JPH0974362A - High frequency selection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the adjustment of a band-pass filter between first and second frequency converters by providing a filter composed of the band-pass filter and a trap circuit between the first and second frequency converters. SOLUTION: Between the first and second frequency converters 4 and 10, the filter composed of the band-pass filter 6 of a wide band constituted of a microstrip line for limiting first intermediate frequency signals and the trap circuit 7 constituted of the microstrip line for attenuating the fundamental frequency or high-order frequency of a first local oscillator 5 and the fundamental frequency or high-order frequency of a second local oscillator 11 is provided. Then, for the filter between the first frequency converter 4 and the second frequency converter 10, the microstrip lines constituted of a pattern on a base are used. Also, the arranging order of the band-pass filter 6, the trap circuit and a first intermediate frequency amplifier 8 is not specified as long as they are provided between the first frequency converter 4 and the second frequency converter 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a TV tuner and a CAT.
The present invention relates to a high frequency selection circuit for a double super heterodyne tuner such as a V tuner.

[0002]

2. Description of the Related Art In recent years, the transmission frequency band of television signals in CATV tends to become higher and higher in recent years.
In order to receive a television signal by CATV, a double superheterodyne tuner having a good distortion characteristic is used.

FIG. 14 shows a high frequency selection circuit of a conventional double super heterodyne tuner. 2 is the input filter,
3 is an RF amplifier, 4 is a first frequency converter, 5 is a first local oscillator, 86 is a bandpass filter, 8 is a first intermediate frequency amplifier, 87 is a bandpass filter, and 10 is a second frequency converter. , 11 is a second local oscillator, 12 is a second intermediate frequency filter, and 13 is a second intermediate frequency amplifier. The signal input from the input 1 is band-limited by the input filter 2, amplified by the RF amplifier 3, and fed to the first frequency converter 4
Is converted into a first intermediate frequency signal.

The first intermediate frequency signal is band-limited by the band-pass filter 86, amplified by the first intermediate-frequency amplifier 8, further band-limited by the band-pass filter 87, and secondly band-passed by the second frequency converter 10. Converted to an intermediate frequency signal. The second intermediate frequency signal is band-limited by the second intermediate frequency filter 12, amplified by the second intermediate frequency amplifier 13, and becomes an intermediate frequency output.

FIG. 15 shows a conventional bandpass filter 86,
The circuit diagram of the 1st intermediate frequency amplifier 8 and the band pass filter 87 is shown. 114 is a feedthrough capacitor, 87 and 102 are coils, 88, 89, 109, 110 and 111 are metal plates,
90, 91, 92, 93, 97, 98, 101, 10
4, 106, 107, 108 are capacitors, 94, 9
6, 99, 100 and 103 are resistors, 95 is a transistor and 105 is a 9v power supply.

The bandpass filter 86 is a bandpass filter formed by arranging two metal plates in parallel, and the bandpass filter 87 is a bandpass filter formed by arranging three metal plates 88 and 89 in parallel. The filter 87 adjusts the metal plates 109, 110 and 111 to limit the band of the first intermediate frequency signal.
6 and the frequency characteristics of the bandpass filter 87 are shown in FIG.
A narrow band filter is used as shown in (a) and (b). Here, the horizontal axis of FIGS. 16A and 16B represents the frequency (1M
Hz to 3 GHz), and the vertical axis represents the gain (-90 to 10 dB).

In this way, the bandpass filters 86, 87
Attenuates the fundamental and higher frequencies of the first local oscillator with

[0008]

[Equation 1]

[0009] As represented by, the sum and difference signals of the fundamental frequency signals of the first and second local oscillators and their higher order frequency signals appear in the band of the second intermediate frequency signal (hereinafter referred to as interference). Spurious interference) is suppressed.

Where fLO1 is the fundamental frequency of the first local oscillator, fLO2 is the fundamental frequency of the second local oscillator,
fUD is the frequency of spurious interference, N is the harmonic order of the first local oscillator, and M is the harmonic order of the second local oscillator.

[0011]

However, in the conventional high frequency selection circuit, the band pass filters 86 and 87 between the first frequency converter 4 and the second frequency converter 10 are provided.
Is made up of two metal plates 88, 89 and 3 for narrowing the band.
Since the first intermediate frequency signal is band-limited by the band-pass filters 86 and 87 formed by arranging the metal plates 109, 110, and 111 in parallel, the first frequency converter 4 and the second frequency converter are provided. Bandpass filter 8 between 10
Adjustment of 6, 87 is required.

In view of the above drawbacks, it is an object of the present invention to make the bandpass filter between the first frequency converter and the second frequency converter unadjusted.

[0013]

The high frequency selection circuit in the first invention is constituted by a microstrip line for limiting the first intermediate frequency signal between the first frequency converter and the second frequency converter. A wideband bandpass filter,
A filter including a trap circuit constituted by a microstrip line that attenuates the fundamental frequency or higher order frequency of the first local oscillator and the fundamental frequency or higher order frequency of the second local oscillator is provided.

In the high frequency selection circuit according to the second aspect of the invention, between the first frequency converter and the second frequency converter,
A wideband bandpass filter composed of a microstrip line that limits the first intermediate frequency signal, and attenuates the fundamental frequency or higher order frequency of the first local oscillator and the fundamental frequency or higher order frequency of the second local oscillator. A trap circuit constituted by a microstrip line and a low pass filter constituted by a microstrip line for attenuating the high-order frequency of the first local oscillator and the high-order frequency of the second local oscillator.

In the high frequency selection circuit according to the third aspect of the invention, between the first frequency converter and the second frequency converter,
A wideband bandpass filter configured by a microstrip line that limits the first intermediate frequency signal, a highpass filter configured by a microstripline that attenuates the fundamental frequency of the second local oscillator, and a fundamental frequency of the first local oscillator Alternatively, a filter including a trap circuit configured by a microstrip line that attenuates high-order frequencies and high-order frequencies of the second local oscillator is provided.

In the high frequency selection circuit according to the fourth aspect of the invention, between the first frequency converter and the second frequency converter,
A wideband bandpass filter configured by a microstrip line that limits the first intermediate frequency signal, a highpass filter configured by a microstripline that attenuates the fundamental frequency of the second local oscillator, and a fundamental frequency of the first local oscillator Alternatively, a trap circuit configured by a microstrip line for attenuating a high-order frequency and a high-order frequency of the second local oscillator, and a high-order frequency of the first local oscillator and a high-order frequency of the second local oscillator are attenuated. A filter composed of a low-pass filter configured by a microstrip line is provided.

[0017]

According to the high frequency selection circuit of one embodiment of the present invention, a wide band composed of a microstrip line for limiting the first intermediate frequency signal is provided between the first frequency converter and the second frequency converter. A band pass filter and a filter including a trap circuit configured by a microstrip line for attenuating the fundamental frequency or higher order frequency of the first local oscillator and the fundamental frequency or higher order frequency of the second local oscillator are provided. Instead of using a conventional metal plate as a filter between the frequency converter of the present invention and the second frequency converter, the first frequency converter uses a microstrip line formed by a pattern on the substrate. The filter between and the second frequency converter can be unregulated.

Further, high-order frequencies of the first local oscillator and the second local oscillator falling within the bands of the first intermediate frequency signal and the second intermediate frequency signal are suppressed, and the fundamental frequency or high frequency of the first local oscillator is suppressed. The next frequency and the fundamental frequency or higher order frequency of the second local oscillation signal are converted by the first frequency conversion circuit and the second frequency conversion circuit, and are converted into bands of the first intermediate frequency signal and the second intermediate frequency signal. Suppresses incoming spurious interference.

Further, between the first frequency converter and the second frequency converter, a wideband bandpass filter constituted by a microstrip line for limiting the first intermediate frequency signal, and the basic of the first local oscillator. A trap circuit configured by a microstrip line for attenuating the frequency or higher order frequency and the fundamental frequency or higher order frequency of the second local oscillator, and the higher order frequency of the first local oscillator and the second local oscillator. On the substrate, instead of using a conventional metal plate for the filter between the first frequency converter and the second frequency converter, a filter formed of a low-pass filter configured by a microstrip line that attenuates high-order frequencies is provided. Since the microstrip line composed of the pattern is used, the filter between the first frequency converter and the second frequency converter is atoned. It can be of.

Furthermore, the higher frequencies of the first local oscillator and the second local oscillator that fall within the band of the first intermediate frequency signal and the second intermediate frequency signal are suppressed, and the fundamental frequency or high frequency of the first local oscillator is suppressed. The next frequency and the fundamental frequency or higher order frequency of the second local oscillation signal are converted by the first frequency conversion circuit and the second frequency conversion circuit, and are converted into bands of the first intermediate frequency signal and the second intermediate frequency signal. Suppresses incoming spurious interference.

When the second intermediate frequency is set lower than the first intermediate frequency and the fundamental frequency of the second local oscillator is set lower than the first intermediate frequency, the first frequency converter and the second frequency converter are connected. A wideband bandpass filter formed of a microstrip line that limits the first intermediate frequency signal, and a highpass filter formed of a microstrip line that attenuates the fundamental frequency of the second local oscillator,
A filter including a trap circuit configured by a microstrip line that attenuates the fundamental frequency or higher order frequency of the first local oscillator and the higher order frequency of the second local oscillator is provided, and the first frequency converter and the second frequency converter are provided. Instead of using a conventional metal plate for the filter between the frequency converters of the above, since the microstrip line configured by the pattern is used on the substrate, the filter between the first frequency converter and the second frequency converter is The filter of can be adjusted.

Further, high-order frequencies of the first local oscillator and the second local oscillator that fall within the bands of the first intermediate frequency signal and the second intermediate frequency signal are suppressed, and the fundamental frequency or high frequency of the first local oscillator is suppressed. The next frequency and the fundamental frequency or higher order frequency of the second local oscillation signal are converted by the first frequency conversion circuit and the second frequency conversion circuit, and are converted into bands of the first intermediate frequency signal and the second intermediate frequency signal. Suppresses incoming spurious interference.

When the second intermediate frequency is lower than the first intermediate frequency and the fundamental frequency of the second local oscillator is set lower than the first intermediate frequency, the first frequency converter and the second frequency converter are connected. A wideband bandpass filter formed of a microstrip line that limits the first intermediate frequency signal, and a highpass filter formed of a microstrip line that attenuates the fundamental frequency of the second local oscillator,
A trap circuit constituted by a microstrip line for attenuating the fundamental frequency or higher order frequency of the first local oscillator and the higher order frequency of the second local oscillator, the higher order frequency of the first local oscillator and the second higher frequency Instead of using a conventional metal plate for the filter between the first frequency converter and the second frequency converter, a filter composed of a low-pass filter configured by a microstrip line that attenuates higher-order frequencies of the local oscillator is provided. Since the microstrip line constituted by the pattern is used on the substrate, the filter between the first frequency converter and the second frequency converter can be made unadjusted.

Further, high-order frequencies of the first local oscillator and the second local oscillator that fall within the bands of the first intermediate frequency signal and the second intermediate frequency signal are suppressed, and the fundamental frequency or high frequency of the first local oscillator is suppressed. The next frequency and the fundamental frequency or higher order frequency of the second local oscillation signal are converted by the first frequency conversion circuit and the second frequency conversion circuit, and are converted into bands of the first intermediate frequency signal and the second intermediate frequency signal. Suppresses incoming spurious interference.

[0025]

【Example】

(Embodiment 1) A high frequency selection circuit according to a first embodiment of the present invention will be described below with reference to FIG. Figure 1 shows the first
3 is a configuration diagram of a high frequency selection circuit according to the embodiment of FIG.

Now, the case where the fundamental frequency of the second local oscillator is lower than the first intermediate frequency will be described as an example.

Reference numeral 2 is an input filter, 3 is an RF amplifier, 4 is a first frequency converter, 5 is a first local oscillator, and 6 is a first local oscillator.
A wideband bandpass filter for limiting the intermediate frequency signal, 7 is a trap circuit for attenuating the fundamental frequency or higher frequencies of the first local oscillator and the higher frequencies of the second local oscillator, and 8 is the first intermediate frequency Amplifier, 9 is a wideband bandpass filter for limiting the first intermediate frequency signal, 10 is a second frequency converter, 11 is a second local oscillator circuit, 12 is a second intermediate frequency filter, and 13 is a second intermediate frequency amplifier. Is.

If the bandpass filter 6, the trap circuit 7 and the first intermediate frequency amplifier 8 are located between the first frequency converter 4 and the second frequency converter 10, they are arranged in any order.

The trap circuit 7 may be a low pass filter having poles at the fundamental frequency or higher order frequency of the first local oscillator and the higher order frequency of the second local oscillator.

As an example, the circuit diagram of the bandpass filter 6 constituted by the microstrip line is shown in FIG. 2, and the circuit diagram of the trap circuit 7 constituted by the microstrip line is shown in FIG. Filter 6
FIG. 4 shows the frequency characteristic of the filter in which the trap circuit 7 is combined with FIG.

In FIG. 2, 15, 16, 17, 18,
Reference numeral 21 is a pattern formed on the substrate, and 19 and 20 are capacitors, which form a band-pass filter of three coupled lines.

In FIG. 3, reference numerals 25 to 38 denote patterns to be formed on the substrate, which are resonance circuits in which the coils and capacitors are grounded by the patterns 26 and 27. Similarly, the patterns 28 and 29, the patterns 31 and 32, and the patterns 33 and 34 are shown. The patterns 37 and 36 also show a resonance circuit in which the coil and the capacitor are grounded.

The horizontal axis of FIG. 4 is frequency and the minimum frequency is 1 MHz.
z, the maximum frequency is 3 GHz, the width of one memory is 300 MHz, and the vertical axis is the minimum gain of -90 and maximum gain of 10 dB.
Thus, one memory has 10 dB.

The frequency band of the input signal is set to 91.25-54.
9.25MHz, the first intermediate frequency is 612.75MH
z, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator is 554 MHz.
The spurious interference generated in the first intermediate frequency band by the frequency converter and generated in the second intermediate frequency band by the second frequency conversion circuit can be calculated by (Equation 1). At this time, set the channel where spurious

[0035]

[Table 1]

As shown in FIG. (Table 1) (a) is a channel of spurious interference generated in the first intermediate frequency (612.75 MHz) band, (Table 1) (b) is the second intermediate frequency (5
It is a channel of spurious interference that occurs in the (8.75 MHz) band. Table 1 shows in order from the left, channels in which spurious interference occurs, the order of the first local oscillator 5, the order of the second local oscillator 11, the frequency of spurious interference, the first order.
The fundamental or higher frequencies of the local oscillator 5 of the second
Is the fundamental frequency or higher order frequency of the local oscillator 11.

As shown in Table 1 (a), for example, 7
At the time of channel reception, the second-order frequency 1604 MHz of the first local oscillator 5 and the fourth-order frequency 2216 MHz of the second local oscillator 10 are frequency-converted to 612 MHz by the first frequency converter 4, and when the C59 channel is received,
The fundamental frequency of the first local oscillator 5 is 1052 MHz and the second
The third-order frequency of 1662 MHz of the local oscillator 11 of
The frequency converter 4 converts the frequency to 610 MHz, and when the C73 channel is received, the first local oscillator 5
2276 MHz and the fundamental frequency 1662 MHz of the second local oscillator 10 are frequency-converted to 614 MHz by the first frequency converter 4, and the fundamental frequency 1162 MH of the first local oscillator 5 is received when the C77 channel is received.
z and the fundamental frequency 554 MHz of the second local oscillator 11 are frequency-converted by the first frequency converter 4 to 608 MHz, which are respectively the first intermediate frequency (612.75 MHz).
It becomes a spurious interference that enters the band.

Further, as shown in (Table 1) (b), the secondary frequency 1 of the first local oscillator 5 is received when 7 channels are received.
604 MHz and the third-order frequency 1 of the second local oscillator 11
The frequency of 662 MHz is converted to 58 MHz by the second frequency converter 10, and the first frequency is received when the C59 channel is received.
The fundamental frequency 1052 MHz of the local oscillator 5 and the secondary frequency 1108 MHz of the second local oscillator 11 are frequency-converted by the second frequency converter 10 to be 56 MHz,
At the time of receiving the C73 channel, the fundamental frequency 2276 MHz of the first local oscillator 5 and the secondary frequency 2216 MHz of the second local oscillator 11 are frequency-converted by the second frequency converter 10 to be 60 MHz. The fundamental frequency 1162 MHz of the local oscillator 5 and the secondary frequency 1108 MHz of the second local oscillator 11 are frequency-converted by the second frequency converter 10 to 54 MHz, which are spurious signals in the second intermediate frequency (58.75 MHz) band. It becomes an obstacle.

Therefore, the bandpass filter 6 outputs 612.
The band of 75 MHz is band-limited, the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary to fourth frequencies of the second local oscillator 11 are attenuated by the trap circuit 7, and the band pass filter 6 and the trap are provided. The circuit 7 attenuates the frequency band of 1 to 2.3 GHz.

As a result, as shown in FIG. 4, the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary and tertiary frequencies of the second local oscillator 11 of 1 to 2.3 GHz are band-pass filtered. 6 and the trap circuit 7 attenuated by 70 dB or more.

The frequency band of the input signal is set to 91.25
˜549.25 MHz, the first intermediate frequency is 612.75
MHz, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator 5 is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator 11 is 671.5 MHz.

[0042]

[Table 2]

As shown in FIG. By changing the frequency having the pole of the trap circuit 7, as shown in (Table 2) (a), C
When 14 channels are received, the fundamental frequency 728 MHz of the first local oscillator 5 and the fundamental frequency 1343 MHz of the second local oscillator 11 are frequency-converted to 615 MHz by the first frequency converter 4, and when the C15 channel is received, the first local oscillator is received. The fundamental frequency 734 MHz of the oscillator 5 and the fundamental frequency 1343 MHz of the second local oscillator 11 are frequency-converted by the first frequency converter 4 to be 609 MHz.
Spurious interference enters the intermediate frequency (612.75 MHz) band. Also, as shown in (Table 2) (b), C1
At the time of receiving four channels, the fundamental frequency of the first local oscillator 5 is 728 MHz and the fundamental frequency of the second local oscillator 11 is 6
The frequency of 71.5 MHz is converted to 56.5 MHz by the second frequency converter 10, and when the C47 channel is received, the secondary frequency of the first local oscillator 5 is 1960 MHz.
And the third-order frequency of the second local oscillator 11, which is 2014.5M
Hz is frequency-converted by the second frequency converter 10, and 54.
5MHz, the second intermediate frequency (58.75MHz)
It becomes a spurious interference that enters the band. Bandpass filter 6 limits the band of 612.75 MHz, and trap circuit 7
With the fundamental frequency of 728 MHz of the first local oscillator 5
The second-order frequency of the local oscillator 5 of 1960 MHz,
The local frequency of the local oscillator 11 of 671.75 MHz and 2
Next and third frequencies 1343MHz, 2014.5MH
It is also possible to attenuate z, attenuate the frequency band of 670 MHz to 2.1 GHz, and attenuate the spurious interference generated in the first frequency converter 4 and the second frequency conversion circuit 10 by 70 dB or more.

(Embodiment 2) Next, a high frequency selection circuit according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a block diagram of the high frequency selection circuit of the second embodiment.

2 is an input filter, 3 is an RF amplifier, 4 is a first frequency converter, 5 is a first local oscillator, and 6 is a first.
A wideband bandpass filter that limits the intermediate frequency signal, 40 is a lowpass filter that attenuates the higher-order frequencies of the first local oscillator and the third and higher frequencies of the second local oscillator, and 41 is the first local oscillator. A trap circuit for attenuating the fundamental frequency and the secondary frequency of the second local oscillator, 8 is a first intermediate frequency amplifier, 9 is a wideband bandpass filter for limiting the first intermediate frequency signal, and 10 is a second frequency converter. , 11 is a second local oscillation circuit, 12 is a second intermediate frequency filter, and 13 is a second intermediate frequency amplifier.

The band pass filter 6, the low pass filter 40, the trap circuit 41, the first intermediate frequency amplifier 8,
If is between the first frequency converter and the second frequency converter, the order of arrangement is random.

The trap circuit 41 may be a low pass filter having poles at the fundamental frequency and the higher frequencies of the first local oscillator.

As an example, the circuit diagram of the bandpass filter 6 constituted by the microstrip line is shown in FIG. 2, and the circuit diagram of the lowpass filter 40 constituted by the microstrip line is shown in FIG. 6, and the trap constituted by the microstrip line is shown. A circuit diagram of the circuit 41 is shown in FIG.
FIG. 8 shows frequency characteristics of the band pass filter 6, the low pass filter 40 of FIG. 6, and the filter in which the trap circuit 41 of FIG. 7 is combined.

In FIG. 6, 43, 44, 46, 47,
49, 50, and 52 are patterns created on the substrate, 4
5, 48 and 51 are capacitors, a pattern 43 is a coil, a pattern 44 is a capacitor grounded in parallel with a capacitor 45, a pattern 46 is a coil, a pattern 47 is a capacitor grounded in parallel with a capacitor 48, and a pattern 49. Is a coil, and the pattern 50 is a capacitor grounded in parallel with the capacitor 51 to form a low-pass filter.

In FIG. 7, reference numerals 55 to 62 are patterns formed on the substrate, and show a resonance circuit in which the coil and the capacitor are grounded by the patterns 55 and 56. Similarly, the patterns 58 and 59 and the patterns 61 and 62 also include the coil and the capacitor. A resonant circuit grounded is shown.

The horizontal axis of FIG. 8 is frequency and the minimum frequency is 1 MHz.
z, the maximum frequency is 3 GHz, the width of one memory is 300 MHz, and the vertical axis is the minimum gain of -90 and maximum gain of 10 dB.
Thus, one memory has 10 dB.

The frequency band of the input signal is 91.25-54.
9.25MHz, the first intermediate frequency is 612.75MH
z, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator 5 is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator 11 is 554 MHz. The spurious interference generated in one intermediate frequency band and generated in the second intermediate frequency band by the second frequency conversion circuit 10 can be calculated by (Equation 1).

As in Example 1, as shown in (Table 1),
In order to prevent spurious interference generated in the first intermediate frequency band by the first frequency converter 4 and generated in the second intermediate frequency band by the second frequency converter 11, 612.75 MHz is set by the bandpass filter 6. The band is limited, the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary to quaternary frequencies of the second local oscillator 11 are attenuated by the trap circuit 41, and the low-pass filter 40 performs the first local frequency. 2 of oscillator 5
The band pass filter 6 and the trap circuit 4 which attenuate the frequencies higher than the second order and the frequencies higher than the third order of the second local oscillator 11 are attenuated.
1 and the low-pass filter 40 attenuate the frequency band of 1 to 2.3 GHz.

As a result, as shown in FIG. 8, the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary and tertiary frequencies of the second local oscillator 11 of 1 to 2.3 GHz are band-pass filtered. 6, the low-pass filter 40 and the trap circuit 41 attenuate 70 dB or more.

Further, the frequency band of the input signal is set to 91.25
˜549.25 MHz, the first intermediate frequency is 612.75
MHz, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator 5 is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator 11 is 671.5 MHz, the frequency having the pole of the trap circuit 41. As shown in (Table 2) in the same manner as in Example 1, the first frequency converter 4 generates in the first intermediate frequency band,
In order to prevent spurious interference generated in the second intermediate frequency band in the second frequency converter 11, the bandpass filter 6 band-limits 612.75 MHz, and the trap circuit 4
1 attenuates the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary to fourth frequencies of the second local oscillator 11, and the low pass filter 40 suppresses the secondary frequency of the first local oscillator 5 and above. , The third and higher frequencies of the second local oscillator 11 are attenuated, and the band pass filter 6 and the trap circuit 41 are attenuated.
The low pass filter 40 attenuates the frequency band of 670 to 2.1 GHz.

(Embodiment 3) Next, a high frequency selection circuit according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 shows a block diagram of the high frequency selection circuit of the second embodiment.

2 is an input filter, 3 is an RF amplifier, 4 is a first frequency converter, 5 is a first local oscillator, and 6 is a first
A wideband bandpass filter that limits the intermediate frequency signal, 7 is a trap circuit that attenuates the fundamental frequency and higher frequencies of the first local oscillator, 64 is a highpass filter that attenuates the fundamental frequency of the second local oscillator, and 8 is A first intermediate frequency amplifier, 9 is a wideband bandpass filter for limiting the first intermediate frequency signal, 10 is a second frequency converter, 11 is a second local oscillator circuit, 12 is a second intermediate frequency filter, 1
3 is a second intermediate frequency amplifier.

If the band pass filter 6, the trap circuit 7, the high pass filter 64, and the first intermediate frequency amplifier 8 are located between the first frequency converter 4 and the second frequency converter 10, the order of arrangement is random. Is.

The trap circuit 7 is composed of the first local oscillator 5
May be a low pass filter having poles at the fundamental frequency and higher frequencies, and the high pass filter 64 may be a trap circuit that attenuates the fundamental frequency of the second local oscillator 11.

As an example, the circuit diagram of the bandpass filter 6 constituted by the microstrip line is shown in FIG. 2, and the circuit diagram of the trap circuit 7 constituted by the microstrip line is shown in FIG. 3 and constituted by the microstrip line. FIG. 10 shows a circuit diagram of the high pass filter 64, and FIG. 11 shows frequency characteristics of a filter in which the band pass filter 6, the trap circuit 7 of FIG. 3 and the high pass filter 64 of FIG. 10 are combined.

In FIG. 10, 65, 67, 68, 7
1, 72, 75, 78, 80, 82, 84 are patterns formed on the substrate, and 66, 69, 70, 73, 74, 7
Reference numerals 6, 77, 79, and 81 are capacitors, and the patterns serve as coils to form a high-pass filter.

The horizontal axis of FIG. 11 is frequency and the minimum frequency is 1 MHz.
z, the maximum frequency is 3 GHz, the width of one memory is 300 MHz, and the vertical axis is the minimum gain of -90 and maximum gain of 10 dB.
Thus, one memory has 10 dB.

The frequency band of the input signal is 91.25-54.
9.25MHz, the first intermediate frequency is 612.75MH
z, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator 11 is 554 MHz,
In the first frequency conversion circuit 4, the first intermediate frequency band (612.
The spurious interference generated in the 75 MHz band is (Equation 1)
Can be calculated by

Similar to Example 1, as shown in (Table 1),
In order to prevent spurious interference generated in the first intermediate frequency band by the first frequency converter 5 and generated in the second intermediate frequency band by the second frequency converter 11, 612.75 MHz is set by the bandpass filter 6 The band is limited, and the trap circuit 7 attenuates the fundamental frequency and the secondary frequency of the first local oscillator 5 and the secondary to quaternary frequencies of the second local oscillator 11. In addition, by attenuating the fundamental frequency 554 MHz of the second local oscillator 5 with a high pass filter,
As shown in (Table 1) (a), when the C77 channel is received, the fundamental frequency of the first local oscillator 11 is 1162 MHz.
And spurious interference 608 MHz generated at the fundamental frequency 554 MHz of the second local oscillator 5 is suppressed.

As a result, as shown in FIG. 12, the bandpass filter 6 and the trap circuit 7 attenuate the first to 1.6 GHz of the second to third frequencies of the second local oscillator 11 by 70 dB or more, and the second local oscillator 554 MHz of the fundamental frequency of the oscillator 11
The high-pass filter 64 attenuates z by 40 dB.

(Fourth Embodiment) Next, a high frequency selection circuit according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 shows a block diagram of the high frequency selection circuit of the fourth embodiment.

2 is an input filter, 3 is an RF amplifier, 4 is a first frequency converter, 5 is a first local oscillator, and 6 is a first local oscillator.
A wideband bandpass filter that limits the intermediate frequency signal, 40 is a lowpass filter that attenuates the third and higher frequencies of the second local oscillator, 41 is a trap circuit that attenuates the second frequency of the second local oscillator, and 64 is A high pass filter for attenuating the fundamental frequency of the second local oscillator, 8 a first intermediate frequency amplifier, 9 a wide band pass filter for limiting the first intermediate frequency signal, 10 a second frequency converter, 1
Reference numeral 1 is a second local oscillation circuit, 12 is a second intermediate frequency filter, and 13 is a second intermediate frequency amplifier.

The band pass filter 6, the low pass filter 40, the trap circuit 41, the high pass filter 64,
If the first intermediate frequency amplifier 8 is provided between the first frequency converter and the second frequency converter, the order of arranging the first intermediate frequency amplifier 8 is in no particular order.

The trap circuit 41 may be a low-pass filter having poles at the fundamental frequency of the first local oscillator 5 and higher frequencies, and the high-pass filter 64 may be a trap circuit that attenuates the fundamental frequency of the second local oscillator 11. good.

As an example, the circuit diagram of the bandpass filter 6 constituted by the microstrip line is shown in FIG. 2, and the circuit diagram of the lowpass filter 40 constituted by the microstrip line is shown in FIG. 6 and constituted by the microstrip line. A circuit diagram of the trap circuit 41 shown in FIG. 7 is shown, a circuit diagram of the high pass filter 64 constituted by a microstrip line is shown in FIG. 10, and the band pass filter 6 of FIG. 2, the low pass filter 40 of FIG. 6, and the trap of FIG. FIG. 13 shows frequency characteristics of a filter in which the circuit 41 and the high-pass filter 64 of FIG. 10 are combined.

The horizontal axis of FIG. 13 is frequency and the minimum frequency is 1 MHz.
z, the maximum frequency is 3 GHz, the width of one memory is 300 Mhz, and the vertical axis is the minimum gain of -90 and maximum gain of 10 dB.
Thus, one memory has 10 dB.

The frequency band of the input signal is 91.25-54.
9.25MHz, the first intermediate frequency is 612.75MH
z, the second intermediate frequency is 58.75 MHz, the fundamental frequency of the first local oscillator 5 is 704 to 1162 MHz, and the fundamental frequency of the second local oscillator is 554 M band Hz,
In the first frequency conversion circuit 4, the first intermediate frequency band (612.
The spurious interference generated at 75 MHz can be calculated by the equation (1).

Similar to the first and third embodiments, as shown in (Table 1), the first frequency converter 4 generates the first intermediate frequency band, and the second frequency converter 10 generates the second frequency band. In order to prevent spurious interference that occurs in the intermediate frequency band of the bandpass filter, the bandpass filter 6 limits the band to 612.75 MHz, and the trap circuit sets the fundamental frequency and the secondary frequency of the first local oscillator 5 to the second local oscillator. The second to fourth frequencies of 11 are attenuated, and the fundamental frequency of 554 MHz of the second local oscillator 11 is attenuated by the high pass filter.

As a result, as shown in FIG. 11, the second to third order frequencies of the second local oscillator 11 are 1.1 to 1.66 G.
The bandpass filter 6, the trap circuit 41, and the lowpass filter 40 attenuate Hz at 70 dB or more, and the basic frequency 554 MHz of the second local oscillator 11 is attenuated by the highpass filter 64 by 40 dB.

[0075]

According to the high frequency selection circuit of the present invention, the first
A first frequency converter for unadjusting a filter for attenuating the fundamental frequency and higher frequencies of the first local oscillator and the second local oscillator between the frequency converter and the second frequency converter. A wideband bandpass filter for band-limiting the first intermediate frequency signal between the converter and the second frequency converter, and further, the fundamental frequency and higher-order frequencies of the first local oscillator and the second local oscillator. And a low-pass filter for attenuating high-order frequencies of the first and second local oscillators are combined with a wideband bandpass filter for band-limiting the first intermediate frequency signal. Due to the fundamental and higher frequencies of the first and second local oscillators, spurious generated in the first local oscillator and the second frequency converter and within the band of the first intermediate frequency signal and the second intermediate frequency signal. A trap that suppresses harm and attenuates higher-order frequencies of the second local oscillator when the second intermediate frequency is lower than the first intermediate frequency and the fundamental frequency of the second local oscillator is set lower than the first intermediate frequency. A circuit, a low-pass filter for attenuating higher-order frequencies of the second local oscillator, and a high-pass filter for attenuating the fundamental frequency of the second local oscillator as a wideband band-pass filter for band limiting the first intermediate frequency signal. The combination of the first and second local oscillators causes the first frequency converter to generate the first intermediate frequency with the fundamental frequency and the higher order frequencies of the first local oscillator and the fundamental frequency and the higher order frequencies of the second local oscillator. It suppresses spurious interference that falls within the band of the signal.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a high frequency selection circuit according to an embodiment of the first invention.

FIG. 2 is a circuit diagram of a bandpass filter using a microstrip line in an embodiment of the high frequency selection circuit.

FIG. 3 is a circuit diagram of a trap circuit using a microstrip line of the same high frequency selection circuit.

FIG. 4 is a frequency characteristic diagram of a filter in which a bandpass filter and a trap circuit of the same high frequency selection circuit are combined.

FIG. 5 is a configuration diagram of a high frequency selection circuit according to an embodiment of the second invention.

FIG. 6 is a circuit diagram of a low-pass filter using a microstrip line of the same high frequency selection circuit.

FIG. 7 is a circuit diagram of a trap circuit using a microstrip line in an embodiment of the high frequency selection circuit.

FIG. 8 is a frequency characteristic diagram of a filter in which a bandpass filter, a trap circuit, and a lowpass filter are combined in an embodiment of the high-frequency selection circuit.

FIG. 9 is a configuration diagram of a high frequency selection circuit according to an embodiment of the third invention.

FIG. 10 is a diagram showing a high-pass filter using a microstrip line in an example of the high-frequency selection circuit.

FIG. 11 is a frequency characteristic diagram of a filter in which a bandpass filter, a trap circuit, and a highpass filter are combined in one embodiment of the high-frequency selection circuit.

FIG. 12 is a configuration diagram of a high frequency selection circuit according to an embodiment of the fourth invention.

FIG. 13 is a diagram showing frequency characteristics of a filter in which a bandpass filter, a trap circuit, a lowpass filter, and a highpass filter are combined in an embodiment of the high-frequency selection circuit.

FIG. 14 is a configuration diagram of a conventional high frequency selection circuit.

FIG. 15 is a circuit diagram of a bandpass filter, a first intermediate frequency amplifier circuit, and a bandpass filter of a conventional high frequency selection circuit.

FIG. 16 is a frequency characteristic diagram of a bandpass filter of a conventional high frequency selection circuit.

[Explanation of symbols]

1 Input 2 Input Filter 3 RF Amplifier 4 1st Frequency Converter 5 1st Local Oscillator 6 Bandpass Filter 7, 41 Trap Circuit 8 1st Intermediate Frequency Amplifier 9 Bandpass Filter 10 2nd Frequency Converter 11 2nd Local oscillator 12 second intermediate frequency filter 13 second intermediate frequency amplifier 14 intermediate frequency output 15-18, 21, 25-38, 43, 44, 46, 4
7, 49, 50, 52, 55-62, 65, 67, 6
8, 71, 72, 75, 78, 80, 82, 84 patterns 19, 20, 45, 48, 50, 66, 69, 70, 7
2, 74, 76, 77, 79, 81, 90, 91, 9
2, 93, 97, 98, 101, 104, 106, 10
7, 108 Capacitor 22 Bandpass filter input 23 Bandpass filter output 24, 54 Trap circuit input 39, 63 Trap circuit output 40 Lowpass filter 42 Lowpass filter input 53 Lowpass filter output 64 Highpass filter 83 Highpass filter output 85 Highpass filter input 86, 87 band pass filter 88, 89, 109, 110, 111 metal plate 94, 96, 99 resistance 95 transistor 102, 116 coil 112 band pass filter output 113 ground 114 feedthrough capacitor 115 band pass filter input

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takaaki Konishi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A first frequency converter that frequency-converts an input signal into a first intermediate frequency signal, a first local oscillator that generates an oscillation signal that is input to the first intermediate frequency converter, and the first frequency converter. A filter comprising a bandpass filter and a trap circuit for inputting the output signal of the first frequency converter and limiting the band; a second frequency converter for inputting the output signal of the filter and converting the frequency to a second intermediate frequency; A second local oscillator for generating an oscillating signal to be input to the second frequency converter, and a fundamental frequency of the first local oscillator or a higher-order frequency signal thereof and a fundamental frequency of the second local oscillator, or A second frequency signal when the higher-order frequency signal is frequency-converted by the first frequency converter and falls within the first intermediate frequency signal band
The trap circuit has a pole at the fundamental frequency of the local oscillation signal or at a higher frequency thereof, and the fundamental frequency of the first local oscillator or a higher frequency signal thereof and the fundamental frequency of the second local oscillator or The higher frequency signal
The trap circuit has a pole at a fundamental frequency or a higher frequency of the first local oscillation signal when the frequency is converted by the second frequency converter and enters the second intermediate frequency signal band. High frequency selection circuit. 2. A first frequency converter that frequency-converts an input signal into a first intermediate frequency signal, a first local oscillator that generates an oscillation signal that is input to the first intermediate frequency converter, and the first frequency converter. A filter including a bandpass filter for inputting the output signal of the frequency converter 1 and band limiting, a trap circuit, and a lowpass filter, and a second frequency converter for inputting the output signal of the filter and performing frequency conversion to a second intermediate frequency. And a second local oscillator that generates an oscillating signal to be input to the second frequency converter, the fundamental frequency of the first local oscillator or a higher-order frequency signal thereof, and the second local oscillator. A second frequency when the fundamental frequency or a higher-order frequency signal is frequency-converted by the first frequency converter and falls within the first intermediate frequency signal band.
The trap circuit has a pole at the fundamental frequency of the local oscillation signal or its higher order frequency, and the higher order frequency of the second local oscillation signal is attenuated by the low-pass filter.
Of the fundamental frequency of the local oscillator or a higher frequency signal thereof and the fundamental frequency of the second local oscillator or a higher frequency signal thereof are frequency-converted by the second frequency converter to generate a second intermediate frequency signal band. The trap circuit has a pole at the fundamental frequency of the first local oscillation signal or its higher frequencies when entering the inside, and the high-order frequency of the second local oscillation signal is attenuated by the low-pass filter. Characteristic high frequency selection circuit. 3. A first frequency converter that frequency-converts an input signal into a first intermediate frequency signal, a first local oscillator that generates an oscillation signal to be input to the first intermediate frequency converter, and the first frequency converter. No. 1 frequency converter inputs a band-pass filter for limiting the band and a filter including a trap circuit and a high-pass filter, and a second frequency converter for inputting the output signal of the filter and performing frequency conversion to a second intermediate frequency. And a second local oscillator that generates an oscillation signal to be input to the second frequency converter, wherein the second intermediate frequency is lower than the first intermediate frequency, and a fundamental frequency of the second local oscillator. Is set to be lower than the first intermediate frequency, the fundamental frequency or higher order frequency of the first local oscillator and the second frequency
Of the local frequency of the second local oscillator signal when the fundamental frequency or higher order frequency of the local oscillator is frequency-converted by the first frequency converter and falls within the first intermediate frequency signal band. The circuit has a pole, the fundamental frequency of the second local oscillator signal is attenuated by the high-pass filter, the fundamental frequency of the first local oscillator or its higher order frequency signal and the fundamental frequency of the second local oscillator. Alternatively, the high-order frequency signal is frequency-converted by the second frequency converter, and the trap is set to the fundamental frequency of the first local oscillation signal or the high-order frequency thereof when entering the second intermediate frequency signal band. A high frequency selection circuit characterized in that the circuit has poles. 4. A first frequency converter that frequency-converts an input signal into a first intermediate frequency signal, a first local oscillator that generates an oscillation signal that is input to the first intermediate frequency converter, and the first frequency converter. A filter including a bandpass filter, a trap circuit, a highpass filter and a lowpass filter for inputting an output signal of the first frequency converter and limiting the band; and a second frequency conversion circuit for inputting the output signal of the filter to a second intermediate frequency. A frequency converter and a second local oscillator that generates an oscillating signal to be input to the second frequency converter, wherein the second intermediate frequency is lower than the first intermediate frequency, and the second local oscillator Is set to be lower than the first intermediate frequency, the fundamental frequency or higher order frequency of the first local oscillator and the second frequency
Of the local frequency of the second local oscillator signal when the fundamental frequency or higher order frequency of the local oscillator is frequency-converted by the first frequency converter and falls within the first intermediate frequency signal band. The circuit has a pole, the fundamental frequency of the second local oscillation signal is attenuated by the high pass filter, the higher order frequency of the second local oscillation signal is attenuated by the low pass filter, and the fundamental frequency of the second local oscillation signal is attenuated by the low pass filter. When the fundamental frequency or its higher-order frequency signal and the fundamental frequency of the second local oscillator or its higher-order frequency signal are frequency-converted by the second frequency converter and fall within the second intermediate frequency signal band. The trap circuit has a pole at the fundamental frequency of the first local oscillation signal or at a higher frequency thereof, and the high frequency of the first local oscillation signal is attenuated by the low-pass filter. Frequency selection circuit.