarity reversal selection circuit for inverting the polarity or outputting without inverting the polarity depending on the detection method determined by the detection method determining means. 4. An amplifying circuit for receiving and amplifying a received RF signal, outputting the same, an RF gain control circuit for taking in the received RF signal amplified by the amplifying circuit and controlling its gain, and outputting the same. In order to select a desired signal in a receiving device that is equipped with an image cancellation mixer circuit for converting the output of the above into an intermediate frequency signal, selects and demodulates the desired signal from the received RF signal, and outputs it as a baseband signal. In addition, the frequency of the local oscillation signal supplied to the image cancel mixer circuit is set to the reception RF as the desired signal according to the frequency of the desired signal.
A detection method determination unit that determines whether the upper heterodyne detection method is selected for the frequency side higher than the signal or the lower heterodyne detection method is selected for the lower frequency side, and whether the detection method is the upper heterodyne method or lower When the frequency of the local oscillation signal supplied to the image cancellation mixer circuit after determining whether to use the side heterodyne method is the fundamental frequency, a frequency-divided output that generates and outputs a signal having a frequency divided by 2 And a local oscillation signal to be supplied to the image cancellation mixer circuit, the local oscillation signal being determined according to the desired signal as to whether to select the signal of the fundamental frequency or the signal of the frequency divided by two. The oscillation signal selection circuit, and the baseband signal after channel demodulation, depending on the detection method determined by the detection method determining means, Inverting the sex, or the receiving device, wherein the polarity inversion selection circuit to not inverted output, by comprising a. 5. A first received RF having a first frequency band
A first amplifier circuit that receives and amplifies and outputs a signal, and a second amplifier that receives and amplifies and outputs a second received RF signal having a second frequency band different from the first frequency band. A circuit, a selection circuit for selecting one of the first and second amplification circuits, and a reception RF signal which is the output of the amplification circuit selected by the selection circuit, and controls and outputs the gain. An RF gain control circuit and an image cancellation mixer circuit for converting the output of the gain control circuit into an intermediate frequency signal, and a demodulation apparatus for selectively demodulating a desired signal from a received RF signal and outputting it as a baseband signal. In order to select a desired signal, the frequency of the local oscillation signal supplied to the image cancellation mixer circuit is set to the reception RF as the desired signal according to the frequency of the desired signal.
Detection method determining means for deciding whether to select the higher frequency side than the signal for the upper heterodyne detection method or the lower frequency side for the lower heterodyne detection method, and the baseband signal after channel selection demodulation And a polarity reversal selection circuit for inverting the polarity or outputting without inverting the polarity depending on the detection method determined by the detection method determining means.