JP2001308736A - High frequency device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency device which prevents backtalk from occurring. SOLUTION: Intermediate frequency 64a outputted from the mixer 53 is set so that it may become larger than a value obtained by subtracting the value of minimum frequency 16a from two times of maximum frequency 16b of a high frequency signal 16. Thus, the occurrence of the backtalk can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency device used for a video receiver or a data receiver.

[0002]

2. Description of the Related Art A conventional high-frequency device will be described below. As shown in FIG. 4, a conventional high-frequency device includes an input terminal 1 to which a high-frequency signal is supplied, a first high-frequency amplifier 2 connected to the input terminal 1, and a first high-frequency amplifier 2.
And a second high-frequency amplifier 3 connected to the output of
The output of the high-frequency amplifier 3 is connected to one input and the other input is connected to the output of the local oscillator 4, and the first intermediate frequency filter to which the output of the mixer 5 is connected. 6, a first intermediate frequency amplifier (hereinafter referred to as an intermediate frequency amplifier) 7 to which the output of the first intermediate frequency filter 6 is connected, and an output of the first intermediate frequency amplifier 7 connected to one input. A mixer 9 to which the output of the local oscillator 8 is connected to the other input, a second intermediate frequency filter 10 to which the output of the mixer 9 is connected,
An output terminal 11 to which the output of the second intermediate frequency filter 10 is connected, and a P terminal loop-connected to the local oscillator 4
It comprises an LL circuit 12, a PLL circuit 13 loop-connected to the local oscillator 8, and a crystal oscillator 14 for providing a reference frequency to the PLL circuit 12 and the PLL circuit 13.

The operation of the high-frequency device configured as described above will be described below. Input terminal 1 has approximately 5
A high-frequency signal (television broadcast signal) 16 of 7 MHz to 855 MHz is input. The input high-frequency signal 16 is mixed with the first local frequency 17 output from the local oscillator 4 by the mixer 5 and output as the intermediate frequency 15. As the intermediate frequency 15, a first intermediate frequency 15a of approximately 1200 MHz is guided through an intermediate frequency filter 6 of approximately 1200 MHz and a first intermediate frequency amplifier 7. The intermediate frequency 15a is mixed with the output of the local oscillator 8 by the mixer 9 to become a second intermediate frequency of approximately 44 MHz, which is output from the output terminal 11.

Here, the first signal output from the local oscillator 4
By varying the local frequency 17, the tuning of the high-frequency signal 16 input from the input terminal 1 is performed.
At this time, the relationship among the intermediate frequency 15a, the high-frequency signal 16, and the first local frequency 17 is as shown in (Equation 1).

[0005]

(Equation 1)

Accordingly, since the intermediate frequency 15a is constant, the high frequency signal shown in (Equation 2) can be selected (selected) by varying the first local frequency 17.

[0007]

(Equation 2)

Thus, the selected intermediate frequency 1
5a is mixed with the output from the local oscillator 8 by the mixer 9 and converted into a second intermediate frequency that is constant at approximately 44 MHz. This signal was output from the output terminal 11 via an intermediate frequency filter (bandpass filter) 10 of approximately 44 MHz.

[0009]

Conventionally, the intermediate frequency 15a has been set to about 1200 MHz. However, setting such values has the following problems. Hereinafter, this problem will be described with reference to FIG.

In FIG. 5, 16 is a high frequency signal,
For example, if the channel a is received, the intermediate frequency 1
5 has a relationship as shown in (Equation 3).

[0011]

(Equation 3)

That is, when the first local frequency 17 is considered as a center, the following equation (4) is obtained.

[0013]

(Equation 4)

Here, for example, when the desired high-frequency signal 16 is selected, the intermediate frequency 15a is 1200 MHz, the lowest frequency 16a of the high-frequency signal is 57 MHz,
Assuming that the highest frequency 16b is 855 MHz, the lowest frequency 17a of the first local frequency 17 is 1257 MHz as shown in (Equation 5).

[0015]

(Equation 5)

The highest frequency 17b of the first local frequency 17 is 2055 MHz as shown in (Equation 6).

[0017]

(Equation 6)

That is, in order to receive the entire range of the high-frequency signal 16, the first local frequency 17 must be 1257 MHz.
To 2055 MHz.

Up to this point, only normal reception has been considered, but the interfering waves 19 occurring simultaneously at this time will now be considered. For example, a minimum receiving frequency of 57 MHz 1
When receiving 6a, the first local frequency 17a becomes 1257 MHz as shown in (Equation 7).

[0020]

(Equation 7)

However, at this time, the input terminal 1 has 57 MH
A high frequency signal 16 of 57 Hz to 855 MHz as well as z is input. Assuming that an 855 MHz high frequency signal 16b is input in an extreme example, the first local frequency 1257MHz at this time is mixed by the mixer 5 to generate an intermediate frequency 15 of 402MHz as shown in (Equation 8). Become. This intermediate frequency 15 becomes an interference wave 19a.

[0022]

(Equation 8)

Similarly, the maximum reception frequency 1 of 855 MHz
When receiving 6b, the first local frequency 17b becomes 2055 MHz as shown in (Equation 9).

[0024]

(Equation 9)

However, at this time, the input terminal 1 has 855M
Hz, and a high-frequency signal 16 of 57 MHz to 855 MHz is input. Assuming that a 57 MHz high-frequency signal 16a is input in an extreme example, the first local frequency 2055 MHz at this time is mixed by the mixer 5 and
As shown in (Equation 10), the intermediate frequency 1 of 1998 MHz
5 will also occur. This intermediate frequency 15 becomes an interference wave 19b.

[0026]

(Equation 10)

That is, in FIG. 5, there is a possibility that an interfering wave 19 from the lowest interfering wave 19a of 402 MHz to the highest interfering wave 19b of 1998 MHz is generated (by the input high-frequency signal 16). This interfering wave 19 leaks to the outside via the input terminal 1 and becomes an interfering signal (hereinafter referred to as back talk) of another receiver. In particular, an interfering signal in a portion 20 where the interfering signal 19 and the high-frequency signal 16 overlap is a problem. In order to reduce the back talk generated by such a mechanism, it is necessary to provide the amplifiers 2 and 3 between the input terminal 1 and the mixer 5 in multiple stages to prevent leakage.

An object of the present invention is to solve such a problem and to provide a high-frequency device for preventing occurrence of back talk.

[0029]

In order to achieve this object, a high-frequency device according to the present invention provides an intermediate frequency output from a mixer by subtracting the value of the minimum frequency from twice the maximum frequency of the high-frequency signal. It is set to be larger.

Thus, occurrence of back talk can be prevented.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides an input terminal to which a high-frequency signal is input, a signal input to this input terminal being supplied to one terminal, and being applied to the other terminal. Is a mixer supplied with the output of the local oscillator,
An intermediate frequency filter to which an output of the mixer is supplied, and an output terminal to which an output of the intermediate frequency filter is supplied, wherein an intermediate frequency output from the mixer is twice the maximum frequency of the high frequency signal. A high-frequency device set to be larger than the value obtained by subtracting the value of the minimum frequency, and by setting the intermediate frequency to be larger than the value obtained by subtracting the value of the minimum frequency from twice the maximum frequency of the high-frequency signal, Even if an interfering wave occurs, the interfering wave is out of the range of the input high-frequency signal, so that it is possible to prevent the occurrence of backtalk affecting other receivers. Therefore, it is possible to reduce the number of amplifiers for preventing backtalk between the input terminal and the mixer, and to reduce the mounting area, the power consumption, and the component cost by increasing the number of amplifiers. There is.

According to the second aspect of the present invention, the intermediate frequency is 20
The high-frequency device according to claim 1, which is set between 20 MHz and 2022 MHz. By setting in this way, the level of spurious signals can be reduced and the number of spurious signals can be reduced. .

According to a third aspect of the present invention, a PLL circuit is loop-connected to the local oscillator, and the PLL circuit, the local oscillator, and the mixer are formed of a silicon germanium semiconductor. This is a high-frequency device. Since a silicon germanium semiconductor is superior in operation up to a higher frequency than a conventional bipolar semiconductor, a local oscillator having excellent phase noise characteristics can be realized. In addition, since the silicon germanium semiconductor has good linearity and excellent third-order distortion characteristics, a mixer having excellent distortion characteristics can be realized. There is also a significant power consumption reduction effect.

According to a fourth aspect of the present invention, the local oscillator is connected to a PLL circuit in a loop, and the PLL circuit, the local oscillator, and the mixer are formed of a CMOS semiconductor. Device.
Use of a CMOS semiconductor has a significant cost reduction effect.

According to a fifth aspect of the present invention, there is provided the high-frequency device according to the first aspect, wherein a surface acoustic wave filter is used as the intermediate frequency filter, and the mounting area is greatly reduced.

The invention according to claim 6 is the high-frequency device according to claim 1, wherein at least the mixer, the local oscillator, and the intermediate frequency filter are formed by a balanced circuit. Hardly affected by external noise. In addition, since it does not emit noise by itself, it does not give noise to other devices. Further, since the local oscillator does not affect the noise, the local oscillator has good phase noise characteristics. Therefore, a high-frequency device that receives digital signals can realize a high-performance high-frequency device, such as having fewer errors.

According to a seventh aspect of the present invention, there is provided an input terminal to which a high-frequency signal is input, and a signal input to the input terminal is input to one terminal and the other terminal is provided with a first local oscillator. A first mixer to which an output is supplied, and a series connection of a first intermediate frequency filter and an intermediate frequency amplifier connected between the output of the first mixer and one input of the second mixer; A second local oscillator connected to the other input of the second mixer, a second intermediate frequency filter connected to the output of the second mixer, and a second intermediate frequency filter. An output terminal connected to the output of the filter, wherein the intermediate frequency output from the first mixer is set to be higher than twice the maximum frequency of the high frequency signal minus the value of the minimum frequency. And output from the second mixer. The intermediate frequency 2 is a high-frequency device that is substantially equal to the lowest frequency of the high-frequency signal, and the intermediate frequency is set to be higher than twice the maximum frequency of the high-frequency signal minus the value of the minimum frequency. Thus, even if an interfering wave is generated, the interfering wave is out of the range of the input high-frequency signal, so that it is possible to prevent the occurrence of backtalk affecting other receivers. Therefore, an amplifier only for preventing back talk between the input terminal and the mixer as in the related art becomes unnecessary, and
This has the effect of reducing the mounting area, power consumption, and component cost of the amplifier.

Further, since the second intermediate frequency output from the second mixer is substantially equal to the lowest frequency of the high frequency signal, the second intermediate frequency is synthesized by the outputs of the first local oscillator and the second local oscillator. The value of the generated spurious can be reduced.

Furthermore, since the converter is an up-down converter, the bandwidth that can be received without switching can be expanded, and image disturbance can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of the high-frequency device. In FIG. 1, the high-frequency device according to the present embodiment includes:
An input terminal 51 to which a high-frequency signal is input, a high-frequency amplifier (hereinafter referred to as an RF amplifier) 52 connected to the input terminal 51, and an output of the RF amplifier 52 connected to one terminal and connected to the other terminal Is a first mixer 53 to which the output of the local oscillator 54 is connected; a first intermediate frequency filter 55 to which the output of the first mixer 53 is supplied as an intermediate frequency signal 64; An intermediate frequency amplifier (hereinafter referred to as an intermediate frequency amplifier) 56 to which an output of the frequency filter 55 is supplied, and an output of the intermediate frequency amplifier 56 is connected to one terminal and a second local oscillation circuit is connected to the other terminal. A second mixer 57 to which the output of the second mixer 57 is connected, and a second mixer 57 to which the output of the second mixer 57 is connected.
And the output of the second intermediate frequency filter 59 is connected and the second
And an output terminal 60 for outputting the intermediate frequency. A PLL circuit 61 is loop-connected to the first local oscillator 54, and a P
The LL circuit 62 is connected in a loop. And this P
A crystal oscillator 63 is commonly connected to the LL circuit 61 and the PLL circuit 62 to generate a reference frequency. The reason why the quartz oscillator 63 is shared is to reduce the size and cost.

Here, by using a surface acoustic wave filter (SAW filter) as the first intermediate frequency filter 55, the mounting area is reduced and the performance is improved. The PLL circuit 61 and the local oscillator 5
4 and the mixer 53 are made of a silicon germanium semiconductor to greatly reduce power consumption and improve performance. In addition, since the silicon germanium semiconductor is superior in operation up to a higher frequency than the conventional bipolar semiconductor, the local oscillator 54 having excellent phase noise characteristics is provided.
Can be realized. Furthermore, since the silicon germanium semiconductor has good linearity and excellent third-order distortion characteristics, a mixer 53 having excellent distortion characteristics can be realized. If the PLL circuit 61, the local oscillator 54, and the mixer 53 are composed of CMOS semiconductors, there is a significant cost reduction effect.

Further, an RF amplifier 52, a mixer 53, a local oscillator 54, an intermediate frequency filter 55, an intermediate frequency amplifier 5
6, mixer 57, local oscillator 58, intermediate frequency filter 5
Reference numeral 9 denotes a balanced circuit. Therefore, it is hardly affected by external noise. In addition, since it does not emit noise by itself, it does not give noise to other devices. Furthermore, since the local oscillators 54 and 58 do not affect the noise, the local oscillators 54 and 58 have good phase noise characteristics. Therefore,
With a high-frequency device that receives a digital signal, a high-performance high-frequency device can be realized, for example, with fewer errors.

The operation of the high-frequency device configured as described above will be described below. The input terminal 51 receives a high-frequency signal 16 (television broadcast signal) of approximately 57 MHz to 855 MHz. The input high-frequency signal 16 is mixed with the first local frequency 67 output from the local oscillator 54 by the mixer 53 and output as the intermediate frequency 64. This intermediate frequency 64 is approximately 2021M
Hz through an intermediate frequency filter (band pass filter) 55 and a first intermediate frequency amplifier
A first intermediate frequency 64a of 1 MHz is derived.

Here, as shown in FIG.
If the overlapping portion 20 of the radio frequency signal 5 and the high frequency signal 16 can be eliminated, the back talk will be eliminated. That is,
As shown in (Equation 11), the lowest frequency 19a of the interference wave 19 is obtained.
Should be higher than the highest frequency 16b of the high-frequency signal 16.

[0045]

[Equation 11]

When the highest frequency 16b of (Equation 11) is transposed, (Equation 12) is obtained.

[0047]

(Equation 12)

Here, the first local frequency 17a when receiving the lowest frequency 16a is as shown in (Equation 13).

[0049]

(Equation 13)

Therefore, from (Equation 12) and (Equation 13),
(Equation 14) is derived.

[0051]

[Equation 14]

That is, as shown in FIG.
By setting a to be greater than twice the maximum frequency 16b of the high frequency signal 16 minus the value of the minimum frequency 16a, the conventional overlapping portion 20 is eliminated, and even if the interference wave 65 is generated, Since it is outside the range of the input high-frequency signal 16, back talk affecting other receivers can be prevented from occurring. Therefore, it is not necessary to provide an amplifier between the input terminal 51 and the mixer 53 only for the purpose of preventing back talk, and there are effects such as a reduction in mounting area, a reduction in power consumption, and a reduction in component costs.

For example, in North American cable broadcasting, (Equation 1)
As shown in 5), the intermediate frequency 64a may be set to 1653 MHz or more.

[0054]

(Equation 15)

In this embodiment, the intermediate frequency 64a
Is set to 2021 MHz. Therefore, as shown in FIG.
There is no overlap with. Therefore, there is no influence of the back talk on other receivers.

Next, spurious components in the present embodiment will be described with reference to FIG. In an up-down converter having a local oscillator 54, another local oscillator 58, and two local oscillators as in the high-frequency device according to the present embodiment, spurious exists due to mutual interference between the local oscillator 54 and the local oscillator 58. It is conceivable that spurious is output from the output terminal 60.

FIG. 3 shows a spurious generation mechanism. The high frequency signal 16 is mixed with a local oscillator 54 in a mixer 53 to generate an intermediate frequency 64. The intermediate frequency 64 is mixed by the second local oscillator 58 and the second mixer 57 to generate the second intermediate frequency 30. However, in each of the mixers 53 and 57, as shown in (Equation 16), a spurious 37 is generated by the generation mechanism of the first local frequency 67 * n ± the second local frequency 68 * m, and the second intermediate frequency 30 It becomes an interference signal.

[0058]

(Equation 16)

M and n are integers and represent the m-th and n-th harmonics, respectively, and the higher the order, the lower the level of the harmonic. (Table 1) shows an example of a generation mechanism of the second intermediate frequency 30 output to the output terminal 60.

[0060]

[Table 1]

In Table 1, when a certain frequency is selected as the intermediate frequency 40, the first local frequency 67 * n-the second local frequency 6 when the channel 41 is selected.
At 8 * m, spurious elements 37 occur in the number of combinations 45. It can be said that the larger the numerical values of n and m and the smaller the number of the combinations 45, the lower the signal level of the spurious 37 and the smaller the number of spurious, so that it is excellent. In the present embodiment, the intermediate frequency 40 is set to 2021 MHz, but by setting the intermediate frequency between 2020 MHz and 2022 MHz, the spurious can be minimized as apparent from (Table 1).

As described above, according to the present embodiment, unnecessary signals are not generated in the input high-frequency signal region, and there is an effect of preventing backtalk and an effect of reducing spurious.

[0063]

As described above, according to the present invention, by setting the intermediate frequency to be larger than the value obtained by subtracting the value of the minimum frequency from twice the maximum frequency of the high-frequency signal,
Even if an interfering wave occurs, it is out of the range of the input high-frequency signal, so that it is possible to prevent the occurrence of backtalk affecting other receivers.

Therefore, according to the present invention, since back talk can be completely prevented, there is no need for a means for preventing leakage to the outside. Therefore, the input terminal and the mixer used for preventing leakage to the outside are not required. The number of amplifiers between them can be reduced, resulting in effects such as a reduction in mounting area, power consumption, and component cost.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a high-frequency device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a frequency spectrum in the high-frequency device.

FIG. 3 is a diagram showing a frequency spectrum for explaining spurious in the high-frequency device.

FIG. 4 is a circuit block diagram of a conventional high-frequency device.

FIG. 5 is a diagram showing a frequency spectrum of the high-frequency device.

[Explanation of symbols]

 51 input terminal 53 mixer 54 local oscillator 55 intermediate frequency filter 60 output terminal 64 intermediate frequency signal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K020 AA00 AA02 AA08 DD02 DD11 DD13 EE01 EE04 FF04 GG01 HH13 MM00 MM04 MM05 5K052 AA02 BB03 BB15 DD05 FF26 GG24 GG26

Claims (7)

[Claims] An input terminal to which a high-frequency signal is input; a mixer to which a signal input to the input terminal is supplied to one terminal and an output of a local oscillator is supplied to the other terminal; An intermediate frequency filter to which the output of the mixer is supplied, and an output terminal to which the output of the intermediate frequency filter is supplied, the intermediate frequency output from the mixer being twice to the minimum of the maximum frequency of the high frequency signal. A high-frequency device set to be higher than the value obtained by subtracting the frequency value. 2. The intermediate frequency is from 2020 MHz to 202
The high-frequency device according to claim 1, wherein the high-frequency device is set between 2 MHz. 3. A PLL circuit is loop-connected to the local oscillator, and the PLL circuit, the local oscillator,
The high-frequency device according to claim 1, wherein the mixer is made of a silicon germanium semiconductor. 4. A PLL circuit is loop-connected to the local oscillator, and the PLL circuit, the local oscillator,
The high-frequency device according to claim 1, wherein the mixer is formed of a CMOS semiconductor. 5. The high-frequency device according to claim 1, wherein a surface acoustic wave filter is used as the intermediate frequency filter. 6. At least a mixer, a local oscillator,
2. An intermediate frequency filter according to claim 1, wherein said intermediate frequency filter is formed by a balanced circuit.
2. The high-frequency device according to claim 1. 7. An input terminal to which a high-frequency signal is input, and a first terminal to which a signal input to the input terminal is input to one terminal and an output of the first local oscillator is supplied to the other terminal. And the output of the first mixer and the second
A series connection of a first intermediate frequency filter and an intermediate frequency amplifier connected between one input of the mixer of
A second local oscillator connected to the other input of the mixer, a second intermediate frequency filter connected to the output of the second mixer, and an output of the second intermediate frequency filter. And an intermediate terminal output from the first mixer is set to be larger than a value obtained by subtracting a value of a minimum frequency from twice a maximum frequency of the high frequency signal, and The second output from the mixer of
A high frequency device whose intermediate frequency is substantially equal to the lowest frequency of the high frequency signal.