JP2002135139A - Frequency conversion circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency conversion circuit, which can make a microcomputer integrated circuit(IC) common to frequency conversion circuits of a plurality of types provided for different input signal frequency bands. SOLUTION: The frequency conversion circuit is constituted by; local oscillators 25a, 25b for outputting local oscillation signals; mixers 24a, 24b for converting each signal distributed by a distributor for distributing a first frequency-band input signal into a second frequency-band signal; PLL-IC 32a, 32b for controlling oscillation frequency of local oscillation signals being output from the local oscillators 25a, 25b; and a microcomputer IC for controlling the PLL-IC 32a, 32b, using a voltage value being input to input ports, so as to output from local oscillators 25a, 25b the local oscillation signals corresponding to the first frequency-band input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for peripheral equipment for receiving satellite broadcasts and the like.
The present invention relates to a frequency conversion circuit suitable for an upconverter that performs frequency conversion from a band frequency to a BS band frequency.

[0002]

2. Description of the Related Art As one of frequency conversion circuits, there is an upconverter for performing frequency conversion from a CATV band frequency to a BS band frequency, and a typical prior art block diagram thereof is shown in FIG.

[0003] The conventional upconverter shown in FIG.
A signal of a CATV band frequency (10 MHz to 770 MHz) input from the CATV input terminal 1 is distributed by a distributor 3 composed of a wound balun transformer, and one of the signals is frequency-divided into a BS band (900 MHz to 2.5 GHz). The signal is converted and output from the BS-IF output terminal 10, and the other signal distributed by the distributor 3 is output from the CATV output terminal 2.

[0004] The upconverter includes an RF amplifier 4 for amplifying one of the signals distributed by the distributor 3.
And a frequency conversion unit 1 for frequency-converting each signal obtained by distributing the signal amplified by the RF amplification unit 4 into a BS band.
3 and two IF amplifiers 9a and 9b for separately amplifying the respective signals frequency-converted by the frequency converter 13.
And is configured to combine both signals amplified by the IF amplifiers 9a and 9b and output the combined signal from the BS-IF output terminal 10 to the outside.

The frequency converter 13 has two local oscillator circuits 6a and 6b for outputting local signals,
Two mixer units 5a and 5b for converting the frequency to the BS band based on the local signals output from the two local oscillation circuit units 6a and 6b, and two local oscillation circuit units 6a and 6b.
And two PLL-ICs 7a and 7b for controlling the oscillation frequency of the local signal output from the PLL-IC 7b.
a and 7b for controlling the microcomputer IC8.

Further, this upconverter has a CA
For the purpose of preventing local signal leakage to the TV input terminal 1 and the CATV output terminal 2, a filter 11 for attenuating a local signal is provided between the RF amplifying unit 4 and the distribution unit at the subsequent stage, and a BS-IF output is provided. In order to prevent local signal leakage to the terminal 10, the IF amplifying sections 9a and 9b
A filter 12 for attenuating a local signal is provided between the subsequent coupling section and the BS-IF output terminal 10.

[0007]

However, the above-mentioned prior art has the following problems.

In other words, in the above-mentioned conventional technology, the microcomputer IC8 controls only to transmit data to the PLL-ICs 7a and 7b when the power is turned on, and a plurality of models having different input signal CATV band frequency bands. Therefore, it is necessary to change the microcomputer IC according to each of the above, which has caused an increase in cost.

In other words, the frequency band of the CATV signal differs depending on the CATV broadcasting service company, and the frequency of the local oscillation signal of the frequency converter must be changed according to the frequency band of the input signal. The microcomputer IC has been changed. Then, not only does the work of changing the microcomputer IC at the time of manufacturing increase, but also inventory management of a plurality of types of microcomputer ICs becomes necessary, which causes a cost increase at present.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a frequency conversion circuit that can use a common microcomputer IC in a plurality of models having different frequency bands of input signals. Aim.

[0011]

In order to solve the above-mentioned problems, a frequency conversion circuit according to the present invention converts each signal obtained by dividing an input signal in a first frequency band by a distributor into a second frequency band. A frequency converter configured to combine and output both signals frequency-converted by the frequency converter, wherein the frequency converter includes two local oscillators that output a local oscillation signal. An oscillation circuit unit; two mixer units for converting respective signals distributed by the distribution unit to a second frequency band based on local oscillation signals output from the two local oscillation circuit units; Two Ps that control the oscillation frequency of the local oscillation signal output from the two local oscillation circuits
The two PLL-ICs are controlled by a voltage value input to an input port so that the LL-IC and a local oscillation signal corresponding to a first frequency band of the input signal are output from the two local oscillation circuits. And a microcomputer IC for controlling.

According to the present invention, a voltage value applied to a specific input port of the microcomputer IC itself is used as a switch to be a local oscillation signal corresponding to the first frequency band of the input signal to be frequency-converted by the frequency converter. Like, PLL
-Since it is configured to change the control signal to the IC, it can be handled by changing the applied voltage of the input port of the microcomputer IC, and even for a plurality of models having different first frequency bands of the input signal, It is possible to share the same microcomputer IC.

Further, in the frequency conversion circuit according to the present invention, the microcomputer IC is arranged between the two local oscillation circuit units.

According to the present invention, since the configuration is such that it is arranged between the two local oscillation circuit units via the microcomputer IC, by increasing the distance between the local oscillation circuits,
Mutual interference between respective local signals due to unnecessary radiation or the like can be prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, an up-converter will be described as a frequency conversion circuit. However, the present invention is not limited to this, and can be applied to a down-converter or a circuit portion that converts a frequency band in a tuner or the like. is there.

FIG. 1 is a block diagram showing an upconverter according to an embodiment of the present invention.

In FIG. 1, reference numeral 20 denotes a CATV input terminal to which an input signal of a CATV band (10 MHz to 770 MHz) as a first frequency band is input, and 33 denotes a CATV band input signal input from the CATV input terminal 20. A distributor 23 for distributing is an RF amplifier, which is a first amplifier for amplifying one signal distributed by the distributor 33, and 22 is an RF amplifier.
Each signal to which the signal amplified by the amplifier 23 is distributed is divided into a BS band (900 MHz to 900 MHz) which is a second frequency band.
And a mixer section 24a for converting the frequency to 2.5 GHz).
2 amplify each signal frequency-converted by 2
An IF amplifier, which is two second amplifiers, is a BS-IF output terminal for outputting a signal obtained by combining both signals amplified by the IF amplifiers 26a and 26b to the outside, and 21 is distributed by a distributor 33. This is a CATV output terminal for outputting the other signal to the outside.

The frequency conversion unit 22 outputs two local oscillation circuits 25a and 25b for outputting local oscillation signals having different oscillation frequencies, and an RF signal based on the local oscillation signals output from the local oscillation circuits 25a and 25b. Two mixers 24a and 24b for frequency-converting the respective signals, to which the signals amplified by the amplifier 23 are distributed, into a BS band, which is a second frequency band, and local oscillators output from local oscillation circuit units 25a and 25b. Two PLL-ICs 32 for controlling the oscillation frequency of the oscillation signal
a, 32b and a local oscillation signal corresponding to the frequency band of the CATV signal as an input signal.
a and a microcomputer IC 34 for controlling the PLL-ICs 32a and 32b according to the voltage value input to the input port so as to output from the input ports 25a and 25b.

In the present embodiment, the microcomputer IC 34 is connected to the two local oscillation circuit units 2 in the printed wiring board on which the electronic components constituting the circuit described above are mounted.
The microcomputer IC 34 and the local oscillation circuit units 25a and 25b are mounted as arrangements located between 5a and 25b.

In the up-converter of the present embodiment, the input signal in the CATV band is distributed from the CATV input terminal 20 to the CATV output terminal 21 and the frequency converter 22 by the distributor 33, and the signal is distributed to the frequency converter 22. The distributed signal is amplified by the RF amplifier 23.

The signals amplified by the RF amplifier 23 and distributed by the distributors are input to mixers 24a and 24b, respectively, and are supplied to local oscillator circuits 25a and 25a.
25b, the frequency is converted to the BS band. That is, RF
Each signal obtained by distributing the signal amplified by the amplifier 23 by the distribution unit is mixed with the local oscillation signals from the local oscillation circuit units 25a and 25b by the mixer units 24a and 24b, and frequency-converted to the BS band. This is RF
The signals amplified by the amplifier 23 are distributed by the distributor, and the signals having the difference frequencies between the respective signals output from the local oscillator circuits 25a and 25b are output from the mixers 24a and 24b, respectively. As a result, frequency conversion to the BS band is performed.

Each of the frequency-converted signals is IF
The signals are amplified by the amplifiers 26a and 26b, and both of the amplified signals are combined by the combining unit and output from the BS-IF output terminal 28. By inputting the output signal to an STB (set top box) or the like, the output signal is demodulated inside the STB and can be monitored as a video.

In this embodiment, the local oscillation signals output from the local oscillation circuit sections 25a and 25b are:
The channel is selected by being controlled by the PLL-ICs 32a and 32b.

The PLL-ICs 32a and 32b
Is controlled by a bus signal transmitted from the microcomputer IC34.

Here, in the microcomputer IC 34 of the present embodiment, the PLL-IC is switched so as to be switched by a voltage value applied to a specific input port of the microcomputer IC 34 itself.
It is possible to change the bus signal transmitted for controlling 32a and 32b. Therefore, according to the present embodiment, it is possible to select a plurality of local oscillation frequencies, and it is possible to use the same microcomputer IC for a plurality of models having different frequency bands of CATV signals as input signals. It becomes possible.

According to the present embodiment, the microcomputer IC
By arranging 34 between the local oscillation circuit units 25a and 25b, the distance between the local oscillation circuits can be increased, so that mutual interference between the local oscillation circuits due to unnecessary radiation or the like can be suppressed. At this time, the distance between the local oscillation circuit portions 25a and 25b is not simply increased, but the microcomputer IC is arranged between them. Therefore, the area of the printed wiring board is not expanded, and thus the printed wiring board is not increased. The size of the apparatus to which the present invention is applied can be reduced by effectively utilizing the mounting area of the present invention.

In this embodiment, the IF amplifiers 26a and 26b as the second amplifiers are connected to the mixers 24a and 24a.
4b and a connection unit that combines both signals amplified by the IF amplification units 26a and 26b, but a single second connection is provided between the connection unit and the BS-IF output terminal 28. May be connected to each other, and the signal combined by the combining unit may be amplified by the single IF amplifying unit.

[0028]

As described above, according to the present invention, as a microcomputer IC, a voltage applied to a specific input port of the microcomputer itself is used as a switch, and an input signal such as a CATV signal which is frequency-converted. In order to obtain a local oscillation signal corresponding to a signal of a first frequency band such as
By changing the control signal to the IC, it is possible to cope with the signal in the first frequency band of the input signal to be frequency-converted by changing the voltage applied to the input port of the microcomputer IC. Therefore, it is possible to use a single microcomputer IC for the frequency of the first frequency band of the input signal such as the CATV signal to be frequency-converted, that is, for a plurality of models having different frequency bands of the input signal. Thus, it is possible to reduce costs in terms of material costs and the like.

According to the present invention, two PLL-Is
Since the microcomputer IC for controlling C is mounted between two local oscillation circuit units forming two frequency conversion units, the distance between the local oscillation circuits is increased so that each local signal due to unnecessary radiation or the like is increased. Can be prevented from interfering with each other. Furthermore, the wiring for controlling the PLL-IC from the microcomputer IC can be shortened,
The effect of bass noise can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic structure of an upconverter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic structure of an upconverter according to a conventional embodiment.

[Explanation of symbols]

 Reference Signs List 20 CATV input terminal 21 CATV output terminal 22 Frequency conversion unit 23 RF amplification unit (first amplification unit) 24a, 24b Mixer unit 25a, 25b Local oscillation circuit unit 26a, 26b IF amplification unit (second amplification unit) 28 BS -IF output terminals 32a, 32b PLL-IC 34 microcomputer IC

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 7/16 H04N 7/16 A F term (Reference) 5C056 FA01 FA11 HA01 HA13 HA14 5C064 BA01 BB05 BC12 BC14 BC21 BD08 5K020 AA03 AA05 DD12 EE16 FF05 GG02 NN10 5K060 DD05 EE05 HH15 HH16 HH25 HH32 JJ17

Claims (2)

[Claims] An input signal of a first frequency band is provided with a frequency conversion unit for converting each signal distributed by the distribution unit to a second frequency band, and both signals frequency-converted by the frequency conversion unit are provided. A frequency conversion circuit configured to output the local oscillation signal; and a local oscillation signal output from the two local oscillation circuit portions. Two mixers for converting respective signals distributed by the distribution unit into a second frequency band based on the following formulas: and 2 for controlling an oscillation frequency of a local oscillation signal output from the two local oscillation circuit units. PLL-IC
And a microcomputer that controls the two PLL-ICs by a voltage value input to an input port so that a local oscillation signal corresponding to a first frequency band of the input signal is output from the two local oscillation circuits. A frequency conversion circuit comprising an IC. 2. The frequency conversion circuit according to claim 1, wherein said microcomputer IC is arranged between said two local oscillation circuit units.